new zealand’s energyscape - niwa · ener gysc a pe december 2008 energyscape asset review...

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EnergyScape™ Basis Review June 2009

New Zealand’s EnergyScape™

Section 2 Renewable Resources

© All rights reserved. This publication may not be reproduced or copied in any form without the permission of the client. Such permission is to be given only in accordance with the terms of the client's contract with NIWA. This copyright extends to all forms of copying and any storage of material in any kind of information retrieval system.

EnergyScape™ Basis Review Authors

Rilke de Vos, NIWA Stefan Fortuin, NIWA Sylvia Nichol, NIWA Peter Franz, NIWA Dennis Jamieson, NIWA Murray Smith, NIWA Craig Stevens, NIWA

Prepared for

Foundation for Research, Science & Technology (FRST)

Project:

NZES091- New Zealand’s EnergyScape

Document number:

AKL-2009-034 (2)

Publisher:

NIWA, Auckland June 2009

Reviewed: Approved:

Georgina Griffiths Senior Climate Scientist

Ken Becker Regional Manager - Auckland

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Section 1 End-use

TABLE OF CONTENTS

Summary v

2. Renewable resources 3 2.1 Solar resources 7

2.1.1 General introduction 7 2.1.2 Introduction to the resource 12 2.1.3 Resource uncertainty 18 2.1.4 Barriers and limitations 19 2.1.5 Introduction to conversion technologies 21 2.1.6 Asset characterisation 31 2.1.7 Research status 33 2.1.8 Summary 35

2.2 Wind resources 37 2.2.1 General introduction 37 2.2.2 Introduction to the resource 41 2.2.3 Resource uncertainty 44 2.2.4 Barriers and limitations 44 2.2.5 Introduction to conversion technologies 48 2.2.6 Asset characterisation 53 2.2.7 Research status 54 2.2.8 Summary 54

2.3 Hydro resources 56 2.3.1 General introduction 56 2.3.2 Introduction to the resource 58 2.3.3 Resource uncertainty 61 2.3.4 Barriers and limitations 61 2.3.5 Introduction to conversion technologies 65 2.3.6 Asset characterisation 66 2.3.7 Research status 68 2.3.8 Summary 69

2.4 Marine (Wave) resources 71 2.4.1 General introduction 71 2.4.2 Introduction to the resource 74 2.4.3 Resource uncertainty 81 2.4.4 Barriers and limitations 83 2.4.5 Introduction to conversion technologies 86 2.4.6 Asset characterisation 90 2.4.7 Research status 91 2.4.8 Summary 94

2.5 Marine (Tidal) resources 96 2.5.1 General introduction 96 2.5.2 Introduction to the resource 98 2.5.3 Resource uncertainty 103 2.5.4 Barriers and limitations 106 2.5.5 Introduction to conversion technologies 111 2.5.6 Asset characterisation 113 2.5.7 Future research 118 2.5.8 Summary 120

References 122

Appendix A – List of marine (tidal) technologies 127

Glossary of common terms 130

New Zealand’s EnergyScape Basis Review Section 2 v

SUMMARY The EnergyScape project is a collaborative research initiative that seeks to develop tools that can support energy policy development by considering the impact of integrated solutions for the long-term time horizon, at a regional level on a broad range of social parameters. To achieve this aim, the project has developed a series of linked tools (the EnergyScape framework) which can unify economic data, energy data, system assumptions and facilitate improved understanding of the complexities and dependencies of: resource depletion, energy substitution, transmission costs, conversion efficiencies, locality effects, scale, demand controls, environmental impact (on land, water and the atmosphere) and risk.

The linkages between some of the key deliverables of the project are illustrated below:

EnergySc a p e Projec t Overview

New Zea land ’ s EnergySc ap e

De cemb er 2008

Ene rg y Resea rc h Stra te gy

New Zea land ’ s EnergyScape

De ce mb e r 2008

EnergySc a pe Asset Review

New Zealand ’s EnergyScap e

De cemb er 2008

Ene rg ySca pe Projec t Overview

New Zea land ’ s EnergySc ape

De ce mb er 2008

LEAP model

Energy AssetDatabase

Energy Demand

Database

Mapping of 'primary' energy pathwaysEnd- use options

Sour ce Examples Pre paratio n Pr im ary distr ib ution Primary co nversion Primary co nversion su pport Secondar y distribut io n T ertiary appliance Exp

ort

Non

-ene

rgy

Low

gra

de h

eat

Hig

h gr

ade

heat

Ele

ctric

al

Mob

ility

Mac

hani

cal

L

L H

L

T M

X N

X N

L H

L

L H

L

H E

L

L

Elec tricity network / Grid

T hermovoltaics ( STV)[Stirling generator]

High temperature ther mal (SHT)[Solar tower; Solar concentrating

boiler]

Low temper ature thermal (SLT)[P late; Evacuated tube;

Thermosyphon; pumped]

Hydratic System

Photo- ox idation (S PO)[Photo bioreactor] Clean & compress

Regional gas ification National gas grid

Switchgear

Pass ive solarW indows, Insulation,

Ther mal mass

Photovoltaic (S PV)[Thin fi lm, O rganic , S il icon]

Standalone Electric ity Local or Off-G rid

Steam generator

Solar thermal s torage tank


Building

Industr ial heat plant

Low temp (eg. Water) heatersIndustrial pre-heat


Onshor e w ind tur bines (WO N)

O ffshore wind turbines (WO F)

Local wind turbines (WLT)

Mechanical w ind drive (WMD)[W ind dam, irrigation channel,

Maise gr inding]




C ommercial and large scale hydro (HLS)

[Run of river; Modulated r un of river; Tunelled hydro]

Distributed and community scale hydro (H SS)

[Mini & micro hydro]

Commerc ial scale tidalBarrage (MTB)Flapper (MTF)Tur bine (MTT)




Commerc ial scale wavePoint absorber (MWA)

Osc ial lating C olumn (MW O)Pelarmis (MWP)


C ommerc ial scale ocean thermal (MO T)Thermal

Tidal current

W ave

Elec tricity network / GridSwitchgear

P urpose grown woody biomass

[Whole fores ts (FWF) ;Short r otation forestry

(SRF)]

Truck ing

H ar vest / C hip / D ry

P yrolys is

Biological trans formation

C ogen (inc luding dry ing)

Elec tricity generation

C rude oi l distribution

O xygenate dis tribution E

Local heat network

Elec tricity network / G rid



D is tributed woody biomass

[Harvest res idue (BPG2);Wood process ing residue

(FRW) ;Sawdust processing

res idue (FR S); G reenwaste (MG W);

Construc tion / Demolition W aste (MC W);

Biosolids from sewage treatment (MBW)

Munipal solid waste - Biosolids (MSW); O ther

Waste e.g. P aper (MOP) ; D airy manure (AMD) - Concentrated; Pruning

R esidies (HPR ); P rocessing P ulp Res idues ( HPP)]

Truck ing

Res idential CHP

Local heat network


National H2 network

Local H2 network

C ogen (inc luding dry ing) Elec tricity network / G rid

Mechanical dev ice (e.g. Pump, Compressed air )

Timber Paper (export)

Low grade heat applications

Waste & Non-ener gy

Industrial / DomesticCombustion (e.g. direc t heat, steam

rais ing, wood drying)

Industrial / Domesticheat plant

R es idential heat plant

Sol

arW

ind

Hyd

roM

arin

eB

iom

ass

Munic ipal Solid Waste G as turbine / ICE Elec tricity network / G rid

Stor

age h

ydro

(pum

ped h

ydro)

CWDPYRCRUDE

CWDENZ

Stor

age h

ydro

(pum

ped h

ydro

)

Chip, dry & pellet R oad transport Low grade heat applications

Disti l lation CW DET H

Electric ity netw or k / Gr id

Landfi l l gas recovery

O xygenate dis tribution E

G as turbine / ICE Elec tricity network / G ridMSW gasificationHigh Temp. Flash

MSW bio-fermentation

Landfi l l burial & cover

Pulp & Paper plant Paper (export)

Industrial / DomesticCombustion (e.g. direc t heat, steam

rais ing, wood drying)

Residential Combustion

Demand by fuel

0

100

200

300

400

500

600

700

800

2000

2005

2015

2030

2050

Year

Vario

us

Avfuel

Biodiesel

Biogas

Black Liquour

CNG

Coal Lignite

Coal SubBituminousCoal Unspecified

Crude Oil

Diesel

Electricity

Export LightFuelsExported CrudeOilFertilizer

Fuel Oil

Geothermal

Geothermal LT

G th l LT

Continuity Scenario

0

1 0 0

2 0 0

3 0 0

4 0 0

5 0 0

6 0 0

7 0 0

8 0 0

2000

2005

2015

2030

2050

Year

Political Scenario

0

1 0 ,0 0 0

2 0 ,0 0 0

3 0 ,0 0 0

4 0 ,0 0 0

5 0 ,0 0 0

6 0 ,0 0 0

7 0 ,0 0 0

2000

2005

2015

2030

2050

Year

Alternative Scenario

Solar: 0.23 PJ Local generation / d ist ribution

Wind: 2.22 PJ

Marine: 0.0001 PJ

Hydro: 84.5 PJElect ric ty generation

Geothermal: 81 PJ

Biomass (waste water): 1.3 PJ

Elect ric ty generation

Indigenous gas: 134 PJ

Biomass (whole fores t): 33.4 PJ

7.08 PJ

19.9 P J

2.22 PJ

65.4 PJ

Fert iliser: 5.71 P J

Coal export: 70.6 PJ

3.86 PJ

5.71 P J

6 PJ

Electrict y generation

6 P J

Pyro lysis

0.3 PJ

5.9 PJ

0.893 PJ 0.33 PJ

Indi genous oil production: 44 1 PJ

Indigenous coal: 133 PJ

0.23 PJ

Petrochemicals

Gas to Liquids

LNG Import : 0.001 PJ

Methand hydrate: 0.001 PJ

18.1 PJ

5.86 P J 4.65 PJ6.67 PJ 26.7 P J

49.7 PJElect ric ty generation

Coal import : 23.4 P J

50 PJ0.1 P J 3.15 PJ

0.001 P J

17 PJ

0.001 P J

Electricty generation

Gasification Coal to Liquids

2.29 P JCogeneration

20.9 PJ

Cogenerat ion6.9 P J

Oil products im port: 83.6 P J

Crude oil export: 28 PJ

Domest ic transport: 194 PJ

Coal to non-energy: 17.1 PJ

Oil products export: 7.04 PJ

4.86 PJ

Petroleum refin ingCrude oil import: 203 PJ

Oil products distribution

Losses & own use

International transport: 19.3 PJ

12.8 P J11 P J2.5 P J

0.5 PJ 14.4 PJ

12.4 PJ

Biomass export: 0.001 PJ

19.3 PJ

Elect ric ty generation Nationa l grid

52.1 PJ

46.5 PJ

Indust rial: 178 PJ

A gricult ural: 21.4 PJ

Commerc ial: 57 PJ

Resident ial: 64 PJ

26.2 PJ

The “EnergyScape Project Overview” report provides the foundation for the research effort, by outlining the scope, purpose and methodology that would be utilised by the research project. The “EnergyScape Basis Review” documents the status of energy infrastructure and flows for all energy pathways in New Zealand. Data pertaining to the pathways described in the “Basis Review” were captured in an “Energy Asset Database” and an “Energy Demand Database”. These databases provide input to Long Range Energy Alternatives Planning (LEAP) models and subsequent analysis tools.

New Zealand’s EnergyScape Basis Review Section 2 vi

This “EnergyScape Basis Review” is intended to provide a broad introduction1 to New Zealand’s energy infrastructure. The seven (7) sections of the report cover the full spectrum of the energy system from resources, through generation, distribution, conversion and end-use:

Section 1 – Energy end-use

Section 2 – Renewable resources

Section 3 – Bioenergy resources

Section 4 – Earth resources

Section 5 – Distribution infrastructure

Section 6 – Secondary conversion

Section 7 – Hydrogen options

All energy sectors (e.g. industrial end-use, wind power, coal to liquids) are given separate chapters in the relevant section. Each chapter has been written so that if the reader only has interest for one particular area, an appreciation for how that area contributes to New Zealand’s energy portfolio, now and in future can be gained by reading that section in isolation. In addition to describing the current status of public domain knowledge pertaining to energy resources, each chapter also deals with the efficiencies, risks and research applicable to this energy sector. These chapters provide the philosophy for populating the New Zealand energy asset and end-use databases.

Section 2 reviews the latest efforts to quantify our renewable resources, and the technologies that support them. Although the scope of the EnergyScape project was only to undertake literature reviews in this area, new research was undertaken to supplement existing literature wherever appropriate. Each resource sub-section concludes with some commentary regarding the expected future development of these resources and detail pertaining to assumptions used to add resource data to the framework. Significant conclusions drawn from this section include:

• The relative energy cost of fossil fuels (low capital expenditure, moderate operating expenditure) is escalating rapidly, to such an extent that prudent investment in renewable fuels (moderate capital expenditure, low operating expenditure) is likely to have economic benefit.

• Significant national carbon intensity reductions will require the use of renewable energy for the provision of process heat and mobility.

• New Zealand is well endowed in resources that can be harnessed almost indefinitely (i.e. renewable) – expansive hydro resources, world class wind resources, bounteous

1 Capable of being read by the interested public i.e. those with some familiarity with energy system concepts.

New Zealand consumers’ annual spend on petroleum and electricity is roughly $2,450 and $3,360 per household respectively (4.9% and 6.8% of total consumer spend). The costs of both energy sources are increasing much faster than inflation.

New Zealand’s EnergyScape Basis Review Section 2 vii

geothermal resources (addressed in Section 4), significant tidal resources, powerful wave resources, abundant agricultural co-products and massive woody biomass plantations (addressed in Section 3).

• Harnessing solar resources is the field with the most opportunity to result in a paradigm shift in energy utilisation. Passive solar and direct solar heating (e.g. solar hot water heating) are currently cost effective. Other technologies such as solar concentrating boilers, organic / thin film and silicon based photovoltaic cells are increasingly competitive in some specific applications with a possibility to become attractive for mainstream applications well before 2050.

• Wind generation is evolving from a very limited starting base (currently less than 2.5% of electricity generation).

• Hydro generation capacity has stagnated, but significant generation potential (1,550 – 4,900 MW) remains unexploited.

• New Zealand’s wave energy resources are significantly greater than tidal resources, but tidal resources may be more accessible in the short term. The technology required to harness these resources is still immature but is evolving rapidly.

• There are many myths associated with the variability / intermittency of renewable resources. The implications of variability and intermittency are often overstated owing to a lack of analytical review to assess the impact.

Section 2 RENEWABLE RESOURCES - Resources that flow perpetually

Section 2 Renewable resources

New Zealand’s EnergyScape Basis Review Section 2 2

2 – RENEWABLE RESOURCES Primary Conversion Pathway Overview

Mapping of 'primary' energy pathways

Source Examples Preparation Primary distribution Primary conversion Primary conversion support Secondary distribution Tertiary appliance

Electricity network / Grid

Thermovoltaics (STV)[Stirling generator]

High temperature thermal (SHT)[Solar tower; Solar concentrating

boiler]

Low temperature thermal (SLT)[Plate; Evacuated tube;


Hydratic System

Photo-oxidation (SPO)[Photo bioreactor] Clean & compress

Switchgear

Passive solar Windows, Insulation, Thermal mass

Photovoltaic (SPV)[Thin film, Organic, Silicon]

Standalone Electricity Local or Off-Grid

Steam generator

Solar thermal storage tank


Building

Industrial heat plant



Onshore wind turbines (WON)

Offshore wind turbines (WOF)


Mechanical wind drive (WMD)[Wind dam, irrigation channel,

Maise grinding]




Commercial and large scale hydro (HLS)

[Run of river; Modulated run of river; Tunelled hydro]

Distributed and community scale hydro (HSS)


Commercial scale tidalBarrage (MTB)Flapper (MTF)Turbine (MTT)




Commercial scale wavePoint absorber (MWA)

Osciallating Column (MWO)Pelarmis (MWP)


Commercial scale ocean thermal (MOT)Thermal

Tidal current

Wave

Electricity network / GridSwitchgear


National H2 network

Local H2 network

Mechanical device (e.g. Pump, Compressed air)

Sola

rW

ind

Hyd

roM

arin

e

Stor

age

hydr

o(p

umpe

d hy

dro)St

orag

e hy

dro

(pum

ped

hydr

o)

SYSTEM IDENTIFIERS TECHNOLOGY STATUS LABEL CODES

HTM High Temp MediumLTM Low Temp MediumSTM SteamELEC Electrical (Local)EXP ExportIMP ImportIND IndigenousNGC Compressed natural gasH2 Hydrogen

ETH EthanolOXY Oxygenate

Distribution systems are "assets"

LEG

END

NATIONAL ELECTRICITY GRID

NATIONAL NATURAL GAS GRID

LIGHT LIQUID FUEL DISTRIBUTION [L] - LPG [P] - Propane [B] - Butane [O] - Butanol

ENERGY STORAGE IS SUPPLIED

CONVENTIONAL LIQUID FUEL DISTRIBUTION [K] - Kerosine [P] - Petrol [D] - Diesel [B] - Fuel oil / Bunkers

NATIONAL HYDROGEN GAS GRID

LOCAL ELECTRICITY GRID

LOCAL NATURAL GAS GRID

LOCAL HYDROGEN GAS GRID

OXYGENATE DISTRIBUTION [D] -DME [E] - Ethanol [M] - MTBE

CRUDE OIL DISTRIBUTION

SEQUESTRATION IS POSSIBLE

XXX

XXX

XXX Fair knowledge

Could improve understanding

Knowledge gap exists


2 – RENEWABLE RESOURCES Introduction

2. RENEWABLE RESOURCES In this section we review New Zealand’s endowment of renewable resources and the status of technology that can be used to harness these resources.

“Renewable energy is derived from natural processes that are replenished constantly. In its various forms, it derives directly from the sun, or from heat generated deep within the earth. Included in the definition is electricity and heat generated from solar, wind, ocean, hydropower, biomass, geothermal resources, and biofuels and hydrogen derived from renewable resources”

Source: IEA, 2008. p.39

Traditionally, the lower energy density of most renewable energy sources has made the development of these resources less cost effective than fossil fuel resources. Worldwide, the scene is changing for three main reasons, namely:

First, most countries consume much more energy than they generate, in particular fossil fuels. There is a threat that, because these energy reserves are finite and, as these reserves deplete, the cost of worldwide supply will increase to a level that makes import dependent countries less economically competitive. By switching to local renewable energy resources, countries become less dependent on energy imports.

Second, when fossil fuels are used to generate energy, they release greenhouse gases, which are increasingly attracting a carbon charge. By switching to renewable energy, countries minimise carbon price exposure and, simultaneously, help reduce their impact on the global climate.

Third, most reserves of fossil fuel are situated in regions which are not politically stable. The potential interruption to supply can either significantly increase energy costs or cause energy shortages affecting the economy in both cases. Reduced dependence on fossil fuels decreases this exposure.

New Zealand is generally considered to be well endowed with renewable energy resources on a per capita basis. This view typically derives from the perspective of electricity generation, but when considered against total energy demand, including transport fuels, our renewable resources do not seem as abundant. Developing a competitive economy based on a high fraction of renewable energy requires significant research to better understand and overcome the hurdles of market effectiveness, intermittency and demand-supply matching, among others.

Most of the renewable energy sources considered in this section were first harnessed into mechanical power directly at their source e.g. windmills for grinding grain and pumping water, hydro turbines for sawing lumber. The development of generators, motors and electricity revolutionised how we capture, transmit and use energy. No longer are we constrained to using

There are three major reasons why more countries are developing renewable energy resources:

• Improving their trade balance by reducing dependence on fossil fuel imports

• Reducing carbon emissions and Kyoto compliance costs • Increasing control over security of supply



energy at its source – now energy captured at one end of the country can be transmitted and used at the other!

With increased interconnectedness and dependence comes additional security costs and planning. In the case of our electricity system, energy demand and supply must be balanced. Demand profiles mostly follow daily and seasonal trends. Renewable energy supplies naturally vary with environmental factors (i.e. weather patterns).

The two terms that define the nature of the output of renewable energy supplies are:

Variability – Indicating the variations in magnitude of output over long timeframes (i.e. annual or seasonal)

Intermittency – Indicating the variations in magnitude of output over short timeframe (i.e. hours, minutes, seconds)

When considering the potential of renewable energy, the capacity is considered in context of the variability of supply, the total capacity of the system (i.e. electricity network assets) and the network’s capacity to adjust to these fluctuations, e.g. store supplies or defer demand.

These systems can be optimised with increased knowledge and understanding of the energy supply variations, increased capacity of the energy system to absorb these (i.e. its technological capabilities) and improved energy system foresight, coordination and planning.

The scale of individual renewable energy capture systems is, generally, significantly smaller than fossil fuel system (e.g. 0.5-10 MW for a wind farm, in comparison to 30 – 400 MW for a coal-fired power station), the exception is obviously large hydro-dams. Smaller individual units require relatively more management, maintenance etc. per unit of energy generated, and thus suffer from a lack of economy of scale. Smaller units, some closer to or in urban developments or in landscapes with significant beauty, also increase public concerns. The shift from ‘stock’ resources (fossil fuels) to ‘flow’ resources (renewables) also includes a shift from mainly variable operating costs to up-front investment costs.

There are also advantages to installing smaller scale energy generation systems, such as:

• Incremental investment to meet demand.

• Personal and community-scale involvement and investment opportunities.

• Greater self-reliance tempered against an increase in self-maintenance.

Each of the next chapters presents a renewable energy resource New Zealand is endowed with. These are:

• Solar

• Wind

• Hydro

The lower energy density of most renewable energy sources means that more effort is required to optimise the extraction and use of these resources than fossil based energy sources.



• Marine (wave)

• Marine (tidal)

Each resource chapter is structured as follows:

• General introduction

• Introduction to the resource

• Resource uncertainty

• Barriers and limitations

• Introduction to conversion technologies

• Asset characterisation

• Research status

• Summary

The general introduction in each chapter contains a pathway overview with the most common and likely energy conversion pathways from resource to common energy carrier (i.e. to secondary distribution). The end points in this graph connect with the starting points in the Secondary Conversion section (see Section 6).

In each chapter the resource is quantified in as much as this was possible, usually through a graph projecting the potential and realisable energy capture on a map of New Zealand (Chapter: Introduction to the resource). Common conversion technologies are described as are expected trends in these and possibly new technologies.

In the end an inventory of relevant energy research options and an indication of the international and New Zealand status of these is given.

Each chapter closes with a summary on the expected developments of the resource’s contribution to New Zealand’s energy supply needs.


Section 2 Solar RESOURCES - Resources that flow perpetually

Section 2.1 Solar resources


2 – RENEWABLE RESOURCES Solar

2.1 SOLAR RESOURCES

2.1.1 General introduction

Solar energy is a universal resource with significant potential, yet only a tiny fraction (~0.05%) of New Zealand’s direct energy demand is currently provided through solar. Solar water heaters provide 0.3 PJ per year (2005), whist photovoltaic technologies (PV) provide 0.007 PJ per year. In New Zealand, the turnover in the solar water heating (SWH) industry is around $14 million per year and is around $4 million per year in the PV industry [EECA (2006)].

Many New Zealand homes are annually exposed to 20 - 30 times more energy from the sun than they use in electricity or gas. Though plentiful, the solar resource is of relatively low intensity and intermittent availability.

In New Zealand there is plenty of solar resource capacity. However, relative to other countries, the rate of uptake of solar energy technology has been very slow. This is largely due to the lack of incentives (such as the lack of a feed-in tariff to be able to sell the excess generated electricity), historically cheap electricity and a perception that New Zealand has poor solar resources.

2.1.1.1 Pathways

Solar energy is a versatile energy resource that can be used to generate low-grade2 heat, high-grade heat and electricity. Some of the common pathways for using this resource are illustrated below (Figure 2.1.1).

Figure 2.1.1 – Solar energy pathways


Thermovoltaics (STV)[Stirling generator]

High temperature thermal (SHT)[Solar tower; Solar concentrating

boiler]

Low temperature thermal (SLT)[Plate; Evacuated tube;


Hydratic System

Photo-oxidation (SPO)[Photo bioreactor] Clean & compress

Switchgear

Passive solar Windows, Insulation, Thermal mass

Photovoltaic (SPV)[Thin film, Organic, Silicon]


Steam generator

Solar thermal storage tank


Building

Industrial heat plant



National H2 network

Local H2 network

Sola

r

A full view of the pathway is presented in the Pathway Overview Map at the start of this document.

2 High-grade heat has a temperature above 120°C and can be used to generate steam and electricity. Below this

temperature, the heat has less energy and is limited to ‘low grade’ applications such as domestic space and water heating.

The estimated combined turnover of photovoltaic and solar hot water industries, in New Zealand, is around $18 million per year. Both industries are “uptake rate” limited and not resource limited.



There are three main ways in which the solar resource is used:

• Passive solar - by converting the solar radiation directly into thermal energy. In practice this consists of solar space heating or crop drying in the sun.

• Solar thermal - by converting the solar radiation into thermal energy. The thermal energy is then either stored (low temperature solar water heating) or converted into electricity through higher temperature thermal processes, generally, by using solar radiation concentration devices.

• Photovoltaic (PV) - by converting the solar radiation directly into electricity.

Apart from the solar energy captured by plants via photosynthesis, the greatest use of solar energy is passive – typically providing warmth in homes and lighting during the day. Generally, these benefits are not quantified in national energy balances, but building design simulations can quantify the amount of passive energy captured. Consideration of passive solar heating is regarded as an essential step in the design of ‘green’ or sustainable buildings. Sound building design can dramatically reduce a dwelling’s energy demand.

Solar water heating is an energy capture technology that too is generally not included in national energy balances. This technology captures and retains low-grade heat from solar insolation. Although, large-scale solar concentrating boilers and thermal ‘tower’ power generation systems have been built and operated overseas, mainly in desert areas, uptake in New Zealand is likely to be limited due to our intermittent (clouded) solar resource.

More recent developments in solar technologies have led to the development of crystalline and organic PV cells which capture solar radiation and convert it directly into electricity. Production technologies and cost effectiveness have improved rapidly over the last decade. PV cells with battery packs have become common for remote low-power and low-voltage applications such as electric fences, metering and navigation stations and telecommunication systems. Further, PV systems (with power inverters) are increasingly used for the supply of electricity to small remote communities. The upfront cost of PV systems, which is a barrier to its uptake, is often related more to the cost of storage (batteries) than the electricity generation (PV panels). The use of solar PV battery systems is only justified in remote domestic and commercial niche applications. However, due to its universality and versatility, this technology continues to attract significant funding and interest.

Solar photo-oxidation, which involves the solar-radiation-augmented biological oxidation of nutrients into energy rich compounds, is not a mature technology.

Small-scale solar energy use in New Zealand is already widespread, especially in water heating for homes, swimming pools, and communal buildings. In 2004, about 1.6% of New Zealand homes had solar hot water heaters [EECA (2008)]. For domestic use, SHW can reduce water-heating costs by 50-75% and so pay for itself through energy savings within 5-10 years. Larger-scale installations have mostly been for quasi-domestic use; motels, hostels and camp grounds, etc.

Relative to other countries, uptake of solar technologies in New Zealand is very slow, and the role of passive solar is often overlooked.



PV technology is used for many consumer devices, including automated equipment and for general power requirements at remote sites. Although it may be cost-effective for sites not connected to the local lines network, especially for low power demand, PV technology needs to achieve further performance gains before it can compete with other renewable resources for central utility supply.

The typically intermittency of the solar resource, due to day-night patterns and cloud formation is a disadvantage for centralised energy capture and distribution systems, as they rely on the installation of large, purpose-built structures which do not generate any energy when no direct sunlight can be captured. These structures concentrate the available solar energy in order to improve the conversion into electricity. Intermittency causes this system to start and stop frequently which is seen as an obstacle for this technology to be preferred over other, less intermittent, alternative sources in New Zealand.

Solar energy can be converted to electricity with PV systems or with solar-thermal technologies. At present, the latter are mostly large-scale systems for centralised generation. Large-scale plants generally use water as a working fluid and are only efficient when designed to work at high temperatures, requiring the use of solar concentration mirrors that track the motion of the sun throughout the day. There are no such systems in New Zealand, although they may be applicable in the sunniest parts of the country. New, thermoelectric (TE) material technologies that convert low-grade and high-grade heat radiation directly into electrical energy show promise, but their high costs are, presently, limiting their use to specialist applications.

New, photovoltaic technology and its associated production methods are evolving rapidly and opening up new market opportunities. The technology is becoming more robust, flexible, efficient and cost-effective. PV technologies are already preferred over other renewable generation in contexts where reliability is of utmost importance and operating conditions are harsh. The excellent scalability of PV has already seen it displace batteries in many consumer goods and remote power systems where reticulation costs are prohibitive.

Solar energy use is most cost-effective at or near the point of power consumption. Consequently, most solar energy infrastructure is likely to be installed as part of the building environment. Efficient passive solar design of buildings, along with roof mounted SHW and/or PV generation systems, are expected to lead the way. Solar PV installations may play a role in the supply and infrastructure required for electric-powered and hydrogen-powered transport.



2.1.1.2 Scale

Economy of scale is a determining factor in the success of any renewable energy generation plant. This is as equally true from the end-user’s perspective as it is from the technology developer’s perspective. Due to the, commonly, high costs associated with the installation of a domestic solar energy system, a single-family dwelling is likely to spend as much on installation fees as it is for the material cost of the system. For a similar installation fee, however, a multi-family building (multiple units or an apartment block) with a medium-sized solar energy system has significant potential to reduce the total costs per person or per apartment - as experience in Austria and Germany shows3. Further, the larger-scale solar installations can gain substantial benefits from the addition of latent heat storage components to the system whilst maintaining lower, overall, per-capita costs.

Likewise, the scale of demand for hot water within a commercial setting can determine if the costs for installing a commercial-scale SHW system outweigh the costs associated with a conventionally-powered water heating system. Comparing the scale of hot water demand and end-user fees for, e.g., a car wash, laundry or a camping site; the larger scale of demand associated with the camp site (for family bathing and cleaning facilities) would provide a better economic situation for diluting the installation costs of a SHW system than in the case for the, lower-demand, car wash and laundry situations.

From the technology developer’s point of view, economies of scale need to be achieved in reducing the cost of individual systems through the realisation of highly efficient, high-output production processes. As the majority of PV and SHW systems are deployed as “distributed generation” units, the technology developers are obliged to produce large numbers of small-scale systems, as opposed to small numbers of large-scale systems. Under such circumstances, it is difficult to dilute the cost of expensive auxiliary components associated with individual systems, and the economies of scale can only be achieved through bulk-purchasing of such components. However, like many emerging technologies, the distributed generation technologies still suffer from the problem of having to start with small production volumes and, thus, face relatively high initial expenses. For PV and SHW systems, this barrier has been overcome through the setting up of large, international production facilities that demand lower labour costs than domestic production facilities.

2.1.1.3 Myth busting

It is sometimes claimed that New Zealand has a relatively small solar resource. Located in the middle latitudes, and exposed to a maritime climate (resulting in significant cloud cover), New Zealand’s solar resource is not exceptional, but neither is it poor. The accumulated, average, yearly, solar energy gain for New Zealand is about 1400 kilo-Watt-hours per square metre (kWh/m² per year). Although this is not as high as in the desert areas of Northern Australia, the United States of America, North Africa and the Middle East (2,100-2,400 kWh/m² per year), it is higher than many European countries where solar installations have a much higher market penetration. In Europe,

3 www.iea-shc.org, IEA Solar Heating and Cooling Programme.



sites with accumulated, average, yearly, solar energy gains as low as 1000 kWh/m² per year are seen as potential candidates for solar technologies. Germany and Japan, together, account for over 75% of the total installed PV capacity in the world, even though their solar resources are of these low levels.

In Europe, solar water heating systems are often combined with space heating systems. In New Zealand, integrated systems are currently seen as too expensive and only the bare minimum systems are installed. This compromise often results in a low effectiveness of the system.

Many customers complain that solar water heaters don’t pay off over time. Problems arise from the fact that the actual efficiency and yield of the installed system is never measured and neither is the hot water use before and after installation. In most circumstances, the costs of a properly installed solar water heating system, including the hot water cylinder, are recovered within 7 to 15 years, depending on the size of the installation, the region and the local price of electricity. For larger users of hot water (such as motels, hotels and rest homes), installing solar water heating systems makes even more sense, because payback periods can be as short as 3 to 4 years.

Those not familiar with solar systems mistakenly make the maximum efficiency of solar panels the highest priority in their purchasing decision. However, the efficiency of a solar panel (PV and SHW) can often be reduced in priority unless the available capture area (the installation area available for the panels at the site) is constrained. If there are no such constraints, the most economical system, for a given power output, may be made up from a larger number of lower-efficiency panels rather than a small number of higher-efficiency panels. The kilo-Watt-hours generated per dollar spent (kWh/$) for the entire system should be the highest priority parameter. The effectiveness of the system at making solar energy available to the demands of the end-user, or “yield”, will also depend on how well all the other components of the system work together, and this can even depend on the demand patterns of the users where an energy storage device forms part of the total system.

Accurate planning for the installation of solar panels can draw upon the guidance of computer aided designs and simulations. These simulations can factor in specific characteristics of the panels to be used and can model how these panels will respond to the weather patterns expected to exist at the intended installation location. Further, solar panels require good year-round exposure to the sun, avoiding any shading, especially during potentially high yielding hours, and accurate geographical information can help to determine if the ideal direction of the panels is something other than north-facing.

Finally, it should be noted that solar panels can be considered as an alternative building material at the outset of a construction project, rather than being an “add-on” feature once the construction has been completed. Solar panels can be integrated, seamlessly, into the urban environment as roofs, solar façades, and motorway sound barriers and, by doing so can displace the costs of conventional materials during the construction survey phase of the development.



2.1.2 Introduction to the resource

Due to New Zealand’s geographical position on the planet, it cannot expect to receive the full intensity of the incoming radiation power (insolation or irradiance) of the Sun, as the Sun is never positioned directly overhead. Also, due to the country’s maritime climate, clouds often block and disperse the incoming flux of solar rays, as illustrated in Figure 2.1.3, which shows the different processes that influence the flux of solar radiation as it passes through the atmosphere towards the Earth.

As an illustration of the overall quality of the solar resource in New Zealand, Table 2.1.2 shows a comparison between yearly-average, solar energy insolation measured at sites within Germany, Japan and New Zealand. As previously mentioned, Germany and Japan currently account for over 75% of the world’s installed PV capacity, and both accumulate significantly less solar insolation than New Zealand:

Table 2.1.2 – Comparison of solar resources

Kassel (middle of Germany) 980 kWh/m² per year Tokyo (Japan) 1090 kWh/m² per year Auckland (New Zealand) 1530 kWh/m² per year

Source: Retscreen / NASA

The quality and characteristics of the solar energy resource can be measured in three ways, two of which, intensity and diffusivity, have already been mentioned above and the third important property is chromaticity:

• Intensity – the measured power, insolation or irradiance of solar radiation falling upon a surface.

• Diffusivity – the degree to which the direct beams of solar radiation from the Sun are scattered from their direct path by obstacles within the atmosphere (e.g. clouds and dust particles). When solar intensity measurements are taken, they can be characterised as direct or diffuse radiation measurements, and when summed together they are referred to as global radiation measurements.

• Chromaticity – the spectrum of wavelengths of light (photons) within solar radiation. This includes all the ranges of coloured light that we see in the visible spectrum of the Sun’s radiation, plus those outside of the visible range in the Infra-Red (IR) and Ultra-Violet (UV) spectral ranges.

It is important to recognise these different qualities within the solar radiation resource, as different solar energy conversion devices respond differently to each. For example, for concentrating solar collectors the distinction between direct and diffuse radiation is important, as these do not concentrate the diffuse fraction of the solar radiation; only the direct fraction determines the energy yield of the device.

Other solar capture devices, notably flat SHW and PV panels, can make use of both the direct and diffuse fractions. The proportion between direct and diffuse radiation depends on the surrounding environmental conditions, such as cloud-cover and landscape (water, snow etc.). For certain devices, it can actually be economical to use a sun tracking mechanism in order to keep their receiving surfaces pointing in the direction of maximum solar intensity. However, an analysis of the benefits of tracking systems, graphically displayed in Figure 2.1.6, indicates that the direct



radiation captured on a tracking plane (for a solar concentrating system) is comparable to the total flux on a fixed, tilted plane. This demonstrates that tracking does not necessarily yield greater energy recovery and investment in solar tracking units may only be justified for niche applications requiring high-heat loads. Note, also, that this analysis concludes that the effect of latitudinal location of a device is less significant than the affect of cloud-cover on device performance.

Some modern PV devices, such organic, Cadmium-Telluride (CdTe) and Gallium-Antimonide (GaSb) based PV panels, have been engineered to make use of wavelengths of sunlight that are beyond the visible spectrum (IR and UV spectra). These devices can be used to compliment or displace conventional Silicon based solar cells that respond, mainly, to the visible spectrum within sunlight.

Figure 2.1.3 - Relationship between insolation (displayed in alternative units of W/m2) at the outer atmosphere and at the Earth’s surface

Solar radiation intensity (insolation) at the top of the atmosphere is a relatively constant at 1367W/m² and is called the solar constant. The actual insolation reaching the Earth’s surface is lower than this, but is still fairly close to this figure (more than 1000 W/m²). The insolation also varies with the time of day and seasons. The latitude of a site or location also has an influence on the insolation, as does the height of the location. This is caused by the depth of the atmosphere through which the solar radiation needs to travel (a typical, average, depth of atmosphere often used is 1.5 atmospheres). The atmosphere also causes the radiation to disperse through diffusion with and reflection off particles within the atmosphere.



Despite regional-scale solar resource mapping by NIWA’s National Climate Centre there have been no formal attempts to quantify the solar generation opportunities at a more detailed scale in New Zealand. Therefore a system was developed to translate this knowledge of solar irradiance into prospective solar generation. The procedure used to assess prospective solar generation potential is described below.

The New Zealand, mean, daily, global solar radiation data for the period 1972–2006 were gathered and updated from a total of 141 NIWA distributed climate-recording station sites. The data was standardised to account for relative variations in latitude, longitude, and percentage of cloud-free skies, and, where insufficient station data existed, the available data were weighted by the number of years of measurements available.

To assess the solar energy resource available to various types of solar energy devices, it was necessary to characterise the direct and diffuse components of radiation within different “global” insolation measurements. Based on complete spectral analyses of the solar radiation reaching stations at Kaitaia, Paraparaumu, Invercargill, and Lauder, an algorithm was developed to determine the impact of solar device tilt and the effects of cloud cover on energy collection capacity. At latitudes far from the equator, the local vertical flux of direct radiation is much reduced and, therefore, solar panels are normally tilted in a direction towards the equator (pointing northward when in the Southern hemisphere) at an angle equal to the latitude. In Figure 2.1.4 and Figure 2.1.5, the mean, annual, global insolation arriving at a plane collecting surface is displayed for both horizontal and tilted (with respect to latitude) surface conditions at various locations around New Zealand.

As mentioned previously, the algorithm was also used to determine the solar energy accumulated by systems that track the sun instead of having a collecting surface that points only in a fixed direction. Although these devices maximise the capture of direct solar radiation, they lose some of the energy available in diffuse insolation as they tilt further towards the horizon and, therefore, see more of the ground and less of the sky within their global field of view.

As a rule of thumb, solar systems are designed for 3.5 hours of direct solar-equivalent sunshine per day in summer, and 1.5 hours per day in winter.



Figure 2.1.4 – Mean, annual, global, solar insolation (irradiance) on a horizontal surface



Figure 2.1.5 – Mean, annual, global insolation (irradiance) on surface tilted with respect to its degree of latitude angle



Figure 2.1.6 – Mean, annual, direct, insolation (irradiance) accumulated by a direct-solar-energy collector fitted with a solar-tracking device



2.1.3 Resource uncertainty

The availability of solar energy is determined by the angle of the sun, which changes throughout the day and through the year, and by the extent of cloud cover. On a very overcast day, the available solar energy resource can be reduced by as much as 90% of the clear-sky value. This variability is illustrated in Figure 2.1.7:

Figure 2.1.7 – Indicative seasonal solar variation in global, solar insolation

Figure 2.1.8 illustrates, further, the variability observed in the diffuse and direct radiation fractions of solar radiation due to the effects of cloud cover during different times of the day. The graphs compare the global and diffuse radiation measurements from a horizontally aligned device with the direct radiation measurements from a solar-tracking device over three different days in Paraparaumu. Within each graph, modelled data indicate the optimum radiation levels expected for a cloud-free day:

Figure 2.1.8 – Variations in the global, diffuse and direct fractions of insolation due to cloud cover

(3 panels: a clear day, a clouded mid-day and a clouded morning)



2.1.4 Barriers and limitations

Although solar water heaters represent a developed and proven technology and the market potential for solar systems is very large, there are a number of barriers that limit the uptake of these technologies. Some of the main factors include:

• Large capital and installation costs when compared to the alternative options of using existing electricity and gas utilities.

• The price of solar systems is often perceived to be too high. Large upfront costs for small domestic applications result in a payback period of often more than 20 years. A related issue is that a solar water heater or PV system is not currently perceived to add value to a house, so it is not viewed as an investment. In particular, the main barrier to the mainstream uptake of PV technology is cost, with a 1.5 kW (peak rated power) grid-connected system costing between NZ$17,000 and 30,000 (installed, including GST).

• Trust among consumers in the current industry is low, as the technology is not considered mainstream. Although warranty issues with the technology are covered in the Consumer Guarantee Act, there is concern that the limited number of servicing agents will lead to long delays in having (essential) services returned.

• Many occupiers do not have sole ownership or occupation of their building, as in apartment blocks and complexes, and this may lead to difficulties in agreeing on how to install and pay for the system.

• In most cases, a building consent is needed, adding significant costs to the installation.

• The unfounded belief that New Zealand has a poor solar resource.

• Visual acceptance of a system on the roof is still lacking.

Lack of information, misconceptions and misinformation put people off investing in new solar energy systems, but there are initiatives currently underway to address some of these issues. These initiatives include:

• A government grant (currently $500 for approved installations) is available to consumers, through the Energy Efficiency and Conservation Authority (EECA), to install solar water heaters.

• A Home Energy Rating Scheme was launched in December 2007 by EECA (www.energywise.govt.nz/yourhome/home-energy-ratings). The scheme aims to make people more aware of the energy performance of their houses, although it is only voluntary at present.

• SolarSmarter website (www.solarsmarter.org.nz) provides information on solar water heaters to both potential consumers and the building industry.

• There is a lack of familiarity with solar energy technologies and their potential among participants within the building and architecture industries. Hence, there is reluctance towards offering or supporting solar system installations, although industry initiatives are underway to improve this.

Since there is little expectation of centralised, commercial-scale solar facilities being set up around New Zealand in the short to medium term, solar energy capture systems are only likely to be adopted by the urban and agricultural populations. The total amount of solar energy likely to be realised is, therefore, limited in geographical extent by this barrier, or restriction, to within areas of high-density population, as indicated by Figure 2.1.9.



Figure 2.1.9 – The realisable solar energy capture (tilted plate) under restricted urban and agricultural developments



2.1.5 Introduction to conversion technologies

2.1.5.1 Passive solar

Passive solar construction uses the sun to provide warmth and light in buildings during the day. Heat is absorbed into the building and slowly released back as it cools. This is achieved through appropriate building design (e.g. the use of atriums for heating and using eaves that block the sun in summer but not in winter to reduce air cooling requirements). These practices are significantly enhanced by using thermal inertia in the building (concrete and brick) and high levels of insulation. The actions of including passive solar heating, thermal mass and insulation are mutually beneficial. Another important role of passive design is in helping to avoid over-heating in the summer through the use of shading devices.

Passive solar heating is regarded as an effective and important consideration in the design of new buildings. Sound building design can dramatically reduce a dwelling’s energy demand, although storing solar heat for more than a few hours is more difficult. When direct solar radiation is used for lighting and heating as an alternative to the use of electricity in domestic buildings, it is an extremely cost-competitive use of the solar energy resource.

2.1.5.2 Solar hot water heating

Solar hot water heating (SHW) technology can capture and retain low grade heat from solar insolation at relatively high efficiencies (up to 80%). These systems typically consist of a solar collector panel to absorb the solar radiation, a transfer fluid (usually water or glycol) to move heat from the solar collector to a storage cylinder where it is stored as heat in warmed water. Heat exchangers can be used to separate the transfer fluid from the stored water and to separate the stored water from the water that is used by the occupants. Figure 2.1.10 shows a typical example of a solar collector panel component of a domestic SHW system that has been mounted onto a roof of a domestic dwelling and which uses a frame to increase its tilt angle.

Figure 2.1.10 – Example of a SHW solar collector panel

Standard SHW systems can produce around 75 - 100% of a household’s water heating in summer and between 25 - 45% in winter. Most home solar water heaters systems produce up to 15 kWh/day on a sunny summer day, and up to 7 kWh/day on a sunny winter day. As a large proportion of the energy used in a household is for hot water and space heating services (see Figure 2.1.11), the total



household energy consumption could be reduced quite considerably if these services were provided for by solar energy.

Figure 2.1.11 – New Zealand, domestic household energy end-use break-down

Range, 6%

Refrigeration, 10%

Lighting, 8%

Other Appliances, 13%

Hot Water, 29%

Space Heating, 34%

Source: BRANZ, 2007

The solar collector panel on a domestic SHW system is typically between 2 m² and 6 m². The collector size should be correctly rated to the capacity of the hot water storage cylinder, observing a ratio of about 1 m² of collector per 40 - 70 litres of cylinder capacity. There are two main designs for SHW systems:

• A thermosiphon system – in which heated fluid in the collector panel sets up a natural convection flow, moving the fluid from the panel to the storage cylinder. The storage cylinder has to be located above the collector panel in this case, either along with the panel outside on the roof or nearby, inside the roof structure.

• A pumped system – which allows the storage cylinder to be located anywhere within the building, but requires an additional energy supply (electricity) to pump the heated fluids out of the collector panel and around the system. The pumped system can make use of an existing hot water storage cylinder within a building, and this is usually the more cost-effective system to install in this particular situation.

The cost of installation for a SHW system can vary widely. Complete systems, including the storage cylinder and installation, usually cost between $4000 and $8000 and requires building consent to be given, since these systems potentially interact with drinking water supplies and add additional load to the roof structure. A typical, domestic-scale, SWH system should have a lifetime of between 20 and 30 years and there are, currently, a total of about 35,000 SWH systems installed in New Zealand homes and commercial buildings.

New Zealand’s adoption of the SHW technology has lagged behind that of many other countries, and this is likely to be due to a combination of; the high costs of manufacture, purchase and installation, some poor customer experiences and mistrust and lack of coordination among the parties involved. Experiences of overseas markets suggest that this situation will improve when awareness of the technology is improved, supporting regulation is put in place and incentives are increased.



2.1.5.3 Photovoltaic (Silicon / Organic)

Crystalline and, more recently, organic photovoltaic (PV) cells have been developed to capture solar insolation and convert it directly into electricity. The efficiency and cost effectiveness of the technology has improved rapidly over the last decade. PV cells with battery packs have become common for remote, low-power, low-voltage, direct-current (DC) applications such as electric fences, metering station, navigation stations and telecommunication systems. PV systems (with power inverters) are increasingly a cost-effective alternative for the supply of alternating-current (AC) electricity to small or remote communities that are too far from an existing national grid network to be connected economically. Cost hurdles associated with large photovoltaic systems are often associated more with the storage of electrical energy (battery packs) than with the PV panels themselves, but the versatility of the electricity generated and the extremely low system maintenance requirements mean that this technology continues to attract significant funding and interest. Figure 2.1.12 provides an example of PV panels installed on the roof of a domestic dwelling and a strip of flexible, roof covering material that contains integrated PV cells.

Figure 2.1.12 – Examples of PV solar cell panels and arrays (Left: panels mounted on a roof; Right: thin film roof cover on a roll)

Source: United Solar Ovonic

PV panels are rated using an expression of the peak electrical output that will occur under standard, solar illumination conditions. For example, a panel with a peak rating of 75W (75Wp) will have a power output of 75 Watts at a solar insolation level of 1000 W/m² at an atmospheric depth of 1.5 standard atmospheres and a panel temperature of 25°C. There are, however, many different types of PV panel technologies available on the market that may produce the same power output under similar conditions for different costs and sizes of panel. The cost and panel size will depend upon the energy conversion efficiency of the PV technology and upon the availability and ease of processing the raw materials involved:

• Mono-crystalline Silicon Panels – (15-18% efficiency) made from silicon wafers that are sliced from silicon with a single crystal orientation.

• Poly-crystalline Silicon Panels – (12-14% efficiency) made from wafers that are sliced from silicon that does not have a uniform crystal orientation.

• Amorphous Silicon or Thin Film Panels – (5-6% efficiency) the silicon material in these panels has no crystalline structure and can be applied as a film directly onto different substrate materials.



• Group III-V Technologies – (25% efficiency) these use materials made from Group III and Group V elements in the Periodic Table (e.g. gallium and arsenic). Their current use is limited to specialist applications, e.g. spacecraft power sources, due to their high costs.

• Organic solar cells – (1-3% efficiency) this is an emerging technology that is under development within numerous companies around the world.

• CIGS and CIS – (15-20% efficiency) these are semiconductor devices made of copper, indium, gallium and selenium (CIGS), or copper, indium, and selenium (CIS), and are especially attractive for thin film solar cell applications because of their high optical absorption coefficients and versatile optical and electrical characteristics. However, manufacturing costs of CIS solar cells are, at present, high when compared with amorphous silicon solar cells. Continuing work is leading to more cost-effective production processes and the first, large-scale, production of CIS modules was started in 2006 in Germany by Wuerth Solar.

It needs to be noted that choosing the PV technology with the highest efficiency is not the key to a cost-effective system design, unless there are significant restrictions on the available space for installation of the PV panels. For a relatively larger panel area, the cost of the system for every kilo-Watt-hours of energy converted (kWh/$) by lower-efficiency panels may prove to be a better capital investment. Over the past decade, global PV prices have reduced by 18% as cumulative production rates have doubled, and this relates to an annual cost reduction of 6% per year for the majority of the PV technologies. Despite this, PV is still a relatively expensive way to generate electricity when compared with conventional techniques, and the prospect of 3rd generation PV technologies becoming cost-competitive within the next 20 years is uncertain. However, thin film manufacturing cost reductions could lead to parity with the cost of conventional electricity supplies in less than 20 years as long as raw-material supply rates can be made to meet global demands.

Figure 2.1.13 presents one analysis of the projected PV module manufacturing cost decline out to 2011. The nature of PV technologies (including PV cells and electrical power inverters) suggests that it stands to see the fastest rate of price decline, due to increased manufacturing growth, of all the energy delivery technologies considered in this review. Further, communities and individuals may be willing to pay a premium for PV technologies because they afford a degree of self-sufficiency and security of energy supply.



Figure 2.1.13 – Overall cost decline curve for the broader PV technologies industries

Source: NREL - DOE/US Industry Partnership

The use of solar PV systems in New Zealand is well established in stand-alone applications in remote areas such as communications equipment, water pumps, lights on navigational buoys, and electric fences on farms. At present, the cost of solar panels is approximately $7/Wp to $10/Wp, such that the cost of the modules for a typical, grid-connected, 2 kWp system would be about NZ$14,000-20,000 and the total cost of a complete system about $22,000 to $40,000, generating about 2,400-3,000 kWh/year. A typical grid-connected PV system would currently generate electricity at $1.34/kWh over its 25 year lifetime, and these costs are projected to decrease to $0.76/kWh by 2015 and $0.41/kWh by 2025 [MED (2006)]. A stand-alone system will be more expensive to install, because a battery bank is required to store the electricity produced. As a point of reference, the average household electricity use in New Zealand is 8,000 kWh/year, so the 2kWp system would provide about one-third of the electricity currently used by an average New Zealand household.

For those considering the use of active sun-tracking with their PV panels, it should be noted that the cost of the wind-resistant frameworks and mounts required are such that it is rarely worthwhile. Tracking is used, and indeed it is essential, with solar concentrating systems that use movable mirrors to focus direct solar radiation onto an intensified collector area. However, the tracking mirrors gather energy from only a narrow field of view around the sun’s location, and when the sun is blocked out by cloud, the energy collection at the mirrors is drastically reduced. Such conditions, unfortunately, exist rather too often during an average day in New Zealand and explain why the gains in building a sturdy tracking system are often outweighed by the losses.

Data on the current uptake of solar PV in New Zealand are difficult to obtain, due to perceived commercial sensitivities. However, in 1999, British Petroleum Ltd (BP) launched New Zealand’s first PV-powered service station at Papakura in Auckland and by the end of 2005, 17 BP service stations in New Zealand had PV installations with a total nominal energy output of 187 kW. Based on the PV sales data reported to EECA (2005), the installed PV capacity at BP service stations in



recent years has made up about 10% of the total installed capacity of New Zealand. In addition, a survey of the main New Zealand PV distributors suggests installed PV capacity in 2001 was between 800 kWp and 1000 kWp, providing yearly PV electricity production of ~11.28 GWh [EECA (2001)]. A survey undertaken for EECA on installed PV systems in New Zealand reported “a rough estimate of total installed PV at 31 December 2004 of 1400 kWp. This is up from 750 kWp in 2001. The estimated energy output in 2004 was 2.5 GWh (0.01 PJ) of electricity. There is no breakdown of the split between grid-connected and off-grid installations” [EECA (2006), p.72].

2.1.5.4 Solar thermal technologies

Solar energy can also be converted to electrical energy via thermal processes such as in a solar-thermal power plant. At present these are mostly large-scale systems for centralised power generation. Large-scale plants generally use water as a working fluid and, hence, are only efficient at high working temperatures. This requires solar insolation to be gathered and concentrated with tracking mirrors that direct the intensified solar energy onto a heat exchanger to raise the temperature of a working fluid. There are no such systems in New Zealand; intermittent supply due to cloud cover is a factor in this, even though the average solar resource is adequate and the clear sky radiation level is excellent.

Solar thermal technologies can be divided into the following categories, which are described in detail below:

• Solar updraft towers

• Solar thermal-electric systems

• Central receiver systems

• Dish-engine systems

• Parabolic trough systems

2.1.5.5 Solar updraft tower

This technology uses the tendency of hot air to rise and directs this rising through a vertical chimney where it drives a ducted turbine to generate electricity. The generating capacity of a solar updraft power plant depends primarily on the size of the collector area at the foot of the chimney and the height of the chimney (Table 2.1.15).

A research prototype was in operation in Manzanares, Spain and was the result of collaboration between the Spanish Government and the German designers, Schlaich Bergermann and Partner [Schlaich et al. (2005)]. The solar tower was built in 1982, about 150 km South of Madrid, with a chimney height of 195 metres and a diameter of 10 metres. The solar collector was actually an arrangement of greenhouses, within which the ambient air was warmed in a traditional greenhouse manner, and had a collection area of 46,000 m². It obtained a maximum power output of only 50 kW, but its main purpose was to investigate cheap construction materials for future, low-cost versions of the technology. It was decommissioned in 1989 due to structural fatigue of the construction materials associated with the tower. A feasibility study is currently underway



concerning plans to build a 200 MW solar updraft tower station in Australia (www.enviromission.com.au).

Figure 2.1.14 – The solar updraft tower prototype plant at Manzanares, Spain.

Source: Schlaich Bergermann Solar, Stuttgart

A solar updraft power plant requires a very large initial capital outlay, which may be compensated by relatively low operating cost. The major disadvantage of a solar updraft tower is the low conversion efficiency, of below 2%, which is much less than can be realised by using a system that, first, concentrates the solar insolation using a system of mirrors. Consequently, a large collector area is required and this can lead to high construction and maintenance costs where land prices are expensive.

There is still a great amount of uncertainty and debate regarding the cost of electricity production from a solar updraft tower and whether a tower (large or small) can be made profitable. Schlaich et al. (2005) estimate the cost of electricity to be between 0.2 and 0.4 $/kWh, but other estimates indicate that the electricity cannot possibly be cheaper than 0.5 and 0.65 $/kWh (2005). No reliable electricity cost figures will exist until such time as actual data are available from a utility-scale power plant.



Table 2.1.15 – Key solar updraft tower parameters

Capacity MW 5 30 100 200 Tower height (m) 550 750 1000 1000 Tower diameter (m) 45 70 110 120 Collector diameter (m) 1250 2900 4300 7000 Electricity output (GWh/y) 14 99 320 680 Tower cost (Mio. €) 19 49 156 170 Collector cost (Mio. €) 10 48 107 261 Turbine cost (Mio. €) 8 32 75 133 Engineering, tests etc. (Mio. €) 5 16 40 42 Total (Mio. €) 42 145 378 606 Annuity on investment (Mio. €/y) 2.7 10.2 27.1 43.7 Annual operation & maintenance cost (Mio. €/y) 0.2 0.6 1.7 2.8 Levelised electricity cost (€/kWh) 0.21 0.11 0.09 0.07

Rated for a site with an annual global solar radiation of 2,300 kWh/m² Cost for unskilled labour assumed to be 5 €/h Interest rate of 6 % and a depreciation time of 30 years

Source: Schlaich et al., 2005

2.1.5.6 Solar Thermal electric systems

These technologies use an array of mirrors to concentrate sunlight onto a central receiver where it generates sufficient heat to raise steam. The resulting steam can either be used directly as high-grade process heat or fed into a turbine to generate electricity. These systems require significant areas of cheap land for installation of their reflectors and high insolation in order to be cost effective. Figure 2.1.16 shows an example of this configuration.

Gross conversion efficiencies, taking into account the fraction of the total area of the power plant occupied by the solar dishes or troughs, are determined by net generating capacity over the solar energy that falls on the total area of the solar plant. The gross conversion efficiencies of these systems are typically 2-3%.

2.1.5.6.1. Central receiver systems

Electrical energy is generated from sunlight by focusing concentrated solar insolation onto a tower-mounted heat exchanger receiver. The system uses hundreds to thousands of sun-tracking mirrors called heliostats to reflect the incident sunlight onto the central receiver. These plants are best suited for utility-scale electricity generating applications in the 30 to 400 MW range.

A pilot solar plant, called Solar One was built in the Mojave Desert in California, USA in 1981. It was operational from 1982 to 1986, with a maximum capacity of 10 MW. It used 1818 mirrors, with a total area of 72,500 m², to reflect sunlight onto a black-coloured receiver on a large tower. The heat was transferred to an oil transfer fluid, which boils water to run turbines. In 1995 Solar One was redesigned and renamed as Solar Two (Figure 2.1.16). This prototype commenced operation in 1996 with a total area of 82,750 m² and an efficiency of 8.5%. Solar Two was decommissioned in 1999.



Figure 2.1.16 – Solar Two: experimental solar power plant

In March 2007 an 11 MW solar concentrating power plant opened near Seville, Spain. This is the first in a set of solar electric power plants to be constructed in the same area. These plants are expected to generate 300 MW by 2013 (www.solucar.es). Closer to home, there are plans to build a 154 MW solar power station in north-west Victoria, Australia (www.solarsystems.com.au/154MW VictorianProject.html). The power station will consist of fields of heliostats focusing sunlight onto PV modules.

2.1.5.6.2. Dish engine systems

A solar concentrating dish system uses a large reflective parabolic dish to focus sunlight onto to a single point above the dish, where a thermal collector is used to capture the heat. Typically the dish is coupled with a Stirling engine to convert heat energy into electricity. The solar dish / Stirling engine systems have the highest energy efficiency of all solar concentrating technologies - the current record is a conversion efficiency of 40.7% of solar energy.

Stirling Energy Systems (www.stirlingenergy.com) in conjunction with utility company Southern California Edison plans to build a 500 MW power plant using Stirling engine/solar dish technology. The power plant will incorporate 20,000 dishes, and cover an area of 19,000,000 m². It is planned to open in 2012. A six-dish model Stirling engine / solar dish power project is currently operating at Sandia National Laboratories in Albuquerque, New Mexico.



Figure 2.1.17 – An array of parabolic dishes with Stirling engine systems (The entire unit follows the position of the sun)

Source: www.trec-uk.org.uk

2.1.5.6.3. Parabolic trough systems

Solar concentrating parabolic trough systems use a curved trough which reflects the direct solar insolation onto a hollow tube in the focal point of the trough. The whole trough tilts through the course of the day so that direct insolation remains focused on the tube for as long as the sun shines. A liquid, normally thermal oil, is heated as it passes through the tube and delivered to a heat exchanger where it heat water to raise steam to power a steam turbine. Solar trough plants have been built with efficiencies of about 20%. These systems are the most successful and cost-effective concentrated solar power system designs at present.

A solar thermal system using this principle is in operation in the Mojave Desert in California, USA, called the Solar Energy Generating System (SEGS). The system comprises nine solar power plants using parabolic trough technology along with natural gas back-up to generate electricity. The plants have a 354 MW installed capacity. The SEGS power plants were commissioned between 1984 and 1991. The facility has a total of 400,000 mirrors and covers 4,000,000 m².



Figure 2.1.18 - Array of parabolic troughs (Almeria, Spain)

Source: www.flagsol.com

2.1.6 Asset characterisation

The detail of solar assets that were incorporated into the LEAP framework are described for each viable solar energy harvesting pathway below.

2.1.6.1 Solar hot water heating

The New Zealand solar hot water (SHW) heating system industry is dominated by many small importers. There are many importers of overseas products, but very few (only 2 or 3) domestic manufacturers. The quality of imported products (panels and systems) is, in general, good when these carry quality markings like the European quality label and Solar Keymark (www.solarkeymark.org). The domestic industry struggles with overseas competition as it has lower design, production and advertising budgets available. Some larger companies have shown interest in setting up domestic production facilities, but major investments into the industry have not materialised, due to uncertainty over market developments. The unwillingness to engage in investments with an extended payback period, and the generally accepted practice of using electricity directly for space and water heating, are tough barriers to overcome.

In the average New Zealand household, about one-third of energy costs can be attributed to heating water. Standard SHW systems can produce around 75% of a household’s water heating in summer and between 25 - 45% in winter. Most home SHW systems produce up to 15 kWh/day on a sunny summer day and up to 7 kWh/day on a sunny winter day. Average savings on electricity for water heating from a SHW are estimated at $350 to $450 a year.

There are an estimated 35,000 SHW systems installed in New Zealand [(EECA (2008)]. Most of these installations are in the residential sector. The commercial and industrial market is estimated to account for less than 3% of installations, and less than 1% are installed in public buildings. About 1.6% of New Zealand homes are estimated to have a SHW system. In recent years, there has been a significant increase in installations, averaging around 40% a year, with 3,500 new systems installed between July 2005 and June 2006. If the rate of installation of SHW remains at 3,500 new



systems each year, then by 2050 an estimated 10% of New Zealand homes will have SHW. This rate of uptake of SHW will obviously increase if there is more aggressive promotion, such as new legislation requiring new dwellings to have SHW. If all new dwellings built after 2015 are required to have SHW, then by 2050 an estimated 40% of New Zealand homes would have these systems installed. To achieve this, the industry has to be capable of installing 26,000 SHW systems each year.

The ‘continuity scenario’ within the Long-range Energy Alternatives Planning (LEAP) database was developed with the following basis:

• The capacity profile was developed using the EECA (2008) figure of 1.6% of homes with SHW in 2004, with an annual increase of 3500 new systems each year until 2015. Post 2015, it is assumed that all new houses will have SHW installed as standard.

• Each SHW system is assumed to be 2.5 kW, producing 3000 kWh per year. The cost of each system is $6,000. Operating / maintenance costs are estimated at 0.5% per year over the life of the plant.

• One year has been allowed for finance and construction, and plant life is assumed to be 25 years.

• The risk profile is considered zero for all phases.

• GHG emissions are considered minimal.

• Area footprint is considered minimal.

2.1.6.2 Photovoltaic

PV systems are currently cost effective for remote sites, where grid connection costs are considerable, and in many isolated devices such as communication relays. A survey undertaken by the New Zealand Photovoltaic Association of installed PV systems in New Zealand reported "a rough estimate of total, peak, installed PV in New Zealand, at 31 December 2004, is 1.4 MWp”

Three main factors may contribute to increased uptake of this technology:

• Decline in technology capital cost. There are numerous indications (especially from China) that production costs are declining, especially in the thin film technology sector.

• Removal of lines company obligations, under the Electricity Act (1992), which may stimulate an increased reliance on remote power systems if “uneconomic” lines are not maintained.

• Incentives / feed-in tariffs are used by governments to stimulate uptake of small-scale renewable technology. The New Zealand government has indicated that it does not intend to stimulate the sector in this way.

The ‘continuity scenario’ LEAP database was developed with the following basis:

• The capacity profile was developed using the New Zealand Photovoltaic Association peak value of 1.4 MW installed capacity in 2004 with an annual increase of 15% in installed capacity.

• Each PV system is assumed to be 1.5 kW, producing 1700 kWh per year. The cost of each system is $38,000. Operating / maintenance costs are estimated at 0.5% per year over the life of the plant.



• One year has been allowed for finance and construction, and the plant life is assumed to be 25 years.

• Revenue risk is considered 1 star. All other phases have zero risk.



2.1.6.3 Passive Solar

With good design, passive solar heating could become a major source of space heating (i.e., displacing conventional heating) in new homes and buildings. Passive solar design on existing buildings generally focuses on improving the building’s insulation and orientating building and windows towards a northward orientation. NIWA is working with architects and the construction sector to create datasets to optimise passive energy utilisation by New Zealand buildings.

No passive solar energy assets were included in the EnergyScape framework.

2.1.6.4 Solar thermal technologies

Opportunities may exist in the future to utilise solar concentrating boiler technology in New Zealand. At present, the most successful and cost-effective solar concentrating boiler design is a parabolic trough.

No solar thermal technology assets were included in the EnergyScape framework.

2.1.7 Research status

The status of solar research in New Zealand reflects the current policy approach of letting the market take care of it. Investments in research and development of solar technologies are limited to niches unless the development is linked to leveraging New Zealand’s strengths (www.frst.govt.nz). It is, thus, unlikely that significant investments in research on solar thermal and PV technologies will materialise. This policy setting leaves New Zealand as an importer of technology and may lead to missed business opportunities as some of these technologies do not require large development investments. The research status is summarized in Table 2.1.19.



Table 2.1.19 – Research status (Clear indicates ‘Fair knowledge’, Green highlight indicates ‘Potential opportunity’, Amber indicates ‘Could

improve’, Red indicates ‘Knowledge gap exists’)

International New Zealand Comment Resource understanding Nearly mature Evolving

EECA, NIWA Limited spread in knowledge about and usability of this resource. NZ is just starting to make headway in this field.

Passive solar Rapidly increasing. Limited application but increasing awareness and uptake.

Value has not sufficiently been recognised in NZ, the focus is still too much on cheap, renewable hydro electricity.

Solar hot water (uptake barriers)

Varied awareness and uptake depending on national factors.

Disparity. Basic developments

Uptake is increasing. Limiting factors have been identified. But disagreement on initiatives remains.

Solar hot water (technology) Mature Mature but lagging behind European technologies. Very limited research and development.

The NZ market is very small which does not warrant national research and development, while the potential is large and the need increasing.

Photovoltaic (inorganic) Generally mature. Some cutting edge developments. Rapid (potentially disruptive) thin film developments focussed mainly on cost reduction.

Very limited NZ research and development.

Market and uptake is limited by price and alternative options.

Photovoltaic (organic) Immature Very immature & limited budget. Cawthron, MacDiarmid

Niche and breakthrough R&D is still possible from New Zealand.

Commercial scale solar thermal electricity and concentrator technologies

Evolving Immature No current national industry capability.

Despite the excellent solar intensity there is none to limited interest in NZ in this technology as opposed to Australia (large desert areas). NZ has many, more economic, alternatives (wind, hydro, marine).

Photo-oxidisation Developing Immature NIWA, Scion

Niche and breakthrough R&D is still possible from New Zealand.

Price signals Nearly mature Evolving EECA, MED, NIWA

NZ needs consistent price signals on per kWh delivered basis.



2.1.8 Summary

New Zealand has relatively good solar resources. However, compared with international trends, New Zealand is under-utilising its solar resources both for passive solar, solar heating and photovoltaic energy. Current penetration levels are far below levels in countries with less solar resources (e.g. Germany and Japan) and utilisation is several orders of magnitude below its economic potential. The same applies to the technologies (passive, active and PV); the technologies have been quite mature and research and development still continues intensively abroad, but far less in New Zealand.

Photovoltaic applications suffer from high upfront equipment cost and low efficiency (25% or less). On the other hand the durability of these systems is particularly high, maintenance free; and usually has a long life span (>20 years). In New Zealand PV electricity is unlikely to compete with mainstream large scale electricity generation (hydro and coal fired generation). It is expected that PV applications will be limited to off-grid remote electrification applications and areas where cost of energy is not the most important consideration.

Passive and active solar heating applications are cost-effective in most cases, although market barriers exist. Experiences from many overseas markets suggest that the market can improve when awareness is increased and supporting regulation and incentives are in place. In most cases solar thermal applications require a back-up heating option (e.g. wood, electricity, LPG or natural gas).

Low temperature solar applications (i.e. domestic applications) face significant competition from heat pump technologies which benefit from larger marketing and branding efforts but their running costs are dependent on the price of electricity.

It is anticipated that in future solar energy technologies or equivalent alternatives (i.e. heat pumps) are installed (mandatorily) as part of the (new) building regulation as is the case in Europe. Solar water heating and PV systems should then be well integrated in the building and complement effective passive solar building designs.

Solar thermal technologies and research and development on solar heating systems do not require the large investments associated with many other energy technologies, however developments are left to the market resulting in most systems being imported. New Zealand also has a range of alternatives for thermal energy (e.g. wood, natural gas, geothermal).

While research on large scale solar concentrator electricity generation systems is booming in certain countries, research on this technology has not materialised in New Zealand. It is not expected that large scale solar technologies will see an uptake in the near future despite the excellent, but intermittent, levels of direct solar radiation here.


Section 2.2 WIND RESOURCES - Creating a storm

Section 2.2 Wind resources


2 – RENEWABLE RESOURCES Wind

2.2 WIND RESOURCES


Wind derived electricity generation has markedly increased since the Brooklyn turbine trial in Wellington in 1993. The initial interest in growth was, partly, fostered by carbon credits awarded when New Zealand believed it would have excess Kyoto credits. Currently, the installed capacity in New Zealand is nearly 321 Mega-Watts (MW), which provides roughly 4 Peta-Joules (PJ) per year (~0.7% of primary, indigenous energy production). Another 58 MW of capacity is planned to come online in the near term. Resource consents have been filed for up to 1,700 MW of generation [NZWEA (2008a)].

On a world scale, New Zealand has exceptional wind resources. The power generation per turbine is nearly double the international average, and for this reason, wind generation is regarded as affordable and cost effective without subsidies. However, extreme wind speed and wind shear issues have challenged onshore and offshore wind turbine designs. Future investment in this technology appears only to be limited by the market pricing of electricity. New Zealand’s investment in wind turbine technology is now estimated at $680 million.

2.2.1.1 Pathways

Wind energy generation pathways considered in this report are illustrated in Figure 2.2.1. Although wind energy can be harnessed for numerous other purposes, e.g. pumping water and milling grain, these pathways are negligible in New Zealand. Generation of electricity from the wind resource is the only technology currently considered on a large scale.

Figure 2.2.1 – Wind energy pathways


Onshore wind turbines (WON)

Offshore wind turbines (WOF)


Mechanical wind drive (WMD)[Wind dam, irrigation channel,

Maise grinding]



Mechanical device (e.g. Pump, Compressed air)

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There is increasing interest in “distributed generation” using wind energy resources, especially as it provides a mechanism for realising personal energy security with private funding. Unfortunately, this scale of development is not as cost-effective as larger-scale options.



2.2.1.2 Scale

The cost of wind-generated electricity is strongly related to turbine size and the number of turbines operating. In recent years, technological advancements have seen larger machines become more attractive, particularly for off-shore sites, although economic issues remain over the high installation, maintenance and repair costs for off-shore locations. Commercial wind turbines now range in size from 0.5 to 3.5 MW per turbine. In addition, the doubling of the rated output of the ‘standard’ wind turbine has led directly to a fall of around 20 % in generation costs in Europe [European Commission (2005)]. Because of the use of “modular” wind turbines, the scalability of a wind farm is one of its biggest advantages.

Local, small-scale wind generation typically ranges from 1.5 to 20 kW per turbine, and generally only involves the installation of 1–3 turbines. Although it is feasible to generate power from a single turbine, this is not generally cost effective. Rather, the costs of a cluster of wind turbines (i.e. a “wind farm”) benefit from spreading the costs across construction, transmission, switchgear and electricity quality control and maintenance over several generating units. Generally 15–20 MW of installed capacity is required to be economic. Figure 2.2.2 shows the scale increase in commercial wind technologies over the past 30 years and the projection for the near future:

Figure 2.2.2 Evolution of (US) commercial wind technology (scale) development.

Source: US DoE, October 2006: NREL/PR-500-40462




The opponents of wind turbines sometimes claim that they contribute to bird mortality. Recent studies of bird mortality, involving collisions with stationary objects, however, do not support the absolute nature of these claims. Modern wind farms are not located in the path of bird migration routes and are no longer made up of a vast numbers of small, fast-spinning turbines with thin blades. Modern wind farm installations are made up of smaller numbers of large turbines, and these have large, broad blades that turn at low speed. Consequently, recent bird mortality studies indicate that these modern installations have an average bird mortality rate as low as 2.3 birds per turbine per year.

There is some concern that wind turbines create unacceptable noise. This idea stems mostly from older designs, especially turbines that had downstream rotors. Noise is typically generated by the rotor blades or from inside the nacelle by the gear box, generator and auxiliary equipment. Modern designs with lower rotation speeds have significantly reduced the noise from blade tips while mechanical noises from inside the nacelle have been reduced through noise insulation and gear box improvements. Consequently, most modern wind turbines are barely audible above the wind itself outside a 400 – 1000 m range.

Figure 2.2.3 - Images of wind farms from “then and now” Left: The old, early 1980s, Tehachapi Pass wind-farm, in California, USA, with many small wind turbines

(Photo: Stane Shebs). Right: A modern offshore (2.3 MW turbine) wind farm, at Nysted, Denmark, supplying 75,000 homes with energy (Siemens AG).

The Energy Efficiency & Conservation Authority (EECA) commissioned a report on low-frequency noise and infrasound from wind turbines and found that the level of emissions from current models of wind turbines is inaudible and should not cause any concern [EECA (2004)]. The New Zealand standard “NZS6808: 1998 Acoustics – The Assessment and Measurement of Sound from Wind Turbine Generators” provides strict guidance on the way in which sound from wind turbines should be measured and assessed and requires wind farms to achieve sound levels that meet World Health Organisation guidelines for preventing sleep disturbance.

In Palmerston North, which currently has the main concentration of wind turbines in New Zealand, noise does not seem to be an issue. Rather, the wind turbines there have been enthusiastically embraced by the local community and have provided a significant boost to tourism and the economy according to NZWEA (2008b).



Given the beauty of many New Zealand landscapes, a common concern is that the presence of wind turbines will adversely impact a site visually or aesthetically. Lothian (2006) examined these ideas and found that: the effect of wind turbines and wind farms on perceived scenic quality was greatest for landscapes perceived as highly scenic, and, the issue becomes progressively less for landscapes rated as lower in scenic quality (to the point where wind farms were actually perceived to enhance scenic quality). Distance to the wind farm did not appreciably reduce their visual effect. Further, varying the number of turbines indicated no clear trend, and the colour of turbines slightly affected perceived scenic quality. Based on these concerns, Lothian (2006) concluded that wind farms should avoid areas of high perceived scenic quality, particularly on the coast, and should be located in areas of low to moderate scenic quality.

As Figure 2.2.4 shows, a lot has changed in the last 30 years since the beginning of large-scale wind turbine implementations. Whatever the resistance to wind turbines may be, the issues above highlight that, for the implementation of many renewable energy generation projects, community information, consultation and involvement helps to reduce both rational and emotional resistance.

More information is available in a report written by Meridian called ‘Myths and Legends about Wind Farms’, which demystifies 13 myths about wind farms [Meridian (2005)].

Figure 2.2.4 - Examples of wind turbines integrated with the landscape

3-bladed turbine wind farm at Te Apiti, NZ

Source: NZWEA

Wind turbine building integration (Castle House, London)

Source: Norwin

Vertical-axis wind turbines artistically placed in a landscaped park in Oulu, Finland

Source: Windside




New Zealand’s location in the latitude of the “roaring 40s” provides the country with a high-quality (high-intensity) wind resource. Mountain regions and associated gorges often enhance the local wind resource, thereby providing numerous sites where wind farms become economical.

NIWA maintains a climate monitoring system across the country which now has 193 wind anemometers at 10m elevation. Data collected from this instrumentation network confirms that New Zealand experiences a high average wind speed which comes predominantly from the westerly quarter. Despite this knowledge, there has been no formal attempt to quantify prospective wind farm opportunities in New Zealand. To help understand the spatial character of the wind resource, a system to translate knowledge of the wind field into prospective wind farm locations is presented.

The procedure used to identify prospective wind farms was as follows:

• Update and re-interpolate the New Zealand onshore wind field. Collated hourly data, based on deciles, was used for this analysis. The spline interpolator used for wind field was “average daily temperature range”, since this parameter captures both wind-chill and elevation factors.

• The New Zealand offshore wind field was obtained from observation data recorded in the NZLAM weather model. This model has only been running in this mode for 1 year, so data depth is limited.

• Wind distributions were fitted to Weibull and Rayleigh distribution functions, for ease of characterisation and power transformation calculations. The suitability of this transformation made some consideration of the differences in 5-minute profiles versus hourly profiles.

• The expected wind distribution at prospective wind turbine hub heights was determined through use of a typical boundary-layer shear correlation. Application of a scaling factor (1.05) was used to account for likely mean wind speed at wind farm sites, relative to the average speed, within a grid (on-shore grid size is 0.5 × 0.5 km; off-shore grid is 4 × 4 km).

• The expected wind turbine output (kW) was derived by applying a typical Vestas V63 performance curve to the hub height wind profile. This turbine operates at 60 m hub height and has a rated electrical capacity of 1500 kW.

• For sites located east of a prevailing ridge (greater than 1:10 slope on a 0.5 × 0.5 km grid), a 5% derate of available power was applied.

• Energy density (kW/m²) was derived by application a of turbine density of 12.3 turbines per square kilometre (/km²).

• Potential generation sites were categorised into 5 tiers:

• Tier 0 (>9.0 W/m2)

• Tier 1 (9.0 – 7.5 W/m²)

• Tier 2 (7.5 – 6.0 W/m²)

• Tier 3 (6.0 – 4.5 W/m²)

• Tier 4 (4.5 – 3.0 W/m²)

The ideal location for wind power capture is an area with high mean wind speed, low wind variability and low wind shear and turbulence. High, mean wind speed provides a high amount of



energy to be harvested. Lower wind variability decreases unevenness in energy output and, hence, reduces the amount of energy storage or spinning reserve required. Meanwhile, low wind shear and low turbulence means less stress on the equipment in use.

The wind power density maps (Figure 2.2.5 and Figure 2.2.6) illustrate that maximum wind power density is observed: on top of ridges (elevation effect); between ridges (funnel effect) and in areas with long clear fetch (e.g. Western coast).

Figure 2.2.5 – Potential wind power density (on-shore)



Figure 2.2.6– Potential wind power density (off-shore)




Wind resources are variable and, to a large degree, unpredictable. The resource maps are based on data from either weather stations (on-shore maps) or combined station and satellite data (off-shore maps). These data should be sufficient to determine the average wind-speed within a coarse grid cell.

The use of averages is quite distorting in the case of wind power, as the average wind-speed value does not provide a good description of the wind-power variation. The amount of wind that can be harvested with a wind turbine is a cubic function of the wind speed (v3). The average is a sum of wind velocities without the cubic function applied, and will, thus, not result in the correct “cubic average”. For example, several severe storms in a usually calm location can give the same annual average wind speed as a location with lower, but more constant, wind speed. In the “stormy” case, the wind turbine might not operate during the extreme storm or calm conditions, due to the safety cut-out and / or the cut-in characteristics of the turbine. In our calculations, we assumed a Rayleigh-shaped wind-speed distribution with variance guided by location. This should be adequate for describing the wind distribution functions in New Zealand.

It is also important to note that, when planning the exact site of a wind turbine, varying the turbine location by only 10 m can alter the power output by several percent. The best location for a turbine in a given project is often found by ‘micro-siting’ (carrying out detailed on-site measurements and interpolations). This fine-resolution surveillance can never be achieved with the modelling methods used here, but actual site measurements have been used wherever they exist.


Based on European studies, it is expected that the proportion of New Zealand’s electricity generation derived from wind could be greater than 20% without encountering any serious technical or practical problems. This number can grow significantly if demand-side management practices are included, such as switching deferrable loads, electric vehicle-to-grid storage and voluntary flexibility from end-users. This highlights the economic and social dimensions, and not solely technical limitations, of this issue. Known factors that limit integration are: frequency management, short-term variation in wind farm output, generation scheduling, clustering of wind farms and development of standards and policy [MED (2005)]. Ongoing developments will attempt to minimise these barriers.

Wind power, at its current penetration level into the electric grid, does not seem to have significant technological barriers. Although resources consent applications may take time, money and effort to complete, almost all consent applications are completed successfully (see www.nzwea.org.nz). The limiting factor is in convincing investors about commercial viability, which is influenced by factors such as policy uncertainty, technology costs, costs of competing technologies and perceived public resistance.

Wind power requires back-up generation capacity, due to its variability, which is suitably provided for by hydro-power in New Zealand. Consumer demand is not an absolute given, in that, with the right incentives (price reductions), end-users may opt for flexibility in supply. Another option



worth looking into is the future increase in deferrable loads from plug-in hybrid cars. Intelligent matching of supply and demand is, in itself, a method of reducing supply costs and increasing the wind power utilisation factor.

The visual impact a wind turbine has is often used as an argument to prevent consent applications being approved. Both small domestic wind turbines and large wind farms suffer from this resistance from non-participating parties, whether they are neighbours or parties with other interests in the region. Europe already has many large wind turbines in urban areas and a massive wind farm presence just off-shore. If properly managed, this social barrier could be overcome in time (see myth-busting section). In New Zealand, the Resource Management Act ensures that appropriate and sustainable development occurs.

New wind power proposals need to go through a long consent approval process, which takes about 1-2 years. However, if the consent is challenged in the environmental court time delays in the order of another year have to be expected. On-site research has to be carried out over a time frame of typically 1 year to find the best turbine locations (micro-siting). Once through the consent and research process, another 1-2 years will be needed for construction, so that a total 4-5 years have to be expected from the first proposal of a development to its operation.

Some of the factors that are beneficial in wind turbine site selection are:

• A location with strong and consistent wind speeds;

• Proximity to electricity transmission lines or substations;

• Construction site should not have high conservation value and have minimal environmental impact, and not be in conflict with cultural heritage issues;

• Open land without obstacles obstructing wind flow;

• Ensure broad community support and the possibility of community involvement;

• Suitable geology (not too steep) for supply tracks and turbine foundations;

• Suitable local infrastructure (such as roading access for turbine deliveries, etc.)

Off-shore installations are, generally, in water depths less than 30 m deep. Connecting off-shore turbines to the electricity grid is an important cost factor, as is the increased difficulty of maintenance. In the off-shore resources maps, sites with anchorage depth greater than 30 m were removed. Floating turbines are anchored to the seabed by cables which keep the floating platform stable even in 30 m high seas. The company behind this technology, which has experience in designing floating installations for oil tankers, considers it can work in waters 700 m deep. Floating turbines are more costly than on land, but could supply power to both off-shore oil and gas platforms, or to coastal cities.

To illustrate how these factors affect total potential resources, suitable barriers were overlaid to the base wind map. For this analysis, the barriers applied to on-shore wind farms were: sites with inaccessible slopes (>35°); sites within conservation estates and sites with too high an elevation (>1500 m ASL). For the off-shore resource map, those sites with anchorage depth greater than 60 m were identified and removed to yield the realisable wind power density map.



Figure 2.2.7 – Realisable wind power density (on-shore)



Figure 2.2.8 – Realisable wind power density (off-shore)




Wind turbines make use of the kinetic energy of the wind to drive mechanical devices such as electricity generators. The power contained in airflow over a turbine is a cubic function of the wind speed, and is defined by:

3221 vRKP ρ=

Where:

K - Fraction of energy extracted

ρ - Density of air (kg/m³)

R - Radius of turbine blades (m)

v - Wind speed (m/s)

A turbine cannot harvest the complete wind energy, since the air cannot be completely stopped during its energy exchange with turbine blade, and must still flow away from behind the turbine. The maximum fraction of energy that can be extracted from wind, according to Betz’s law, is Kmax = 59%.

Wind turbines types are generally divided between:

• Horizontal Axis Wind Turbine (HAWT)

• Vertical Axis Wind Turbine (VAWT)

Most commercial-scale wind turbines are of the three-bladed, horizontal-axis, upwind turbine model. The primary reason for this is the higher-efficiency in moderate to good winds. Large, 5 MW wind turbines have already been installed in Europe. The high wind speeds and turbulence of the wind climate in New Zealand warrants consideration of alternative designs, such as two-bladed horizontal- and vertical-axis turbines.

Figure 2.2.9 - Examples of vertical-axis wind turbines

Sources: (L-R) Quiet Revolution, Windside on Pacific Buoy, Windspire and Windspire (by Mariah Power)

Some of the advantages and disadvantages of each wind turbine type are considered below:



Horizontal Axis Wind Turbine (HAWT)

Vertical Axis Wind Turbine (VAWT)

Adv

anta

ges

- Blades are always facing the wind at the best angle while turning. - Ability to change the wing pitch gives the turbine blades the best angle of attack in various wind strengths. Allowing the angle of attack to be remotely adjusted gives greater control, so the turbine collects the maximum amount of wind energy for the time of day and season. - Ability to pitch the rotor blades in high winds to minimize stress and damage. - Tall towers allow access to stronger wind in sites with wind shear. In some wind shear sites, every ten metres up, the wind speed can increase by 20% and the power output by 34%.

- Easier to maintain because most of their moving parts are located near the ground. - Does not need to be pointed into the wind, as the rotor blades turn vertically, a yaw device is not needed. Although stators can be used which may require turning with the wind, the moving blades do not require adjustment. - Vertical wind turbines have a higher airfoil pitch angle, giving improved aerodynamics while decreasing drag at low and high pressures and making some models especially suitable for areas with strong winds and variation. - Mesas, hilltops, ridgelines and passes can enhance powerful winds near the ground through a funnelling effect. In these places, VAWTs placed close to the ground can produce more power than HAWTs placed higher up. - Low height, and, with some models, solid structure, enables these structures to be permitted where others are not. - Does not need a free-standing tower, so is much less expensive and stronger joined together close to the ground. - Usually have a lower tip-speed ratio, so less likely to break in high winds. - They can potentially be built to a far larger size than HAWTs, for instance floating VAWTs hundreds of metres in diameter where the entire vessel rotates, can eliminate the need for a large and expensive load bearing.

Dis

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- HAWTs have difficulty operating in near ground, turbulent winds. - The tall towers and long blades (up to 90 m long) are difficult to transport on the sea and on land. Transportation can now cost 20% of equipment costs. - Tall HAWTs are difficult to install, needing very tall and expensive cranes and skilled operators. - Their height can create local opposition, based on impacts to views. - Cycling through wind speed variations between the top and bottom of the turbine can result in structural failure (caused by fatigue) of blades.

- Most VAWTs produce energy at only 50% of the efficiency of HAWTs, in large part, because of the additional drag that they have as their blades rotate into the wind. This can be overcome by using structures to funnel more and align the wind into the rotor (e.g. stators) or the vortex effect of placing VAWTs closely together or in a wind barrier structure. - There may be a height limitation to how tall a vertical wind turbine can be built and how much sweep area it can have. This can be overcome by connecting a multiple number of turbines closely together. - Most VAWTs have low starting torque, and may require energy to start the turning. - A VAWT that uses (top) guy wires to hold it in place puts stress on the bottom bearing. This problem is solved by using a rigid superstructure to hold a top bearing in place to eliminate the downward thrusts by the guy wires and the torque on the turning axis.

Figure 2.2.10 - Transport of a 61.5 m blade for a 5 MW wind turbine in Spain

Source: LM Glassfiber

Since turbine blades face a stronger wind when in the top position of their rotation, and lower at their bottom position, the turbine blade and axle suffer periodic stress with every circulation. Designs with an odd number of blades (usually three) generally handle these forces better. Likewise, blades in front of the mast are less subject to turbulence around the mast than blades on the lee ward side. It is no surprise that most commercial scale wind turbines are of the three bladed, horizontal-axis, upwind turbine model.



2.2.5.1 Offshore wind farms

Internationally, more and more offshore wind installations are emerging. Typically, the wind is more consistent (with less turbulence) and faster over the open water. This provides a better yield than for similar on-shore wind turbines. In many European nations, off-shore wind farms have been implemented, making use of the shallow waters of the Baltic and Northern Seas, whilst avoiding the often densely populated land areas. As can be seen by comparing the on- and off-shore resource maps; off-shore wind resources often yield better results than on-shore wind resources in New Zealand.

However, issues such as piling, which is only possible in relatively shallow waters, and the limited number of sub-sea electricity cables (for which installation costs can be high) reduce the off-shore options for New Zealand at the present time. Figure 2.2.12 shows the state-of-technological-development for anchoring offshore wind turbines at different coastal depths – circa 2006. Figure 2.2.11 shows some of the additional challenges offshore wind farm development faces.

Figure 2.2.12 - Off-shore wind turbine anchoring technology development (2006)


Figure 2.2.11 – Off-shore wind farm challenges




2.2.5.2 Onshore wind farms

Multiple wind turbines are usually arranged in large grids (“wind farms”), ranging in turbine numbers from a few to more than one hundred turbines. Onshore wind farms are often located where the geography enhances the wind resource. Construction (e.g. site access, roading infrastructure etc.) and grid connection costs (e.g. distance to nearest suitable grid connection point) are major cost factors that determine whether a wind farm can be operated profitably. For wind farm developments, making good use of economies-of-scale in the project planning and construction stages is important.

For landowners, wind power can provide an additional source of income, as the land can be used for, e.g., farming / grazing and wind power generation at the same time.

2.2.5.3 Distributed generation and on- and off-grid

Wind turbines are often identified with distributed generation (DG). The difference between distributed generation (close to the point of demand) and central generation lies in the link between the point of generation and point of end-use. If electricity is used within the same local (sub-) network as where it was generated, it is often called ‘distributed generation’. If DG is connected to a large network, ‘DG or central’, is then a matter of the balance between generation capacity and size of demand on the local grid. DG can, thus, be grid connected. However, due to the local demand, the grid is (mostly) not used for distributing the electricity because of large local demand. DG is also often used to distinguish between the option of many small generators (usually relatively small renewable options) and few large generators (usually gas / coal fired power stations, large hydro power dams etc.).

The difference between off-grid and on-grid is clearer. An on-grid network has a continuous connection between the local network and the national electricity grid. When the connection with the national grid is missing, it is called an off-grid network. Local generation may or may not be connected to a local network or the electricity grid.

A remote community may opt to install local (off-grid) electricity generation capacity (e.g. a wind turbine, solar PV, micro-hydro turbine) if establishing a grid connection is prohibitively expensive (too far away from the nearest grid point). If done for other reasons, such as revenue generation or self-sufficiency, a back-up grid connection is often established too.

There is increasing interest from the general public in small-scale distributed generation, especially since it provides a mechanism for realising personal energy security with private funding. Unfortunately, due to the lack of economies-of-scale, these developments are often not as cost effective as larger scale options.

Smaller-scale, distributed wind farms (around 10 MW or less) provide the following advantages:

• Less concentrated impacts on localities and communities

• Can utilise sites that would be inappropriate for large-scale wind farms

• Do not create the same tensions as larger-scale wind farms

• Add to local energy security by strengthening local electricity networks



There is increasing popular interest in small wind turbines designed for urban environments. The turbines are designed to be mounted directly on buildings, and operate well within the relatively low wind speed and turbulent wind conditions that occur at rooftop level. The swept areas are about two meters in diameter and the blades have low weight. The manufacturers say that the wind turbines have an output of 1.5 kW, which could provide between 2,000 and 3,000 kWh per year - about a quarter of the average New Zealand annual household’s electricity needs4. Critics question the expected power generation (due to the small-scale and often less than optimal location of the turbines), and cost effectiveness of the turbine, which currently retails in excess of $8,000.

2.2.5.4 Generation intermittency

Wind power is usually converted into electrical power. The main disadvantage of wind power is the variability (intermittency) of the resource relative to demand. For electricity networks with good demand-side control, much of the intermittency can be absorbed by deferrable load (e.g. hot water heating, battery recharging) or variation of supplementary supply (e.g. hydro power). As the proportion of electricity generated by wind increases (increased market penetration), the controls required become increasingly difficult.

The extent to which intermittent renewable energy sources, such as wind, can be integrated into the electricity grid depends on many grid-specific factors. The obvious ones are the variability of the wind itself and the capabilities of other generators in the grid to absorb and compensate for the power variability. Grid quality (voltage & frequency) obviously needs to be maintained. According to a study for the IEA, “the extent to which the intermittency of natural resources will become a barrier to renewables is mainly a question of economics and market organisation” [Gul & Stenzel (2005, p.3)]. New Zealand, unlike Europe, does not have a grid that is integrated across borders. New Zealand has a large ‘island’ grid and thus has to take precautions for all eventualities itself.

Because wind power has proven itself to be cost competitive in the New Zealand market without subsidies, it would be prudent to manage its intermittency and enable a high level of penetration (even above 20%) by developing a portfolio of options, including; new, flexible (thermal or hydro) plants, storage technologies (e.g. pumped hydro), distributed generation and intelligent demand-side response techniques (two-way, smart meters).

Other developments, such as managed electric-vehicle battery recharging can aid New Zealand to achieve higher wind penetration. Wind turbines may also have a role in the supply of hydrogen. A small scale demonstration project was set up in Totara Valley. The variability in the wind resource can be buffered by producing hydrogen, through electrolysis of water, and storing hydrogen for use in fuel cells when needed. Wind power can, thus, have a role in the ‘hydrogen economy’.

4 New Zealand Herald - 28 June, 2007 (page A4)




The current design lifetime of wind turbines is 20 years [DWIA (2008)]. However, few wind turbines have been operating on this time scale, since the wind power industry only started taking off in the 1980s.

A database of potential wind generation assets was developed by identifying areas capable of generating greater than 50 MW in four wind power-density tiers. The likely annual power output of these wind farms was defined by expected power factors.

Table 2.2.13 – Expected power factors of various wind tiers

Tier 0 Tier 1 Tier 2 Tier 3 Tier 4 >9.0 W/m² 7.5-9.0 W/m2 6.0-7.5 W/m2 4.5-6.0 W/m2 3.0-4.5 W/m2

Weighted Mean Wind-Power Density [W/m²]

9.97 8.23 6.73 5.22 3.70

Power factor (%) 54.24 44.80 36.61 28.41 20.16

The ‘continuity scenario’ in the LEAP database was developed on the following basis:

• Realisable wind potential generation plants were developed by identifying 50 MW wind farm sites from GIS data.

• Wind generation assets will be brought on-line to keep pace with electricity demand growth. The moratorium on thermal generation is assumed to continue until 2018, and geothermal generation will be brought on-line first.

• Based on recent projects, the construction costs are assumed to be between $1,700-2,300 / kW installed. Whilst the supply market is tight and steel prices are high, the upper bound for the costs is used (i.e. until 2012). This falls to the lower bound in later years. It should be noted that these costs are for equipment only, and do not include construction or grid tie-in costs, which often double the cost of the wind farm.

• Operational costs are considered to be $40-50 / kW per annum, which is in line with literature [EHMS (2005)].

• The time phases for each asset were typically:

• 1 year for research and planning

• 1 year (in addition to the research & planning) for addressing RMA and policy issues.

• 2 years for financing and construction

• 30 years operational life prior to major reinvestment

• All the risk is considered to be in the plant life and revenue (earning 1 and 2, respectively, out of 5 stars on the EnergyScape risk assessment rating scheme). All other phases are considered to have zero risk.



Other scenarios were developed using the same asset characterisation, but the number of assets included in the scenario was modified in accord with demand side scenarios.




Table 2.2.14 shows the current status of knowledge and the research needs relevant for the future development of the New Zealand wind energy resource:

Table 2.2.14 – Research status (Green highlight indicates ‘Fair knowledge’, Amber indicates ‘Could improve’, Red indicates ‘Knowledge

gap exists’)

International New Zealand Comment Resource mapping Mature Advancing.

NIWA New Zealand has fair near-term records, but longer histories have not been recorded.

Wind-Hydro interface

Advancing. Many studies done, indicating maximum penetration of 20-30%.

Limited – Advancing. EC, Garrad Hassan, Connell Wagner, NIWA

Interaction between wind and storage systems, particularly with NZ’s unique hydro systems (limited storage capacity) has not been undertaken.

Turbine design Nearly mature. Vestas, Enercon

Advancing. Windflow

Still significant scope to advance NZ designs to cope with NZ extreme winds.

Switchgear design Mature Advancing – mature Grid interface Mature Advancing – mature.

EC, Garrad Hassan, Connell Wagner

Wind Generation Investigation Project program (Electricity Commission) is actively addressing these questions.

Forecasting Immature Immature. NIWA, Metservice

There is active work being undertaken in this area.

2.2.8 Summary

New Zealand currently has a great deal of interest and optimism regarding wind-power generated electricity. Over the next 10-20 years, it is most likely that we will see more large-scale projects developing in New Zealand. Wind power technology is relatively mature and marginally economically viable today. Wind farms have been established and run profitably in New Zealand without any subsidies over the last decade. Looking at the number of current resource consent applications to establish wind farms, the uptake over the next few years is likely to be strong. However, it is clear that new wind projects will require broad community support to pass the consent process. Local involvement, operation and ownership may assist this process.

Intermittency in wind generation can be managed through a number of demand and supply controls. With the current predominance of hydro generation, New Zealand is well placed to accommodate a high wind-market share for grid electricity generation. Options for managing wind intermittency include matching demand through ‘smart’ demand-side management (active and intelligent electricity metering), producing hydrogen through electrolysis of water and charging electric vehicle batteries. The future is likely to see a combination of these new technologies.


Section 2.3 Hydro resources


2 – RENEWABLE RESOURCES Hydro

2.3 HYDRO RESOURCES


New Zealand has had a history of hydro generation expansion as a key component of national growth and development. Initial, small-scale, private hydro stations, in the late 19th century, served local communities and industries such as gold mining. These power stations were integrated into larger government-supported programmes of hydropower construction on major rivers and nationwide reticulation through to the late 1980s. During the period of active government involvement, the goals of “cheap hydropower” were economic expansion and improved living conditions through nationwide access to electricity. These goals were achieved through a mix of taxpayer contributions and user charges, with user charges often being kept low to encourage both uptake and consumption. Existing hydropower stations provide 5,365 Mega-Watts (MW) of installed capacity.

By international standards, New Zealand has an electrical supply system with a high proportion of hydropower. Although significant thermal and geothermal generation capacity has been constructed since the development of natural gas fields in the 1970s, the proportion of electricity generated by hydropower stations remains between 60 and 70% but fluctuates due to seasonal climatic variability.

The development of hydropower in New Zealand was initially fostered through what is known as the “Hay Report” [Hay (1904)]. This was a thorough report on national hydropower resources by the Superintending Engineer of the Public Works Department (PWD). The report was based on field investigations around New Zealand and provided a basis for systematic and prioritised hydropower development to meet national needs.

The assessment undertaken in this project identified numerous sites with realistic generation potential, amounting to 4,903 MW. An additional 662 MW of potential generation capacity, with higher construction costs, was also identified.

2.3.1.1 Pathways

Hydropower stations generally consist of an intake structure, a powerhouse and a pipeline (penstock) that delivers a flow of water, from the intake to the powerhouse, at high pressure. The energy available from a hydropower site is a combination of available flow rates (m³/s) and usable head (m) between the intake site and powerhouse.

There are diverse variations of this general configuration that may include spillways, tunnels, canals, control structures and conveyance (non-pressure) pipelines. The wide range of configurations demonstrates the innovative approaches developed by designers in order to make full use of stream flows and available head.

Since the basic principles behind all schemes are essentially the same, the only pathway distinction that has been made is between commercial / large-scale developments and distributed / community-scale developments, as illustrated below.



Figure 2.3.1 – Hydro energy pathways

Commercial and large scale hydro (HLS)

[Run of river; Modulated run of river; Tunelled hydro]

Distributed and community scale hydro (HSS)




Electricity network / GridSwitchgear

Hyd

ro Storage hydro(pumped hydro)

Storage hydro(pumped hydro)


2.3.1.2 Scale

The scale of hydropower facilities varies from innovative micro-hydro devices, based on running washing machines in reverse and delivering hundreds of watts at remote locations, through to large powerhouses with multiple generating turbines generating hundreds of MW each. However, the underlying technology remains the same, irrespective of the scale of the facilities.

New Zealand has been systematically examined for hydropower potential for over 100 years. As demonstrated by the Hay Report, the government has ensured that hydropower was expanded and considered in a systematic manner, as part of nation building. Indeed, it may be considered that the “easy” sources of hydropower development have already been developed and that remaining sites, generally, have significant barriers to development and limitations on output. Given the focus on developing “large hydro” from the 1930s to the 1980s, it follows that the sites most suitable for large-scale development have already been investigated and either developed or have reasonable information about their potential available.


There are many who still believe there is still significant potential for “cheap hydro”. This concept evaporated in the 1980’s through:

• Cost overruns on the Clyde Hydro project, which was accelerated to construction using “National Development” legislation, and the

• Financial failures of a number of small hydropower projects, including power stations at Ruahihi, Whaeo and Wairoa.

• The availability of Maui Natural gas for thermal-power generation.

• There is often significant geological integrity risk associated with the undeveloped sites.

There are still many reports of “huge” regional potential for hydropower. It is acknowledged that a number of regional studies of energy potential have been carried out over time. These typically identify thousands of Mega-Watts of additional hydropower potential in regions such as Canterbury and the West Coast. These studies typically provide a starting point for consideration of realistic potential, not an end point. Many options remain, but they represent the tail end of a prioritised list of potential schemes rather than an abundance of future attractive options.




Two methodologies have been used to quantify New Zealand’s hydro power potential:

• Analysis of NIWA hydrometric network model

• Literature review of reported hydro generation sites

NIWA has a hydrometric network model that uses knowledge of the relationship that exists between New Zealand’s rainfall and hydrology. Through research programmes that have combined direct measurements and modelling, the relationship between a relatively small number of rainfall recording sites and hydrology has been determined. This modelling approach has been essential in order to overcome the fact that rainfall data are often collected from only the most easily accessible monitoring sites, which may not represent the optimum sites for hydropower installations.

New Zealand’s theoretical, maximum, available hydropower potential was estimated by integrating the accumulated flow rate with elevation change in each stream and river. The rivers and streams were those described in the River Environment Classification digital stream network [Snelder and Biggs (2002)]; the geographical elevations were taken from the NZMS260 topographic map series and the integration technique followed the example set out by Woods et al. (2006).

The assessment developed here is a reach-by-reach assessment of power potential. Actual power generation, involving dams, exploits the potential of more than just the reach where the dam is constructed, and is dependent upon the height of the dam and the operating head. Diversion schemes also use more head than that for the reach where they divert or discharge, depending on the particular configuration of the scheme.

This analysis found that the total potential power in New Zealand streams and rivers is 66,820 MW. This is equivalent to an energy density of 0.26 W/m². Over 45% of the total potential hydro power developments are small and in steep and / or remote locations, hence unlikely to be a fruitful source of realistic power generation. The sum of potential hydro power in each catchment has been used as the background layer in Figure 2.3.2.

Extensive quantitative information on New Zealand freshwater resources has been accumulated through operation of a hydrometric network that has been geared towards hydro development needs since the 1950s. At the time the network was established, the main interest was in larger rivers and development opportunities. Indeed, there are sufficient, publically available reviews of potential hydropower developments that a comprehensive list of opportunities could be developed from undertaking a broad literature review. In developing a list of hydropower opportunities, the most useful resource was found to be the Statement of Opportunities, developed by PB Associates [Electricity Commission (2006)]. The list developed from this document was supplemented with details from additional documents covering regional studies from over the last three decades. Where available, construction cost estimates from the New Zealand Energy Research and Development Committee (NZERDC) (see [Electricity Commission (2006)]) which was active in the 1970s and 1980s were used as a basis for updated cost estimates.

Locations for all (existing and proposed) hydropower stations were determined and loaded into a mapping system for checking and presentation purposes. Duplicate proposed hydropower stations



for some river reaches were identified and the most likely option selected. All prospective hydropower development sites have been classed by indicative cost and scaled in Figure 2.3.2. Existing hydropower generation sites have been labelled.

The possibility of head being made available through diversion to another catchment at significantly lower elevation is one that could be assessed. This would need input from tunnelling experts or economists, but the identification of possible sites is an interesting Geographical Information System (GIS) problem.

An important observation about hydropower development in New Zealand, to date, is that it has concentrated on rivers with lakes above power station sites. Existing natural lakes were fitted with level control structures, and additional, controllable storage was often created by building dams and reservoirs. The storage available in these schemes has made them very valuable in supplying “base load” power, which in many other countries would be supplied by more conventional power generation plant (e.g. coal- and oil-fired thermal-power plant).

Many of the remaining development opportunities in New Zealand are of smaller scale, “run of river” schemes. Such schemes are, generally, characterised by lower reliability and greater variability of supply than for projects that have substantial storage facilities.

Some large-scale development possibilities remain, and some sites have been proposed for large-scale, pumped storage or combined irrigation / hydro projects. It is expected that new concepts will continue to emerge, but it is apparent that the “easy” projects have already been developed.



Figure 2.3.2 – Potential hydropower generation




New Zealand has a hydrometric network, configured to gather the minimum information that was considered to meet national needs at the time of development. The evolution of the network to meet emerging needs has been constrained by available funding for many years, and much of the available data is still centred on hydro development needs identified in the 1950s, i.e. larger rivers. As many of the prospective schemes are located on remote rivers and streams, flow data have not been measured and records for others are of limited duration. These remote hydro resources are not understood well enough to develop them without significant, further review.

To overcome the hydrological monitoring limitations, run-off models geared to New Zealand conditions have been developed. In order to verify the hydro potential for many prospective developments, a scheme-specific model, preferably supplemented by additional direct measurements, is needed to reduce uncertainties for plant design, construction and operation.

Stream and river catchment flow rates are subject to significant natural climate variability. Processes driving this variability include the El Nino Southern Oscillation, with La Nina and El Nino phases. This variability, and the latest realistic predictions of any other climate change processes, need to be recognised during the design process. Indications are that such variability is not well recognised or handled by the existing New Zealand power system.

There are numerous reasons why power developed at a site may be less than that assessed, including:

• Loss of flow through machines due to spillage. This is related to the amount of storage available and the relationship between inflow volumes and storage. Some development of this relationship could be made from generation / spill ratios and storage data taken from existing schemes.

• Provision of minimum flow regimes below impoundments or diversions. This is a significant factor for diversion schemes, whereas, for dam schemes, it means that generation is not always optimal from the market point of view.

• Reservoir sedimentation. Where significant, this affects the storage and, eventually, the ratio of spill to generation.


New Zealand has been systematically examined for hydropower potential for over 100 years. As demonstrated by the Hay Report, previous governments have ensured that hydropower was expanded and considered in a systematic manner, often as part of nation-building until the 1980s. Indeed, it may be considered that the “easy’ sources of hydropower development have been developed and remaining sites, generally, have significant barriers to development and limitations on output.

Construction difficulties and delays, due to long investigation times, difficult geology and steep and rugged terrain, have been widely publicised features of some hydropower developments in New Zealand. Successful development of remaining hydropower opportunities will require very careful planning and execution.



There are numerous reasons why prospective hydro developments will not be developed. In this project we have only used three criteria to define the likelihood of development of future prospects, namely:

• Scale: Smaller schemes often have insufficient flow or head for economic development and / or connection to the national grid. We have distinguished between electrical power outputs larger than 20 MW and smaller than 20 MW.

• Cost: Proposed sites have been broken down into cost bands representing: Low (less than $3,500 per kW), Medium (between $3,500 and $7000 per kW) and High (greater than $7,000 per kW) capital cost.

• Location: Sites with a National Water Conservation Order for part or all of a catchment network, or, sites inside National Parks, Wilderness Areas and, potentially, affecting Rahui zones, have been excluded wherever identified. While some very substantial hydropower assets are located inside such areas (e.g. Manapouri, Tokaanu), the assumption has been made that prospective developments in such areas are unlikely to proceed.

Based on the criteria described above, a database of existing and proposed hydropower stations was developed. The resulting database can be summarised in terms of hydropower station operating capacity (in units of MW) and number of hydropower stations.

The results for operating capacity are summarised in Table 2.3.3 and number of hydropower stations in Table 2.3.4. The tables give information on existing stations together with information from proposed stations, categorised by cost bands. The column headed “RMA” indicates sites where standard Resource Management Act processes may affect their benefits. The details of stations excluded for specific reasons (Rahui, National Water Conservation Orders and those affecting part of the DoC estate) are also shown for comparative purposes. Note that existing hydropower stations which affect parts of the DoC estate are not excluded.

Table 2.3.3 – Hydropower generation assets based on operating capacity (MW)

Exclusions Total Rahui NWCO DoC

Estate

Subject to standard “RMA” process

Existing 5,365 - - 1,547 3,818 Tier 1 (Less than $3,500/kW) 1,845 - 56 214 1,576 Tier 2 ($3,500 to $7,000/kW) 4,729 45 548 809 3,327 Tier 3 (Greater than $7,000/kW) 1,009 25 100 222 662 Grand Total 12,948 70 704 2,792 9,382

Table 2.3.4 – Hydropower generation assets based on number of developments

Exclusions Total Rahui NWCO DoC

Estate

Subject to standard “RMA” process

Existing 89 0 0 17 72 Tier 1 (Less than $3,500/kW) 28 0 3 10 15 Tier 2 ($3,500 to $7,000/kW) 212 2 20 56 134 Tier 3 (Greater than $7,000/kW) 85 1 4 21 59 Grand Total 414 3 27 104 280



This analysis suggests that there is potential to almost double New Zealand’s hydropower generation. It should be noted, however, that the average size of prospective generators (27 MW, 132 GWh/y) is, on average, less than half the average capacity of existing hydropower stations (60 MW, 317 GWh/y). The smaller average size and output of these schemes is an indication that the most favourable sites have already been developed.

Additional barriers to further development that have not been considered in this analysis include:

• The cost of environmental investigations required to properly design, construct and operate hydropower stations. Historical cost estimates typically do not include provision for these costs. It is also apparent that the extent of such investigations are related to the effect of a scheme rather than its scale, suggesting that the investigations costs of some small schemes will be greater per MW (or MWh) than for larger schemes.

• The need to provide adequate flow regimes to protect other assets and other water users in rivers affected by developments (including recreation, fisheries, aquatic ecology, etc.). Previous approaches, based around simple minimum-flow regimes, have not proved adequate. Providing adequate flow regimes poses challenges to operational flexibility (timing of generation, rate at which flows can be altered), requires complex monitoring and control and results in each factor having an affect on the operational economics.

• Availability of transmission. Generation sites can be remote from demand zones. This requires considerable investment in transmission to reach consumers and results in losses of energy in transmission.

• Modifications to waterways affect freshwater fisheries. Information on the biology and population of freshwater fisheries is often very limited. The effect of existing hydropower facilities on the populations of some species (e.g. longfin eels, lampreys, galaxiids, bullies) are already of concern. Future developments are likely to face considerable scrutiny regarding their effect on freshwater fisheries together with potential cost and timing difficulties where investigation programmes are not properly planned.

• Limited accessibility for dam or diversion construction or geologic instability.

To resolve all of the above criteria, there is a need for accurate, site specific costing of developments.



Figure 2.3.5 – Realisable hydropower generation




All hydropower stations derive work by converting the potential energy contained in water, stored above the power station, into kinetic energy at the station. It is not surprising, therefore, that they all have similar mechanical structures, namely: an intake structure, a pipeline (penstock) that delivers a flow of water from the intake to the powerhouse at high pressure, and a powerhouse which houses a turbine to convert the high pressure energy into a useable form of energy.

Prior to the popularisation of electricity, the majority of hydropower was converted to mechanical work. Now, however, such uses of hydropower are uncommon.

Conventionally, large hydropower developments construct dams to enhance the available head and dampen the flow rate variation. Storage in hydro systems is extremely desirable, as it allows variable inflows to be “smoothed” to enable generation when rainfall is limited. Storage also allows sediment inflows to be captured before entering turbines, although the effective life of this effect is limited in smaller reservoirs, which can quickly lose effective storage, given the high sediment load of many New Zealand rivers. The capacity to create water storage is limited by natural topography and requirements established through the Resource Management Act.

Power stations with little upstream storage are known as “run of river” generators. Their primary operating feature is that their generation is very directly tied to flow and, hence, their ability to meet demand is limited to periods of adequate rainfall in the upstream catchment of the river. The economics of such stations needs careful attention, as they may be unable to generate at times of maximum value to consumers.

Where considerable upstream storage exists, hydropower station operators have much more flexibility in the level of generation they produce and the timing of generation. These are essential requirements to produce “base load” power. In the New Zealand electricity system, such power stations take the place of coal-fired, thermal power stations.

New Zealand has a number of hydropower stations with reservoirs that also supply irrigation systems and there are a number of small hydropower sites on irrigation canals. However, there is a tension in concurrently meeting the storage needs for both irrigation and electricity generation as the peak demand periods do not coincide (summer for irrigation, winter for electricity).

Some of the biggest risks to hydro assets are unexpected floods and earthquakes. The different levels of robustness required define the type of dam, e.g. earth dam (Waitaki), mass-concrete dam (Clyde) and roller-compacted-concrete dams (expected in the future).

Penstocks also have significant diversity. Hydropower designers use many methods to maximise useable fall with minimum cost. Approaches used include:

• Inter-basin transfers (e.g. Manapouri)

• Tunnelling (e.g. proposed North Bank Tunnel Project on Lower Waitaki)

• Complex canal and flow control systems (e.g. Tongariro Power Development)

• High flow rate canals without concrete lining (e.g. Waitaki)



The wide range of configurations indicates innovative approaches developed by designers to make full use of stream flow and available head. Continuing innovation means that new hydropower station options may emerge in the future. Examples of techniques under desktop investigation and application in New Zealand include:

• Large-scale pumped storage, where energy losses in pumping water are offset by storage being made available at the time electrical energy is required

• Micro-hydro stations with relatively low energy yield. While energy production from such stations is small, they are located where electricity is of high value and typically have low flow requirements, minimal transmission costs and small environmental effects.


Hydropower generation is a mature technology with many locations under active or semi-active scrutiny. Existing generators and potential “new entrants” have access to experienced hydro designers who are bringing new design concepts from international experience and networks. Any appropriate new technologies are quickly assessed and applied where available.

In addition, operators of existing schemes focus on productivity and efficiency gains that add to the output (and value) of their plant. Examples include the upgrade on the Manapouri powerhouse through to the refurbishment and automation of smaller power stations.

Despite the many opportunities, there is significant debate in New Zealand regarding the role of additional hydropower developments in contributing to future energy supply. Although there is recognised opportunity for further development, many recent hydropower proposals have not been able to sufficiently minimise ecological impacts.

The ‘continuity scenario’ LEAP database was developed with the following basis:

• Only those schemes that have been publically identified as likely developments are included in this scenario.

• Installed capacity of assets was derived from literature reviews, as described above.

• Firm capacity is assessed using a plant factor of 60% for existing and larger proposed hydropower stations, and 50% for smaller proposed hydropower stations. This means that the actual output of a power plant is 50 to 60% of its theoretical maximum. The estimate for larger and existing schemes is based on analysis of output of existing plant. The reduction to 50% for proposed small hydropower stations allows for the remaining, less favourable sites.

• Construction costs were taken from published material, as described above, and adjusted to December 2008 values, using a construction cost index.

• Operating and maintenance costs are in accord with literature [MED (2003), Appendix D].

• The time phases for each asset were typically:

• 1 year for research and planning

• 1 year (in addition to the research and planning) for addressing RMA and policy issues.

• 2 years for financing and construction

• 20 years operational life prior to major reinvestment



• All the risk is considered to be in the RMA and policy issues phase (earning 3 out of 5 stars on the EnergyScape risk assessment rating scheme). All other phases are considered to have zero risk.


• The area footprint of assets was considered to be the area of the upstream storage lake, if any. The source of this data is, generally, the internet.

Other scenarios were developed using the same asset characterisation, but the number of assets included in these subsequent scenarios were modified to match demand in accord with the demand scenarios.




Hydropower generation is a mature technology with many locations under active or semi-active scrutiny. Research needs are not as urgent as other renewable energy opportunities; there are, however, still many areas where it could be valuable to fill the existing knowledge gaps.

Table 2.3.6 – Research status (Clear indicates ‘Fair knowledge’, Green highlight indicates ‘Potential opportunity’, Amber indicates ‘Could

improve’, Red indicates ‘Knowledge gap exists’)

International New Zealand Comment Resource understanding

Mature Advancing NIWA

Development of flow duration curves and better understanding of flow variability required. Investigations of a regional basis may be useful to inform potential developers of the true nature of opportunities, risks and uncertainties in flows.

Turbine efficiency Mature Advancing Generators

Hydropower companies have investigated options and opportunities for efficiency improvements and actioned these as operational opportunities where economics dictate.

Ecological impacts Immature Immature NIWA

Individual and cumulative effects of smaller potential hydro schemes are of concern. Ecological impact investigations are a large component of scheme costs. There is a lack of knowledge about fisheries biology and population distribution at most locations.

Wind – hydro (and other renewable energy) interaction

Advancing Immature EC, NIWA, UoA, Garrad Hassan

Significant knowledge gap and source of risk.

Pumped storage Stable Stable UoA

Market and uptake is limited by price and price perception

Reserve market Mature Immature Regulation is unique to NZ and does appear to support the introduction of more intermittent renewable generation.

Consenting rules Mature Immature Need for standardised guidance to support RMA



2.3.8 Summary

A review of New Zealand’s hydro generation potential has yielded a large number of possible schemes in existing literature. Based on simple construction cost and land access filters, it has been estimated that the there is realistic potential to increase hydropower generation by some 90%. Details are given below.

Table 2.3.7 – Summary of hydropower development opportunity

Operating Capacity (MW)

Firm Capacity(GWh/y)

Number of Hydropower

stations Existing 5,365 28,177 89 Tier 1 (Less than $3,500/kW)

1,576 8,162 15

Tier 2 ($3,500 to $7,000/kW)

3,327 16,495 134

Grand Total (Existing + Forecast) 10,268 52,834 238 % increase on existing +91% +88% +167%

While there is opportunity to increase the operating and firm capacity by some 90 %, this would require the development of a great number of smaller power stations. The largest proportion of future development is in Tier 2. It is probable that more thorough construction cost estimation and inclusion of investigation costs may render many tier 2 sites impractical or uneconomic.

It should be noted that all reviews of New Zealand’s hydro generation potential are optimistic because there has been little research into quantifying the barriers to development. While extensive investigation material exists for proposed hydropower stations, much of it is dated and significant review is required to properly confirm the potential. The key elements of this work are:

• Environmental investigation processes and costs. Much information that is critical to proper decision-making, on topics such as effects on fisheries and aquatic ecosystems, is sparse. Gathering this information will take time and resources.

• Construction costs. Many potential developments are in remote locations with difficult terrain. It is likely that construction costs are not particularly accurate for many potential schemes identified, as the reports reviewed are dated and many do not take into account experiences from the construction of small hydro schemes in the last 20 or so years.

• Confirmation of river flows. Hydrology information is limited at many locations. A structured programme of investigation is advisable to fill information gaps, particularly for smaller potential sites.


Section 2.4 Marine (wave) resources


2 – RENEWABLE RESOURCES Marine (wave)

2.4 MARINE (WAVE) RESOURCES


The world’s oceans have long been recognized as potentially immense sources of power. One of the earliest global estimates of wave power reaching the shore was 2.2 Terra-Watts (TW) [Kinsman (1965)]. More recent publications still quote the figure of Panicker (1976), who put the estimate of global wave power resource in deep water as 1 – 10 TW [Brooke (2003)]. However, the practical amount that could potentially be extracted is estimated to be closer to 0.2 - 0.4 TW [Callaghan (2006)]. (NB. 1 TW = 1012 Watts = 1,000 GW. It is also the approximate amount of electricity presently generated worldwide).

New Zealand is situated at an ideal location for wave energy extraction. The strong westerly winds and long fetches of the Southern Ocean are able to build up large waves unimpeded by land masses. This energy can travel long distances only to arrive and be dissipated on our shorelines. The south and west coasts are particularly exposed to this active Southern Ocean wave source.

Measurements of the wave power resource around New Zealand’s coastline are actually very sparse. Early estimates of wave power were based on visual estimates of wave properties from ships [Brown (1991); EECA (1996)]. These gave estimates of offshore wave power in the southwest of New Zealand in excess of 100 kW per metre of wave front, some of the most energetic in the world. This figure is reassessed here in light of more recent objective wave modelling studies. The barriers to exploitation of this resource are also outlined, in particular the decrease of energy available at inshore locations that are practicable for wave energy extraction.

From the energy technologies perspective, there has long been an interest in harnessing the power of the oceans using a range of energy conversion devices. Interest in the development of more commercially viable devices saw a significant growth during the oil crisis of 1973. For example, Oscillating Wave Column (OWC) devices were developed in Norway in the 1970s and 80s, a device was operational in Japan in 1984, but none of the devices have reached widespread commercial success or acceptance. With the revival in interest in renewable energy and increasing cost of fossil fuels, there has been a resurgence of developments over the last 10 years. Over 60 wave energy devices are presently either deployed, in development or proposed, with an increasing number of widely different devices connected to national grids.

This international resurgence is being reflected in New Zealand with an $8 million Deployment Fund about to assist this development over the next 4 years.

Ocean Thermal Energy Conversion (OTEC) is not considered in this report on the basis that our relatively cool surface ocean temperatures do not provide a great enough contrast to the deep ocean. In warmer waters, with access to great depths, OTEC can be exploited for electricity, desalination, or simply cool water.



2.4.1.1 Pathways

Wave energy can be exploited for electricity generation, or in some designs, for desalination. In New Zealand the demand is for electricity production, whereas, in Australia and some Pacific Island islands, the desalination pathway will have a greater importance. The most common conversion pathway is an in-situ conversion from hydraulic to turbine, with some hydraulic power conversion systems incorporating an accumulator to produce a smoother power output.

For example: Oscillating Water Column (OWC) devices commonly use a variable-pitch-blade air-driven-turbine (e.g. Oceanlinx). The Orecon OWC incorporates a third power takeoff stage in which air passes through an air-impulse turbine, converted to rotary motion, and then into hydraulic pressure before driving a generator. Several “bottom-attached” devices employ efficient direct-drive generators, for which energy conversion efficiencies of mechanical energy into electrical energy are expected to better 80% (e.g. Aegir dynamo, Trident Energy and Waveswing). The overtopping WaveDragon uses a number of low-head Kaplan turbines adapted for variable speed, as used in low-head hydro sites. A smaller number of devices pump pressurized water ashore, rather than generate electricity in-situ, and this aims to decrease costs and allows the shore-based water head to be used for desalination or electricity generation (e.g. CETO).

The Electric Power Research Institute (EPRI) study of conversion efficiencies [EPRI (2004)] has suggested power-plant capacity factor values for the different forms of wave-energy device as follows: 40% for hydraulic, 33% for pneumatic, 50% for OWC and 20% for direct-acting, reciprocating power take-off devices. These values indicate the realistic amount of power that can be generated by a device, over a given time period, relative to the “nameplate” capacity of the device. In effect, the EPRI have already attempted to model the operational environment for these devices, although this environmental analysis may not be appropriate for New Zealand.

Many of these conversion pathways are displayed in Figure 2.4.1.

Figure 2.4.1 – Marine energy pathways (Wave energy pathway circled in red)







Tidal current

Wave


Mar

ine




2.4.1.2 Scale

The full extent of power generating capacities for wave-energy devices has yet to be discovered. Some early examples of research and semi-commercial devices help to demonstrate the early potential for this technology, with existing device power outputs ranging from a few tens of kilo-Watts up to several hundreds of kilo-Watts. Near-term development goals are targeting a single device capacity of 1 Mega-Watt, which follows a similar pattern of capacity developments as observed for wind-turbine technologies.

Following this example set by the wind-energy sector, it is expected that greater power generating capacities from wave-energy devices will be delivered from farms or arrays of many smaller devices rather than all the power being delivered from a single, massive, device. The feasibility of operating such farms and arrays has yet to be determined, although the use of the Pelamis device in a wind farm demonstration project off the coast of Agucadoura, Portugal, is showing great promise. This wave-farm has been operating an array of three Pelamis devices over the latter months of 2008, and intends to expand the farm to a total of 31 devices within the coming year.


Big is not always best with marine-based power generating technologies. Several decades ago, attempts at rapid production of very large capacity devices (in the 2000 MW range), before adequate scale-testing had been completed, led to some large-scale failures. The lesson learned was that large-scale plants are accompanied by large-scale risks with this type of technology. The future may well benefit from basing large-scale wave energy farms on multiples of small-scale devices, rather than single “mega” structures.

It is not necessarily the best option to target wave energy plants in regions having the highest wave energy conditions. It is often the case that these regions are extremely remote, requiring great effort to establish supply routes during the construction phase of a project. More importantly, in extreme storms, these regions pose the largest engineering challenges in terms of forces on structures. It is consistency in the wave energy patterns that is more important than the magnitude of the extremes.




The wave energy resource to the South of New Zealand is exceptionally high by world standards. In order to quantify the resource it is necessary to have long time-series records of wave height and period. New Zealand lacks such a long-term systematic measurement database. Earlier estimates of wave power have been largely derived from visual estimates of wave height from ships and oil exploration rigs [Pickrell and Mitchell (1979)].

Ship visual estimates were used by Quayle and Changery (1981) to estimate wave power around the globe. Their estimates for offshore regions South of New Zealand were the highest in the world, at 126 kW/m, and lower values, of 70 kW/m, were determined for the West Coast. Even higher values were estimated by EECA (1996).

Some instrumented measurements have been made during oil exploration activities around New Zealand, but these were, typically, only for short survey periods of about a month. Such short records can be strongly biased by isolated high-intensity storms. Long-term measurements which allow a full seasonal assessment to be made are still needed. The one exception is a record taken from the Maui gas platform off the Taranaki coast. More recently, NIWA has maintained long-term Waverider buoy measurements off Banks Peninsula, the Wellington Harbour entrance, and a 1-year record off Hokianga.

Satellites provide valuable measurements of wave height, but they do not provide wave period, which is needed to calculate wave energy. They are, therefore, of limited value here.

In the absence of long-term, systematic measurements around the New Zealand coast, it is necessary to model the waves generated based on the widespread systematic meteorological situation data available at the time.

2.4.2.1 National total wave energy resource

An estimate of total wave energy resource available nationally can be made by integrating the energy flux around the coast, based on model results described in the next section. For this purpose, we selected the 50 m depth contour, which is considered a typical depth in which wave energy devices might be deployed. Two methods were used to integrate the flux. The first method integrates the transport of vector flux crossing the 50 m contour, i.e.:

∫ ⋅=C

dsPnEρ)

1

Where: s is distance along the contour C, and n) is the unit vector perpendicular to the contour (pointing shoreward). This sums the total power passing shoreward through the 50 m contour. This would correspond to a “wall” of perfect energy converters built along the 50 m depth contour capturing all the wave power that would pass through it, but not capturing energy propagating parallel to the contour. The total power available was found to be 97 GW (56 GW for the South Island, 41 GW for the North Island).



The second method integrates the flux magnitude along the contour, i.e.:

∫=C

dsPEρ

2

Which would correspond to capturing all the wave energy passing along, as well as through, the 50 m contour. This totalled 180 GW (110 GW for the South Island, 70 GW for the North Island). The figures should only be regarded as order-of-magnitude estimates.

For both methods, the integral has been restricted to sections of the 50 m contour on which the mean energy flux magnitude exceeds certain thresholds, reflecting the likelihood that only the higher-energy coasts will be targeted for exploitation, and that devices have a cut-in threshold. These results are presented in Table 2.4.2, below:

Table 2.4.2 – Integrated energy fluxes around the 50 m depth contour lines, for the North and South Islands, and combined

Vector flux integral E1 (GW) Scalar flux integral E2 (GW) Threshold

(kW/m) South Island North Island Total South Island North Island Total

0 56 41 97 109 69 178 20 55 33 88 106 54 160 50 34 0 34 63 0 63 75 25 0 25 42 0 42 100 1.2 0 1.2 1.5 0 1.5

2.4.2.2 The New Zealand regional wave hindcast

Numerical modelling can be used to provide wave-climate information, supplementing the limited data available from wave buoys and satellite altimeter sources. A 20-year hindcast of wave conditions in the Southwest Pacific and Southern Oceans from 1979 through 1998 has been created [Gorman et al. (2003a and 2003b)]. This hindcast will be referred to here as “NIWAM79-98”. Within the EnergyScape project, a more recently-developed forecasting system has been applied to produce a hindcast (“NIWAM97+”) of regional wave conditions from the present back to February 1997. Both simulations are based on the WAM wave generation model [Hasselmann et al. (1988)], which calculates the energy-density associated with each wave frequency and propagation direction present in the wave field at each position in a spatial domain and varying with time through the simulation. The model includes the contributions from various physical processes, including generation by wind stress, propagation, non-linear interactions, and dissipation by white-capping.

For the NIWAM79-98 New Zealand regional wave hindcast, a rectangular grid was established covering latitudes 78.75°S to 9°S and longitudes 99°E to 220.5°E (139.5°W). Spectra were computed at 16 equally spaced propagation directions and 25 logarithmically spaced frequencies, between f1 = 0.0417 Hz and f25 = 0.4518 Hz. Wind data were sourced from the European Centre for Medium-Range Weather Forecasts (ECMWF). These provide winds at 10m elevation on a 1.125°×1.125° latitude / longitude grid, at 6-hourly intervals. The same spatial resolution was applied to the wave model grid. The model was run for a 20-year hindcast of the years 1979-1998 inclusive at 3-hourly intervals over the entire grid. Outputs include summary wave statistics (e.g.



significant wave height, mean and peak wave period, mean wave direction) over the entire model domain, as well as full directional wave spectra at selected grid cells, including all cells adjacent to the New Zealand coast.

For the NIWAM97+ hindcast, a regional grid was established covering latitudes 78°S to the equator (0°) at 1.0° intervals, and longitudes 105°E to 225°E (135°W) at 1.25° intervals. The regional grid is nested in a global grid at a resolution of 3.0° in latitude and 3.75° in longitude, allowing for the effects of remotely generated swell entering the region to be accounted for. The same discretisation of frequency and direction is used as in NIWAM79-98. Wind data are sourced from the National Centre for Environmental Prediction (NCEP) at the United States National Oceanic and Atmospheric Administration (NOAA), providing winds at 10 m elevation at 3-hourly intervals. Daily sea-ice coverage data from NCEP are also used to adjust the available fetch in polar waters.

In order to obtain wave conditions at a near-shore site from the hindcast, wave spectra were interpolated from archived hindcast spectra at adjacent grid cells (using an interpolation procedure that takes account of the effects of the coastline in blocking wave approach and limiting fetch from the various wave propagation directions [Gorman et al. (2003b)]). Significant wave heights obtained from the NIWAM79-98 hindcast in this way for the Foveaux Strait site were compared with buoy data in Figure 4 of Gorman et al. (2003b).

They showed that, in moderate energy conditions, modelled and measured significant heights lie scattered quite evenly about the equivalence line, but the hindcast tends to under predict the higher energy events. From the time series comparison [Figure 4A of Gorman et al. (2003b)], it would also appear that the model shows a less rapid response to changing sea conditions than is evident in the data. This is to some extent a result of variations in the wind field being “smoothed out” due to the limits in spatial and temporal resolution of the model.

For the EnergyScape project, the interpolation procedure has been extended to provide estimated wave spectra and wave statistics over an extensive spatial domain. To do so, directional spectra, at coarse grid cells for each time, are read from archived hindcast spectral outputs, where available, and estimated elsewhere from archived significant height, peak period and mean direction parameters (assuming a JONSWAP spectral shape with cos2θ directional distribution [Hasselmann et al. (1988)]). Directional spectra are then interpolated within each coarse cell using a fetch-dependent method that removes energy behind obstructions. Wave statistics are then derived from the interpolated direction spectra, including energy flux P as described above.

This interpolation procedure was applied to outputs from the NIWAM97+ hindcast, and monthly means derived for each month from September 1997 through August 2007, to provide exactly 10 years of coverage. The largest wave heights (over 3.5 m on average) are found in waters south of New Zealand, generated by strong persistent westerly winds acting over long fetches. Swells propagating up from this region play a large part in the wave-climate in waters around most of the country, except where sheltering by land moderates their influence, resulting in mean heights less than 2 m in a large region off the northeast coast of the North Island, and in the immediate vicinity of most of the East Coast.



The 10-year average of energy flux is shown in Figure 2.4.3, with the contours and colour scaling showing the time-average of the flux magnitude P

ρ, while the arrows show the time-average value

of the vector components of Pρ

, and reflect the dominance of southwest swell described above. The highest mean energy fluxes reaching the New Zealand coast are found in Southland, with values of 80-100 kW/m. These values drop quite rapidly as we move northward, with values less than 40 kW/m for almost the entire coastline north of Bruce Bay on the South Island west coast, and the Otago Peninsula on the east coast, except for some areas averaging just over 40 kW/m southwest of Cape Farewell, as well as on the Taranaki Peninsula and the Northland west coast.



Figure 2.4.3 – Marine potential wave power ( Pρ

). Arrows indicate the direction of energy propagation.



2.4.2.3 Annual variation of wave energy

Variability of supply and the match to demand is an important factor in energy utilisation. Figure 2.4.4 shows the monthly mean values, averaged over the hindcast record over 10 years for two contrasting months: a summer month (January) and a winter month (August). Clearly, winter wave energies are higher, which is a good match with demand.

Figure 2.4.4 – Wave energy flux for summer and winter months (Left: Summer month wave energy flux map. Right: Winter month wave energy flux map)

This annual variation can be seen more clearly in Figure 2.4.5 and Figure 2.4.6 for two sites: the west coast near Auckland, and south of Stewart Island. Mean wave fluxes peak in winter, a good match to demand, but are lower in amplitude than on the Southland coast (South Cape). At the latter site, there is also a second peak in spring, which remains partly evident further north (Greymouth, Otago Peninsula). This spring peak is also evident in the maxima at most sites, indicating that it is associated with an increase in storm occurrence.



Figure 2.4.5– Wave energy flux for the Auckland west coast. The solid line shows the 10-year mean for each month in the year, while the upper and lower plots show the

minimum and maximum value of monthly mean flux.

Figure 2.4.6– Wave energy flux at a site off South Cape, Stewart Island.

The solid line shows the 10-year mean for each month in the year, while the upper and lower plots show the minimum and maximum value of monthly mean flux.




The wave hindcasts used here provide a large improvement to our knowledge of the wave energy resource. However, wave hindcasts can have bias. In the Southern Ocean the ECMWF wind-field reanalysis has been shown to tend to underestimate winds and, hence, wave height. When model grid points occur close to land, results can be biased. In this work, careful account for sheltering by land and the subsequent decrease in fetch has been taken into account. However attenuation of waves by friction with the seabed has not been. The best approach near land is to use a high-resolution model, such as SWAN, nested within the coarser WAM model used here. This is too computationally intensive for the decadal-long hindcasts here, but is feasible and necessary for site-specific surveys.

There is significant seasonal and inter-annual variation. Caution should be exercised when referring to short time series. Ideally, more direct measurements are needed over significant lengths of times (e.g. several years). Longer period climatic variations, notably the El Niño-Southern Oscillation (ENSO) cycle and inter-decadal Pacific Oscillation (IPO), should also be considered in the long-term.

Wave energy can be quite variable on a day-to-day basis. This variability is illustrated in Figure 2.4.7. However, wave energy is more continuous than wind, since wave energy can propagate large distances from where there is wind-wave forcing. In general, the predictability is good - of the order of a few days. Forecasting waves benefits from the fact that the travel time from distant storms can be several days.



Figure 2.4.7 - Variability of wave energy flux, P, on a day-to-day basis (bottom panel, black line) measured by a Waverider buoy

(Bottom panel: green line = smoothed power; yellow line = modelled power, averaged over a 20 year period)

The aim of this analysis is to give an overall view of the potential New Zealand wave energy environment. Local bathymetry (and topography) will, however, create local hot spot areas. The resolution of the present model will not resolve these features. Any deployment would, necessarily, have to examine the local bathymetry and sheltering geography in detail, using a model suited to localised areas, such as SWAN.




One of the barriers in the past has been the limited understanding of the energy resource. While the open ocean resource well off-shore can be obtained, realistic assessments must account for the limits to fetch, wave attenuation, local focussing or spreading, which can all occur in-shore. The techniques to do this at specific sites are now in place.

It is not yet possible to say what the economic level of the energy resource is, until more is understood about: the performance of devices, their costs of installation, operation and maintenance. As an example, the state of Oregon, USA, sets a threshold figure of 21 kW/m on a resource before it is considered economical for further exploration and exploitation [EPRI (2004)].

One of the main barriers to resource uptake is the accessibility of the resource. The highest wave power figures are well off-shore, in a remote part of New Zealand (southwest Westland), making the economics of infrastructure development, reticulation to shore and maintenance costs prohibitive. The higher resource areas are also most likely to experience the most extreme, damaging wave conditions. For example, a “1 in 100 year” wave could have a 35 m trough to peak height.

Most devices will initially be deployed in water less than 50 m in depth. As waves progress to shallower water, their interaction with the seabed attenuates the energy. This attenuation will be minimised where the continental shelf is narrow. It is also economically beneficial to have devices in-shore. This depth barrier is shown in Figure 2.4.8. This shows, for example, that the 50 m depth contour on the Wellington South coast is typically within 2 km of shore. It can also be seen that the continental shelf comes very close to the shore in the southwest of the country, where highest wave power is found. In other regions, such as North of Taranaki, the shelf is further out and waves will be more subject to attenuation. The attenuation will be site-specific, but can be modelled.



Figure 2.4.8 - Marine depth barrier showing the distance from shore of the 50 m depth contour.

The composition of the seabed will be important in determining the engineering required to secure a wave-energy conversion device. A map showing sand-versus-rock substrates could be generated.

Other physical constraints on deployment will arise through alternative uses of the marine environment. Both fisheries and aquaculture will have prior demands in particular areas. Customary coastal and kaimoana management are also established in certain areas. Within Cook Strait, the cable exclusion zone will exclude deployments over a significant area.

Ideally, wave devices would be located far enough off-shore so as not to impose an adverse visual impact on the natural landscape, thereby avoiding some of the controversy that wind energy has suffered. Large mussel farms are also being planned this way. However, some devices are designed for shoreline construction which will have a large local impact. These devices are also most likely to have a large local infrastructure.

A number of barriers have been combined in Figure 2.4.9. This indicates the exploitable energy resource for a typical point absorber device deployed in 50 – 100 m water depth. As explained earlier the total energy resource depends on the energy crossing a particular depth contour, rather than integration of the area. A similar figure could be obtained for shoreline devices, typically of the oscillating water column type, using a depth barrier of 0 – 20 m for example. At this stage,



conversion efficiencies are unproven for the wide range of devices emerging. To account for the typical efficiency of marine energy harvesting devices, a 10% efficiency has been applied to the above calculations. Capacity factors of 20 to 50% have been estimated by EPRI (2004).

Figure 2.4.9 – Marine (wave) exploitable energy for a point source device typically deployed in 50-100 m water depth.




A wide range of technologies are proposed to capture wave energy. A survey of web site references yielded over 60 different technologies, ranging from advanced grid-connected devices through to basic conceptual device plans. This vast array of devices can be categorized in a number of ways. They may be fixed to the seabed, floating, or partially submerged. A range of power take offs are also used. In terms of the technology, and the practicalities of deployment, it is convenient to loosely / broadly categorize them as:

• Oscillating Water Column (OWC) - both near-shore and moored

• Overtopping device - both near-shore and moored

• Moored point absorber, self-reacting

• Fixed point absorber with fixed reaction point

• Attenuator

• Terminator

Near-shore devices, which would often be built on the shoreline, will have the greatest visual impact and require use of what is increasingly regarded as prime real estate. Lower servicing costs would be a distinct advantage. A common feature of most off-shore devices is that, while the power output of an individual device may be modest (500 kW to 1 MW), it is planned to deploy them in arrays or farms of devices. This, coupled with the mooring issues, provides a commonality across many devices that may assist development. The typical size of a farm for a 20 MW output would consist of 25 – 30 devices with a 750 kW rating. With wave-energy incident at 20 MW/km, the farm would need to be spread over several kilometres of shoreline in order to minimize downstream effects.

Ideally, a device will capture the entire wave energy incident upon it, but, in reality, there is a cut-in level of wave energy that must be reached before generating and power delivery can be initiated. In addition, most devices aim to enter into a survival mode in extreme wave energy conditions. These factors restrict the total spectrum of wave energies that can be turned into useful power by the devices, and these conditions are illustrated in Figure 2.4.10.

Technology Near-shore Moored OWC Overtopping Point absorber Attenuator Terminator



Figure 2.4.10 Factors that restrict the total spectrum of wave energies that can be turned into useful power by wave devices.

Source: Carbon Trust: Future Marine Energy

(http://www.carbontrust.co.uk/technology/technologyaccelerator/performance.htm)

2.4.5.1 Oscillating water column

The concept of the oscillating water column (OWC) device is straightforward: the surging / retreating water associated with a wave crest / trough is guided into a chamber where it forces trapped air to be compressed / rarefied. This then drives a bi-directional turbine, typically a Well’s-type turbine, to generate electricity.

The near-shore, 2 MW, Osprey OWC is an example of this type of device, and hard lessons were learned from the difficulties encountered with the large-scale construction of the device under the pressures of fast-tracked testing – resulting in failure of the device in early sea trials prior to completion of the project. A more attractive proposition is to be able to mass produce these devices, for use in near- or off-shore sites, in a controlled factory environment. A Carbon Trust (2006) study concluded that a shoreline device is the preferred option when installed capacity is below 2 MW, but that offshore devices are the preferable option above the 2 MW capacity level.

One of the most prominent examples of the near-shore OWC device is the Limpet 500, produced by Wavegen, a subsidiary of Voith Siemens Hydro Power Generation. It uses a pair of counter-rotating turbines to give a rated output of 500 kW. Wavegen aims to increase output with the installation of a new variable-pitch turbine. The device is located at the island of Islay, Scotland, and has been connected to the UK national grid since 2000 (www.voithsiemens.com).

Limpet 500, Wavegen



Oceanlinx has a 450 kW near-shore OWC device in operation at Port Kembla, Australia, and is contracted to supply the local state authority. A more ambitious project, deploying 18 units of 1.5 MW, is seeking resource approval. The design size is 100 kW to 2 MW, above which multiple units are planned to be linked as part of a farm, connected by a single cable. Oceanlinx is also seeking to use the device to produce desalinated water (www.oceanlinx.com).

Offshore OWC devices include the MRC1000 multi-resonant converter (Orecon), which is a 1 MW, multi-column OWC (www.orecon.com). The Sperbuoy is a similar device that uses a single column (www.sperboy.com). Both are designed for off-shore use in farms in water depths greater than 50m (the maximum height of the Sperbuoy is envisaged as 50m). The Sperbuoy is optimized for 450 kW mean annual output per device.

2.4.5.2 Overtopping devices

Overtopping devices provide a ramp for waves to run up and overtop a reservoir above sea level. This head of water is then used to drive turbines.

Wave Dragon has a floating slack-moored device and the first prototype was connected to the grid in Denmark. A 7 MW device is planned to be deployed off the coast of Wales in summer 2008. A claimed advantage of the technology is that it can be freely scaled up (www.wavedragon.net).

2.4.5.3 Slack-moored point absorber

Point absorbers have a dimensional scale that is much smaller than the ocean wavelength and aim to harness the wave energy from oscillatory translational or rotational motion. The translational motion imposed upon the device by a passing wave may be a vertical-heave, a horizontal-surge or an angular pitch, roll or yaw motion. The moored point absorbers obtain a reaction point against themselves – usually having one component of the device moving relative to a larger, more stable component. There is a vast variety of Point Absorber designs exploiting one or more components of this wave-induced oscillatory motion, but the heave motion is the single motion that is most commonly targeted (e.g. Aquabuoy, Wavebob and the WET-NZ design, which utilises the surge and pitch motion as well).

Oceanlinx OWC

MRC1000 OWC, Orecon

Wave Dragon



The Aquabuoy (Finavera Renewables Inc) is a US example which harnesses the vertical motion, driven by wave-heave action, and reacts against water in a large vertical tube below. A 1 MW demonstration unit is planned for the Washington coast.

The Wavebob, is a self-reacting, slack moored device and there is, currently, a one-quarter-scale prototype deployed off the coast of Ireland. A full-scale version is designed to produce 1 MW.

The WET-NZ device is slack-moored with a floating arm that reacts against a more stable spar buoy. It aims to extract energy from multiple modes of motion, i.e. heave, surge and pitch. The hydraulic drive is designed to adapt to the incident wave field in order to optimise energy extraction (www.wavenergy.co.nz).

2.4.5.4 Attached point absorber

The attached Point Absorbers are similar to those above, except that they maintain an attachment point at the seabed as a reaction point. Many of these designs are planned as low-cost, mass produced devices.

Archimedes Waveswing (AWS), by Ocean Energy, resembles a cylindrical buoy with an air-filled upper casing and a lower cylinder fixed to the seabed. As a wave passes over, pressure on the upper casing induces motion between the two, which is converted by a linear, direct-induction motor into electricity.

The Australian CETO device takes a different approach by pumping high-pressure seawater ashore. At that point there is the option of generating electricity, using standard hydro technology, or desalinating water, which is becoming an increasingly important issue for the Australian market (www.ceto.com.au).

Wave Bob

WET-NZ

AquaBuoy, OPT

AWS, Ocean Energy

AWS, Ocean Energy



2.4.5.5 Attenuator

One of the most promising technologies has been used to build the Pelamis device, produced by Pelamis Wave Power, formerly Ocean Power Delivery. These devices have been deployed in Portugal and the Scottish Executive is funding four of the 750 kW devices at the European Marine Energy Centre (www.pelamiswave.com) [Scottish Executive (2006)].

2.4.5.6 Terminator

Terminator devices seek to absorb energy from along the width of a wave-front.

S.D.E. Energy Ltd., Israel, uses shoreline waves that act upon a cantilever connected to hydraulics to run a generator. Devices have been manufactured and the technology is claimed to be commercially ready, with a very low cost of US$0.02 /kWhr. The device would typically be built into a breakwater, which will limit widespread application. (http://www.sde.co.il).

The Oyster device is a near-shore, bottom-mounted Wave Energy Convertor (WEC) designed to interact efficiently with the dominant surge forces in shallow water waves, providing a device for use in easy-access shorelines with lower waves. A demonstrator unit is planned for deployment in 2007 and the peak power generated by each Oyster unit is between 300 kW and 600 kW, depending on location and configuration. A commercial wave farm, consisting of 10 Oyster modules deployed in arrays, has been proposed, and this would generate up to 4 MW of power.


International trends may help in building a picture of the scale (financial support and scale of demand) of future developments in wave-energy assets. For example, the Carbon Trust estimates that up to one sixth of the UK Governments target, for 20% renewable energy by 2020, could be met by marine renewable energy, whilst the Scottish Executive is committed to generating 40% of Scotland’s electricity from renewable energy by 2020. New Zealand has set a target of 90% sustainable energy generation by 2050. Further, the UK envisages a £42 million deployment fund for “revenue support payments of £100 /MWh for electricity delivered to the network”. “The total value of the combined financial aid to any project will be capped at £9 million and a maximum of two years will be allowed for the commissioning of projects, after which, revenue support payments will be paid for up to seven years”.

Further characterisation of wave-energy assets may have to await the dissemination of accurate energy conversion device analyses from the European Marine Energy Centre (EMEC), in the Orkney Islands, Scotland; and the South West England Wave Hub, off Cornwall and Galway Bay, in Ireland (www.southwestrda.org.uk) (www.marine.ie).

Pelamis Wave Power

SDE Energy



Offshore marine aquaculture farms are being suggested as a model upon which the future, multiple, low-cost-device-based wave farms may operate. We have yet to understand how this type of farm and operational strategy will develop, but such a farm has been established in Portugal. This farm is, currently, operating with 3 Pelamis devices and has plans for a further 25 devices to be installed.


Currently, there are no marine wave energy devices installed in New Zealand. However, interest in the field is high and increasing, with 18 marine energy projects (including tidal) in various stages of development. The recently announced Marine Energy Deployment Fund (MEDF) has added further stimulus for actual deployment. This fund, administered by EECA, has been launched “to bring forward the development of marine energy in New Zealand by facilitating the early deployment and adaptation of the technology”. The Fund is providing $8M over 4 years.

While most projects aim to import technology from overseas, a wave-energy converter is being developed in New Zealand by a consortium of IRL, NIWA and PPL (WET-NZ, www.wavenergy.co.nz). A 2 kW small-scale device has undergone sea trials off Banks Peninsula.

The Aoteoroa Wave and Tidal Energy Association (AWATEA) are providing some coordination for marine energy interests (www.awatea.org.nz).

The general New Zealand resource has been mapped as part of EnergyScape. However, detailed site-specific modelling and measurements will be required before deployment. This may also become necessary in order to satisfy Resource Consents, by demonstrating that the device deployment will have no detrimental impact on the environment (e.g. sediment movement).



Table 2.4.11 – Research status (Clear indicates ‘Fair knowledge’. Amber indicates ‘Could improve’. Green highlight indicates ‘Potential

opportunity’. Red indicates ‘Knowledge gap exists’)

International New Zealand Comment National resource understanding

Developing Advancing. NIWA, MetOcean Solutions, CAE, EECA

NZ is just starting to make headway in this field.

Site-specific resource understanding

Advancing. NIWA, ASR, MetOcean Solutions

Uptake is increasing. Several limiting factors identified by EECA.

Consistency of supply Frequency of storm events versus background levels.

Device efficiency / adaptability

Device survivability Arrays of small devices Immature Immature.

NIWA Experience will be gained from aquaculture industry.

Mooring devices Experience will be gained from offshore oil and gas industry.

Environmental impact Consulting engineers, NIWA

Commercial scale wave energy electricity generation

Immature None Internationally, lead-in tariffs are attracting developments

Switchgear / grid connection

Developing Marine Energy centres provide demonstration.

2.4.7.1 Requirements for future research

Wave power is variable from day to day. Further research is required on the consistency of supply and persistence of supply [Frazerhurst (2006)].

Most fully-commercial devices will be part of a ‘wave farm’ of relatively small devices which are economic to manufacture and deploy. Research is needed into how the devices interact hydro-dynamically, the optimal spacing of devices, the downstream impact on shoreline currents, sediment transport and surfing amenity. The farm concept has not yet been tested, although there is experience with aquaculture farms that have similar mooring and hydrodynamic issues. A small array of three 750 kW Pelamis devices have been trialled off the coast of Portugal.

The environmental impact of large-scale devices is unknown at present. This will require a significant amount of research covering a large number of areas: the physical impacts as noted above, impacts on marine mammals and impact on the local ecosystem.

Mooring design is essential to the survivability of devices, but must be designed in such a way as to not impede the efficiency of the wave energy convertor. This development will leverage off the offshore oil and gas industry, as well as large-scale aquaculture.



Many components of marine-energy device efficiency and environmental impacts will benefit from computational fluid dynamics (CFD) modelling. This has been used for a few devices for design modelling, but, as the field develops, will have much wider application.

Turbine design is subject to on-going research. Typically, an efficient bi-directional turbine is required with variable pitch blades. The traditional Wells turbine efficiency falls at high flows due to stalling.

Some devices aim to optimise their performance by adapting to the wave environment (adaptability). For example, the WaveDragon constantly adjusts its own floating height to match the wave height and has interactive mooring lines which reduce the load on lines. In extreme storm conditions, some devices de-power themselves (e.g. Pelamis, Wavebob). This will continue to be an active research area in order to enhance the knowledge of the present and future wave environment, particularly when wave-by-wave reaction is required.

2.4.7.2 Time scale

No devices are grid-connected in New Zealand as of 2008. The Marine Energy Deployment Fund aims to see demonstration units deployed in the next 4 years. Development of arrays or farms of devices are expected to grow from that initial demonstration. The rate of development of the technology will depend on the international energy (oil) price, and the desirability of moving to renewable energy.

In New Zealand, commercial production of electricity from a wave energy device is expected by 2015.

In the international context, units have been operating in a number of countries (e.g. UK, Norway, Portugal and Israel). The timescale of development has been provided by the World Energy Council (Figure 2.4.12).

Figure 2.4.12 – Roadmap for wave energy 2004 2006 2008 2010 2012 2014 2016 2018

Grid integration

Environmental & strategic environmental studies

Licensing & consents

R &

D

System optimisation

Basic component & systems

Oth

er

Second phase offshore device large farm

Second phase offshore devices small farms

Second phase offshore devices commercialO

ffsho

re

Dev

ices

Type 1 Shorline & Nearshore OWCs Type 2 OWC farms

Second phase prototype devices

Offs

hore

D

evic

esO

WC

s

Type 2 OWCs

First phase prototype devices

First phase devices large farms

First phase devices small farms

Source: World Energy Council 2007



2.4.8 Summary

Marine wave energy is an emerging technology with great potential in New Zealand. We are ideally placed geographically to capture some of the high wave-energy generated in the Southern Ocean. The national resource has been broadly mapped, but local-scale, in-shore modelling is required to ensure devices are optimally located.

The oil price and the quest for carbon-neutral renewable energy have stimulated the development of a range of new wave-energy converter devices in the last decade. These range from large structures fixed to the shoreline to smaller off-shore devices which are likely to be deployed in arrays or farms. At this early stage of development, device efficiencies, engineering robustness, and resulting economics are still being evaluated. Guidelines for environmental impact are yet to emerge.


Section 2.5 Marine (tidal) resources


2 – RENEWABLE RESOURCES Marine (tidal)

2.5 MARINE (TIDAL) RESOURCES


The perception that significant energy can be harnessed from ocean currents has led to much speculation and optimism about the role that it might play in New Zealand’s energy future. New Zealand certainly has some significant ocean current (tidal) resources, but the technology for converting energy from ocean currents into useable energy is still embryonic. In this section, we identify what we, currently, do and don’t know about the basic resource and discuss the technological approaches that are publicly available. The economic and environmental issues associated with these devices are then addressed, and the future for the industry is speculated upon. Suffice to say that there are, currently, no tidal energy devices deployed around New Zealand’s coastal waters, but that there is government support for this resource to contribute towards New Zealand’s future energy network.

The resource analysis described within this report suggests that the majority of available energy is located in Cook Strait. A key point here is that these tidal flows are, potentially, not strongly bi-directional, and, the water is reasonably deep, making the resource accessible using, e.g., vertical-axis turbine devices.

Tidal energy-conversion technologies are divided into a few particular types, with classification based on the type of mooring required and the axis orientation of the device’s mechanical-drive. Four classes of device, with generic characteristics, are described in the following sections. However, development of these technologies is such that only a handful of devices have been tested at anything like full-scale. Successful deployments of tidal devices have been reported; in the Straits of Messina, Devonshire, UK; the Orkney Islands and in the Hudson River, USA. Present power outputs for individual devices are generally described to be in the region of up to 300 kW, with future outputs suggested as extending out to the 0.5-1 MW range.

The effects of, and operation of, large-scale arrays of such devices have yet to be assessed and there is, therefore, uncertainty over the issues of environmental impact, device deployment and maintenance and effects that may reduce the tidal resource itself.

2.5.1.1 Disclaimer

The tidal energy industry is developing rapidly, and, in many instances, results of developments are commercially sensitive. Consequently, accurate referencing and verification is difficult, and reliable financial information is almost impossible to resolve. It is advised that quantification be treated with caution. Reviews from the UK Sustainable Development Commission [SDC (2007)], Edinburgh Designs and the University of

Definitive operational and performance data are lacking within the community, often because of commercial sensitivities. Therefore, a cautious approach to the use of all data should be applied!



Strathclyde5 ( provide useful overviews of the state of the industry. Locally, the Australasian Wave and Tidal Energy Association (AWATEA6) provide an informative newsletter to members. In addition, ABP MER Consultants produced a recent report which includes an attempt to classify devices and approaches similar to here [ABP MER (2007)]. In a related fashion, the Electrical Power Research Institute [EPRI (2005)] provides an in-depth calculator based on tidal variability, although this does ignore other drivers of operational variability (and reasonably so in some circumstances).

2.5.1.2 Pathways

Because all tidal energy capture devices are remote from the locations of energy demand, all devices that are in the process of commercialisation have been designed to generate electricity. Some of the generic types of tidal energy capture device are illustrated below.

Figure 2.5.1 – Marine energy pathways (Tidal energy pathway circled in red)







Tidal current

Wave


Mar

ine



It is unfortunate that the actual level of knowledge and understanding of tidal power does not meet the general public’s expectation. Considering the wealth of encouraging marketing and media reports available from the internet, it is not difficult to understand why this misconception exists. Generally speaking, positive claims and reporting of the technology appear within the “forward-looking” statements on the web sites of tidal-energy conversion device manufacturers. However, these need only to highlight the possible potentials of tidal energy resources without making any attempt (or legal obligation to) verify the realistic penetration of their technology into any specific, local tidal resource. Therefore, it must be admitted that marine energy from tidal power cannot be expected to solve all the world’s energy demand issues in an instant.

The ability to predict the future generating output capacity of any installed tidal power plant is also an area where public perception out-stretches technical reality. It is fair to say that tidal heights can be forecast with an acceptable degree of accuracy, within the constraints of being able to predict the weather (barometric pressure patterns will affect storm and surge tide levels). The tidal currents that actually “drive” tidal-energy-conversion devices, however, have additional factors of local variability that relate to the turbulent eddies shed from coastal features. Therefore, the concept that

5 University of Strathclyde www.esru.strath.ac.uk/EandE/Web_sites/03-04/marine/tech_concepts.htm. 6 www.awatea.org.nz.



power outputs from these devices will be “totally predictable years in advance” is unfounded. Furthermore, the use of “spring tide magnitude” data to categorise opportunistic locations for deploying tidal power plant does not represent a reliable method.


Tides are mainly driven by the gravitational pull of the Moon and Sun on the ocean. The Moon has the more significant influence as it is the closer to the Earth. New Zealand has semi-diurnal tides and this twice-daily rise and fall of sea levels is primarily caused by the main lunar tide, known as the “M2” (the ‘M’ stands for Moon, and the ‘2’ for twice a day). The time between high tides varies from day to day because the orbits of the Moon around the Earth, and that of the Earth around the Sun, are not exactly circular. On average, the Earth rotates one complete revolution beneath the Moon every 24.8 hours, so that the M2 occurs in half this time, i.e. in 12.4 hours.

Stevens and Chiswell (2004) provide a layperson’s description of tides around New Zealand, which are moderate by world standards. That is, tidal amplitudes around New Zealand are not particularly large, with spring tides reaching around 4 m on the North-West coast from Hokianga down to Tasman / Golden Bay (see Figure 2.5.2). This compares poorly with the 16 m plus tides of the Australian North-West shelf, Brittany or the Bay of Fundy. However, it is sufficient to create substantial flows in harbour entrances (e.g. Hokianga, Kaipara and Manukau). Additionally, large flows are found in Te Aumiti (French Pass) and Tory Channel. Lesser flows, but perhaps more accessible, are found in between Kapiti Island and Paraparaumu. In addition, there are some potential flows yet to be explored within the Allen Strait in the Marlborough Sound.

The nature of the scale of the New Zealand landmass does, however, result in the M2 tide being almost 180 degrees out of phase at either end of the Cook Strait, generating some very substantial flows (see Figure 2.5.2). Substantial flows are also found at Cape Reinga, at the tip of the North Island, and in Foveaux Strait, at the southern tip of the South Island.



Figure 2.5.2 - Modelled tidal amplitudes around New Zealand (Walters and Plew unpublished model results).

Tide gauges can be used to measure the height of the tide every few minutes. However, not all places have gauges, so computer models have been developed to compute tidal constituents for all coastal locations. Comparison between these modelled data and observations has enabled some degree of confidence to be placed in these results at the graphical levels of resolution displayed in Figure 2.5.3. The EnergyScape Project bases its conclusions relating to tidal resource upon tidal modelling using “Tide2D”, a tide-specific computer model. This is run by the NIWA and facets are described in Walters (1992 and 2005) and Walters et al. (2001). The numerical model uses a finite element approximation in space and a harmonic approximation in time [Walters (1992)]. The variable spatial resolution enables better approximation of complicated shoreline geometry and bottom topography, and the harmonic representation is ideally suited for combinations of periodic motions such as tides. The model has been used to simulate tides at a number of places around the world: the New Zealand Exclusive Economic Zone (EEZ) [Walters et al (2001), Stanton et al (2001)], the English Channel and southern North Sea [Walters (1987)], the West coast of Canada [Foreman and Walters (1990), Foreman et al (1993), Foreman et al (1995)] and the Delaware Bay [Walters (1997)]. All of these have been compared with extensive suites of observations, particularly those from Canada and New Zealand. The model generates depth-averaged flows.



Figure 2.5.3 - Average tidal speed for Cook Strait from the Tide2D model, as generated for the EnergyScape Project.

Average speed (m/s)



It should be pointed out that there is an important distinction to be made between tidal height and tidal currents. Tidal height behaviour is a relatively well understood area of study, relating to bathymetry and celestial forcing effects, and this allows reliable tidal height forecasts to be made. This is not the case for tidal flow, which is the characteristic component of the tide that is actually used for power generation. Tidal current meter records were analysed to give a large-scale overview of tidal flows around New Zealand [Stanton et al (2001)], as shown in Figure 2.5.4. This figure also compares the observations with modelled results, indicating fair agreement between the two. However, it must be noted that “tidal ellipses” do not convey information on “non-tidal” flow components, which can also be exploited by a tidal-energy conversion device to generate power.

Figure 2.5.4 - Observationally-derived M2 tidal ellipses compared with model results (Key: Blue ellipses = observed tides; Red ellipses = modelled tides)

(It needs to be kept in mind that these ellipses represent the flow that varies at the tidal frequency. It does not represent the residual flow nor does it represent flows generated by the M2 tide that create flows at other

frequencies)

Source: Stanton et al. (2001)

In order to provide an EEZ-wide picture of tidal flows, a number of smaller influencing factors and processes have, initially, been ignored. Consequently, the modelling does not account for the effect of stratification and internal tides, nor for oceanic or wind-driven currents or shedding of headland-eddies. Additionally, it does not model the bathymetry down to the device-scale, which can



generate substantial, but highly localised, flow disturbances. Consequently, the present EnergyScape work is a broad assessment, and assessment of individual device locations requires a finer scale of modelling and observation. As it stands, this broad assessment of New Zealand’s tidal energy resource is mapped in Figure 2.5.5, below:

Figure 2.5.5 – Marine (tidal) potential energy resource




Tidal flows are intrinsically variable. Consequently, their utilisation for power generation must be considered in tandem with energy storage and complimentary power supply. Furthermore, tidal energy is often erroneously promoted as being perfectly predictable for millennia to come (at least until the solar system changes its present dynamic configuration). However, this neglects the fact that tidal energy-conversion devices generate their power from the localised tidal flow patterns within larger-scale tidal systems. There are two facets to this:

• First: even with a perfectly regular background flow, eddy currents generated along the coasts are non-linear and somewhat unpredictable in their creation, propagation and development (as displayed in Figure 2.5.6).

• Second: regional-scale ocean currents can be substantial contributors to total tidal currents. For example, the Cook Strait has the effect of concentrating regional circulation currents, resulting in substantial flows that, although non-tidal, are very significant tidal energy resources.

Figure 2.5.6 - Modelling of coast-induced variability in the Cook Strait using spatio-temporally adaptive meshes

(The colours show the strength of the vorticity (eddying), whilst the scale of the adaptive mesh is also shown)

Source: Popinet and Rickard (2007)



Figure 2.5.7 - Comparison of (top) tidal constituent model and (bottom) current meter mooring data from Cook Strait, South of Wellington, during April 2006.

As an illustration of this complexity, Figure 2.5.7 shows tidal model output in comparison to current meter data from a mooring in Cook Strait. From an oceanographic perspective, this is a reasonable comparison as the model clearly captures the correct phase to the modulation and the amplitude is not dissimilar. However, clearly, there are some slow-moving variations not captured in the model, including actual non-reversal in flow. This last feature is well-described in marine charts derived from many years of observations by surveyors and mariners and is, again, a result of (amongst others) the shedding of eddy currents inside the local region (Charts can be found under: LINZ NZ46 www.linz.govt.nz).



Figure 2.5.8 – Cycles-per-day (CPD) power density spectra (psd) from 3 current meters in Cook Strait along with the pressure spectrum from one of the devices.

(The pressure spectrum is mainly driven by the mooring “blowing over”)

The spectral analysis, displayed in Figure 2.5.8, clearly shows the dominance of the semi-diurnal tidal pattern, defined by the major peak zone at 2 Cycles Per Day (CPD), but also shows that harmonics and a general background level of spectral activity exist. At low frequencies (towards the left-hand-end of the CPD-axis), this energy is associated with regional oceanographic variation in currents. At higher frequencies (towards the right-hand-end of the CPD-axis), the energy is related to the coastal boundary-layer.

Furthermore, in the present resource assessment, there is also something of a focus on a two-dimensional picture of flow. For example, the bathymetry of Cook Strait is highly three-dimensional, where ridges can rapidly shoal from 300 m to less than 50 m. Direct observations made using an Acoustic Doppler Current Profiler (ADCP), mounted in the hull of the Research Vessel Tangaroa, show the influence and extent of some of this bathymetrically-driven variation in flow in Figure 2.5.9 (Note that tides vary during this transect). There will always be a boundary-layer effect whereby the sea-bed serves to retard nearby flow, and Figure 2.5.9 shows that this is not always apparent and hard to distinguish from the effect of changes in bed depth.



Figure 2.5.9 - ADCP current magnitude during a 7 hour repeated transect along the Wellington south coast.

(The black region is the sea bed and the red regions mark the high flows at the time, which reached 2.5 ms-1)

Another issue is that of bi-directionality in tidal flow, which is better dealt with by most of the horizontal-axis turbine devices for power generation. A tidal ellipse analysis of suitable locations for deploying such devices, as indicated in Figure 2.5.4, would certainly highlight those locations with the strongest bi-directional flows. However, this type of analysis filters out the non-tidal-frequency flows. Consequently, if a tidally-generated eddy spins off a headland at the start of a particular phase of a tide and passes through the observation point over, say, a 20 minute period, it will not appear in the tidal filtering, but it may significantly affect the operation of the turbine.


It is claimed that only regions where spring tides drive flows exceeding around 2.5 m/s are viable as tidal energy resources. This must be treated with caution, because, almost all of the time, tidal flows will be less than the spring tidal flow, meaning that energy-conversion devices will be operating at lower tidal speeds for most of the time. In addition, the maximum spring tide is not a perfect proxy for total energy, as different locations have different tidal components. New Zealand has strongly semi-diurnal tides so that, typically, there are two tides a day of nearly equal magnitude. Some regions, however, sustain a stronger daily tidal signal so that one of the tides during the day is substantially smaller than the other, as depicted in Figure 2.5.10. Beyond this, the actual spring / neap cycle varies from place to place, with some areas having neap tides that are less than half the spring tidal amplitude and others where the spring / neap cycle is barely discernable.

Transect-1 Transect-2



Figure 2.5.10 - Tidal elevation snapshots (Top: a coastal site in British Columbia, Canada showing the strong daily (diurnal) tide)

(Bottom: a two-day record from Golden Bay, New Zealand, where the tide is almost totally semi-diurnal)

Source: Stevens et al. (2003)

Source: Plew et al (2006)

The nameplate ratings of many tidal energy-conversion devices appear to be associated with this 2.3-2.5 m/s flow rate, and each device will have a critical tidal flow speed – the cut-in speed – above which it will begin to generate a power output. A typical value for the cut-in speed is usually around 0.5-0.7 m/s [EPRI (2005)]. Figure 2.5.11 illustrates how the average, potential, tidal energy available within a flow stream around a typical energy-conversion device might vary depending on the ratio of tidal components and the rated cut-in speed. Clearly, the ratio (1 = totally semi-diurnal / 0 = totally diurnal) of the two tidal components has a significant influence over the potential resource available to the device (note that this approximate analysis is for a 24 hour snapshot and doesn’t include spring / neap variations). The rated cut-in speed influences the potential, tidal energy that may be available for extraction by the device more strongly at lower tidal component ratios. This is due to the average tidal speeds reducing to a value closer to the cut-in speeds, and, therefore, the actual tidal speeds cycling below the cut-in speed more often under these tidal conditions.



Figure 2.5.11 - Influence of semi-diurnal / diurnal tide ratio and cut-in speed on the potential tidal-energy resource available to a typical tidal-energy conversion device over a 24 hour

period (Contours display the average, potential tidal energy resource available for extraction, relative to a peak

potential resource for a tidal speed of 1 m/s amplitude)

An additional caveat to be borne in mind when considering the installation of a multi-device array, or farm, of tidal-energy conversion devices is the effect they will impose upon the local tidal flow patterns. In the case of a tidal channel, e.g., the Kaipara Harbour entrance, an array of devices may add sufficient hydraulic friction to the channel as to alter the potential tidal energy available [Garrett and Cummins (2005)]. Similarly, in a more open situation, e.g., the Cook Strait, a substantial array of devices may deflect the local tidal flows and reduce potential tidal energy available.

With the above barriers and limitations in mind, quantifying the realisable tidal-energy resource for New Zealand in any meaningful way is complex. A report by the Sustainable Development Commission identifies three categories of resource quantification [SDC (2007)]. Following their lead, these categories are:

• Theoretical Resource - the energy contained in the entire tidal flow essentially defined as the time-average of

• Technical Resource - the amount of the Theoretical Resource that can, likely, be exploited using upcoming technology. This includes cut-in and cut-out speeds and array interaction effects etc.

• Practical Resource - the amount of the Technical Resource that can be exploited after consideration of external constraints (e.g. grid connections, environmental factors).

In Table 2.5.12, below, an estimated, hybridised Theoretical / Technical Resource list is provided for preferred tidal-energy installations around New Zealand. This hybridised resource takes into account the effect of array interactions on the Theoretical Resource, but does not apply further device-specific limitations to the resource. Each of the locations’ resources estimates were based on

( )A u35 .0 ρ



transects taken across representative flow locations, and the complete Technical Resource can be estimated as a fixed percentage (10%) of the hybrid resource value (based on various arguments from Bryden and Melville (2004)). The Practical Resource assessment cannot be assessed until realistic developments of the tidal-energy conversion device technology have been made. Thus, Table 2.5.12 suggests that around 20 GW of tidal power is available from hybrid “Theoretical / Technical Resources” and that around 2 GW of power is plausibly available from the “Technical Resource”. The majority of this power is associated with Cook Strait and this is around 4 times the output of the Clyde Power station on the Clutha River.

Table 2.5.12 - Estimated tidal stream resources

Location Maximum spring-tide

speed

Depth Width Theoretical / Technical Resource

Technical Resource

unit m/s m km MW MW Cook Strait 2.5 250 21 18000 1800 Foveaux Strait 1.8 35 22 980 98 Cape Reinga 1.2 80. 10. 300 30 Kaipara 3.0 30 3 220 22 Colville Channel 1.0 50 15 160 16 Manukau 2.5 20 1.5 100 10 Tory Channel 2.5 50 0.5 85 8.5 French Pass 4.0 20 0.1 28 2.8 Total resource 19873 1987.3

Bluff Harbour was not included within this table as it was considered to be too small in total resource. However, Vennell and Beatson (2006) indicated peak tidal speeds of 1.6 m/s, and direct observation suggested that 250 kW of tidal power might be available for any given turbine [Jull (2007)].

Applying the above methodology to the potential tidal-energy resource map for New Zealand generates the “Realisable Tidal Power” map presented in Figure 2.5.13, below:



Figure 2.5.13 - Marine (tidal) realisable energy resource




As has been noted in the above sections, the tidal-energy conversion device industry is still within its embryonic stages of development and statements regarding device behaviours, efficiencies and efficacies are, in most cases, purely speculative. However, based on the criterion that they are undergoing, or nearing, sea trials of a significant scale, some of the front-runners are described in the following sections. Appendix A provides a more extensive list of links to less developed devices and approaches to tidal-energy extraction.

2.5.5.1 Tidal barrage technology

Whilst “marine-tide” generation is a relatively new concept, it must be noted that “tidal barrage” installations have been in operation for decades (e.g. La Rance, France). Furthermore, new developments of the tidal barrage technology (e.g. Severn Estuary, UK) are presently under serious consideration [SDC (2007)]. It is the opinion of the authors that these large developments, which disrupt estuarine flows substantially, are unlikely to become economically or environmentally viable in New Zealand, despite there being a number of moderately reasonable resource options.

2.5.5.2 Marine current turbines

MCT has the highest profile in the media, with respect to full-scale, prototype testing. It is poised to install its SeaGen device in Strangford Loch. The development has seen delays caused by the scarcity of support vessels, which is as a result of buoyant offshore gas / oil industry activity (www.marineturbines.com). The device is expected to produce 2 MW of electrical power from a dual-rotor configuration. This builds on their 300 kW SeaFlow trial device that was deployed in Devon, UK (Figure 2.5.14).

Figure 2.5.14 - SeaFlow turbine deployed by Marine Current Turbines off the Devon coast

Source: www.maritimetidal.com



2.5.5.3 OpenHydro

A device built by OpenHydro (Figure 2.5.15) is the first to be deployed at the European Marine Energy Centre. There is no explicit power generating capacity information available, although a device rating of 750 kW has been implied by Crest Energy, New Zealand7.

Figure 2.5.15 - The OpenHydro turbine installed at the EMEC

Source: www.openhydro.com

2.5.5.4 Kobold vertical axis turbine

This Italian vertical axis design has, apparently, been deployed in the Straits of Messina since 2001 [Calcagno et al. (2006)]. It has been demonstrated to produce in the order of 25 kW, but their proposed deployments extend up to 220 kW [EPRI (2005)].

2.5.5.5 Verdant East River

Prototypes of these smaller devices (35 kW) (Figure 2.5.16) have been deployed in the East River, New York. Despite this small capacity rating, the project claims a number of “firsts”, including:

• First kinetic-hydropower technology to deliver electricity to end-use customers,

• First fully bi-directional tidal operation,

• Most hours of continual operation and energy delivered of any kinetic-hydropower technology.

However, the deployments appear to suffer from mechanical blade fracture issues (http://www.nytimes.com/2007/08/13/nyregion/13power.html). Strong currents have sheared the tips off blades, and replacement blades made from aluminium are being investigated.

7 www.all-energy.co.uk/UserFiles/File/2007JamesIves.pdf



Figure 2.5.16 - Turbine being installed into East River

Source: http://www.verdantpower.com/gallery2

2.5.5.6 Aquanator Western Port

Atlantis Resources is developing a range of converters rated as micro-hydro (1-10 kW), mini-hydro (10–1000 kW) and small-hydro (1-10 MW). They operate as a sequence of sails turning a belt, which is a significantly different approach in comparison to most other technologies that have undergone reasonable development.


The principle asset associated with the New Zealand tidal-energy resource will, most likely, be comprised of a select range of tidal-energy conversion devices, possibly integrated into large arrays or farms, and associated mooring and electrical power transmission and distribution infrastructures. Accurate characterisation of these assets will be determined by the progress and successes of the various commercial industries with interests in pushing the development of specific tidal-energy conversion devices. As yet, little more than speculative attempts at future asset characterisations can be obtained.

As the industry is still in within its research and development phase, the associated costs of operation are substantial, with individual device costs currently in the order of $4,000,000, and the cost-per-kWh of electricity generated being similar to that of diesel-based generation. In terms of operation and maintenance costs, a berth at the non-profit EMEC is set at, approximately, $400,000 per year.



2.5.6.1 Analogues of tidal-energy assets

The offshore wind-energy and the offshore oil and gas exploration industries may offer some guidance to the possible assets associated with a future tidal-energy industry (Figure 2.5.17). Similar equipment and costs are likely to be shared between the industries in terms of the installation, maintenance and port operation infrastructures used. Tidal-energy assets, however, will be based in marine environments with stronger tidal flow conditions than experienced by the other two industries, and this is likely to reduce the windows of opportunity available for installation and maintenance operations.

Figure 2.5.17 - Infrastructure for installation of offshore wind turbines

Source: www.a2sea.com

2.5.6.2 Current status

Currently, there are no marine tidal-energy generators in New Zealand, although the recent announcement of the Marine Energy Deployment Fund (MEDF8), administered by the EECA, has inspired a lot of interest from private individuals and established power companies. At the time of writing, NIWA was fielding around 1 serious enquiry every 2 weeks regarding the fund. Some examples of the more refined proposals for New Zealand-based tidal-energy farm deployments are provided below.

2.5.6.2.1. Crest Energy - Kaipara

This group have obtained consent for a staged deployment of multiple 750 kW turbines based on the OpenHydro devices. They have constructed a very informative web site (www.crest-energy.com), and address the effect of shifting submarine dunes on the power cables. However, they appear to ignore the effect of the turbines reducing tidal flow and altering the scour region that

8 http://www.beehive.govt.nz/node/28658



the turbines sit in. Their present proposal identifies a staged development extending to 200 MW of generating capacity at full development and this has received funding from the MEDF.

2.5.6.2.2. Neptune Power - Cook Strait

A buoyant, horizontal-axis, turbine concept has been given consent for coastal water testing off Sinclair Head. Neptune Power’s press release claims a 17 m diameter rotor design, although their resource consent identifies a different design, and has claimed that devices would operate at around 1MW. A significant issue with this design of device is the effect that short-term eddies may have on the turbine’s “wing”, giving rise to directional stability issues (Figure 2.5.18). Their present proposal identifies deployment of only a single device [MED (2007)].

Figure 2.5.18 Artists impression of Cook Strait turbine

Source: www.stuff.co.nz/thepress/4220778a6430.html



2.5.6.3 Theoretical asset characterisation

Based on limited information available from the above examples, predominant characteristics of these tidal-energy farm concepts have been used to define a range of “generic” device parameters and costs. These figures are, essentially, guess work and draw heavily on the known information that; large operational vessel costs are around $50,000 per day, EMEC charges, approximately, $400,000 per year in berth rental and that large-scale, tidal-energy conversion devices are likely to reduce in unit cost from, approximately, $4,000,000 to $2,000,000 once a suitable production rate turnover has been established. A range of theoretical, generic devices, labelled “A” to “D”, are, thus, described as follows:

Device A is a large, monopole construction, appearing like a stubby-bladed wind-turbine. Installation costs will be large, because a monopole foundation structure needs to be installed. Maintenance will be relatively high, because operators have no choice about the removal of the device from the water for repairs. These devices can only be installed at a limited range of depths (i.e. deeper than their turbine-blade radius, but still within comfortable access for the surface maintenance vessels). Notably, the offshore wind-farm industry is now contemplating the installation of monopoles in water depths greater than 50 m.

Device B is based on the buoyant, tethered turbine device that is proposed to be used by Neptune Power for deployment in the, relatively deep, waters of Cook Strait. Installation should be less complicated than that of Device A, as the mooring for this device is of relatively simple design. Part of the attraction of this device is that maintenance can be achieved through mooring adjustments alone, which should allow for quicker maintenance operations times.

Device C is along the lines of the bi-directional device proposed by Crest Energy for the Kaipara entrance. A key point is that the mounting for the device is massive and has a substantial installation cost. Maintenance is relatively cheap, as this can be carried out by diver-based operations.

Device D is a novel, omni-directional device appearing like a water-wheel that lies on its side and floats on the surface of the water. This makes for simple deployment, recovery and maintenance, but makes it vulnerable to storm action.

The various properties of these theoretical devices are summarised, in Table 2.5.19 below, and have been used to assess the assets associated with a range of future, theoretical tidal-energy farm developments for New Zealand:



Table 2.5.19 - List of generic, hypothetical device descriptors

Description Comment Rating (MW)

Size (m)

(diam)

Depth (m)

Capital Cost ($M)

Maint. Cost

($M/y) A Monopole-mounted,

open-blade turbine. (e.g. MCT, Verdant)

Narrow depth range. Partly exposed to surface wave forces.

0.5 ~ 15 ~ 30 5 0.6

B Buoyant, counter-rotating blade turbine. (e.g. SMD)

Turbulence instabilities.

0.5 ~ 15 > 50 4 0.4

C Bed-mounted, ducted turbine. (e.g. Open Hydro)

Massive foundation mounting.

1 ~ 25 > 30 3 0.2

D Floating, vertical-axis. (e.g. Edin. Designs, Kobold)

Exposed to surface wave forces.

0.25 ~ 5 > 5 1 0.3

A large array of these tidal-turbines will be required by large-scale energy utilities for connection into the National electricity generation grid. Arbitrarily, a tidal-turbine “Farm Unit” is defined for this purpose and given a 20 MW capacity rating for a 2 × 2 km array footprint (this is around 10% of the capacity of the project “West Wind”, which includes up to 70 wind-energy turbines, spread along 20 km of ridge-line west of Wellington, and generates up to 210 MW of power).

Hence, this generic marine farm will require 40 units of Device A or Device B, requiring that each unit has an individual footprint area of = (2×10³)²/40 = 1×105 m² (e.g. each unit sits in the centre of a grid with sides of 316 m each). In determining which of the devices is more suitable for deployment at this level of unit spacing density, the down-stream turbulence characteristics and operational “safety zone” for access around each turbine will need to be understood in more detail.

Only 20 units of Device C are required for the theoretical marine farm array, but this assumes the farm is located somewhere with sufficient uni-axial tidal-flow patterns. These flow patterns are, generally, only found in narrow channels and straits, which will impose restrictions on the arrangement of the devices within the array.

If Device D is used to build the marine farm array, 80 units will be required and each will be positioned within a sea-surface grid of 220 m per side.



2.5.7 Future research

With the industry so embryonic, it is almost impossible to predict the future for it. The fundamental issue will be the continued need for low-carbon energy solutions. In concert with this is the need to move from a mind set of “keeping up with a growing energy demand” to limiting that demand. Developments in electricity storage are vital for widespread uptake of intermittent tidal-energy power generation. From a New Zealand perspective, extension of the existing electricity distribution network to some locations with favourable tidal flows will also aid in uptake.

Table 2.5.20 – Research status (Clear indicates ‘Fair knowledge’. Amber indicates ‘Could improve’. Green highlight indicates ‘Potential

opportunity’. Red indicates ‘Knowledge gap exists’)

International New Zealand Comment National resource understanding

Developing Advancing. NIWA, MetOcean Solutions, CAE, EECA

NZ is just starting to make headway in this field.

Site-specific resource understanding

Advancing. NIWA, ASR, MetOcean Solutions

Uptake is increasing. Several limiting factors identified by EECA.

Device scale turbulence Marine organism interaction

Device array interactions Immature Immature. NIWA

Experience will be gained from aquaculture industry.

Mooring devices Experience will be gained from offshore oil and gas industry.

Environmental impact Consulting engineers, NIWA

Commercial scale wave energy electricity generation

Immature None Internationally, lead-in tariffs are attracting developments

Switchgear / grid connection

Developing Marine Energy centres provide demonstration.

Over the next 10 year period, it should be envisioned that individual, and then small groups of, tidal-energy devices will become commonplace, providing for a variety of experiences, skills and infrastructures to be developed. Beyond this, a further 10 years of expansion could occur, in much the same way as the wind-energy sector is experiencing at this time. Beyond the next 20 year period, the vision would be for the industry to consolidate and for a number of large-scale developments to take place. At the same time, portable and remote “turn-key” energy solutions may also begin to become possible.

Towards these visions, specific research topics have already been identified as being necessary for assisting in the fledging of the tidal-energy power generation sector. These topics are as follows:



2.5.7.1 Device-scale turbulence and flow-structure interactions

Most devices are tested in regimes with only moderate background turbulence, but real-world tidal streams are highly turbulent. Once turbines are shown to work fundamentally, there will be further work to streamline their structure, whilst maintaining or improving their power generating capacity. This will test engineering limits, and two critical aspects need to be considered. The first is the vertical eddying that will be found in most tidal flow situations and which can be, partially, addressed in testing. However, wide straits, like Cook Strait, permit substantial horizontal eddying as well, so the degree of variability encountered by the turbine must be assessed using accurate flow-field measurement data. Secondly, it will be important to know how turbine blades and the local tidal flows interact. Computational work has taken place for some turbine designs, but mainly around blade behaviour in uniform background flow.

2.5.7.1.1. Device array interactions

Garrett and Cummins (2004) have shown that arrays of energy absorbers (tidal-energy conversion devices) will affect the total energy available within a given tidal flow stream. This interaction between tides and arrays happens at an interesting hydro-dynamic scale, as it sits on the boundary between oceanographic modelling and engineering Computational Fluid Dynamic (CFD) modelling. A combination of these models, like Gerris (gfs.sourceforge.net) and ROMS (www.myroms.org), are needed in order to understand how tidal currents are affected by the “porous” arrays of devices in tidal-energy farms in near-shore environments. To this end, the Foundation for Research, Science and Technology (FRST) has funded a three year programme to consider the usefulness of modelling for the understanding of array interactions with flow fields.

2.5.7.1.2. Marine mammal and fish interactions

Little is known about the interactions of larger fish and marine mammals with tidal-energy conversion devices – specifically turbine based varieties. Charismatic mega-fauna have a high-profile in the public perception and, while developers will predict tip speed and indicate that this is unlikely to harm animals, there is no evidence either way to suggest the fate of such animals. At present, any development will have difficulty in stating, with any confidence, that their hardware will not harm such species. This leaves any development open to a wide range of questions. These same issues are, however, being faced by aquaculture developers, and observational work, involving new approaches to monitoring, will begin the task of addressing these issues in the near-term. In the last year, NIWA9 has been actively studying the parameters that need to be considered for the environmental-impact assessment of marine energy technologies on mammals, benthic ecology and sedimentation, in order to improve the science in this area.

9 Chandler T; Torres L (2008). Overview and mitigation strategies of potential impacts on marine mammals caused by

marine energy facilities in New Zealand, NIWA Internal Report. Kregting L; Stevens C (2008). Marine energy influences on subtidal benthic communities, NIWA Internal Report. Broekhuizen, N. (2009). Electrical generation using marine energy: scope of impacts upon plankton? NIWA Draft

Report. MacCauley, G (2009). Marine energy and acoustics, Draft internal report in preparation.



Hydro-acoustic noise pollution has also been highlighted as a possible issue for marine animals living near a tidal-energy farm. Moving components and machinery associated with the energy conversion devices are likely to contribute to back-ground noise levels that may disturb aquatic species’ habits and habitats. Electro-magnetic noise, associated with on-board electrical generation equipment within the devices, should also be assessed for possible disturbance of marine “signalling” between certain aquatic species.

2.5.7.1.3. Moorings

Clearly, mooring design is crucial to the success and long-term economic viability of the tidal-energy device array. Shallow-water deployments are based on relatively well developed mono-pile technology, but deeper water developments are likely to employ the suspended, buoyant device technology. The moorings for these deep-water devices need to be studied in order to understand their stabilising requirements for maintaining turbine blade control under short-term tidal current variations.

2.5.8 Summary

The significant lack in our understanding of the marine-tidal energy resource for New Zealand, and, indeed, globally, stems from the difficulty involved in measuring and visualising the extent and pattern of the resource. With time and with dedicated mapping activities, we will understand its full complexity and potential. In the mean time, we must draw optimism from the fact that, for many years now, we have battled with marine environments in order to establish off-shore oil and gas infrastructures, off-shore wind turbine farms and, more recently, off-shore wave-energy farms. With no argument to suggest otherwise, we may expect the tidal-energy industry to follow the same speed and scale of development as seen in the wave-energy and off-shore, wind-energy sectors. A time-lag of 20-years may be the appropriate period of time observed between the initial stages of development for these three renewable energy resource sectors.


REFERENCES

References


2 – RENEWABLE RESOURCES References

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Carbon Trust (2006) Future Marine Energy, UK Government. http://www.carbontrust.co.uk/Publications/ publicationdetail.htm?productid=CTC601

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Kinsman, B. (1965). Wind waves. Prentice Hall Inc., Englewood Cliffs, New Jersey.

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Calcagno, G. F. Salvatore, L. Greco, (1) A. Moroso, H. Eriksson, (2006) - Experimental and Numerical investigation of an Innovative Technology for Marine Currents Exploitation: the Kobold Turbine, XVI Offshore and Polar Engineering Conference - San Francisco (USA). http://www.pontediarchimede.it/shared_uploads/Download/13_DOCUMENTO.pdf

EPRI (2005). Survey and characterisation: tidal in stream energy conversion devices http://www.epri.com/oceanenergy/attachments/streamenergy/reports/004TISECDeviceReportFinal111005.pdf. (Bedard et al. authors)

Foreman, M.G.G.; Walters, R.A. (1990). A finite element tidal model for the southwest coast of Vancouver Island, Atmosphere-Ocean 28: 261-287.

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Plew DR; RH Spigel, CL Stevens, RI Nokes, and MJ Davidson. (2006). Stratified flow interactions with a suspended canopy, Environ. Fluid Mech. 6: 519-539. http://www.springerlink.com/content/j081551w2114j585/

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Appendices


2 – RENEWABLE RESOURCES Appendices

APPENDIX A – LIST OF MARINE (TIDAL) TECHNOLOGIES

Since marine (tidal) energy capture is a rapidly evolving field, by definition, this list of marine (tidal) technologies will quickly become obsolete:

Marine Current Turbines - A pair of turbines (total =~ 1 MW) mounted on a mono-pile; poised to have a test deployment in Strangford Narrows Nth. Ireland. http://www.marineturbines.com

SMD Hydrovision TidEl - A pair of contra-rotating turbines (total =~ 1 MW) mounted on a buoyant wing allowing moored deployment and maintenance. This design was that initially favoured by Neptune Power for use in Cook Strait. http://www.smdhydrovision.com/products/?id=27

Lunar Energy bidirectional blades – 1-2 MW ducted turbine fixed to seabed on a massive concrete foundation. It is large, 30×30×30m. Simple in operation relying on relative axisymmetrical tidal flows. Proposed deployment at EMEC in the next y12-24 mo. Originally considered for Kaipara development. http://www.lunarenergy.co.uk/

Enermar Kobold – 400 kW device – deployed in Straits of Messina. www.pontediarchimede.com/language_us/progetti_det.mvd?RECID=2&CAT=002&SUBCAT=&MODULO=Progetti_ENG&returnpages=&page_pd=d

Edinburgh Designs Variable Pitch Foil vertical axis turbine broadly similar to Kobold device but variable pitch – their www site has no tidal content however their report is available at http://www.berr.gov.uk/files/file30557.pdf

BioPower Systems Oscillating hydrofoil with proposed capacity at the 500 kW and upwards level. http://www.biopowersystems.com/biostream.html

Verdant - 25-100 kW pile-mounted turbine http://www.verdantpower.com/what-systemsint

EXIM Seapower Savonius floating device - small 44 kW device

Aquanator – Atlantis Energy - hydrofoil rotor technology in 1MW range with planned deployment of Western Ports in Victoria http://www.atlantisresourcescorporation.com/pages/applications.htm


2 – RENEWABLE RESOURCES Appendices

OpenHydro – a hybrid between MCT and Lunar approaches with a closed disk for blades mounted between twin-monopiles, it is presently being trialled at EMEC. http://www.openhydro.com/techInstall.html

MantaRay http://www.mantaray.biz/full.html

StarTider www.starfishelectronic.co.uk

Hammerfest StrØm AS www.e-tidevannsenergi.com

ScotRenewables SRTT www.scotrenewables.com

Atlantisstrom www.atlantisstrom.de

Tidal Sails www.tidalsails.no

Stingray and AWCG by Engineering Business. Substantial environmental impact work has been conducted: www.engb.com/

Seasnail by Robert Gordon University and AREG at: www.rgu.ac.uk/cree/general/page.cfm?pge=10645

Tidal Fence by Blue Energy at: www.bluenergy.com

Polo by Edinburgh University at: www.mech.ed.ac.uk/research/

Rochester / Gentec Venturi by Rvco Ltd at: www.rvcogen.com

Underwater kite by Abacus Controls at: uekus.com/

Gorlov Turbine by GCK Technology at: www.gcktechnology.com


Glossary


2 – RENEWABLE RESOURCES Glossary

GLOSSARY OF COMMON TERMS ~ Approximately Afforestation To convert land into a forest by planting trees or their seeds. ADCP Acoustic Doppler Current Profiler – a measuring device that can be used

for determining marine current flow speeds. Assets A physical item (or group of items) of infrastructure the either extract,

convert or distribute energy e.g. wind farm, coal mine, electricity network.

AU Ammonia Urea Bar.g Barometric gauge pressure – the pressure of a gas registered by a

measurement gauge device, relative to the ambient pressure. Bounded map Land areas where activity is consider to be of low likelihood due to

existing planning logistics e.g. Road in a National Park. Bbl “Esso” blue barrel – 42 US gallons, the international volumetric unit of

oil. Bpd Barrels per day BRANZ Building Research Association of New Zealand - an independent

consulting and information company providing resources for the building industry.

BTL Biomass to liquids CAPEX Capital expenditure CSS Carbon Storage and Sequestration – The process of capturing

greenhouse gas emissions can storing them for several hundreds of years

CCS Carbon Capture and Storage (or Sequestration) CCT Carbon Capture and Trade CGH2 Compressed Gaseous Hydrogen CHP Combined Heat and Power. Electricity (power) production alone

generates a lot of waste heat and is therefore doesn’t recover maximum value from fuel. Heat generation achieves a fuel to energy output ratio, but doesn’t produce high value electricity. A CHP operation combines the advantages of both.

CNG Compressed Natural Gas CO2 Carbon Dioxide CO2EQV A common measure for greenhouse gas warming potential. This unit

aggregates the emissions from CO2, CH4, SF6, N2Ox, HCF & PCF to Carbon Dioxide Equivalent.

CPI Consumer Price Index CTL Coal to liquids DME Di-methyl Ether DoC Department of Conservation DSM Demand Side Management E3 A database used to assess Energy use, Economics and Emissions for

processes EDF Energy Data File – Annual summary of New Zealand’s energy demand.

Maintained by MED. EECA Energy Efficiency and Conservation Authority EERA Energy Efficiency Resource Assessment EEUD Energy End-Use Database – Maintained by EECA EEZ Exclusive Economic Zone EPRI Electric Power Research Institute EROEI Energy Return on Energy Invested EROFEI Energy Return on Fossil Energy Invested EtOH Ethanol



F-T Fischer-Tropsch process. A technology developed in Germany (1920s) which uses catalytic reactions to synthesise complex hydrocarbons from synthesis gas (carbon monoxide and hydrogen).

FC Fuel Cell FCV Fuel Cell Vehicle Firm capacity A baseline (minimum) generation capacity that can be maintained on an

inter-annual basis (e.g. dry year capacity of hydro power station). FPSO Floating Production, Storage and Offloading – a ship-based facility that

accompanies off-shore oil & gas drilling platform operations. FRST Foundation for Research, Science & Technology FTE Full-Time Equivalent – the equivalent number of people employed in

full-time positions within an industrial sector. GBS Gravity-Base Structure – a heavy-duty, off-shore, oil storage facility

that is used to assist in off-shore oil drilling operations. GDP Gross Domestic Product GHG Greenhouse Gas – Emissions that add to radiative warming of earth eg.

CO2, CH4, SF6, PFC, HFC. GIS Geographical Information System GJ Giga-Joule = 1,000,000,000 Joules = 109 Joules of energy GTL Gas to liquids GWP GHG warming potential HRAP High Rate Algal Pond – a type of waste-water treatment pond HEEP Heat Energy Efficiency Program HERA Heavy Engineering Research Association ICDP International Continental Drilling Programme – towards the study of the

Earth’s crust, natural mineral resources and interactions with surface ecological systems.

ICE Internal Combustion Engine ICEV Internal Combustion Engine Vehicle IGCC Integrated Gasification Combined Cycle In-gate All off-road transportation i.e. agriculture, forestry, mining, recreational

and off-road vehicles. IPCC International Panel on Climate Change Kt kilo-tonne – equivalent to a million kilograms or a Giga-gram. L/100 km Litres per 100 km – a measure of fuel consumption used for road

transport vehicles lde Litre of Diesel equivalent – a unit of measure for comparing the energy

content of alternative fuels with that of a litre of conventional Diesel fuel.

LEAP Energy pathway visualisation software – Long-range Energy Alternatives Planning.

LEAP framework The database, output files and visualisation tools that are associated with running LEAP.

lge Litre of gasoline equivalent – a unit of measure for comparing the energy content of alternative fuels with that of a litre of conventional gasoline (“petrol”) fuel.

LNG Liquefied Natural Gas (mainly methane @ -160˚C) LPG Liquefied Petroleum Gas (mainly propane and butane) mcfd thousands of cubic foot per day MED Ministry of Economic Development MEDF Marine Energy Deployment Fund – administered by the EECA MeOH Methanol MEPS Minimum Energy Performance Standard MJ Mega-Joule = 1,000,000 Joules = 106 Joules of energy



mbbls Thousand barrels – non-SI unit of volumetric measurement of oil mmbbls Million barrels – non-SI unit of volumetric measurement of oil

(1mmbbl of crude oil contains approximately 6 PJ of energy) MOT Ministry of Transport mmscf millions of standard cubic feet MT Magneto-Tellurics – a technique used for mapping sub-surface rock

features, relating to their natural, electrical conductivity. Mt-km/ktequivalent Mega-tonne-kilometre travelled per kilo-tonne(equivalent) of various

industrial stock moved. MTG Methanol-to-Gasoline plant MW Mega-Watt = million Watts – measurement of power output NA & AN Nitric Acid and Ammonium nitrate NGL Natural Gas Liquids NZ New Zealand / Aeotearoa NZBCSD New Zealand Business Council for Sustainable development NZES New Zealand Energy Strategy NZEECS New Zealand Energy Efficiency and Conservation Strategy O & G Oil and Gas OPEX Operational Expenditure OWC Oscillating Water Column – a form of wave energy conversion

technology for marine applications. Peak Oil Defined as the maximum production (bpd) of a field, a province, or the

world Phase The stage of development of an asset – eg. Research, Construction,

Operating. PHEV Plug-in Hybrid Electric Vehicle PJ Peta-Joule = 1015 Joules = thousand, million, million Joules –

measurement of energy. PKT Passenger Kilometres Travelled – used in the quantification of personal

transportation Risk score An indication of the likelihood that a phase of asset development will

fail (0 – Minimal to no risk; 5 – Extreme to almost total risk). When risk probabilities are applied to applied to Policy, research & financing costs an implementation risk ($000s) is calculated. When risk probabilities are applied to applied to operating capacity, an operational risk (MW) is calculated.

RMA Resources Management Act RON Research Octane Number – a measure of the quality of a fuel,

commonly seen at transport fuel filling stations to indicate the relative octane rating of petrol.

PWD Public Works Directive PV Photo-Voltaic – relating to the conversion of solar energy, carried by

photons, directly into electrical energy (via photo-voltaic cells that are built into panels or arrays).

RVP Reid Vapour Pressure (The propensity of “light ends” to evaporate from crude oil).

SHW Solar Hot Water SI le Systeme International d’unites – the international system for defining

common units of measurement. SMR Steam Methane Reformation SRF Short Rotation Forest StatsNZ Statistics New Zealand SUV Sports-Utility Vehicle Sweet gas Well gas with low sulphur content (<4ppm H2S), as distinct from sour

or “dirty”



TJ Tera-Joule = 1012 Joules of energy TE Thermo-Electric – relating to the conversion of thermal radiation

directly into electricity (via thermo-electric cells that are built into panels and arrays).

t-km Tonne-kilomteres - used in the quantification of goods transportation Tm3 Tera-cubic metres – used as an SI alternative to “trillions of cubic feet”

for measurement of natural gas reserves tph Tonnes per hour TW Tera-Watt = million-million Watts – measurement of large power

output US United States of America USDoE United States Department of Energy VFM Vehicle Fleet Model – developed by the Ministry of Transport VKT Vehicle Kilometres Travelled – Generally associated wth passenger

transportation. WGIP Wind Generation Investigation Project – set up by the Electricity

Commission WEC Wave Energy Converters WSP Waste Stabilisation Pond – for waste-waster treatment

new zealand’s energyscape - niwa · ener gysc a pe december 2008 energyscape asset review...

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