i

PARTNERSHIP TO ADVANCE CLEAN ENERGY DEPLOYMENT (PACE-D)

ii

Technical Assistance Program

NTPC Solar Wind Hybrid at

Kudgi

Approach for Measurement and Metering

of Wind-solar Hybrids

iii

TABLE OF CONTENTS

Figures and Tables ______________________________________________________________ iv

Acronyms______________________________________________________________________ v

Executive Summary ____________________________________________________________ vii

About This Document ____________________________________________________________ x

1 Introduction ________________________________________________________________ 1

1.1 Metering Levels In Independent Solar And Wind Projects _______________________ 1

2 Possible Placements of Tariff Meters in Wind-Solar Hybrid ___________________________ 3

2.1 Measurement at Interconnection Point (Levels 3 & 4) __________________________ 4

2.2 Metering At Generator Level (Level 2) ______________________________________ 7

2.3 At Wind Turbine Generator Or Solar Block Level (Level 1) ______________________ 7

3 Proposed Measurement and Metering Approach for Hybrid Plants _____________________ 9

4 Case Study: Metering For A Hybrid Project In Karanataka __________________________ 10

5 Loss Allocation Approaches __________________________________________________ 12

5.1 Loss Allocation to Power Generators in a Hybrid Project _______________________ 12

5.2 Loss Allocation To Wind And Solar Components _____________________________ 12

6 Policy Recommendations ____________________________________________________ 14

7 Conclusion________________________________________________________________ 15

Annexure 1 Existing Policies for Wind-solar Hybrid Projects _____________________________ 16

Annexure 2 Location of Renewable Energy Meter as per CEA regulation and RPO ___________ 18

iv

FIGURES AND TABLES

Figure 1 Different possible metering levels ...................................................................................... 4 Figure 2 Proposed metering approach for wind-solar hybrid project ............................................. 10 Figure 3 Case study: Metering at Kudgi project ............................................................................. 11 Figure 4 Location of Renewable Energy Meter .............................................................................. 18

Table 1 Example of metering levels for wind and solar projects ____________________________ 1 Table 2 Scenario wise proposed metering approaches __________________________________ 9

v

ACRONYMS

ABT Availability Based Tariff

AC Alternating Current

AEP Annual Energy Prediction

ALDC Area Load Dispatch Centre

APTRANSCO Andhra Pradesh Transmission Company

CEA Central Electricity Authority

CERC Central Electricity Authority

CUF Capacity Utilization Factor

DC Direct Current

Discom Distribution Company, delivering power to a consumer

DPR Detailed Project Report

EE Energy Efficiency

EVI Emergent Ventures India

F&S Forecasting and Scheduling

GETCO Gujarat Electricity Transmission Company

GOI Government of India

GW Giga Watt = 10^9 Watt; a unit of electric power

GWh Giga Watt Hour = 1 GW of power delivered for 1 hour.

HV High Voltage

INR Indian Rupee

kV Kilovolt or 1000 Volt.

kW Kilo Watt = 10^3 Watt; a unit of electric power

kWh Kilo Watt Hour = 1 kW of power delivered for 1 hour.

KERC Karnataka Electricity Regulatory Commission

KREDL Karnataka Renewable Energy Development Limited

MNRE Ministry of New and Renewable Energy

MOP Ministry of Power

MW Megawatt = 10^6 Watts; a unit of electric power

MWh Megawatt hour; a unit of electric energy, equivalent to 1 MW electric power delivered for 1 hour.

NIWE National Institute of Wind Energy

vi

NTPC National Thermal Power Corporation

OA Open Access

OEM Original Equipment Manufacturer

PACE-D Partnership to Advance Clean Energy Deployment

PE Plant Evacuation

PLF Plant Load Factor

PPA Power Purchase Agreement

PV Photovoltaic

RE Renewable Energy

REC Renewable Energy Certificates

RPO Renewable Purchase Obligations

SERC State Electricity Regulatory Commission

SLD Single Line Diagram

SLDC State Load Dispatch Centre

SNA State Nodal Agency

SS Substation

STU State Transmission Utility

Unit In informal description of electric energy consumed; equal to 1 kWh

USAID United States Agency for International Development

WTG Wind Turbine Generators

vii

Executive Summary

Background

India has an abundance of wind and solar energy resources. Successive governments

have recognized the benefits of renewable energy as key contributor and enabler to

India’s growth, and made developing these sectors a priority. A rich and diverse

ecosystem of wind and solar companies, enabled by mature regulations has resulted

in the creation of a vibrant market, buoyed by rapid investment in these sectors. As

wind and solar technologies scale to a significant fraction of India’s energy mix, it

becomes critical to take into account their footprint in the form of land use, and use of

power evacuation infrastructure, and seek avenues for increased utilization and

efficiency of common resources. While so far, the focus for both, solar as well as wind

projects have been on technology, project implementation and policy, a more

integrated approach is needed to develop the sectors in the future. Wind-Solar1 Hybrid

projects are a new and emerging concept globally, and offer an approach to make this

resource use optimization possible. Hybrids offer several benefits such as:

1. Increased generation per square meter area of land utilized

2. Savings from shared transmission costs

3. Savings from common generation infrastructure cost

4. Reduced operating costs due to shared services

5. Balanced power mix for sale

Recognizing their potential in helping scale up renewable energy, the Government of

India has set a target to install 10 GW of wind-solar hybrid power plants by 2022 as

per the draft National Wind-solar hybrid policy.2 The states of Gujarat and Andhra

Pradesh brought out draft policies for development of Wind-Solar Hybrids. Although

hybrid projects are simply an approach to co-locating wind and solar energy projects at

a single site, the combination of the two technologies on one site presents a certain

level of complexity, which must be addressed. Sites must be chosen in a manner to

optimize generation from both types of sources, and planning must be done while

taking into account specific needs of both, wind and solar generation. These general

issues have been discussed in detail in a separate publication.

One of the most complex issues affecting hybrids is the metering of power generation,

due to issues related to energy accounting and regulatory compliance. Each state has

specific procedures for metering of independent wind and solar projects. Because

these approaches have been developed with a single developer, technology, or small

1 Through this report, when reference is made to solar, it refers to solar photovoltaic (PV) technology.

2 http://mnre.gov.in/file-manager/UserFiles/Draft-Wind-Solar-Hybrid-Policy.pdf; For further details about

the existing policies refer Annexure 1

viii

plants in mind, current approaches do not directly apply to hybrid projects. New

approaches therefore must be developed for hybrid projects given their complexity.

The paper presents key considerations in developing the metering methodology for

measuring of hybrid power generation from wind-solar sites. The paper analyzes

present practices of metering of independent solar and wind projects and the issues

that arise if similar metering approach is adopted for wind-solar hybrid projects. This

paper also presents a case study of metering implemented for a hybrid wind-solar

project installation in Karnataka.

Problem statement

While regulatory and metering regimes for independent solar and wind projects are

well developed, several challenges arise when the two are combined and common

evacuation infrastructure is used. Wind and solar generation fall under separate

regulatory regimes, with separate quotas for renewable purchase obligation for end

users, and are priced differently in the energy markets. Typically, metering for power

generation takes place at the point of feeding into the main grid, at a transmission sub-

station. A hybrid project must ensure similar metering at the grid-injection stage. But in

addition, it must also deploy a second level of metering to capture generation at solar

or wind project level. Additional complexity emerges when multiple operators own one

or more solar or wind projects co-located within a single farm. Hybrid projects can

operate in a number of situations, which necessitate a new metering approach, e.g.

The buyers of wind and solar generation from the hybrid plant are different;

The tariffs of wind and solar generation from the hybrid plant are different;

The end buyer or developer needs to meet its RPO obligations, and needs to

account for purchase from individual sources separately;

The forecasting and scheduling (F&S) norms for wind and solar are different,

with differences in permissible error band and penalties imposed for deviations;

or

Transmission and wheeling charges are different for wind and solar power.

The situations listed above are just some examples of conditions where metering of

power hybrid plants becomes critical.

Proposed Solution

This paper outlines a feasible approach for independent metering of solar and wind

generation, even when they use common evacuation infrastructure. Renewable energy

farms are often spread across large areas, at locations that are far from the point of

interconnection with utility grid. Like other projects, hybrid projects utilize shared

evacuation infrastructure to inject power into the grid, and incur transmission losses

between the point of generation (block level) and the point of grid interconnection.

Accounting for power generation at each of these levels, and intermediate levels

between generation and grid feed is critical from the perspective of proper accounting

for purpose of sale and cost allocation.

ix

The paper recommends scenario based multilevel metering, which can be a

combination of the generator level (wind turbine generator and solar block), ownership

level, the plant level and grid level metering. The four levels can be described as

follows, and are depicted in the schematic presented in Figure 1.

Level 1 - Metering at generator block level: Design of blocks in a solar plant is done

based on technical considerations, and metering at this level allows the most granular

reporting of power generation. This level of metering is required when segregation of

wind and solar generation is necessary, and can help facilitate splitting of generation at

the project level for wind and solar technologies.

Level 2 - Metering at individual plants owned by different developers within a

farm: This approach to metering becomes necessary, if there are several plants

owned by different entities in a large wind-solar hybrid park or zone. This level of

metering can consist of one or more blocks in a plant located within a farm. Level 2

metering of net energy exported from each owner forms the basis for allocation of

proportionate energy loss attributable to shared evacuation infrastructure across

projects.

Level 3 - Metering at the wind-solar hybrid park or farm level: This level of

metering is at the farm level, and measures the total renewable energy generation

from all sources, including solar and wind generation in the entire hybrid farm.

Metering at this level is net of internal losses.

Level 4 - Metering at grid substation level: This level of metering is done at the

location where power is injected into the grid at a utility substation. Wind solar hybrid

farms may be situated at locations remote from the grid, and often require evacuation

infrastructure to access the grid. In addition to losses incorporated within metering at

level 3, this level of also reflects transmission losses between the point of generation

and the point of grid injection. Typically, metering at this level is critical from a financial

accounting perspective, as it typically forms the basis of compensation to power

generators.

Depending on state regulations regarding the interconnection point, level 3 or level 4

metering, at a minimum, is typically made mandatory for all projects. Additionally, it

would probably benefit hybrid projects to also require metering for generation by each

owner, necessitating metering at level 2 or in case even greater granularity is desired,

at the block level, or level 1.

x

ABOUT THIS DOCUMENT

This document has been prepared for the United States Agency for International

Development (USAID) Partnership to Advance Clean Energy Deployment (PACE-D)

Technical Assistance (TA) program.

This document is second in part of a series of publications drawing from the

experience of designing a wind-solar hybrid plant by National Thermal Power

Corporation (NTPC), in Kudgi, Karnataka. The first publication, ‘White Paper on

Design Approach for Wind-Solar Hybrids’ focuses on design aspects such as layout,

planning and policy aspects of hybrids. This publication focuses on the metering

aspects governing the measurement and accounting of energy generation from

projects. The paper has been prepared based on meetings with stakeholders,

including Original Equipment Manufacturers (OEMs) for wind power, Ministry of New

and Renewable Energy (MNRE), Regulators (CERC, SERC), Indian Wind Turbine

Manufacturers Association (IWTMA), The Energy and Resources Institute (TERI), and

CSTEP. Stakeholder comments and suggestions on the metering approach have been

taken into account and analyzed, and recommendations are offered for metering

approaches for wind-solar hybrid projects.

1

1 Introduction

Wind and solar PV are well established and mature technologies. At present, solar and

wind projects are installed on a standalone basis, under separately defined policies and

regulations. Accounting of energy generation is a critical aspect for any power project

and over the years, a robust policy framework has been developed for metering in the

context of both, solar as well as wind projects. Metering and grid interconnection points

are typically defined for each state by the respective State Electricity Regulatory

Commission (SERC). In turn, these are developed based on guideline regulations

specified by the Central Electricity Authority (CEA)3.

1.1 Metering Levels In Independent Solar And Wind Projects

In case of independent wind and solar projects, the widely accepted metering level is at

the interconnection point of the project with the grid. Some wind projects are also

allowed to meter the generation at wind turbine generator level, if they fall under the

cluster scheme. Metering level for a specific project is subjected to state policy and

acceptance by the distribution company. The table below describes the identified

metering points for solar and wind projects in different states.

Table 1 Example of metering levels for wind and solar projects

State Policy Metering level

Gujarat solar

power policy4

Electricity generated is metered on 15-

minute time block by STU/Discom/SLDC/

ALDC at the 11 kV system of Discom.

ABT-complaint meters must be installed

for purpose of energy accounting of solar

generating projects.

Interface metering shall conform to CEA

Regulation 2014.

STU/Discom shall stipulate specifications

Grid interconnection

point

Gujarat wind

power policy5

Metering point is at 66/132/220 kV

pooling sub-station located at the wind

farm site

Interconnection point shall be the point of

connection at the nearest GETCO sub-

Plant site (outgoing

feeder)

3 Please refer to Refer to annexure 2. For more detail, visit

http://www.cea.nic.in/reports/regulation/amend_15122014.pdf 4 https://geda.gujarat.gov.in/policy_files/gujarat_solar_power_policy_2015.pdf

5 https://geda.gujarat.gov.in/policy_files/Gujarat%20Wind%20Power%20Policy-2016.pdf

2

station.

ABT complaint meter must be installed for

purpose of energy accounting, as per

GERC order.

Interface metering shall conform to CEA

Regulation 2014.

GETCO stipulates specifications

The electricity generated from the WTGs,

shall be metered and readings taken.

Andhra

Pradesh Power

Evacuation

from Captive

Generation,

Cogeneration

and Renewable

Energy Source

Power Plants6

Energy accounting for projects connected

to EHT pooling substation shall be based

on metering at the HV bus bar side in the

pooling substation.

For single owner Solar/Wind Projects

connected through a 33 kV (11 kV) line

with a pooling bus of 33 kV (11 kV) at the

project, metering for energy accounting

shall be provided at the outgoing feeder

of pooling bus. If pooling bus is not

available, metering for energy accounting

shall be provided at incoming feeder of

the 33 kV (11kV) bus bar side of the grid

substation.

Multiple Solar/Wind project developers

having meters at HV (33 kV) side of

individual generator(s) with a pooling bus

at the project, common metering point for

energy accounting shall be provided at

the outgoing feeder of pooling bus. If

pooling bus is not available, the common

metering point for energy accounting shall

be provided at incoming feeder i.e, just

before the 33 kV bus bar side of the grid

substation.

Each Solar/Wind power project will have

two metering points, one at project’s

switchyard and another metering point is

common metering point.

At plant as well as grid

interconnection point

To understand the applicability of similar methodology to a wind-solar hybrid project, let

us consider a wind-solar hybrid project in state of Gujarat. If injected power is metered at

6 http://www.aperc.gov.in/aperc1/assets/uploads/files/8d9e9-power-evac_reg_-3of2017.pdf

3

the wind-solar hybrid farm level (as per the Gujarat wind power policy), segregation of

generation for each owner and further segregation into wind and solar generation is not

possible. Similar issues will arise, if metering is done at grid interconnection point (as per

the Gujarat solar power policy). This inability to segregate leads to challenges outlined in

the next section.

2 Possible Placements of Tariff Meters in Wind-Solar Hybrid

This section outlines the different possible designs for hybrid metering. The best design

of a hybrid plant metering is decided on the basis of requirements of the consumer, the

generator and the distribution utility. Levels 1-4 define the different level of metering

possible for any wind/solar project. These levels are depicted in Figure 1 below.

Level 1 - Metering at generator block level: Design of blocks in a solar plant is done

based on technical considerations, and metering at this level allows the most granular

reporting of power generation. This level of metering is required when segregation of

wind and solar generation is necessary, and can help facilitate splitting of generation for

wind and solar technologies. This can be useful for the purpose of accounting of power

generation.

Level 2 - Metering at individual plant(s) level: This approach to metering becomes

necessary, if there are several plants owned by different entities in a large wind-solar

hybrid park or zone. This level of metering can consist of one or more blocks in a plant

located within a farm. Level 2 metering of net energy exported from each owner forms

the basis for allocation of proportionate energy loss attributable to shared evacuation

infrastructure across projects, further downstream from the plant till the point of feeding

into the grid.

Level 3 - Metering at the wind-solar hybrid park or farm level: This level of metering

is at the farm level, where electricity from all the generators is pooled this metering

reflects the total renewable energy generation from all sources, including solar and wind,

in the entire hybrid farm. Metering at this level is net of internal losses. In States, such as

Gujarat this is the interconnection point from where the transmission grid picks the

electricity.

Level 4 - Metering at grid substation level: This level of metering is done at the

location where power is injected into the grid at a utility substation. Wind solar hybrid

farms may be situated at locations remote from the grid, and often require evacuation

infrastructure to access the grid. This level of metering reflects transmission losses

between the point of generation and the point of grid injection. Typically, metering at this

level is critical from a financial accounting perspective, as it forms the basis of

compensation to power generators. This is currently the most widely accepted metering

level for both wind and solar projects across states.

4

Figure 1 Different possible metering levels

The following section discusses key features and challenges associated with metering at

all possible levels, beginning at the highest level (levels 3 or 4), and going down to the

most granular level of metering (level 1). As we see in the sections below, the ideal

solution for metering is a combination of metering at two levels or more – as this

approach provides the greatest flexibility and accuracy in measurement of generation,

while at the same time facilitating proper accounting of internal losses, transmission

losses upstream of the point of grid interconnection, and for purposes of electricity sale.

2.1 Measurement at Interconnection Point (Levels 3 & 4)

At this level the total hybrid power generation in the farm is metered prior to the

interconnection point. According to existing state level policies metering is either allowed

at level 3 (farm level pooling), or at level 4 (grid sub-station). This is the minimum

metering required by the distribution company, as it is the basis upon which, the

accounting for power sale and purchase occurs. Whether level 3 or level 4 metering is

accepted, varies from state to state.

If metering is carried out only at level 3 or level 4 for a hybrid wind-solar project, it results

in certain specific challenges that do not affect generation from wind-only or solar-only

sites. The following challenges emerge, which must be addressed through the metering

framework.

5

There is no basis for the utility or project developers to segregate power

exported by generator/owner.

There is no basis for segregation of generated power into solar or wind

components, which results in attendant challenges when it comes to accounting

for RPOs, and other obligations, as discussed below.

Challenge Discussion

Inability to segregate power injected into the grid by each generator

In absence of generator level segregation, billing for power exported by each generator is not possible. In such a case, the hybrid plant will be built without any sharing of infrastructure, resulting in erosion of savings.

Inability to segregate power into wind and solar components

If the power injected can’t be segregated into wind and solar components this results in challenges relating to

Wind and solar RPO compliance

REC qualification

Determination of transmission and wheeling charges

Determination of forecasting and scheduling compliance

Determination of Tariff

Different fiscal incentives

Challenges associated with wind and solar RPO compliance

RPO for each obligated entity is defined for solar and non-solar categories. RPO is defined in terms of % of total energy consumed by the entity. Obligated companies will not be able to utilize power purchased from hybrid farms. E.g. in 2018-19, Indian Railways, an obligated entity, is required to meet 6.75% power from solar energy, and 10.25% electricity use from non-solar sources of generation.

REC qualifications RECs and can be bought by obligated entities to meet their RPO requirements. They are sold on two power exchanges active in India, and can command significant value, currently trading with a floor price of INR 1500/MWh for both solar and non-solar RECs. A wind-solar hybrid plant, if it is not selling power to meet its own RPO target, can sell RECs. However, it will not be able to qualify unless it is able to specify how much of the total power injected into the grid comes from solar and non-solar source.

Different Fiscal Incentives Fiscal benefits vary depending on the technology, e.g. wind generators used to get Generation Based Incentive under Feed in Tariff schemes, which are not available to solar projects. In case states offer differing benefits to wind or solar, segregation of output into wind and solar may be needed.

Transmission, Wheeling and Banking Charges

Energy bought by an Open Access (OA) customer is delivered using the discom’s transmission infrastructure, and attracts transmission, wheeling and banking charges. In addition, electricity duty is payable on the variable electricity cost paid by end buyers. Transmission, wheeling, banking and electricity duty provisions differ for wind and solar power and are state specific.

Forecasting and Scheduling The Grid Code defines Forecasting and Scheduling (F&S)

6

requirements for renewable energy generators and imposes penalty if deviation from a schedule is beyond a defined limit. The schedules are 15-minute, day-ahead schedules. Up to 16 revisions in the schedule are allowed in a day. The F&S requirement varies from state to state and is often different for wind and solar generation. This requires segregation of generation into solar and wind components.

Buyer requirement or preference

A buyer of renewable energy may want to purchase specific quantum of wind or solar power, e.g. a discom may want to buy specific quantum of solar and wind because

• It has individual internal targets for wind and solar • Generation costs are different for wind and solar • It is buying electricity under feed-in-tariff programs which

have different tariffs for wind and solar • It has invited bids for wind and solar separately • PPA conditions define minimum and maximum power

injection permitted, based on technology

The table above demonstrates the range of challenges necessitating two tiered metering

for hybrid projects. Each of the regulatory requirements above are treated differently by

specific state regulation. Some examples of state specific treatment of wind and solar

energy is summarized in the table below.

Policy Area State Differential Treatment for Solar and Wind

Transmission, wheeling and banking charges

Madhya Pradesh

For solar projects, transmission, wheeling charges up to 4% are waived off and electricity duty is waived for 10 years.

100% banking is allowed up to 1 year with banking charges of 2%.

For wind projects, similar benefits are granted. However, if wind energy is sold to a third-party buyer other than discom or the generator itself, transmission and wheeling charge waiver is not available.

Haryana All transmission, wheeling, banking and electricity duty charges are waived off for solar projects, but no waivers are granted for other forms of renewables.

Karnataka Karnataka had granted complete waiver for all open access charges and losses for solar till March 2018 but has a charge of 5% for wind transmission and wheeling.

Forecasting and scheduling

Gujarat F&S requirement in the state of Gujarat define the permissible deviation depending on year of installation of wind projects, and separately for solar projects.

7 Penalties for

deviation too, vary for wind and solar.

7 The F&S Requirement in Gujarat allows deviation of ±12% for old wind projects (commissioned before

30.01.2010), ±8% for new wind projects (under section 7.5), ±7% for solar project (under section 7.7). The initial penalty for wind is INR 0.35/kWh, increasing to INR 0.70/kWh and INR1.05/kWh, and for solar, the

7

As can be seen, metering at level 3 or level 4 alone may result in several practical and

policy related challenges in implementation. These levels of metering are only suitable

if a hybrid project doesn’t require separate tariffs for wind and solar energy, is not

focused on meeting RPO or qualifying for REC, or the project site is located in a state

where F&S requirement are same for wind and solar projects. In most cases, additional

metering at a lower level would be required. We discuss those approaches below.

2.2 Metering At Generator Level (Level 2)

Metering at this level enables generator level segregation of energy, injected into the

grid from a hybrid farm. The segregation will be achieved as outlined in section 5.1. This

approach is necessary for those hybrid parks that have many generators owning

different generating plants and using the common evacuation infrastructure. For

supporting billing by each generator, level 2 metering must to be added in addition to

metering at level 3 or level 4, as desired. Metering at this level may not be required if the

entire hybrid farm has only one generator or if generators don’t use shared evacuation

infrastructure within the farm. At this level of metering, it is not possible to segregate the

wind and solar components and therefore, same challenges as outlined above are

applicable.

Level 2 metering is necessary, in conjunction with metering at level 3 or level 4, if the

hybrid farm has many generators and they use a shared evacuation infrastructure. If

there is only a single generator, metering at this level becomes redundant.

2.3 At Wind Turbine Generator Or Solar Block Level (Level 1)

With level 1 metering, coupled with metering at level 3 or level 4, separate accounting of

wind and solar generation is possible. This can be achieved using the loss allocation

approach outlined in section 5.1. The benefits of this approach are:

o Solar and non-solar RPO can be met

o Solar and non-solar REC can be issued

initial penalty is INR0.60/kWh, increasing to INR1.2/kWh and INR1.8/kWh. See Forecasting, Scheduling, Deviation Settlement and Related Matters of Solar and Wind Generation Sources Regulations, 2017; available at http://gercin.org/uploaded/document/8f42601e-b8dd-4f6f-9a08-f6d3f08dc662.pdf

8

o Power sale and tariff determination for solar and wind is possible, individually.

o Individual F&S requirement of wind and solar generation can be met

o Special fiscal and financial incentives for solar projects and wind projects can be

availed.

One of the challenges associated with this approach is that the number of meters to be

installed increase. For example, in a hybrid plant of 300 MW, with 75 MW of wind and

225 MW of solar, there may be 38-40 wind generators and 38-40 solar blocks. Level 1

metering in such a farm will result in installation of 80 meters, a significantly large

number. An approach of clustering wind turbine generators and solar blocks may be

adopted, especially in large hybrid farms, to minimize number of meters installed.

Currently, metering at level 1 is only allowed for clustered, independent wind and solar

projects but not widely practiced. Policy changes are required to permit wind turbine

solar block level metering for hybrid projects. An optimization approach may also be

required, in order to optimally cluster solar and wind blocks in a manner that manages

the number of metering locations, while keeping the benefits of shared evacuation

intact.

9

3 Proposed Measurement and Metering Approach for Hybrid Plants

From the above discussion and analysis, it can be inferred that the metering for wind-

solar hybrid projects should facilitate segregation of energy generation for different

generators into wind and solar components. Key factors such as ownership by one or

more developers within the farm, requirements of buyer of the power generated, and

state specific regulation all must be taken into account to develop the optimum approach

for metering. This section provides the best-fit approach to resolve the issues discussed

in the previous section and present some examples of scenarios where specific metering

approaches become necessary. A few commonly encountered scenarios, and

appropriate metering approaches are listed in Table 3.

Table 2 Scenario wise proposed metering approaches

Scenario Metering Recommendation

Generator: Single

Buyer: Single (indifferent to type of resource)

Delivery point: plant sub-station/ grid sub-station

F&S requirement: Same for wind & solar

REC: Not claimed

For delivery at plant substation:

Level 3

For delivery at grid substation:

Level 4

Generator: Single

Buyer: Single (without RPO requirement)

Delivery point: Plant or grid sub-station

F&S requirement: Different for wind & solar

RECs: Generator can claim

For delivery at plant substation:

Level 3 and Level 1

For delivery at grid substation:

Level 4 and Level 1

Generator: Single

Buyer: Multiple (with RPO requirement)

Delivery point: Consumer’s grid connection

Generator can use technology specific provisions for

wheeling, transmission, banking, generation-based

incentives

At Level 4 and Level 1

Generator: Multiple

Buyer: Multiple (with RPO requirement)

Delivery point: Consumer’s grid connection

Generator can use technology specific provisions for

wheeling, transmission, banking, generation-based

incentives

At Level 4, Level 2 and Level 1

Discoms currently only accept level 3 or level 4 metering for billing purposes. Additional

metering at level 1 or level 2 will allow segregation of power generated from wind and

solar, as well for different owners. Net energy generation can be calculated by

apportionment of evacuation loss to each wind generator and solar block.

Refer section 5.1 for loss apportioning approach in case of wind-solar hybrid project.

10

Figure 2 Proposed metering approach for wind-solar hybrid project

This metering approach can be used for projects where AC side outputs from wind and

solar blocks are integrated i.e. common feeder lines take electricity generated from wind

turbines and solar blocks to the pooling substation. This allows savings on evacuation

infrastructure costs. This approach will not work in case of DC side integration and solar

and wind generators (DC output of solar feeding DC input into the wind generator).

However such combinations are rare.

4 Case Study: Metering For A Hybrid Project In Karanataka

To clarify various considerations involved in developing a metering plan, let us consider

a hybrid farm of 300 MWp capacity in Karnataka.

The farm has single owner (generator).

The delivery point is at plant substation, where the grid interconnection is

provided.

Because there are other industrial facilities inside the farm boundary, the hybrid

capacity is developed on vacant land available in 2 clusters.

While designing it was found that the capacity mix of wind and solar generation in the 2

clusters is such that number and capacity of evacuation cables will not change

significantly even when wind and solar power, from each cluster, is taken independently

to the plant-pooling substation. Hence in this project, metering is carried out as follows

Level1 – cluster level. The total number of wind and solar clusters metered are 8.

11

Level 2 metering is not needed as the farm is owned by a single owner.

The grid interconnection point is at the plant itself, hence Level 3 metering is

planned and level 4 metering is not required.

At the 33kV side of pooling sub-station, 8 (Level 1) energy meters are installed, which

are measuring wind and solar power. On HT side (220 kV) of pooling sub-station the

final tariff meters are installed (Level 3). These tariff meters account for total energy

evacuated from the entire farm. The loss allocation is based on the 8 energy meter

installed at 33 kV side. The loss allocation allows segregation of final injected power into

wind and solar generation.

Figure 3 Case study: Metering at Kudgi project

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5 Loss Allocation Approaches

5.1 Loss Allocation to Power Generators in a Hybrid Project

This is possible in case of hybrid projects that incorporate a combination of metering at

level 3 or 4, with level 2. Segregation of final power injected from a hybrid farm, into

generator level power can be achieve as follows:

Where,

Mt - Total delivered energy at interconnection point (level 3/4 measurement)

Mi - Total power delivered by a plant owner ‘I' into the shared evacuation

infrastructure (level 2 measurement)

N – Number of generators

For example, in a hybrid farm, there are 2 generators each generating 280 MWh

(recorded at level 2 metering). They use a common infrastructure to evacuate to the

farm substation (level3), and energy injected into the grid is recorded at 550 MWh.

Loss Li = (280+280- 550)/(280+280) = 1.78%

Actual hybrid generation delivered by each generator at the interconnection point ~

280*(1-1.78%) = 275 MWh

That is, the total loss of 1.78 percent is allocated to the generators proportionately as per

their contribution to the total generation.

5.2 Loss Allocation To Wind And Solar Components

Segregation of final power generated from a hybrid generator/owner, into solar and wind

components can be achieved as follows:

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Where,

Mi - Total power metered by a Plant Owner infrastructure (level 2 measurement)

M – Number of solar and wind blocks for generator i

Msi = measurement for solar generation at a solar block (level 1), for generator i

Mwi = measurement for wind generation at a wind block (level 1), for generator i

The total solar energy injection for generator i SMSi = ΣMSi x Li

The total wind energy injection for generator I SMWi = ΣMWi x Li

For example the total generation from wind generator (ΣMw) is 100 Mwh and from solar

blocks is (ΣMs) 200 MWh

Total energy delivered (Mi) is recorded as 280 MWh

Therefore, Loss Lwsi = (200+100-280)/(200+100) = 6.6%

Solar generation at generator level = 200 x (1- 0.066) = 186.8 units

Wind generation at generator level = 100 x (1-0.066) = 93.4 units

Solar energy injected by the Generator into the grid = 186.8*(1-1.78%) = 183.5 MWh

Wind energy injected by the Generator into the grid = 93.4*(1-1.78%) = 91.8 MWh

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6 Policy Recommendations

As is evident from the discussion in sections above, hybrid projects present several

accounting and generation apportionment challenges in the context of a policy

framework that treats solar and wind generation differently, and a scenario where

generation from renewable energy sources is priced differently. As India progresses

along its path towards greater deployment of hybrid projects, several policy changes can

be developed in a manner which is cognizant of such arrangements, and streamline

implementation, thereby making it easier to develop hybrid projects. There are two

possible approaches to solve the solar wind hybrid metering issues.

Acceptance of multi-level metering as part of the policy framework: The

multi-level metering approach described in this document, can segregate the

energy injected into various components as required by different policy regimes

in the country.

This approach will need to be formally accepted in all states.

Convergence in policy treatment of solar and wind: As wind and solar

capacities scale up in India, it is seen that policy treatment for the two is

converging, e.g. tariffs discovered in bidding for wind and solar bids in 2017

have both discovered levels of INR 2.44-2.47 per kilowatt-hour. Several other

factors strengthen this case, e.g.

o States are opting for similar open access policies for solar and wind, with

differences being reduced. Special support to solar is now being withdrawn.

o Forecasting and scheduling standards are now being harmonized across

wind and solar and many states have same standards for both technologies.

o In discussion with policy makers, it appears that the difference between non-

solar and solar RPO will be eliminated in near future, and there will be greater

flexibility to meet RPOs by either technology.

In such cases, it may be useful to consider total injected power as renewable, not

requiring segregation into wind or solar, or allowing flexibility to treat injected power as

wind or solar depending on the commercial needs. Such a policy will however require

deeper consideration at center and state levels and may not be immediately

implementable.

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7 Conclusion

Hybrid projects are a new concept internationally and in India, and present several

challenges which must be addressed by a collaborative approach between developers,

state and central government, and regulators. Hybrid projects can help maximize the

generation from a given land area, and help drive lower cost of generation. Hybrid

projects also result in savings in terms of common utilization of capital expenditures, e.g.

cost of evacuation infrastructure.

Issues related to energy accounting, Renewable Portfolio Obligations, Renewable

Energy Certificates, Forecasting and Scheduling, Open Access charges etc. can be

handled by segregating solar and wind generation, and the paper recommends a bi-level

metering approach that can be developed to address unique challenges of using

common evacuation infrastructure.

It is proposed that regulators take an approach for metering of wind-solar hybrids in a

manner so as to permit wind and solar level segregation of injected power, and allow fair

loss allocation approaches to both sources, as recommended in the paper.

In the long run, India would benefit if policymakers increasingly focus on technology

neutral regulation, and make active attempts to align approaches to forecasting and

scheduling, wheeling and distribution, as well as develop incentive mechanisms such as

generation based incentive or net metering in a manner that is suitable for multiple

technologies, especially solar and wind. Market signals such as pricing discovered in

recent bids, and a convergence of prices of renewable power from multiple sources in

recent months further strengthens the argument for treatment of solar and wind

technology on an equal footing.

Government of India targets addition of 10 GW of hybrid capacity by 2022. This

ambitious target needs strong policy support, and can help become a significant driver

for implementation of hybrid projects across the country. Discussions presented in this

paper, and accompanying publication ‘White paper on Design Approach for Wind-solar

Hybrids’, being made available alongside this document make a strong case for the

critical role hybrid projects can play in effective utilization of resources.

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ANNEXURE 1 EXISTING POLICIES FOR WIND-SOLAR HYBRID PROJECTS

National Wind-solar Hybrid Policy Draft, 20168

The draft National Wind-solar Hybrid Policy sets a goal of 10 GW capacity by 2022. It

allows the implementation configuration to be based on AC or DC integration. The policy

allows existing wind and solar plants to be hybridized (known as Brownfield projects),

and also includes provisions for development of new hybrid plants (knows as Greenfield

projects). Under the policy, hybrid power can be procured through a transparent bidding

process under different mechanisms. Parameters that may be considered for bidding

include total capacity, capacity utilization facto (CUF) and unit price of electricity. Hybrid

power generation can be used by distribution companies to offset their solar and non-

solar Renewable Purchase Obligations (RPOs). All fiscal and financial incentives

available for independent wind and solar power projects can be made available for the

wind-solar hybrid projects. The policy envisions making low cost financing available for

projects through Indian Renewable Energy Development Agency (IREDA), multilateral

banks, and other financial institutions.

Andhra Pradesh Wind-solar Hybrid Power Policy Draft – 20169

Under this draft policy, Government of Andhra Pradesh (GoAP) has described the

complementary power generation profile of wind and solar in the Rayalaseema belt. The

policy remains in force for five years or till the next policy issuance. This policy sets the

basis for a way forward for wind-solar hybrid projects in Andhra Pradesh. The

configuration of projects is defined as combined generation or co-located or co-injection.

The plants will be categorized on the basis of their allocation before and after issuance

of policy and named as type A and type B hybrid plants. Type A is for existing,

operational, under-construction and allotted wind or solar power plants and type B is for

proposed wind or solar power plants.

In the case of new allocated projects, the choice of capacity split between wind and solar

lies with the developer. The capacity mix (wind:solar) can vary from floor ratio of 1:0.6

and ceiling ratio of 1:1.5. Solar and wind power are separately metered. For these

projects, grid connectivity with the Andhra Pradesh Transmission Company

(APTRANSCO) is proposed to be based on Ampacity i.e., limiting the amperes that

would flow in the transmission network, in opposition to MVA/MW connectivity. This

provides ease to developers in optimizing the sizing of the wind-solar hybrid project.

Tariff for sale of power to Andhra Pradesh distribution companies (APDISCOMs) will be

8 http://mnre.gov.in/file-manager/UserFiles/Draft-Wind-Solar-Hybrid-Policy.pdf

9 http://ukmspower.com/attachment/Draft_wind_solar_hybrid_policy_2016.pdf

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based on Feed- in- Tariff (FIT). Incentives available for independent solar and wind

projects are expected to be given. These projects avail the must run status similar to

other renewable energy power plants.

GoAP incentives remain in force for 25 years from the date of commissioning of the

project. Details of the incentives:

a. Power Evacuation: Projects will be exempt from paying supervision charges to

APTRANSCO/DISCOM towards the internal evacuation infrastructure within the plant site

and up to pooling sub-station.

b. Distribution Losses are exempt for feeding power at 33 kV or less.

c. There will be NO transmission and distribution charges for wheeling of power within the

state, and for sale outside the state, wheeling charges will be according to APERC.

d. Banking of 100% of energy shall be permitted during all 12 months of the year (April-

March). Banking charges shall be adjusted in kind at 2% of the energy delivered at the

point of drawl.

e. The cross subsidy surcharge shall be exempt for third party sale within the state for a

period of five years from Commercial Operation Date (COD). All hybrid power projects

are exempt from paying Electricity Duty for selling power to APDISCOMs.

Gujarat Wind-solar Hybrid Power Policy Draft - 201710

The Gujarat draft wind-solar hybrids policy remains in force for five years from the date

of issuance. Projects developed under the policy become eligible for availing benefits for

twenty five years from the date of commissioning. The policy suggests that the project

will be under AC integration configuration i.e., AC output of wind and solar generation

will be integrated at the pooling end sub-station, and wind and solar generation will be

metered separately. Projects are categorized as Type A (existing or under construction

wind/solar projects) and Type B (new wind-solar hybrid projects). The capacity mix

planning is kept open for the developer. Installation of the availability based tariff (ABT)

meter is mandatory on each turbine and solar project. Internal connectivity between

solar and wind capacity is not allowed prior to pooling end sub-station. The tariff will be

decided by competitive bidding (reverse bidding wherever required) for both Type A and

Type B projects, undertaken by DISCOMs separately for wind and solar. Transmission

charges applicable are similar to any normal open access consumer for captive use or

third-party sale.

10 https://gujepd.gujarat.gov.in/uploads/DRAFT%20GUJARAT%20WIND%20SOLAR%20HYBRID.pdf

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ANNEXURE 2 LOCATION OF RENEWABLE ENERGY METER AS PER CEA

REGULATION AND RPO

Figure 4 Location of Renewable Energy Meter

Main Meter is a meter which will primarily be used for accounting and billing of

electricity.

Check Meter is a meter which shall be connected to the same core of the Current

Transformer (CT) and Voltage Transformer (VT) to which the main meter is connected

and shall be used for accounting and billing of electricity in case of failure of main meter.

Interface Meter is a meter used for accounting and billing of electricity, connected at the

point of interconnection between electrical systems of generating company, licensee and

consumers, directly connected to the Inter-State Transmission System or Intra-State

Transmission System (covered under ABT and has been permitted open access by the

appropriate commission).

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