Comparativa tecnologíasde almacenamiento de energía a gran escala.

Sumario Julio 2009

Prospectiva tecnológica yanálisis comparativo

Grandes sistemas estáticos de almacenamiento de

energía

Energy Storage Facility Load Profile Multiple Value Streams

Pumped Hydro 1

Availability 95% efficiency around 70%. 200 plus MW scale

Pumped Hydro 3

Capex = $3000/kW. Siting permit issues. 40 year life

Opex = $0.015/kWh

Pumped Hydro 4 – response rates

Pumped Hydro 2

Fuel cells

• PEM - low temperature 120 º C

• Phosphoric Acid (PAFC) and Molten Carbonate (MCFC) –medium temperature

• Solid Oxide (SOFC) -high temperature 1000ºC

Limitations of Fuel Cells• They reduce emissions, but do not reduce GHG unless hydrogen

fuel is derived using electrochemical processes from solar or wind powered converters. This is highly inefficient

• They suffer from poisoning of noble metal catalysts by CO/CO2

• Energy efficiencies are approximately 60% less than for the VRB-ESS

• High costs $3000- 4500/kW*

• Short cycle life – 1500cycles

* MTU and UTC 2007

Compressed Air Energy Storage

Ridge energy LLCGeneral compression in wind towers. Or in caverns salt domes etc.

Costs claimed around $1.8m/MW. HR= 4700btu/kWhRamp rates around 15seconds per 50MWRequires natural gas supply60MW or larger although tank compression on surface in smaller sizes proposed

1. Excess electricity is used to compress air

2. Air is pumped underground and stored for later use

CompressedAir

Air

Waste heat

4. The electricity produced is delivered back onto the grid

3. When electricity is needed, the stored air is used to run a gas-fired turbine-generator

Exhaust

Thermal Energy storage

• Hot water resistive heating - district heating – proven - low efficiency

• Molten Salt energy storage - solar concentrators –proven Expensive used in PV concentrators

• Graphite block – ex nuclear industry technology - research

• Ice storage – DSM approach - proven

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Consumer

Electricity Transport

Ulf Bossel – October 2005

Lead Acid Battery The de-facto standard

There are two types of Lead Acid Battery

- Flooded or vented

- Sealed: valve regulated lead acid (VRLA) and Gel types

- AGM (Absorbed Glass Mat) –advantages over Gel and similar cost

-Costs for UPS shallow cycle china lead acids $150/kWh

-Cost for deep cycle PV – EU -$500/kWh

-China $280/kWh

? Cannot leave battery in a charged state for long periods due tosulphation

? If VRLA battery is not gassing when charged then there is a danger of:

- Stratification of electrolyte

- Reduction in battery life

- Gell damage is voltage incorrect on charge

? Gassing when charging results in

- loss of electrolyte VRLA

- Explosive hydrogen formation

? Needs to be oversized for maximum cycle life

? SOC of battery hard to measure

? Charge to discharge ratio usually long – 5 to 1 : C-rates

Despite these problems they are the standard and there is a great body of knowledge

Problems with Lead Acid Batteries

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Depth of discharge impacts on ALL non FLOW batteries – reduces life and severely limits their

suitability for wind power smoothing

• High Temperature – 350ºC Molten sodium and sulphur

• 65 to 70% roundtrip efficiency (AC-AC) Small footprint

• Received large Japanese subsidies over 15 years of development –strong balance sheet

• Don’t handle partial cycling e.g. wind –integration for SOC

• SOC must be calculated/ averaged so periodic off line measurements required

• Overcharging is dangerous

• Requires parasitic heating to maintain temperatures

• 3500 cycles

• Maturing product, 250MW installed

Sodium Sulphur – NAS battery

2MW 7.5 hour NAS in Japan

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This means that in an average wind application, where about 200 to 600 partial cycles (average power swings of 50% (+-25%) occur per day averaging 0.3hours, the NAS battery with 6 usable hours of storage will experience an equivalent of 3 to 5% of full rating in partial discharges. From the energy throughput life curve below, the NAS battery will last around 100,000 cycles or about 1,000 days so 3 to 4 years. BY overrating the battery this can be extended. A VRB-ESS has NO such limitation nor overrating requirement.

NOTE: Required for Charge and Discharge

Equivalent VRB with no life limit for this application is 50% the power rating and 35% the storage (hours) and thus 20% the cost

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NAS versus VRB-ESS cost comparison for equivalent performance with wind

• NAS is modular MW x 6 hours. Cost with PCS and controls and storage thus China and EDF around $550 to 650/kWh or US$4million

• VRB-ESS can have any number of hours. IT requires 50% MW rating for same NAS and storage of only 2 hours for wind for every 6hours of NAS – because we know SOC accurately and have no cycle reduction due to deep cycles. Thus an equivalent VRB-ESS will cost US$2million

• VRB-ESS will last 3 times as long and then only costs $500k to extend life another 10 years. NAS would cost 3.5Million to replace. Life cycle cost thus VRB-ESS= $2.5million versus NAS $7.5million or 3 TIMES less.

• Longer life than lead acid

• Suffer from problems of memory effect

• Disposal problems

• Shortage of Cadmium

• Expensive

• The Golden Valley installation in Alaska 40MW for 15minutes – 4 x VRB-ESS size. 10x cost. Has perfumed well over 5 years

Nickel Metal Hydride (Ni-MH)

Nickel Cadmium (Ni-Cd)

• Similar to Ni-Cd but negative electrode uses metal alloy which absorbs hydrogen

• Hydride electrode has higher energy density than Ni-Cd so higher capacity for same size

• More environmentally friendly than Ni-Cad – no Cadmium

• Suffers memory effect

• Expensive

Lithium Ion (Li Ion)

• Cathode is Lithiated metal oxide

• High Efficiency

• High energy density – 130Wh/kg

• 2000 cycles at 88% DOD

• Problem in Large sizes is that special packaging for overcharge control – ($1050/kWh) is required

• Battery life exhibits logarithmic improvement with respect to both average depth-of-discharge and temperature

Lithium Titanate (A123), LI Phosphate (Valence), Lithium thionyl (Li-SOCl2) AMR, BYD (China)

? Li-ion is often misused as a battery type by misinformed OEM customers. While the layman term is what is most commonly referenced when talking about lithium batteries, it is really the true chemical compounds of the anode, the cathode and the separator that make up a cell. Cobalt Oxide, Iron Phosphate and Manganese Oxide are the most commonly used cathode materials. "Poly" or lithium-ion polymer batteries are often seen as a specific type of cell while in reality the term polymer in the name describes the separator structure. Poly cells with Cobalt Oxide or Iron Phosphate cathodes are used in cells today. No matter the makeup, each of the lithium ion cell variants require careful tuning of their key parameters to maximize cycle life.

? Signifcant cost challenges faced. Supply limited to three regions – ay acceptable cost. These gave limited capacity for major markets of cars. Tibet, Bolivia, (Brines) USA and Australia (Greenbushes)

Lithium Ion (Li Ion) continued

A123 Lithium

The Zebra - Battery

Metal-Air•Zinc Air

•Aluminum Air

High Energy Density and low cost BUT Difficult to recharge_ several groups proceeding with this Siemens and in the USA

• High Temperature battery – 270ºC 42kWh unit

• Developed by Anglo American and Daimler Benz and now a Swiss company

• Sodium Chloride and Nickel

• Expensive but energy density high

• Liquid sodium not sulphur as with NAS

Zinc Bromine Batteries – ZBB and Premium Power and Redflow (Australia) NetPower (China)

• 2000 cycles – zinc is plated on the negative electrode during each cycle

• Energy Density 33Wh/kg practical Power density 50 to 80W/kg

• Bromine – environmental issues

• Hard to scale

• Must be deep cycled and discharged weekly to maintain life. Cannot do deep cycles on a repeated basis. Cannot handle wind balancing

Zinc Bromine 2

• ZBB sell 3.5hour 45kW systems at $1000/kWh – have many systems in field 20 to 30 or so

• Premium Power have claims of $300/kWh – have had several disasters

• Net Power claim they will achieve $50/kWh – have no products yet (PCS costs are nearly $70/kWh right now!!)

Flow BatteriesRegenesys - Polysulphide Bromine – cross contamination of electrolytes, expensive recombination process control – targeted at very large systems due to complexity. Low cost electrolyte

• Deeya – Iron-Chrome small 5 year life low cost low efficiency 1.2V couple• Vanadium Bromine – experimental Australia and UK• Squirrel (Selenium) series flow VRB prototype–• Plurion – Cerium Zinc

Squirrel series VRB Cellenium Thaliand

• Reduces shunt current losses since series flow

• Reduces chance of dry cell and gas evaluation due to blockages

• Patent issues with Prudent

• Voltage issues in series systems, expensive and pressure issues

Plurion - UK

Prototype - Cerum Zinc: 10 year history – serious problems. Uses MSA so environmentally acceptable, higher cell voltage than VRB-ESS, crossover problems, membrane issues. Balancing problems.

Cellstrom VRB - Austria

• 10kW 100kWh – comprises 10 x 1kW cells

• Footprint larger than Prudent by 30%

• Patent issues with Prudent .

• Cost around 2 x Prudent

Competing technologies

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Year 2009Life cycles > 50% depth of

discharge

AC _AC Roundtrip efficiency

First time Capital cost

$/kWh to customer

Environmental Risk

Pros/ConsUse with

wind

Deep Cycle Gel LEAD ACID 3500 45% 1300 -1800

Medium clean up heavy

metals

recharge rate slow

NO

Sodium Sulphur Company NGK 3500 68% $675 Very High

Small footprint/charge control issues

SOC derived double sizing

Zinc Bromine Company ZBB

Premium Power, Redpower, NetPower

2500 60% $1,000 HighCompact / two

species

needs rebalancing every week

Iron Chromium Company Deeya

Energy. Originated by SEI

1800 55% $1,200 High no membranelimited life 5 years small

systems

Lithium Ion Companies A123,

AES2000 85% $6,000 High

very compact/ charge control

challenge

storage hours limited

Vanadium REDOX Company Prudent

Energy>100,000 times 65 - 75% $500 - $850

Medium indefinite life

electrolyte

larger footprint/SOC always known

Excellent ideal