Why energy storage? Technologies in use or R&D. Conclusion for energy storage systems.

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EnStorage Confidential

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Solar Power

generation reduces

conventional

generation requirements

Without Storage

With Storage

3000

2000

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•Shifting capacity night to day.•Lowering need for spinning reserve.•Lowering the need for new installations.

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.... Flexible Deployment

Electrical Energy Storage can be Connected in Several Strategic Locations: At the Load

At Transmission

Nodes

At Conventional Power Plants

At Renewable Energy Sites

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•High capacity

•Geographically limited.

•Using old gas mines for storing compressed air.

•Of peak energy used for compressing.

•Lowering the need for new installations.

•Adiabatic also stores the heat.

•The first commercial CAES was a 290 MW unit built in Hundorf, Germany in 1978.

• The second commercial CAES was a 110 MW unit built in McIntosh, Alabama in 1991.

•The third commercial CAES, the largest ever, is a 2700 MW plant that is planned for construction in Norton, Ohio

•Energy is stored mechanically in a rotating device.

• Good for up to 15min storage, short duration applications.

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Uncoupling of Power from Energy: High hours of storage Long life

Energy Energy

Power

Hours of Storage

Cost ($/kWhr)

Flow Batteries

Non-Flow BatteriesFlow Batteries

EnStorage Confidential

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Main concept:

1. Based on Vanadium Red-Ox chemistry.

2. Vanadium solutions are circulated both on anode and cathode.

3. Storage capacity (Energy) is based on tanks volume. Power is based on the size of the active electrodes .

4. Membrane is used for separation between anode and cathode.

5. Cation exchange membrane is used.

Tanks

Cells

•Expensive salts.

•Membrane price.

•High cycle #.

One tank: NaBr /NaBr3, second tank: Na2S4/Na2S2

•Expensive organic complex.

•limited cycle #.

• requires 100% DOD ever few cycles.

•Capacity & power conjoined.

•Regenerating the metal is very non efficient procedure

•Carbonization of the electrolyte.

Reaction : PbO2 + Pb + 2H2SO4       PbSO4 + 2H2O + 2e¯

At the negative electrode:      Pb + SO4           PbSO4 + 2e¯  

At positive electrode:     PbO2 + SO4 + 4H   + 2e¯           PbSO4 + 2H2O

40 MWh system in Chino, California, built in 1988.

•Generation of Hydrogen gas.

•Low efficiency.

•Low cycle life.

•Capacity & power conjoined.

•Carbon based electrodes.

•Higher cycle rates.

•Gel type electrolyte.

•Capacity & power conjoined.

Reaction : Na+ + xS NaSx

(cycling of Na)      

NAS battery technology has been demonstrated at over 190 sites in Japan totaling more than 270 MW with stored energy suitable for 6 hours daily peak shaving.

•Proven & mature tech.

•Requires 300C.

•Capacity & power conjoined.

•Self discharge during SB.

•Limited cycle #.

Cd electrode (-)

Ni electrode (+)

Net:

•Toxicity.

•Memory effect – requires special management system

•Capacity & power conjoined.

Cycling of Li ions

•High price.

•Safety issues .

•Complex managing cycling system.

•Capacity & power conjoined.

• Energy storage critical when looking at higher penetration rates of renewable energy.

•Storage can help improve quality of utilities and reduce cost.

•Many technologies are available – limited number on economic scale.

•The storage technology is coupled to the application.