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AES installs First A123Systems 2MW H-APU Energy Storage System

AES Energy Storage, LLC, a subsidiary of The AES Corporation, has installed its first Hybrid Ancillary Power Units (H-APU) from A123Systems. The lithium-ion H-APU is designed to create another way for AES’ existing facilities to meet the power industry’s need for capacity, by supplying power plant reserve requirements and other ancillary services which enable the increasing use of renewable energy sources.

A123 is under contract to provide multiple Hybrid Ancillary Power Units in 2008 and 2009 for use in grid stabilization applications in several AES facilities across the world. The initial unit, installed at one of AES’s Southern California power plants, is capable of delivering 2 MW of power at close to 90% efficiency.

The Hybrid Ancillary Power Unit energy storage system can serve two functions. First, A123’s H-APU will absorb (charge) energy from the grid during times when the frequency or voltage is too high and inject (discharge) that energy back to the grid when it is too low. A123’s H-APU is expected to allow greater use of variable sources of energy such as wind and solar by rapidly absorbing or injecting energy as these sources vary.

The H-APU is expected to provide variable service much faster than existing power plants responding in seconds rather than minutes. And, because it is recycling energy already in the system, it will provide these services without unnecessary emissions.

Second, the Hybrid Ancillary Power Units are designed to provide backup services by storing energy until it is needed by the grid in the event of a power plant or other asset failure. In some markets, the portion of thermal power plant capacity normally reserved for ancillary services to provide reserve capacity and frequency regulation services can be freed up to operate at a higher capacity and produce more electricity and associated revenue.

Pending final approvals, the H-APU will be used to provide ancillary services for the California power market.



Great technology. A 2 megawatt capacitor. A lot more efficient than pumped hydro. And much faster than bringing an idling NG turbine on-line.

It's a shame it has to be used though. If PHEVs or EVs were more abundant and were connected to a smarter grid...no need. Like gridpoint's v2green product.

Henry Gibson

The VRB vanadium systems can supply much more energy capacity with a much more simple system and there is already one such unit in operation in the US with Pacific Corp. ..HG..


Every approach is helpful. I just wish the people writing these reports had a clue as to what they were writing about. What is a 2M Watt capacitor? how many nanoseconds or minutes or hours will it deliver 2MW?

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