ARPA-E backs compressed air energy storage project -  

The New York Times has an article on ARPA-E investing in General Compression's CAES technology for an energy storage pilot project with Duke Energy - ARPA-E Is Poised to Put Products on the Grid.

ARPA-E, the government’s incubator for high-risk energy inventions, has its first graduate in the electricity area — a new energy storage technology — and on Thursday it announced a preliminary agreement to get it tested.

The agency, more formally the Advanced Research Projects Agency – Energy, modeled after the Defense Department’s longstanding program, said it had signed a memorandum of understanding with Duke, the big utility company, and the Electric Power Research Institute, the nonprofit utility consortium, to try out the inventions in the real world.

The agreement will “provide the connective tissue for ARPA-E,’’ said Arun Majumdar, the agency’s director, and “provide the test bed to see how to create value in the actual business.’’

The first candidate will probably be General Compression, a company to which ARPA-E directed $750,000; that advanced the technology enough for the firm to raise $12 million privately, Mr. Majumdar said. The company developed a way to pump air into an underground cavern, using electricity generated at inconvenient hours. When the energy is needed, the air flows back out again through a generator.

An older technology accomplishes this by adding natural gas to the exiting air and burning it to spin a turbine; General Compression uses no fuel at all. Its “round-trip efficiency,” meaning the amount of energy delivered versus the amount it takes in, is 70 to 75 percent, the company says.

Energy storage is considered a crucial complement to wind power and possibly solar power as well, smoothing out production and ensuring that the energy is available when it is most valuable, but today’s systems are expensive and thus are not in wide use.

Mr. Mujamdar said that ARPA-E hoped the air compression technology can be scaled big enough to store a gigawatt-hour, equal to the entire output of a large nuclear plant for an hour. Price is a crucial consideration, and ARPA-E has determined that a utility could probably afford to pay $100 per kilowatt-hour of storage.