Isentropic owns several international and U.S. patents and applications. U.S. Application Publication No. 2010/0257862 (’862 Application) describes and claims the PHES technology.
Entitled “Energy storage,” the ’862 Application is directed to an energy storage system (10) comprising compressor/expander means (20) including a compressor (21), an expander (22), and power input/output means (40).
The energy storage system (10) also includes a first heat storage means (50), a second heat storage means (60), high pressure transfer means (70, 71) and low pressure transfer means (80, 81).
To charge the system (10), a low pressure gas enters the compressor (21) through inlet (23) and passes into a compression chamber (24). The low pressure gas is compressed by a compression piston (25) and transferred via the high pressure transfer means (70) to the first heat storage means (50) where it transfers thermal energy to the first thermal store (53).
The gas then passes through the high pressure transfer means (71) and enters the expander (22) through inlet (27). The gas is then expanded in the expansion chamber (28) and is transferred by the low pressure transfer means (81) to the second heat storage means (60) where it receives thermal energy from the second thermal store (63).
Finally, the gas passes through the low pressure transfer means (80) and can start the process again by entering the compressor (21).
According to Isentropic’s PHES technology web page, each heat storage means contains mineral particulates as a storage medium to interact with the pumped gas.
The company says the PHES system provides very high (72-80%) round trip efficiency comparable with pumped hydro, high reversibility, i.e., the system can function as both an engine and a heat pump, and no geographical restraints.
Isentropic should be able to showcase all of these advantages soon. This GTM piece reports that a UK public-private partnership called the Energy Technologies Institute is investing $22 million to build a full-scale PHES demo system.
Eric Lane is a patent attorney at McKenna Long & Aldridge LLP in San Diego and the author of Green Patent Blog. Mr. Lane can be reached at email@example.com