Patent ID: 8495872

Claim:
A method of energy storage and recovery, the method comprising: during each of a plurality of cycles: (i) in a pneumatic chamber of a cylinder, at least one of compressing a gas to store energy or expanding a gas to recover energy, and (ii) during the at least one of compressing the gas or expanding the gas, circulating, without thermal conditioning thereof, a heat-exchange fluid through the gas to exchange heat between the gas and the heat-exchange fluid; and thermally conditioning, external to the at least one of compression or expansion, at least a portion of the heat-exchange fluid between cycles, wherein, during each cycle, circulating the heat-exchange fluid comprises (i) pumping heat-exchange fluid from the pneumatic chamber into a first hydraulic chamber and (ii) pumping heat-exchange fluid out of a second hydraulic chamber separated from the first hydraulic chamber into the pneumatic chamber.