Patent ID: 8450884

Claim:
An apparatus comprising: a first reversible gas compressor/expander configured to effect gas-liquid heat exchange with gas being compressed or expanding within a first chamber; a second reversible gas compressor/expander configured to effect gas-liquid heat exchange with gas being compressed or expanding within a second chamber; and a network of gas conduits and valves allowing selective fluid communication between the first reversible gas compressor/expander, the second reversible gas compressor/expander, a compressed gas storage unit, and a counter-flow heat exchanger, the network of gas conduits and valves selectively operable in one of the following modes: an energy storage mode wherein the first reversible gas compressor/expander operates as a compressor to flow compressed gas to the compressed gas storage unit, and the second reversible compressor/expander operates as a compressor to flow compressed gas to the compressed gas storage unit, such that an input energy is converted into pneumatic form, an energy delivery mode wherein the first reversible gas compressor/expander operates as an expander to receive compressed gas from the compressed gas storage unit, and the second reversible compressor/expander operates as an expander to receive compressed gas from the compressed gas storage unit, such that an input pneumatic energy is converted into another form of energy, and a heat engine mode wherein the first reversible gas compressor/expander operates as a compressor to flow compressed gas through the counter-flow heat exchanger to the second reversible gas compressor/expander operating as an expander, such that an input thermal energy is converted into a different form of energy.