Systems and methods for energy storage and recovery using rapid isothermal gas expansion and compression

A system for substantially isothermal expansion and compression of a gas, the system comprising:

• a cylinder assembly including a staged pneumatic side and a hydraulic side, the sides being separated by a movable mechanical boundary mechanism that transfers energy therebetween;
• a heat transfer subsystem in fluid communication with the pneumatic side of the cylinder assembly, the heat transfer subsystem comprising (i) a heat transfer fluid reservoir, and (ii) a fluid circulation apparatus arranged to pump heat transfer fluid from the reservoir into the pneumatic side of the cylinder assembly;
• and
• a spray mechanism disposed in the pneumatic side of the cylinder assembly for introducing the heat transfer fluid.

A staged hydraulic-pneumatic energy conversion system that stores and recovers electrical energy using thermally conditioned compressed fluids, the system comprising first and second coupled cylinder assemblies, wherein:

• the system includes at least one pneumatic side comprising a plurality of stages and at least one hydraulic side, the at least one pneumatic side and the at least one hydraulic side being separated by at least one movable mechanical boundary mechanism that transfers energy therebetween;
• and the system further comprises a heat transfer subsystem in fluid communication with the at least one pneumatic side, the heat transfer subsystem comprising:
• a circulation apparatus in fluid communication with the at least one pneumatic side for circulating a fluid through the heat transfer subsystem;
• and
• a heat exchanger comprising:
• a first side in fluid communication with the circulation apparatus and the at least one pneumatic side;
• and
• a second side in fluid communication with a liquid source having a substantially constant temperature,
• wherein the circulation apparatus circulates the fluid from the at least one pneumatic side, through the heat exchanger, and back to the at least one pneumatic side.

A staged hydraulic-pneumatic energy conversion system that stores and recovers electrical energy using thermally conditioned compressed fluids, the system comprising first and second coupled cylinder assemblies, wherein:

• the system includes at least one pneumatic side comprising a plurality of stages and at least one hydraulic side, the at least one pneumatic side and the at least one hydraulic side being separated by at least one movable mechanical boundary mechanism that transfers energy therebetween;
• and the system further comprises:
• a heat transfer subsystem in fluid communication with the at least one pneumatic side, the heat transfer subsystem comprising (i) a heat transfer fluid reservoir, and (ii) a fluid circulation apparatus arranged to pump heat transfer fluid from the reservoir into the at least one pneumatic side of the system;
• and
• a spray mechanism disposed in the at least one pneumatic side for introducing the heat transfer fluid.