FLUID STORAGE IN COMPRESSED-GAS ENERGY STORAGE AND RECOVERY SYSTEMS

1 - 112 . (canceled)

113 . A method of energy storage utilizing a compressed-gas energy storage system selectively fluidly connected to a lined underground reservoir at least partially surrounded by rock, the method comprising:

substantially isothermally compressing gas with the energy storage system at a compression temperature;

transferring the compressed gas to the lined underground reservoir for storage; and

thereafter, exchanging heat between the stored compressed gas and the rock at least partially surrounding the lined underground reservoir to change a temperature of the stored gas to a storage temperature different from the compression temperature.

114 . The method of claim 113 , further comprising thermally conditioning the compressed gas during transfer to the lined underground reservoir by at least one of (i) spraying droplets of a heat-transfer liquid into the gas or (ii) forming a foam comprising the gas and a heat-transfer liquid.

115 . The method of claim 113 , wherein the storage temperature is lower than the compression temperature.

116 . The method of claim 113 , wherein the storage temperature is higher than the compression temperature.

117 . A compressed-gas energy storage and recovery system comprising:

a cylinder assembly for at least one of compressing gas to store energy or expanding gas to recover energy;

a heat-exchange subsystem for thermally conditioning the gas during the at least one of compression or expansion via heat exchange between the gas and a heat-transfer liquid;

a lined underground reservoir for storing at least one of compressed gas or heat-transfer fluid in an interior volume thereof, the lined underground reservoir being substantially impermeable to fluid and comprising an inner steel layer surrounded by an outer concrete layer;

a source of heat-transfer fluid fluidly connected to the interior volume of the lined underground reservoir; and

a sink for heat-transfer fluid fluidly connected to the interior volume of the lined underground reservoir.

118 . The system of claim 117 , further comprising:

disposed within the interior volume of the lined underground reservoir, a nozzle for introducing heat-transfer fluid into the interior volume as a spray of droplets or as a foam;

a first pipe fluidly connecting the cylinder assembly to the interior volume of the lined underground reservoir;

a second pipe fluidly connecting the source of heat-transfer fluid to the nozzle;

a third pipe fluidly connecting an area proximate a bottom portion of the interior volume of the lined underground reservoir and the sink for heat-transfer fluid; and

a pump configured to transfer heat-transfer fluid through the third pipe to the sink for heat-transfer fluid.

119 . The system of claim 117 , wherein the source of heat-transfer fluid and the sink for heat-transfer fluid are the same body of liquid.

120 . A compressed-gas energy storage and recovery system comprising:

a cylinder assembly for at least one of compressing gas to store energy or expanding gas to recover energy;

a heat-exchange subsystem for thermally conditioning the gas via heat exchange between the gas and a heat-transfer liquid; and

selectively fluidly connected to the cylinder assembly, a lined underground reservoir for at least one of (i) storage of gas after compression, (ii) supply of compressed gas for expansion, (iii) storage of heat-transfer liquid, or (iv) supply of heat-transfer liquid.

121 . The system of claim 120 , wherein the lined underground reservoir comprises a liner at least partially surrounded by at least one of earth, dirt, or gravel.

122 . The system of claim 121 , wherein the liner comprises at least one of steel or concrete.

123 . The system of claim 121 , further comprising, disposed on at least one of an inner surface of the liner or an outer surface of the liner, a coating for at least one of sealing the liner to prevent fluid flow therethrough, preventing corrosion or degradation of the liner, or for thermally insulating the liner.

124 . The system of claim 120 , wherein at least a portion of the lined underground reservoir is disposed below ground level.

125 . The system of claim 120 , wherein the lined underground reservoir comprises therein a liquid containment region disposed above a bottom surface of the lined underground reservoir.

126 . The system of claim 120 , further comprising, disposed within the lined underground reservoir, at least one of a spray head or nozzle for introducing at least one of heat-transfer liquid or foam.

127 . The system of claim 120 , wherein the lined underground reservoir comprises a container buried beneath and surrounded by at least one of earth, dirt, or gravel.

128 . The system of claim 127 , wherein the container comprises steel.

129 . The system of claim 127 , further comprising, disposed between the container and the at least one of earth, dirt, or gravel, at least one of concrete, an insulating material, fiberglass, or carbon fiber.

130 . The system of claim 129 , wherein the at least one of concrete, an insulating material, fiberglass, or carbon fiber is disposed directly on the container with substantially no gap or air therebetween.

131 . The system of claim 120 , further comprising, disposed within the lined underground reservoir, a circulation apparatus for pumping liquid disposed proximate a bottom surface of the lined underground reservoir to a point outside of the lined underground reservoir.

132 . The system of claim 131 , wherein the lined underground reservoir comprises therein a liquid containment region disposed above a bottom surface of the lined underground reservoir, and further comprising, disposed within the lined underground reservoir, a second circulation apparatus for pumping liquid disposed in the liquid containment region to a point outside of the lined underground reservoir.

133 . The system of claim 120 , further comprising, extending from the cylinder assembly to a point within an interior volume of the lined underground reservoir, a pipe for transferring gas between the cylinder assembly and the lined underground reservoir.

134 . The system of claim 120 , wherein the lined underground reservoir comprises a plurality of discrete containers disposed within a shaft extending below ground level.