Embodiments of the inventive concept include a manufactured pressure vessel including pressure cells having an impermeable layer containing porous material in which air can permeate, and a big mass layer disposed atop the pressure vessel to pressurize the air within the pressure vessel. The impermeable layer can include rubber from recycled vehicle tires. The big mass layer can have a total weight of between one (1) million and one (1) billion tonnes, or more. The big mass layer can include a remediated upper surface. The pressure vessel can include an interface section through which the air can enter and exit the pressure vessel. Pressure lines can be coupled to the interface section. A turbine center can be coupled to the pressure lines to generate electricity in response to pressurized air received through the pressure lines, or to pump air through the pressure lines into the pressure vessel to pressurize the pressure vessel.

A method for controlling the pressure in an underground storage volume, wherein the underground storage volume is at least in part filled with an incompressible fluid, the pressure is monitored, a compressible fluid can be introduced into and extracted from the underground storage volume, if the pressure reaches a predetermined upper pressure limit incompressible fluid is extracted from the underground storage volume for reducing the pressure in the underground storage volume; if the pressure volume reaches a predetermined lower pressure limit incompressible fluid is introduced into the underground storage volume for increasing the pressure in the underground storage volume. The method according to the present invention allows the increase the amount of compressible fluid like helium stored in an underground storage volume, e.g. a salt cavern, by adjusting the pressure by the introduction or extraction of an incompressible fluid like brine.

A thermal storage subsystem may include at least a first storage reservoir configured to contain a thermal storage liquid at a storage pressure that is greater than atmospheric pressure. A liquid passage may have an inlet connectable to a thermal storage liquid source and configured to convey the thermal storage liquid to the liquid reservoir. A first heat exchanger may be provided in the liquid inlet passage and may be in fluid communication between the first compression stage and the accumulator, whereby thermal energy can be transferred from a compressed gas stream exiting a gas compressor/expander subsystem to the thermal storage liquid.

A system and method for creating a subterranean storage facility at a location where there is underlying bedrock. A storage tank is provided that is formed from a cylindrical casing that is sealed with a top closure and a bottom closure. A first hole is excavated through the overburden. At the bottom of the first hole, a second hole is excavated into the bedrock. The storage tank is placed in the second hole with the top closure of the storage tank facing upward. The storage tank is set into the bedrock with a cement mixture. Pipe risers are extended into the storage tank through the first closure. The pipe risers extend up through the first hole and provide access to the storage tank.