System for underwater compressed gas storage

A system for storing compressed gas, the system comprising:

• a surface structure disposed in a body of water, wherein the surface structure includes a compressor and expander assembly associated therewith, wherein the compressor and expander assembly includes a compressor, a heat exchanger and a gas expander assembly, and wherein the compressor and expander assembly is secured on, mounted to or otherwise associated with the surface structure,
• a gas storage assembly, wherein the gas storage assembly includes at least one gas receiver and is in fluid communication with the compressor and expander assembly, wherein the gas storage assembly is disposed in the body of water, wherein the gas storage assembly is configured to move within the body of water from a first level to a second level when compressed gas is added to the gas storage assembly, wherein the second level is deeper than the first level,
• a thermal storage assembly that includes one or more tanks containing water therein, wherein the thermal storage assembly is in thermal communication with the compressor and expander assembly, and
• a tether extending between the surface structure and the gas storage assembly.