Near isothermal combined compressed gas/pumped-hydro electricity storage with waste heat recovery capabilities

A ground-level energy storage and extraction system comprising:

• a reservoir for storing a working liquid;
• a common pressure vessel for storing both a volume of a gas and a volume of the working liquid in a common location;
• a pump fluidly coupled between said reservoir and said common pressure vessel;
• a check valve coupled between said pump and said common pressure vessel;
• a hydropower turbine fluidly coupled to a bottom portion of said common pressure vessel through a control valve;
• an electrical generator mechanically coupled to said hydropower turbine;
• and
• wherein, when the system is operating in an energy storage cycle at a first time, said pump is energized by a power source and temporarily interrupted to maintain a measured temperature of the volume of gas to within a predetermined temperature range as a portion of the working liquid is transferred from said reservoir to said common pressure vessel by said pump such that a volume of gas in said common pressure vessel is compressed inside said common pressure vessel and,
• wherein, when the system is operating in an energy extraction cycle at a second time that is later than the first time, the working liquid is directed to drive said hydropower turbine under pressure from the volume of gas which, in turn, drives said electrical generator to produce electricity to power a load at the second time.