Pumped hydro energy storage system and method

A pumped hydro storage system comprising:

• a first reservoir, wherein the first reservoir is configured to contain a high-density fluid and includes a first reservoir flow port disposed at a bottom of the first reservoir;
• a second reservoir, wherein the second reservoir is configured to contain a lower-density fluid which has a density lower than that of the high-density fluid, and includes a second reservoir flow port disposed at a bottom of the second reservoir;
• a cavity tank disposed at a cavity tank elevation, wherein first and second elevations of the first and second reservoirs are higher than the cavity tank elevation of the cavity tank, wherein the cavity tank is configured with an upper cavity tank port and a lower cavity tank port, wherein the upper cavity tank port is disposed above the lower cavity tank port;
• a turbine unit, the turbine unit includes a first turbine unit flow port and a second turbine unit flow port, wherein the second turbine unit flow port is coupled to the second reservoir flow port;
• a penstock, wherein the penstock includes
• a first portion penstock coupled to the first reservoir flow port and the lower cavity tank port, wherein a lowest port of the first portion penstock is below the cavity tank, and
• a second portion penstock coupled to the upper cavity tank port and the first turbine unit flow port;
• wherein
• in power generation mode, the high-density fluid is configured to flow through the penstock towards the cavity tank and towards the second reservoir, forcing the lower-density fluid to flow through the turbine and into the second reservoir, the lower-density fluid turns the turbine unit in a first direction to generate power, and
• in recharge mode, the turbine unit pumps the lower-density fluid from the second reservoir through the penstock towards the first reservoir, forcing the high-density fluid back into the first reservoir;
• and
• wherein the lower-density fluid and high-density fluid are configured to prevent the high-density fluid from passing through the turbine unit.