A pumped hydro energy storage system and method are disclosed. The system employs a high-density fluid, such as a slurry, to improve power output. In some cases, the fluid is a binary fluid system, with a high-density fluid and a lower-density fluid, such as water. The lower-density fluid flows through the turbine unit of the system, avoiding the need to modify the system to handle the high-density fluid, while achieving improved power output. The system can be configured with one atmospheric reservoir for a higher-density fluid and another one for a lighter-density fluid. Each of them is connected to a pressurized cavity which is filled with the higher-density or lighter-density fluid. The atmospheric tanks may be at the same elevation, or the tank with high density fluid might be higher for increased energy output. For example, the system may be placed on a topographical elevation.

A pumped hydro energy storage system and method are disclosed. The system employs a high-density fluid, such as a slurry, to improve power output. In some cases, the fluid is a binary fluid system, with a high-density fluid and a lower-density fluid, such as water. The lower-density fluid flows through the turbine unit of the system, avoiding the need to modify the system to handle the high-density fluid, while achieving improved power output. The system can be configured with one atmospheric reservoir for a higher-density fluid and another one for a lighter-density fluid. Each of them is connected to a pressurized cavity which is filled with the higher-density or lighter-density fluid. The atmospheric tanks may be at the same elevation, or the tank with high density fluid might be higher for increased energy output. For example, the system may be placed on a topographical elevation.

A multi-mode subterranean energy system and a related multi-mode subterranean energy production method are disclosed. The system comprises subterranean tunnels (2, 3, 8, 9, 14) connecting an upper reservoir of water (1), an underground cavity (10) and a subterranean recipient (15), a turbine/pump unit (4), and water flow control means (5, 6, 7). The system optionally can be operated in four modes.

A multi-mode subterranean energy system and a related multi-mode subterranean energy production method are disclosed. The system comprises subterranean tunnels (2, 3, 8, 9, 14) connecting an upper reservoir of water (1), an underground cavity (10) and a subterranean recipient (15), a turbine/pump unit (4), and water flow control means (5, 6, 7). The system optionally can be operated in four modes.

The present invention is a reversible pump-turbine installation positioned in a vertical borehole instead of in a conventional underground powerhouse or deep concrete powerhouse. The required plant cavitation coefficient may be achieved by simply boring a vertical borehole to the required depth rather than routing the water flow to and from a deeply buried powerhouse. A pneumatically controlled pressure relief valve may be incorporated into this invention.

A reversible pump-turbine and also a guide vane for a reversible pump-turbine with a guide vane body, a pivot for rotating the guide vane body around an axis of rotation and two end faces. The guide vane body has a turbine leading edge facing the turbine flow and a turbine trailing edge facing away from the turbine flow, where the individual guide vanes come into contact with one another along closing edges when the wicket gate is closed, where the guide vanes each have two flow-guiding surfaces on either side of the axis of rotation and opposite one another that are limited by the two end faces. These two flow-guiding surfaces have different flow profiles.

A circular dam for generating, accumulating, storing, and releasing electrical energy comprises a wall defining a water reservoir built in an abundant body of water such as a sea or an ocean. Water inside the water reservoir is kept at a water level below the water level outside the wall so as to create a water level difference sufficient to operate one or more water turbines positioned across the wall of the water reservoir. Excess electrical energy from other renewable sources of electricity such as wind, solar power, or supplied by a local power grid is used to operate water turbines as water pumps to lower the water level inside the reservoir during times of peak supply of electricity. Water is drained from outside the wall back into the water reservoir to generate electrical energy by flowing over a plurality of water turbines. Generated electricity supplements electrical power for the local power grid during times of high demand.

A circular dam for generating, accumulating, storing, and releasing electrical energy comprises a wall defining a water reservoir built in an abundant body of water such as a sea or an ocean. Water inside the water reservoir is kept at a water level below the water level outside the wall so as to create a water level difference sufficient to operate one or more water turbines positioned across the wall of the water reservoir. Excess electrical energy from other renewable sources of electricity such as wind, solar power, or supplied by a local power grid is used to operate water turbines as water pumps to lower the water level inside the reservoir during times of peak supply of electricity. Water is drained from outside the wall back into the water reservoir to generate electrical energy by flowing over a plurality of water turbines. Generated electricity supplements electrical power for the local power grid during times of high demand.

A combined pump and turbine (electromechanical converter), which may be operable as a motorized centrifugal pump for starting a siphon and as an electromechanical turbine particularly for transmission of a liquid, such as water, in a water treatment plant.

A submersible hydraulic assembly for an energy storage plant is provided that includes at least one hydraulic machine and at least one first buoyancy chamber filled with at least one first buoyancy element. The at least one first buoyancy chamber is generally configured in such a way that the hydraulic machine is substantially neutrally buoyant when submerged in an environmental liquid. An energy storage plant is also provided as well as a method for performing maintenance operations on an energy storage plant and a method for assembling/disassembling an energy storage plant.