Systems for underground energy storage and methods for their construction. Methods include forming a plurality of chambers underground connected to a plurality of multiple flow conduits, the plurality of chambers including an upper chamber and a lower chamber each containing a working fluid, each multiple flow conduit of the plurality of multiple flow conduits comprising an inner tubular segment having a flowbore interior to the inner tubular segment configured to flow the working fluid, and an outer tubular segment containing the inner tubular segment, wherein each multiple flow conduit defines an annulus between the outer tubular segment and the inner tubular segment configured to flow a compressed gas, by drilling a borehole in the earth formation, installing an outer tubular segment in the borehole, cementing the outer tubular segment at a target location, and installing the inner tubular segment inside the outer tubular segment.

The method according to the invention relates to the storage of energy in the form of a compressed fluid which is pumped into a container (2) arranged below a water surface (4) to store the energy, wherein the fluid entering the container displaces an existing content, comprising water, from the container and into the surrounding water, and compressed fluid is removed from the container (2) to remove energy, wherein surrounding water flows back into the container according to the volume of the removed, compressed fluid, characterized in that the container (2) is provided with flexible walls at least in some parts and is arranged on a seabed (6) or lake bed (6) and there is covered by ballast (15) such that it is pressed against the substrate even when completely filled with compressed fluid.

The method according to the invention relates to the storage of energy in the form of a compressed fluid which is pumped into a container (2) arranged below a water surface (4) to store the energy, wherein the fluid entering the container displaces an existing content, comprising water, from the container and into the surrounding water, and compressed fluid is removed from the container (2) to remove energy, wherein surrounding water flows back into the container according to the volume of the removed, compressed fluid, characterized in that the container (2) is provided with flexible walls at least in some parts and is arranged on a seabed (6) or lake bed (6) and there is covered by ballast (15) such that it is pressed against the substrate even when completely filled with compressed fluid.

An energy storage system includes a vessel for storing water, an energy conversion device, and a connection line connecting the vessel with the energy conversion device. The energy conversion device includes first and second housings, a pump turbine in the first housing, and a motor generator in the second housing. The pump turbine includes a first shaft and an impeller mounted on the first shaft. The motor generator includes a second shaft and a rotor at the second shaft for rotating relative to a stator. The second shaft is coupled to the first shaft for transmitting torque between the first and second shafts. The connecting line connects a low pressure opening with an opening for receiving water or discharging water. The second housing is filled with a gas for a barrier pressure during operation of the energy conversion device, such that the rotor rotates within the gas.

In accordance with the present invention an apparatus is provided to maintain separate upper and lower water levels in a bi-level tank. The purpose here is to maintain tank configurations for the water portion of an air/water pathway in the tank that will be followed by a buoyant power module during its electricity generating work cycle. During an operation, the module enters the tank and raises the lower water level. The apparatus is then expanded to displace a volume of water in the tank with a volume of air, which raises the upper water level. Subsequently, when the module leaves the tank, the upper water level is lowered. Further, the apparatus is collapsed to drop the lower water level back to its original level in the tank. Thus, the bi-level tank is reconfigured to receive another module, for another duty cycle.

In accordance with the present invention an apparatus is provided to maintain separate upper and lower water levels in a bi-level tank. The purpose here is to maintain tank configurations for the water portion of an air/water pathway in the tank that will be followed by a buoyant power module during its electricity generating work cycle. During an operation, the module enters the tank and raises the lower water level. The apparatus is then expanded to displace a volume of water in the tank with a volume of air, which raises the upper water level. Subsequently, when the module leaves the tank, the upper water level is lowered. Further, the apparatus is collapsed to drop the lower water level back to its original level in the tank. Thus, the bi-level tank is reconfigured to receive another module, for another duty cycle.

The energy transition involves the electrical power supply being almost completely covered by renewable energy sources such as solar plants or wind turbines. However, due to their naturally fluctuating output, these energy sources require the use of large energy storage systems, the realization of which still represents a major problem today. The present invention relates to supporting the construction of a large-scale pumped-storage power plant, e.g., in the Hambach open-pit mine, by enabling test operation as well as energy generation as early as during the construction phase.

The energy transition involves the electrical power supply being almost completely covered by renewable energy sources such as solar plants or wind turbines. However, due to their naturally fluctuating output, these energy sources require the use of large energy storage systems, the realization of which still represents a major problem today. The present invention relates to supporting the construction of a large-scale pumped-storage power plant, e.g., in the Hambach open-pit mine, by enabling test operation as well as energy generation as early as during the construction phase.

A pumped storage electricity generating system that includes a water feed line for introducing water into a pressure vessel. Water flow valves communicate with the pressure vessel to control introduction of water into the pressure vessel. A push plate is mounted for movement in the pressure vessel. A single motor, for example, hydraulic radial piston motors, may be adapted for reciprocating the push plate linearly between a first direction wherein water is drawn into the pressure vessel through the water flow valves and a second direction wherein water is conveyed downstream through the water discharge line under pressure to the hydroelectric turbine. Other embodiments are double-acting and convey water to the turbine on each stroke.

The invention relates to a system for storing and recovering energy, comprising at least two liquid containers for storing a liquid, the two liquid containers being preferably located at substantially the same level and/or preferably having a substantially identical volume, and a turbine unit for power generation, which connects the two liquid containers to one another and is designed in such a way that the liquid can flow from the one liquid container through the turbine and into the other liquid container and thereby drives the turbine, and a working gas provision unit for providing a working gas, in particular air, having a substantially constant working gas pressure, the working gas provision unit being connected to the two liquid containers and designed in such a way that the working gas having said constant working pressure conveys the liquid from the one liquid container, via the turbine unit and into the other liquid container.