Pumped storage power plant, method for operating a pumped storage power plant and pumped storage system

Description

[0001] The present invention relates to a pumped-storage power plant. Furthermore, the present invention relates to a method for operating a pumped-storage power plant. Finally, the present invention provides a pumped-storage system.

[0002] Due to the finite nature of fossil fuels, the need for and demand for renewable energies is increasing. Unlike conventional energy producers such as power plants, energy generation from renewable sources is intermittent and depends, for example, on weather conditions. This presents numerous challenges. For instance, there can be a surplus of green electricity generated from renewable energy sources. Conversely, depending on climatic conditions and the associated highly fluctuating availability of wind and solar energy, there is often too little green electricity available, necessitating a return to fossil fuels.The general objective is to temporarily store a sufficient quantity of surplus renewable electricity in such a way that it can be economically made available again at a specific time during grid overload or under climatic conditions where renewable electricity cannot be generated. Due to the globally limited energy / electricity storage capacity of sufficient size and economic viability, the search for new solutions continues.

[0003] Of the storage concepts known to date—pump-storage power plants, batteries, compressed air energy storage, flywheel energy storage, and thermal energy storage—pump-storage power plants have proven particularly effective. These plants pump water from a lower-lying reservoir (downstream) to a higher-lying reservoir (upstream) during periods of low electricity demand, such as at night, where it is stored. To meet peak demand and make the stored energy available again, the upstream water, now carrying increased energy, is released back into the downstream reservoir via power-generating turbines to produce electricity. The geographical possibilities for such pumped-storage power plants are severely limited worldwide.

[0004] DE 10 2014 016 640 A1 discloses an underground gravity pumped storage system for storing electrical energy. In this system, a piston that can be moved up and down is sealed within a hermetically sealed, underground water shaft. A turbine-pump arrangement allows water to be pumped in the shaft in such a way that the piston can be raised and lowered. To store energy, water is pumped under the piston to raise it against gravity, i.e., the force of the piston's weight, thereby generating potential energy. To convert the potential energy into electrical energy, the piston is moved back to its lowered position, which pumps water back to the turbine-pump arrangement, driving the turbine that powers a generator.

[0005] US 2008 / 012344 A1 comprehensively describes a pumped storage power plant: a working cylinder partially immersed in a working fluid reservoir, with an upper fluid compartment substantially above a fluid level of the working fluid reservoir and a lower fluid compartment below the fluid level; a buoyancy piston that is guided to move relative to the working cylinder in the direction of gravity and seals the upper fluid compartment from the lower fluid compartment in such a way that a gravity-induced fluid exchange between the upper and lower fluid compartments is prevented; an energy charging operation in which air is admitted into the upper fluid compartment so that the buoyancy piston is immersed into the lower fluid compartment relative to the fluid level; and an energy release operation in which a column of air built up in the upper fluid during the energy charging operation flows away.

[0006] Finally, DE 10 2008 040393 A1 discloses another pumped storage power plant comprising: a working cylinder with a working fluid compartment and a counter-working compartment; a working piston that is movable relative to the working cylinder in a working direction and seals the working fluid compartment from the counter-working compartment in such a way that fluid exchange between the working fluid compartment and the counter-working compartment is prevented; an energy charging operation in which fluid is admitted into the working fluid compartment so that, under the influence of the fluid pressure, the working piston is moved into the counter-working compartment by tensioning an elastic component on the working piston into a counter-working fluid filled in the counter-working compartment; and an energy discharge operation in which, under the influence of the tensioning force of the tensioned working piston, working fluid is forced out of the working fluid compartment.

[0007] A disadvantage of this type of pumped storage system is the large amount of underground space required. Particularly to provide high energy storage capacities, very great depths are necessary for the pumped storage system. Furthermore, it has proven disadvantageous that the pump must be very powerful to lift the piston against its own weight using water pressure. This makes such a pumped storage system prone to failure.

[0008] The object of the present invention is to improve upon the disadvantages of the known prior art, in particular to provide an efficient pumped storage power plant, a method for operating a pumped storage power plant and a pumped storage system that is scalable in a structurally simple manner in order to be usable for high energy storage capacities and is less prone to failure.

[0009] The problem is solved by the subject matter of claims 1, 8, 12 and 13.

[0010] A pumped-storage power plant is then provided. A pumped-storage power plant is generally an energy storage device that stores energy in the form of potential energy, which can be made available again in the form of electrical energy. In particular, it can be provided that the electrical energy to be stored is used to build up a high energy potential, whereby the electrical energy is first converted into kinetic energy of the working fluid used and finally into potential energy. In order to be able to use the stored energy again when needed, the process is carried out in reverse, that is, the stored potential energy of the working fluid is first converted into kinetic energy and finally into electrical energy. The pumped-storage power plant according to the invention can be used as an onshore pumped-storage power plant for use or installation on land or as an offshore pumped-storage power plant for use or installation on the seabed.Installation must be designed to take place in a body of water, such as a sea.

[0011] The pumped-storage power plant according to the invention comprises a working cylinder partially immersed in a working fluid reservoir, such as a water storage tank, for example a rain barrel, or a body of water, such as a lake or sea. The working cylinder has an upper fluid compartment located substantially above the fluid level of the working fluid reservoir and a lower fluid compartment located substantially below the fluid level. The working cylinder is not limited to a specific geometric shape and / or dimensions. A round, preferably circular, cross-sectional shape has proven advantageous, particularly with regard to hydrostatic pressure effects. With respect to the amount of energy to be stored, the volume of the working cylinder has been identified as the decisive containment factor, which depends in particular on the height and diameter of the working cylinder.In particular, the height of the working cylinder is crucial for the amount of potential energy that can be stored per unit volume. This amount of potential energy, also known as storage capacity, scales quadratically with changes in the height of the working cylinder. Furthermore, the internal volume of the working cylinder, and thus its storage capacity, also scales quadratically with its radius. Consequently, there is a desire to provide the largest possible working cylinder dimensions, especially in terms of height and / or diameter. The working cylinder is partially immersed in a working fluid reservoir, so that an upper fluid compartment is located essentially above the fluid level of the working fluid reservoir and protrudes from the reservoir to provide storage capacity.The subfluid compartment adjoining the upper fluid compartment, located below the fluid level and thus immersed in the working fluid reservoir, can be arranged in fluidic connection with the working fluid reservoir, wherein a fluid level outside the working cylinder essentially corresponds to the fluid level inside the working cylinder, which separates the upper fluid compartment from the subfluid compartment.

[0012] The pumped-storage power plant according to the invention also comprises a buoyancy piston, which is movably guided relative to the working cylinder in the direction of gravity and thus seals the surface fluid compartment from the subfluid compartment, preventing gravity-induced fluid exchange between the surface and subfluid compartments. The buoyancy piston is, for example, a hollow body, in particular a hollow cylinder, the shape and / or dimensions of which are adapted, for example, to an internal dimension of the working cylinder, in particular such that it separates the surface fluid compartment from the subfluid compartment in a fluid-tight manner. The buoyancy piston can, for example, be made of a material that has a lower density than the working fluid located in and / or to be stored in the working fluid reservoir. For example, plastics are suitable, which can in particular consist of so-called plastic waste.Regardless of the material chosen and the working fluid used, it must be ensured that the buoyancy piston generates a buoyancy force relative to the working fluid in the working fluid reservoir, preferably oriented opposite to the direction of gravity acting on the buoyancy piston. The working cylinder may be designed to be substantially closed and / or sealed from the environment, preventing the working fluid introduced into the surface fluid compartment from unintentionally escaping.

[0013] During the charging process of a pumped-storage power plant, working fluid is introduced into the surface fluid compartment. Examples of working fluids used include volatile fluids such as helium or liquids such as water. During charging, the buoyancy piston is drawn into the lower fluid compartment relative to the fluid level by the influence of the weight and / or hydrodynamic pressure of the surface fluid introduced into the surface fluid compartment. In an exemplary embodiment of the present invention, working fluid is continuously introduced into the surface fluid compartment to fill it, and the working fluid introduced into the surface fluid compartment is referred to as the surface fluid. During the continuous introduction of the surface fluid into the surface fluid compartment, a fluid column, in particular a surface fluid column, builds up within the surface fluid compartment.The volume of the surface fluid column depends on the internal dimensions of the outer cylinder, particularly the surface fluid compartment, and on the height of the surface fluid column, which builds up against the direction of lift of the lift piston and in the direction of gravity, exerting a weight force on the lift piston. The lift piston, which continuously moves into or submerges into the submerged fluid compartment, and in particular the submerged section of the lift piston, can essentially correspond in its longitudinal dimension to the height of the surface fluid column, or change accordingly with a change in the height of the surface fluid column. For example, under the influence of the hydrostatic pressure, also called gravitational pressure, of the surface fluid, the lift piston is submerged into the submerged fluid compartment due to the influence of gravity.Additionally or alternatively, a hydrodynamic pressure of the introduced surface fluid can be used to immerse the buoyancy piston into the subfluid compartment, which results from the kinetic energy of the inflowing surface fluid and depends in particular on the flow velocity and density of the inflowing surface fluid.

[0014] The pumped-storage power plant further comprises an energy release operation in which, under the influence of the buoyancy force of the buoyancy piston, surface fluid is forced out of the surface fluid compartment and / or in which a fluid column, in particular the surface fluid column, built up during the energy charging operation, preferably flows out of the surface fluid compartment at a constant rate. The energy release operation can, for example, be designed such that the buoyancy piston is preferably moved purely under the influence of the buoyancy force against the direction of gravity from the lower fluid compartment towards the surface fluid compartment, so that the surface fluid is at least partially forced out of the surface fluid compartment. The forced-out surface fluid can then form a water column, the height of which determines the displacement of the buoyancy piston in the direction of buoyancy.The energy output operation can also be designed such that the assembled column of surface fluid is preferably constantly drained from the surface fluid compartment, or can flow out, whereby it can be provided that the working fluid that has already flowed out of the surface fluid compartment draws in the remaining surface fluid still arranged in the surface fluid compartment, whereby in particular the portion of the working fluid that has already flowed out can exert a suction effect on the surface fluid still arranged in the surface fluid compartment. As a result of the surface fluid flowing out of the surface fluid compartment, the weight force of the surface fluid acting on the buoyancy piston against its buoyancy direction is reduced, so that the buoyancy force of the buoyancy piston with respect to the working fluid reservoir exceeds the weight force of the surface fluid at least briefly and thus displaces the buoyancy piston against the direction of gravity and thus in the direction of buoyancy.

[0015] The pumped-storage power plant can, for example, be designed such that the weight of the surface fluid essentially corresponds to the buoyancy force of the buoyancy piston, so that the buoyancy piston is in equilibrium. According to a further development, the equilibrium between the buoyancy piston buoyancy force and the weight of the surface fluid is only disrupted during the transition phases between energy output and energy charging. For example, the pumped-storage power plant is configured such that at a moment of demand, when the stored potential energy is to be made available again—which is provided in the form of the surface fluid located within the surface fluid compartment or by the buoyancy piston submerged in the working fluid reservoir—at least some of the surface fluid is released or forced out.The temporarily superior buoyancy force of the buoyancy piston causes it to re-emerge, at least partially, from the subfluid compartment until an equilibrium is re-established between the weight of the subfluid compartment and the buoyancy piston's buoyancy force. This occurs when the buoyancy piston comes to a standstill, meaning it no longer moves between the subfluid and subfluid compartments. According to the pumped-storage power plant according to the invention, the stored potential energy is essentially completely available for reconversion into electrical energy when needed. Due to the simple configuration of the present invention, the pumped-storage power plant can be easily scaled to any desired size, so that any storage capacity can be easily implemented according to the application, preferably by simply scaling the pumped-storage power plant.Furthermore, the division of the working cylinder into an upper fluid compartment and a lower fluid compartment has proven advantageous with regard to its reduced installation space requirement in the lower fluid compartment. Moreover, the utilization of buoyancy or weight according to the present invention has a beneficial effect on the efficiency of the pumped storage power plant, since, particularly during the charging phase, little energy is required and / or the device used for charging must have a low energy output.

[0016] According to an exemplary embodiment of the present invention, at least one seal is arranged between the lift piston and the working cylinder, preferably in the region of the fluid level, to seal the surface fluid compartment against the subfluid compartment. For example, a group of several seals can be arranged in the region of the fluid level to improve the sealing performance and provide redundancy, for example, in the event of a seal failure. Furthermore, it can be provided that the at least one seal, or at least one further seal, is arranged in the central region or in the upper half with respect to a longitudinal extent of the surface fluid compartment. In an exemplary further development, the at least one seal can be activated such that it holds the lift piston relative to the working cylinder, preferably during the energy charging operation and / or the energy discharge operation of the pumped storage power plant.For example, when the seal is activated, a holding force is generated between the lift piston and the working cylinder. The at least one seal can be activated, for example, such that the holding force between the working cylinder and the lift piston is preferably continuously adjustable. In a deactivated operating state of the at least one seal, the frictional force between the lift piston and the working cylinder can be essentially eliminated, or a certain frictional force can be maintained during the movement of the lift piston relative to the working cylinder. The seal can be activated, for example, by pneumatic and / or hydraulic actuation of the seal.For example, the at least one seal is designed as a hollow seal and / or has a cavity extending at least partially through the seal, which can be pressurized with hydraulic medium or pneumatically to activate or deactivate the seal. The at least one seal, or its activation, can be implemented such that, to activate the seal, hydraulic medium or air is introduced into the hollow seal, in particular its cavity. To deactivate the seal, the hydraulic medium or air is removed from the at least one seal or its cavity. According to a further embodiment, other principles for activating the seal are conceivable, for example, piezoelectric or electromagnetic activation.For example, it can be provided that each seal can be individually activated, in particular individually hydraulically and / or pneumatically, electromechanically, or piezoelectrically. According to an exemplary embodiment, the at least one seal is arranged circumferentially around the lift piston or on the inner wall of a working cylinder. Alternatively, the at least one seal can be designed and / or arranged such that it is not circumferential. In this context, it has proven advantageous, particularly to avoid leakage losses between the surface fluid compartment and the subfluid compartment, to arrange several seals that are not circumferential in an offset configuration, similar to a labyrinth seal. "Offset" can be understood to mean that any two adjacent seals, viewed in the direction of displacement of the lift piston, partially overlap and partially protrude from one another in the circumferential direction.The profile of the at least one seal is not limited to a specific shape. Furthermore, a wide variety of suitable materials are possible. According to an exemplary embodiment of the present invention, the at least one seal can hold the lift piston relative to the working cylinder by means of a material bond, a force bond, and / or a form-fit bond. In particular, the form-fit connection has proven advantageous with regard to stabilizing the pumped-storage power plant during its energy charging operation (storage state).

[0017] According to an exemplary embodiment of the pumped-storage power plant according to the invention, the at least one seal is received in a groove formed on an inner surface of the working cylinder and / or an outer surface of the buoyancy piston. For example, the at least one seal is received in the groove on the working piston side, so that the at least one seal moves with the buoyancy piston when the buoyancy piston moves, particularly between the surface and sub-fluid compartments. If the at least one seal is received in the groove on the working cylinder side, the at least one seal does not move with the buoyancy piston when the buoyancy piston moves, particularly between the sub-fluid and surface compartments, and / or is essentially stationary.For example, the at least one seal is designed such that, upon activation, it expands in the direction of the lift piston and / or the working cylinder to generate a holding force, such as a frictional force and / or a positive-locking force, between the lift piston and the working cylinder, preferably continuously. Because the at least one seal is prevented from expanding, preferably radially, on the lift piston side or the working cylinder side relative to the lift piston or the working cylinder, it expands in the opposite radial direction upon activation, in particular to compress itself in the space between the lift piston and the working cylinder, thereby generating a holding force.In an exemplary embodiment of the present invention, guide rollers can be arranged, for example, in the form of roller rings on the outer cylinder side and / or on the lift piston side, against which the lift piston and / or the working cylinder can roll when the lift piston moves between the surface fluid compartment and the subfluid compartment. This reduces wear on the pumped storage power plant according to the invention, in particular the wear resulting from the relative movement between the lift piston and the working cylinder. The resulting improved tribology also has a beneficial effect on the efficiency of the system. According to an exemplary further development, additional measures for improving the tribological properties of the pumped storage power plant can be provided, such as further wear- and / or friction-reducing measures, like lubrication, specific material selection, and / or coatings.For the arrangement of guide rollers on the lift piston side and / or the working cylinder side, corresponding grooves can be formed on the lift piston side and / or the working cylinder side, in which the corresponding guide rollers are arranged. It has proven advantageous, in a configuration with seals on the working cylinder side, to also arrange the guide rollers on the working cylinder side, and vice versa, in order to avoid a collision between the seal and the guide rollers, which could lead to damage to the at least one seal and / or the guide rollers. The inventors of the present invention have found that when using guide rollers, in particular roller rings, a preferably uniform and / or circumferential annular gap results between the lift piston and the working cylinder, which facilitates and / or clarifies the activation, preferably control, of the at least one seal.According to an exemplary embodiment, an air cushion can be provided as an alternative or additional measure to the at least one seal to seal the lower fluid compartment against the upper fluid compartment. The air cushion can be realized, for example, by enclosing a preferably predetermined air cushion section in which a volatile medium is pressurized. Leakage fluid between the upper fluid compartment and the lower fluid compartment would have to overcome or bypass not only the at least one seal but also the pressurized volatile medium forming the air cushion in order to reach the lower fluid compartment. This measure has proven particularly advantageous with regard to the longevity of the pumped-storage power plant according to the invention.

[0018] In an exemplary embodiment of the present invention, the activation of at least one seal, preferably for holding and / or releasing the lift piston relative to the working cylinder, and the displacement of the lift piston between the energy charging position and the energy output position are coordinated. For example, it can be provided that a relative movement of the lift piston relative to the working cylinder is preferably realized exclusively by activating or deactivating, preferably by controlling, the at least one seal.For example, the activation of the at least one seal and the displacement of the lift piston are coordinated in such a way that a frictional force during the displacement of the lift piston between the lift piston and the working cylinder is preferably continuously adjustable, wherein in particular the acting frictional force correlates with the expansion / contraction of the at least one seal resulting from activation of the seal.

[0019] In a further exemplary embodiment of the pumped-storage power plant according to the invention, an activation energy source, such as a pneumatic, electronic, and / or hydraulic source, is fluidically and / or electrically connected to the at least one seal. Thus, the at least one source can be activated or deactivated, in particular by being supplied with activation fluid and / or current. According to an exemplary further development, the activation energy source is coupled to a control and / or regulating device for preferably automated control and / or regulation of the activation energy source, in particular for activating or deactivating the at least one seal. For the purposes of the application, control is understood to mean that the behavior of the at least one seal, and thus of the pumped-storage power plant, is specifically influenced, in particular by controlling the activation or deactivation.Deactivation of at least one seal, preferably to hold or release the lift cylinder relative to the working piston. Control, in this context, means that a variable, namely the controlled variable, such as pressure within the seal, is continuously or intermittently measured and compared with a setpoint, the reference variable, such as a predetermined setpoint pressure. Based on this comparison, the controlled variable is adjusted or influenced. For example, the energy required to activate or deactivate the at least one seal can be supplied by connecting to a power grid, preferably separate from the pumped-storage power plant. Furthermore, it is possible that at least a portion of the energy required for activation or deactivation is drawn from a portion of the energy to be stored.For example, a portion of the energy to be stored can be temporarily stored, e.g., in a hydraulic or compressed air storage system, to make this portion available for subsequent activation or deactivation of the at least one seal. For instance, it has been found that an external power supply is unnecessary and the pumped-storage power plant can supply itself for activating or deactivating the at least one seal, thus enabling flexible use of the pumped-storage power plant even in locations without access to electricity.

[0020] According to an exemplary embodiment of the present invention, at least one preload seal seals the lift piston and the working cylinder against each other at an end of the lift piston facing away from the subfluid compartment. This means that the preload seal can be arranged on an upper end section of the lift piston or the surface fluid compartment when viewed in the direction of gravity. It should be understood that the at least one preload seal can be constructed analogously to the at least one seal and / or can be arranged on the pumped storage power plant, in particular on an inner surface of the working cylinder and / or an outer surface of the lift piston.The at least one preload seal can be operated such that, in the energy charging position of the buoyancy piston, the at least one preload seal is activated to build up a predetermined column of surface fluid, in particular, it is activated such that the weight of the surface fluid continuously exceeds the buoyancy force of the buoyancy piston relative to the working fluid as the buoyancy piston moves to a final energy position. In other words, the preload seal serves to initially build up a predetermined column of surface fluid during the energy charging operation of the pumped-storage power plant without allowing a gravity-induced movement of the buoyancy piston into the subfluid compartment. The preload seal is therefore initially activated until a predetermined column of surface fluid has accumulated in the surface fluid compartment above the buoyancy piston, while holding the buoyancy piston in place relative to the working cylinder.During the build-up of the surface fluid column, the weight force of the surface fluid, and in particular of the building surface fluid column, acting against the direction of lift on the lift piston, increases essentially continuously. As soon as a predetermined surface fluid column has been built up and / or a predetermined surface fluid column weight force is provided, the preload seal is actuated, in particular deactivated, to reduce the holding force acting between the lift piston and the working cylinder to hold the lift piston in place. This causes the lift piston to be immersed in the subfluid compartment in the direction of gravity relative to the fluid level due to the built-up surface fluid column, whose weight force exceeds the lift force of the lift piston. Preferably, the lift piston is set into motion abruptly when the preload seal is deactivated. This allows for high dynamics in the pumped storage power plant.This also has an advantageous effect with regard to the energy required to introduce the surface fluid into the surface fluid compartment, since only the potential energy, for example due to a height difference between the surface fluid compartment and the fluid reservoir, has to be overcome.

[0021] In an exemplary embodiment of the present invention, the buoyancy piston and / or the working cylinder is coupled to at least one additional body, for example a float, submersible body, compensating body and / or buoyancy body, arranged outside the working cylinder and at least partially immersed in the working fluid reservoir, preferably in any number, shape and / or connection type. The coupling can be effected, for example, by means of a cable construction which is attached on one side to the at least one additional body and on the other side to the buoyancy piston. The cable construction can, for example, be guided over the working cylinder, for example by means of pulleys, so that the forces acting between the additional body and the buoyancy piston can be supported by the working cylinder.In particular, the at least one additional body serves to compensate for or absorb forces acting on the pumped-storage power plant, especially in the freely floating configuration of the working cylinder within the working fluid reservoir. The additional body can be configured to transmit a force component to the buoyancy piston that opposes the weight of the surface fluid. This force component, in particular, counteracts the displacement of the buoyancy piston from the energy-discharging position to the energy-charging position, i.e., from the surface fluid compartment downwards relative to the fluid level into the subfluid compartment. Furthermore, the provision of at least one additional body has proven particularly advantageous when the pumped-storage power plant is designed such that the buoyancy force of the buoyancy piston exceeds the weight of the surface fluid acting opposite to the buoyancy force.This configuration allows for increased energy storage capacity. Initially, more energy is required to immerse the buoyancy piston in the subfluid compartment, i.e., to move it into the energy charging position, as the excess buoyancy must be overcome by providing an additional force, such as hydraulic pressure. This additional energy is then reversibly available during the pumped-storage power plant's energy release operation, where it can also be converted into electrical energy, thus increasing the electrical energy output.According to an exemplary further development, in which the working cylinder is freely floating, i.e., without being anchored to the bottom of the fluid reservoir, the working cylinder is coupled to at least one float, which is preferably located outside the working cylinder and at least partially submerged in the working fluid reservoir. It has been found that this supports the stabilization of the pumped-storage power plant in such configurations with regard to its floating arrangement in the working fluid reservoir. This means that the forces acting on the pumped-storage power plant as a result of switching between energy charging and energy release operations can be better balanced.

[0022] According to an exemplary embodiment of the present invention, the pumped-storage power plant comprises a pump-turbine unit, also called a pump turbine, for supplying the energy required for charging and for absorbing the energy released during discharge. For example, the pump-turbine unit is arranged outside the working fluid reservoir and / or above the fluid level. This means that, for example, there is no hydrostatic resistance at a turbine outlet of the pump-turbine unit, but only atmospheric pressure, so that less power is lost. Furthermore, this arrangement is characterized by improved maintenance access and significantly easier acoustic decoupling from the working fluid reservoir.The pump-turbine unit can be designed to pump working fluid into the surface fluid compartment during energy charging, preferably from the working fluid reservoir containing the working cylinder, or from a separate working fluid reservoir. According to an exemplary embodiment, the pumped-storage power plant can have at least one balancing element that floats in the working fluid reservoir and / or is partially submerged in the working fluid reservoir, wherein, in particular, the balancing element is designed to support or compensate for the forces acting on the pumped-storage power plant during operation of the pump-turbine unit.According to an alternative embodiment, which can be combined with the previously described embodiment, a separate pump can be connected to the pumped-storage power plant instead of the pump-turbine unit, and the pumped-storage power plant can be coupled to another, separate energy conversion device that converts the stored potential energy back into electrical energy during energy release operation. For example, during energy release operation, containers can be filled with the surface fluid pushed out or flowing from the surface fluid compartment and coupled to a generator via a chain-belt drive to convert the weight of the pushed-out or flowing surface fluid into a torque that the generator can use to produce electricity. For example, the pump-turbine unit can have at least one pumped-storage cylinder.Furthermore, it is conceivable that several pumped storage cylinders are supplied by a single pump-turbine unit. The pumped storage cylinders can be supplied in parallel or sequentially. Costs can be saved by reducing the number of components of the pumped storage power plant according to the invention. For example, a ring-shaped arrangement of the multiple pumped storage cylinders relative to the single pump-turbine unit is possible.

[0023] In another exemplary embodiment of the pumped-storage power plant according to the invention, the pump-turbine unit is configured to operate in generator mode when the power output phase begins. This allows the flow energy of the surface fluid forced out of and / or flowing away from the surface fluid chamber to be converted into mechanical energy during power output, which can preferably be used to drive a power generator. As mentioned above, further energy conversion devices can be coupled to the pumped-storage power plant to convert the stored potential energy into electrical energy, in particular electricity. For example, the pump-turbine unit can be arranged such that a substantially vertical flow direction results between the working fluid reservoir and the working cylinder and / or between the pump and the turbine.Furthermore, it is possible to provide for a substantially horizontal flow direction. With this arrangement, it has proven advantageous that no gravitational forces need to be overcome; however, it has also been found that flow losses must be accepted.

[0024] According to an exemplary embodiment of the present invention, the working cylinder, in particular the surface fluid compartment, is closed or at least partially open on a side facing away from the subfluid compartment. For example, the working cylinder can be sealed off from the environment, particularly fluid-tight, by means of a cover. For example, the working cylinder sealed off from the environment, in particular the cover, can be used to simplify the initiation of energy charging operation, since hydraulic pressure can be built up within the working cylinder, in particular within the surface fluid compartment, which is realized between the outer surfaces of the working cylinder, the lift piston, and the closure, in particular the cover, of the working cylinder, extending upwards towards the environment.Furthermore, an advantage lies in the fact that the working cylinder, particularly the surface fluid compartment, is designed to be fluid-tight from the environment. This means that during energy release operation, the buoyancy piston is subjected not only to the buoyancy force but also to a suction force provided by the surface fluid flowing out of the fluid compartment. This improves both the efficiency of the pumped-storage power plant and its dynamics, especially its responsiveness. It also prevents a so-called stick-slip effect between the buoyancy piston and the working cylinder, which can lead to an uneven flow of surface fluid from the fluid compartment into the energy release chamber. Additionally, the cover can serve a supporting function, for example, to guide or support the cable structure used to hold the additional components.In the event that the working cylinder, in particular the surface fluid section, is at least partially, preferably completely, open (i.e., corresponding to an outer dimension of the working cylinder), the surface fluid can be obtained, for example, from rainwater, which can drip into the surface fluid compartment via the working cylinder, which is open at the top towards the environment. Filling the surface fluid compartment with rainwater increases the efficiency of the pumped-storage power plant, as no energy is required to fill the surface fluid compartment.

[0025] In an exemplary embodiment of the pumped-storage power plant according to the invention, the working cylinder is arranged to float freely in the working fluid reservoir or is anchored firmly in a base of the working fluid reservoir. The working cylinder can be designed in the area of ​​the subfluid compartment such that fluid exchange with the working fluid reservoir is possible. For example, the subfluid compartment is preferably completely open at an end face facing the working fluid reservoir. Furthermore, the subfluid compartment can have a plurality of through-openings provided on the outer surfaces of the subfluid compartment, through which fluid exchange between the subfluid compartment and the working fluid reservoir is possible.

[0026] According to an exemplary embodiment of the present invention, the buoyancy force of the buoyancy piston with respect to the working fluid arranged in the working fluid reservoir is greater than the weight of the surface fluid in an end-energy-release operating position of the buoyancy piston, in order to move the buoyancy piston into the energy-charging operating position. The material of the buoyancy piston, in particular its density, can be adjusted with respect to the working fluid located in the working fluid reservoir such that the above condition is achieved. Additionally or alternatively, the material of the buoyancy piston, in particular its density, can be selected with respect to a surface fluid compartment size in the end-energy-release operating position of the buoyancy piston such that the above condition is achieved.According to an exemplary further development, the pump-turbine unit is designed to overcome the excess buoyancy force, in particular to move the buoyancy piston from the energy output operating position, especially the final energy output operating position, towards the subfluid compartment, in particular to assume the energy charging operating position.

[0027] According to an exemplary embodiment of the present invention, the pumped-storage power plant can have a surge tank, in particular to prevent flow-induced backflow in the pipes, especially those of the pump-turbine unit, which may be connected to the working cylinder. For example, the surge tank serves to collect any falling column of surface water that forms when the power output operation is interrupted. According to the invention, this can be initiated, for example, by the following two measures. First, at least one seal can be activated such that the lift piston is held in place relative to the working cylinder. Second, the pump-turbine unit can be controlled such that the flow of working fluid through the pump-turbine unit is interrupted.For example, the pump-turbine unit is provided with an inlet line for introducing surface fluid into the surface fluid compartment and an outlet line for draining the expelled or flowing surface fluid from the surface fluid compartment. In addition to the inlet and outlet lines, a compensating line can be provided into which the working fluid in the lines can flow to achieve the measures described above, in particular to prevent any further working fluid from flowing through the turbine-pump unit. The flow-induced pressure surges or pressure peaks that occur in the event of an interruption of power output can be compensated for by flooding the compensating line with the working fluid and propelling the working fluid to a height against the direction of gravity, where an equilibrium is established.Once the pump-turbine unit is restarted, and in particular once the pumped-storage power plant resumes energy output, the working fluid is first supplied to the pump-turbine unit from the equalization line before it is again supplied with working fluid from the inlet or outlet line. For example, the equalization line can have a U-shaped form or be designed as a pipe-in-pipe structure, in which the equalization line surrounds the inlet and outlet lines.

[0028] According to another aspect of the present invention, a pumped-storage power plant is provided. A pumped-storage power plant is generally an energy storage device that stores energy in the form of potential energy, which can be made available again in the form of electrical energy.

[0029] In particular, it can be provided that the electrical energy to be stored is used to build up a high energy potential, whereby the electrical energy is first converted into kinetic energy of the working fluid and finally into potential energy. In order to be able to use the stored energy again when needed, the process is carried out in reverse, i.e., the stored potential energy of the working fluid is first converted into kinetic energy and finally into electrical energy. The pumped storage power plant according to the invention can be designed as an onshore pumped storage power plant for use or installation on land or as an offshore pumped storage power plant for use or installation in a body of water, such as a sea.

[0030] The pumped-storage power plant comprises a working cylinder with a working fluid compartment and a counter-working compartment. The working cylinder is not limited to a specific geometric shape and / or dimensions. A round, preferably circular, cross-sectional shape has proven advantageous, particularly with regard to hydrostatic pressure effects. With respect to the amount of energy to be stored, the volume of the working cylinder has been identified as the decisive containment factor, which depends in particular on the height and diameter of the working cylinder. Specifically, the height of the working cylinder is crucial for the amount of potential energy to be stored per unit volume, with the amount of potential energy to be stored, which can also be referred to as storage capacity, scaling quadratically with a change in the height of the working cylinder.Furthermore, the internal volume of the working cylinder, i.e., its storage capacity, scales quadratically with its radius. Consequently, there is a tendency to provide the largest possible working cylinder dimensions, especially working cylinder height and / or working cylinder diameter.

[0031] The pumped-storage power plant also includes a working piston that is movable relative to the working cylinder in one direction and seals the working fluid compartment from the counter-working compartment in such a way that fluid exchange, in particular fluid exchange due to gravity, between the working fluid compartment and the counter-working compartment is prevented. The buoyancy piston is, for example, a hollow body, in particular a hollow cylinder, whose shape and / or dimensions are adapted to an internal dimension of the working cylinder, in particular adapted in such a way that it fluidly separates the working fluid compartment from the counter-working compartment. The buoyancy piston can, for example, be made of a material that has a lower density than any counter-working fluid that may be present in the counter-working compartment and / or than the working fluid to be stored.For example, plastics that can consist particularly of so-called plastic waste are suitable.

[0032] In an energy charging operation, fluid is introduced into the working fluid compartment, such that, under the influence of the fluid pressure and the weight of the introduced fluid, the working piston is moved into the counter-working compartment, thereby being tensioned. This tensioning of the working piston is achieved preferably by tensioning an elastic component on the working piston or by immersing the working piston in a counter-working fluid filled in the counter-working compartment. The energy to be stored is thus used to tension the working piston; that is, the energy to be stored is used to perform work in order to tension the working piston.The working piston can, for example, be designed as a buoyancy piston, analogous to the embodiment of the present invention described above, and possess a buoyancy force with respect to the counter-working fluid arranged in the counter-working compartment, which opposes the buoyancy piston immersing in the counter-working fluid.

[0033] The pumped-storage power plant according to the invention also comprises an energy release operation in which, under the influence of the tension force of the tensioned working piston, working fluid is forced out of the working fluid compartment and / or in which a fluid column of working fluid built up during the energy charging operation preferably flows out of the working fluid compartment at a constant rate. The forced-out working fluid can form a water column, the height of which determines the displacement of the working piston in the working direction. The energy release operation can also be designed such that the built-up working fluid column is preferably released from the working fluid compartment at a constant rate.The fluid can flow out, and it may be provided that the fluid that has already flowed out of the fluid compartment draws in the remaining fluid still in the fluid compartment, whereby in particular the portion of the fluid that has already flowed out can exert a suction effect on the fluid still in the fluid compartment. As a result of the fluid flowing out of the fluid compartment, the weight force of the fluid acting on the working piston against the direction of the clamping force is reduced, so that the clamping force acting on the working piston briefly exceeds the weight force of the fluid and thus the working piston is displaced against the direction of gravity and therefore in the direction of operation.

[0034] According to the pumped storage power plant according to the invention, the stored potential energy is essentially completely available for reconversion into electrical energy when needed. Due to the simple configuration of the present invention, the pumped storage power plant can be easily scaled to any desired size, so that any storage capacity can be easily realized according to the application, preferably by simply scaling the pumped storage power plant. Furthermore, the division of the working cylinder into a working fluid compartment and a counter-working compartment has proven advantageous with regard to its reduced installation space requirement in the area of ​​the counter-working compartment. In addition, the utilization of the buoyancy force or...The weight force according to the present invention advantageously affects the efficiency of the pumped storage power plant, since in particular little energy is required during storage, i.e. when entering energy charging mode, and / or the device used for storage must have a low energy output power.

[0035] In an exemplary embodiment of the present invention, the working piston is tensioned under the influence of the weight of the working fluid. For example, it can be provided that, during energy charging, a preferably constantly increasing column of working fluid is built up in the working fluid compartment. Furthermore, it can be provided that the pumped storage power plant is arranged or oriented such that a direction of gravity is oriented in the direction of the displacement of the working piston, preferably opposite to the displacement of the working piston. According to an exemplary embodiment, during energy charging, a tension force, preferably directed opposite to the direction of gravity, builds up during the introduction of working fluid into the working fluid compartment, and is oriented opposite to the displacement of the working piston into the counter-working compartment.According to an exemplary embodiment of the present invention, the working piston is configured to deform, in particular to expand, when the working fluid is introduced into the working fluid chamber, thereby increasing the size of the working fluid chamber. Furthermore, the working piston can be configured to deform, in particular to compress, when the working fluid is forced out or flows out of the working fluid chamber, thereby reducing the size of the working fluid chamber.For example, the working piston can be arranged in the working cylinder in such a way that a fastening part of the working cylinder, preferably a part of the working piston facing away from the counter-working compartment, is fixedly attached to an inner surface of the working cylinder, and a deformation part of the working piston adjoining the fastening part, which is preferably located on the counter-working compartment side, is displaceable in the working direction relative to the working cylinder, in particular displaceable by deformation, preferably displaceable by expansion and compression.

[0036] In an exemplary embodiment of the present invention, the working piston has at least two working segments, such as the fastening part and the deformation part, which are telescopically displaceable relative to each other in the working direction. The at least two working segments can extend apart when the working fluid is introduced into the working fluid compartment, wherein, in particular, one of the two working segments, especially the working segment on the counter-working compartment side, preferably the deformation part, moves in the direction of the counter-working compartment and / or the working segment facing away from the counter-working compartment, especially the fastening part, remains stationary during the introduction of the working fluid into the working fluid compartment.Furthermore, the at least two working segments can retract into one another when the working fluid is ejected from the working fluid compartment, wherein, in particular, one working segment, preferably on the opposite working compartment side, is moved in the working direction towards the working fluid compartment and / or the other working segment, preferably the working segment facing away from the opposite working compartment, preferably the mounting part, remains stationary. According to an exemplary embodiment, the working fluid compartment is essentially bounded by the at least two working segments. This means that the working fluid compartment volume is adjusted or varied during expansion or compression and / or during the extension or retraction of the at least two working segments. The telescopic retraction or retraction...The extension of the at least two working segments can be supported by at least one spring element that connects the at least two working segments to each other and / or pre-tensions the at least two working segments into the retracted position, which defines, for example, the energy output operating position.

[0037] In another exemplary embodiment of the pumped-storage power plant according to the invention, the working piston comprises an elastically deformable working bellows that essentially delimits the working fluid compartment. The working bellows can be designed such that it expands when the working fluid is introduced into the working fluid compartment and compresses when the working fluid is forced out or allowed to flow out of the working fluid compartment. For example, it can be provided that the working bellows is in an undeformed state when the pumped-storage power plant is in the final energy delivery operating position, preferably when the stored working fluid has been essentially completely forced out of the working fluid compartment or has flowed out of it. To enter energy charging mode, the restoring deformation force that builds up in the elastically deformable working bellows when the working fluid is introduced into the working fluid compartment must therefore be overcome.In the energy output operation, the built-up deformation restoring force is ultimately used to push the working fluid located in the working fluid compartment out of the working fluid compartment.

[0038] In an exemplary embodiment of the pumped-storage power plant according to the invention, a clamping force builds up when the working piston is clamped. This clamping force is oriented, in particular, in the direction of operation, preferably against a displacement direction of the working piston, especially a principal deformation direction of the working piston. In particular, the clamping force is oriented against the direction of gravity, so that it counteracts the weight of the immersed working fluid. Furthermore, it can be provided that the clamping of the working piston is effected by a spring. In particular, the clamping force acting on the working piston is applied by a spring. According to an exemplary embodiment, the spring is supported on an end face of the working piston facing the counter-working chamber and on a bottom surface of the working cylinder that preferably bounds the counter-working chamber downwards.For example, it can be provided that the spring is supported in such a way that when the working fluid is admitted into the working fluid compartment, the spring is pre-tensioned, in particular compressed, towards the bottom surface of the working cylinder and / or when the working fluid is discharged, preferably pushed out, from the working fluid compartment, the spring expands towards the end face of the working piston on the counter-working compartment side, preferably providing a deformation restoring force that acts on the working piston.

[0039] According to a further aspect of the present invention, a method for operating a pumped-storage power plant is provided. According to the method, energy working fluid is filled into an upper fluid compartment of a working cylinder partially immersed in a working fluid reservoir. The working cylinder is arranged in the working fluid reservoir such that the upper fluid compartment lies above a fluid level of the working fluid reservoir and is fluidically separated from a lower fluid compartment, which lies substantially below the fluid level of the working fluid reservoir, by a buoyancy piston.

[0040] Furthermore, according to the inventive method for releasing the energy of the surface fluid, the working piston is used to push the fluid out of the surface fluid compartment and / or to allow the surface fluid in the surface fluid compartment to flow out from a constant height.

[0041] According to a further aspect of the present invention, a method for operating a pumped-storage power plant is provided. In this method, a working cylinder is fluidically divided into a working fluid compartment and a counter-working compartment by means of a working piston.

[0042] Furthermore, working fluid is filled or introduced into the working fluid compartment to store energy.

[0043] According to the inventive method, to release energy, the working fluid filled or introduced into the working fluid compartment is forced out of the working fluid compartment and / or flows out from a constant height by utilizing a buoyancy force of the working piston, such as a tension force of an elastic component on the working piston and / or a buoyancy force of the working piston immersed in a counter-working fluid filled into the counter-working compartment.

[0044] According to an exemplary further development of the inventive method for operating a pumped storage power plant, the method can be set up to realize the pumped storage power plant according to one of the aspects or exemplary embodiments described above.

[0045] According to a further aspect of the present invention, which can be combined with the aspects and exemplary embodiments described above, a pumped storage system is provided. The pumped storage system can, for example, be implemented as an offshore or onshore pumped storage system. The pumped storage system according to the invention comprises at least two fluidically coupled pumped storage power plants, which are configured according to one of the aspects or exemplary embodiments described above. According to an exemplary further development, the pumped storage system, and in particular the pumped storage power plants, can be configured to process, store, and release energy from renewable resources, such as wind power, photovoltaics, and hydropower, for conversion into electrical energy.

[0046] Preferred embodiments are given in the dependent claims.

[0047] Further properties, features and advantages of the invention will be clarified below by describing preferred embodiments of the invention with reference to the accompanying exemplary drawings, which show: Fig. 1 a schematic sectional view of an exemplary embodiment of a pumped storage power plant according to the invention; Fig. 2 a detailed sectional view according to section II. Fig. 1 Fig. 3 shows a detailed sectional view according to section III. Fig. 1 ; Fig. 4 a further sectional view of the pumped storage power plant according to the invention Fig. 1 in another operating position; Fig. 5 a further sectional view of the pumped storage power plant according to the invention Fig. 1 in another operating position; Fig. 6 a further schematic sectional view of a pumped storage power plant according to the invention in a further embodiment; Fig. 7 a further schematic sectional view of a pumped storage power plant according to the invention in a further exemplary embodiment; Fig. 8 a further schematic sectional view of a pumped storage power plant according to the invention in a further exemplary embodiment; Fig. 9 a further schematic sectional view of a pumped storage power plant according to the invention in a further exemplary embodiment; Fig. 10 a further schematic representation of a pumped storage power plant according to the invention in a further alternative embodiment; Fig. 11 a further schematic representation of a pumped storage power plant according to the invention in a further alternative embodiment; Fig.Fig. 12 shows a further schematic representation of a pumped storage power plant according to the invention in a further alternative embodiment; and Fig. 13 shows a further schematic sectional view of a pumped storage power plant according to the invention in a further exemplary embodiment.

[0048] In the following description of exemplary embodiments of a pumped-storage power plant according to the invention, a pumped-storage power plant according to the invention is generally designated by reference numeral 1. With reference to the various exemplary embodiments, which are explained in more detail with reference to the accompanying figures, the description of the individual embodiments focuses primarily on the differences between them to avoid repetition, whereby identical or similar components are designated with the same or similar reference numeral.

[0049] The pumped-storage power plant 1 comprises a working cylinder 3 that is partially immersed in a working fluid reservoir 5, which may be, for example, a water storage facility, a body of water such as a lake or the sea. The working cylinder 3 includes an upper fluid compartment 9 located essentially above a fluid level 7 of the working fluid reservoir 5 and a lower fluid compartment 11 located essentially below the fluid level 7. According to the exemplary embodiment, the working cylinder 3 is realized as an essentially cylindrical component with constant dimensions, which defines a cavity 13 within its interior. The cavity 13 is closed to the environment in the region of the upper fluid compartment 9 and open to the working fluid reservoir 5 in the region of the lower fluid compartment 11. For example, the lower fluid compartment 11 has an open shape at one end face 15 towards the working fluid reservoir 5, for example, in the form of a through-opening 17.Furthermore, the subfluid compartment 11 has a plurality of preferably uniformly distributed through-openings 21 on its outer surface 19, through which additional fluid exchange with the working fluid reservoir 5 and the interior of the subfluid compartment 11 is enabled. According to the exemplary embodiment in . Fig. 1 The pumped storage power plant 1 is essentially oriented in the direction of gravity G, meaning that the working cylinder 3 is essentially oriented in the direction of gravity G, which according to Fig. 1 downwards. In other words, the working cylinder 3 extends essentially along a longitudinal direction oriented parallel to the gravitational direction G. A radial direction R, oriented essentially perpendicular to the gravitational direction G and thus to the longitudinal direction, defines a radial dimension of the working cylinder 3. As in Fig. 1 As shown, the through-openings 21 are distributed essentially uniformly along the surface 19 of the subfluid chamber 11 in both the longitudinal and radial directions R, although it is clear that a non-uniform distribution in the longitudinal and / or radial direction R is also conceivable. A lift piston 23 is arranged within the working cylinder 3 and is movably guided relative to the working cylinder in a displacement direction V oriented parallel to the direction of gravity G. The lift piston 23 is arranged in the working cylinder 3 and movably guided relative to the working cylinder 3 in such a way that the surface fluid chamber 9 is sealed off from the subfluid chamber 11, such that fluid exchange, as shown in the figure, is prevented. Fig. 1 as gravity-induced fluid exchange between upper fluid compartment 9 and lower fluid compartment 11 is prevented.

[0050] To seal the upper fluid compartment 9 against the lower fluid compartment 11, a group of several seals 25 is arranged between the lift piston 23 and the working cylinder 3. As described with reference to the Fig. 2 und 3 As can be seen, the seals 25 are received in a groove 29 formed on an inner surface 27 of the working cylinder 3. Referring again to Fig. 1 It can be seen that the group of several seals 25, according to Fig. 1 Seven circumferential seals 25 are distributed along the longitudinal extent of the working cylinder 3, but all are arranged in the area of ​​the surface fluid compartment 9. At least one of the seals 25, preferably all of the seals 25, can be activated, for example piezoelectrically or electromagnetically, and / or hydraulically and / or pneumatically, such that the at least one seal 25 expands in the direction of the lift piston 23 upon activation ( Fig. 2 ), to build up a holding force, such as a frictional force and / or a positive locking force, between the lift piston 23 and the working cylinder 3, preferably continuously, in order to hold the lift piston 23 firmly relative to the working cylinder 3. In Fig. 1 The pumped storage power plant 1 is schematically arranged in an energy output operating position, in particular an end-of-energy output operating position, in which the buoyancy piston 23 is located essentially entirely above the working fluid reservoir 5. This is because the buoyancy piston 23 is designed such that its buoyancy force with respect to the working fluid reservoir 5 is greater than its weight force acting in the gravitational direction G. As shown in Fig. 2 As can be seen, the upper seal 25 is activated, which manifests itself in an expansion acting particularly in the radial direction R, which in Fig. 2 This is evident from the convex bulge 31, which opens into two straight sections 33, 35 adjacent to the bulge 31. To achieve this, the seal 25 is, for example, designed as a hollow seal, which defines a cavity 37 in its interior, which is filled by means of a Fig. 1 The activation energy source 39, shown schematically, can be activated. The activation energy source 39 can, for example, be a pneumatic and / or hydraulic source and is fluidically connected via a line system 41 to at least one seal 25 in order to activate or deactivate the at least one seal 25, preferably hydraulically and / or pneumatically, in order to cause expansion in the radial direction R ( Fig. 2 ) or to cause compression in the radial direction R ( Fig. 3 ), which results in the holding force between the lifting piston 23 and the working cylinder 3 being reduced, preferably substantially eliminated.

[0051] Taking together the Fig. 1 , 4 and 5 The functioning of the pumped storage power plant 1 according to the invention is illustrated by means of three exemplary operating positions of the pumped storage power plant 1 and of the buoyancy piston 23 in the working cylinder 3. When the following description refers to an energy charging operation or an energy charging operating position, this means an operation or a state in which working fluid is introduced, for example, from the working fluid reservoir 5 into the surface fluid compartment 9, in particular into the cavity 13, especially with the aim of immersing the buoyancy piston 23 with respect to the fluid level 7 into the lower fluid compartment 11 under the influence of the weight force and / or the hydrodynamic pressure of the surface fluid introduced into the surface fluid compartment 9 (sequence of the Fig. 1 , 4 and 5The energy stored by the pumped-storage power plant 1 is at least partially used to introduce working fluid into the surface fluid compartment 9. For example, a pump-turbine unit 43, located essentially above the fluid level 7 and / or outside the fluid reservoir 5, can be coupled to the working cylinder 3, and in particular fluidically connected to the surface fluid compartment 9, in order to pump working fluid, for example, from the fluid reservoir 5 into the surface fluid compartment 9. For this purpose, the pump-turbine unit 43 has a piping system 45 that opens into the working cylinder 3 and, for example, has an inlet opening 47 and an outlet opening 49. As described in Fig. 1 As can be seen, the piping system 45 splits at a switch 51 into an inlet pipe 53 and an outlet pipe 55, each of which is fluidically connected to the surface fluid compartment 9. Starting from the in Fig. 1 the operating state shown, which defines, for example, an energy output operating state, in particular an end energy output operating position of the lift piston 23 within the working cylinder 3, into the energy charging operation ( Fig. 4 , 5 To transition to the working fluid, the pump-turbine unit 43 pumps working fluid via the piping system 45 into the surface fluid compartment 9, whereby, under the influence of the weight of the surface fluid in the surface fluid compartment 9, the piston 23 moves downwards in the direction of gravity G and continuously immerses itself in the working fluid reservoir 5. Fig. 4 The buoyancy piston 23 is partially immersed in the subfluid compartment 11, whereby the in Fig. 4 The illustrated operating position of the lift piston 23 starting from Fig. 1 as energy charging operating position and starting from Fig. 5 This can be described as the energy output operating state. When the following description refers to energy output operation, energy output operating state, or energy output operating state, it means a state or position in which, under the influence of the buoyancy force of the buoyancy piston 23 with respect to the working fluid 5, surface fluid is forced out of the surface fluid compartment 9 and / or in which a fluid column (not shown) of surface fluid built up during the energy charging operation preferably flows out of the surface fluid compartment 9 at a constant rate. The at least one activatable seal 25 is used to ensure or prevent displacement of the buoyancy piston 23 in the displacement direction V, whereby activation of the at least one seal 25, which state in Fig. 2 As shown, the holding force resulting from the expansion of the at least one seal 25 in the direction of the lift piston 23 causes the lift piston 23 to be held relative to the working cylinder 3, regardless of whether working fluid has already been pumped into the surface fluid compartment 9 or not. To release, preferably completely release, the lift piston 23 and thus to allow the lift piston 23 to move in the direction of displacement V, both in the direction of gravity G to enter energy charging mode and against the direction of gravity G to enter energy discharge mode, the at least one seal 25 is actuated again, in particular deactivated, which state in Fig. 3 is shown schematically.

[0052] Referring to Fig. 5 It can be seen that the buoyancy piston 23 is substantially almost completely immersed in the working fluid reservoir 5 and / or is substantially completely located within the subfluid compartment 11. The final energy charging operating state is reached when the buoyancy piston 23 is substantially completely submerged in the working fluid reservoir 5, i.e., when an upper-fluid compartment-side end face 57 of the buoyancy piston 23 is substantially at the level of the fluid level 7. At this point, the maximum storage capacity of the pumped storage power plant 1 according to the invention is reached. To deviate from the in Fig. 1 depicted state, which is, for example, an end-energy output operating state, in which in Fig. 5 To transition to the depicted near-final energy charging operating state, the exemplary design of the Fig. 1 bis 5 Working fluid is pumped into the upper fluid compartment 9 by means of the pump-turbine unit 43 until it is essentially completely filled with working fluid ( Fig. 5 ), and the weight force acting on the lift piston 23 from the surface fluid has caused the lift piston 23 to plunge downwards into the subfluid compartment 11 against the buoyancy force of the lift piston 23 with respect to the working fluid reservoir 5. In this final energy charging operating state, it can be provided, for example, that the buoyancy force of the lift piston 23 and the weight force of the surface fluid contained in the surface fluid compartment 9 are essentially balanced, i.e., a state of equilibrium is reached, so that no further displacement of the lift piston 23 in the displacement direction V occurs. Furthermore, it can be provided that the at least one seal 25, according to Fig. 5 The lowest seal 26, located near the subfluid compartment 11, is activated, in particular hydraulically and / or pneumatically actuated, to generate a holding friction force between the lift piston 23 and the working cylinder 3, which is intended to counteract displacement of the lift piston 23 in the displacement direction V. This makes it possible to maintain the energy charging operating state of the pumped storage power plant 1 and, if necessary, to switch to an energy output operating state when energy is required and the surface fluid is to be forced out or drained from the surface fluid compartment 9 in order to operate the pump-turbine unit 43 in generator mode. In generator mode, the pump-turbine unit 43 is designed to convert the flow energy of the fluid forced out of the surface fluid compartment 9 into a generator.to convert the outflowing surface fluid into mechanical energy, for example to drive a power generator, which in turn can be supplied to an electrical consumer to provide it with electricity or energy. The outflow or expulsion of the surface fluid from the surface fluid compartment 9 then takes place via a drain line 55. In the . Fig. 1 bis 5 Figure 1 shows an embodiment of the pumped storage power plant 1 in which the working cylinder 3 is arranged to float freely in the working fluid reservoir 5. Further embodiments are illustrated with reference to subsequent figures.

[0053] In Fig. 6 Figure 1 schematically illustrates an exemplary further embodiment of a pumped storage power plant 1 according to the invention, in which an additional body 59 is attached to the working cylinder 3, in particular to the subfluid compartment 11. The additional body 59 can, for example, be a ring weight body that completely surrounds the working cylinder 3. Alternatively, the additional body 59 can only partially surround the working cylinder 3 and / or be composed of several semicircular segment-shaped additional bodies 59, each of which partially surrounds the working cylinder 3. According to the embodiment shown in Figure 1, the additional body 59 can be arranged in a circular segment-like manner. Fig. 6 The additional body 59 is essentially completely submerged in the working fluid reservoir 5 and arranged outside the working cylinder 3. For example, the additional body 59 may be coupled to the buoyancy piston 23 by means of a cable construction (not shown). In particular, the at least one additional body 59 serves to compensate for or absorb forces acting on the pumped storage power plant 1, especially in the free-floating configuration of the working cylinder 3 in the working fluid reservoir 5. The additional body 59 may also serve, for example, to transmit a force component opposite to the weight of the surface fluid to the buoyancy piston 23 in order to prevent the buoyancy piston 23 from shifting from its position in the reservoir 5. Fig. 6 to counteract the transition from the depicted end-energy output operating position to an energy charging operating position. This configuration has proven particularly advantageous when the buoyancy piston 23 or its material is selected such that the buoyancy force of the working piston 23 with respect to the working fluid reservoir 5 is greater than the weight of the surface fluid in the end-energy output operating position of the buoyancy piston 23. This means that even with a completely filled surface fluid compartment 9, i.e., a completely filled free surface fluid compartment area 61, which is described in Fig. 6 The acting weight force, which is limited by the end face 57 of the lift piston 23 and the upper fluid compartment 9, is smaller than the lift force of the lift piston 23 with respect to the fluid reservoir 5. The pump-turbine unit 43, which is limited by the end face 57 of the lift piston 23 and the upper fluid compartment 9, is therefore smaller than the lift force of the lift piston 23 with respect to the fluid reservoir 5. Fig. 1 bis 5 As explained, it can be set up to overcome the excess buoyancy force, for example by providing hydrodynamic pressure by means of a flow of the working fluid, which acts on the front surface 57 of the buoyancy piston 23 and thus generates a force component in the gravitational direction G and thus against the direction of the buoyancy force.

[0054] The execution according to the Fig. 7 differs from the design according to Fig. 6 This is achieved essentially by providing an anchorage 63 for anchoring the working cylinder 3 to a base 65 of the working fluid reservoir 5. The anchorage 63 can, for example, have a grid- or cage-like structure, for example made of metal, and / or substantially completely surround the working cylinder 3, in particular the subfluid compartment 11. For example, the anchorage 63 is arranged exclusively below the fluid level 7 in the working fluid reservoir 5. An anchorage such as the cage-structure anchorage 63 according to Fig. 7 , has the advantage that forces acting on the pumped storage power plant 1 can be absorbed by the anchoring 63, which has a positive effect on the stability of the pumped storage power plant 1.

[0055] Unlike Fig. 7 , in which the working cylinder 3 is anchored on the bottom 65 of the working fluid reservoir 5, the working cylinder 3 is according to Fig. 8 The working fluid reservoir 5 is arranged to float freely. To absorb or compensate for the forces acting on the pumped storage power plant 1 during its operation, an arrangement of balancing elements 67 and floating or submerged elements 69 is provided. Both the balancing elements 67, which are arranged essentially outside the fluid reservoir, and the floating or submerged elements 69, which are immersed essentially below the fluid level 7 in the working fluid reservoir 5, are arranged according to Fig. 8 The compensating elements, designed as submersible bodies, are arranged near the fluid level 7 outside the working cylinder 3. These compensating elements, which are located essentially above the fluid level 7 and may, for example, be hollow and have a density lower than that of the working fluid in the working fluid reservoir 5, can be submerged into the working fluid reservoir 5 when forces act upon the pumped storage power plant 1. Due to their lower density, they generate a counterforce that causes the compensating elements 67 to resurface from the working fluid reservoir. For example, the compensating elements 67 are rigidly connected to the working cylinder 3 so that the counterforce occurring when the compensating elements 67 are submerged is transmitted to the working cylinder 3 to stabilize the pumped storage power plant 1 in its initial, undisplaced operating position.Essentially completely submerged in the working fluid reservoir 5 are the submersible bodies 69, whose density, for example, corresponds approximately to the density of the working fluid in the working fluid reservoir 5, so that the submersible bodies 69 behave essentially neutrally, that is, initially impart no force component to the pumped storage power plant 1. As soon as, as a result of force influences on the pumped storage power plant 1, it changes compared to the state in . Fig. 8 As the depicted position rises at least partially, that is, emerges from the fluid reservoir 5 against the direction of gravity G, the submerged bodies 69 act as a weight-increasing force for the pumped storage power plant 1. Thus, the submerged bodies 69 provide an additional weight force opposing the force of gravity, which can be used to move the pumped storage power plant 1 back, in particular to stabilize the pumped storage power plant 1 in its position relative to the fluid level 5, that is, its position in the direction of gravity G. It can be provided that the compensating bodies 67 and / or the floating or submerged bodies 69 are attached to the working cylinder 3 by means of a cable construction schematically indicated by the reference numeral 71. In particular, the cable construction 71 is supported on an upper end region, preferably the cover region 73 of the upper fluid compartment 9. The shape and / or the dimensions of the compensating bodies 67 or the floating or submerged bodies 69 are determined by reference numeral 71.The immersion body 69, like the auxiliary body 59, is not limited to a specific shape and / or dimensions. For example, it can be ring-shaped and / or partially or even completely surround the working cylinder 3 and / or be composed of segments, in particular semicircular ring-shaped structures that semicircularly surround the working cylinder 3. With regard to the... Fig. 7 , 8 and 9 It should be noted that for the sake of clarity, the conduit system 41 and the associated activation energy source 39 have been omitted, although activation energy source 39 and conduit system 41 are shown in the diagram below. Fig. 7 and 8 may be provided for.

[0056] In Fig. 9 Figure 1 shows another exemplary embodiment of a pumped storage power plant 1 according to the invention, which differs from the embodiments described above essentially in that the working fluid reservoir 5 is realized as a basin, barrel, canister, or the like 75. For example, a rain barrel 75 installed outdoors has proven to be advantageous. The pump-turbine unit 43 can, for example, draw the working fluid to be introduced into the surface fluid compartment 9 from the basin 75 or be connected to a separate (not shown) working fluid reservoir source. Furthermore, as an alternative to the one described in Figure 1, the pump-turbine unit 43 can be connected to a separate (not shown) working fluid reservoir source. Fig. 9 The design, which is closed at the top towards the environment, has at least one opening towards the environment in the area of ​​the cover 73, through which, for example, rainwater can flow into the upper fluid compartment 9 and which can be used to move the buoyancy piston 23 downwards into the lower fluid compartment 11 arranged in the basin 75 in order to bring the pumped storage power plant 1 into energy charging mode. The working fluid reservoir 5, which is limited by the basin 75, according to Fig. 9 can be described as a closed working fluid reservoir, while those according to the Fig. 1 bis 8 The depicted working fluid reservoirs 5 can be realized as open working fluid reservoirs, like open bodies of water.

[0057] Regarding the Fig. 10 und 11 Two further pumped storage power plants 1 according to the invention are described in accordance with a further aspect of the present invention. The pumped storage power plant 1 comprises a substantially circular cylindrical working cylinder 3 with a working fluid compartment 109 and a counter-working compartment 111 fluidically separated from the working fluid compartment 109. According to the Fig. 10 und 11 The pumped-storage power plant 1 is essentially oriented in the direction of gravity G, so that the working fluid compartment 109 is arranged above the counter-working compartment 111 in the schematic diagrams. The working fluid compartment 109 is separated from the counter-working compartment 111 by a working piston 123 and fluidically sealed against each other, thus preventing fluid exchange between the working fluid compartment 109 and the counter-working compartment 111. The working piston 123 is movable relative to the working cylinder 3 in a working direction A, which according to Fig. 10 und 11 oriented along the direction of gravity G, but generally essentially in the longitudinal direction of the working cylinder 3. When the working piston 123 moves relative to the working cylinder 3, the working piston 123, in simplified terms, performs a movement between or in the direction of the working fluid compartment 109 and the counter-working compartment 111. During an energy charging operation of the pumped storage power plant 1, fluid is admitted into the working fluid compartment 109. This can be done, for example, via a [missing information - likely a specific mechanism or feature] relative to the Fig. 1 bis 9 The discussed pump-turbine unit 43 happened, or as it was described in Fig. 10 The system, shown schematically, is powered solely by a pump (not shown) connected to a piping system 45 that opens into the surface fluid compartment 109 at a piping inlet 47. Similar to the previously described configurations, the working fluid introduced into the working fluid compartment 109 exerts a force on the working piston 123. This force can, for example, be essentially the weight of the working fluid in the working fluid compartment 109. Furthermore, the force can consist, at least in part, of a hydrodynamic pressure force that develops as a result of the flow of the working fluid into the working fluid compartment 109 and presses against an end face 113 on the working fluid compartment side, in order to move the working piston 123 towards the counter-working compartment 111, i.e., essentially into the counter-working compartment 111, while tensioning the working piston 123.The tensioning of the working piston 123 can be achieved, for example, by tensioning an elastic component 115 or, alternatively, by immersing the working piston 123 in a counter-working fluid filled in the counter-working chamber 111. In the latter case, the working piston 123, or its material, should be selected such that a buoyant force is generated on the working piston 123 relative to the counter-working fluid in the counter-working chamber 111. By tensioning the elastic component 115, it builds up a deformation restoring force opposite to the movement of the working piston 123. This restoring force essentially forms the basis of the potential energy that is stored by the pumped-storage power plant 1 and can be made available again in an energy release operation, which is described below. In the energy release operation, under the influence of the tensioning force of the tensioned working piston 123, working fluid is forced out of the working fluid chamber.The working cylinder 3 can be used as described in relation to the . Fig. 1 bis 9 As described, the pump-turbine unit 43 is coupled to the piping system 45 by means of the pump-turbine unit 43, which can be operated in generator mode to drive a power generator that converts mechanical energy into electrical energy. According to the Fig. 10 und 11 In devices where, instead of the pump-turbine unit 43, a pump (not shown) is provided for pumping working fluid into the working fluid compartment 109, the working fluid is transferred via a line 117 to an energy converter during energy output operation. This converter can generate electrical energy from the flow energy of the outgoing working fluid. For example, the line has a connection nozzle 119 at one end for connecting to the energy converter. This converter can be implemented, for example, by filling at least one container, which, by means of a chain-belt mechanism (not shown), converts the weight of the outgoing working fluid into a torque that can be converted into electrical energy by a power generator.

[0058] Both in Fig. 11 as well as in Fig. 10 The tensioning of the working piston 123 is effected by an elastic component 115 designed as a spring. The spring 115 is supported against an end face 121 on the counter-working part side and against a bottom surface 122 of the working cylinder 3, which delimits the counter-working compartment 111 downwards. This occurs in such a way that when the working fluid is introduced into the working fluid compartment 109, the spring 115 is pre-tensioned in the direction of the bottom surface 122 of the working cylinder 3, so that a deformation restoring force builds up against the displacement of the working piston 123 in the working direction A. The introduction of the working fluid into the working fluid compartment 109 and the associated tensioning of the spring or the elastic component 115 takes place by enlarging the working fluid compartment 109, that is, by expanding or extending the working fluid compartment 109 in the direction of the counter-working compartment 111.The opposite occurs when the working fluid is pushed out of the working fluid compartment 109, i.e. during energy output operation.

[0059] According to Fig. 10 Does the working piston 123 have at least two, or as it is described in Fig. 10 The illustration shows four telescopically movable working segments 125 relative to each other in the working direction A. The working segments 125 are arranged and coordinated relative to each other such that when the working fluid is introduced into the working fluid compartment 109, the working segments 125 extend apart, a state partially in Fig. 10 As illustrated, when the working fluid is forced out of the working fluid compartment 109, the at least two, preferably four, working segments 125 move into one another, reducing the size of the working fluid compartment 109 and enlarging the counter-working compartment 111. During this process, the spring 115 presses on the working segment 125 on the counter-working compartment side and pushes it in the working direction A into the other working segments 125. Fig. 10 It is evident that the working piston 123 is attached to the inner surface 127 of the working cylinder by means of a fastening section 129 of the working piston 123. The fastening section 129 remains essentially stationary on the working cylinder 3 during the movement of the working piston 123 within the working cylinder 3. A deformation section 131 adjoins the fastening section 129. This deformation section is characterized by the fact that it expands during operation, i.e., the working segments 125 extend apart, and compresses during energy delivery operation, i.e., the working segments 125 retract into one another. The embodiment according to Fig. 11 differs from the design according to Fig. 10 essentially solely due to the fact that the working piston 223 ( Fig. 11 ) does not consist of telescopically extendable working segments 125 ( Fig. 10 ), but is designed as an elastically deformable working bellows 223 that essentially delimits the working fluid compartment 109. The working bellows 223 is designed such that it expands when the working fluid is introduced into the working fluid compartment 109, specifically in the direction of the counter-working compartment 111. When the working fluid is forced out of the working fluid compartment 109 due to the tension force provided by the spring 115, in particular the deformation restoring force, the elastic working bellows 223 compresses back, reducing the size of the working fluid compartment 109. It may be provided that the working bellows 223 inflates like a balloon and, as the working fluid is introduced into the working fluid compartment 109, pushes or pre-tensions the spring 115 towards the bottom surface 122 of the counter-working compartment 111. Furthermore, a venting device 133 can be integrated into the working fluid compartment 109, for example to allow pressure equalization to the atmosphere.

[0060] In relation to Fig. 12 bis 13 An exemplary further development of a pumped storage power plant 1 according to the invention is shown, wherein with regard to the Fig. 12 a first version of a water castle 77 is shown and in relation to the Fig. 13 A second embodiment of a surge tank 77. The surge tank 77 generally serves to absorb or compensate for pressure surges acting on the pumped-storage power plant 1. This may be necessary, for example, if power output is interrupted, which results in a free-falling column of surface fluid or working fluid being collected to prevent it from impacting a stationary component, such as a component of the pump-turbine unit 43, under the influence of its weight. The surge tank 77 essentially comprises a fluid or compensating line 79 provided in addition to the piping system 45 of the pump-turbine unit 43, into which the working fluid or surface fluid already forced out of the surface fluid compartment 9 or working fluid compartment 109 is to flow in order to prevent damage to the pump-turbine unit 43.The fluid line 79, designed as a hollow pipe, is flooded by the escaping surface fluid or working fluid in such a way that it is carried to a vertical height against the direction of gravity G in order to convert or dissipate the flow energy into potential energy. Fig. 12 Figure 1 shows an embodiment of the water lock 77 with an essentially U-shaped fluid conduit section 81, which couples the fluid conduit 79 with the fluid conduit system 45 of the pump-turbine unit 43 in order to bring the fluid into the fluid conduit 79 and there bring it in a vertical direction against the direction of gravity, so that the flow energy is converted into potential energy.

[0061] When executed according to Fig. 13Instead of the U-shaped arrangement 81 of the water lock 77, a pipe-in-pipe construction of the water lock 77 is implemented, in which the additional fluid line 79 is implemented as a hollow line 83, which essentially surrounds the fluid line system 45 along its entire longitudinal extent, thus forming a closed system, i.e., sealed from the environment. In this construction of the water lock 77 as well, it is provided that the working fluid or surface fluid exiting the surface fluid compartment 9 or working fluid compartment 109 flows into the annular pipe section 85, which is located between the hollow line 83 and the fluid line system 45, and flows therein in a vertical direction against the direction of gravity G in order to convert or dissipate flow energy into potential energy.One advantage of the pumped storage power plant 1 according to the invention lies, for example, in its simple scalability with regard to its size and / or storage capacity. For example, the working cylinder 3 can have a diameter of up to 10 m, preferably in the range of 1 m to 5 m. The total longitudinal extent of the working cylinder 3 can, for example, be up to 100 m, preferably in the range of 20 m to 80 m.

[0062] The scope of protection is defined in the attached claims. Reference symbol list

[0063] 1 Pumped storage power plant 3 Working cylinder 5 Fluid reservoir 7 Fluid level 9 Surface fluid compartment 11 Subsurface fluid compartment 13 Interior 15 End face 17 Opening 19 Shell 21 Through-opening 23 Buoyancy piston 25, 26 Seal 27 Inner shell surface 29 Groove 31 Belly 33, 35 Section 37 Cavity 39 Activation energy source 41 Pipeline 43 Pump-turbine unit 45 Piping system 47, 49 Inlet / outlet 53, 55 Inlet / outlet pipe 57 End face 59 Float / submersible body 61 Surface fluid compartment area 63 Anchoring 65 Base 67 Compensating body 69 Additional body 71 Cable construction 73 Cover 75 Basin 77 Water seal 79 Fluid line 81 U-shaped fluid line 83 Hollow line 85 Ring-shaped pipe section 109 Working compartment 111 Counter-working compartment 113 End face 115 Elasticity component 117 Line 119 Connection 121 End face 122 Bottom face 123 Working piston 125 Working segment 127 Inner shell surface 129 Mounting section 131 Deformation section 133 Venting device 223 Working bellows G Gravitational direction V Displacement direction R Radial direction A Working direction

Claims

1. Pumped storage power plant (1) comprising: - a working cylinder (3) partially immersed in a working fluid reservoir (5), such as a water reservoir, with an upper fluid compartment (9) substantially above a fluid level (7) of the working fluid reservoir (5) and a lower fluid compartment (11) substantially below the fluid level; - a buoyancy piston (23) which is movably guided with respect to the working cylinder (3) in the direction of gravity (G) and seals the upper fluid compartment (9) from the lower fluid compartment (11) in such a way that a gravitational fluid exchange between the upper fluid compartment (9) and the lower fluid compartment (11) is prevented; - an energy charging mode in which working fluid is admitted into the upper fluid compartment (9), so that under the influence of the weight force and / or the dynamic pressure of the upper fluid admitted into the upper fluid compartment (9), the buoyancy piston (23) is immersed in the lower fluid compartment (11) with respect to the fluid level (7); and - an energy output mode in which under the influence of the buoyancy force of the buoyancy piston (23), upper fluid is pushed out of the upper fluid compartment (9) and / or in which a fluid column of the upper fluid built up during the energy charging mode preferably flows off constantly from the upper fluid compartment (9).

2. Pumped storage power plant (1) according to Claim 1, wherein, in order to seal the upper fluid compartment with respect to the lower fluid compartment (11), at least one seal (25, 26) is arranged between the buoyancy piston (23) and the working cylinder (3), preferably in the area of the fluid level, and can be activated, in particular can be acted on hydraulically and / or pneumatically, in such a way that the at least one seal (25, 26) holds the buoyancy piston (23) in place relative to the working cylinder (3), preferably in the energy charging mode and / or in the energy output mode of the pumped storage power plant (1), wherein, in particular, the at least one seal (25, 26) is received in a groove (29) formed on a casing inner surface (27) of the working cylinder (3) and / or a casing outer surface of the buoyancy piston (23), wherein the at least one seal (25, 26) expands in the direction of the buoyancy piston (23) and / or of the working cylinder (3) when it is activated, in order to build up a holding force, such as a frictional force and / or a force caused by a form fit, between the buoyancy piston (23) and the working cylinder (3), preferably continuously.

3. Pumped storage power plant (1) according to Claim 2, wherein an activation of the at least one seal (25, 26) and a displacement of the buoyancy piston (23) between the energy charging mode position and the energy output mode position are coordinated with one another and / or wherein an activation energy source (39), such as a pneumatic, electronic and / or hydraulic source, is fluidically and / or electrically connected to the at least one seal (25, 26), in order to activate or deactivate the at least one seal (25, 26), in particular to act on it with activation fluid or current, wherein, in particular, the activation energy source (39) is coupled to a control and / or regulating device for preferably automated control and / or regulation of the activation energy source (39), in particular for activating or deactivating the at least one seal.

4. Pumped storage power plant (1) according to one of the preceding claims, wherein at least one prestressing seal (25, 26) seals the buoyancy piston (23) and the working cylinder (3) with respect to one another at an end of the buoyancy piston (23) facing away from the lower fluid compartment (11) and can be operated in such a way that, in the energy output mode position of the buoyancy piston (23), the at least one prestressing seal (25, 26) is activated in order to build up a predetermined upper fluid column in such a way that the weight force of the upper fluid continuously exceeds the buoyancy force of the buoyancy piston (23) with respect to the working fluid when displacing the buoyancy piston (23) as far as a final energy charging mode position.

5. Pumped storage power plant (1) according to one of the preceding claims, wherein the buoyancy piston (23) and / or the working cylinder (3) is coupled to at least one additional body, for example a floating body, immersion body and / or buoyancy body, arranged outside the working cylinder (3) and at least partially immersed in the working fluid reservoir (5), preferably by means of a cable construction (71), wherein, in particular, the additional body communicates a force component directed counter to the weight force of the upper fluid to the buoyancy piston (23), wherein, in particular, the force component counteracts a displacement of the buoyancy piston (23) from the energy output mode position into the energy charging mode position.

6. Pumped storage power plant (1) according to one of the preceding claims, wherein a pump-turbine unit (43) arranged, in particular, outside the working fluid reservoir (5) pumps working fluid into the upper fluid compartment (9) in the energy charging mode, wherein, in particular, the pump-turbine unit (43) is configured to be able to be operated in a generator mode when adopting the energy output mode, in particular in order to convert flow energy of the upper fluid pushed out of the upper fluid compartment (9) into mechanical energy, in particular in order to drive a current generator.

7. Pumped storage power plant (1) according to one of the preceding claims, wherein the working cylinder, in particular the upper fluid compartment, is closed or at least partially open on a side facing away from the lower fluid compartment (11) and / or wherein the working cylinder (3) is arranged in a freely floating manner in the working fluid reservoir (5) or is fixedly anchored in a base (65) of the working fluid reservoir (5) and / or wherein a buoyancy force of the buoyancy piston (23) with respect to the working fluid arranged in the working fluid reservoir (5) is greater than the weight force of the upper fluid in a final energy output mode position of the buoyancy piston (23) for bringing the buoyancy piston (23) into the energy charging mode position, wherein, in particular, the pump-turbine unit (43) is configured to overcome the excess buoyancy force.

8. Pumped storage power plant (1) comprising: - a working cylinder (3) with a working fluid compartment (109) and a counter-working compartment (111), - a working piston (123) which can be moved with respect to the working cylinder (3) in a working direction (A) and seals the working fluid compartment (109) from the counter-working compartment (111) in such a way that fluid exchange between the working fluid compartment (109) and the counter-working compartment (111) is prevented; - an energy charging mode in which fluid is admitted into the working fluid compartment (109), so that under the influence of the fluid pressure and the weight force of the working fluid admitted into the working fluid compartment (109), the working piston (123) is moved into the counter-working compartment (111) while tensioning the working piston (123), preferably while tensioning an elasticity component (115) on the working piston (123) or immersing the working piston (123) in a counter-working fluid filled in the counter-working compartment (111); and - an energy output mode in which under the influence of the tensioning force of the tensioned working piston (123), working fluid is pushed out of the working fluid compartment (109) and / or in which a fluid column of the working fluid built up during the energy charging mode preferably flows off constantly from the working fluid compartment (109).

9. Pumped storage power plant (1) according to Claim 8, wherein the working piston (123) is tensioned under the influence of the weight force of the working fluid and / or wherein the working piston (123) is configured to deform, in particular expand, when admitting the working fluid into the working fluid compartment (109) while enlarging the working fluid compartment (109), and to deform, in particular compress, back when pushing the working fluid out of the working fluid compartment (109) while reducing the size of the working fluid compartment (109).

10. Pumped storage power plant (1) according to either of Claims 8 and 9, wherein the working piston (123) has at least two working segments (125) which can be displaced telescopically with respect to one another in the working direction (A) and which extend apart when admitting the working fluid into the working fluid compartment (109) and retract into one another when pushing the working fluid out of the working fluid compartment (109), wherein in particular the working fluid compartment (109) is delimited substantially by the at least two working segments (125) and / or wherein the working piston (123) comprises an elastically deformable working bellows (223) which delimits substantially the working fluid compartment (109) and expands when admitting the working fluid into the working fluid compartment (109) and compresses when pushing the working fluid out of the working fluid compartment (109).

11. Pumped storage power plant (1) according to one of Claims 8 to 10, wherein a tensioning force builds up when tensioning the working piston (123) and / or the working piston (123) is tensioned by a spring, wherein in particular the spring is supported on a counter-working-compartment-side end face of the working piston (123) and on a bottom surface of the working cylinder (3) delimiting the counter-working compartment (111), in particular is supported in such a way that, when admitting the working fluid into the working fluid compartment (109), the spring is prestressed in the direction of the bottom surface of the working cylinder (3).

12. Method for operating a pumped storage power plant (1), in which - for storing energy, working fluid is filled into an upper fluid compartment (9) of a working cylinder (3) partially immersed in a working fluid reservoir (5), wherein the upper fluid compartment (9) lies above a fluid level (7) of the working fluid reservoir (5) and is fluidically separated from a lower fluid compartment, which lies substantially below the fluid level (7), by a buoyancy piston (23), wherein under the influence of the weight force and / or the dynamic pressure of the upper fluid admitted into the upper fluid compartment (9), the buoyancy piston (23) is immersed in the lower fluid compartment (11) with respect to the fluid level (7); and - for outputting the energy, the upper fluid is pushed out of the upper fluid compartment (9) by the buoyancy piston (23) using a buoyancy force of the latter and / or can flow off from a constant height.

13. Method for operating a pumped storage power plant (1), in which - a working cylinder (3) is fluidically divided into a working fluid compartment (109) and a counter-working compartment (111) by means of a working piston (123); - for storing energy, working fluid is filled into the working fluid compartment (109), so that under the influence of the fluid pressure and the weight force of the working fluid admitted into the working fluid compartment (109), the working piston (123) is moved into the counter-working compartment (111) while tensioning the working piston (123), preferably while tensioning an elasticity component (115) on the working piston (123) or immersing the working piston (123) in a counter-working fluid filled in the counter-working compartment (111); and - for outputting energy, the working fluid filled in the working fluid compartment (109) is pushed out of the working fluid compartment (109) using a buoyancy force of the working piston, such as a tensioning force of an elasticity component (115) on the working piston (123) and / or a buoyancy force of the working piston immersed in a counter-working fluid filled in the counter-working compartment (111), and / or can flow off from a constant height.

14. Method according to Claim 12 or 13, which is designed to realize the pumped storage power plant (1) according to one of Claims 1 to 11.

15. Pumped storage system, preferably offshore pumped storage system or onshore pumped storage system, comprising at least two pumped storage power plants (1) which are fluidically coupled to one another and are designed according to one of the preceding Claims 1 to 11.