The invention provides an energy storage system (1) for storing energy in a waterbody (2), such as a sea, an ocean, a waterway, etc. The energy storage system comprises a reservoir structure (8A, 8B, 8C, 9A, 9B, 9C) for a working liquid (7) and an energy storing and retrieving subsystem (10A, 10B). The working liquid (7) in the reservoir structure is completely separated from the water (6) of the waterbody. The reservoir structure comprises a deformable pressurizing subreservoir (8A), which is extending in the waterbody, and which has a liquid-impermeable deformable wall structure (18). The reservoir structure further comprises a buried depressurizing subreservoir (9A), which is an artificial structure, which has been buried under a vertical column of a waterbody underground (5). The energy storage system provides, inter alia, improved energy storage capacity and improved reliability, as well as reduced operational costs and reduced environmental disturbance.

The invention concerns a method for starting a hydroelectric turbine (10) in a pumping mode, said turbine being provided with a runner (6) mechanically coupled to a shaft line (8) and a variable speed electric motor connected to a grid, a distributor (4) comprising guide vanes to control a flow of water to said runner, the method comprising: a) a step of operating the variable speed motor at least partly at fixed speed, said guide vanes being only partially opened, and of defining or calculating: data of a plurality of hydraulic characteristics (C.sub.1, C.sub.2, C.sub.i) of the turbine for an operation without cavitation; data of an operation range of the electric motor, giving the speed of the motor as a function of its power; b) then a step of operating the turbine in a power control mode.

The invention concerns a method for starting a hydroelectric turbine (10) in a pumping mode, said turbine being provided with a runner (6) mechanically coupled to a shaft line (8) and a variable speed electric motor connected to a grid, a distributor (4) comprising guide vanes to control a flow of water to said runner, the method comprising: a) a step of operating the variable speed motor at least partly at fixed speed, said guide vanes being only partially opened, and of defining or calculating: data of a plurality of hydraulic characteristics (C.sub.1, C.sub.2, C.sub.i) of the turbine for an operation without cavitation; data of an operation range of the electric motor, giving the speed of the motor as a function of its power; b) then a step of operating the turbine in a power control mode.

The present invention generally relates to hydraulic machinery, such as hydraulic turbines. More specifically, the invention is directed to optimizing power consumption when the turbine is used in condenser mode. The present invention provides a novel hydraulic installation where the reduction of pressure in the spiral case during condenser mode operations is more efficient, limiting the power consumption if compared to state-of-the-art installations.

The present invention provides improved methods, apparatus, and manufacture for an Archimedes Screw using a strake design as a blade to increase the volume of water raised or lowered by about 10%. The invention, in part, alters the shape of the blades within the screw from a helicoid shape to a strake shape. A helicoid blade in an Archimedes Screw has been used since antiquity and has not changed since then, limiting the efficiency and manufacturing process. The strake shape allows a greater quantity of water to be contained within the screw and is a developable surface that enables easier fabrication than the helicoid shape.

An electric machine is presented. The electric machine includes a hollow rotor; and a stator disposed within the hollow rotor, the stator defining a flow channel. The hollow rotor includes a first end portion defining a fluid inlet, a second end portion defining a fluid outlet; the fluid inlet, the fluid outlet, and the flow channel of the stator being configured to allow passage of a fluid from the fluid inlet to the fluid outlet via the flow channel; and wherein the hollow rotor is characterized by a largest cross-sectional area of hollow rotor, and wherein the flow channel is characterized by a smallest cross-sectional area of the flow channel, wherein the smallest cross-sectional area of the flow channel is at least about 25% of the largest cross-sectional area of the hollow rotor. An electric fluid pump and a power generation system are also presented.

A power unit including an enclosed housing, a shaft passing through the central section of the enclosed, a motor located outside the housing and mounted to the first end of the shaft, a turbine located inside the housing and mounted into the shaft, the turbine includes a hub, a top end, a bottom end, and blades, sealing fins located at the bottom end of the turbine; and a pump located inside the housing and mounted on the turbine. The pump includes fins that are inserted in grooves located on the hub of the turbine. The fins of the pump are joined to the blades of the turbine creating that the pump, turbine, and shaft move as unitary unit. The fins of the pump maintained by two spaced crowns by insertion form cells that guide a flow of fluid. A space free of fluid with a defined volume occupies the bottom end of the pump. In a non-working position, the space free of fluid has a cylindrical shape. In a working position, because of rotation of the fluid, the space free of fluid has a paraboloid shape. The rotation of the fluid at a minimum angular velocity creates a virtual barrier, and generates a thrust.

A device and method for converting electric energy into pneumatic energy and vice versa, which involves: pumping a liquid forming a liquid piston into a conversion chamber in which a quantity of air is trapped until the air reaches a pressure of a compressed air storage vessel; or churning a liquid by expanding the compressed air in a conversion chamber which is filled with a quantity of liquid, in which device or method the pumping or the churning of the water takes place in the same conversion chamber and consecutively in at least two pumping or churning stages, respectively, provided so as to operate in different pressure ranges. The present device and method can be used in particular in the field of converting and storing electric energy.

Some embodiments are directed to a system for generating waves in a pool, including, in the region of at least one wall of the pool, at least one water intake mouth connected to a supply source by means of a network of pipes, the network of pipes including at least one pump capable of alternately transferring water from the supply source to the pool and vice versa, the pump being controlled so as to generate, in the region of the water intake mouth, an oscillating flow alternately oriented towards the pool and then towards the supply source.

A pumped storage hydropower apparatus includes a housing and at least one pump disposed within the housing. The at least one pump is configured to operate in a first mode of operation or a second mode of operation based on an operation condition including at least one of a time or a price of electrical power from a remote electrical power source. In the first mode of operation, the at least one pump receives a first flow of water from a first water storage unit, transports the first flow to a second water storage unit, and generates electrical power for transmission to the remote electrical power source. In the second mode of operation, the at least one pump receives a second flow of water from the second water storage unit, and transports the second flow to the first water storage unit using electrical power from the remote electrical power source.