A method for starting a motor having a stator and a rotor is provided. The method includes starting a motor with field coils of the stator being in Y connection, switching the connection of the field coils to Δ connection when the speed of the rotor does not fall within a predetermined range from a rated speed within a predetermined time (t2), and switching the connection of the field coils to the Y connection when the speed of the rotor falls within the predetermined range from the rated speed.

A water reservoir system for generating, accumulating, storing, and releasing electrical energy comprises a reservoir wall built in a shallow body of water such as a sea or an ocean with a height exceeding the outside water level by about 10-25 m, thereby defining an interior of the water reservoir. Excess electrical energy from other renewable sources of electricity such as wind, solar power, or supplied by a local power grid is used to operate water pumps to fill the interior of the water reservoir with water during times of peak supply of electricity. Water is drained from the water reservoir to the outside body of water and generates electrical energy by flowing over a plurality of water turbines, thereby generating electricity and supplementing electrical power for the local power grid during times of high demand. Additional interior sources of renewable energy may be used to supplement external sources of electrical power in operating the system of the invention.

A floating power-generation group comprises a floating hub such as a spar buoy that is anchored to subsea foundations by anchor lines. Floating power producer units such as wind turbines are connected electrically and mechanically to the hub. The power producer units are each moored by mooring lines. At least one mooring line extends inwardly toward the hub to effect mechanical connection to the hub and at least one other mooring line extends outwardly toward a subsea foundation. The groups are combined as a set whose hubs are connected electrically to each other via subsea energy storage units. Anchor lines of different groups can share subsea foundations. The storage units comprise pumping machinery to expel water from an elongate storage volume and generating machinery to generate electricity from a flow of water entering the storage volume. The pumping machinery may be in deeper water than the generating machinery.

Methods and systems of operating a gas turbine engine in a low-power condition are provided. In one embodiment, the method includes supplying fuel to a combustor by supplying fuel to a first fuel manifold and a second fuel manifold of the gas turbine engine. The method also includes, while supplying fuel to the combustor by supplying fuel to the first fuel manifold: stopping supplying fuel to the second fuel manifold; and supplying pressurized air to the second fuel manifold to flush fuel in the second fuel manifold into the combustor and hinder coking in the second fuel manifold and associated fuel nozzles.

A subterranean energy storage system configured to store and subsequently release potential energy. Storage of potential energy is achieved by the transfer of a pseudo fluid from a first storage tank to a second storage tank located above the first storage tank, and is subsequently released by the transfer of the pseudo fluid from the second storage tank to the first storage tank. To transfer the pseudo fluid between the first and second storage tanks, the subterranean energy storage system comprises at least one continuous conveyor mechanism extending through at least one transport shaft, wherein the at least one continuous conveyor mechanism comprises a plurality of vessels arranged along a length of the continuous conveyor mechanism. The subterranean energy storage system further comprises an energy transfer means operably connected to the at least one continuous conveyor mechanism to transfer power to and from the subterranean energy storage system.

A reactive blade turbine system works vertically, horizontally, or at an angle and clockwise or counterclockwise according to blade angle and locking position and adjusts to variations in fluid flow such as changes in tidal currents to generate power more efficiently regardless of direction of fluid flow.

A system for energy storage and electricity generation is described. The system includes an energy storage system providing compressed air and an electricity generation system. The electricity generation system includes an airlift pumping system pneumatically coupled to the energy storage system. The airlift pumping system includes a water collecting tank containing collecting water and a riser tube having a base immersed in the collecting water and configured for injection of the compressed air into the riser tube through the air pipeline to provide air bubbles within the riser tube that produce an upward flow of the collecting water together with the air bubbles. The electricity generation system also includes a hydro-electric power system driven by upward flow of the collecting water together with the air bubbles to produce electricity, and a water heating system for heating the collecting water in the water collecting tank.

An energy facility that generates energy using ballistic optimized hydro-electricity. The facility sends a plurality of specialized balls from a lower storage reservoir to an upper storage reservoir. The balls fall through a drop-down system and into a power generation system with a generator and a turbine. Ballistic impacts of the balls on the turbine generate electricity before the balls are returned to the lower storage reservoir.

The disclosure concerns a fan wheel, including a base body with a rotational axis, and a swing part. The base body is made of a first material and the swing part is made of a second material. The density of the second material and the density of the first material are different. The swing part has a surface. The swing part is at least partially surrounded by the base body, so that the base body covers at least 80%, in particular at least 90%, preferably at least 95% of the surface of the swing part. The first material has a first thermal expansion coefficient, and the second material has a second thermal expansion coefficient. The second thermal expansion coefficient amounts to 70% to 110%, in particular 80% to 100%, preferably 85% to 95% of the first thermal expansion coefficient, and/or the swing part is substantially annular and runs fully closed around the rotational axis.

An energy island system arranged related to a body of water with a seafloor, a surface and a depth over an underground is disclosed. The system comprises a structurally rigid shell (1) extending from the seafloor to above the water surface, inclosing a lagoon of the body of water, material with a negative buoyancy stacked around the shell (1) forming a gravity stabilized wall (2), and a tunnel (5) established in the wall (2), providing for hydraulic communication between the surrounding body of water and the interior of the shell (1). Further, a method for construction of an energy island is disclosed.