Energy is harvesting from fluids with different densities, such as water (34) and air (38) with a rotor (12) that is selectively above and below a water surface (30). The rotor (12) has cavities (31,32) inside tubes (18) with apertures (24) in walls (22) of the tubes (18). In a submerged mode, with the rotor (12) in the water (34), air is trapped in tubes (18) on one side of the rotor (12), which has apertures (24) facing down and air is released from the tubes (18) on the opposite side of the rotor (12), which has apertures (24) facing up. The opposite happens in an elevated mode.

A wave energy conversion cylinder includes an outer cylinder and a center rod disposed along an axis of the outer cylinder. A plurality of electrically-conductive windings are disposed about an inner circumference of the outer cylinder. A magnet is slidably disposed on the center rod. A buoyancy cylinder is disposed outwardly of the outer cylinder. A first moveable ring weight may be slidably disposed along the axis of the center rod and a second moveable ring weight may be slidably disposed along the axis of the center rod. The first moveable ring weight and the second moveable ring weight facilitate control to tune a mass moment of inertia of the wave energy conversion cylinder.

A wave energy converter (10) is capable of floating on a body of water (BW), moving in response to waves (W) occurring in the body of water (BW), and includes a hull (12) connected to a heave plate (14). The wave energy converter (10) is characterized in that the hull (12) is formed from reinforced concrete, a plurality of connecting tendons (16) extend between the hull (12) and the heave plate (14), and a power take off (66) is attached to each connecting tendon (16).

A self-supporting nacelle structure for wind turbines, adapted to house a transmission assembly, includes a first shaft connected to a wind turbine rotor hub and to a gearbox, and a second shaft connected to the gearbox and to a generator. The nacelle structure further includes a tubular outer shell defining delimiting a space for housing the transmission assembly, a vertical tubular extension with an upper end edge connected to the outer shell and a lower end edge secured to a tower, an inner frame secured to the outer shell and having a plurality of transverse ribs and a plurality of longitudinal ribs joining the transverse ribs, each transverse rib extending in a closed path, completely enclosing the transmission assembly. The outer shell has a portion with a closed cross section, with at least one transverse rib secured thereto to provide the structure with high torsional and flexural stiffness.

An apparatus for generating energy from ocean waves, the apparatus including a first or outer section arranged to be coupled to a sea floor and a second or inner section that is at least partially received by and slidably moveable within the first section. The first section includes a float housing arranged to be located toward or at a sea surface and an armature housing extending from the float housing toward the sea floor, the float housing having one or more apertures so that a water level within the float housing is substantially similar to or follows that of the sea surface. The second section includes a float slidably received by the float housing and a stem carrying a magnetic element that extends from the float so as to be receivable by the armature housing. The arrangement is such that the float travels in substantially vertical direction within the float housing in response to movement of the sea surface thereby the armature housing being moved relative to the magnetic element to generate energy.

Method for retrofitting a lightning protection device of a rotor blade of a wind turbine. In the method, a cable section of a lightning protection cable is stripped of insulation. A connection piece and a lightning protection receptor are fitted to the cable section which is stripped of insulation, so that the lightning protection receptor is electrically coupled to the lightning protection cable. The invention also relates to a rotor blade which is retrofitted using the method. The risk of lightning strikes in specific regions of a rotor blade can be reduced by the invention by means of the retrofitting operation.

A vessel may be disposed in a body of water. At equilibrium, the water level inside the vessel may be equal to the water level of the body of water. Water may be forced through an outlet from the vessel into the body of water, which decreases the water level inside the vessel. A valve on the outlet may be closed to store the potential energy of the system. When energy is desired, a valve may be opened. Water may flow into the vessel through an inlet, turn a turbine, and generate electricity.

Provided are a rotary device for fluid power generation and a fluid power generation device that are capable of converting the kinetic energy of a fluid to an electric energy. By utilizing a longitudinal vortex as a driving force, a rotary body such as a cylinder as a high-strength and tough wing-shaped member can be rotated, and power can be efficiently generated in a wide range of flow rate without letting the longitudinal vortex disappear even if the flow rate changes in a wide range. This rotary device for power generation includes a rotary body 3; and a wake body 8 that is a distance away from the rotary body 3 toward the downstream side of a flow direction 10 of the fluid, and has at least one crossover section at which the wake body 8 intersects with the rotary body 3.

A wave energy conversion cylinder includes an outer cylinder and a center rod disposed along an axis of the outer cylinder. A plurality of electrically-conductive windings are disposed about an inner circumference of the outer cylinder. A magnet is slidably disposed on the center rod. A buoyancy cylinder is disposed outwardly of the outer cylinder. A first moveable ring weight may be slidably disposed along the axis of the center rod and a second moveable ring weight may be slidably disposed along the axis of the center rod. The first moveable ring weight and the second moveable ring weight facilitate control to tune a mass moment of inertia of the wave energy conversion cylinder.

A low-head and high flow water turbine machine comprises a water-guiding base having a top plate, a bottom plate, an accommodating space defined therein, an inlet and an outlet respectively arranged at upstream side and downstream side, and a first and a second lateral plates respectively having a first and a second water-guiding walls that are respectively extending inward toward circumference of the accommodating space, a water turbine arranged in the accommodating space and having multiple blades, and a cylindrical-shaped gate shell passing through the top plate and slidably coupled to circumference of water turbine around upstream side wherein an opening degree is adjusted through sliding the gate shell for adjusting cross-sectional area of stream thereby controlling stream discharge entering to the water turbine, switching off rotation of the water turbine, and adjusting water level at high water level state at upstream side according to the stream discharge requirement.