A high-pressure compressor having a hydraulic system and a gas chamber, where the hydraulic system includes a reservoir, connected to a hydraulic fluid chamber by a hydraulic flow path and a pump assembly positioned in the hydraulic flow path, and the compressor furthermore includes a control element controlling the flow of hydraulic fluid in the hydraulic flow path and thereby the pressure in the hydraulic fluid chamber, where the control element and the pump assembly is configured for controlling the pressure of hydraulic fluid in the hydraulic fluid chamber when the compressor is not in operation.

A method and an apparatus for controlling noise of multiple wind turbines. The method includes: determining a noise-influencing sector of each of the multiple wind turbines, based on positions of the multiple wind turbines and a position of a noise-influencing site; acquiring a current wind direction; determining whether there is at least one wind turbine of the multiple wind turbine under the current wind direction operating in the noise-influencing sector; and limiting output power of the at least one wind turbine, in a case that the determination is positive.

An aquifer storage and recovery system can include a pump, an electric motor coupled to the pump, a drive unit configured to control operation of the electric motor, and a controller. The controller can be configured to flow water into a well bore from a source reservoir through the pump such that the pump rotates in a reverse direction and drives the electric motor coupled to the pump in the reverse direction to operate as a generator, determine a power output of the electric motor, determine a difference between the power output of the electric motor and a power output set point, and operate the drive unit to control a rotational speed of the electric motor based at least in part on the difference between the power output of the electric motor and the power output set point.

A method of controlling a wind turbine, wherein a minimum required hydraulic pressure represents a hydraulic pressure of at least one accumulator of the wind turbine which is required to pitch at least one blade of the wind turbine which is associated with the accumulator into a stop position of the wind turbine, and wherein a pitch angle represents a pitch angle of a normal of the at least one blade of the wind turbine relative to an incoming wind direction. The method includes (a) determining a minimum requirement function of the minimum required hydraulic pressure dependent on the pitch angle, (b) detecting a current hydraulic pressure in the at least one accumulator at a current pitch angle of the at least one blade, and (c) controlling the wind turbine such that the current hydraulic pressure is above the minimum required hydraulic pressure at the current pitch angle.

A measuring device for wave energy conversion performance of a comb-typed permeable breakwater with arcuate walls is provided. The measuring device includes four parts: the comb-type permeable breakwater with arcuate walls, a wave height measuring instrument and pressure sensor fixing and adjusting apparatus, a wave height measuring instrument data collecting and processing apparatus and a pressure sensor data collecting and processing apparatus. The comb-typed permeable breakwater includes combined arc-shaped caissons, partition plates, a back plate, a fixing bottom plate and fixing screws. The wave height measuring instrument data collecting and processing apparatus processes data collected by a wave height measuring instrument and outputs for display. The pressure sensor data collecting and processing apparatus analyzes data collected by a pressure sensor and outputs for display. The measuring device has a stable structure, convenient operation and high experimental accuracy.

In one embodiment, a method includes determining, by a controller, a first wind pressure associated with a first port of a first probe, determining, by the controller, a second wind pressure associated with a second port of the first probe, and determining, by the controller, a reference wind pressure associated with an end portion of the first probe. The method also includes calculating, by the controller, a first reference differential using the first wind pressure and the reference wind pressure, calculating, by the controller, a first rotational differential using the first wind pressure and the second wind pressure, and calculating, by the controller, an angular coefficient using the first reference differential and the first rotational differential. The method further includes calculating, by the controller, a wind velocity using the first reference differential and the angular coefficient. The wind velocity represents a wind velocity relative to a vehicle.

A structure adapted to traverse a fluid environment exerting an ambient fluid pressure is provided. The structure includes an elongate body extending from a root to a wingtip and encapsulating at least one interior volume containing an interior fluid exerting an interior fluid pressure that is different from the ambient fluid pressure. A method of retrofitting a structure adapted to traverse a fluid environment exerting an ambient fluid pressure, the structure comprising an elongate body extending from a root to a wingtip and having at least one interior volume is also provided. The method includes sealing the elongate body to encapsulate the at least one interior volume containing an interior fluid; associating at least one valve with the at least one interior volume; and modifying interior fluid content via the at least one valve to produce an interior fluid pressure that is different from the ambient fluid pressure.

An aquifer storage and recovery system can include a pump, an electric motor coupled to the pump, a drive unit configured to control operation of the electric motor, and a controller. The controller can be configured to flow water into a well bore from a source reservoir through the pump such that the pump rotates in a reverse direction and drives the electric motor coupled to the pump in the reverse direction to operate as a generator, determine a power output of the electric motor, determine a difference between the power output of the electric motor and a power output set point, and operate the drive unit to control a rotational speed of the electric motor based at least in part on the difference between the power output of the electric motor and the power output set point.

Provided is a method of detecting a leak in a hydraulic cylinder of a rotor blade pitch system of a wind turbine including a plurality of rotor blades, which method includes the steps of selecting one of the pitch systems to undergo a functionality test; actuating a fluid pump to move the pistons of the hydraulic cylinders of the pitch systems to their outermost positions; monitoring the hydraulic cylinder pressure levels of the non-selected pitch systems while performing the functionality test on the selected pitch system; and analyzing the monitored hydraulic cylinder pressure levels of the pitch systems to detect a drop in pressure in a pitch cylinder of a non-selected pitch system. A leak detection arrangement of a pitch-controlled wind turbine; and a pitch-controlled wind turbine are also provided.

A compressor assembly for a portable oxygen concentrator includes a first compressor chamber having a first connector, a second compressor chamber having a second connector, and a tube having a first end having a first connection interface configured to connect to the first connector and a second end having a second connection interface configured to connect to the second connector. The first connection interface is shaped to maintain the connection between the first connector and the first connection interface in a fixed orientation and the second connection interface is shaped to maintain the connection between the second connector and the second connection interface in a fixed orientation. One or more of the first connector, the second connector, and the tube are compliant.