Abstract: A variable speed wind turbine including a variable speed rotor, a large constant speed generator, and a small variable speed generator is characterized by a three-shaft variable ratio gearbox connecting the shaft of the rotor with the two generator shafts. The variable ratio gearbox is an epicyclic gearbox which enables the combination of the high performance of a variable speed rotor with the low cost of a large constant speed generator. The torque of the small variable speed generator controls the rotor speed. Variable frequency power conditioning cost is less than that of a prior art variable speed wind turbine, reduced by the ratio of the rated capacity of the small generator to total rated capacity. Also, the small generator enables efficient low wind velocity energy capture. The low rotational inertia of the small variable speed generator further reduces drive train dynamic stress.

Abstract: A variable speed wind turbine including a variable speed rotor, a large constant speed generator, and a small variable speed generator is characterized by a three-shaft variable ratio gearbox connecting the shaft of the rotor with the two generator shafts. The variable ratio gearbox is an epicyclic gearbox which enables the combination of the high performance of a variable speed rotor with the low cost of a large constant speed generator. The torque of the small variable speed generator controls the rotor speed. Variable frequency power conditioning cost is less than that of a prior art variable speed wind turbine, reduced by the ratio of the rated capacity of the small generator to total rated capacity. Also, the small generator enables efficient low wind velocity energy capture. The low rotational inertia of the small variable speed generator further reduces drive train dynamic stress.

Abstract: A hybrid power generator is characterized by the combination of a wind turbine and a combustion engine to drive a generator. The wind turbine and combustion engine are each connected with the generator via a drive train. Each drive train preferably includes a gearbox and a clutch, with the clutches being operated by a controller to determine which of the wind turbine and combustion engine are connected with the generator. Preferably, under high wind conditions, only the wind turbine is connected with the generator to produce electricity for delivery to a power grid via a converter. During periods of peak demand and low or no wind conditions, the combustion engine is connected with the generator. It is also possible to connect the wind turbine and combustion engine with the generator at the same time. Also, a differential at the input to the generator can compensate for the different rotary speed outputs from the wind turbine and the combustion engine.

Abstract: A fin-type compound parabolic concentrator includes a pair of semi-parabolic reflectors arranged on opposite sides of a common plane, the reflectors having a common focal point on the plane and being rotated through an angle defined by a line extending from the apex of each reflector through the focal point. A generally arcuate bottom reflector having a center line within the common plane is connected with the semi-parabolic reflectors. A bi-facial photovoltaic absorber is arranged in the common plane and extends from the focal point to the bottom reflector for absorbing rays of sunlight directed thereon from the reflectors. The absorber has a critical angle below which rays directed thereon will be substantially absorbed and above which rays directed thereon will be substantially reflected and the bottom reflector is configured to limit the angle of rays that strike said absorber to less than said critical angle.