Renold Clutches & Couplings has helped to design a novel transmission system for wind power turbines that makes them lighter and more efficient in operation. Renold’s team modified an overrunning sprag clutch and vee pulley assembly connected to a gearbox via a Renoldflex torsionally rigid coupling. The gearbox is able to change the pitch angle of the turbine’s rotors in different wind conditions.
Conventional wind turbines normally employ fixed-speed rotors and in high wind conditions they have to contend with large torque fluctuations that can cause power output variations, through the generator, of up to 100%. The new design counters this problem by employing a novel gearbox and clutch combination that allows rotor speed adjustment through variations in the pitch angle of the blades. This enables power output, through the generator, to be maintained at a constant level regardless of fluctuations in wind speed. In cases of over-speed, the rotor reaches a fully feathered position and cuts out, but the clutch allows the generator to continue running.
A conventional system requires extremely heavy and robust assemblies in order to contend with the large fatigue loads in high wind conditions. The new design, which incorporates a swept blade diameter of 33m, can attain speeds of 50rpm and is about 50% lighter than conventional wind turbines. This improves the cost-to-weight ratio and reduces operating costs as only 3% of rated power is consumed by the components.