Water Current Turbines for River Applications - Alaska Energy ...

WCT EvaluationNRCan-06-01071CycloTurbine - BOSCH AEROSPACE (USA)Technology: The CycloTurbine, a form of Cycloidal Turbine, is in essence a paddle wheel witharticulating blades. The blades are long, straight, non-varying in width and symmetrical. They arearranged in parallel around the perimeter of a wheel forming a squirrel cage-like arrangement. Theblades could be oriented vertically or horizontally. The need for bearings at the far end of the blades isdictated by the length and flexibility of the blade. The pitches of the blades vary independently fromone another as the turbine rotates in the stream. This allows the blades’ individual lift and drag to beoptimized, giving the system its best overall performance. The turbine has the advantage of workingwithout high head pressures. The CycloTurbine works by placing a blade broadside to the flow whilethe opposing blade is feathered to the local flow. The illustration below shows the blade positions of ahorizontal Cyclo Turbine. At all other locations the angle-of-attack of each blade is optimized toproduce the maximum power. The maximum power occurs when the turbine tip-speed is equal to 1/3the flow speed. In a vertical blade arrangement, the generator and bearings could be situated abovewater which has great advantages for accessibility during maintenance. It also reduces the complexityand number of water seals. The efficiency can be increased by installing a ramp to “shade” the bottomof the turbine which is moving upstream against the current. An unducted prototype turbine wasmeasured to have an efficiency of 39.6% and a water to wire efficiency of 29.3%.Application: These turbines would work in rivers, tidal estuaries, and in manmade canals. Thehorizontal application is particularly well suited to shallow rivers. The system could operate in tidalapplications by reversing the pitch control pattern.Stage of Development: A small hydro CycloTurbine was demonstrated in a laboratory setting in thesummer of 2002. The development of the CycloTurbine for its primary application in vertical lift-offaircraft has been moving forward steadily since 2001. In 2006 a new hydro prototype is beingconstructed which replaces the belt drive with gears which should increase efficiency.Verdant Power Canada ULC 27