FARM-SIZED LOW WINDSPEED TURBINE

Well over 50 % of US land area constitutes low wind-speed sites, yet wind turbines are either not effective or only marginally effective in such low winds. To extract significantly more energy from such DOE Class 1 or Class 2 winds requires substantially increasing turbine blade rotor diameter (wind power is proportional to the square of the blade diameter). However, due to limitations on turbine blade tip speed, this cannot be done without significantly decreasing blade rotor rpm (blade tip speed is directly proportional to rotor rpm), which in turn, due to limitations on generator output at low rpm, would normally require considerably more massive and costly wind turbines. What is being proposed is a novel low rpm, low mass, and low cost 12 kW permanent magnet wind turbine generator that will be built, bench tested, and then field tested within a commercially available 10 kW horizontal axis wind turbine. Numerical simulations show that, with the greatly extended area rotor facilitated by the low rpm generator, we get: 1. Effective turbine operation in Class 1 and Class 2 low wind speed sites where other wind turbines are impractical, 2. Substantially shorter payback periods (due to lower price and greater power in low winds), 3. Quieter turbines as result of the lower rpm (turbine noise is proportional to the fifth power of the blade tip speed).