In 1975, modeled after an Austrian wind turbine, The National Aeronautics and Space Administration (NASA) built a two-bladed wind turbine with flexible or teetered rotor hubs, finding that two blades can produce approximately the same amount of energy as three but at a savings due to not having the cost and weight of a third blade. The rotational speed is increased for two-blade rotors which reduced damaging stress and reduces the gear ration in the gear box. None of the NASA wind turbines experienced failures in the gearbox. None of the NASA prototypes became commonly produced as commercial generators because the purpose of the program was to develop the technology and support the emerging industry.
Although a number of wind turbines were developed and tested, there was a significant decrease in competing energy prices during the 1980s. Concerns over global warming, and the future fossil fuel depletion forced interest in renewable energy, once again, as the 21st century began.<< previous 1 2 3 4 5 6 next >>