photovoltaic panels, courtesy of DOE/NREL


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Wind power systems
Wind turbine

Wind energy is one of the fastest-growing forms of electricity generation in the world. The United States can currently generate more than 10,000 megawatts (MW) of electricity from the wind, which is enough to power 2.5 million average American homes. With further development, wind energy could ultimately provide as much as 20% of this nation's energy needs. This part of the course addresses the following topics:

  • Wind resources: World, U.S. and Colorado
  • Power in the wind, efficiency of wind energy harvesting
  • Wind turbine generators and interface to the power grid
  • Control of wind turbines
  • Wind farms
2.5MW dynamometer test bed, courtesy of NREL/DOE 2.5 MW wind turbine drive train dynamometer test bed facility at NREL's National Wind Technology Center (NWTC).
Inside a wind turbine, courtesy of NREL/DOE

Wind turbine size

2 MW wind turbine compared to a 747 Jet

A typical wind horizontal-axis wind turbine has two or three blades, spanning a diameter of about 70m for a 2 MW turbine. A controller starts up the machine at wind speeds of about 3 to 6 m/s (8 to 16 mph) and shuts off the machine at about 25 m/s (55 mph). Gears connect the low-speed shaft to the high-speed shaft and increase the rotational speeds from about 30 to 60 rotations per minute (rpm) to about 1000 to 1800 rpm, the rotational speed required by most generators to produce electricity. Alternative designs are based on direct-drive generators, sometimes in combination with power electronics converters, which enable more efficient wind energy harvesting and improved system control over a wider range of wind speeds.