Effects of Variable Speed and Drive Train Component Efficiencies on Wind Turbine Energy Capture

Research output: Contribution to conferencePaper


A wind turbine rotor achieves optimal aerodynamic efficiency at a single tip-speed ration (TSR). To maintain that optimal TSR and maximize energy capture in the stochastic wind environment, it is necessary to employ variable-speed operation. Conventional constant-speed wind turbines have, in the past, been converted into variable-speed turbines by attaching power electronics to the conventionalinduction generator and gearbox drive train. Such turbines have shown marginal, if any, improvement in energy capture over their constant-speed counterparts. These discrepancies have been shown to be th result of drive train componenets that are not optimized for variable-speed operation. Traditional drive trains and power electronic converters are designed to achieve maximum efficiency at fullload and speed. However, the main energy producing winds operate the turbine at light load for long periods of time. Because of this, significant losses to efficiency occur. This investigation employs a quasi-static model to demonstrate the dramatic effect that component efficiency curves can have on overall annual energy capture.
Original languageAmerican English
Number of pages9
StatePublished - 1998
EventASME/AIAA Wind Energy Symposium - Reno, Nevada
Duration: 6 Jan 19979 Jan 1997


ConferenceASME/AIAA Wind Energy Symposium
CityReno, Nevada

NREL Publication Number

  • NREL/CP-500-22082


  • drive train component
  • tip-speed ratio
  • turbines
  • variable speed
  • wind


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