Author
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Neal, Byron |
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Submitted to: Windpower
Publication Type: Proceedings Publication Acceptance Date: 5/21/2010 Publication Date: N/A Citation: N/A Interpretive Summary: The effects of the strength of turbulence on the capture of energy by small wind turbines has been a point of debate in the last few years. Over the years, many attempts have been made to model the effects of turbulence on the operation of the turbines. Most of these models have been calibrated to a single turbine at a specific site. Power and performance data for three small wind turbines were analyzed to determine the effect that turbulence intensity has on the power curve and energy capture. Three different turbine configurations were used in this study. The turbine configurations were (1) constant speed, downwind, free yaw; (2) variable speed, upwind, free yaw, furling; and (3) variable speed, downwind, free yaw. Downwind turbines have the rotor blades rotating behind the tower when viewed from upwind. Upwind turbines have the rotor blades rotating in front of the tower when viewed from upwind. Free yaw turbines use the drag from the wind or a tail to keep the turbine pointed into the wind. Furling is the process where a turbine turns its rotor out of the wind to control its rotational speed. Contrary to previous studies, the measured power curve of the variable speed, free yaw turbines showed a slight increase during periods of high turbulence intensity for wind speeds below the rated wind speed. However, the power curves showed a decrease in power at high turbulence intensity for wind speeds greater than the rated wind speed. The constant speed turbine showed the greatest reduction in power production with an increase in turbulence intensity. Technical Abstract: The effect of turbulence intensity on energy capture by small wind turbines has been a point of debate in the last few years. Claims of 25% de-rating of the power curve for turbines installed at sites with high turbulence are not uncommon. Over the years, many attempts have been made to model the effects of turbulence on the operation of the turbines. Most of these models have been calibrated to a single turbine at a specific site. Power and performance data for three small wind turbines were analyzed to determine the effect that turbulence intensity has on the power curve and energy capture. Three different turbine configurations were used in this study: (1) constant speed, downwind, free yaw; (2) variable speed, upwind, free yaw, furling; and (3) variable speed, downwind, free yaw. Contrary to previous studies, for the variable speed, free yaw turbines, the measured power curve showed a slight increase in power during periods of high turbulence intensity for wind speeds below the rated wind speed. However, the power curves showed a decrease in power at high turbulence intensity for wind speeds greater than the rated wind speed. The constant speed turbine showed the greatest reduction in power as the turbulence intensity increased. |
