Wind Regimes in Urban Environments: Experimental Comparison with the IEC 61400.2-2013 Open Terrain Wind Model

Small wind turbines are usually sited in more complex environments than the open terrain sites, such as urban built environment. However, the international small wind turbine design standard IEC61400.2 is based on the measurements of flat and open terrain. Failures of SWTs operational in urban area predicts the inadequacy of turbine design for the turbulent wind resource at the sites. This study investigates the wind speed in the vertical direction at a complex terrain site, where a small 5 kW Aerogenesis horizontal-axis wind turbine is in operation and subject to an ongoing research. Wind measurements were acquired at 20 Hz using 3 three-axis ultrasonic anemometers equispaced around the tower of the wind turbine. The results show significantly high wind speeds (8–12 ms⁻¹) in the vertical direction. High fluctuation of vertical wind speed was observed with standard deviation >2 ms⁻¹. In addition, the turbulence in vertical direction was found to be 20% higher than the IEC 61400.2 level. The result of this study is important for the small wind turbine developers as they seek best practice for determining turbine operating loads.