Modelling the structural loading of a small wind turbine at a highly turbulent site via modifications to the Kaimal turbulence spectra

Although, wind turbines have traditionally been sited in open terrain, there is a growing trend of installing turbines in non-homogeneous terrain, such as urban areas. Recorded urban turbine failures suggest that turbine design has been inadequate for the turbulence experienced at these sites and hence a better understanding of the turbine-loading issues in the built environment is required. This paper compares turbine blade load statistics for inflow turbulence fields based on the open terrain standard Kaimal spectra, as suggested in the standard IEC61400-2 that covers the design and safety standard of small wind turbines, and measured turbulence spectra from a built environment site. The findings show that for extreme, high turbulent intensity winds, the measured spectra predict isolated loading events around twice the magnitude of loads predicted by use of the standard spectra. The work suggests the need for improvements to the standard in order to model the non-Gaussian wind statistics that occur in extreme events such as sudden strong gusts.