Designing small wind turbines for highly turbulent sites

The use of small grid-connected wind turbines in the built environment is increasing. The international wind turbine design standard is based on open terrain sites, but in the built environment, the turbulence intensity is much higher than in open terrain and can lead to premature fatigue of turbines This paper compares the turbulence power spectral densities from direct measurement on the rooftop of Bunning Group Ltd’s warehouse at Port Kennedy, Western Australia, with predictions from the von Karman and Kaimal spectra used by turbulence models in the design standard. Both model spectra under estimate the magnitude of the measured values for all wind components although the Kaimal spectra provides more realistic values in terms of predicting the turbulence power spectra of lateral and vertical wind components in the built-environment. A corrected Kaimal model is proposed that has good agreement with measured values and can be viewed as a first step towards upgrading the existing standard with a dedicated design model for the built environment.