Performance of wind energy conversion systems under low power density wind regimes

Abstract

Due to the present day's energy crisis and growing environmental concerns, supplementing our energy base with clean and renewable resources like wind has become imperative. With its steady growth rate over the years, wind energy would become a major player in the clean energy scenarios in the near future. On the other hand, sites with high wind energy potential are becoming scarce due to social, technical and economic reasons and the future wind power developments would more be focused on sites with moderate wind spectra. Keeping this in view, several leading wind turbine manufactures have introduced turbine designs targeting sites with low to medium wind potential. The current investigation theoretically analyzes and simulates the performance of some of these new designs under low power density wind regimes. Three low wind speed turbines recently introduced by leading wind turbine manufacturers were considered under this study. Performances of these turbines at a representative site falling under the wind class 3 were modeled. The model basically combines the Weibull probability density function of the wind velocity at the site and the velocity - power response of the turbine which is then integrated within the productive functional limits of the turbine. Expressions for the energy yield and capacity factor of the turbine at a given site are presented. Wind Energy Resource Analysis (WERA) tool, which is based on the above models, is then used to simulate the performance of the selected turbines at the representative site. Performance of a conventional turbine at the given site has also been analyzed for comparison. Results of the simulation indicates that, with reasonably high capacity factors, all the three low wind speed turbines perform well under the low power density wind conditions. The key requirements for the turbines to perform better under low wind regions have been identified as lowering the cut-in and rated wind speeds, and design improvements for better velocity power response at lower wind spectra.