An experimental investigation into the influence of unsteady wind on the performance of a vertical axis wind turbine

► Experiments on a wind tunnel scale VAWT were conducted in unsteady wind conditions. ► Varying tip speed ratios and amplitudes were tested and the results presented. ► The unsteady power coefficient of the VAWT does not trace the steady CP curves. ► Small amplitudes have no effect on cycle CP while large amplitudes are detrimental. ► Mean λ below peak performance show hysteresis in CP curve while high λ do not.