A comparative calculation of the wind turbines capacities on the basis of the L-sigma criterion

Usually, wind sites are equipped with hat-running Horizontal Axis Wind Turb ines of the airscrew type, which has a high efficiency. In this article, th e argument is put forward that the choice of a wind turbine must not be bas ed only on high efficiency. We propose a comparative criterion adapted to t he comparison of a horizontal axis wind turbine with a vertical axis wind t urbine: the Go criterion. This criterion consists in comparing wind turbine s which intercept the same front width of wind, by allocating them a same r eference value of the maximal mechanical stress on the blades or the paddle s. On the basis of this criterion, a quantitative comparison points to a cl ear advantage of the Savonius rotors, because of their lower angular veloci ty, and provides some elements for the improvement of their rotor. (C) 2000 Elsevier Science Ltd. All rights reserved.