Title: The power coefficient of windmills in ideal conditions

Authors: Shikha Singh, T.S. Bhatti, D.P. Kothari

Addresses: Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India. ' Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India. ' Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India

Abstract: The windmill efficiency, also designated as the power coefficient, is defined as the ratio of the actual power output to the power present in the free stream of a fluid flowing through the same cross-sectional area. There are remarks in the literature to the effect that the power coefficient of actual windmills is very close to the ideal power coefficient or Betz limit of 0.5926. In this paper, the traditional basic assumptions in establishing the Betz limit are reviewed with mathematical derivation of the ideal power coefficient. It is concluded that the value of the ideal power coefficient is 0.89.

Keywords: limits; power coefficient; wind turbines; windmill efficiency; wind energy; wind power; renewable energy; Betz limit.

DOI: 10.1504/IJGEI.2004.005768

International Journal of Global Energy Issues, 2004 Vol.21 No.3, pp.236 - 242

Published online: 01 Dec 2004 *

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