Energy Convers. Mgmt Vol. 32, No. I, pp. 43-50, 1991 0196-8904/91 $3.00 + 0.00 Printed in Great Britain. All rights reserved Copyright © 1991 Pergamon Press plc PERFORMANCE PREDICTION OF MULTIVANE WINDMILLS IN INDIA CHANDRA SHEKHAR SINHAt and TARA CHANDRA KANDPAL Solar Concentrator Laboratory, Centre of Energy Studies, Indian Institute of Technology, Hauz Khas, New Delhi-II0 016, India (Received 9 March 1989; received.for publication 15 June 1990) Abstract--A method for predicting the useful output from the Apoly 12-PU-500 water pumping windmill (the most extensively used windmill in India) is proposed. The prediction procedure establishes the overall efficiency of the Apoly as a function of wind speed, using performance data of the windmill. Using mathematical properties of the Weibull distribution, an expression for the useful output from the windmill is established. The Weibull parameters of two locations in India, of different agro-climatic characteristics, are used to predict the monthly hydraulic output from the Apoly. The prediction procedure may prove useful for the rational siting of the 50,000 windmills for water pumping planned in India by 2001 A.D. Windmill irrigation Performance prediction Windmill designs in India 1. INTRODUCTION Water pumping for irrigation is a priority area in India. Policy emphasis in this direction has resulted in the number of electric pumpsets alone jumping from 21,000 in 1951 to over 7 million today. By 1990, this figure was expected to touch 8.82 million [1]. In view of the increasing shortage and cost of electricity and other conventional fuels, the Government of India is promoting the utilization of renewable energy technologies for wide- ranging end uses, and the high priority for irrigation water pumping is reflected in the government's promotion of alternative technologies for this purpose. Since its inception in 1982, the Department of Non-conventional Energy Sources (DNES) has installed over 1900 water pumping windmills all over India [2]. The DNES plans to achieve a target of 50,000 windmills for water pumping alone by 2001 A.D, [3]. However, the diffusion of windmill technology has been far from satisfactory, and one of the main reasons for this has been poor site selection, leading to an unsatisfactory performance of the windmills. One study[4] surveyed 177 windmills (which is about 30% of the total windmills installed at that time) in eight states of India and found that 106 of the windmills were sited in areas with inadequate wind or water. Successful implementation of the proposed plans of the DNES, thus, requires the development of a quick and reasonably accurate method for indentifying areas where the existing windmill designs in India are likely to be viable. This paper is a preliminary step in this direction. The method proposed for predicting the monthly output from the Apoly 12-PU-500 (the most widely used windmill in India, details of which are presented in Section 3) windmill design is outlined in Section 2. An empirical relationship of the variation of the efficiency of the windmill with wind speed is established and used with the Weibull parameters to predict the monthly overall efficiency and the hydraulic output in Section 3. Though the computations are made for the Apoly windmill, the arguments are valid for any other windmill, and the method can be used to predict the output from any other windmill with known performance characteristics. The monthly prediction of the output from the Apoly windmill for two locations, namely Indore and Madras, is discussed in Section 4. tPresent address: Tata Energy Research Institute, 7 Jor Bagh, New Delhi-110 003, India, 43