Energy in Agriculture, 6 (1988 ) 311-324 311 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands Cost Estimate of Chance-constrained Windmill Irrigation System R.K. PANDA I, T.K. SARKAR2 and A.K. BHATTACHARYA 2 lOrissa Renewable Energy Development Agency, 622-Sahidnagar, Bhubaneswar- 751 007, Orissa (India) 2Water Technology Centre, Indian Agricultural Research Institute, New Delhi-110 012 (India) ( Accepted 18 June 1987) ABSTRACT Panda, R.K., Sarkar, T.K. and Bhattacharya, A.K., 1988. Cost estimate of chance-constrained windmill irrigation system. EnergyAgric., 6: 311-324. A methodology has been developed in this study to determine the investment per unit amount of water supplied and the levels of daily irrigation demand satisfied by the most economic windmill irrigation system at various levels of risk (probability of failure). Hourly wind-speed data over a period of 5 years at Delhi, India, were analysed to compute the diurnal windpump discharge at varying levels of risk. The sizes of reservoirs required to modulate fluctuating discharge, and to satisfy predetermined levels of irrigation demand, were computed by cumulative deficit water budgeting. The capital cost and annual cost of the reservoirs and the complete irrigation system were calculated subsequently. The cost per m 3 of irrigation water supplied by the most economic windmill irrigation system was found to vary between 38 paise and 71 paise at Delhi, India, de- pending on the level of risk considered (US$= 10.21 Indian Rupees as in October 1983, and 1 Rupee = 100 paise). The daily irrigation demand satisfied by the most economic windmill irriga- tion system was noted to be a little less than or equal to 25 m 3 based on the level of risk. INTRODUCTION Lift irrigation activity is a major consumer of energy among agricultural operations. It is becoming increasingly difficult to meet the energy require- ment for lift irrigation due to the scarcity and high price of conventional and exhaustible resources. The use of alternate sources, therefore, is of great im- portance and interest these days. Wind energy is one of the alternative sources which can be harnessed through the windmill for irrigation pumping. It is a decentralized source of supply readily available at the doorstep of the individ- ual user, along with its operating control. A windmill irrigation system comprises of the windmill pump, the storage reservoir and the conveyance channels. Of these three, the size of the storage 0167-5826/88/$03.50 © 1988 Elsevier Science Publishers B.V.