APPLICATION OF SOLAR ENERGY IN IRRIGATION SECTOR

Abstract

Many parts of the world do not have electricity but have abundant solar energy. In absence of electricity farmers are forced to use diesel pumpsets to lift ground water for irrigating their crop lands. Then automatically the process of producing food becomes dependent on energy which is conventionally produced by dissipating fossil fuel. Solar energy application can have vital role for sustainable agriculture keeping in view the upcoming energy crisis and environmental concern. Solar Photovoltaic (SP V) pumps can be used in lifting water from streams or pumping the water from aquifers for irrigation instead of conventional irrigation pumps. Secondly, scarcity of water is widespread problem in the world. • Therefore it is very important to improve water use efficiency in irrigation sector. An ideal solution to deal with these two crises would be SPV drip and mini sprinkler irrigation systems. The overall objective of this dissertation is to study viability .of solar photovoltaic energy in the irrigation sector, especially for drip irrigation and mini sprinkler irrigation considering life cycle cost in long running. The development of Angstrom equation to estimate solar radiation in Roorkee is also one specific objective. Roorkee is located on the banks of the Upper Ganges canal in Haridwar District, State of Uttarakhand in India. Due to economic consideration in developing countries, the instrumentation for measuring solar radiation is usually available at a few places while bright sunshine hours are measured at several locations. It is possible to develop correlations to predict global solar radiation from readily measured sunshine data. In this study the Angstrom equation and Hargreaves Samani model have been employed to estimate solar radiation. Angstrom equations were formed for each month of a year to predict monthly average daily solar radiation at Roorkee. 15 years (1990 to 2004) data on sunshine hours and monthly average daily global solar radiation has been used The solar radiation estimated using equations and measured solar radiation were compared using the mean bias error (MBE), root mean square error (RMSE) and mean percentage error (MPE) statistic techniques. This study shows that better results are obtained in estimation of solar radiation by using separate Angstrom equations for each month instead of using single Angstrom equation (based on entire data). Using separate Angstrom equations for each month, the value of MBE, RMSE, and MPE between predicted and measured solar radiation in Roorkee decrease by 92%, 23% 86% respectively with respect to using single Angstrom equation. In other words predicted results are more accurate using separate equation for each month. The generated single and separate Angstrom equations at Roorkee have been used to predict solar radiation at other two places named Dehradun and Pantnagar. The comparison presents a remarkable agreement between the measured and calculated value of solar radiation for these two stations with single and separate Angstrom equations. iii Hargreaves and Samani model based on maximum temperature and minimum temperature shows underestimation of solar radiation at the three locations considered in this study. Measured and calculated monthly average daily global solar radiations are tested for various seasons (winter, pre-monsoon, monsoon, post-monsoon) of the year. It shows that in the monsoon season Angstrom equation gives less accurate predicted values compared to other seasons of the year. This study presents a procedure to design a drip irrigation system for citrus crop and design of a mini sprinkler irrigation for cotton crop and associated sizing of solar photovoltaic system to energize pumping system for both drip irrigation system and sprinkler irrigation system. SP V drip irrigation system and SPY mini sprinkler irrigation system have been designed considering different land sizes and different pumping depth to ground water. There are 100 combination of land size• (0.5ha to IOha) and depth (lOm to 50m) of aquifer pumping for drip irrigation and 80 combinations of land size (0.25ha to 4. Oha) and depth (10m to 50m) of aquifer pumping for mini sprinkler irrigation system. The economic analysis has been carried out for each combination to study variation of investment cost and levelized cost of water. Concerning the investment cost of SPV pumpsets up to Rs. 10 lakhs, this study shows that SPV pumping system for drip irrigation system is economically favoured for 6.5ha land size for citrus crops and 30 m maximum depth to ground water. For the mini sprinkler irrigation for cotton crops, economically favourable land size would be up to 1.5 ha for 10 m water depth. In this study the economic viability of the solar photovoltaic pumpset compared with the conventional diesel pumpset has been analyzed for 4 ha citrus crop land through sensitivity analysis using a life cycle cost (LCC) computation. The sensitivity analysis has been carried out to compare both pumpsets based on parameters such as module cost per Wp, diesel fuel cost, life time of diesel pumpset, diesel price escalation rate, discount rate. The study shows that if operating life is more than 9 years then solar pumpset is more economical against conventional diesel pumpset. The LCC of diesel pumpset is sensitive to discount rate, price escalation rate and diesel fuel cost as variation in those parameters lead to higher percentage variation in LCC of the diesel system. LCC is less sensitive to life time of the diesel pump. In SPVpumping system, LCC is highly sensitive to module price per Wp.