Development of an efficient off-grid pumping system and evaporation reduction strategies to increase access to irrigation for smallholder farmers in India

Abstract

Due to the unavailability of electricity, about 85% of groundwater irrigation in eastern India employs fuel-powered surface pumps, which can have system efficiencies as low as 5%. As fuel prices continue to rise, impoverished smallholder farmers cannot afford the operation costs of their systems and, as a result, irrigate less land. This research aimed to develop a more efficient off-grid system that eliminates suction head while continuing to utilize a fuel engine on the surface. Design requirements included increased discharge, increased efficiency, portability, maintainability, availability of replacement parts, and affordability. Flow rates and efficiencies of Indian pumps at varying pressure heads were tested to establish baseline performance and test the hypothesis that removing suction lift reduces operation costs. It was found that eliminating suction head can decrease operation costs up to 44% for the farmers. Fuel-driven system options investigated include flexible shafts and telescoping shafts to transmit power from a surface engine to a submersible pump, fluid machinery such as semi-open hydraulic systems, jet pumps, compressed air motors, and air lifts, and off-grid electricity generation employing a household backup generator or automotive alternator. However, none of these alternatives met all the design requirements. Instead, a hybrid motorized-manual rope pump was prototyped and tested on a well in Ruitola, Jharkhand. Although this system does not meet all the design requirements, it has the added benefit of providing domestic water supply. The prototype discharged an average of 155.4 L/min in motorized mode and 17.2 L/min for men and 13.3 L/min for women in manual mode. The rope pump received positive feedback from the users and thus could be taken forward with several modifications to improve performance. To increase the available water resources, evaporation reduction strategies to limit water loss from farm tanks were explored. The strategies employed waste materials and included covering a water surface with waste PET bottles and floats comprised of PET waste bottles and old saris. While waste bottles proved promising in a preliminary test, data in a larger experiment has thus far proved inconclusive and further testing is needed.