Stand-Alone Solar Organic Rankine Cycle Water Pumping System and Its Economic Viability in Nepal

The current study presents the concept of a stand-alone solar organic Rankine cycle (ORC) water pumping system for rural Nepalese areas. Experimental results for this technology are presented based on a prototype. The economic viability of the system was assessed based on solar radiation data of different Nepalese geographic locations. The mechanical power produced by the solar ORC is coupled with a water pumping system for various applications, such as drinking and irrigation. The thermal efficiency of the system was found to be 8% with an operating temperature of 120 degrees C. The hot water produced by the unit has a temperature of 40 degrees C. Economic assessment was done for 1-kW and 5-kW solar ORC water pumping systems. These systems use different types of solar collectors: a parabolic trough collector (PTC) and an evacuated tube collector (ETC). The economic analysis showed that the costs of water are $2.47/m(3) (highest) and $1.86/m(3) (lowest) for the 1-kW system and a 150-m pumping head. In addition, the cost of water is reduced when the size of the system is increased and the pumping head is reduced. The minimum volumes of water pumped are 2190 m(3) and 11,100 m(3) yearly for 1 kW and 5 kW, respectively. The payback period is eight years with a profitability index of 1.6. The system is highly feasible and promising in the context of Nepal.