A stand-alone photovoltaic power system for remote villages using pumped water energy storage

Abstract

The present paper regards the implementation of a stand-alone photovoltaic plant in which battery storage is partially replaced by a micro-hydraulic system. The plant was installed on Donoussa Island in the Aegean Sea, Greece to cover basic electricity needs of the remote village of Merssini (13 houses). Lighting, TV set and refrigerator were considered basic electricity needs for each house. The photovoltaic array consists of 300 photovoltaic modules of 60 W p each, for a combined 18 kW p total installed power. The micro-hydraulic system consists of a water pump of 6 kV A and a water turbine coupled with a DC generator of 7.5 kW and two identical water reservoirs of 150 m 3 capacity each. During the day, the load is satisfied directly form the photovoltaic generator through an inverter (UPS unit of 25 kV A, 380 V-3 phases alternative current), while any energy surplus is directed to the pump for pumping water from the low level reservoir (at about 100 m altitude from sea level), to the high level reservoir (at about 200 m altitude from sea level). During the night, water is turbined to the low level reservoir providing energy to the load. There is also a battery bank of 186 cells of 2 V nominal voltage in series, with a total capacity of 100 A h. The batteries cover primarily load peaks. The paper presents first results and experience gained from the system performance.