Potential of power generation by solar batteries for operating irrigation pumps in Ishigaki Island

Electricity generated by solar batteries has many merits. Especially in a small island where there are not enough water resources, adequate and cheap electricity is prerequisite for agriculture. First, trials to estimate electricity generation by solar battery were conducted using the limited data on solar radiation energy. Second, operation times were estimated for various pumps placed in the pumping station in Ishigaki Island. It was clarified that there was a tendency that operation times calculated by estimated curves showed somewhat longer hours that of observed curves, for the smaller pumps. On the other hand, for the larger pumps, there was a tendency that operation times derived from observed curves exceeded the times derived from estimated curves. Third, a simulation was conducted for finding the suitable irrigation area supported by a self electricity generating system. It was concluded that a 15 kW pump was suitable as this was operated longer hours than other pumps and irrigated area slightly increased if rotation of irrigation was applied for the 200kWp system. But for the 1000kWp system, irrigated area increased effectively.