Optimum operation of desalination plant to minimize power consumption and water shortage risks in Okinawa, Japan

摘要

Okinawa Island is located in the southern region of Japan and has a population of 1.22 million. Okinawa Prefectural Enterprise Bureau (OPEB) supplies 410,000 m~3/d of water to 24 municipalities. Although OPEB uses multiple water resources including dam reservoirs and ground-water, increased water demand resulted in occasional water shortages until a seawater desalination plant (40,000 m~3/d) started operations in 1997. In this study, a model was developed to simulate the water supply system of Okinawa Island using precipitation and OPEB operational data from 2009 to evaluate the role of the desalination plant in reducing risks associated with drought and power consumption of the plant. The simulation results indicate that without the desalination plant, the dam reservoir storage falls below 50% for 70 days, whereas with the desalination plant, storage remains above 50%. If the plant was operated at full capacity, the dam reservoir storage increased by 17.2% after 1 year of simulation time. However, the desalination plant consumes 4.5-14.7 times more electricity per unit volume of water than other water resources. Although the desalination plant plays an important role in avoiding water shortage in Okinawa Island, operational protocols to minimize power consumption need to be developed further using simulation models such as the one developed in this study.