Japan’s Omarugawa pumped-storage scheme with an asphalt-lined reservoir

The Kyushu Electric Power Co has developed a number of pumped-storage plants over the years to provide power for daytime peak demand periods as well as for emergency backup. The 500 MW Ohira and 600 MW Tenzan schemes began operation back in 1975 and 1987, respectively, contributing to the stability of power supply at that time. From the late 1980s through to the early 1990s, power demand began to surge along with the economic boom, and peak demand rose sharply. It was therefore decided to construct new pumped storage schemes, one of which was the Omarugawa plant, where the last of four units was commissioned in 2011.