An introduction of Kyuden Group's geothermal power plants in Kyushu Island, Japan

Abstract

Kyushu island, located in the southern part of Japan, is one of Japan’s most famous geothermal resource areas.
Kyushu Electric Power Company, a major power company in Japan, supplies over 16 GW of electricity to Kyushu island. Together with its subsidiaries, the company forms the Kyuden Group, which owns geothermal power plants with a combined capacity of 224 MW across eight sites in Japan. In addition to domestic operations, the group is also actively investing in overseas geothermal power plants.
The development of Japan’s first commercial geothermal power plant began with a resource survey at the Otake site in 1949. Initial findings revealed that the geothermal fluid was hot water dominated, which at the time was considered unsuitable for power generation, leading to the suspension of the project. Meanwhile, New Zealand succeeded to operate a single flash geothermal power plant with the separation of steam and hot water. Kyushu Electric Power was encouraged by this fact and resumed the development of the geothermal power plant in Otake area and completed it in 1967. This power plant is still in operation as of today, following a major upgrade in 2020, that increased the capacity from 12.5 MW to 14.5 MW. The success of the Otake power plant led to further development of flash geothermal power plants such as Hatchobaru (55 MW x 2 units), Yamagawa (30 MW), Ogiri (30 MW), Takigami (27.5 MW) and binary power plants (totaling approximately 12 MW).
This paper presents a historical overview and the latest developments of geothermal power generation by the Kyuden Group, with a particular focus on Otake and Yamagawa Power Plant, which includes both flash and binary systems.