Press Release

Mitsubishi Power Completes Renovation of Generating Facilities at Otake Geothermal Power Station
-- Efficient Utilization of Geothermal Resources to Curb CO2 Emissions, and Contribute to Decarbonized Economy --


・ First “double flash and dual pressure” method in Japan, efficiently utilizing a mix of high and low pressure steam
・ Power output increased to 14.5MW, 2MW higher than before renovation, with commercial operation starting in October

YOKOHAMA, JAPAN (October 5, 2020) – Mitsubishi Power, a major subsidiary of Mitsubishi Heavy Industries (MHI) Group, has completed its renovation of the Otake Geothermal Power Station (Kokonoe-machi, Oita Prefecture) operated by Kyushu Electric Power Company. Commercial operation of the renovated facility began in October 2020. The stable electric power supply generated by the highly efficient and reliable steam turbine installed as part of this renovation project will curb CO2 emissions, and contribute to a decarbonized economy.

This renovation project was conducted under an engineering, procurement and construction (EPC) contract by a joint venture comprising Mitsubishi Power, which supplied the steam turbine, Mitsubishi Power Industries Co., Ltd., which handled the supply and installation of auxiliary equipment, and Mitsubishi Electric Corporation, which supplied the generator and electrical facilities.

The power generation system utilizes a “double flash and dual pressure” method, the first of its type in Japan. This allows for stable operation of the steam well and efficient use of geothermal resources, and has increased the power output by two megawatts (MW) compared to the previous facility, to 14.5MW. Construction was completed two months ahead of schedule from the plan when work began in May 2019, allowing for the start of commercial operation in October.

In the double flash and dual pressure method, high pressure primary steam from a powerful production well, and low pressure secondary steam from a weak production well, are supplied to the steam turbine. Steam is further obtained by lowering the pressure of the hot water extracted from the primary steam, which is then used as secondary steam.

Geothermal energy utilizes the heat energy of the magma chamber inside the earth, and because no combustion takes place above ground, little CO2 is emitted into the atmosphere, making it an effective method of power generation for curbing global warming. Further, because geothermal power is a type of renewable energy that makes use of the enormous heat energy in the earth’s interior, it is not subject to the cycles of season, weather, or time of day, offering a high availability factor nearly on a par with that of thermal power.

Kyushu Electric Power’s Otake Power Station began commercial operation in August 1967 as Japan’s first commercial geothermal power station. This plant is also Japan’s first wet steam geothermal plant, and Mitsubishi Power’s first commercial geothermal facility. Over more than fifty years in operation, this plant has contributed to a stable energy supply, and the decarbonization (sustainability) of society.

Mitsubishi Power has fulfilled orders for more than 100 projects in the geothermal power field in 13 countries. With total plant capacity of more than 3,200MW, Mitsubishi Power holds a leading share of the world’s geothermal power generating capacity, and as a geothermal EPC provider, contributes to their stable operation.

Mitsubishi Power, through innovative power generation technologies and solutions, will contribute to the realization of a sustainable decarbonized economy, and work to solve the wide range of issues facing global society.

Mitsubishi Power’s Geothermal Power Plants

Otake Geothermal Power Station
Otake Geothermal Power Station