The Appi area of Hachimantai City is in an extremely snowy region of northern Iwate Prefecture. A nearby ski resort is approximately 1,130 meters above sea level, and the snowfall there reaches 4 to 5 meters.
The Appi geothermal power plant is built on the slope of a mountain. It has been in operation since March 2024.

Mitsubishi Materials Corporation and Mitsubishi Gas Chemical Company, Inc. jointly established Appi Geothermal Energy Corporation in 2015 and built the power plant to reduce CO₂ emissions and ensure stable power supply. Yuko Kanno became President of Appi Geothermal Energy in April 2022 after working for Mitsubishi Materials in nuclear power-related businesses. Kaname Ohata, who has been involved in the project since 2018, works in the Production Engineering Office, Technology Management Department, Renewable Energy Business Division of the Strategic Headquarters. They told us about their passion for the power plant and geothermal power generation.

Geothermal power generation involves drilling down deeply in geothermal areas where volcanoes, natural fumaroles, hot springs, and altered rocks exist and extracting steam from geothermal reservoirs to rotate turbines to generate electricity. Because its energy source exists depths below the earth's surface, there is no fear of depletion as with fossil fuels, and almost no CO₂ is emitted. The plant is expected to provide a stable power supply day and night for an extended period of time.

Kanno explains the background that led to the construction of the Appi Geothermal Power Plant:

"From 2000 to 2003, the New Energy and Industrial Technology Development Organization (NEDO) conducted a geothermal development promotion survey, which confirmed the promising geothermal resources in the Hachimantai area. Mitsubishi Materials Corporation and Mitsubishi Gas Chemical Company, Inc. conducted additional studies to determine a geothermal power project's feasibility, including profitability. In 2015, the two companies established a joint venture, Appi Geothermal Energy Corporation, and conducted an environmental impact assessment. In January 2018, the government issued a notification of confirmation. Subsequently, with Electric Power Development Co., Ltd. (J-POWER), we commercialized the project. Construction work began in 2019, and we were able to start the plant’s operation in March 2024."

From the initial survey, it took 20 years. There were countless hardships, including snow, which was a particular headache for on-site personnel. As mentioned earlier, the Appi Geothermal Power Plant is in an exceptionally snowy area; the snow could accumulate to the point where roads were impassable only an hour after the snowplows passed. Some roads are closed for the winter. From the time construction started to the period of trial run, the struggle against snow was ceaseless.

"The power plant is 14 km beyond where the winter road closure starts," Ohata told us. "In 2022, we brought in a large snowplow and installed snow fences to prevent whiteouts. In addition, we have increased the number of snow removal crews this winter in preparation for the start of plant operation. We secured access to the power plant by clearing the snow ourselves day and night to conduct trial run and inspections in two shifts, 24 hours a day."

After about four and a half years of construction work, the plant was put into operation.

“With an output of 14,900 kW, the plant's installed capacity is about two orders of magnitude smaller than that of large power plants using thermal or nuclear energy, but we are determined to contribute to the reduction of CO₂ emissions and the stable supply of electricity while placing the highest priority on safety,” says Kanno.

The initial cost of geothermal power generation is high: It requires drilling to a depth of about 2,000 meters underground and extracting the steam accumulated in the geothermal reservoir, a process that costs several hundred million yen. Even if a geothermal reservoir is there, steam will only come out if there are many fractures. "It is really challenging to locate such fractures because they are only a few millimeters to a few centimeters in width," Ohata says. In a wind power project, you get some idea of how much wind blows in a given year when you do a survey, and in a solar power project, how much sunshine the area gets. However, in a geothermal power project, you will not know until you drill. This uncertainty increases the risks significantly.

Nevertheless, Mitsubishi Materials continues to take on the challenge of developing geothermal power generation to ensure a stable supply of renewable energy. Utilizing its abundant experience and advanced technological capabilities cultivated over many years through the development of coal and metal mines, the company began operating the Onuma Geothermal Power Plant (Kazuno City, Akita Prefecture) in 1974. Since then, the company has been involved in the construction and operation of the Sumikawa Geothermal Power Plant^*1 (Kazuno　City, Akita Prefecture; started operation in 1995) and the Wasabizawa Geothermal Power Plant^*2 (Yuzawa City, Akita Prefecture; started operation in 2019), leading the geothermal power business.
^*1 : Tohoku Electric Power Co., Inc. for power generation, Mitsubishi Materials Corporation and Mitsubishi Gas Chemical Company, Inc. for steam supply.
^*2 : Yuzawa Geothermal Power Generation Corporation was established by J-POWER, Mitsubishi Materials Corporation, and Mitsubishi Gas Chemical Company, Inc. to manage and operate the plant.

In 2021, a geothermal resource survey began in the Komonomori area (Kazuno City, Akita Prefecture), located west of the Appi Geothermal Power Plant. In 2022, another survey began in the upper reaches of the Appi River (Hachimantai City, Iwate Prefecture) east of the Appi Geothermal Power Plant, both using a grant from the Japan Organization for Metals and Energy Security (JOGMEC, former Japan Oil, Gas and Metals National Corporation). Furthermore, in 2022, we invested in "Hakodate Esan Geothermal LLC^*3, " which engages in geothermal research and development in the Esan area (Hakodate City, Hokkaido). The company is also continuing local coordination in the Azuma and Adatara areas of Fukushima Prefecture jointly with other corporations.
^*3 : Joint venture by RENOVA , Inc., Daiwa Energy & Infrastructure Co. Ltd., and Mitsubishi Materials Corporation.

“Mitsubishi Materials has announced the Medium-term Management Strategy FY2031, which aims to achieve a level of renewable energy generation that matches our electricity consumption, enabling us to become 100% self-sufficient in renewable energy electricity by FY March 2051,” says Kanno. “We want to develop and promote renewable energy and pursue manufacturing mindful of reducing environmental impact, including future geothermal power projects and power generation using other energy sources such as wind power.”

We will work to develop geothermal energy further, knowing it will play a vital role in a decarbonized society by promoting effective use of rich natural resources in Japan.