April 15, 2026
TOKYO – This is the second installment in a series of articles examining the ideal infrastructure for building vibrant regions, with the future of Kyushu as well as Yamaguchi and Okinawa Prefectures in mind.
As I drove through the town of Kokonoe, Oita Prefecture, admiring the magnificent Kuju mountain range surrounding the area, a building spewing out thick white steam came into view. This was the Hatchobaru geothermal power plant, which boasts an output of about 110 megawatts, more than any other geothermal plant in Japan, which has an abundance of volcanic activity.
“Most of this equipment is from 40 to 50 years ago, when this plant came online,” Hideki Yoshigai, head of the plant’s administrative group, said proudly. “But even now, it reliably operates 24 hours a day, 365 days a year.” The plant’s first unit began operating in 1977, and the second unit did so in 1990. The two units continue to supply enough electricity for about 192,000 ordinary households.
Geothermal power generation involves extracting extremely hot steam and water from depths of between 1,000 meters and 3,000 meters underground. The steam is separated from the water and directed to drive turbines. “We’ll keep this plant running for another 50 years,” said Yoshigai, 53.
Unlike other renewable energy sources such as solar and wind power, geothermal power is not affected by weather conditions. Consequently, there are high expectations that geothermal power could become a major source of domestically produced energy for Japan, which currently has a low level of energy self-sufficiency and relies heavily on imports.
The many volcanoes of Kyushu make the region a jewel in the nation’s geothermal energy crown. Fukuoka-based Kyuden Mirai Energy Co., a subsidiary of Kyushu Electric Power Co. group, operates six geothermal power plants, including Hatchobaru. Their combined output accounts for about 40% of all geothermal electricity generated in Japan.
Kyuden Mirai is also pushing ahead with efforts to develop geothermal power plants. In 2024, the company began constructing a power plant in Kirishima, Kagoshima Prefecture. It also is conducting field surveys with a view to developing power plants in six other locations.
“Geothermal power is a precious baseload power source,” former Kyuden Mirai President Yutaka Mizumachi said.
Lagging behind
According to government estimates, the potential power that could be generated from Japan’s geothermal resources is about 23,000 megawatts, the third highest in the world after the United States and Indonesia. However, only about 2% to 3% of this is currently being tapped. In terms of electricity generating capacity, Japan lags behind those nations.
This lag is partly because the land suitable for geothermal power generation using current methods is limited, as most of the nation’s geothermal resources are located inside national parks and other areas where development is difficult. The process from surveying to activating a geothermal power plant takes about 10 years, a length of time that is a major sticking point compared with other renewable energy sources.
Most of the components and equipment for wind and solar power are manufactured overseas, so even if Japan increases its electricity output from these sources, the nation’s reliance on other countries will remain unchanged. By contrast, Japanese companies hold about 70% of the global market for manufacturing geothermal power equipment. Mitsubishi Heavy Industries, Ltd., for instance, makes turbines for geothermal power generation in Nagasaki Prefecture.
Yasuhiro Fujimitsu, a professor at Kyushu University’s Graduate School of Engineering and head of the Geothermal Research Society of Japan, said, “If new technologies can expand our use of geothermal power, it will, in a very real sense, become a locally produced and locally consumed energy source.”
Harnessing water temperature gaps
In the sea, another new potential energy source waits quietly to be unlocked.
Kumejima Island is a 40-minute flight from Okinawa Island. On the eastern part of Kumejima is a massive apparatus equipped with multiple pipes of varying thickness. Major shipping firm Mitsui O.S.K. Lines, Ltd. and other companies have set up this demonstration facility with the aim of starting to commercialize ocean thermal energy conversion (OTEC). Saga University and Xenesys Inc., a heat exchanger maker based in Imari, Saga Prefecture, are also involved in this project.
This power generation method uses energy from the sea to make electricity. It works based on the difference in temperature between surface seawater and deep-sea water. A CFC substitute or other liquid with a low boiling point is heated and evaporated by the warm surface water to drive the turbines. Cold deep-sea water then cools the vapor back to a liquid, which is circulated back through the system. This also has the special benefit of making it possible to effectively use deep-sea water in agriculture and aquaculture.
Mitsui plans to capitalize on this demonstration facility to build a 1,000-kilowatt OTEC plant and, by around fiscal 2031, make it the first such plant in the world to be fully commercialized.
Demand set to swing upward
Japan’s energy demand had been trending downward as the population declined and people became more conscious about saving electricity. However, demand is set to increase in the years ahead.
In January, the Organization for Cross-Regional Coordination of Transmission Operators (OCCTO), a government-authorized corporation, released domestic energy estimates that forecast this demand would start ticking upward after bottoming out in fiscal 2025. OCCTO predicted that demand in fiscal 2035 would be about 5.3% higher than it was in fiscal 2025.
The surge in construction of semiconductor plants and data centers that will consume vast amounts of electricity are expected to be a major factor in this change.
“Renewable energy sources are one of Kyushu’s strengths,” said Keisuke Matsushima, a former senior official at the Kyushu Economic Research Center. “If these sources could be skillfully combined and their respective advantages exploited to the fullest, they could give Kyushu’s industrial development a shot in the arm.”