Sumitomo Corp., JGC Corp. and Electric Power Development Co. and other companies are cooperating with the government to sell geothermal power technology overseas.

Twenty companies, including Itochu Corp., Mizuho Corporate Bank Ltd. and Sumitomo Mitsui Banking Corp., have set up a working group to promote the Japanese technology, said Hiroyuki Kudo, general manager of the international cooperation division at the Energy Conservation Center, which serves as the group's secretariat.

The group plans to first pursue opportunities in Indonesia, where demand for geothermal power is forecast to increase, said Satoshi Nakamura, assistant director of the Ministry of Economy, Trade and Industry's Agency for Natural Resources and Energy.

Japan and Indonesia have agreed to cooperate on building infrastructure for geothermal power, Nakamura said. Officials discussed geothermal power and other projects at an economic forum Thursday in Tokyo. Indonesia's government aims to boost its geothermal power capacity to 9,500 megawatts by 2025 from the current 1,200.

The Japanese group first met Oct. 8, with METI and the Japan Bank for International Cooperation attending as an observer.

Developing power from sources underground such as hot springs is estimated to cost between $3,000 and $4,000 per kilowatt, according to Tadashi Kaneda, head of the overseas division at Fuji Electric Systems Co., a unit of Fuji Electric Holdings Co.

A 100 megawatt geothermal plant would cost between $300 million and $400 million, Kaneda said, meaning Indonesia's geothermal market may be worth as much as $38 billion within 15 years, based on Indonesian government targets.

"Japan's technological strength can set itself apart from others," Kaneda said.