• Geothermal Power Generation Accident

Comprehensive Safety Measures a Prerequisite for Widespread Use

An accident that caused local damage occurred at a site being surveyed for the generation of geothermal power, which is considered to be one of the most promising renewable energy sources. It is essential to remember that ensuring safety is a prerequisite for the spread of geothermal power generation.

The government and the operator should investigate the cause of the accident and take thorough measures to avoid a recurrence.

On June 29, large quantities of steam began spewing from a geothermal power generation research site in the town of Rankoshi, Hokkaido. Water that accumulated at the site was found to have arsenic levels that significantly exceeded safety levels. Furthermore, air in the vicinity reportedly contained toxic hydrogen sulfide.

Nearly two months on, steam continues to gush from the site of the accident. About 20 people, including nearby residents, have complained of health problems likely linked to factors such as hydrogen sulfide poisoning. The accident has caused immeasurable anxiety among the local community.

On Aug. 12, Mitsui Oil Exploration Co., a subsidiary of Mitsui & Co. and the operator of the development project, began injecting cooling water into wells at the site in a bid to suppress the steam, saying it aimed to backfill the wells entirely by late August. The first thing to do is bring the situation under control expeditiously.

In geothermal power generation, magma-heated steam is extracted from the ground and used to turn turbines that generate electricity. There is a danger of toxic gas leakage during this process, so it is common practice to install control devices that seal off wells to prevent the release of gases if an anomaly is detected.

The accident occurred when drilling reached about 200 meters below ground being surveyed to determine its suitability for geothermal power generation. Mitsui Oil Exploration said it had planned to install control equipment after drilling reached 700 meters.

It is essential to verify whether this plan was appropriate.

It has also been pointed out that there was a delay in the initial response to the accident. The company did not immediately release information about health hazards. It also took time to procure the necessary machinery and equipment needed to stop the blowout. The firm’s crisis management system must be thoroughly inspected.

Unlike solar and wind power, geothermal power generation is unaffected by weather and has a stable output. It also emits relatively fewer greenhouse gases. The government has positioned geothermal power generation as a promising power source in terms of decarbonization, and is focusing on its widespread use.

Japan, which has many volcanoes, is thought to have the world’s third-largest geothermal resources after the United States and Indonesia. Currently, Japan’s geothermally generated electricity capacity is less than that of a single nuclear reactor. There is ample room for expansion, but the recent accident could throw cold water on the utilization of geothermal power generation.

It is vital for the government to be involved in the investigation into the accident as much as possible. It is hoped the government will take the lead in strengthening safety measures, such as by considering initial response steps to deal with unexpected situations, based on lessons learned from the accident.

(From The Yomiuri Shimbun, Aug. 18, 2023)