JFS Newsletter No.88 (December 2009)
Hatchobaru Geothermal Power Plant (110MW, Kokonoe Town, Oita Prefecture)
Copyright: Prof. Sachio Ehara
The temperature of the Earth's inner core is about 6,000 degrees Celsius (C) -- almost the same as the surface of the Sun -- and it is estimated that 99 percent of Earth's volume is at a temperature of more than 1,000 degrees. Thus, there is an enormous amount of geothermal energy in the planet's interior that could potentially be tapped; an obvious manifestation of this is the ongoing volcanic eruptions and hot springs found around the world. In light of the issues of global warming and energy problems, more effective use of geothermal power should be closely examined as a significant source of energy.
Located on the Pacific Ocean's volcanic "Ring of Fire," Japan has the third largest pool of geothermal resources in the world, but it has not yet made the most effective use of these resources, even while there is an increasing need for development of renewable energy sources. In this issue of the JFS newsletter, we provide an overview of the current situation and future challenges of geothermal energy use in Japan, mainly based on an interview with Professor Sachio Ehara, of the Kyushu University Graduate School of Engineering, whose specialty is geothermics, and who also serves as the president of the Geothermal Research Society of Japan.
The Potential of Geothermal Power as an Energy Source
According to the latest data from Japan's National Institute of Advanced Industrial Science and Technology (AIST), the United States has the highest capacity for geothermal energy production, estimated at 30 million kilowatts (kW), or 30 gigawatts (GW). Indonesia is second, with 27.79 million kW (27.79 GW), followed by Japan, with 23.47 million kW (23.47 GW), while the Philippines and Mexico both have six million kW (6 GW) each in capacity. So, Japan ranks among the world's top three countries for geothermal energy potential.
In one study using a new technology called "enhanced geothermal systems" (EGS), researchers succeeded in extracting heat for the generation of electricity by drilling down to the depth of magma and hot dry rocks. When this technology comes into practical use, it will be possible to tap into a very large amount of geothermal energy.
The main geothermal sources in Japan are located along the East Japan Volcanic Belt (in the districts of Hokkaido, Tohoku, Hokuriku, Chubu, and the Izu Islands) and the West Japan Volcanic Belt (in the districts of Kyushu and Chugoku), which shows the close correlation between geothermal energy and volcanic areas.
Geothermal energy comes in various forms, and a number of ways are available to utilize it, depending on temperature, as follows:
- High-temperature geothermal resources (200 to 350 degrees C):
Steam at high temperatures and pressures is accessed by drilling into geothermal reservoirs located at about 1,000 meters below the Earth's surface, and then used to rotate turbines to generate electricity.
- Low-to-medium temperature geothermal resources (below 200 degrees C):
In addition to direct use of hydrothermal water coming from underground in the form of hot springs or used for heating, geothermal liquids, such as pentane and ammonia water (which have a low vaporizing point), can be used for binary-cycle power generation to heat up and rotate turbines with steam to generate electricity.
- Ground heat (10 to 20 degrees C):
As shallow ground temperatures are relatively constant through the year, ground heat obtained using a heat pump can be used to melt snow on roads and in cooling/heating systems for buildings.
Geothermal energy also has several advantages as an energy source. First, it can be domestically accessed and is natural. Second, geothermal power plants have low carbon dioxide (CO2) emissions and normally zero emissions when used to generate electricity, unlike thermal power plants that require other fuels. Even if CO2 emissions associated with plant construction are included, CO2 emissions per kilowatt-hour (kWh) from geothermal plants are 15 grams, the second lowest after hydropower plants, at 11.3 grams, and lower than those from solar- or wind-power plants. Third, being unaffected by natural surface conditions such as weather, the operating rate of geothermal plants can be as high as 70 percent compared with 12 percent for solar-power plants and 20 percent for wind-power plants. Moreover, geothermal plants can supply reliable base-load power, as they can generate electricity constantly on a 24-hour-a-day basis.
The Present Status of Geothermal Electricity Generation in Japan
The first geothermal-powered electricity was generated in 1904 in Italy, and it was being used in 25 countries in 2008, with a total installed capacity of 10 million kW (10 GW). Because many countries have been making efforts to increase their geothermal generating capacity as a measure to reduce oil dependence and greenhouse gas emissions, it is estimated that geothermal power generation will be operating in 46 countries in 2010, with a total capacity of 13.5 million kW (13.5 GW).
Geothermal power generation in Japan, with an initial output capacity of 1.12 kW, was first successfully done in 1925 in Oita Prefecture. Since then, development of geothermal resources has been done mainly in the districts of Tohoku and Kyushu, and there are now 20 geothermal power plants in 18 areas, with a total installed capacity of 535,250 kW, accounting for about 0.2 percent of the total electrical power generation capacity in Japan. Geothermal power plants have a slightly larger share (0.3 percent) of generated output due to their high operating rate, and the actual output of geothermal power generation in fiscal 2007 was larger than that of solar power and wind power.
AIST estimates that potential low-temperature geothermal resources in Japan (53 to 120 degrees C) suitable for hot spring water-power generation could be 8.33 million kW (8.33 GW). Currently, development of a hot spring water-power generation system with a capacity at the 50-kW level is underway, with the aim of completion in fiscal 2010. In this system, unused high-temperature hot spring water above bath-use temperature is used to generate electricity, and also the used cooling water can be supplied for bath, hot water, and heating systems in hot spring facilities. Thus, this system creates a win-win situation both for power producers, who have no development risk, and owners of hot spring facilities who would enjoy energy cost reduction. As an energy vision, a total output of 120,000 kW from hot spring water-power generation is projected in 2020.
The geothermal energy a heat pump can utilize is more than 3.5 times the amount of electricity needed to operate the heat pump. For this reason, the utilization of ground heat is being widely promoted around the world, especially in the United States and Sweden, but Japan has hardly made any use of its available ground heat resources. Even so, the use of geothermal air-conditioning systems for residential use in Japan has been increasing since around 2003. Furthermore, the nation's first district heating and cooling (DHC) system utilizing geothermal energy will be introduced in the Tokyo Sky Tree District in Sumida Ward, Tokyo, where the 634-meter tower named the "Tokyo Sky Tree," soon to be one of the world's tallest radiowave transmission towers, is under construction and due for completion in 2012.
Most of Japan's presently operating geothermal electricity generation facilities were built before 1996. Since then, only one, the Kuju Geothermal Power Plant, with a 2,000-kW output, was built in 2000. The country was in sixth place in the world in geothermal power generation capacity in 2000, and it dropped to eighth in 2009. Despite its rich geothermal resources, why has Japan's geothermal use remained static for over a decade?
Tapping into geothermal energy entails risks from exploitation of underground resources and huge initial investment costs. Therefore, the cost of generating electricity from newly developed geothermal energy sources is usually more expensive than from conventional sources. Moreover, a drastic budget cut to the support of geothermal energy development during this period directly contributed to the slump in utilization of this energy source.
After the 1973 oil crisis, the Japanese government set up the "Sunshine Project" and conducted long-term, comprehensive, and systematic research and development on the supply of clean energy including from geothermal sources. The project brought some progress in the development of geothermal power generation facilities, but geothermal energy development started to face difficulties after it was excluded as a new energy source when Japanese politicians enacted the Law Concerning Special Measures to Promote the Use of New Energy in June 1997, which was meant to ensure energy security and tackle global warming. This exclusion under this new law brought budget cuts in geothermal research and development. Moreover, geothermal-related generation systems, except geothermal binary power generation, were also ruled out from the category of new energy sources under the Law on Special Measures Concerning New Energy Use by Electric Utilities -- better known as the Japanese Renewable Portfolio Standard (RPS) Law -- which was implemented in June 2002. This further aggravated the situation surrounding the use of geothermal energy in Japan.
One of the fundamental disadvantages for the use of geothermal energy in Japan is that the most promising spots for energy exploitation are in protected areas, because 82 percent of them are located in special or special protection zones in national parks and quasi-national parks. In these areas, it is prohibited to conduct any development, as laid out under a 1972 agreement between the Ministry of International Trade and Industry and the Environmental Agency (now the Ministry of Economy, Trade and Industry and the Ministry of the Environment, respectively). Even though the capacity of geothermal resources -- even when those in protected areas are excluded -- is estimated to be about 4.25 million kW, the development of geothermal energy use involves a long lead time in order to meet the requirements under the Hot Springs Act, the Environmental Impact Assessment Act, the Electricity Utilities Industry Law, and so on, which leads to increased development costs and high power generation costs per kilowatt-hour.
Nonetheless, Japan has about 28,000 geothermal hot springs, and their geothermal heat is already, in some ways, practically utilized by people for bathing, and the hot springs continue to attract tourists. Drilling wells for the development of geothermal power generation facilities in such areas are most often opposed by local tourism industries, that are concerned with possible adverse impacts on the hot springs. With over 40 years of experience in Japan in the development and operation of geothermal power generation facilities, however, the scientific knowledge has been gained on how to develop these resources without such adverse impacts. With these data and knowledge in hand, it is necessary for scientists and developers to work to win the understanding and support of local hot spring industries.
After reflecting on these barriers to more effective exploitation of geothermal energy and development, the Geothermal Research Society of Japan submitted a proposal on October 31, 2008, for better utilization of geothermal energy and to see the nation grow to be a geothermal superpower. The President of the society, Prof. Ehara summarized the recommendations of the proposal, as follows:
- Policies should be established to promote the development and utilization of "clean domestic energy" for energy security and measures against global warming. As other countries in the world already emphasize the development of renewable energy, including geothermal, high numerical targets should be set and supporting policy measures should be set, in order to keep up with this worldwide movement, and Japan should set better policies in support of renewable energy development. In terms of geothermal energy development specifically, problems with legal restrictions have to be resolved and supporting measures should be established.
- New rules need to be established to support geothermal energy development in national parks and close to hot springs.
- Advanced technology for the development and utilization of geothermal energy should be developed and promoted, and Japan should restart the development of geothermal technologies that have been "on hold" since the mid-1990s.
Japan's Agency for Natural Resources and Energy released the interim report of the working group on geothermal power generation on June 9, 2009, which summarizes the current conditions and challenges, and proposes future measures to promote the development of geothermal power generation.
The Japanese government started a new program on November 1, 2009, which requires power companies to purchase surplus electricity from residential solar-power system owners, and almost doubled the price to purchase electricity from home owners with solar power generation systems to 48 yen/kW. This represents the very start of a feed-in tariff (FIT) system in Japan.
Japan's new administration, led by the Democratic Party of Japan, declared the target of a 25-percent reduction of greenhouse gases emissions in 2020 compared to the 1990 level. In order to achieve this, even more rigorous policies are required to promote renewable energy use. FIT, in particular, will provide a strong incentive for use as a system, and it is expected to be adopted for use with other renewable energy sources. Geothermal power generation cost was estimated to be about 9.2 to 21.7 yen/kWh in the interim report by the working group on geothermal-power generation, which would be effective enough to produce a cheaper purchase price than solar-power generation under the FIT program.
From the long-term perspective, it is necessary for Japan to start studying electricity generation with enhanced geothermal systems (EGS), which the United States and Australia have already started researching.
In the end, there are high expectations that geothermal energy will again come into the spotlight. Its development and utilization as a clean domestic energy source is anticipated once the disadvantages are overcome and promotion of it is enforced, as recommended in the proposal and interim report of the working group on geothermal power generation mentioned above.
Written by Kiyoshi Koshiba