Introduction – Japan
The third largest economy in the world, Japan, has always played a significant role in modern technology development. Important changes to Japan’s energy policy have occurred following the fallout from the 2011 earthquake and subsequent Fukushima nuclear accident, with focus shifting from nuclear power to renewable sources of energy. A rise in fossil fuel usage from increasing imports of coal and natural gas has led to rising carbon dioxide emissions. This has led to mounting unsustainable electricity prices, which reiterates the need for development of renewable energies.
Unlike much of eastern Asia, Japan significantly lacks domestic reserves of fossil fuels with only 18.8 Mtoe (Million Tonnes of Oil Equivalent) of natural gas, 4 million tonnes of oil and 240 Mtoe of coal. In turn, Japan imported 187 Mt of coal and 99 bcm of natural gas (Billion Cubic Metres of Natural Gas) becoming the first coal and natural gas importer in 2010. Overall Japan constituted to 20% of world coal imports and 12.1% of world gas imports.
Following the devastation of the earthquake and tsunami, Japan made the decision to completely halt the production of nuclear energy. The last nuclear reactor was shut down on 5th May 2012, leaving the country without nuclear power for the first time since 1970. Although the third and fourth reactor of Ōi nuclear plant was restarted in July 2012, the reactor was shut down once again for extensive safety inspections. It was only until late 2015, when both reactors at Sendai Nuclear Power Plant were allowed to restart producing nuclear energy.
Currently, it is estimated approximately 10% of Japans total electricity production is from renewable sources. Following the Fukushima disaster, the shutdown of multiple nuclear plants and growing public concerns of nuclear power, have lead the government to focus on renewable energy sources. The Fourth Strategic Energy Plan indicates that Japan intend on 24% of electricity production to be harnessed from renewable sources in 2030 with an estimated $700 billion to be invested into renewable energy.
Hydropower
With 49.9 GW installed capacity, hydropower is Japans most harnessed renewable energy. Focussing on hydropower has allowed Japan to utilise most of the suitable sites for installing large-scale hydroelectric plants. Currently, the majority of hydropower projects focus on large-scale pumped storage schemes, deviating from smaller schemes in 2011 with Japan having 291MW of hydropower capacity under construction.
As reported by the Japanese Member Committee, the approximate capacity for small-scale hydropower plants would be around 47 TWh/yr. This would constitute to 34% of total hydropower production. In 2011, it was estimated that cost for power per kilowatt-hour was ¥15100, too expensive for further development.
The following diagram illustrates the locations where Japan’s hydroelectric power plants are situated. Blue triangles indicate hydroelectric power plants. Red circles indicate thermal power plants and green squares indicate nuclear power plants.
Pumped-storage Hydroelectricity
More recent hydroelectric power plants in Japan utilise pumped-storage hydroelectricity (PSH). PSH is an energy storage method used for load balancing. By pumping water from lower elevation reservoirs to higher-level reservoirs, the gravitational potential energy of water is stored ready for release during peak energy usage times. Although using PSH results in net consumption of energy, the system is economically more efficient by selling more electricity at higher prices at peak times. The round trip energy efficiency of PSH varies at 70% – 80%.
Typically, the sites used require geographical height and water, usually limiting locations to mountainous areas. A plant of similar capacity is usually quite smaller in size when using PSH, with periods of electricity generation lasting less than 12 hours a day. The following graph illustrates typical PSH’s energy consumption and electricity generation within 24 hours.
Kannagawa Hydropower Plant
Kannagawa Hydropower Plant is set to be the largest capacity hydropower plant in Japan, with a capacity of 6 x 470 MW pump generators totalling 2820 MW. Water from the upper Minamiaki Reservoir is transferred to the lower Ueno Reservoir via a power house to produce electricity. The power station itself is 490 m underground. The reservoir uses PSH to then restore the potential energy for use at peak times. The structure connecting the reservoirs is 6.1 km long with an effective hydraulic head of 653 m. With the first generator commissioned on 22nd December 2005 and the second on 7th June 2012, the remaining four generators are to be completed by 2020. Once complete, Kannagawa Hydropower Plant will have the second largest pumped storage power capacity in the world before Bath County Pumped Storage Station.
Geothermal
A significant portion of Japan’s geothermal potential remains unutilised. For over ten years, geothermal development slowed primarily because it was not economical and lacked social support. However, after the Fukushima nuclear accident in 2011, there was a resurgence of activity, with the Japanese government supporting the development of over 40 projects in 2014. In 2015, several units totalling 6.8 MWe have been commission. At the time, the total installed power generating capacity was 533 MW. The new plants included 3 binary units, a 5 MW plant constructed by Turboden and Mitsubishi, a 1.4 MW plant installed in the Kagoshima prefecture, and a 400 kW unit installed in the Fukushima area. In relation to direct use geothermal, additional components concentrated around heat pumps, which are used for heating and cooling, domestic hot water and snow melting. For example, bathing accounts for 90% of direct-use applications, traditionally found at Japanese-style inns.
Current geothermal situation
In 2003, renewable energies won the support of the national government, however little change came about until 2012, when the government authorised exploration in the Japan’s national parks, and extended membership of its renewable portfolio to a broader variety of geothermal plants. In July 2013, a feed-in tariff system was introduced to promote investment in the geothermal sector. The feed-in tariff will force regional electricity monopolies to buy renewable energy at above-market rates—though a price has not yet been set, according to The Economist.
Japan is one of the most seismically active nations, with its geothermal resources estimated to be able to generate as much as 23 million kilowatts of energy. This represents the third largest amount in the world after the United States and Indonesia. In recent years, several Japanese companies including Fuji Electric, Mitsubishi and Toshiba have pioneered in the development of technology for geothermal power plants.
However, given that only two percent of Japan’s potential geothermal power generation is currently being used, the nation’s power plant technology is being channelled to projects overseas. The reason for underinvestment in this sector has been attributed to the defiance of local communities who are protective of their hot spring industries and associated tourism, with many potential sites for power plants located in government protected areas.
However, three years after the Fukushima nuclear disaster, there has been a decline in opposition and a change of mood, resulting in an increasing number of companies looking to diversify into alternative energy sources such as geothermal power.
Many upcoming projects, including the new Kumamoto plant, are diminishing local opposition to geothermal plants by limiting their operational footprint and working closely with the community. The Kumamoto plant is being developed in partnership with the local enterprise Waita-kai, with a planned maximum output of 2,000 kilowatts to cater for 1,500 households.
Small-scale power plants play a critical role in Japan’s expansion plans, creating a new energy source while supporting the regeneration of local communities, according to Chuo Electric power Co.
Hiroto Kobayashi, an associate professor at Keio University, states: “Such a small-scale geothermal power generation approach is an epoch-making, future-oriented project, which not only is able to exploit the potential of numerous hot spring towns in Japan and allow the supply of energy in the next generation with the lowest environmental impact possible, but also takes the revitalisation of decaying local communities into consideration.”
Currently, multiple new sites across the country are being assessed for suitability with two projects having recently received loan guarantees to start work. Nevertheless, resistance to plant construction from local communities persists, based on fears that the plants will deplete resources for hot springs and pollute the parks. As a result, there is now a focus on small-scale geothermal power plants
Finding the right kind of geothermal energy:
The type of system used to harness geothermal energy varies depending upon enthalpy output of the geothermal site. Hot spring water at 80 to 120°C, power generation can occur using the Kalina cycle system. The cycle is a binary system that utilise geothermal water steam to heat a more volatile liquid, typically water mixed with ammonia. The resultant pressure turns a turbine with a generator, producing electricity.
Japan has about 28,000 hot springs that are naturally discharging or artificially drilled. It is estimated that by using 1,500 hotter wells and springs among them, as much as 723 MWe could be generated without additional drillings.
Most high-temperature fluid resources are located in Tohoku and Kyushu, home to the Kuju volcano. Japan sits above a subduction zone, so the archipelago possesses many geothermal fields with low-enthalpy. These regions have potential for development with organic rankine cycle (ORC) systems and fluid temperatures of 100 C, or 212 F, according to Renewable Energy World.