AS ONE of the most developed countries in the world, and home to an energy hungry population of 120M, Japan has substantial power requirements to meet. With few energy resources of its own it is dependent on imports of oil, coal, gas and other supplies.

After the oil price shocks of the 1970s, the country actively pursued large scale construction of hydro power but has since exhausted almost all of its larger hydrological sites. The country’s mountainous topography now makes it difficult to find further suitable places to develop economically attractive hydro power schemes. As a source at Japan’s Federation of Electric Power Companies (FEPC) commented, about 66% of Japan’s hydro power potential has already been developed and little more would be developed in future.

Declining output

At the end of the financial year (FY) 2000 (to March 2001) Japan’s hydro power stations, including pumped storage and conventional hydro schemes, totalled 44,800MW of installed capacity. But this figure has declined over the past two decades. Hydroelectric generation has fallen as a proportion of total power generation in Japan and the country has looked to nuclear power, along with liquefied natural (LNG) gas and coal-fired generation, to satisfy its massive growth in electricity demand.

In 1980, hydro power was the second largest source of electricity in Japan. With an annual output of 84.5TWh, it accounted for 17% of total electricity generation compared with oil-fired generation totalling 208.9TWh (43%). By 2000, Japan’s power generation picture had changed sharply. Nuclear energy, coal and LNG all had grown rapidly in importance while hydroelectric power output only grew marginally. In 2000, hydro was the fourth largest source of electricity in Japan, with 96.9TWh output accounting for 10% of the total 939.6TWh of generation.

According to Japanese power companies‚ long term generation forecasts predict that the share of hydroelectricity in the generation mix will be maintained, while the share of nuclear energy is due to grow as oil-fired generation further declines. By 2010 hydro power generation is forecasted to reach 99.3TWh, representing 9% of total power output forecasted at 1089TWh for that year.

According to FEPC statistics, 23 of Japan’s 25 largest hydroelectric schemes are pumped storage projects: the largest is Kansai Electric’s 1932MW Okutataragi scheme. In Japan pumped storage schemes use both off peak coal and nuclear energy to refill reservoirs. Some use natural water flow and pumped water to fill the storage reservoirs while others are designed to use pumped water only.

Pumped storage projects have grown rapidly in numbers since the 1970s, and this programme will continue in future as power companies plan development of pump storage capacity to match their planned increase in nuclear and coal-fired generation.

Japanese power companies plan to construct new pumped storage schemes totalling 6400MW by 2010. Further projects amounting to 7400MW will be built between 2011-20, giving a combined total of 13,800MW for large schemes over 200MW over the next two decades.

Tokyo Electric Power Co (Tepco), Kansai Electric Power Co and the Electric Power Development Corporation (EPDC) are the country’s main generators of hydroelectric power. Tepco, the world’s largest private power company, is Japan’s largest operator of hydro power plants totalling 8508MW, of which 5453MW (64%) are pumped storage schemes. Not all Tepco hydroelectric plants are located within the company’s traditional Greater Tokyo power supply area. A number have been built in the supply areas of other power companies, an arrangement that Tepco has also used to build nuclear and thermal power plant facilities. In FY 2000, hydro power plants accounted for 5.1% of its total 265.5TWh of power generation.

Tepco plans to construct two large pumped storage schemes totalling 4300MW of installed capacity over the next two decades. The 2700MW Kannagawa project will begin commissioning in 2005 while the 1600MW Kazunogawa pumped storage scheme will begin commissioning in 2011.

While Tepco has the largest hydro power generation capacity in Japan, Kansai Electric generates the most electricity from hydro power dams among Japan’s ten regional power companies. In FY 2000 the company’s hydro power plants accounted for 11.46% of its total 125.6TWh power generation.

Kansai Electric plans to construct a fifth large pumped storage scheme to begin commissioning in 2011. The 2280MW Kaneihara project will have a maximum discharge of 531m3/sec and an effective head of 514m.

Pumped storage

Nine out of Japans ten regional electricity companies operate hydro power plants. The exception is Okinawa Electric Power Co which relies on thermal power. Apart from the regional power companies, large hydro plants are owned and operated by the state-run EPDC which was set up to supply wholesale thermal and hydro power electricity to the regional power companies.

In fact, EPDC is Japan’s third largest hydro generator after Kansai Electric and Tepco, while the corporation’s total hydro power capacity is the second largest in Japan in terms of installed generating capacity. Its hydro power plants total 8261MW of which 4440MW (53%) are pumped storage schemes.

EPDC plans to construct two large pumped storage schemes and one conventional hydro power dam with a total combined 2400MW installed capacity over the next two decades. The first scheme to enter service will be the 200MW Okutadami conventional dam which will begin commissioning in 2003. This will be followed by the 400MW Tokuyama pumped storage scheme, due for commissioning in 2008, with the 1800MW Yunotaniyosui scheme hot on its tail in 2011.

The other power company planning a large expansion in hydro power output over the next two decades is Chubu Electric, which serves the central region of Honshu island around the city of Nagoya which lies between Tokyo and Osaka.

In FY 2000 hydroelectric plants accounted for 7.6% of its total 119.7TWh power generation. The company’s hydro power plants total installed capacity is 5213MW of which pumped storage schemes amount to 2280MW (43.7%) of capacity.

Chubu Electric’s largest hydro power plant is the 1500MW Okumino pumped storage scheme commissioned in 1995 which has a maximum discharge of 375m3/sec and an effective head of 486m. It also plans to construct two large pumped storage schemes with a total combined 3100MW installed capacity over the next two decades. Commissioning of the 1300MW Kawaura project will begin in 2007 and the 1800MW Kisochuo pumped storage scheme in 2016.

While power companies and EPDC develop mostly large and medium size hydroelectric schemes, small, mini and micro hydroelectric projects are developed under prefectural and local governments. Regional power companies also develop some small and mini hydro schemes. Construction of mini hydro power projects is encouraged by central government subsidies.

Pumped storage data