Power supply stability: The Okinawa experience

NAHA, Okinawa—A decade ago, this isolated southern prefecture of Japan generated 100 percent of its electrical power from diesel-fuel generators. Today, with the price of petroleum products skyrocketing, Okinawa has dramatically reduced its dependence on imported oil and produces only 22 percent of its electricity from diesel generators.

Okinawa Electrical Power Company, the prefecture’s only power company, now relies on coal to produce 77 percent of its electricity. The remaining 1 percent is generated by renewable energy sources, primarily solar and wind power.

Satoru Matayoshi, Okinawa Electrical Power Company’s engineering liaison group leader, says the utility changed its fuel source mix to reduce costs to the company. That keeps costs under control for consumers.

Okinawa Electrical Power Company, which reported operating revenues in the 2005 fiscal year of $1.4 billion and 800,000 customers, has 99 generators, including 11 steam-run units, eight gas turbines, and 80 internal combustion engines. It also has 19 wind turbines and nine solar power generation systems.

While the prefecture—with a population of 1.4 million people and 139 islands—is not energy self-sufficient, its planning and development over the past 12 years has given it a level of energy security that is the envy of other island governments.

Population, demand growth

The coming years, however, pose unique challenges for the Okinawa Electrical Power Company. Unlike Japan’s national trends, the Okinawa prefecture is projecting a fast-growing population and increasing demands on power generation. The company says Okinawa’s population is projected to grow at a rate of .46 percent from 2004 to 2015. In comparison, Japan’s average national population growth rate is projected to be a negative .08 percent during the same period.

Citing figures from Japan Electric Power Survey Committee, the company said that the population of Japan is projected to peak in fiscal year 2007 while Okinawa’s population is forecast to continue growing until 2026. The number of households in the prefecture is also projected to rise by 1 percent during the period, well above the national average of .32 percent.

Okinawa’s Gross Domestic Product is also forecast to grow at a rate faster than the national projection. Japan’s growth rate from fiscal year 2003 to 2012 is projected to grow at a rate of 1.6 percent.

Okinawa’s GPD, in contrast, is forecast to grow by 2.6 percent. Likewise, Okinawa, which has a thriving tourism industry, is projecting visitor arrivals to grow from 5.15 million in 2004 to 6.5 million in 2012.

Balanced against these fast-growth figures is the likelihood that the U.S. military presence, which is particularly heavy in Okinawa, will be trimmed in the coming years. The anticipated reduction of U.S. forces here would result in a 10-percent decline in Okinawa’s energy consumption, said Kyuna Satoshi, Okinawa Electrical Power Company’s public relations officer.

But, he added, the shortfall could easily be filled by projected increase in economic activities. “We project a 2-percent increase in demand a year over the next decade,” Satoshi said, noting that the rate is higher than the national average of 1.2 percent increase during the same period.

To meet future demand, Satoshi said the company plans to rely mainly on thermal generators, which burn either coal or oil. For example, in fiscal year 2011, the company plans to begin operating a new thermal plant in Yoshinoura, on Okinawa Island. The plant will use liquefied natural gas (LNG) as its fuel.

“As the combustion of LNG emits very little carbon dioxide [compared to oil], it will not materially contribute to global warming,” the company said. Likewise, it said the use of LNG is in line with the company’s policy of diversifying the sources of power generation in the prefecture.

Alternative energy sources

While the Okinawa Electrical Power Company has made significant progress in diversifying its sources of power generation, renewable energy remains at a trial level. That is because of it not yet reliable enough, said Hisatake Kishimoto, OEPC business planning liaison officer.

“Its nature is very unstable. Sometimes wind is not strong so [the] quality of power is not so good compared to diesel generators,” he said. Expanding wind plants could jeopardize the utility’s ability to reliably provide power.

Satoshi said that installing and maintaining wind and solar power facilities are more expensive than regular diesel engines. To buy and install one wind turbine alone costs $1 million, he said.

However, the company has to explore this area for two major reasons: to help meet Japan’s commitment under the 1997 Kyoto Protocol, which requires the country to reduce carbon dioxide emission by 6 percent by 2010 and, to save on generation costs, the company hopes to realize savings by mixing its traditional energy sources with renewable energy.

“The cost would be cheaper by doing mixture,” said Matayoshi.

Solar and wind power

Another source of renewable energy in Okinawa is solar power. Okinawa’s sub-tropical location makes it an ideal candidate for solar power projects. Okinawa Electrical Power Company built its first solar energy project in May 1988 in Tokashiki and Zamami in Shimajiri district, a southern outer island.

In 1994, a third solar facility was built on Miyako Island, an outer island further south of Okinawa Island. The fourth and fifth facilities became operational in 1998 in Urasoe and 1999 in Naha City, respectively.

In 2001, three additional solar plants were added: one each in Miyako, Yaeyama, and Kita-Daito.

Wind power is another alternative, but it represents a smaller percentage of the company’s power generation, and it poses some unique challenges on Okinawa, which sits in the middle of the typhoon alley. The company ventured into wind power in 1998, 10 years after its initial try on solar energy.

Three wind power facilities were built that year in Makiminato, Ishikawa, and Ginoza. Another two wind farms were set up in the following year in Tarama and Hateruma, five more in the five succeeding years, the latest of which was in 2003 in Iheya.

Tsuha Yoshinori, the utility’s research and development officer, said that actual generation represents 15 percent of the total capacity of each engine.

Satoshi, the public relations official, said each windmill is designed to withstand up to 150 miles of wind per second. It means that they are strong enough to endure most typhoons, he said.

However, he said that on Miyako Island, which is similar to Saipan and Guam, a windmill had collapsed during a strong typhoon a few years back. If destroyed, it would cost 500 million yen ($4.5 million) to repair one machine, he said.

Aside from solar and wind resources, the company is also examining bio-mass, or using items such as wood chips and sawdust, which can be mixed with sludge left after the combustion of coal, to produce power. Further, the company is considering using “redox flow cell batteries” that are capable of storing a significant amount of electricity, especially at night when the demand is low, for use in the daytime.

Meantime, the company said coal ash from the combustion of coal at thermal power plants would be turned into an organic fertilizer. The ash can be mixed with organic materials such as rice bran, fish meal, and oilseed husks.

Of Japan’s 10 power companies, the Okinawa Electrical Power Company is the only one that does not use nuclear power. The prefecture’s population and electrical consumption needs are too low to justify the cost of investing in a nuclear power reactor.

“Our population doesn’t justify nuclear power use. We’re too small,” said Satoru Matayoshi, the company’s engineering liaison group leader.

He said nuclear power could be tapped for a minimum residential population of 5 million or about four or five times Okinawa’s current size.

Currently, Japan’s nuclear power plants produce nearly 30 percent of the total power generation.

As part of its national long-term energy security program, the government of Japan aims to increase this to 50 percent in 2010 and 57 percent in 2030.

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The writer was a 2006 Sasakawa Pacific Islands Journalism Fellow, and worked on this story in Tokyo and Okinawa while on the fellowship.