Toppled turbine fans safety probe 

Attention has been drawn to the safety of wind power generators following an incident in which a windmill toppled over in Higashidorimura, Aomori Prefecture earlier this month.

Wind power generation has emerged as a fast-growing source of energy, prompted by the deregulation of the electricity industry and the need to tackle global warming.

But most of the wind turbines used in this nation are made overseas, with many coming from Europe. Therefore, when determining safety standards for turbines, this nation’s weather and terrain are not taken into consideration and, after construction, the turbines are not thoroughly inspected.

An official from the Economy, Trade and Industry Ministry’s Nuclear and Industrial Safety Agency, who inspected Iwaya Wind Farm on Jan. 10, two days after the accident there, expressed surprise that the accident occurred, saying, “How could it have fallen down like this?”

The 68-meter wind power generator toppled from its base, exposing the steel reinforcement rods meant to have secured it.

The 25 generators at the wind farm are set at intervals of 100 meters to 200 meters in a curved line. The No. 11 generator, which was located near the middle of the row, fell down.

The wind turbine’s structure is designed to withstand winds of up to 216 kph, more than sufficient to cope with the maximum instantaneous wind speed of just 90 kph recorded just before the accident by a nearby wind meter.

Experts and officials said it was unlikely wind caused the generator to fall down. “The concrete of the base cracked and the wind turbine broke from its moorings,” the agency official said.

The possibility of design and construction error has emerged, but there is no safety standard for constructing wind power generators in this nation.

The requirement that turbines be able to withstand a wind speed of 216 kph is based on the Building Standards Law. The regulation was set for high-rise buildings.

Regarding the construction of the base, there is only a regulation based on the Electric Utility Law, which stipulates that the base of an electric generation facility must be structurally sound. Construction methods are left up to each operator and constructor, and the technical know-how used for constructing steel towers is applied when installing a wind power generator.

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European standards

The generator that fell down was made in Denmark and was installed by a major domestic construction company.

There were 1,050 wind power generators across the country as of the end of March 2006. Of them, 788, or 75 percent, were made overseas. Three prefectures have a total of 79 generators made by the same Danish maker of the generator that toppled over. Construction of wind power generators for commercial use started in this nation in 1995, but turbine makers still depend heavily on European technology.

The international safety standard for wind turbines is based on the average wind speed found in Europe, among other factors.

In 1998, there was an accident in India in which 129 wind power generators were destroyed when a powerful cyclone hit an area. But Japan Wind Energy Association Director Hiroshi Nagai, 53, said, “Cases in which wind power generators are destroyed are rare worldwide.”

But conditions differ greatly between Europe, where the terrain is mainly flat and the wind direction–driven by circumpolar westerlies–is stable, and this nation where the terrain is hilly and typhoons often strike.

In September 2003, wind power generators made in Denmark and Germany were hit by a typhoon in Miyakojima island in Okinawa Prefecture. Three were destroyed and seven were damaged.

After the accident, new safety measures were called for, and in September 2004, university professors joined officials from electricity companies and wind power generator makers on a subcommittee of the Japan Society of Civil Engineers tasked with formulating high-wind-resistant designs for wind power generation facilities and to start formulating nationwide guidelines for relevant structural design.

One of the subcommittee members, Assistant Prof. Hiroshi Katsuchi of Yokohama National University, 44, who specializes in wind-resistant engineering said, “The safety of wind power generators can’t be guaranteed in the current environment in which no clear design guidelines exist, and guidelines for building chimneys are being used instead.”

The subcommittee will compile new guidelines in this spring, but the agency said it could not predict to what extent safety rules would be improved before the guidelines are made.

The government’s safety inspection system for wind power generators also has surfaced as an issue.

Currently, the government checks only the results of strength calculations when construction plans are submitted.

The agency said operators have to formulate their own safety management systems.

The operator of Iwaya Wind Farm, Eurus Energy Iwaya based in Higashidorimura, said it inspected its 25 generators, including the one that fell down, in checks that ran from October to December. However, it said it did not check the bases.

Assistant Prof. Kozo Tsumura, 48, of Hirosaki University’s science and technology faculty, who specializes in concrete engineering said: “It’s almost impossible to reconfirm the safety of a wind power generator’s base once it’s concreted. Inspections by the government and a third-party organization are necessary to avoid substandard design and construction.”

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Winds of change

The number of wind power generators in the country has rapidly increased since about 2000.

The number increased from 198 in fiscal 1999 to 1,050 in fiscal 2005. Total generating capacity has reached about 1.08 million kW, 13 times more than the 80,000 kW available in fiscal 1999.

One reason for this growth has been the liberalization of the electricity market. In March 2000, liberalization of electricity retail sales rules meant that nonpower companies, which had only been allowed to sell electricity to factories with electricity demands of at least 2,000 kW, could sell power to small factories with electricity demands of as little as 50 kW.

Wind power generation has attracted attention as effective strategy for tackling the global warming problem, prompting firms other than electricity companies to enter the market.

The Economy, Trade and Industry Ministry plans to increase the nation’s wind power generating capacity to 3 million kW, about three times the present level, by fiscal 2010.

Prior to the liberalization, the International Trade and Industry Ministry inspected wind power generators after they had been constructed. But in 2000, the Electric Utility Law was revised to promote deregulation, and inspection of sites became the responsibility of operators.

Liberalization made easier for newcomers to enter the market, but insufficient measures were taken to guard against shoddy design and construction.

By Keita Ikeda and Kojiro Tanikawa
Yomiuri Shimbun Staff Writers

yomiuri.co.jp