Electricity supply from nuclear plants, already down by almost 20 percent following the March 11 earthquake and tsunami, will drop further during peak summer demand as operators shut reactors for maintenance.
Six reactors are scheduled to be offline for checks and maintenance by the end of August. Chubu Electric Power Co. last week shut two reactors out of fear of a natural disaster causing a crisis similar to the one at Tokyo Electric Power Co.’s Fukushima No. 1 nuclear power plant.
The planned shutdowns mean 75 percent of Japan’s nuclear power capacity will be idled or damaged by August when air conditioning demand surges as temperatures can rise to as high as 40 degrees.
Companies and households may have to cut production and usage to avoid blackouts, said Junichi Ogasawara at the Institute of Energy Economics, Japan.
“The area served by Tepco will be severely affected,” said Ogasawara, an economist in the institute’s electric power group. “Through measures such as modifying production shifts, it has been possible to cut power consumption by 15 percent and supply has been just able to meet demand.”
Ten reactors were idled or damaged after the quake and tsunami, accounting for 18 percent of nuclear capacity. By August 40 out of 54 reactors in the country, the world’s third-biggest user of atomic energy, will be shut down unless units idled for maintenance are brought back online.
Tepco, the nation’s biggest power provider with 28.6 million customers in the capital and adjacent areas, may have a shortfall of almost 4,000 megawatts should demand rise to 60,000 megawatts, the peak reached last year, the hottest summer on record.
Tepco expects to have 56,200 megawatts of capacity online by the end of August, Vice President Takashi Fujimoto said Friday. While the company is starting idled thermal power plants to meet supply, its second- and third-biggest fossil fuel stations were knocked out in the disaster.
Simply matching demand and capacity is not enough because power companies typically require a cushion of between 8 and 10 percent of excess electricity supply.
Chubu Electric, which includes Toyota among its customers, expects its excess capacity to fall to as low as 2.1 percent in July and 3.5 percent in August.
“Our reserve capacity could be below 1 million kilowatts, President Akihisa Mizuno said May 10, the day after the company agreed to a government request to shut its Hamaoka reactors to strengthen tsunami defenses. “At that level, we can’t maintain stable power supplies.”
Companies that operate in the area served by Chubu Electric include Sony, which has liquid-crystal display TV and Handycam factories in the region.
The suspension of the Hamaoka plant “may impact our operations, but it depends on how much the shortfall will be,” Atsuo Omagari, a Tokyo-based spokesman for Sony, said Friday. “We’ll assess the impact as we gather more information.”
Sharp Corp., which has its second-biggest plant for making LCDs in Mie Prefecture, another area served by Chubu Electric, said it has not been informed of any shortages.
“We haven’t received a request about the power cut and cannot comment what the impact will be,” said Miyuki Nakayama, a Tokyo-based spokeswoman.
Sharp also has a factory for small-size LCDs in Mie, Nakayama said.
The ability of power companies in western Japan to sell excess power to Tepco is hampered because the country is divided by grids that use different frequencies. Companies including Tepco and Tohoku Electric Power Co. transmit power to the eastern grid at a frequency of 50 hertz (cycles per second), while the rest of Japan uses 60 hertz.
The possibility of longer shutdowns has also been raised by one of the nation’s nuclear agencies. The government should “take strict measures including halting operations” if safety measures are insufficient, the Japan Atomic Energy Commission, which promotes nuclear power development, said in a statement issued May 10.
Prime Minister Naoto Kan said the same day the administration will reconsider plans to increase the use of nuclear power generation to 50 percent. Nuclear power accounted for 27 percent of the electricity generated by the main utilities in the year to March 31, according to the power federation. Thermal power amounts to 49 percent.
Chubu Electric plans to build a seawall at least 12 meters high to protect the station from tsunami and will add more backup power supplies.
The plant, located almost 200 km southwest of Tokyo, sits on the coast adjacent to a fault line where the government estimates there’s an 87 percent chance of an 8-magnitude earthquake hitting within 30 years.
Kansai Electric Power Co. is closing down three reactors with a total capacity of 2,876 megawatts, while Tepco is closing two in August, with combined output of 2,456 megawatts.
Hokkaido Electric Power Co. plans to idle one 579-megawatt reactor.