Chiaki Toyoda / Yomiuri Shimbun Staff Writer
TEPCO implemented its emergency electricity supply measures this week not just because of higher-than-predicted temperatures, but also as a result of structural changes in the pattern of the nation’s demand for electricity.
Tokyo Electric Power Co. took the emergency measures for the first time in 17 years as the daily peak in electricity demand reached records this summer.
With the Kashiwazaki-Kariwa nuclear power station still shut down in the wake of the Niigata Prefecture Chuetsu Offshore Earthquake, TEPCO has been on a tightrope in terms of balancing supply and demand.
The company finally had to make use of measures it sees as its last resort once it became clear its initial estimate for the maximum demand for power proved to be a miscalculation.
Early Wednesday morning, the mood at TEPCO’s central supply control office in the Uchisaiwaicho area of Chiyoda Ward, Tokyo, became very tense. In the office controlling the distribution of power supplies in TEPCO’s service areas, one official said, “If it continues like this, there’s no way 61 million kilowatts is going to be enough.”
In the Otemachi district, one of the major business centers in the ward, the temperature had already risen above 30 C by 7 a.m. and was continuing to rise.
From past experience, it is believed as a rule of thumb that when the temperature in Tokyo exceeds 30 C, every subsequent one degree rise in the temperature increases the total electricity demand by 1.7 million kilowatts.
In accordance with this rule of thumb, TEPCO was already down to its last 1.6 percent of supply capacity.
When extremely hot days and tropical nights continue for extended periods, the asphalt of roads and walls of buildings do not cool down sufficiently at night, resulting in high room temperatures in office buildings from early in the morning.
This heat-accumulating effect boosts the demand for power. Between 8 a.m. and 10 a.m. Wednesday the total power demand rose at a ferocious pace–by more than 8 million kilowatts per hour at the peak of the surge.
This meant the overall demand was enough to consume the hourly output of a large nuclear power station in just 10 minutes.
At 11:30 a.m., TEPCO Executive Vice President Takashi Fujimoto, who is responsible for power distribution, decided to take the emergency measures, which he had tried to keep in reserve if at all possible.
One of the measures involves asking some companies to accept a cut in their power supply in accordance with their supply contracts, which stipulate that TEPCO is allowed to adjust the amount of power supplied.
Another measure taken was the emergency activation of the Shiobara hydroelectric power plant in Tochigi Prefecture, whose operating license has been suspended since data falsification at the facility came to light.
The requests for large-scale users to accept a reduction in power supply has restricted production at these companies.
TEPCO took this measure twice in 1987 and four times in 1990.
It is seen as the absolute last resort for TEPCO because the measure results in it cutting the supply of its product, which runs contrary to TEPCO’s commercial obligations.
Use of the Shiobara plant, meanwhile, may draw criticism from local residents.
Shortly after 11 a.m., total demand surpassed 60 million kilowatts. TEPCO revised upward its prediction for Wednesday’s maximum demand from 60 million kilowatts made the previous day to 61 million and then again to 61.5 million.
In addition to the two measures, TEPCO was forced to use a third measure–increasing its access to power supplied by other electric power companies.
Shortly after 11:30 a.m., TEPCO began making urgent requests to 23 plants in Tokyo and surrounding areas that have contracts allowing TEPCO to reduce their power supply when deemed necessary.
By fax and telephone, TEPCO asked the plants to refrain from using electricity as far as possible between 1 p.m. and 5 p.m. that day.
Most of the 23 plants were manufacturers of nonferrous metals that consume large amounts of electricity.
At at about 1:10 p.m., the Shiobara plant started operating at an output level of 300,000 kilowatts.
Shortly before noon, TEPCO notified the Economy, Trade and Industry Ministry of the situation. At 12:45 p.m., the ministry held an urgent press conference to ask companies and people to cooperate in saving electricity.
In the ministry’s head office building, lights were turned off in lobbies and corridors, and coffee machines were turned off and the temperature setting of air conditioners raised from 28 C to 30 C.
At the request of the ministry, companies turned off lights in offices and took other measures to cooperate.
But ordinary households were hard to reach in calling for cooperation. Not only that, the final game of the national high school baseball championship was about to start at 1 p.m.
In recent years, TV sets do not consume as much electricity compared with the past, because of the spread of TVs with liquid crystal display screens that consume only about two-thirds the electricity of a comparable cathode-ray tube TV.
But in many households, people will have watched the game in air-conditioned rooms. While TV sets consume less than 10 percent of the total electricity used by ordinary households, the figure for air conditioners is 25 percent, higher even than the 15 percent used by refrigerators and lights.
Total electricity demand spiked at 61.47 kilowatts shortly after 2 p.m. But shortly after 3 p.m. when the baseball game ended, total demand fell away and failed to exceed TEPCO’s revised forecast of 61.5 million kilowatts.
Small-user demand rises
One of reasons of the tight balancing act between the supply of and demand for power in the Tokyo area is that the main consumers of electricity are no longer predominantly manufacturing plants but offices and households, which makes it difficult to coordinate actions to save power.
Of fiscal 2006’s total domestic electricity demand of about 1.04 trillion kilowatt-hours, 60 percent was consumed by plants, department stores, offices and other large business entities, and 40 percent by households, small offices and other small-scale users.
Total annual demand has increased by 16 percent since 1996, when the figure was about 903.5 billion kilowatt-hours. While the increase in demand among business entities during that period was 11 percent, the figure for households was 22 percent.
The sharp increase in household demand for electricity is a result of increased air conditioner usage, with many households now fitted with two or three air conditioners.
The only measure TEPCO has held in reserve is the invocation of the power-cut option among smaller users with contracts stipulating the power-cut option. This measure could reduce demand by a further 1 million kilowatts.
According to the Central Research Institute of Electric Power Industry, if a condition of excess power demand is not addressed, the frequency and voltage of the electricity current falls, and this can result in computer glitches or the sudden stopping of elevators.
In the worst-case scenario, power outages can suddenly occur, and TEPCO has no way of predicting where such outages might take place.
Ikuo Kuribayashi, deputy director of the System Engineering Research Laboratory of the institute, said, “If the worst-case scenario of a serious power shortage occurs, TEPCO may implement a power cut rota.”
This measure cuts the power supply during designated hours in one area and then another. This can in effect force households to reduce electricity consumption. This measure has been used in the United States.
(Aug. 24, 2007)