Photo/Illutration A solar power plant in Fukuoka Prefecture (Asahi Shimbun file photo)

Power cuts triggered by surges in renewable energy sources like solar and wind power are increasingly common.

Electricity outages result when renewable power resources produce more energy than the grid can take. Effectively utilizing the growing capacity of renewable power generation so that it develops into a main power source in the future will require stepping up measures on both the supply and demand sides. That is the only way to avoid losses of potentially useful energy.

A survey by the Asahi Shimbun of leading electric utilities revealed that their operations to reduce the amount of electricity generated to maintain a balance between supply and demand had more than tripled last year compared to two years earlier.

Expansion of curtailment was particularly pronounced in western Japan, especially in areas served by Kyushu Electric Power Co., where solar power generation is abundant and more nuclear reactors have been restarted. However, this trend is now spreading to other regions as well.

Electricity generation and consumption must match to prevent frequency disturbances that can lead to large-scale power outages.

During times of high electricity production, such as sunny midday periods with increased solar power generation, the first steps power companies take are reducing output from thermal power plants and using the extra electricity for pumping water in pumped-storage hydroelectricity.

Electricity is also transmitted to regions served by other power companies. Only when there is still an excess after taking all these steps do electric utilities reduce solar and wind power outputs.

Given the fluctuations in renewable power generation due to weather conditions, this system is needed to a certain degree. However, from the perspective of effectively utilizing renewable power generators that do not emit carbon dioxide, more ingenious efforts should be made to reduce curtailment operations. Such efforts are indispensable for encouraging investment toward the expansion of renewable energy.

Especially necessary is the enhancement of mechanisms that encourage adjustments on the demand side.

If, during times of power surplus, operations of plant facilities that consume a lot of power like electric furnaces, can be quickly and flexibly increased, or if homes and businesses use heat pump water heaters, curtailment can be reduced. This requires the development of a more flexible tariff system that makes electricity cheaper depending on time zones, as well as investment in facilities for detailed online control.

Efforts to store surplus electricity, such as the introduction of storage batteries and hydrogen production facilities, are also crucial. Battery prices are falling, and installations are expanding worldwide.

On the supply side, in addition to reducing the minimum output of thermal power plants, it is necessary to strengthen the interconnection lines that allow for the mutual exchange of electricity between regions.

Among renewable energies, the expansion of wind power, which can complement solar power when weather conditions are right, should be accelerated.

The “priority dispatch rule,” a regulatory framework that gives certain types of electricity generation sources preferential access to the electricity grid over others during times of oversupply, prioritizes nuclear power along with hydropower and geothermal energy. In other words, the outputs from these high-priority power generation systems will be the last to be curtailed.

As a result, solar and wind power curtailment increases as nuclear power generation grows. Since existing nuclear plants are not suited for output adjustment due to safety concerns, this order of priority is inevitable in a sense. However, a system that imposes costs on the inflexible power sources should also be considered.

The most logical way of achieving decarbonization, an urgent and critical environmental challenge, is “making renewable energy the main power source.” No effort toward this goal should be spared.

--The Asahi Shimbun, Feb. 27

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