Photo/IllutrationThe Asahi Shimbun

  • Photo/Illustraion

Usage rates of core electric power transmission lines operated by 10 major utilities are only 19.4 percent on average of capacity, contradicting a claim by these companies, according to a newly conducted analysis.

The remaining free capacity can be used to transmit electricity generated by renewable energies such as wind power or solar power.

However, major electric power companies are refusing to allow the use of the free capacity for transmission of renewable energies, saying that there is no available capacity in many of those lines.

The study was conducted by Yoh Yasuda, a specially appointed professor at Kyoto University’s economics course on renewable energies. It marked the first time in Japan that usage of the core transmission lines was surveyed on a nationwide scale.

“The usage rates of transmission lines with ‘zero free capacity’ should be higher," Yasuda said. "In reality, however, they have more free capacity in some cases. It is incomprehensible. Why do utilities say that their free capacity is at zero? Why do they restrict connection of the equipment for renewable energies by citing the zero free capacities as a reason? They are required to make reasonable and highly transparent explanations to those questions.”

The results of the analysis are scheduled to be announced in a symposium in Tokyo on Jan. 29.

Yasuda surveyed the 10 utilities’ 399 high-voltage core electric power lines, such as 500,000 volts or 275,000 volts, based on data released by the Organization for Cross-regional Coordination of Transmission Operators (OCCTO).

The data covered the period from September 2016 to August 2017.

The usage rate is the ratio of capacities of electricity that actually flowed in the lines to the maximum capacities of electricity that can flow in a year.

According to the analysis of the data, the usage rate of Tokyo Electric Power Co. (TEPCO) was the highest at 27.0 percent while that of Tohoku Electric Power Co. was the lowest at 12.0 percent.

The so-called “crowded transmission lines,” meaning that the usage rate temporarily exceeded 100 percent, occurred at least once in 60 lines. Of these, 22 lines were those of TEPCO.

Meanwhile, 139 of the 399 lines were categorized as “free capacity is zero.” However, their average usage rate was only 23.0 percent, which was almost the same as the 19.4 percent of the 399 lines.

According to the major utilities, zero free capacity is based on the premise that all existing power plants are running at their full capacities, including idled nuclear power plants and aged thermal power plants.

Therefore, the actual flow of electricity through the transmission lines was much smaller.

In a news conference held in November 2017, Satoru Katsuno, chairman of the Federation of Electric Power Companies of Japan, was asked about the circumstances that despite transmission lines having free capacity, equipment to transmit renewable energies could not be connected to those lines.

At that time, he said, “We are putting priority on nuclear power as a baseload power source.”

An official of a major utility also explained, “Free capacity cannot be measured based only on electricity that actually flowed in transmission lines.”

In Europe and the United States, however, transmission lines are used based on the capacity of electricity that actually flows through the lines. As a result, renewable energies have been introduced in large quantities.

Therefore, the economy ministry has begun to consider greater utilization of the free capacity.

The ratio of transmission lines whose free capacity is zero is high for utilities in eastern Japan, such as Tohoku Electric Power, Chubu Electric Power Co., Hokkaido Electric Power Co. and TEPCO.

On the other hand, the corresponding ratios for utilities in western Japan are low.

For utilities such as Tohoku Electric Power and Hokkaido Electric Power, the usage rates of transmission lines with zero free capacities were lower than those of all the transmission lines under their jurisdictions.

(This article was written by Toru Ishii, a senior staff writer, and Yu Kotsubo.)