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Wakkanai Mega Solar Plant Pioneers Local Use of Solar Electricity (1)

Power supplied to adjacent facilities using own transmission lines during blackout

2020/03/17 15:55
Kenji Kaneko, Nikkei BP Intelligence Group, CleanTech Labo
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The Ministry of Economy, Trade and Industry (METI) reviewed the teed-in fariff (FIT) scheme and decided to establish a new "regional power supply" category. METI will continue to support plants of this category under the FIT scheme upon the condition that they can generate power independently and supply power to local regions in the event of power failure in commercial grids caused by disasters, etc.

The requirement set for low-voltage solar power plants for business use is "30% or more self-consumption rate and independent operation during power failure," which will be applied to power plants certified in FY2020 and later. As for high-voltage and extra-high-voltage solar power plants, discussions on the "requirements for regional power supply" will be started soon. In this feature article, the sites evaluated as examples of "regional power supply" at meetings of experts held by METI are introduced.

Supplies power during blackout

In the Hokkaido Eastern Iburi Earthquake in the early morning of September 6, 2018, the Tomato-Atsuma Thermal Power Plant of Hokkaido Electric Power Co Ltd (Hokuden), which was near the seismic center, was damaged, and two of the three generators stopped operation. The damage to the plant led to power failure throughout Hokkaido, resulting in a "blackout" where all power grids stopped operation for two days.

Following the failure, mega (large-scale) solar power plants and wind power plants that were in operation in Hokkaido were disconnected from power grids and stopped operation.

Renewable energy facilities, which rapidly increased following the introduction of the FIT scheme, are basically designed to be connected to transmission lines for sale of all the power. Therefore, it is also impossible for "dispersed power sources" in local regions to supply power to nearby regions when commercial grids stop operation. General inverters for connection to high-voltage grids cannot transmit AC current independently because they are controlled according to the frequency of grids for transmission of power.

When the blackout due to the earthquake affected various regions in Hokkaido, people complained saying, "We invited many mega solar power plants and wind power plants to the region and cooperated in constructing the plants. Why can't we use electricity at all when a power failure occurs?"

Under such situation, the "Wakkanai Mega Solar Power Plant," which is operated in Wakkanai City and features an output of about 5MW, continued to supply power to "Wakkanai City Onuma Ballpark" and "Hokkaido Soya Fureai Park" adjacent to the plant during the blackout. The power plant was also disconnected from the grid of Hokuden at 3:08am on September 6 after the earthquake, but the power supply to the two facilities continued even after the disconnection (Fig. 1).

Fig. 1: Full view of the "Wakkanai Mega Solar Power Plant" (source: Wakkanai City)

The records of the plant were presented at a committee meeting held by METI for verification of the course from the occurrence of the earthquake to the blackout, indicating the great potential for regional use of mega solar power plants.