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Solar Plant in Toyama Endures Heavy Snow Without Removing Snow (page 4)

2019/07/31 12:00
Shinichi Kato, Nikkei BP Intelligence Group, CleanTech Labo
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Solar panels manufactured by NextEnergy & Resources Co Ltd (Komagane, Nagano Prefecture) were adopted. A total of 20,592 polycrystalline silicon-type panels (255W/unit) were arrayed.

As for PV inverters, a DC 1,000V-supported product manufactured by Toshiba Mitsubishi-Electric Industrial Systems Corp (TMEIC) was adopted. Six units with a rated capacity of 750kW each were introduced (Fig. 7).

Fig. 7: Composed of six PV inverters (source: Nikkei BP)

Annual power generation is expected to total about 4,800,000kWh, which is equivalent to the consumption of about 1,300 general households. Generated power is sold at 32 yen/kWh (excluding tax) under the feed-in tariff (FIT) scheme to Hokuriku Electric Power Co Inc.

The plant has been hit by heavier-than-expected snow cover since it began operation. In the winter from 2017 to 2018, heavy snow dubbed "Gosetsu 2018" continued across the coast along the Sea of Japan. In this heavy snow, many solar power plants suffered damage such as collapsed mounting systems. Amid such circumstances, there was no damage at the mega-solar plant in Toyama Shinko. Toyama Prefecture considers the design that primarily focused on the snow cover load proved effective.

However, accumulated snow on the ground grew high enough to reach the lowest part of the solar panels following heavier-than-expected snowfalls that continued all night twice in a row. At that time, Toyama Prefectural Government Enterprise Bureau continued to monitor the situation without removing the snow. This was because the prefecture wanted to know what would happen if the situation was left as it was. As a result, while the amount of power generation was affected, neither arrays nor solar panels were damaged.

The enterprise bureau was worried that some panels in the lower rows would be broken by downward pulling strength because of the increased load when snow slips off the panels. However, no panels broke.

Partly because the sea is near, the amount of snow cover is usually less compared with other areas in Toyama Prefecture. The plant has also experienced operations stopping because of power outage in the power transmission cables supposedly due to winter lightning, which is unique to the Hokuriku region. But, according to Toyama Prefecture, operation did not stop so many times as to have a serious impact on the power selling business.

Winter lightning is unique to the Sea of Japan side and strikes along a cold front during winter. Compared with summer lightning, its electric energy is sometimes more than 100 times higher. The Ministry of Economy, Trade and Industry requires wind farms in the corresponding areas to take special measures against winter lightning.

Regarding the damage believed to have been caused by winter lightning, the cover glass of solar panels was broken and significantly warped at a mega-solar plant in Yatsuomachi, Toyama City (See related article).

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