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1.4MW Solar Plant in Toyama Directly Hit by Ferocious Winter Lightning (page 2)

Annual power sale affected by snow accumulation

2019/07/01 20:11
Shinichi Kato, Nikkei BP Intelligence Group, CleanTech Labo
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The way it snows in Hokuriku

The annual power generation amount was higher than anticipated in the years after the start of operation, and the amount remains steady, according to the company. However, the power generation amount per year fluctuates by up to roughly 10% depending on the snow accumulation situation (Fig. 3).

Fig. 3: Snow removal (source: NiX)

Roughly speaking, the power generation amount tends to drop in January and February due to snow accumulation, so a moderate estimate is drawn up in the business plan. However, the amount exceeds the estimated amount when snow accumulation is low during those two months.

On the other hand, snow accumulation in the months from December 2014 to January 2015, the first winter after the start of operation, exceeded the estimation and the power generation amount in January was lower than the amount estimated in the business plan by 38%. Snow accumulated by about 30 cm per night for three to four consecutive days in ten days. Snow piled up on the arrays (units for fixing solar panels on mounting systems) and nearly reached the top of the solar panels.

The height of the bottom of the solar panels is set high at 1.5m, but there was a risk that the snow would reach the panels after sliding down the panels and accumulating. About 20 employees pulled down the snow and removed it in front of the arrays.

Possibly struck by 'winter lightning' unique to Hokuriku region

Damage rarely seen to solar panels occurred in the winter from December 2016 to January 2017, the year before the region was hit by heavy snow. Some cover glasses were cracked and significantly warped (Fig. 4).

Fig. 4: Solar panels warped (source: NiX)

During this season, the remote monitoring system frequently warned of ground faults in the DC circuits. This occurred once Dec 6, 2016, three times on January 5 and 6, 2017 and 12 times on January 12 of the same year.

When the warnings are transmitted, an electrical chief engineer visits the site and checks the situation. The severely warped solar panels were discovered by the licensed electrical engineer during a patrol. Based on the phenomenon that occurred later and weather conditions on these days, it is believed that the mega solar power plant was directly hit by "winter lightning" Dec 5 or 6 of 2016. The area suffered from a number of "winter lightning" strikes on those two days.

Winter lightning is a phenomenon unique to Japan Sea side regions and is generated in winter along cold fronts. The electrical energy of winter lightning is stronger than the electrical energy of summer lightning by more than 100 times.

Two scenarios are anticipated for the phenomenon that occurred at the mega solar power plant of Nix. One of them is winter lightning, which caused warping of solar panels and a temperature increase in the outer circumference of the warped solar panels, causing a vapor explosion and damage to the cover glass of the panels. The other is the electromagnetic force generated by winter lightning, which applied excessive stress in the outer direction of solar panel aluminum frames, causing the cover glass to break.

In both cases, breakdown was caused by the impact of the damage, causing warping of panels due to stress applied later by the weight of the snow.