Visit to Plant

Double-sided Solar Panels Turn Snow Into Advantage

Power generation efficiency improves even in winter

2014/02/09 15:24
Kenji Kaneko, Nikkei BP CleanTech Institute
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Asahikawa City, Hokkaido, is known as one of the coldest cities in Japan. The average depth of snow is about 70cm, which is less than in other heavy snowfall areas, such as the Joetsu region, but the fallen snow freezes and hardly melts in midwinter because the temperature often goes below freezing even in the daytime.

In July 2012, when the feed-in tariff (FIT) program was implemented, leading companies visited Asahikawa in search of a place to build a mega (large-scale) solar power plant. However, no leading company has ever constructed a mega solar power plant there owing to the risk regarding the sustainability of the business.

Snow slips off solar panels

On November 29, 2013, "Asahikawa Hokuto Solar Power Plant," with 1.25MW output, started operation in the region that seemed ill-suited for a mega solar power plant (Fig. 1). Local electric facility company Nishiyama Sakata Denki Co Ltd (Asahikawa City, Hokkaido) has been engaged in the plant's design, construction, maintenance and power generation business. Ahead of Asahikawa Hokuto Solar Power Plant, Nishiyama Sakata Denki also launched "Asahikawa Kuranuma Solar Power Plant" with 250kW output Sept 30, 2013 (Fig. 2). The company runs these two solar power plants in Asahikawa City.

In late January 2014, I visited these two plants to gather information. The weather was fine that day, but in the city there was about 60cm of snow that had fallen three days earlier. Asahikawa Kuranuma Solar Power Plant with 250kW output is a 20-minute drive from the downtown area. Despite the snowy landscape in the surrounding area, almost no snow was found on the solar panels (Fig. 3).

"As soon as the solar panels start generating power under the sun, the snow on the panels naturally starts slipping off, melting as the temperature of the panel surface rises," said Satoshi Nishiyama, director and chief of the Corporate Planning Department, Nishiyama Sakata Denki.

Snow should be removed before it consolidates

"When the snow slips off the panels, the fallen snow forms banks under the panels," Nishiyama said. "And the snow only slips off the panels until the snow banks reach the height of the solar panels. At Asahikawa Kuranuma Solar Power Plant, snow easily fell off the panels because the snow banks under the panels had been removed by heavy machinery. At Asahikawa Hokuto Solar Power Plant, on the other hand, fresh snow fell onto the snow banks before they were removed, and, consequently, some snow remained on the panels without slipping off."

He regretted that the company had delayed snow removal.

I also visited Asahikawa Hokuto Solar Power Plant. The snow banks under the panels had adhered to the snow on the panels, and the snow remained on a large portion of the panels (Fig. 4). The plant is in a suburb a 10-minute drive from the downtown area of Asahikawa City. Using the grounds of a closed high school, the entire mega solar power plant can be looked down upon from the parapet of a nearby bridge, which is positioned a little higher than the surrounding area (Fig. 5). It is an ideal spot for a mega solar power plant close to citizens.

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