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Japan's Largest Solar Plant Withstands Ash, Salt, Strong Wind (page 2)

Widespread effort to realize 70MW output, finish construction in 14 months

2013/12/01 19:56
Shinichi Kato, Nikkei BP CleanTech Institute
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Solar panels tilted at 20 degrees to realize 70MW

Some skeptics might wonder if the location near Sakurajima is suited for solar power generation, remembering the thick carpet of volcanic ash in Kagoshima City seen on the TV news, etc.

Kagoshima Nanatsujima Mega-Solar Power Plant is located to the southwest of Sakurajima. Volcanic ash from Sakurajima does not fall frequently over the area to the southwest side where the solar plant is located since it is blown by the wind to the north side. Even if volcanic ash did land on the solar panels on one day, it would be almost completely blown away by sea wind by the following day or be washed away should it rain.

Of course, measures have been taken to prevent the accumulation of a thick layer of volcanic ash and dust. Three 8mm-wide slits are added to both sides and the middle of the bottom of the solar panel frames (Fig. 3). Volcanic ash and dust can be washed off through these slits by rain. If a conventional frame were used, some of the volcanic ash and dust would be left at the bottom of the frame.

If volcanic ash was still piled up and the amount of power generation went below expectation for six consecutive days, all 290,000 solar panels will be cleaned with trucks, moving between the panels, loaded with high-pressure washers and power generators. If this happens, 200t of well water prepared in the power plant will be used for washing.

The solar panels were tilted at 20 degrees when installed on the mounting system. Based on the sun's culmination altitude in Kagoshima Prefecture, the panels should be tilted at 26.3 degrees to secure the maximum amount of annual power generation.

However, if tilted at this angle, the solar panels to realize an output of 70MW could not be set up at a distance from each other that is enough for each panel not to shade the neighboring panel in the morning and late afternoon when shadows lengthen as the sun comes up or goes down. Based on this, the solar panels were tilted at 20 degrees, an angle at which they could be laid out to realize 70MW and a greater amount of annual power generation could be secured.

Unique measures intended for solar power plants facing the sea were added to the mounting system, namely, materials and a structural design incorporating salt and wind resistance. The steel used in the mounting system is zinc-coated. In addition, the design reflected the results of wind-tunnel experiments using a 1/4-sized model. And it features resistance to winds of 60mps, which exceeds Kagoshima Prefecture's reference wind speed of 33.7m when designing structures.

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