Visit to Plant

No Solar Facilities Damaged in Flood After Typhoon

6 years of 'asphalted mega solar plant'

2019/03/04 18:11
Shinichi Kato, Nikkei BP Intelligence Group, CleanTech Labo
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The "Shoken Ishibe Solar Power Plant," a mega- (large-scale) solar power plant with an output of about 1.81MW in Konan City, Shiga Prefecture, Japan (See related article), and the "Shoken Kashiwabara Solar Power Plant" with an output of about 2.45MW in Maibara City, Shiga Prefecture, have experienced abnormal weather problems and large-scale maintenance over approximately six and five years, respectively, since their operation began.

According to Shoken Co Ltd (Otsu City), which is the power producer and a general contractor focusing on local civil engineering, the mega-solar plant in Konan City was flooded following nearby rivers and streams rising as "typhoon No. 18 of Heisei 25," which caused serious wide-area flooding, passed through Shiga Prefecture from September 15 to 16, 2013 (Fig. 1).

Fig. 1: Flooding in September 2013 (top) and same spot during normal times (bottom) at Shoken Ishibe Solar Power Plant (output about 1.81MW) (source: top Shoken, bottom Nikkei BP)

Although the Konan site was flooded, no power generation facilities were damaged. This was largely attributed to the power plant design. Set up at the lowest point at the mega-solar plant in Konan City are PV inverters and step-up transformers (cubicles). They were fixed on about 30cm-tall concrete foundations built on crushed stones (Fig. 2).

Fig. 2: Around PV inverters when site flooded (top) and during normal times (bottom) at Shoken Ishibe Solar Power Plant (output about 1.81MW) (source: top Shoken, bottom Nikkei BP)

While the flood water rose almost to the top of the foundations, it never rose above the foundations, so the PV inverters and step-up transformers remained safe. Solar panels and combiner boxes were fixed on about 50cm-tall concrete foundations built on the asphalted ground (Fig. 3). Despite the flooding, both solar panels and combiner boxes were neither inundated nor submerged as the water never rose above the concrete foundations.

Fig. 3: Arrays during flooding (top) and normal times (bottom right) at Shoken Ishibe Solar Power Plant (output about 1.81MW) (source: top/bottom left Shoken, bottom right Nikkei BP)

At the Konan site, cables between solar panels, combiner boxes and PV inverters were placed in elevated racks when they were set up. During the flooding, this design worked well. At many mega-solar plants in Japan, cables are buried underground or laid on the ground. The cables at Shoken's Konan site are laid on the 50cm-tall concrete foundations (Fig. 4).

Fig. 4: Racks during flooding at Shoken Ishibe Solar Power Plant (output about 1.81MW) (source: Shoken)

Cables were supported on the bottom side of the solar panels up to the combiner boxes and in the housing racks fixed on the concrete foundations at 50cm or higher from the ground between arrays (a unit of panels set up on a mounting system) up to the PV inverters. Thanks to this design, cables also avoided sinking in the water.