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Solar Plant on Former Eel Farm Avoids Floods But Suffers From Weeds (page 2)

Weeding implemented in line with local events, vehicle-type weed cutter utilized

2019/08/16 10:59
Shinichi Kato, Nikkei BP Intelligence Group, CleanTech Labo
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Mega-solar plant submerged 1st after water level rises

The Kurimamachiya Mega Solar Plant is situated along the watershed of rivers near the sea (Fig. 2). The site was previously used as a pond for eel farming (Related article: Riverside Solar Plant Absorbs Water of Flooded River).

Fig. 2: Mega-solar site sometimes becomes lower than river depending on tides and floods (source: Nikkei BP)

Located about 1km away from Ise Bay, the plant is adjacent to the junction of the Shitomo River and the Kenashi River at its south end, with the rivers running to the east and southwest, respectively. To the northwest the plant faces a ready-built housing complex. Sanko Real Estate started selling units in this housing complex in 1969 and has since maintained a close relationship with the residents.

Located near the sea, water levels around the plant shift with the tide. When the tide is high, the water level rises and water flows into the ditches built outside the levee and inside the housing complex.

Accordingly, Sanko Real Estate designed the site so water would flow into the mega-solar site first before the housing complex site floods as soon as the rivers rise to a certain level or higher and the amount of water increases to more than the ditches in the surrounding area can absorb.

The site has been reclaimed to gradually descend from the highest area adjacent to the housing complex in the opposite direction. At the same time, many areas in the plant site were built lower than the adjoining site on the side of the housing complex.

As a result, if the water level rises higher than expected, the mega-solar plant will be submerged before the housing complex. In other words, the power plant will play a role similar to a balancing reservoir. Moreover, water will pool in areas further away from the housing complex.

As for drainage measures inside the site, underdrainage, which is a measure to drain the stagnant water underground, was built in addition to a sand basin. The sand basin not only prevents sand from being discharged to outside by storing it, but also retains water. The underdrainage was set up underground connecting the sand basin and the ditches. The constructor buried pipes with holes in the ground and spread crushed stones all over the pipes. Water, after penetrating the ground, will enter the underdrainage through the holes and flow into the sand basin and the drainage ditches.

During the approximately three years and 10 months since the operation began, no solar panels and other power generation facilities have been submerged, proving the effect of the design.

When a high tide coincided with heavy rain, the roads inside the housing complex were apparently submerged from time to time. Even in such cases, however, only part of the mega-solar site's foundations seems to have submerged in the water near the south end, which is the lowest area in the site.