Visit to Plant

21MW Solar Plant to Be Built on Land Cleared by Large Dump Trucks (page 2)

Foundations changed in consideration of rocky ground, slopes

2017/08/17 17:06
Shinichi Kato, Nikkei BP Intelligence Group, CleanTech Institute
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More-than-expected amount of earth

The mega-solar site slopes down the mountains to the north (Fig. 2). The ground is very rocky underneath in many areas, so the land is being reclaimed by crushing the rocks. Some other site areas, on the other hand, were located in valleys, where the land is reclaimed by piling earth on top.

Fig. 2: The rendering of the power plant. A total of 75,144 solar panels will be arrayed across northern slopes in the mountains. (source: Saga Ouchi Solar)

As large-scale land reclamation was required, Kyudenko considered the method in which solar panels are arrayed in accordance with the existing uneven terrain, such as former golf courses and hills, to be unsuitable. The company decided to develop slopes that descend at a certain degree to the north and array panels there.

Kyudenko planned to not discharge surplus earth outside the site, making the amounts of filling and cut earth generated from land reclamation equal. Cut earth will also be used to adjust the angle of slopes. The amount of earth to be moved in such land reclamation will reportedly total about 100,000m3.

In late July, when I visited the site under construction for the interview, the land reclamation was in its final phase (Fig. 3).

Fig. 3: Large-scale land reclamation using large dump trucks like those seen at mines. The scale of the reclamation can be estimated from the bedrock and rocks, and the almost completed slopes, etc. (source: Nikkei BP)

Large dump trucks like those seen at large-scale open-cut mines, bedrock cliffs, mountains of crushed rocks and the almost completed sloping terrain showed the scale of land reclamation.

In fact, after construction started, the amount of earth produced for land reclamation was more than expected. In order to completely use the earth, Kyudenko had to repeatedly adjust the overall slope angle, which resulted in an extended construction period. The company was originally supposed to have finished positioning the solar panels by then.

Fig. 4: Foundations and mounting systems are rapidly built, and solar panels are set up in areas where land reclamation is completed. Kyudenko is striving to catch up with the delay in reclamation by increasing the number of workers from the plan. (source: Nikkei BP)

According to Kyudenko, the amount of earth produced increased because of underground rocks. The amount of earth varies depending on the state of the rocks to be dug out. This time, the amount of earth produced was more than the initial plan. It also increased partly because of a slight change in the construction plan.

To completely use the earth dug out, which was more than expected, Kyudenko undertook more land reclamation work, lowering the initially planned angle of about 10.8% to 9.05% by filling in more earth, for example. Reclamation work that had been extended to the rainy season further delayed the construction period. When it rains, the ground is softened and stops reclamation work for about two days as a result.

Kyudenko is making up for the delay by allotting more workers than in the initial plan after building the foundations. The company described such agile adjustments as a strength of a construction company participating in a solar project. Kyudenko is building foundations and assembling mounting systems to set up panels from areas where land reclamation has finished (Fig. 4).