Japan's Largest Battery-equipped Solar Plant Almost Completed in Hokkaido (page 3)
102MW of panels, 52MW storage battery set up on former ranch
'Yard for temporary assembly' to build units in advance
Despite the large scale exceeding output of 100MW, panels were set up in accordance with the terrain without large-scale land reclamation. As the ground in the site was almost flat, the constructor could easily boost the construction efficiency by designing and setting up the panels in the same array (unit of panel installation) composition pattern.
Each array basically consists of nine panels sideways in three rows (9 x 3 panels), tilted by 30° and set up 1.3m from the ground.
The constructor divided the mounting systems for these arrays into three units and consecutively assembled them in the "yard for temporary assembly" first. The assembled mounting systems were lifted by a crane, loaded onto trucks, carried to the designated block in the site and lifted by the crane again before installation (Fig. 6, 7 & 8).
Such a "temporary assembly method" is unusual in mega-solar construction. In the cases of a large-scale solar power plant connected with an extra-high-voltage power grid, it is generally important to prepare multiple array structures and adjust them at the site of installation, depending on the angle of the ground to set them up and the shape of each construction block.
In that respect, the 11,312 mounting systems were set up in no more than one pattern because this overall construction site was flat and almost square. As a result, it was reportedly efficient to consecutively assemble the units in advance, carry them to the designated construction block, install them and finally adjust them.
Soil improvement using shells of local specialty scallops
As the project site is peatland near the coast, however, it was not easy to construct the foundations. To supplement the soil bearing capacity, the plant adopted a method of driving pile foundations 4 to 6m into the ground and solidifying the surrounding area with concrete. For this purpose, the constructor created a jig to keep the pile in the middle of the hole, which was dug in advance, and made it possible to fix eight pile foundations at one time and efficiently deposit the concrete (Fig. 9).
In addition, the plant uses the scallops cultivated in Uchiura Bay (Volcano Bay) in front of Yakumocho as a soil conditioner by crushing their shells and scattering them on some parts of the ground. Calcium carbonate in the shells neutralizes the acid peatland and dries the soil at the same time (Fig. 10).
Although Yakumocho is a relatively warm region in Hokkaido, the deepest snow cover reaches about 80cm on average in one winter. In light of that, panels were tilted by 30° so the snow accumulated on the panels would easily fall off and the power generation loss would be minimized.
Even though banks of snow would be formed in front of the arrays, the snow banks are not likely to reach the arrays without snow removal during the winter if the snow cover is like that in an average year thanks to the lowest part of the panels being 1.3m above the ground (Fig. 11).