Solar Plant Designed to Minimize Damage to Roof (page 2)
Spreading across logistics center roof, securing ease of maintenance
Fig. 4: A total of six clasps holding a solar panel on both of its long sides. A solar panel was installed with three clasps on each side on the three tops of the folded-plate roof. (source: Nikkei BP)
In addition, given the service life of roof coating, it is sometimes necessary to repaint the waterproofing and other coatings every five to 10 years. The solar panels installed on the roof should not interfere with the recoating process.
In view of these circumstances, Daiwa House Industry arranged the distribution of panels so it is easy to confirm the state of the roof by sight and fixed panels without damaging the roof.
The logistics center's roof is metal and is called a folded-plate roof where V-shapes line up sideways; this is a type that is widely used at large-scale facilities. Daiwa House Industry installed the solar panels so that they would neither damage the top part of the folded-plate roof nor affect its coating while realizing a strength that would not let the solar panels be blown away by the wind.
For the clasps that would meet these goals, the products of Sakata Co Ltd and Nichiei Intec Co Ltd were deployed.
"The clasps use fewer bolts than other models and accordingly help constructors to install panels more easily with a smaller load," said Yoshiteru Adachi, New Energy Project leader, New Energy Division, Daiwa Energy. "As a result, construction errors would decrease, increasing the benefit of a shorter time required for installation. If it is easier to construct, the number of days to work on the roof will decrease. And that will lead to a cut in costs."
Panels fixed avoiding slits for drainage
The solar panels were set up by attaching clasps at the top of the folded-plate roof. A total of six clasps are used to fix each solar panel, with three pieces set on each long side of the panel (Fig. 4).
Each solar panel was mounted across the three tops of the folded-plate roof. And, basically, 28 panels were installed on three folds. As a circuit called a "string", which connects 14 solar panels as one unit on direct current, is formed, two strings are allotted to every three folds and connected with a connecting box. There are, however, some exceptions. This is because the panels are installed to avoid the exhaust ports and soft parts of the structure (Fig. 5).
When attaching the clasps, issues arose stemming from the adopted solar panel design. Kyocera Corp's solar panels have three slits for drainage on both sides and in the middle, and it turned out that the middle part of the panel could not be fixed with the clasps because of the slit. For this reason, Daiwa House Industry modified the panel positions at tops of the folded-plate roof so that the clasps could be used to hold a panel at positions slightly away from the panel center (Fig. 6).
Schemes to realize ease of maintenance, short construction time
Also, in an effort to cut the construction time on a roof as long as 290m, Daiwa House Industry conveyed the related materials by a trolley on a track set up on the roof. Such a method could never be applied without being familiar with every part of the roof including the load capacity.
In addition to this, there were various others schemes and considerations. First, you will recognize the solid-looking stairs and platforms on the roof (Fig. 7). They are designed for a number of people to easily go up and down or walk on, aimed at securing safety and ease of inspection and maintenance.
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