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Light-weight Panels Realize Japan's Largest On-roof Solar Plant (page 3)

Mountable area expanded on roof of glass substrate plant

2013/12/28 19:15
Shinichi Kato, Nikkei BP CleanTech Institute
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Installation time cut by half

There is another benefit of reducing the weight of a solar panel: lower installation cost. The panel is easy to set up because it is light, and the easy installation brings a reduction in the installation time.

Compared with the on-land type, work efficiency usually worsens when setting up solar panels on roofs because they are more difficult to walk on than on the ground. The lighter the panel is, the easier the workers can carry it and the more panels can be brought up at one time and kept on the roof. Furthermore, the load on the workers decreases thanks to the safety of installation work being enhanced by the panel's lightness and handiness.

Asahi Glass said it could cut the installation time almost by half when installing this light-weight model, compared with the time required to install the same number of existing solar panels. While a pair of workers carry and install the existing model one by one, three panels can be carried at one time with the light-weight model. Therefore, it cut the installation period by reducing the time to install solar panels.

When lifting the panels 200kg at a time onto the roof, the number of lifts was cut by half because 20 panels can be lifted at a time with the light-weight model, whereas only 10 panels can be lifted at a time with the existing model.

However, Asahi Glass said the benefit of time reduction has not yet been fully enjoyed because the time required for connection is longer compared with the existing model due to the different method to connect panels with the wiring.

To ensure safety, safety ropes were set on the roof first, and, then, a safety net was set up around the roof before starting to install the panels on the roof. The roof was a metal building material called folded-plate roof, in which V-shapes run crossways. The material is widely used in plants and other large facilities. The solar panels were set up using clasps and bolts strong enough to keep the panels from being blown away by the wind without making a hole in the folded-plate roof (Fig. 3).

The solar panels were tilted at about 2° against the horizon when installed. Asahi Glass said this is the angle at which dust and other particles accumulated on the panel can be easily washed off by rainwater. The panels were tilted at 2° by arranging the clasps, regardless of the roof angle on which the panel is installed.

As the connecting boxes are also placed on the roof, a stainless chassis was adopted as a measure against salt damage and strong wind.

Upon consideration of workers' safety, winter and summer were avoided when installing the panels because strong wind and rain occurs on many days in winter while it is hot on the roof in summer. For these reasons, winter and summer are both dangerous for the installation workers.

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