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Light-weight Panels Realize Japan's Largest On-roof Solar Plant

Mountable area expanded on roof of glass substrate plant

2013/12/28 19:15
Shinichi Kato, Nikkei BP CleanTech Institute
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Following the implementation of the feed-in tariff (FIT) scheme for reusable energy, a number of on-land-type mega solar (large-scale solar) power plants have been constructed one after another. And areas where they can be constructed relatively easily have been developed. As a result, it is expected to gradually become more difficult to cultivate suitable new areas.

Based on these circumstances, from now, the large-sized roofs of plants, warehouses and public facilities are likely to be focused upon as locations to install solar panels. As of today, the largest on-roof-type mega solar power plant in Japan is Asahi Glass Co Ltd's 5MW Kansai Plant Takasago Factory (Takasago City, Hyogo Prefecture).

Asahi Glass' Kansai Plant Takasago Factory is located in the Harima Coast Area in south-central Hyogo Prefecture, where heavy industry is thriving. In the 2000s, the plant supported the company's mainstay business as a core factory of large glass substrates for LCD panels. After installing solar panels with about 5MW output on this factory's roofs, Asahi Glass started selling electricity in March 2013.

Light-weight panels expand mountable area by 20%, output by 1MW

Regarding the power generation business, Asahi Glass said, "We are approaching the business because it's one of our duties as a material manufacturer. We are focusing on the business but do not give priority to the revenue from power sales." For instance, the company said, the factory is aimed at utilizing and verifying materials and technologies intended for Asahi Glass' proprietary solar panels and power generation systems.

The company chose the Takasago Factory's roofs because the largest area of roof could be secured there. The factory's overall site area is approximately 380,000m2. The solar panels were mounted on about 70,000m2 of some buildings' roofs in the factory. As the glass factory already receives power from the extra-high voltage transmission wire, it can easily have a grid connection even with an output of 2MW or larger.

The mega solar power plant has a notable feature: the weight of its solar panel is less than half the weight of other crystalline silicon solar panels generally used at mega solar power plants. Thanks to this, solar panels could be mounted on the roofs, on which panels could not have been previously mounted because of the roofs' insufficient load capacity (Fig. 1).

As a result, the area where solar panels can be mounted was increased by 20%, compared with the system consisting solely of the existing panels. Specifically, the area and output were increased approximately by 13,000m2 and 1MW, respectively. This is reportedly the first case in the world where light-weight panels with an output of about 1MW were installed on roofs.

For installing solar panels on roofs with an insufficient load capacity, two methods have been conventionally used. One is reinforcing the structure to improve the load capacity of the roof. This method, however, increases the installation cost. The other is a reduction in the number of panels to be installed to meet the load capacity. In this case, the power generation amount decreases due to the reduction in the number of installed solar panels.

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