Solar Plant Designed to Minimize Damage to Roof (page 3)
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)
The connecting boxes that are set upright, instead of being laid down, also reflect considerations for ease of operation and maintenance (Fig. 8). As resistance to wind pressure was required because the boxes are standing, the metal fittings used to install the connecting boxes are noticeably large.
As this plant is Daiwa House Industry's first installation of an on-roof-type large-scale solar power plant and the project has an element of verification, a variety of instruments needed to operate the power generation system such as power supplies, sill cocks, solar radiation sensors, temperature sensors and remote monitoring cameras are installed and leveraged for maintenance (Fig. 9). Daiwa House Industry even redesigned some instruments, considering they were excessive, to make them simpler for future on-roof large-scale solar power generation systems.
As to the solar power generation system, the plant adopted Kyocera's solar panel and Toshiba Mitsubishi-Electric Industrial Systems Corp's (TMEIC) PV inverter. Kyocera's solar panel was adopted for its performance at the nearby "Hibikinada Solar Power Station" by Electric Power Development Co Ltd (J-Power) in consideration of the impact from salt damage owing to the plant's location by the sea. TMEIC's PV inverter was adopted because of the generally high praise it has received.
Roof preservation, heat shield effects
Solar power generation systems installed on the roof of a large structure have other benefits in addition to power generation. It is "the contribution to roof preservation and boosting the heat shield effect of the roof brought about by the solar panels that work as a roof cover," said Megumu Sonobe, manager of the Management Planning Department, Daiwa House Industry.
In terms of roof preservation, the panels can protect the roof without damaging it while slowing its aging. In fact, on one occasion, a radio-controlled helicopter fell and damaged the solar panels at this solar power plant. Had the panels not been mounted, the roof would have been seriously damaged. As for slowing its aging, the effects show in areas that are not directly affected by sunlight.
The heat shield effect of the roof contributes to, for example, reducing air-conditioning costs inside the building. Daiwa House Industry is verifying this effect with the 816kW capacity solar power generation system installed on the roof of Building No. 2 at its Okayama Plant. The temperatures of the roof surface and inside the building are compared to assess the effect of the panels. Such a benefit is likely to grow to an advantage regarding the future penetration of on-roof-type solar power generation systems.
Using Okayama Plant's solar power generation system, various solar panels and clasps are being compared and verified. As for solar panels, Korean LG Electronics Inc's single-crystal silicon type, Sharp Corp's and Suntech Power Japan Corp's polycrystalline silicon type and Solar Frontier K K's thin-film type were introduced with an output of about 207kW, 202kW, 205kW and 202kW, respectively. And about 100kW of panels of each manufacturer were set up facing south (and the other 100kW facing north) to measure the power generation efficiency and the amount of power generation.