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Mega-solar Power Plant Plagued by Vines (page 3)

Picket-based panel installation changed to foundation-based method

2014/04/06 12:22
Shinichi Kato, Nikkei BP CleanTech Institute
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When solar panels are tilted at 15°, on the other hand, the shadow's impact would decrease, and more panels can be set up. To maximize the amount of power generation in a limited size of area, it is generally considered more beneficial to set up more panels by reducing the installation angle.

Both "overload" and the method of setting up more panels by narrowing the installation angle cause the initial investment to grow. However, at the current stage where a relatively high purchase price is applied while the panel price has been decreasing, a power producer can boost the internal rate of return (IRR) by pumping up the amount of power generation by installing more solar panels. This is one of the reasons why overload and a smaller installation angle were adopted at Hitachiota Solar Power Plant and many other mega-solar power plants across Japan.

China's Suntech Power Co Ltd's solar panels and Toshiba Mitsubishi-Electric Industrial Systems Corp's (TMEIC) PV inverter were installed. Nippon Comsys said it chose Suntech Power's solar panel based on performance and pricing benefits while it selected TMEIC's PV inverter considering its performance and reliability in view of the use for the next 20 years. The employment of a proprietary PV inverter temperature control system and the burial of connecting cables (Fig. 3) are also rarely seen at other mega-solar power plants.

Different methods were used to hold the mounting system at A site and B site. At B site, which was constructed first, mounting systems are supported by pickets without creating foundations (Fig. 4). This was changed to a method that holds the mounting system with concrete foundations at A site, which was built later.

In general, the total construction cost can be lowered with the picket-based method, which requires no land leveling and foundation work, compared with the method that uses concrete foundations. However, the picket-based method is not strong enough when the ground is soft, and it requires special heavy machinery for construction when the ground is too hard.

One of the challenges the picket-based method faces also became clear at B site. The picket-hammering work took a long time due to part of the ground containing rock. As a result, for A site, it was changed to the method that uses concrete foundations. To minimize the cost increase, Nippon Comsys filled the inside of the U-shaped concrete ditch, which was procured for a drain channel set along the plant's perimeter, and used it as the foundation (Fig. 5).

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