Solar Plant Exploits City Policy on Landfill

Integrated foundation resolves construction restrictions

2014/03/18 21:03
Shinichi Kato, Nikkei BP CleanTech Institute

"Hibiki Solar Power" (Fig. 1), a mega (large-scale) solar power plant with an output of 1.990MW, was constructed by Kitakyushu City's third-sector organization Hibikinada Development Co Ltd. The construction site is reclaimed land in which industrial waste landfilling had been completed.

The Hibikinada area is a landfill site facing the Sea of Japan, where plants, operations and waste disposal facilities of Nippon Steel & Sumitomo Metal Corp, Asahi Glass Co Ltd, Nippon Coke & Engineering Co Ltd and Electric Power Development Co Ltd, as well as Kitakyushu Eco Town's verification test facility, are located. Making the most of the vast land available, the area has recently been growing into a complex of mega-solar power plants and wind power plants (Fig. 2).

As for the waste disposal facilities in such areas, there are restrictions with respect to building construction and people's entry into the facilities during the purification period after the landfill is completed. The construction of the mega-solar plant is one of the methods to make efficient use of it.

Meanwhile, diverse environments such as wetland, freshwater ponds and grassland have been created because of the rough terrain formed by the wind and rain. And some places, where people have almost never entered, are now inhabited by various creatures including birds, animals and insects.

"Hibikinada Biotope" run by Kitakyushu City is one such place. More than 200 kinds of birds and nearly 300 kinds of plants have been confirmed, including rare species such as Circus spilonotus (Eastern march harrier), which the Ministry of the Environment has designated an endangered species (Fig. 3).

This mega-solar power plant faces Hibikinada Biotope across the sea. It has only been about three years since the completion of the landfill. When it was constructed, the fill surface had merely been bulldozed.

Construction in compliance with Kitakyushu City's plans

Hibikinada Development is a company established with the aim of securing industrial waste disposal facilities, etc for businesses based in Hibikinada and Kitakyushu City. And it has run a waste disposal facility in three blocks in the Hibikinada-Nishi area.

Hibikinada Development is financed by Kitakyushu City, Fukuoka Prefecture, Nippon Steel & Sumitomo Metal, Asahi Glass, Mitsubishi Chemical Corp, Electric Power Development, Nippon Coke & Engineering, Idemitsu Kosan Co Ltd, Nissan Motor Co Ltd, Krosaki Harima Corp, Mizuho Bank Ltd and the Bank of Fukuoka.

In Hibikinada Development's waste disposal facility, the shareholder companies' waste and steel materials, in particular, are buried. The facility's Block No. 1 (approx 536,000m2), where landfill was completed first, is now being sold in lots for uses such as logistics centers. The on-roof-type 2MW output mega-solar power plant (See related article) at Hibiki International Logistics Center, which we introduced in the "Visit to Plant" series, is located in Block No. 1 of this waste disposal facility.

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Hibiki Solar Power is situated in Block No. 2 (approx 369,000m2) of the facility, which was filled next (Fig. 4). Japan Asia Group's mega-solar power plant with about 2MW output is in the adjoining site across a fence.

Landfill was completed in the facility's Block No. 2 in 2011. Following Kitakyushu City's plan, Hibiki Solar Power was constructed as an effective use of the land being purified.

"Large-scale solar power plants have become a business that can avoid relatively major risks and expect revenue returns following the implementation of the feed-in tariff (FIT) program," said Mitsuo Nakatomi, president of Hibiki Development. "Moreover, the plant is in line with Kitakyushu City's policies."

Acquiring expertise from neighboring preceding mega-solar power plants

Kitakyushu City launched "Kitakyushu City Photovoltaic Power Generation Promotional Council" in January 2012 to offer measures including loan assistance by financial institutions toward the introduction of a solar power generation system. Hibikinada Development participated in this council. It procured financing for the construction costs of about ¥600 million (approx US$5.92 million) based on the council's assistance.

Executive Director Tsuyoshi Hashiguchi, Development & Planning Department of Hibikinada Development, said, "(In regard to the companies to be involved with the mega-solar power plant construction), we selected the companies that have business bases in Kitakyushu City. And we selected related instruments and components made in Japan (while considering their qualities and prices)."

Kyudenko Corp provided the EPC (engineering, procurement and construction) service, while Mitsubishi Electric Corp, Toshiba Mitsubishi-Electric Industrial Systems Corp (TMEIC) and Kokura Cement Co Ltd provided solar panels, PV inverters and mounting systems, respectively.

The mega-solar power plant operators said they could enjoy the local benefits of Hibikinada during construction. They could acquire expertise concerning the installation of a solar power generation system in Hibikinada from the Daiwa House Group and J-Power, which had constructed mega-solar power plants before the Hibikinada Development.

The expertise extended to a broad range of subjects including efforts to steadily secure a large amount of power generation, the amount of power generation among different manufacturers' panels and insurance to be purchased. As a result of reflecting on the experience offered, Hibiki Solar Power did not, for example, take out earthquake insurance.

Mounting system integrated with foundations

This mega-solar power plant has unique features that could only be found at waste disposal facilities. For example, the land is built over the waste buried in the landfill, and the land is purified by letting rain penetrate.

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Given these circumstances, concrete foundations cannot be built on the ground as they are in general large-scale solar power plants. Accordingly, the plant adopted a method in which a concrete piece that integrates the foundation part and the mounting system is placed on the ground.

Deployed was Kokura Cement's "Solar Keeper." Excluding the clasps to attach the solar panels, every other part is made of concrete (Fig. 5) so the required resistance can be secured by its own weight even without building up the foundations.

This system features more benefits than the weight that secures the resistance required for solar panel installation. First, the concrete model's durability is superior to that of general metal models. Given the location near the sea, its durability was also a key factor to be focused on not only against wind pressure but also against salt damage.

Weeds do not grow under the solar panels where the ground is covered by concrete (Fig. 6). This effect can also cut the cost for weeding.

While the PV inverters' total capacity is 1.990MW, 8,008 solar panels for an output of 2.002MW were installed. The installation angle of the panels is 20°. As the angle makes the shadow of the adjoining panels to the south shorter, the plant could array more solar panels than had first been expected.

Space for service vehicles to operate has been set out in a grid inside the mega-solar power plant. This space is needed not only for operation and maintenance of the power plant but also for soil purification. An adjustment ditch was also established for drainage (Fig. 7).

Along with the concrete foundations that cover the ground under the solar panels, weed control sheets are used between the rows of solar panels as another measure against weeds.