German-style Solar Plant Debuts in Kumamoto
Ozu Town, Kumamoto Prefecture, is located in the middle of Mt. Aso and Kumamoto City and has prospered as a post-station town since the Edo period. After driving for about 10 minutes from JR Higo-Ozu Station on a main road through the downtown area, you will enter a narrow street and find vegetable farms and woods spreading ahead.
This is the rural area where the "Ozu Solar Power Plant" mega-solar (large-scale solar) power plant with an output of approximately 1.1MW is situated (Fig. 1). Shrubs grow around the fence surrounding the blue solar panels, and magnificent Mt. Aso can be seen beyond the panels (Fig. 2).
"It was like a jungle when we first visited here during our search for a candidate site for a mega-solar power plant," said Takayuki Kasama, Kyushu area manager of Shizen Energy Inc (Bunkyo-ku, Tokyo). The approximate 21,750m2 of land under the power plant was formerly a pig farming facility. It had not been used for about 30 years and no longer had a clear border because the plants and trees had grown so much.
Headed on site by foreign engineers
Shizen Energy is a venture company engaged in the development and planning of plants based on reusable energy such as solar and wind. And it has developed reusable energy power plants on its own with output as much as 150MW, and 250MW in joint projects since its establishment in June 2011. Manager Kasama, who is responsible for the Kyushu area, was introduced to the land in Ozu Town by his acquaintances, repeatedly visited the five landowners to explain the framework of the mega-solar power business and saw the project through to the end.
"The project enabled the landowners to generate rent from the land that was not being used," Manager Kasama said. "I gained understanding from them all by giving them sincere explanations."
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In fact, no one wanted to use the land, which would require large-scale development for use as a housing area because of the concrete foundations left from the former pig farming facility.
As the landowners agreed to the project, major local companies to finance the project and run the power selling business were also selected. The next issue was how to install a highly reliable solar power generation system at a low cost on the ground left with the old concrete foundations.
juwi Shizen Energy Inc (Bunkyo-ku, Tokyo), which provided the EPC (engineering, procurement and construction) service, tackled this challenge. juwi Shizen Energy is a joint venture formed in January 2013 by Shizen Energy and the world's leading EPC service company juwi AG of Germany. Manager Kasama also serves as a project manager at juwi Shizen Energy and controlled the EPC of Ozu Solar Power Plant.
"As for each practical task regarding engineering, procurement and construction, three foreign engineers who were dispatched from juwi and stayed in Japan took the initiative, leveraging their knowledge about mega-solar power plant construction accumulated overseas," he said.
Quiet TMEIC PV inverters employed
juwi boasts the world's largest business in the market of EPC services for reusable energy power plants, having been engaged in about 1,500 projects or 1,250MW-equivalent solar power plants across the world. Its employees number approximately 1,800, and its sales reached roughly 1 billion euro (¥100 billion) in 2012.
"juwi assesses facility equipment in its proprietary duration tests before use and only procures products from specific manufacturers," Manager Kasama said. "Moreover, it even checks their quality management system, regularly inspecting the manufacturers' plants."
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For example, juwi is said to have limited its solar panel suppliers to six firms. Solar panels manufactured by Canadian Solar Inc, one of the six firms, were used at Ozu Solar Power Plant. Also, PV inverters of Toshiba Mitsubishi-Electric Industrial Systems Corp (TMEIC), which is among the manufacturers specified by juwi, were used (Fig. 3).
"Although products of SMA Solar Technology AG of Germany are often chosen overseas, we chose TMEIC's product this time," Manager Kasama said. "Both manufacturers' PV inverters are almost equally excellent in efficiency and reliability. But we preferred TMEIC's PV inverter to SMA's. TMEIC's product is housed in a building whereas SMA's is not. Therefore, there is less risk of noise that would trouble neighboring residents."
On the other hand, the plant employed an imported wiring facility and mounting system specified by juwi (Fig. 4). The mounting system is a product of Schletter GmbH of Germany (Fig. 5). Schletter is the world's leading manufacturer of mounting systems for solar power generation, and its products are said to have been deployed as much as about 10GW thus far, primarily in Europe and the US.
Its products feature a construction method that involves heavy machinery digging a hole in the ground and driving a stake into that hole. Many mounting systems made in Japan are supported by stakes driven into the ground at two spots on the rear and front sides of panels tilted on the mounting system. Schletter's products can be set up in a short period because they use fewer stakes; holding the panels on both sides with only one stake provides sufficient strength.
It reportedly only took just under a week to set up the mounting systems at Ozu Solar Power Plant. However, special heavy machinery is required to drive the stakes for Schletter's mounting systems, and there are currently only five such machinery units in Japan.
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What became a challenge when setting up the mounting systems were the concrete foundations left from the former pigsties. Should they be removed in a large-scale project, initial investment would increase too much to maintain revenues from the solar power business. Based on these circumstances, the plant decided to leave the concrete foundations untouched and minimize the impact on driving the stakes by arranging the disposition of the mounting systems (Fig. 6).
Water control to prevent "nuisance facility"
Along with the selection of facility equipment, juwi Shizen Energy has focused on "power plants that harmonize with the local community" throughout its mega-solar power plant constructions overseas. The company provided presentation meetings jointly with the neighborhood association after signing a location agreement with Kumamoto Prefecture and Ozu Town.
"One of the factors that make mega-solar power plants 'nuisance facilities' overseas is the water issue," Manager Kasama said. "Given their poor water retaining ability, mega-solar power plants can easily attract complaints as soon as rainwater runs in a specific direction."
Ozu Solar Power Plant, which looked "like a jungle in the beginning," was constructed by cutting down the plants and trees growing there. This made the local residents concerned about the water discharge issue caused by weakened water retaining ability. And some raised water-related questions at the joint presentation meetings with the neighborhood association.
In Japan, there is no obligation to set up a water discharging facility at solar power plants because the installation of a solar power generation system does not correspond to a "development action." Accordingly, most mega-solar power plants in Japan only establish a simple ditch and consider further action in accordance with any water accumulation and other factors after the operation has started.
On the other hand, Ozu Solar Power Plant asked Japanese civil engineering experts who know about Japanese ground formations to calculate the area’s maximum amount of water retention and water penetration ratio, in addition to juwi's findings, and constructed water passages using a U-shaped gutter. The civil engineers also buried boards to block groundwater streams and dug holes to move the water running out from the solar power plant in various directions.
"For a mega-solar power plant run by low-profile venture companies and foreign enterprises to be accepted by the local community and then take root, it is necessary to pay more consideration to the local community compared with the domestic leading companies," said Manager Kasama, standing in front of the mega-solar power plant, which has started operating smoothly.