Visit to Plant

Coal Mining Area Shaped Into Solar Town

Output lowered due to restriction by 'bank reverse power flow'

2013/11/25 13:47
Kenji Kaneko, Nikkei BP CleanTech Institute
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Koyagimachi, Nagasaki City, is situated in the mountains facing a cove about 10km from central Nagasaki City. Since being connected in 2011 by a bridge with Iojima Island, which has spa facilities and bathing beaches, the town has become more bustling. Shortly after driving into Koyagimachi on the way from central Nagasaki City to Iojima, solar panels start coming into view just beside the road, with the sea behind.

This is the "SoftBank Nagasaki Koyagi Solar Park" with 1.75MW output and being run by SB Energy Corp (Minato Ward, Tokyo). The hill on the opposite side of the road is a residential area, and you can overlook the large-scale solar power plant consisting of about 10,000 neatly arrayed solar panels from halfway up the hill from the path between the houses.

Unused 160,000m2 site in former coal mine

Koyagimachi is known as the location of Mitsubishi Heavy Industries (MHI) Ltd’s Nagasaki Shipyard & Machinery Works, where large tankers are built. With an expanse of evergreen trees remaining in the mountains, this is an area where manufacturing and nature co-exist.

What originally developed the region was, however, a coal mine. After Koyagi Coal Mine started operation in 1874, rows of houses for miners were built and a lot of miners lived in the town. The site of "SoftBank Nagasaki Solar Park" was previously a landfill for coal waste, previously called "bota," which is produced during the coal mining process.

After the war, Koyagi Coal Mine came under the management of Tetsugen Corp (Chiyoda Ward, Tokyo). However, the mine, where coal was mined from a tunnel extending under the sea, gradually became less cost competitive and closed in 1964. Tetsugen, which owned the coal mine facilities, has since played a key role as a major landlord in Koyagimachi in rebuilding the town after the mine closed. Partly thanks to the location close to central Nagasaki City, the town has successfully avoided a rural exodus as the houses for the miners changed to rental apartments and the hillside land was developed as residential areas.

However, an area of land approximately 165,000m2 (Takesaki District) along the coast, which was developed by landfilling a cove with coal waste, had been virtually unused and vacant for nearly 50 years partly because it was designated as an urbanization control area.

"In urbanization control areas, under the City Planning Act, no houses or other buildings can be built except those related to agriculture and fishery," said Katsunori Goto, director of Nagasaki Office, Kyushu Development Unit, Tetsugen. "We started discussions after the Urban Renaissance Agency suggested building a large-scale solar power plant. We had been consulting with the Agency for some time about development of the land."

At first, it was unclear whether the building in which the PV inverters were to be housed corresponded to the "buildings" prohibited under the City Planning Act; however, the Ministry of Land, Infrastructure, Transport and Tourism later judged it did not, which enabled the construction of the solar power plant.

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