1MW of panels set up in farming zone
Koshi City in northern Kumamoto Prefecture, Japan, has recently seen a population increase after a new urban area was developed as a commuter suburb of Kumamoto City. The area also boasts agriculture and stock farming in its northern area where the ground is covered by humus soil called "Andosol," volcanic ash deposits from Mount Aso.
The southern side of the Koshi River, in particular, is one of the prefecture's largest breadbaskets boasting huge areas of farmland. The "Koshi Agricultural Energy Project Solar Power Plant," a mega- (large-scale) solar power plant with an output of about 1MW, is located in an area surrounded by rice and vegetable fields (Fig. 1).
The power plant began operation in March 2014 and sells generated power at 36 yen/kWh using the feed-in tariff (FIT) scheme. A total of 3,920 solar panels manufactured by Canadian Solar Inc were set up on simple one-legged pile foundations in a north-south direction. Foundations and mounting systems manufactured by Schletter GmbH of Germany and PV inverters of Toshiba Mitsubishi-Electric Industrial Systems Corp (TMEIC) were adopted.
Leveraging the designing knowhow of juwi Inc of Germany, which is a global, highly experienced engineering, procurement and construction (EPC) service provider for mega-solar plants, this mega-solar plant was constructed after careful preliminary studies of soil bearing capacity and other elements. During the five and a half years since the operation began, the solar plant has reportedly been operating soundly, despite experiencing strong typhoons and earthquakes (Fig. 2).
Partly because of the agriculture and stock farming prospering around the plant, however, the panel surfaces reportedly grew quite dirty. Accordingly, all the solar panels were cleaned in October 2018. The cleaning was carried out in expectation of cost-effectiveness because the amount of power generation increased about 5% as a result of a preliminary test cleaning of some panels. The panel surfaces were washed with soft mops using water carried into the site in tanks (Fig. 3).