The Nakajima Treatment Plant of Toyohashi City Waterworks and Sewerage Bureau is located about 4km to the southwest of JR Toyohashi Station, facing the mouth of the Yagyu River, with Mikawa Bay spreading just beyond it. This is the city's largest sewage plant and has a huge site of about 29ha.

Huge fermenters next to mega-solar plant

This facility treats about 70% of all sewage water in the city's urbanized area and is, in fact, a renewable energy-based power generation facility with a maximum output of about 3MW. On the north side of the site, a mega- (large-scale) solar power plant and a biomass power generation facility with an output of about 2MW and 1MW, respectively, had both started operation by the fall of 2017 (Fig. 1).

Fig. 1: The mega-solar and biomass power plants started operation in the Nakajima Treatment Plant. (source: JFE Engineering)

A total of 9,328 polycrystalline silicon solar panels (265W/unit) were arrayed in the mega-solar plant area. The capacity of the installed solar panels is about 2.472MW while the rated capacity of PV inverters is 1.995MW. Generated power is boosted to 6.6kV before being transmitted to a high-voltage grid of Chubu Electric Power Co Inc. Generated power is sold at 32 yen/kWh based on the feed-in tariff (FIT) scheme.

Also, two huge cylindrical fermenters, which measure about 20m in height and 21m in diameter, and other facilities were set up in the biomass power plant area (Fig. 2). The capacity of the fermenter reaches about 5,000m3, and methane is derived as fuel for a gas engine power generator by anaerobically fermenting three kinds of organic waste.

Fig. 2: Two 20m-high fermenters were set up. (source: JFE Engineering)