Two-digit upswing in power generation

Mega Solar Tokorozawa started selling power in March 2014. It was constructed in Tokorozawa City's "Kitano General Waste Final Disposal Site." Its panel capacity is 1.053MW while the PV inverters' rated capacity is 1MW. This was reportedly Saitama Prefecture's first mega- (large-scale) solar power plant with an output of over 1MW. The unit price of power based on the feed-in tariff (FIT) scheme is 36 yen/kWh.

In its 20-year business plan, power sales are expected to total about 1 billion yen (approx US$9 million); expenses will be about 680 million yen, resulting in an overall profit of about 320 million yen. Tokorozawa City keeps the income from power sales as its "Eco Town Promotion Fund" separate from its general budget, and uses it for its environment-related subsidy system, for example.

Constructing a mega-solar plant on a landfill disposal site faces challenges such as weak ground, the risks of uneven subsidence and so forth.

Tokorozawa City adopted "FXT steel tube foundations," in which two steel tube pipes are driven into the ground diagonally, crisscrossing over each other, as a measure against weak ground. While limiting the panel angle to 10° to secure a mega-class capacity on the limited site, Tokorozawa City set up an observatory, electronic signage to display the amount of power generation and educational panels in view of the plant's use for environmental education (Fig. 4).

Fig. 4: FXT steel tube foundations adopted as measure against weak ground source: Nikkei BP)

A total of 4,298 polycrystalline silicon panels (245W/unit) of Sharp Corp and two 500kW-output PV inverters of Toshiba Mitsubishi-Electric Industrial Systems Corp (TMEIC) were adopted. A standalone battery (2.5kWh) of Eliiy Power Co Ltd and two more solar panels are provided so the battery system can autonomously operate and charge power in an emergency for the use of information devices and others (Fig. 5).

Fig. 5: Sharp solar panels and TMEIC PV inverters (source: Nikkei BP)

The amount of power generation has outperformed the business plan, marking a 13.4% upswing to about 1,278,000kW and roughly 53 million yen in fiscal year 2017, compared with the 1,120,000kW and 43 million yen estimates, respectively (Fig. 6).

Fig. 6: The power generation amount is released to the public on the city's website. Above are the amounts of power generation in 2017. (source: Tokorozawa City)