Visit to Plant

1.6MW Solar Plant Supplies Power to Local Sewage Plant via Independent Cables

Excess power converted to heat, hydrogen, electricity

2018/10/02 12:25
Kenji Kaneko, Nikkei BP Intelligence Group, CleanTech Labo
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Independent power cables erected on 30 utility poles

A number of leading companies in Japan have set up their plants in the Soma Chukaku Industrial Park along the coast of northern Soma City, Fukushima Prefecture, Japan. As you drive on Route 6 north from the town, panels of a mega- (large-scale) solar power plant will appear on the right before the stacks of a thermal power plant while Soma City Sewage Plant will appear on the left.

After the Great East Japan Earthquake, mega-solar power plants based on the feed-in tariff (FIT) scheme started operating in series and transmitting power to the grids of Tohoku Electric Power Co Inc along the coast of Fukushima Prefecture, in accordance with the prefecture's vision to promote renewable energy.

This mega-solar plant along Route 6, however, does not transmit power to the grids using the FIT scheme. The generated power is directly supplied to the sewage plant across the road. "Directly" means the plant transmits its power via its own cables which it erected independently without using Tohoku Electric Power's power transmission cables (Fig. 1).

Fig. 1: Mega-solar power plant in "Soma IHI Green Energy Center" (source: IHI)

Aerial cables were erected for about 1.2km between the mega-solar plant and the sewage plant over Route 6 via 30 utility poles. The service type, in which power is supplied and sold by a power plant via such "independent cables," is called a "specific power transmission/distribution company." When 20-year stable power selling business is guaranteed by the FIT scheme, such a specific power transmission/distribution company with a mega-solar power plant is very rare (Fig. 2).

Fig. 2: Solar power transmitted to sewage plant via 1.5km independent cables (source: Nikkei BP)

'No reverse flow' sought for limited grid capacity

This mega-solar plant is one of the facilities at "Soma IHI Green Energy Center" which was constructed and is run by IHI Corp. The center's opening ceremony took place in April 2018. A solar power generation system with an output of 1.6MW and batteries with a total output of 2,500kWh, among other facilities, were installed in a 54,000m2 site (Fig. 3).

Fig. 3: Li-ion batteries with a total output of 2.5MWh (source: Nikkei BP)

Partly because IHI constructed and has run plants in Soma City since 1998 as the production base of its aero engine and space business area, the company came to approach smart community business combined with the reconstruction plan in collaboration with the city after the earthquake. The project's concepts were "local production and consumption of renewable energy," "enhancement of disaster prevention capability" and "advanced business that leads to revitalizing local communities," and IHI specifically advocated the use of "hydrogen" systems.