Heavy chemical industries such as iron manufacturing and petrochemical complexes are concentrated in the Oita Coastal Industrial Zone to the east of Oita City, Oita Prefecture, Japan. Mitsui Engineering & Shipbuilding (MES) Co Ltd's Oita Works is located in this area. The works are the company's manufacturing base for large cranes used for loading and unloading cargo at ports and harbors. The site is about 1.7km2.

In December 2013 the "Mitsui Engineering & Shipbuilding/Mitsui Fudosan Oita Solar Power Plant" (hereafter Oita Solar Power Plant), a mega- (large-scale) solar power plant with an output of about 17MW, started operation in the site of the Oita Works. This power plant was developed and is operated jointly by MES and Mitsui Fudosan Co Ltd.

I visited the mega-solar plant to write about its changes during the last three and a half years after the plant had been covered in this section in April 2014 (See related article) (Fig. 1).

Fig. 1: Mega-solar plant with a total output of almost 70MW. On the left is the initial mega-solar plant with an output of about 17MW. In the center and on the right is the new 45MW-output solar plant built utilizing a former golf course. (source: MES)

Compared with the time when this plant was first covered in this section, the existing Oita Solar Power Plant has been expanded while the new "Oita Hiyoshibaru Solar Power Plant" (hereafter Hiyoshibaru Solar Power Plant) has been separately constructed. Both were built in the Oita Works site utilizing the former Hiyoshibaru Country Club, which was closed in spring 2014.

At the Oita Solar Power Plant, the capacity of solar panels and the rated capacity of PV inverters to be connected with the grid were initially set at about 17MW and 14MW, respectively. Adding about 42,334m of the former Hiyoshibaru Country Club to this, 14,070 solar panels with an output of about 3.7MW and PV inverters with an output of 3MW were additionally set up while the grid connection amount was also increased.

Following this expansion, the panel and grid capacities were boosted to about 21MW and 17MW, respectively, at the Oita Solar Power Plant.

Meanwhile, using the roughly 460,000m2 remaining of the former Hiyoshibaru Country Club, the new Hiyoshibaru Solar Power Plant became an even larger mega-solar plant with a panel capacity of about 45MW and a grid capacity of 34MW (Fig. 2). This plant was jointly developed and is operated by MES, Itochu Corp and Kyudenko Corp.

Fig. 2: At the newly built "Hiyoshibaru Solar Power Plant," 179,536 solar panels were arrayed. (source: Nikkei BP)