SB Energy Corp and Mitsui & Co Ltd started the construction of the SoftBank Tomatoh Abira Solar Park, a mega-solar (large-scale photovoltaic (PV)) power plant with a maximum output of about 111MW, in Toasa, Abira-chou, Yufutsu-gun, Hokkaido Oct 7, 2013.
SB Energy Corp carries on a renewable energy business, etc in the SoftBank Group.
We interviewed Takeshi Yokota (Fig. 1), managing executive officer of Toshiba Corp, which provides engineering, procurement and construction (EPC) services for the power plant, on the overview of its facilities.
The PV panel and power conditioning subsystem (PCS) of the power plant will be supplied by Toshiba and Toshiba Mitsubishi-Electric Industrial Systems Corp (TMEIC), respectively. And Toshiba Plant Systems & Services Corp will build mounts.
With 444,024 monocrystalline silicon PV cells, each of which has a maximum output of 250W, the amount of power generated by the plant per year is expected to reach about 108,014,000kWh, which is equivalent to the amount of electricity consumed by about 30,000 households in a year.
Hokkaido is often considered to be a region that is not suited for PV power generation. However, the construction site of the new PV power plant is ideal for it in terms of the amount of sunshine and temperature, Yokota said. Because crystalline silicon-based PV panels generate less electricity at high temperatures, the not-too-high temperature in the region has a positive impact.
For the construction of the SoftBank Tomatoh Abira Solar Park, Toshiba reduced construction period, installation cost and the impact of deposited snow on power generation. They were achieved mainly due to the improvements made to mounts.
First, to reduce construction period, the legs of the mounts are embedded in the ground. Then, only the areas around the legs are covered with concrete (Fig. 2). Each mount consists of a V-shaped structure made of plated steel plate and a bar-like leg. This method shortens construction period by half, compared with a conventional method that installs mounts after groundwork, Yokota said.
Second, Toshiba made improvements to the mount and PV panel in the aim of preventing the plant from being covered with snow and the amount of generated electricity from decreasing in winter. As for the mount, the company designed it so that the height of the lowest part of the panel becomes 90cm from the ground. Because the snow accumulation on the construction site (Abira-chou) is about 70cm, the power plant is less likely to be covered with snow even on a snowy day.
In regard to the PV panel, Toshiba employed a panel with a flat surface so that snow is hardly accumulated on it. This panel was realized by changing the positions of electrodes, etc. The panel is set at an angle of 30°.
Furthermore, Toshiba made improvements to the locations of the PV panel and PCS. If PV panels can be placed with regularity to form a grid shape, it is easy to decide the locations of PCSes with regular intervals. However, the construction site has a complicated terrain (Fig. 3).
"To place as many panels as possible on the complicated terrain and generate as much electricity as possible, the locations of PCSes and the way of using them are important," Yokota said.