Visit to Plant

Wooden Mounting System Brings Down Cost of Solar Power Plant

Costs less than steel systems, easier to handle

2014/03/01 18:59
Kenji Kaneko, Nikkei BP CleanTech Institute
Print Page

The Kashima Plant of Sumitomo Forestry Crest Co Ltd, a Sumitomo Forestry Group company, in Kashima City, Ibaraki Prefecture, is located on the Kashimanada coast, where a steady wind blows throughout the year and large windmills operate in the neighboring areas.

In November 2013, "Sumitomo Forestry Kashima Solar Power Plant" with 876kW output started operation in the site adjoining the plant (Fig. 1). Canadian Solar Inc's solar panel and Toshiba Mitsubishi-Electric Industrial Systems Corp's (TMEIC) PV inverter were adopted (Fig. 2). These products boast large market shares and are often seen at other solar power plants in Japan.

When you look behind the solar panels, however, you will recognize this power plant's unique feature: the mounting systems are assembled with wood. Compared with inorganic steel mounting systems, the natural warmth and presence that the wood surface brings about is impressive.

Sumitomo Forestry Co Ltd is known for its timber houses that primarily use domestic materials. Its "Mocca (Wood Use Integration) Department" is developing wood applications other than houses. "Can you build a wooden mounting system for a solar power generation system?" The Mocca Department was asked by a private entrepreneur during the sharp rise in the number of construction plans for solar power generation facilities that resulted from the implementation of the feed-in tariff (FIT) program.

Simple assembly of square cedar logs

Sumitomo Forestry established the Environmental Energy Group in the Forestry & Environment Division to deal with biomass and solar power generation businesses. At that time, the plan was devised to construct Sumitomo Forestry Kashima Solar Power Plant with 876kW output in the idle site adjacent to the Kashima Plant of Sumitomo Forestry Crest, a group company that manufactures and sells wood housing materials and equipment. In light of this plan, the company hurriedly started considering building part of the power plant using a wooden mounting system.

The mounting system had to be strong enough to withstand typhoons and other strong winds and durable enough to support the solar panels for 20 years, even under such severe weather conditions. In addition, cost becomes a key factor in the effort to get the wooden mounting system construction on track as a business. Business sustainability cannot be secured unless the wood mounting system is manufactured for an equivalent or lower cost compared with iron, aluminum and steel models.

After formulating a design plan and estimating the strength, durability and cost, the Mocca Department reached the conclusion that it could commercialize the wooden system and so made a full-fledged start.

Considering future volume production and cost, Sumitomo Forestry deployed 105 x 105mm kiln-dried (KD) square cedar logs that were generally used as a building material. In addition, the company aimed at a structural design assembled with these standard logs to be as simple as possible.

(Continue to the next page)