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Self-powering office buildings just around the corner (Nikkei)

The outer walls of Taisei's prototype zero-energy building in Yokohama are covered with thin-film solar cells.

The outer walls of Taisei’s prototype zero-energy building in Yokohama are covered with thin-film solar cells.

TOKYO — Japanese general contractors are making strides toward office buildings that can take care of their own energy needs. Taisei is set to test the world’s first prototype zero-net-energy office building in Yokohama.

The three-story building, which was unveiled to the media June 16, has a greenish, all-glass exterior. “A solar power device integrated into the windows covers 50% of the entire exterior surface,” a Taisei engineer explained.

The windows generate power with an organic thin-film solar cell. The system, developed with Mitsubishi Chemical, converts sunlight into electricity with a conversion rate of about 5%. With chemical produ  The solar panel portion of the window is only 2mm thick. The panel is bendable, light and easy to install. On a curtain-wall building — a structure in which the exterior walls do not carry a load — almost the whole surface area can be used to generate juice.

“We want to commercialize zero-energy buildings by 2020,” Taisei President Takashi Yamauchi said during a news conference at the prototype building.

Smart lighting, cold water

Taisei and other major construction companies are testing a variety of technologies to make energy self-sufficiency possible. Starting in July, Taisei will use the prototype building to collect data it hopes will contribute to reaching that 2020 goal.

While the building uses the solar panels to produce electricity, a range of other systems hold down energy consumption. Sensors turn lights on only in areas where there are people. The building is also designed to maximize natural light by reflecting it on the ceiling. To cool the interior, cold water is run through ceiling pipes, and the air around the pipes is sent into the rooms. Air from outside is brought in through floor vents, too.

Taisei sees the building’s power usage coming to just 25% of the average level for Tokyo office buildings in 2010.

Still, no matter how efficient a building is, it will still need a steady supply of electricity. Since solar generation is at the mercy of the weather, the prototype is connected to the power grid. Taisei hopes the solar cells will provide enough to fully offset the purchased power. If they do, over the course of a full year, Taisei’s building will be the first to accomplish the feat of using zero net energy from the outside.

Taisei has worked with a number of companies to realize its vision. Aside from Mitsubishi Chemical, the general contractor teamed up with Mitsubishi Heavy Industries and office furniture maker Okamura to develop a special desk lamp.

This lamp uses the Mitsubishi Heavy group’s OLED panel — a thin, bendable layer of organic light-emitting diodes — to emit light that is easier on the eyes than today’s regular LED bulbs. The lamp itself is manufactured by Okamura.

Installing the lamps throughout an office makes it possible to reduce the use of ceiling lights.

Post-disaster rush

Rival general contractor Obayashi, meanwhile, is developing its own systems for zero-energy buildings at a test facility. Shimizu says it has already built zero-energy buildings for a religious organization, though these structures achieve energy self-sufficiency as a group, whereas Taisei’s stands alone.

Part of the impetus for this development rush was the earthquake-tsunami disaster that struck Japan in March 2011. The nuclear meltdowns that followed, and the subsequent power shortages, raised awareness of the need for faster research into energy-saving and energy-generating technologies.

While costs will have to come down to make zero-energy buildings commercially viable, Japanese contractors hope the structures will eventually give them an edge over competitors in overseas markets.

cers competing to improve the performance of such cells, generation efficiency is expected to improve.


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