WASHINGTON - Rain normally spoils a solar power contest. But three days of showers - and the use of thin-film photovoltaic (PV) technology - actually helped Team Germany win the 2009 U.S. Department of Energy (DOE) Solar Decathlon.

Team Germany was followed by the University of Illinois at Champaign-Urbana in second place, and Team California in third. The winners were announced by DOE Deputy Secretary Daniel Poneman at the competition site on the National Mall in Washington, D.C.

SOLAR POWER IN THE RAIN

Team Germany’s “Cube House” actually produced a surplus of power despite the three rainy days during the two-week contest. Every exposed face of the building was covered with power-generating panels.

On the roof there was a 11.1-kW PV system of 40 monocrystalline silicon panels. On the sides there were 250 thin-film panels that looked like glossy clapboards. The thin films used copper-indium-gallium-diselenide (CIGS) layers.

The combination system was expected to produce 200 percent of the energy needed by the house. The thin-film panels, while less efficient than conventional silicon, were projected to perform better in cloudy weather than silicon.

Team Germany got proof of this expected performance on the competition’s fifth day when skies turned gray and a cold rain dampened the contest’s solar village. By late afternoon, as D.C. commuters started going home and electricity demand throughout the city began climbing, the Team Germany house was producing 12.68 kW and consuming 12.33 kW, for a net export of 0.35 kW. “Team Germany built a gingerbread house packed with solar panels,” said Richard King, DOE Solar Decathlon director. “In the rain, the thin-film panels were making electricity. It made the difference.”

THE POTENTIAL OF ZERO ENERGY HOMES

In addition to educating the next generation of renewable energy engineers, architects, and green builders, the Solar Decathlon is intended to help propel solar energy and energy-efficient products into the marketplace and to demonstrate the potential of zero energy homes.

The 2009 Solar Decathlon challenged 20 student teams from across the United States, as well as from Canada, Germany, and Spain, to compete in 10 contests, ranging from subjective elements such as architecture, market viability, lighting design, and engineering, to technical measurements of how well the homes provided energy for space heating and cooling, hot water, appliances, and net metering.

New to this year’s competition, the Net Metering Contest challenged teams to generate surplus energy, above and beyond the power needed to run a house, which they fed into a power grid.

Of the 10 contests, Team Germany’s surplus power production earned the Net Metering award, which carried the greatest weight at 150 points. Team Germany also won the Comfort Zone contest for 100 points by best maintaining a comfortable temperature and humidity in its home. The requirements were to maintain an average indoor temperature of 72° to 76°F and maintain humidity of 40 to 55 percent.

The second-place University of Illinois team took top honors in the Hot Water contest, which required producing enough hot water for regular showers; the Appliances contest, which involved running a refrigerator and freezer, dishwasher, washer, and dryer; and the Home Entertainment contest, which involved not only running a television, computer, lights, and a cooking appliance, but also hosting two dinner parties and a movie night.

And although its team didn’t place in the top three, the University of Minnesota team won the Engineering award, honoring the solar home that best exemplified excellence in energy systems design, energy-efficiency savings, creative innovations in design, and reliability of energy systems.

Publication date: 11/23/2009