The U.S. Department of Energy Solar Decathlon challenged 20 collegiate teams to design and build energy-efficient houses powered exclusively by the sun. Here’s how they did.

The U.S. Department of Energy Solar Decathlon challenges 20 collegiateteamsto design and build energy-efficient houses powered exclusively by the sun. These teams spend almost two years creating houses that compete in 10 contests: architecture, market viability, engineering, lighting design, communications, comfort zone, hot water, appliances, home entertainment and net metering-the extent to which the house would draw from or give back to the electricity grid each year.

The competition is held in Washington, DC, on the National Mall. The winner is the team that best blends cost-effectiveness, consumer appeal, and design excellence with optimal energy production and maximum efficiency.

The first Solar Decathlon was held in 2002 and has since been held in 2005, 2007 and 2009. Team Germany, from Technishce Universität Darmstadt, won in 2007 and took first place again in 2009. Team Germany focused on producing surplus energy by using the maximum building dimensions allowed, covering every available surface with photovoltaics and pushing the envelope with new technologies.

Second place went to the team from the University of Illinois at Urbana-Champaign. Their Gable House was one of the first to be assembled and ran like clockwork throughout the competition. Team U of I focused on performance and also achieved elegant simplicity in design.

Third place went to Team California, from Santa Clara University and California College of the Arts. Team California’s Refract House finished first in both architecture and communications, second in engineering and tied for third in market viability.

The next Solar Decathlon will take place in fall 2011. Open to the public free of charge, the event will again take place on the National Mall. Visitors can tour the houses and learn how energy-saving features can help them save money today. You can learn more about the event, the 20 teams that will compete in 2011, and how your team can apply for the next event