The U.S. Department of Energy (DOE) hosted its 2011 Solar Decathlon in Washington, D.C., at the end of September.

For the energy industry, the Solar Decathlon means more than developing solar energy. The competition breeds innovation in energy efficiency and design, using technology and products that are currently on the market. Biennially, the DOE chooses 20 teams from around the world to each build a house that adheres to strict guidelines in efficiency and sustainability.

Most teams look at past competitions and examine what worked and push the designs further, creating an evolving trend of increasingly efficient design. Clearly, the focus had shifted to the real-world application of solar energy from some of the futuristic designs of past competitions. The student engineers and designers explained how visitors could take home and implement energy-saving ideas immediately.

The homes, which had more pronounced themes this year, were designed to fit organically into their indigenous settings. The City College of New York’s Roofpod is based on the idea that the most under-used urban space is the rooftop. The University of Calgary’s TRTL design was inspired by the tipi (teepee) and was intended to raise awareness of critical native housing issues in Canada.

The University of Illinois’s Re_home is designed to be a sustainable solution for disaster relief. Preconstructed in two pieces, it can be quickly deployed and assembled within a day. Team Tidewater (Va.) built one unit of a proposed multifamily dwelling that aims “to contribute to walkable city-center neighborhoods.”

At the conclusion of this year’s competition, the University of Maryland’s three-module WaterShed house came out on top, earning 951 points out of a possible 1,000. Purdue University’s InHome suburban farmhouse placed second with a total of 931 points, while New Zealand’s beach cottage, which uses recycled sheep’s wool as insulation, placed third with 919 points.

Judges score each house in 10 categories. In addition to architecture, engineering, and market appeal, an affordability category was new this year. Teams were awarded 100 points if they kept the cost of their house under $250,000. If a house cost more than $600,000 to build, that team would not receive points.

“The houses on display blend affordability, consumer appeal and design excellence with optimal energy production and maximum efficiency,” said Energy Secretary Steven Chu in a DOE press release. “These talented students are demonstrating to consumers the wide range of energy-saving solutions that are available today to save them money on their energy bills.”

Of course, more than building for energy, many houses featured innovation in integration. Team California’s house was notable for its “outsulation” concept, which used insulation on the exterior of the house to help regulate temperatures inside, but it also featured a robust integration of lighting control that users could toggle with a sleek iPad app the students developed themselves.

On the topic of innovation, Team Tennessee’s house featured cylindrical Solyndra PV panels mounted above a white membrane on the roof’s surface that reflects light back up. In this way, the team could gather the energy from the sunlight that slips between the panels, which other PV panels would miss. Appalachian State University’s Solar Homestead, which won the People’s Choice award, also had bifacial solar panels, which the team promoted with giveaway reflective hats that visitors could wear when walking beneath the panels, thereby becoming part of the solution.

At the end of each competition, teams must figure out what will happen to these innovative marvels. Some return to their university campuses to promote efficiency in design. Some are sold to institutions for research or to individuals, looking for a sleek getaway home. Parsons NS Stevens partnered with Habitat For Humanity on its Empowerhouse, which will be donated to a family in the Washington, D.C., area. All the structures live on to promote efficient energy and environmental design and help shape the future of systems integration in the residential market.

The next Solar Decathlon will take place in 2013. The participants have already been selected and no doubt were busy scouting out this year’s competition. The DOE recently opened the location for bidding, so be on the lookout. The next competition may be coming to a locale near you.