A high-tech building covered on all sides with solar cells has won an international contest for the best home powered only by the sun.
Team Germany, which also won in 2007, took first place in the Solar Decathlon, beating out teams from Illinois and California.
At a ceremony Friday in Washington, D.C., the Department of Energy announced the winners of the competition, in which student teams designed and built solar homes on the National Mall. For the past week, the homes have been scored on architecture, market viability, and a number of objective measures, such as how much hot water the house can generate.
On the final day, Germany beat out its rivals by getting the highest score in the net metering contest, or the amount of excess electricity the home produced.
Germany's team, from Technische Universitat in Darmstadt, designed a building that not only had solar panels on the roof, but also on the walls, making the potential generation as high as 11,000 watts. The specially designed siding that used thin-film solar cells fitted onto aluminum strips. The solar cells ran all the electrical systems, including the hot water heater, and are capable of generating about twice as much electricity as the house needs.
Underneath the clapboard was a highly insulating material. That was one of a number of techniques, including automated louvers to take in outside air, that home used to increase its energy efficiency and conform to the Passive House low-energy home standard.
The cube-like structure not only allowed for a maximum surface area for solar cells, but also allowed the architects to build a two-story interior, unlike the other entrants. The cost for this sophisticated home was at the high end in the competition, with an estimated price tag in the $650,000 to $850,000 range.
By contrast, the second place team--Team Illinois from the University of Illinois at Urbana-Champaign--made a home on the low end of the price range, estimated at about $250,000.
The Illinois team chose to focus on local architecture and local suppliers for its house. It used reclaimed wood from a family barn and a local grain elevator for the siding and decking. On the inside, it used a new product--structural bamboo beams--made from a fast-regenerating plant.
The designers at Illinois, too, chose to run the house entirely on solar electric panels, rather than have a combination of solar photovoltaics and solar hot water panels for all heating and cooling. The all-electric system allowed it to use highly efficient air-source heat pump. The building was also heavily insulated, getting an estimated R50 by using spray foam, and chose highly efficient appliances inside.
Team California, which was a collaboration between Santa Clara University and the California College of the Arts, came in third place, placing at the top in the communications and architecture categories.
The homes in the competition were limited to 800 square feet but California designed its home to give it a bigger feel by having different zones and a large deck that integrated with the main living space.
The team, which also scored well for home entertainment and appliances, designed a home-automation system that allows home owners to monitor energy usage from a touch-screen display. The same display also allows people to control lighting, the shades, and appliances.
The full scorecard and more photos of the homes can be seen at the Solar Decathlon site.