Harnessing The Sun

A home wrapped in solar panels won this year’s Solar Decathlon, put on by the Department of Energy on the National Mall, in Washington, D.C. The competition, held on Oct. 8 to 18, brought together teams of students from Canada, Germany, Puerto Rico, Spain, and the U.S. to showcase how energy technologies can be incorporated into a real home.

The competition, which began in 2002, invites architecture and engineering students and faculty to design energy-efficient homes and assemble them on-site. This year marked the first time the houses were tied to the electric grid rather than backed up by batteries. This change is significant because homes that generate excess electricity can put it back on the grid.

The teams competed for points in 10 categories of sustainability and practicality, with electricity production carrying the most weight. Despite cold and rainy weather, the event attracted more than 200,000 people.

Technical University of Darmstadt’s Team Germany brought in the big photovoltaic guns and won the contest. The team’s home was encased in photovoltaic cells: 250 thin-film copper indium gallium diselenide (CIGS) panels lined the four outer walls, and 40 monocrystalline silicon panels sat on the roof. In all, the “surPLUShome,” as the team calls it, could generate 19 kW of power at peak production—four to six times more than usual residential rooftop 
installations.

The German students’ goal, the team said, was to push the technological envelope, and their reliance on CIGS panels paid off. These panels have the advantage of being more efficient than silicon panels on overcast days. But the roof’s silicon panels produced the most electricity overall, architecture team member Patrick Tauchert tells C&EN. During the almost-two-week period the panels were operating, the house produced 400 kWh of electricity but used only 260 kWh.

Some other teams used more affordable technology. For instance, Rice University students developed a prototype row house, capable of producing 4.2-kW of power, at a cost of $200,000, a fraction of the surPLUShome’s estimated $650,000 to $850,000 price tag. The Rice team plans to build a prefabricated version of the prototype for $80,000 when they return to Texas.