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SPIE Professional January 2010

Places in the Sun

The Solar Decathlon gave students and the public a personal look at the possibilities of energy-efficient living.

By Rich Donnelly

Hosting a cozy evening of dinner and a movie for friends. Doing a load of laundry. Generating enough electricity to put some of it back into the grid. These are just a few of the challenges to 20 unique solar-powered houses—and dedicated teams of student designers—at the Solar Decathlon in Washington, DC.

The Solar Decathlon is a biannual competition sponsored by the U.S. Department of Energy (DOE). Twenty university teams design and build solar-powered homes to meet strict construction and efficiency criteria for the event. The competition is intended to raise public awareness and further the integration of energy-efficient technology into residential building practices.

Team Germany's winning Cube Houseenergy-efficient, solar-powered houses built by 20 university teams from North American and Europe on the National Mall
The public toured the energy-efficient, solar-powered houses built by 20 university teams from North American and Europe on the National Mall. Left: Team Germany's winning Cube House. Photos courtesy of Stefano Paltera/U.S. Department of Energy Solar Decathlon

Team Germany, from Technische Universität Darmstadt, won top honors for the most attractive and efficient solar-powered home in the 2009 competition. The University of Illinois at Urbana-Champaign took second place followed by Team California in third.

The winners were announced by DOE Deputy Secretary Daniel Poneman. More than 200,000 visits were recorded at the 20 solar-powered homes displayed on the national mall in Washington, DC, over a 10-day period last October.

The 10 categories of scoring for the "decathlon" ranged from the functional to the aesthetic. Houses were scored in architecture, market viability, engineering, lighting design, communications, comfort zone, hot water, appliances, home entertainment, and net metering. On the more technical side:

  • The engineering contest considered functionality, efficiency, innovation, and reliability, as evaluated by professional engineers.

  • In the hot water contest, teams scored points by successfully completing several daily 15-gallon "hot water draws." The goal during these tests was to deliver 15 gallons of hot water (110°F/43.3°C) in 10 minutes or less.

  • For the net metering contest, each house was equipped with a utility meter to measure how much net energy the house produced or consumed over the course of the competition. Teams scored points for producing as much or more energy than they consumed. For a net consumption of zero, teams received 100 points; 15 of 20 teams accomplished this. Fifty bonus points were possible for surplus energy generation. Team Germany won the maximum.
Ohio State University solar decathlon students
Ohio State University students Dave Nedrow, left, Steve Winter, center, and Kara Shell, right, fold laundry in their solar-powered house on the first rainy day of the Solar Decathlon.
Customizing by Need

Each house incorporated an array of innovative technologies—available products and custom developments—to maximize efficiency.

One big change from the 2007 Solar Decathlon was the migration of solar panels from the roof to the façade. Several houses in the 2009 competition featured solar collectors on the sides of the house to take advantage of low winter sun angles and indirect solar radiation.

The home built by Team Germany, the winner in 2007 as well, was almost completely covered with custom vacuum insulation panels covered with CIGS (copper indium gallium diselenide) thin-film solar "shingles" - allowing it to generate more than 200% of its electricity needs.

  • Natural Fusion, the Penn State house, used a water bladder system embedded in the floor and phase-change material in the walls and ceiling to store heat during the day and emit it at night. The main source of solar electric power is cylindrical photovoltaics over a green roof. The cylindrical design of the photovoltaics collects 360 degrees of direct and indirect sunlight, to mimic a tracking array without moving parts.

  • Team Spain's Black and White House featured a solar-tracking inverted-pyramid rooftop made possible by a ball-and-socket, central-pivot system.

  • In Virginia Tech's Lumenaus, single-crystal silicon wafers are mounted between transparent glass plates in the solar array, so that some sunlight passes through the panel, is reflected off of the roof, and bounces back up to the back side of the wafer to generate additional electricity.
Virginia Tech solar-powered house
Team Virginia Tech's solar-powered house glows at night during the lighting design contest.
Maximizing Efficiency

Most of the houses included a computerized monitoring and regulating system that responded to usage patterns and environmental conditions to maximize efficiency. The user can adjust the solar arrays, blinds, and other systems remotely via iPhone or other Internet connection.

Johnny Rodgers, from a Canadian team of students from three universities, said his Team Ontario/BC developed "an intuitive, really useful system" for their home called North House that allows residents to "gain energy feedback so they can make better decisions about their energy consumption."

Flexibility was built into most of the houses, from the energy monitoring systems that allow- even encourage-residents to modify their usage patterns, to the modular furnishings that allow the relatively compact living spaces to be expanded for different uses. Many of the teams from warmer climates incorporated extensive outdoor living spaces into the homes, such as the courtyard that Team California's Refract House wraps around. BeauSoleil, from the University of Louisiana at Lafayette, incorporated a covered porch for socializing, a space between the kitchen and living room bookended by sliding glass doors.

Commercializing Technology

The opening of the Solar Decathlon on 8 October provided a platform for U.S. Energy Secretary Steven Chu to announce up to $87 million in funding for the development of new solar energy technologies and the rapid deployment of available carbon-free solar energy systems. The 47 projects with universities, electric power utilities, DOE's National Laboratories, and local governments will help accelerate the commercialization of solar technologies in an effort to achieve cost-competitive solar electricity by 2015. More information is available at www.eere.energy.gov/solar/.

Each house was targeted toward a specific market, from independent living for seniors (Iowa State's Interlock House) to "a minimal zen style, ideal for a relaxing vacation home" (Team Spain, Black and White House).

Rice University's Zerow House is a modern interpretation of a row house, targeting low- to middle-income residents and incorporating affordable, practical energy-saving solutions. The house will be donated to Project Row Houses, a community organization that develops low-income housing in Houston, TX.

The Solar Decathlon's run in Washington ended on a soggy note, as rain plagued the last several days. Even so, enthusiastic crowds turned out to tour the homes and listen to the student tour guides who still had plenty of energy even after more than a week of long days and late nights. DOE's Richard King, director of the event, said that "you can just see a raising of the bar, a step up this year, with these houses." He said the solar systems on the houses showed increasing sophistication, and "the architects have really discovered that it's a building product," incorporating panels into facades, overhangs, and creating a lot of power even on cloudy days.

"It's been incredibly fun out here all week long," King said.

For a list of the 2009 teams and links to team sites: solardecathlon.org/teams.cfm

See additional coverage of the Solar Decathlon and other news about solar and alternative energies on the SPIE Newsroom:

In Madrid 2010, Washington 2011

The Solar Decathlon travels across the Atlantic this year. Solar Decathlon Europe will take place this June in Madrid.

The European organizers have licensed the name from the U.S. Department of Energy, which organizes the U.S.-based events. The DOE is providing advice and support to the Madrid effort.

In 2011, the Solar Decathlon returns to Washington, DC.

Proposals have already been submitted and the qualifying teams were to receive their notifications in December. Design and construction of a solar house for the event is a two-year project. See solardecathlon.org for the complete list of competitors.

Rich Donnelly 
Rich Donnelly is managing editor of the SPIE Newsroom. 

Have a question or comment about this article? Write to us at spieprofessional@spie.org.

DOI: 10.1117/2.4201001.14

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