Beginning Oct. 8, 2009, the National Mall in Washington, D.C., will once again host a temporary village of 20 completely solar-powered houses designed and built by university students from the United States, Canada, and elsewhere around the world. The U.S. Department of Energy's 2009 Solar Decathlon pits 20 student teams against each other in a competition to see which house represents the best blend of design aesthetics, modern conveniences, maximum energy production, and optimal efficiency.

Designed to focus consumers' attention on rising energy demands and the need to find alternatives to conventional energy sources, the Solar Decathlon offers powerful solutions for using energy more efficiently and obtaining energy from renewable sources. Through the competition, students learn about the benefits of energy efficiency, renewable energies, and green building technologies, and leave with an educational foundation on which to build potential future careers in engineering, architecture, and construction. The competition also raises public awareness of renewable energy, energy efficiency, and green building options, and encourages research and development of energy production technologies and more efficient systems.

Once again, Solar Decathlon homes will be scored in 10 categories: architecture, market viability, engineering, lighting design, communications, comfort zone, hot water, appliances, home entertainment, and net metering. In this year's competition, the net-metering contest will evaluate how much energy each home produces and consumes during the competition. Each home will be outfitted with an electric meter, and teams can score up to 150 points total. Producing as much energy as the house needs will garner 100 points. Teams are eligible for an extra 50 points if their houses produce a surplus of energy, causing the electric meter to run backwards.

The competition begins Oct. 8 and ends with the results announcement on Oct. 16. Solar houses will be open to the public for tours Oct. 9 – 13 and Oct. 15 – 18, but will periodically close for judging from Oct. 8 through Oct. 16.

Competing in this year's Solar Decathlon are:

Cornell University—Cornell's 2009 Solar Decathlon House draws on the vernacular agricultural architecture of upstate New York, combining modular design with a courtyard assembly. Spare interiors hide surprises, such as a bed tucked away in the ceiling to save space. Lighting and solar thermal controls minimize the need for climate control.

Iowa State University—Designed as an infill residence, Iowa State's 2009 Interlock House was built using unique building components and materials developed through the decathlon team's collaboration with the university's Biopolymers & Biocomposites Research Team, which promotes research in the development of biorenewable polymers from Midwest crops, encourages bioplastics in industry, and works toward new formulations and processing techniques. Passive solar design, multiple zones, and efficient active systems reduce energy demands, while solar electric and thermal collector systems generate energy.

The Ohio State University—Ohio State's Solar House 1 redefines living spaces and encourages occupants to take an active role in the house's core functions, such as ventilation. A central living space with concealed components—kitchen, bedroom, living room—can be reconfigured to suit the occupants' needs. The solar arrays are mounted to an operable frame that allows seasonal adjustments of tilt.

The Pennsylvania State University—Penn State's 2009 Solar Decathlon house is a single module with four operable window walls along its South side and a clerestory running the length of the South side, providing natural ventilation, interior daylighting, and passive solar performance. A green roof integrated photovoltaic system provides most of the home's energy, and an active awning along the house's South side tracks the sun throughout the day, automatically shading the house from summertime heat gain and collecting energy through embedded photovoltaic cells.

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