For a week and a half in mid-October, the National Mall in Washington, D.C., was transformed into a solar village, as colleges from around the country and around the world competed in the third Solar Decathlon. This biennial competition challenges 20 student teams to design, build, and operate houses that are completely powered by the sun.
A team from Germany took the top prize, but all 20 living laboratories showcased existing and new technologies in energy generation, energy conservation, resource efficiency, and a number of other green attributes, all in a structure that can be easily imagined as a real home, albeit within the confines of the contest's 800-square-foot limit.
In addition to challenging students to learn and innovate, the Solar Decathlon was an educational opportunity for the consumers who toured the houses during the week. This year's event saw a record 120,000-plus visitors, reports Richard King, director of the Solar Decathlon for the Department of Energy (DOE), which sponsors the event.
"People are being told they should go green, but one of the benefits of the Solar Decathlon is it shows them how," King says. "You can not only learn how to produce all the energy you need from the sun, but you can learn how to save energy inside your house." It's hard to grasp on TV, he explains, "but when they walk in a house and see it … they get a better feel for just what it is."
Accepting the ChallengeThe teams—17 from the United States and Puerto Rico plus a team each from Canada, Germany, and Spain—began working on design and construction two years ago; the completed projects were transported to D.C. and then reassembled in the days preceding the event.
Each house was judged in 10 categories, both subjective and objective: architecture, engineering, market viability, communications, comfort zone, appliances, hot water, lighting, energy balance, and getting around. Students were required to prove the houses are fully functional, including by making dinner and having enough power leftover from running the home to operate an electric car.
The winner of the competition, according to the DOE, is the house that best blends aesthetics and modern convenience with maximum energy production and optimal efficiency. This year that honor went to Technische Universität Darmstadt of Germany. The house's passive solar design includes an outer layer of oak louvered frames outfitted with photovoltaics (PV) to provide shading and protection as well as generate energy. The interior incorporates furniture into the home's platform. Three types of photovoltaics and countless other high- and low-tech features were utilized throughout.
In addition to the PV arrays of various types, sizes, and installations, a number of other familiar and proven green building products and techniques were used throughout many of the homes. Adaptable, modular designs were popular, as were SIPs construction, passive solar, and daylighting considerations. Common products included radiant-heat flooring, bamboo, recycled glass tiles, and paper-based countertops and paneling.
Local woods also were prevalent. Carnegie Mellon utilized long-leaf yellow pine flooring salvaged from a nearby demolition site and included a student-made countertop that creatively patchworked 20 species of wood from around campus. Penn State turned fallen trees from its property into furniture.
Yet even with some similarities in products, each team approached the concepts of sustainability differently—resulting in home styles ranging from traditional to ultra-modern, in creative construction techniques, and in the unveiling of brand-new technologies. The University of Maryland, for example, introduced a team-designed desiccant waterfall that removes humidity from the air to ease the load on the air conditioner. Ceiling-mounted radiant panels, reminiscent of refrigerator coils, condition the "elementhouse" from the University of Illinois at Urbana-Champaign, eliminating the need for air ducts. Santa Clara designed the industry's first bamboo I-joists. And the list goes on.
Face of the FutureFor skeptical homeowners, this array of styles and materials showcased the many ways that building and living green can be attractive, practical, and functional. The students, however, didn't need convincing. The enthusiasm in their voices and the pride on their faces seemed as much a reflection of their hard work as it was about what they will continue to achieve as the next generation of architects and engineers.
Indeed, in his opening remarks DOE assistant secretary of energy efficiency and renewable energy Andy Karsner equated young people's enthusiasm for green building to similar excitement in the technology sector two decades ago.
"We're the generation to make a change," confirmed Nora Hendrickson, a senior mechanical engineering major at Santa Clara. "I think we have a lot of power."-- BUILDING PRODUCTS
Technische Universität Darmstadt. The overall winner in the 2007 Solar Decathlon, the German team focused on passive energy design and developed the house specifically for the Washington, D.C., climate. The house's outer segment of oak louvered frames outfitted with photovoltaics generates electricity while providing shading and protection. The second layer of the house is the thermal envelope; the third layer is the living space. The living area features furniture and a bed integrated into the platform while shelves incorporated into the walls define the home's zones. www.solardecathlon.de.  |
 | Penn State University. The "MorningStar Pennsylvania" house boasts an ensemble of local products, including Pennsylvania bluestone, recycled steel, and furniture made from fallen wood found on campus. An eye-catching sliding panel made of glass milk containers diffuses light and may eventually be filled with liquids that absorb heat. In addition to a fixed photovoltaic array on the roof, the house has Solar Slates on the east and west façades that power a dedicated DC/LED lighting system. A gliding movable wall allows the bedroom and living room to shift in size. solar.psu.edu. |
| Santa Clara University. Finishing third overall under a theme of "design with purpose," the Santa Clara "Ripple" house offers sustainable features in a space and style that are traditional and livable. The team designed industry-first bamboo I-joists, and bamboo also is used for the cabinets and flooring. Air conditioning is solar-powered thanks to an absorption chiller that uses hot water from flat-plate thermal collectors. Insulated Nana Wall telescoping doors open the house up to the outdoors. scusolar.org. |  |
 | MIT. This WarmLight wall on the south-facing side of MIT's "Solar 7" house converts sunlight into heat during winter days and radiates it into the home. Other highlights from the project include Kirei sorghum cabinets, SIPs construction, a white rubber roof membrane to keep solar cells cooler, and pocket and telescoping doors that allow for a flexible interior design. mit.edu/solardecathlon. |
| University of Maryland. The "LEAFHouse" (Leading Everyone to an Abundant Future) was the second-place finisher and the winner of the People's Choice Award. One of the most unique features is its liquid desiccant wall, a waterfall that removes humidity with very little energy to help reduce the workload on the air conditioner. Other details include solar water heating tubes; rainwater collection, filtration, and irrigation; greywater collection and filtration; ductless mini-split air conditioning with a 16.5-SEER rating; radiant floor heating; and an energy recovery ventilator. Tags throughout the house identify how the various systems conserve energy. www.solarteam.org. |  |