Competition is underway in the Department of Energy's (DoE) Solar Decathlon, in which 20 teams of college and university students compete to design, build, and operate the most attractive, effective, and energy-efficient solar-powered house. The house designs entered in the competition not only capture heat and light from the sun, but also integrate design features to take advantage of cooling breezes and shading. By combining these proven energy efficient designs with the latest off-the-shelf technology, the teams aim to create homes that reduce utility bills and meet all their energy needs, while providing all the comforts of home.
The walls are made from vacuum-sealed panels constructed from the same material as recyclable plastic water bottles. It contains football-shaped cavities that are filled with water. In total the system holds 215 gallons of water (just over 2,000 pounds) and every cubic foot of water can hold 64 Btu's for every degree Fahrenheit of temperature change. This makes the system three times more efficient than concrete and it's also much lighter to ship because the water can be added at its destination. Plus, the team says living next to a water wall provide, "some really neat optical effects and lighting effects."
The wall is the brainchild of Eddie Hall, who cautions that, like many things in the experimental house, it is a prototype, but it has been refined after a year and a half of experimentation.
The modules are joined on the southern side, but the northern side is left open. The exterior is covered with Cor-Ten, a corrugated, steel cladding whose outer layer oxidizes to a weather-proof rusty coating that gives the Silo House its distinctive coloring. Solar heat absorbed by the Cor-Ten steel siding on the southwest side of the house is transferred to fluid running through copper pipes hidden underneath the corrugated steel skin. This preheats water entering the domestic hot water tank before the primary heating is done by an Apricus evacuated tube solar thermal system.
Acting together, these systems allow 15 gallons of hot water to be supplied to the showers in ten minutes with the 120-gallon tank able to store heat for days without sun. If the heating mechanism doesn't provide enough hot water, a backup electric resistance heater in the how water tank can finish the job.
Virginia Tech's Lumenhaus sports a single array of bifacial panels that capture energy on both sides to increase energy output by 15 percent. Using an electric actuator, the entire PV array can be tilted to the optimal angle for each season (from zero degrees to a 17-degree angle in summer and to a 35-degree angle in winter), to allow for maximum solar energy collection.
Even more impressive in its sun following capabilities though, is the Black ]
Anyone looking for a more in depth examination of all the entries can check out the Solar Decathlon website or, if you're in the neighborhood, get along to the competition site located at the National Mall in Washington, D.C., which is open for public tours. The houses are open to the public until October 13 and will be closed for competition monitoring on October 14, before reopening to the public from October 15 to 18.
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