On the last two occasions, the overall winner of the U.S. Department of Energy Solar Decathlon has gone to Germany's Technische Universität Darmstadt but this year the top honor has stayed with one of the home teams. As the name might suggest, the University of Maryland's winning WaterShed project features some novel innovations to make the best use of water, in addition to an intriguing internal waterfall that helps reduce the load on the structure's air conditioning system. Read on for a brief look at the top five winning projects, as well as the People's Choice.

First started in 2002 and running every two years since 2005, the Solar Decathlon challenges student teams from all over the world to design, build and operate solar-powered houses that are cost-effective, energy-efficient and appealing to the eye. The overall winner of the competition is the team that, according to the official description, "best blends affordability, consumer appeal, and design excellence with optimal energy production and maximum efficiency."

This year's challenge saw 19 solar-powered houses being constructed in the Solar Village at the National Mall's West Potomac Park in Washington, D.C., seven of which managed to produce more energy than they consumed despite a mostly cloudy competition week. Some 4,000 student representatives from five countries took part and more than 357,000 tours around the homes were undertaken during the week of the competition.

There can, however, be only one overall winner and that honor went to Team WaterShed from the University of Maryland. In addition to a rooftop-mounted photovoltaic array, the winning structure also incorporates technologies aimed at more effectively managing water use - recycling greywater from washing machines and the bathroom and reusing collected rainwater. Another water-based feature is the liquid waterfall that absorbs moisture from the air into a high-saline solution to help reduce the load on the structure's air conditioners, and builds on technology developed by Maryland's 2007 Decathlon entrant, the LEAFHouse.

Designed as a home/office with sustainable living in mind, WaterShed features a small vegetable garden, vertical gardens with vine crops such as blackberry and grape, and a green roof on the south module covering 312 square feet. There's also a built-in home automation system that monitors and adjusts environmental systems.

The runners up

Only a few points behind Maryland, Purdue University's
INhome project looks like it might easily blend into any typical Midwestern neighborhood. Short for
Indiana home, INhome features a self-watering vertical wall of plants that helps clear the air of contaminants, a water heater that makes use of ambient air inside the house to produce hot water and passive air ventilation that combines manual and automated control.

Its interior has been designed to make use of recycled materials, there are 36 roof-mounted solar panels to help meet its own energy needs and a touch panel central control system for monitoring and tweaking environmental and security settings, with smartphone integration.

Coming in third is First Light from Team Victoria University of Wellington, New Zealand. This green home was inspired by the Kiwi bach or traditional New Zealand holiday home and is so named because New Zealand is the first place to greet the morning sun on each new day. A glazed central section and triple-glazed skylight allow natural light to flood into the house, there's a solar-heated drying cupboard and interactive energy monitoring system.

Being prefabricated and modular, First Light lends itself to easy transportation and installation, makes use of locally-sourced and certified green, as well as recycled, materials and was designed to use less than a third of the energy of a typical U.S. home.

Just missing the medal podium, Middlebury College's Self-Reliance project takes the best aspects of a New England farmhouse and combines them with some 21st Century energy-efficiency technologies. This two bedroom home features 11-inch thick insulated walls to help fend off Vermont's cold winter months, large south-facing triple-glazed windows with cork-insulated frames (with smaller windows to the north, east and west faces), a 30 panel solar array on the gable roof and a ventilation system that pulls in cooler air from the ground and expels warm air from skylights.

The last of the top five is Ohio State University's enCORE project. Built around centrally-located mechanical and plumbing systems, this family home for three benefits from triple-glazing throughout, a unique solar thermal hot air system, thin-film PV panels and a touchscreen monitoring and control interface. There's a sloped roof for water collection, which is then filtered by a bioremediation system.

The people have spoken

Solar Homestead from Team Appalachian State University grabbed the public's imagination, receiving over 92,000 votes to take the People's Choice award. This design features a large outdoor living space called The Great Porch that was inspired by the lifestyles of the early settlers, 42 bi-facial photovoltaic panels to provide energy and offer filtered daylight, a hot water system that uses phase-change materials to ensure that the temperature of the on-demand hot water remains constant and wall cavity insulation that also uses phase-change material to store heat during the day and release it at night.

With this year's entries having now been dismantled and returned to the various universities for further research or sold to recover some of the design and build costs, the organizers of the Solar Decathlon have already started preparations for the next competition in 2013. Student teams wanting to take part can apply online, and anyone wanting to find out what's happened to previous entries and where they're now located can visit the Where are they now? page.

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