Solar decathlon competition comes to Washington

Physics Today : The next generation of energy efficient houses appeared in Washington this week as part of the Department of Energy’s 2009 solar decathlon competition ( pdf ).The competition, held on the Washington Mall, judged 20 homes based on aesthetics, functionality and energy measurements.The University of Minnesota’s 565 sq. ft solar home called ICON cost half a million dollars to build and came 5th in the competition.

Student’s have to design in factors such as is there enough solar thermal hot water for the big and small dishwashers in the kitchen and the clothes washer in a cabinet next to the small bathroom? Was the temperature in the house just right? What about the humidity? Exactly how much power would the appliances, along with the lights—mostly LEDs—draw from the photovoltaic cells that covered the roof and south-facing wall?

“We build [ICON] specifically for the Minnesota climate,” said Shona Mosites, a senior studying interior design at the University of Minnesota.

Like all of the houses in the competition, the Minnesota house is compact—about the size of a large house trailer. It is extremely energy efficient, producing more electricity during the day than it uses and feeding the excess into the regional power grid. At night, when the sun is down, the house draws from the grid, but less than it feeds into the system during the day.

And like all of the other houses, the ICON house makes extensive use of green materials.

“The sliding panels are made of recycled material, and the maple flooring is two-thirds reclaimed wood,” Mosites said.

A difficult road trip

At the other end of the Mall, the team from the University of Wisconsin-Milwaukee was struggling. The team was in last place, and were struggling to get the house’s sliding doors to move smoothly on their tracks. Their house, valued at $485,000, had tabletops made out of pressed paper and cashew shells and the ability to warm up just from the heat of the people inside.

But its last-place standing reflected a 3-inch problem in the design.

“The west end of the house was 3 inches too tall to go through Indiana [on the transport trailer],” said Eric Davis, the project’s chief engineer. “So we had to go down through Illinois, then cross Kentucky.”

There was another height regulation problem when they got to the edge of Washington, and it took another 20 hours to finally get their structure to the National Mall. While the other teams were fine tuning their home’s systems, the Wisconsin team was still wearing hard hats and putting their house together.

“We missed the metering contest, so our score is down,” Davis said.

The houses that make up the high-tech Solar Village are mostly from universities, shipped in multiple pieces from around the world. Germany, Spain and two teams from consortiums of Canadian universities also have entries in the competition. And the event is drawing crowds, with long lines of people waiting to tour the houses.

“About 2,000 people come through our house each day,” said Thomas Rauch, media liaison and team member of Penn State University’s Natural Fusion house.

The energy produced by these small structures, each limited to 800 square feet, powers all of the lighting, appliances and air conditioning within. And on sunny days, when the houses produce more electricity than is needed, they pump the extra energy directly into the regional electrical grid that powers the metro area.

The German team’s house often gives back twice as much energy as it uses—enough in one day to light 400 incandescent light bulbs for one hour.

Home improvement

US Secretary of Energy Steven Chu helped to kick-off the event on Oct 8 (see picture left. Chu is on the right. Photo credit: DOE) by describing his own home-improvement experiences while working to make his home more energy efficient. “I started doing this long before I knew about climate change. And I have to confess the only reason I was doing that is because I’m fundamentally cheap,” he said.

Chu said that during his time at Lawrence Berkeley National Laboratory in California he became convinced that houses could be made 75 or 80 percent more efficient in terms of energy usage—before adding any solar panels. He also announced an additional $87 million in DOE funding to further the solar research on display in the homes.

Several of the houses are smart phone-enabled—the interior lighting and temperature can be changed remotely with an iPhone application. Others adjust interior conditions automatically, using sensors that monitor time and weather data to tint electrochemical windows and dim light levels.