University of Maryland students didn’t compete in the last Department of Energy Solar Decathlon, but that doesn’t mean they didn’t show up. Dozens of them carried clipboards and furiously scribbled notes while eyeballing solar-powered houses designed and built by other students from around the world.

They were preparing to vie for this year’s event, which started Thursday at West Potomac Park and runs through Oct. 2. U-Md. is unveiling ­WaterShed , a house inspired by the Chesapeake Bay ecosystem. Water from its sinks, shower and washer is captured, filtered and recycled to sustain a lush water garden that runs the length of the house. Solar tubes heat running water.

The school’s student architects and environmentalists spent two years dreaming up, designing and building a modern house that conserves water and reduces its utility bill to almost nothing.

“We’re ready for anything,” said Veronika Zhiteneva, a 20-year-old project manager. “It’ll be interesting to see who comes out on top.”

This year’s competition is expected to be fierce.

Team China’s Y-shaped house has moving walls and thermal tubes that heat floors in winter. A motion detector follows occupants in the California house, turning on the TV when they plop on a couch and switching off lights when they point. The New Zealand house gives residents the sense of being outdoors, and a sunlight beams through a skylight and onto a polished concrete dinner table that radiates solar heat.

Twenty teams from schools in Manhattan, Canada, Tennessee, Tidewater Virginia, Florida, Ohio, Massachusetts, Indiana, Belgium, Illinois and other points are also in it to win it. Some houses have been sold.

Empowerhouse, built by Parsons the New School for Design in Manhattan and the Stevens Institute of Technology, in Hoboken, N.J., will go to Habitat for Humanity, which donated it to a single mother in the District’s Deanwood section.

Emphasis on affordability

Solar energy development is a stated priority of the Obama administration. Last year, the president pledged to install solar panels on the White House, but this summer’s deadline was missed. In recent weeks, the administration drew controversy for providing millions of dollars in loan guarantees to a solar company that collapsed.

So the biennial decathlon is welcome news. It was started in 2002 by the Department of Energy to demonstrate that solar power can be practical and affordable, and to prepare students to work in the field. Judging on 10 individual contests that lead to the crowning of an overall winner started Thursday, said Richard King, the event’s director.

That affordable message was slightly diminished when a team from Germany won in 2009. Its house, smothered in solar panels, cost $800,000, King said.

“We’re stressing affordability this time,” he said. Points will be deducted if a house costs more than $250,000. Teams must show that six people can comfortably watch TV, play music and do basic chores.

“We will make them do a whole lot to prove that you can power your house and that you don’t have to sacrifice” your lifestyle, King said.

Grounds for new event site

Sacrifice is familiar to competitors at West Potomac Park, a location near the Arlington Memorial Bridge where most would rather not be. In January, the event was kicked off its more visible stage on the Mall, where it had been held four times over seven years.

The U.S. Park Service said the houses, dropped in place by huge cranes, destroyed the grounds. Although students paid for sod to replace damaged grass, the event left a messy field for the tens of thousands of people who visit America’s so-called front yard.

The Energy Department was not artful in delivering news that the event would be moved to the remote National Harbor in Prince George’s County: It made a conference call.

“It was a collective gasp,” said Reed Finlay, 33, project manager for the Compact Hyper Insulation Prototype house by the Southern California Institute of Architecture and the California Institute of Technology.

Students, who raise millions of dollars to fund the houses, ship them from as far as Shanghai and put up about 30 students per team for two weeks in a hotel, heard the news crackle over a loudspeaker.

“That was a shocker,” said Newton Gorrell, 27, a project manager seeking a master’s degree in architecture at U-Md.

After launching a campaign to stay on the Mall, decathletes were given space at West Potomac Park, where joggers dash between the Memorial Bridge and Georgetown and weekend warriors play softball and field hockey.

The area is not ideal. Framed by the river and the Tidal Basin, it’s a you’ve-got-to-be-kidding-me walk from the nearest Metro stations. The Energy Department arranged for free shuttle buses to pick up and drop off visitors at the Smithsonian station on the Blue and Orange lines.

The upside is that, to some, the West Potomac Park site, with the Potomac flowing by, is more scenic than the Mall. “It’s in our watershed,” Zhiteneva said.

Plenty of hard work

Visitors will see houses that are controlled by computer tablets and Microsoft’s Xbox 360 Kinect and adorned with plants native to their places of origin. They won’t see how hard students worked behind the scenes — 12-hour days spent designing and sawing houses into shape.

“They work their butts off,” said Amy Gardner, an associate professor of architecture at U-Md. who’s the lead investigator for the project. She said 200 students played a direct role in creating WaterShed.

The past overall winners in the four previous decathlons were split between the University of Colorado and Universitat Darmstadt in Germany. But U-Md. has a legacy to protect.

Its 2007 house placed second overall and won the People’s Choice Award. Thirty U-Md. students traveled daily from as far as Germantown to construct and decorate the house before Tuesday’s 7 p.m. completion deadline.

“I had no clue what I was getting into,” said Gorrell, who joined the project two years ago. But it’s worth it, he said. “I went to a meeting and . . . quickly found I was in over my head. It’s learn on the go and try to adjust.”