Inside solar house No. 101, engineering student Jenny Nickel is already thinking about how to add more alternative-energy features once the smartly modern house she helped build gets trucked out of Denver.

If you go: Solar Decathlon 2017 What to expect : Student-led tours of 11 solar houses, free workshops and Sustainability Expo

: Student-led tours of 11 solar houses, free workshops and Sustainability Expo When : Daily through Oct. 15

: Daily through Oct. 15 Hours : 11 a.m. to 7 p.m. except Monday when hours are 1 p.m. to 7 p.m. Closed to the public on Tuesday and Wednesday.

: 11 a.m. to 7 p.m. except Monday when hours are 1 p.m. to 7 p.m. Closed to the public on Tuesday and Wednesday. Where : Next to Peña Station Next, at 6045 N. Richfield St. in Denver (A line RTD stop at 61st & Peña Station)

: Next to Peña Station Next, at 6045 N. Richfield St. in Denver (A line RTD stop at 61st & Peña Station) Parking : Some free parking or park in solar-covered lot for $2

: Some free parking or park in solar-covered lot for $2 Cost : Free

: Free More info: www.SolarDecathlon.gov

The house, which Missouri University of Science and Technology students assembled in about 10 days in a muddy field south of Denver International Airport, already runs on solar power. Solar feeds six batteries that can power the 1,000-square-foot home for more than a day. But Nickel and her teammates can’t stop considering more options — they’re big geeks when it comes to sustainability.

“We’re adding a new microgrid up there. I think we’re going to put some wind turbines up there,” said Nickel, an undergrad who lives in her school’s 2015 solar house, pointing upward. “We don’t get class credit. We don’t get paid. This is purely student volunteers who are passionate about sustainability and trying to get solar power and renewable energy out there.”

Nickel’s team is one of 11 in this year’s U.S. Department of Energy Solar Decathlon, a student competition to demonstrate the latest innovations in solar energy, to highlight building and architecture designs, and to offer practical examples of sustainability.

For the first time since its 2002 debut, the competition is in Denver at the future Peña Station Next smart-city site. It has been held only in coastal cities until this year, and it typically draws anywhere from 40,000 to 100,000 visitors. The free event runs Thursday through Oct. 15. Tours of the 11 solar houses will be given daily, except Tuesday and Wednesday to allow for judging. The solar village has parking, but visitors also can ride commuter rail to the Peña Station stop.

“We’re from the Office of Energy Efficiency and Renewable Energy, so we love all renewable energy,” said Linda Silverman, director of the Solar Decathlon. “If you think about how much energy innovation has happened since 2000 when this started, there were almost no solar installations and almost no energy renewables. You can almost map the innovation of renewable energy and energy efficiency with this. It’s been growing leaps and bounds.”

According to the Solar Energy Industries Association, solar energy use is booming, growing at an average annual rate of 68 percent over the past decade. Some of the growth is attributed to the 2006 Solar Investment Tax Credit, which allowed taxpayers to get a 30 percent credit on a solar-energy system. Panel prices have also come down while reliability has gone up.

“I think the main thing that caused growth is the cost of panels has come down so much, about 65 percent in five years. It’s competitive with many other energy sources in other parts of the country,” said association spokesman Dan Whitten. “It comes down to economics. It’s the scale we’ve achieved. There are some places where policies have driven wider solar adoption, but last year for the first time, solar was the largest source of new electricity capacity in the country.”

The industry is bracing for price hikes that could occur if President Donald Trump decides to impose new tariffs on foreign solar products.

The push behind the Solar Decathlon was Richard King, who was working for the Department of Energy in the 1990s. King got the Clinton administration’s blessing in 1999, and the first event was held in Washington, D.C., in 2002.

“Oh, yeah, you can’t forget the first year,” said King, who retired after the 2015 event. “Here’s this crazy guy who wants you to build a house and bring it to Washington, D.C. I was twisting arms and finally got the dean of the University of Virginia interested. He said, ‘Oh, I know all the other deans. Here, let me help you,’ because he really thought it was a good idea. We got 14 teams that first time. Only one didn’t show. It was a smashing success.”

Still, not everything worked in the early years. King said about half the houses couldn’t get their solar water heaters to warm up the water. (“That’s a lot harder to do in the house than putting up a (photovoltaic) module and sticking two wires in your circuit breaker,” he said.) It just needed some time, and students learned from one another and improved on their homes.

“After the first four events, just about everyone had the performance down. We have de-emphasized it because everyone can do that now and it’s really good,” King said. “It’s become more and more a beauty contest.”

The 11 houses in the Denver competition have a very modern look with features that have more to do with sustainability than solar energy. The Swiss team, with students from four Swiss universities, has a green roof, aquaponics for breeding fish and a “dry” toilet that needs no water but uses worms to treat and recycle waste.

Wood trim on University of California at Davis’ Our H2Ouse came from trees that died in California’s drought. The side deck has an awning made of bicycle spokes and frames. Two muddied bamboo bikes from Boo Bicycles rest near the front door.

At the RISE house — a joint project by University of Denver and University of California at Berkeley students — a massive deck that is the same size as the house is meant to support communal living. The two bedrooms have walls that slide to open up the main living space for larger gatherings. A living wall of moss was growing quite nicely, thanks to the recent rain in Denver.

“It’s low maintenance and very, very resilient. It can survive winters in Chicago. That’s a testament of how it would be good for a lot of different climates,” Sam Durkin, student president of the Berkeley team, said of the moss wall provided by Moss Acres in Pennsylvania. “And it’s good for people because they don’t have to worry about it too much.”

The main event consists of 10 competitions involving architecture, market potential, engineering, and, this year, smart water solutions and innovation. Each team receives $100,000, with category winners getting more.

For the competition, the houses are being monitored and judged on energy use — preferably net-zero because they should provide about as much energy as they take from the grid. Team members, who will be active in the houses during the day but sleep elsewhere, also have to market their houses with signs to help inform visitors of the technology inside and what’s so great about it.

“They’ve got to cook meals, wash clothes, have the TV and lights on,” said King, who is volunteering as an observer at this year’s event. “We force them to do everything a family of six would have to do on a day-to-day basis, like drive around in the car, keep the refrigerator going, the lights on, the home theater. An observer’s job is to make sure they do these things and don’t cheat.”