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The Distance From Texas to Germany Shrinks to Net-Zero in NexusHaus

Tuesday, February 10, 2015

The 5,500-mile distance from Austin, Texas, to Munich, Germany, melts away with NexusHaus, a U.S. Department of Energy Solar Decathlon 2015 project that combines students from the United States and Europe.

Decathletes from the University of Texas at Austin and Technische Universitaet Muenchen in Germany have drawn upon shared interests—especially the energy-water nexus of sustainable practices—to create an ultra-efficient solar house. The only slight disagreement came over the title of the project.

“That name [NexusHaus—spelled the German way] actually came from the Austin side of the team, but some of the TUM [Technische Universitaet Muenchen] team thought it might sound a little too much like clichéd German,” laughs Charles Upshaw, a University of Texas mechanical engineering doctorate student and team co-captain. “Now that we’ve all agreed on it, we’re feeling pretty good about the name.”

Alt: Photo of a group of people with a giant balloon behind them.

Members of the University of Texas at Austin and Technische Universitaet Muenchen Solar Decathlon 2015 team enjoy activities at the Orange County Great Park in January. (Credit: Carol Laurie/U.S Department of Energy Solar Decathlon)

It helps that Austin and Munich share cultural bonds. A wave of immigration around Austin gave the region German roots. These days, residents of both Austin and Munich enjoy outdoor beer gardens and relaxing in public spaces.

There are technological parallels as well. Germany’s electric system is rapidly moving away from fossil fuels and toward renewables such as solar energy and wind power, while Texas is a leader in developing wind energy. Both grapple with integrating intermittent renewable power into electricity grids, and both are increasingly aware of the need to conserve resources such as water.

Wolfgang Vidal, a Technische Universitaet Muenchen student, says he became involved in the Solar Decathlon project because he shares a sense of responsibility for the global environment and wants to support “sustainable ways of designing and building and thus contribute to finding solutions for environmental issues.”

Upshaw says the house’s name encompasses what the team is trying to address—a nexus of four interrelated elements: energy, water, population growth, and sustainable food production.

“The idea is to build a house that is water self-sufficient, is net-zero energy, and has thermal storage,” Upshaw says.

Computer-generated illustration of a modern house.

NexusHaus is designed to increase the housing density in Austin without increasing the burden on water and electricity. (Courtesy of the Solar Decathlon 2015 University of Texas at Austin and Technische Universitaet Muenchen team)

Integrating solutions is the challenge, which was part of the learning process.

“We are an interdisciplinary team composed of many different nationalities,” says Technische Universitaet Muenchen’s Kristina Groendahl. “That gives us as a richer team when it comes to work methods, approaches, experiences, discussions, and solutions.”

Not everything goes smoothly at first.

“There are differences in design aesthetics, but those are helping drive our house design to something unique,” Upshaw says. “Otherwise, it wouldn’t be as creative as it is.”

The European preference for clean architectural lines, big windows, and sustainable materials is evident in the 784-ft2 modular urban home.

Eneida Lila, one of the Technische Universitaet Muenchen’s student leaders, explains: “Our design is composed of two equal-sized modules, with a clean division between day and night usage. These two house components come together through a central space, which we also call ‘nexus’ or the breezeway. It is an outdoor-indoor space which we integrate in our architectural and energy concept.”

The compact size is crucial because the team envisions the house as a prototype for “accessory” housing, such as a second house on a residential lot. Within Austin city limits, where the house will likely end up, this type of house could be installed on about 40,000 lots. To address the varied and unique challenges that come with building a new structure on an already developed property, modularity and flexibility are central design themes.

“The point is to increase the housing density in Austin without increasing the burden on water and electricity,” Upshaw says. “This could help with the population boom.”

In Austin, and across Texas, there’s constant pressure from growth.

“Population is projected to increase by 80%, while water supplies will decrease by 10%,” says Upshaw, an Austin native. Upshaw also says that Austin’s reservoirs have only been about a third full for several years because of drought conditions.

To help conserve water, NexusHaus uses its modular multipurpose canopy to collect rainwater and direct it to the under-deck storage system. It is also designed to recycle greywater—defined in Texas as water from showers, bathroom sinks, and washing machines—to support outdoor urban farming. The team will pump greywater for vegetables such as tomatoes and okra, and an aquaponic system will support fish such as tilapia and water plants in a symbiotic system.

“There’s a strong urban farming movement in Austin, and this would be part of that,” Upshaw says.

Technische Universitaet Muenchen students will head to Austin this spring to help with construction. The group will benefit from advice from University of Texas at Austin veteran decathletes. The school has participated in three previous U.S. Department of Energy Solar Decathlons—including the inaugural event in 2002.

“We’ll try to leverage as much knowledge as possible,” Upshaw says.

As the team gets down to the serious work of building NexusHaus, the Europeans and Americans will probably also find time to relax in Austin, aware that two cultures—so many miles apart—can come together in a single place, in a single project, as one group and, as Vidal says, “can laugh about everything.”

Ernie Tucker is a member of the U.S. Department of Energy Solar Decathlon communications team.



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