CMU builds solar-powered house for Washington, D.C. Decathlon

In Germany, entire communities are made up of solar-powered homes. While the US has not as rapidly adopted solar houses, steps are being taken toward green energy use. From September 27 to October 4, the National Mall in Washington, D.C. will become a temporary solar village. The inaugural event, the Solar Decathlon, is sponsored by the US Department of Energy in an effort to demonstrate the practical uses of solar energy.

A team of Carnegie Mellon students is currently building a solar-powered house in the Donner Ditch. From walls filled with denim jeans to a plant-covered roof, the design features a number of techniques to increase energy efficiency and create a comfortable place to live.

The steel frame house has been taking shape over the summer, and was in the planning stages as early as October 2001. It will be able to support all of the standard amenities of a modern house, including a home business.

"Part of this competition is to show that every luxury of a normal house can be accommodated with solar energy," said Andy Lee, a fifth-year architecture student and chief architect of the house.

The Decathlon in Washington, D.C. will have about 12 students from the CMU house to re-assemble it and conduct tasks required for judging. Students will be asked to demonstrate certain capabilities of the house, such as cooking, showering, use of a home business, and powering a small electric vehicle. Each team will be using a Ford Th!nk, a small electrically powered cart.

Entries in the competition are expected to be able to independently sustain power for a week. The CMU house, named Resolution, contains an 850 amp-hour battery array, which is used to store excess energy from the solar panels, and later reclaim the energy when it is needed.

"You could pretty much run the entire house off the battery for a week," said Andy Lee.

When complete, Resolution will have a front porch with a balcony on the second floor. Most of the roof will be covered with solar panels, or photovoltaic arrays.

Resolution utilizes several technological innovations from the Robert L. Preger Intelligent Workplace (IW). The IW is an advanced workplace on top of Margaret Morrison Carnegie Hall that was designed to maximize work efficiency and worker comfort. The solar house uses the same raised floor system as the IW. The floors have panels with space below for running wires and utility lines. This helps to improve insulation because it allows the builders to avoid cutting holes in walls. Another technology that transferred over is the software control system. The house uses "Metasys," the software system used to control the environment in the IW.

There are two types of solar power systems. A stand-alone system is not connected to the city power grid and is completely dependent on generating its own power. An extended period of cloudy weather could deplete the batteries, leaving the house without any power. The other type of system is connected to the power grid and can buy or sell power.

"The whole concept behind a grid-connected photovoltaic system is that when you are producing more power than the house is consuming, you're selling it to the utility company. And when you're not producing any power, you're buying it from the utility company," said Stephen Lee, an architecture professor and an advisor to the team.

At the Solar Decathlon, the houses will be stand-alone systems because they cannot connect to the Washington, D.C. power grid. However, after the competition the CMU team plans to install the house into a Pittsburgh-area community such as East Liberty or Garfield. It would be connected to the grid so that power would not be lost during extended periods of cloudy weather. The house would be placed on a corner because it is designed to be situated at the corner of two intersecting streets.

In Germany, where grid connected solar-powered homes are common, houses fall into a class of low energy, zero energy, or plus energy. Low energy houses produce less energy than they buy, zero energy houses produce the same amount as they buy, and plus energy houses produce more energy than they buy. Plus energy houses actually make a profit by selling energy back to the utility company.

The German government signed an agreement in 2001 to phase out 19 of the country's nuclear power plants. As a result, Germany strongly promotes solar energy and subsidizes construction of solar houses.

The house will feature a bed of plants on a flat portion of the roof which will not contain solar panels. The dirt and plantings on the roof will help to absorb heat and will also soak up rain water instead of letting it simply run off into surrounding areas. This is in sync with the idea of being responsible for the water that falls on the footprint of a house. Traditional houses simply let water run off into surrounding lands which can contribute to flooding and erosion.

The green roof also is beneficial because it absorbs heat from the sun. Many cities have "heat islands" - areas that heat up by several degrees due to houses with black roofs. The green roof can help eliminate this heat elevation in cities, explained Stephen Lee.

Resolution includes a loft bedroom, which will make the house taller than the contest's height limit. The designers of the project felt that it was important to design a house that would fit in an urban environment. "We have a commitment to the urban model," said Andy Lee. Though the team may be penalized slightly for the extra height, they feel they will do very well in the livability ratings of the competition.

Construction of the house is running behind schedule, however. Several teams, including Virginia Tech, have already completed construction and testing of their house. Stephen Lee said that it will not be a problem completing the house in time, but there will be less time for testing. He is working to recruit CMU alumni in Washington, D.C. to assist with the move-in.

For some of the architecture, design, and mechanical engineering students working on the house, past courses have helped prepare for this project. A course in the architecture department, titled Zero Energy House, taught the principles of running a house that produces as much energy as it uses, leaving a net energy input of zero.

Another course offered in the School of Architecture, Powering the Campus of the Future, studies power generation on college campuses, including fuel cell technology.

Students working on the project explained that the project is a good experience because everything they learn in the classroom, they get to apply to the house. They also learn plenty of new things. "They don't teach how to hang a door in studio," said Ryan Stahlman, a senior architecture student.