Going Off The Grid: Competition Spurs Innovations in Solar Home Design

Imagine an energy efficient  house that's a blueprint for the  future, but exists today.  That’s exactly what 60 architectural and engineering students from the Missouri University of Science and Technology (Missouri S&T) designed and built. Their Chameleon House is a 1,000-square-foot home powered entirely by the sun.

The Chameleon House is the Missouri S&T entry in the 2013 Solar Decathlon, a worldwide competition that challenges university students to build state-of-the-art solar-powered homes. The contest is intended to encourage the development of home designs and technologies that are energy efficient, economical, and attractive. This year, 19 university teams are competing to make use of energy-saving technologies that are readily available in the marketplace, although these technologies are integrated in a variety of innovative combinations in each solar home.

The Missouri S&T students spent nearly two years designing the Chameleon House. They chose the name because their home adapts to changing features with a modern, adjustable, open-space interior and a “live” web-based automation system that updates the home’s heating and cooling settings with the changing weather.

While most conventional homes get their power from the burning of fossil fuels, solar homes like the Chameleon House use clean, renewable energy from the sun, which reduces the cost to the environment and energy bills for residents. Thanks to a unique solar array and a thoughtful design plan that packs energy savings into every square inch, the Chameleon House is able to generate enough energy to operate the home off the public utility grid with power to spare.

QUEST went behind the scenes to show how Missouri S&T students infused the Chameleon House with the energy-saving technologies.

The Frame: Support from SIPs

Conventional homes are constructed from dimensional lumber or “studs,” padded with pre-cut panels of fiberglass, rock wool, or cellulose insulation. But the frame of the Chameleon Home is different. It's built with high-tech prefabricated walls called structural insulated panels (SIPs).

Each SIP looks a bit like a marshmallow sandwich, according to Aaron Enz, the director of construction for the Chameleon House. A SIP is made from two pieces of oriented strand board (OSB), engineered sheets of wood made from glued layers of wood chips, separated by a dense layer of polystyrene foam in the middle. “[T]he reason that these are so good at thermally insulating the house is because there’s no wooden beams that go from this piece of plywood to the other,” said Enz. And even though the foam panels look delicate, their structure is strong, like a steel I-beam. Enz added, “They may not look like it, but they’re designed to be sturdy [enough] to withstand earthquakes.”

A study by the Oak Ridge National Laboratory confirms that SIPs are nearly airtight insulators that are 15 times better at stopping air leakage than conventional home frame construction. The study also found SIPs to be 40 to 50 percent more energy efficient than conventional stud walls, and so can keep a house warmer in the winter and cooler in the summer.

The Solar Array

To power the Chameleon House, the Missouri S&T team covered and wired the roof with 21 unique solar panel modules called redundant array integrated solar (RAIS) modules. Traditional solar modules have individual crystalline silicon cells wired together in series, like a single strand of Christmas tree lights. When one cell stops working or underperforms, the whole module is affected and may fail. But RAIS cells and modules are wired in parallel, with multiple contacts between the circuit’s beginning and end. That means if one module fails or underperforms, the rest of the modules continues to operate and generate electricity.

Solar panels work by converting sunlight into electricity. Each panel contains multiple silicon solar cells topped with metal-wire conductor strips. When the sun’s rays hit the silicon cells, they excite the silicon electrons and cause them to generate a direct electrical current (DC) like a mini generator. Inverter devices within the array convert the DC into alternating current (AC) to power appliances, lights, and other home devices.

The Chameleon House solar array has an additional feature not found in standard solar panels. Each RAIS module looks like a small A-frame and is backed by a reflector that increases its solar collection.

Charles Wright, who leads the Chameleon House electrical team, explained, “The solar array consists of 21 panels that total 8.6 kilowatts. Then on the front of the house, we’ll have an overhang with a bifacial panel (panels that collect light from the top and bottom), and it’ll generate 1.9 kilowatts. So, we’ll have a total of 10.5 kilowatts on the house. Basically, the house will be net zero, and that means it will produce as much electricity as it uses over a year’s period of time.”

As a general rule, solar panels produce electricity during the five sunniest hours of the day. So, the Chameleon House will produce 52.5 kilowatt hours per day or 1,500 kilowatt hours per month. According to the U.S Energy Information Administration, conventional American homes use an average of 940 to 1,348 kilowatt hours per month.

Project manager Emily Vandivert is proud of the Chameleon House’s free energy output. “You’re gaining free energy from the sun, other than the cost of the actual panels. It makes sense to use the sun’s power because we are able to harvest that power and transport it into actual energy,” she stated.

Heating and Cooling: A "Live" Automation System

The Chameleon House boasts a unique smart home feature: an automation system that optimizes the home’s total energy efficiency. The system combines a smart thermostat with a Web-based interface that monitors changing weather conditions in real time and tracks interior climate conditions.

The home automation system not only regulates the heating and cooling system’s thermostat, explained team leader Austin Murdock, “It also can open and close automated shades to gain heat from sunlight or open windows to let out extra heat instead of using the air-conditioning unit in the house.”

The automation system operates from a built-in computer in the home's mechanical room, and it can be monitored or updated with a Web-based tablet or smart phone. As the computer monitors “live" updates of changing weather conditions via the Web, the automation system makes small changes to the heating and cooling systems within the house. These small automated changes reduce the home's power consumption, saving heating and cooling costs compared to manual changes made to suit a person’s comfort level.

The  Competition

Just as the Chameleon House took final shape - after five months of construction - a day of reckoning arrived.  The Chameleon House had to be taken apart in three sections and shipped by truck to Irvine, CA in order to compete in the Solar Decathlon.  After a five-day trek across the country, the Missouri S&T students had just nine days to reassemble the home.

The Chameleon House premiered to the public at the Solar Decathlon in Irvine, California, in October. The international competition included nearly 4,000 university students from the U.S., Canada, Austria and the Czech Republic. More than 64,000 people visited the 19 solar homes. For more information about the Chameleon House and to learn about the other Solar Decathlon homes, visit www.solardecathlon.gov.