Harnessing the power of the sun is nothing new in the energy-saving world. For decades, green buildings and homes have employed solar panels to convert the sun’s rays into usable electricity. But in the dead of winter, when temperatures are low, the sun can provide buildings with more than just electricity; it can provide heat as well. Solar heating is a smart way to get through the colder months sustainably, and one company — in cooperation with the U.S. Department of Energy — has invented a solar heating system that is simple and efficient.
Transpired air collectors are an innovative solution to high heating costs. The transpired air collector technology, marketed as SolarWall, was invented by Conserval Engineering Inc., a solar heating and energy conservation company, which worked in partnership with the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL).
The principle behind the SolarWall air heating technology is relatively straightforward, and it produces a big payoff. The company installs a dark-colored façade, which acts as a heat absorber, on a building’s south-facing wall, leaving a space between the original wall and new façade for airflow. The exterior façade of the SolarWall system is made up of tiny micro-perforations that allow air to flow into the wall cavity. This air is pulled up and into the building by a fan, and as the air rises, it’s heated by the warm wall. Warmed air enters the building through a connection to the HVAC intake. (View an animation of how SolarWall technology works.)
Fresh air entering the building after being warmed by SolarWall technology will require less additional energy from a building’s existing heater. Victoria Hollick, a SolarWall representative, says transpired air collector systems generally save customers between 10 to 50 percent of heating costs. Savings depend on a building’s orientation, the size of the SolarWall collector, the length of the heating season, the volume of air to be heated and the color of the wall.
Solar heating systems that use glazed panels are a popular option as well (read Build a Simple Solar Heater), but the simplicity of transpired air collector systems makes them easy to maintain and affordable.
Transpired air collectors can be used for residential, commercial and industrial buildings. SolarWall systems are currently used in 33 countries, and you may recognize some of the big names already employing this technology: the United States Military, FedEx and KFC/Taco Bell, to name a few.
For every 5 square meters of SolarWall panels installed, about 1 ton of carbon dioxide emissions is displaced each year. Transpired air collectors aren’t just an environmentally sound option, though; they’re an economical choice, too. Customers generally see a complete payoff on their SolarWall investment in three to 12 years, according to SolarWall’s website. In the United States, commercial and industrial clients are eligible for a 30 percent federal tax credit.
Solar air heating is a great way to earn LEED (Leadership in Energy and Environmental Design) points, too. LEED points and certification are given to buildings that are built and function sustainably. SolarWall clients have earned as many as six LEED points for their transpired air collector systems alone.
Wondering whether your building is a candidate for transpired air collectors? According to SolarWall, certain factors contribute to ideal usage and savings:
- Buildings that have a south-, southeast- or southwest-facing wall on which the system can be installed are ideal. However, Conserval’s new product, SolarDuct, is similar to the SolarWall system, but has been designed for rooftop installation.
- Although they do provide some cooling benefits, transpired air collectors are most beneficial to clients in areas with longer heating seasons. Systems are being used successfully in warmer climates, though, such as Arizona, California and South Carolina.
- Clients with large ventilation requirements who have high utility rates for heating will see the fastest return on investment.
According to NREL, “Thirteen percent of the energy used in the United States goes to heating residential and commercial buildings.” SolarWall’s new technology is working to chip away at that number in a simple, stylish way.
Lindsey Siegele is the Senior Web Editor at Ogden Publications, the parent company of MOTHER EARTH NEWS. Find her on Google+.