Renewable energy sources
A solar wall was installed on Hangar 210 on Peterson Air Force Base in 2007. The wall is made of ribbed panels that have small slits on them. Air is drawn in through the slits and the surface of the panels heats the air, which is then blown in through an air duct inside the hangar. To date, the project has saved $126,000 in utility costs. Solar walls are being considered for other buildings on base in an effort to increase renewable energy sources. (U.S. Air Force photo/Monica Mendoza)