Solar-tracking skylights are seen installed in the roof of hangar 2418 at Fort Eustis, Va., Nov. 18, 2013. The skylights save energy by using the sun as a power source to track its movement, which enables Soldiers to utilize only the illumination from the sun through the skylight as a source of lighting throughout the day. (U.S. Air Force photo by Staff Sgt. Ashley Hawkins/Released)