Hot Air Balloons

Hot air balloons are incredible machines that capture a tremendous amount of energy into one big bubble. The balloons use propane to heat the air over 200 degrees before blowing it into the balloon. With a capacity of 7-10 million btu's, the burners are 30-40 times the capacity of a typical home furnace. These images from last weekends balloon festival show the visible light image alongside an image taken with a thermal camera.
note: the green-yellow blobs below the balloons are people.

Duluth Balloon Fest 2014