Canadian made, handcrafted piston fan runs off the heat of your woodstove. The secret of the Free Breeze fan is a small stirling engine housed in the square base of the unit. Stirling engines have been around for decades but no one has ever come up with a marketable way to use them. They consist of a sealed chamber that expands quickly when heated and contracts when it cools down. The heating up and cooling down happens almost instantly. The piston in the small engine drives an offset crank that drives the fan. The unit weighs about 15 lbs. and has a 14" diameter, 8-bladed fan. You just set the unit freely on top of a hot surface. Needs no batteries, fuel or electricity.