The EcoFan is a heat-powered fan that circulates heat from a wood stove into a room. The fan generates it’s own energy to power the fan by using the difference in temperature experienced by the fan at the top and bottom. The fan is almost completely silent, and will automatically circulate air when the stove heats up.
The fans have a small thermoelectric module which acts as a small generator to power the fan’s motor. When the module experiences a difference in temperature, it generates electricity. The fan will help circulate heat from the wood stove into a room, reducing the heat wasted up the chimney or into the back wall.
It doesn’t need any batteries, and is almost completely automatic to operate. You just need to be careful of over-heating the unit, which happens at around 350 degrees Celsius.
More technical information is available directly from EcoFan.