English: Thermal image of a heat-powered fan, used to circulate the heat from a wood stove. The camera's sight is focused on the semi-conductor, which produces electricity to power the fan's motor. The upper inset shows a close-up of the semi-conductor. This area is the transitional zone, where thermal energy is first turned into positive work (electric current generation), and then into negative work, or "entropy" (heating of the cooling fins). The heat is then dispersed into the air, where it rejoins the heat from the wood stove to heat the house, returning it to a useful form of work, or "negative entropy." The lower inset shows the fan in visible light.