This is a hot-air machine (stirlingengine), built with some old computer-parts (heatsink and the head of an old harddisk). This Stirlingengine (and all others also) works with a temperature difference between the hot bottom side (e.g. heatet with a candle) and the colder topside (cooled with the hea...URL: http://www.instructables.com/id/Rotating-LED-throwies-driven-by-a-Stirlingengine-/