This guy made a very simple and awesome homemade stirling engine that is powered by a candle. A faster than any you have seen. A stirling engine actually operates by transferring air or gas from one side of the engine to the other, this is done by the displacer. This air then works upon the power piston which in turn rotates the crankshaft which moves the displacer and on and on it goes until a heat source runs out or the engine reaches equilibrium.
Well, he should have replaced the cd with some fan blades and you have a candle powered fan for hot summer days :-).