First attempt would not run without ice on top. I wanted it to run without needing a cup (or cups) of HOT water for my son's science fair. This one is running atop a 12v automotive headlight bulb powered by two 18650 batteries acting as a "solar simulator". I cut the reflector out of the headlight and mounted it inside an glass candle jar to try to keep the heat contained and as close to the engine as possible. It'll run about 20 minutes or so before the light begins to dim and the engine slows. Should be good enough. If not he can change the batteries and keep on chuggin'.