This low temperature Stirling engine is a cool little device. It’s a closed cycle engine, meaning that all the working gases that expand and make it work are contained inside the cylinder unlike combustion or steam engines that expel the gas after expanding. This efficient little engine runs on nothing more than a little bit of heat. Get the bottom plate a little warmer than the top one, set the flywheel in motion and it runs, keeping the flywheel turning as long as the temperature difference is …