Unlike other engines, a Stirling engine (like other external combustion engines) is more suited for using alternative power sources like solar energy. You can h

Unlike other engines, a Stirling engine (like other external combustion engines) is more suited for using alternative power sources like solar energy. You can heat the end using a Fresnel lens or a solar concentrator (http://en.wikipedia.org/wiki/Solar_power_in_Spain http://en.wikipedia.org/wiki/Solar_power_in_Spain). But more importantly, with a $100 price tag, it will be an affordable engine to experiment for hobbyists.