Linux tricks for those who don't want to learn to kernel hack. Have you ever wondered about whether or not there are external combustion engines? Maybe it's just me. In case that's not the case, here, here, here, here, and here. Here, here, here, here, here, and here are some more links about the stirling engine, which basically runs off of any external source of heat or cold. Temperature differential, in other words. Interesting...I can think of several untapped sources of heat around.