Stirling engine
A Stirling engine can convert small differences in temperature into movement, and thus into for example electricity.
small homebuilt engines to show how it works using low diffrence in temprature.
http://www.youtube.com/watch?v=Qt5tthfk59U&feature=related
http://www.youtube.com/watch?v=0wnqjkazxsQ&feature=related
http://www.youtube.com/watch?v=vM0YmlRIYBI&feature=related
sterling engine running on a open flame:
http://www.youtube.com/watch?v=DKW83hId-6M&NR=1
http://www.youtube.com/watch?v=q7_1W799nkk&feature=related
Quad sterling engine running on open flame:
http://www.youtube.com/watch?v=uU6IstOVsew&feature=related
Bigger sterling engines:
http://www.youtube.com/watch?v=PIe3XeDWmGE&feature=related
http://www.youtube.com/watch?v=vsg6wfhgx-M&feature=related
solarpowerd sterling engine.
http://www.youtube.com/watch?v=1dTt2s6YwJ8 and http://www.youtube.com/watch?v=kYKOjnCwmG8&feature=related