Some years ago I builded a robot. It was able to avoid ostacle, it was funny and it had a lot of drive strategy (ABS for example) but after few minutes battery died. So I decided to build a THERMOELECTRIC GENERATOR unit. This is a electric generator, it is small (90x30x50 mm) and capable to generate 5W powr (5V 1A) with alchool burner or a small candle. It costed 25Euro (about 25$) and it is using a Peltier cell (50W) and very simple and fast to build (1 hour). The only prolem is temperature, after few minutes it becam hot, so it needs a fresh position (top of robot). I think it is a funny alternative to solar cells. Email: thomas.mazzi@virgilio.it