how to make electricity from temperture difference

One day I saw on Discovery a guy using a local stream to make electricity. really cool, he attached a light bulb to it and put that into layers of stone. by doing so, the stone heated and so he was able to cook on it.
Basically what I am asking is, how can you make electricity from the local stream by means of temperature difference with the air temperature.

Kiteman4 years ago
You're looking for a heat pump. They come in several forms, so start with that as your search, then refne things by your personal skills and budget.