how to make electricity from temperture difference

Hi,
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.
TXS!!!

Kiteman4 years ago
Ah.

Try peltier instead.
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.