Thanks for the responses. I have a few queries and things to clear up. I had a similar idea to Abstruce's about using refrigerants. The thing I don't get is how do you make "a collector to absorb heat from the atmosphere", wouldn't the collector just re-emit the heat into the atmosphere. I was thinking that one could put some water in a sealed container and then pump out enough air so that the boiling point of the water is around room temperature (or similarly use a refrigerant which boils at room temp. if such a refrigerant exists). Then what would happen (maybe) is that the water at the bottom of the container would evaporate, rising up the container to turn a turbine, condense at the top of the container and fall back down to complete the cycle. I think that the water would condense at the top of the container even if the top and bottom of the container are at the same temp. The reason is that as the water vapour rises, it gains potential energy and thus loses kinetic energy (i.e. the temperature of the water vapour drops) allowing the water vapour to condense and fall back down. Another thought that I had along the same lines is that if the container widens towards the top then the temperature of the water vapour would drop as it expands, making it easier to condensate. I had a look at the website that Kayra referred to. A powerchip is not what I was thinking of as it needs a temperature gradient to work (similar to thermoelectric converters). What I am ultimately asking is if electrical energy can be produced from the heat in a building, thus cooling the building and generating electricity. If, however, there is a natural temperature gradient in a building then it would be interesting to find out if powerchips and thermoelectric converters could be used to generate electricity. The only natural temperature gradient I can think of is the ceiling being hotter than the floor (because hot air rises and the roof of the building gets heated up by the sun). However, I imagine that this temperature difference is too small to be any use to a thermoelectric converter or a powerchip. In addition, I don't think that thermoelectric converters would solve my intial query as I don't think that they actually cool down the surroundings. They generate electricity from the transfer of heat from a hot source to a cold source. Just an additional question, is there any reason why a photovoltaic cell can't be tweaked to absorb Infrared Radiation (heat) instead of visible light, thus solving my initial query.
