Half a croissant, on a plate, with a sign in front of it saying '50c'
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Evaporative Generator

Water evoporates, make stuff cooler than ambenint, and a thermocoulple
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When water (ect.) evaporates, it cools both the surface and the air. Thermocouples use temperature differences to generate electricity (cool and ambient).

Details: there are 2 possible configurations (that I can think of): Big, flat, thermocouple (one side covered with MOIST cloth, one covered with (optional) radiators (spikes, metal "fur"?)

Swamp cooler configuration- cool air inside (with radiators) warm air outside (radiators). Fan *needed*.

Cloth should be thin, could even be paper! Mostly for western USA, Sahara,... use (evaporative cooling works best in dry climates)

my-nep, Dec 03 2003

How thermocouples work http://www.nphheate...l/thermo_letter.htm
[SystemAdmin, Oct 04 2004, last modified Oct 06 2004]

[link]






       Um, Worldgineer, how do you think thermocouples measure temperature...? Don't be dumber than the idea you're criticizing.
my-nep: given that thermocouples generate only mV of DC electricity, and you've got all that sunlight in the desert, this device really doesn't cut it against, say, an array of solar panels.
DrCurry, Dec 03 2003
  

       California has arrays of windmills to help suppliment the solar panels too ... if, for some reason the sun wasn't cutting it.
Letsbuildafort, Dec 03 2003
  

       Hey [my-nep]   

       The problem with this idea is that, although you need a temperature differential to generate power, you need a fairly large differential to make it worthwhile.   

       In your example we may be able to generate a 20C differential which (correct me if I’m wrong someone) works out to about 5% theoretical maximum efficiency. Out of that 5% efficiency, a thermocouple is about 5% efficient (perhaps newer ones are better). That means you only extract 5% of 5% of the energy available. Considering the cost to build a thermocouple, it may not be worth it.   

       Much cheaper to build for the energy returned would be a solar concentrator. There are many example of these worldwide.
TIB, Dec 03 2003
  

       Now I really wonder what [World] had to say, so I could chortle tee-hee that it got called dumb. Oh well.   

       I am trying to think of a situation where the thermocouple generator would have any advantages. The only one I can think of would be a station at a "black smoker" deep sea vent - you have adjacent very hot and very cold temperatures to tap, and if I recall, thermocouples have no moving parts which would be a plus for undersea saltwater operation. If thermocouples are actually crammed with gears and gewgaws, [Curry] can put me in my place.
bungston, Dec 03 2003
  

       Don't talk to me - I'm busy hiding my head in the sand from saying somthing like "Thermocouples don't generate electicity, they measure temperature".
Worldgineer, Dec 03 2003
  

       [bungston]: I was going to use that exact example!! I suppose the problem would be the destruction of a unique habitat.
TIB, Dec 03 2003
  

       You wouldn't need to destroy anything. You would just position your generator over one smokehole (OK, it might be a bit rough on it). But then you could power your research station without cumbersome cables etc and study the rest of what is down there.
bungston, Dec 03 2003
  

       Could work, if can get the price of thermo-couples down and make them from environmentally safe material.
kbecker, Dec 03 2003
  

       I thought thermocouples changed resistivity with temperature. Oh, wait, that's a thermistor.
Detly, Dec 03 2003
  

       I belive you CAN make them from copper and steel. ( not sure )
my-nep, Dec 04 2003
  

       [World]   

       Thermocouples measure temperature by measureing the slight electrical current between two different metals when one is heated with respect to the other.   

       So it's true that thermocouples measure temperature but they also generate small currents to do that.   

       **see link**
SystemAdmin, Dec 04 2003
  

       Yes, thank you.
Worldgineer, Dec 04 2003
  
      
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