> -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Charlie Bell > > None, once it's out there. IIRC, it's a small wind turbine that cools > collectors in it, and desert air is often humid even if it doesn't > rain much.
If the collectors are cooled, there _has to be_ a source of energy that is being used. If not, then we've just found an exception to the 2nd law of thermodynamics. A useful statement of the 2nd law for our purposes is that "it is impossible to transfer heat from a cooler reservoir to a warmer one without adding work of some kind. The sites I read said that a wind turbine, solar cells, or thermal solar heaters could be used. All are sources of low entropy energy. Now, one might thing that a solar heater is an exception to the rule, but it isn't. With it, one has three reservoirs. Hot, medium, and cool. The hot is the solar heater water, the medium is the environment and the cool is the collectors. One can simultaneously transmit heat from the hot and cool to the medium, the ratio of which is determined by the laws of thermo. If need be, I can still work out the problem analytically, but it's been a while since I did the actually number crunching. :-) Speaking metaphorically, there has to be a waterwheel of some kind driving the mechanism that pulls things uphill. >Even a cold beer at 3C attracts a lot of condensation. This > is definitely a small scale solution for remote locations. And it took work, probably from an electric motor, to make that beer cold. Now, if you have a cold reservoir available, then the thermo is simple, but I don't think that's what's being talked about. It definitely looks like work is involved. I suppose I could figure it out, but with a wife recovering from a second knee operation, keeping house, and working full time, I probably won't do the problem just for the fun of it. But trust me, some external, low entropy source of energy is needed. A wind turbine would qualify. In essence, all we would need to know is what the output of the wind turbine is, what the water production is, and we'd have our answer. > > It reminded me of your discussion of > > how energy intensive desalination is. > > Yeah, but that's a different process. Fair enough, but I'm guessing you'll find that it takes a lot more energy per liter of water than you might think to pull the water out of the air. > But look at how much water comes > out as a by-product of airconditioning systems... And look at how big my electricity bill is to run it. :-) Dan M. _______________________________________________ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
