h a l f b a k e r y"Look on my works, ye Mighty, and despair!"
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How's it? Damn, I wish my formal training it heat transfer amounted to something, but I've scratched my head raw over this... :( |
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All I will say is that I have a super temp. gradient right now between the inside and outside of my apartment wall, but no turbines are spinning, dammit! |
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Build a wall around the area, to prevent air from carying heat into it. At night the ground will radiate heat, and in the day-time, being shielded from the sun, absorb much less then the surrounding sand. Therefore the area inside the wall will be significantly cooler then the area outside. There are many ways to use temperature differences to generate electricity. |
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I dunno. Using shade to generate a heat difference just doesn't really seem original to me. I mean, how does this really differ from a house and some big worded hand-waving? |
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[marked-for-deletion] where's the beef? |
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unmark me, you cretin! houses are not built to generate electricity! |
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[marked-for-tagline]: "unmark me, you cretin!" |
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Voice: desert houses *are* built to generate temperature differentials, and you really haven't said much about the actual electrical generation. |
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Has he said anything at all? except for some weak improbable driving force? But, I must collect my thought.... |
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please note the location of this idea, the last line, "Use the temperature difference to generate electricity efficiently.", and the fact that there are no other uses for this such as living in it. Then go play in traffic. |
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[Voice], dude, how does shady sand collect solar energy? |
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I played in traffic once. It's markedly as dangerous as you would think. |
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//cool below ambient// impossible. [marked-for-deletion] bad science. Sorry, but your sentiments make me critical. |
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Gumbob, I said that you can reliably and cheaply make one place colder then another, and that electricity can be generated. Do you understand now? |
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no, no, it is the good doctor Curry on whom I wish the death of a hundred wheels. The shady sand is cooler then the not shady sand. You can make a heat engine, run a turbine, or do something else to generate electricity from the difference. |
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This is frustrating. Tell us how to generate the electricity already! |
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EDIT: You beat me to it, it seems. |
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it is not bad science. A temperature difference can be generated. am I the only person here who knows how to use a difference in temperature to generate electricity!? I dont even have a degree for cryin out loud |
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Clearly not. [Voice] if you don't see complications in your logic, and are not willing to hash thru them, then what, may I ask, are your intentions? |
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A turbine will generate electricity based on air flow due to temperature differentials. My stand is this: your temperature differentials will exist, but will be negligible with respect to energy generation. |
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I believe a difference of ten or twenty degrees can be easily realised, and that the difference will generate enough electricity to make it worthwhile. That said, stranger things have happened then me being wrong. And use water, not air. |
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Another hamsterpower idea, this is. |
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but I didn't get to the best part! you have to coat the sand with custard to improve its albido |
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Ah. In that case, [marked-for-deletion] custard. |
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Wait, what??? Is there a chance we can mark this more as many deletions as ever recorded? I, for one, think it's a let's all, for it wouldn't be economical unless everyone did it. |
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A joke, Bob. One our friend Dr. Curry wasted no time in exploiting to his nerforous(sp?) ends. |
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George Bush! perpetual motion! spam, spam, spamity spam spam! Wouldn't it be nice! I saw it in a movie! Rant! advice, philosophy, theory, and racism! Rant, rant, rant! MARK ME FOR DELETION YOU SPINELESS BAKERS ASSISTANTS! |
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Shit.... he's still incoherent... |
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Thank god, he's thinking... |
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// The shaded area will cool below ambient // |
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So the next morning, the shaded area is fully cooled below ambient. Now when the sun comes up close those shutters again and the shaded area will stay below ambient. We can even lay a thermal blanket on it to make sure that it does. But at night we open the shutters again it will get even colder, now way below ambient. |
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After a couple of days it's going to be really f*cking cold in that shaded area and we can make liquid nitrogen which is then used to fill the boiler of a large steam locomotive and when the sun comes up and warms the boiler the train will start to move. It's a solar train! |
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Well, the train can be used in a number of ways to generate electricity. |
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So. Apart from the mud-slinging, the idea is: use solar energy to make one mass warm. Keep a second mass cool. Use the temperature difference to generate electricity (by unspecified mechanism). |
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Usual system for this kind of application is a Stirling engine (see link). |
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Being a newbie, I don't feel qualified to [MFD], and I'm too nice to anyway. So far. |
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And the anno's make me laugh - particularly "unmark me you cretin!" |
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//Use some automatic shutter system to shade a large patch of desert in the day-time. At night, open the shutters and allow heat to radiuate out.//
If the patch of desert has been shaded in the day-time, where does the heat come from? |
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////cool below ambient// impossible. [marked-for-deletion] bad science.// |
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In reallity this is in fact possible. see cosmic backround refrgeration link, i think there were links in there. If not google Radiation and you should find info. a 10 to 20 degree difference is possible but I dont think that you can generate any useful electricity from that. A stirling engine is inefficient at those temperature differentials. |
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It's a pity this idea has been chewed for
its poor presentation. I don't think it's a
good idea, but it's still interesting (to
me, anyway). |
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I think that the reason people don't
already do something like this is
that the energy generated is closely
related to the temperature *difference*.
When it's very easy to raise the higher
temperature
by several hundred degrees simply
by arranging a few mirrors, it's a waste
of time to
spend the same effort cooling the lower
end by just a few degrees. |
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If you could make usable energy
efficiently from small temperature
differentials, everyone would be
powering their house, day and night
from the temperature difference
between their swimming pool and a
stone surface next to
it. Those without swimming pools
would build them just to generate
power. |
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Well, here's what you do [voice] : figure out what the temperature difference is, then find out how much energy you can get running a Stirling engine on that temperature difference per square meter of sand. Don't forget to include transmission losses from the heat to the engine, and storage losses for trying to keep things cool / hot under the shutters during the day / night. |
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Next, compare the power you get with the amount of power necessary to open and close the giant insulating shutters. This is also a function of the alleged power generation area. If you get a negative number, well, the Commisar has loaded the delete button for you and left it on your desk. |
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hey, Halfbaked ideas don't have to be efficient, just look at the orbital toaster, that is the least efficient thing I can think of. Although [Voice] didn't word it well, and was as coherent as an inebriated monkey. |
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Don't be burning on the Orbital Toaster - I've got my late breakfast touching down in the parking lot in three minutes, and I have to go get the jam out of the refrigerator. |
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Which, I might add, has an automatic shutter system over it at night. Still can't get it to generate electricity, though. |
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I'm not burning the orbital toaster. I love the orbital toaster. |
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you might want to move your car out of the parking lot first |
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I saw a fan once that had two metal prongs at the end. You stuck one of the prongs in something cold and one in something hot and the fan turned on. IIRC, the temperature difference required was high and the energy generated was low. Thus, this idea probably wouldn't be cost effective...but the concepts behind it are valid. |
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//Use the temperature difference to generate electricity efficiently.//
It's not unworkable, but it isn't efficient as you claim. Efficiency is related to the temperature difference. Some real scientific type guy proved it a long time ago. Carnot? |
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Really? nobody mentioned a Peltier Junction? see the
link |
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The Seebeck rather than the Peltier effect is what you want if
you're looking for thermoelectric conversion. |
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Eldrin Carnot, in his famous equation, said that
the limit of efficiency for a heat-powered engine
is 1-(Th/Tc), where Th and Tc are the
temperatures on the hot and cold sides,
respectively. |
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Since we're talking Kelvin, a temperature
differential of 20°C (20K) will lead to a maximum
efficiency of something like 1-(290/310), or about
6%. Not unsignificant, though in reality I think
you'd struggle to get a tenth of that out as
electricity. |
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The same area of solar panels, on the other
hand... |
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[MB] Just put in what I was about to, that the
efficiency is dependent on the temperature ratio
in an absolute scale (kelvin or rankine, makes no
difference). That means that you're going to need
either a fairly high temperature differential or an
absurdly large area to justify the cost of any sort
of generator, let alone the cost of building and
maintaining the shade system. That being said, if
you put a large field of tracking solar panels in
place, maybe you could use the space under it for
this idea, with only the generator and heat
transfer systems as an add on cost. |
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Carnot efficiency is only relevant if there is something you'd rather be doing with the input work, land area, or resources utilized. |
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Anyone who's stood on a hot beach and then stuck their feet a few millimeters further into the sand can appreciate the temperature differential here. |
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