Half a croissant, on a plate, with a sign in front of it saying '50c'
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temperature difference generator

Generate energy by cooling a patch of sand
  (+4, -9)(+4, -9)
(+4, -9)
  [vote for,

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. The shaded area will cool below ambient. Use the temperature difference to generate electricity. <edit:inefficient>
Voice, Aug 16 2006

Cosmic Background Refrigeration Cosmic_20Background_20Refrigeration
The desert is hot, but space is c-c-c-cold. [Voice, Aug 16 2006]

Solar Stirling Engines http://www.sunpower.com/index.php?pg=6
commercially available solar-powered heat engine systems [Frankx, Aug 17 2006]

Making power from heat differentials http://en.wikipedia...oelectric_generator
I thought this was self evident (did I miss something?) [Brian the Painter, Jan 06 2013]


       How's it? Damn, I wish my formal training it heat transfer amounted to something, but I've scratched my head raw over this... :(   

       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!
daseva, Aug 16 2006

       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.
Voice, Aug 17 2006

       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?   

       [marked-for-deletion] where's the beef?
DrCurry, Aug 17 2006

       unmark me, you cretin! houses are not built to generate electricity!
Voice, Aug 17 2006

       [marked-for-tagline]: "unmark me, you cretin!"
methinksnot, Aug 17 2006

       Voice: desert houses *are* built to generate temperature differentials, and you really haven't said much about the actual electrical generation.
DrCurry, Aug 17 2006

       Has he said anything at all? except for some weak improbable driving force? But, I must collect my thought....
daseva, Aug 17 2006

       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.
Voice, Aug 17 2006

       [Voice], dude, how does shady sand collect solar energy?   

       I played in traffic once. It's markedly as dangerous as you would think.   

       //cool below ambient// impossible. [marked-for-deletion] bad science. Sorry, but your sentiments make me critical.
daseva, Aug 17 2006

       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?
Voice, Aug 17 2006

       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.
Voice, Aug 17 2006

       This is frustrating. Tell us how to generate the electricity already!   

       EDIT: You beat me to it, it seems.
Texticle, Aug 17 2006

       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
Voice, Aug 17 2006

       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?   

       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.
daseva, Aug 17 2006

       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.
Voice, Aug 17 2006

       Another hamsterpower idea, this is.
Texticle, Aug 17 2006

       but I didn't get to the best part! you have to coat the sand with custard to improve its albido
Voice, Aug 17 2006

       Ah. In that case, [marked-for-deletion] custard.
DrCurry, Aug 17 2006

       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.
daseva, Aug 17 2006

       A joke, Bob. One our friend Dr. Curry wasted no time in exploiting to his nerforous(sp?) ends.
Voice, Aug 17 2006

       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!   

       Edit: I'm okay now
Voice, Aug 17 2006

       Clear! <BOOM>   

       Shit.... he's still incoherent...   

       Clear! <BOOM>   

       Thank god, he's thinking...
daseva, Aug 17 2006

       I like this idea.   

       // The shaded area will cool below ambient //   

       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.   

       Repeat this process.   

       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!   

       Well, the train can be used in a number of ways to generate electricity.
jmvw, Aug 17 2006

       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).   

       Usual system for this kind of application is a Stirling engine (see link).   

       Being a newbie, I don't feel qualified to [MFD], and I'm too nice to anyway. So far.   

       And the anno's make me laugh - particularly "unmark me you cretin!"
Frankx, Aug 17 2006

       //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?
angel, Aug 17 2006


       ////cool below ambient// impossible. [marked-for-deletion] bad science.//   

       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.
jhomrighaus, Aug 17 2006

       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).   

       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.   

       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.
st3f, Aug 17 2006

       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.   

       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.
strange606, Aug 17 2006

       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.
AlexTheGreat, Aug 21 2006

       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.   

       Which, I might add, has an automatic shutter system over it at night. Still can't get it to generate electricity, though.
normzone, Aug 21 2006

       I'm not burning the orbital toaster. I love the orbital toaster.   

       you might want to move your car out of the parking lot first
AlexTheGreat, Aug 21 2006

       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.
aguydude, Aug 23 2006

       //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?
Ling, Aug 29 2006

       Really? nobody mentioned a Peltier Junction? see the link
Brian the Painter, Jan 06 2013

       The Seebeck rather than the Peltier effect is what you want if you're looking for thermoelectric conversion.
8th of 7, Jan 06 2013

       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.   

       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.   

       The same area of solar panels, on the other hand...
MaxwellBuchanan, Jan 10 2013

       [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.
MechE, Jan 10 2013

       Carnot efficiency is only relevant if there is something you'd rather be doing with the input work, land area, or resources utilized.   

       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.
RayfordSteele, Jan 10 2013


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