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Peltier Questions
I'm trying to figure out how much power I could generate from a peltier
device from a given temperature difference. With water as the medium on each side of the peltier, what temperature difference would I need to have to power a small water pump to circulate the water round my CPU cooler block? In other words - could a cooling system be designed to actually drive/power itself from the very heat it is trying to remove? Perhaps convection would be required to start or subsedise the equation, but do 'we' think this is possible?? Could this be scaled up to drive a water pump for a small pool, driven by a peltier that is powered by sun energy heating water on one side in a black, heat absorbing tank and cold water from the pool on the other side? |
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Peltier Questions
On Wed, 16 Jun 2010 10:11:50 +0100, "GT" wrote:
I'm trying to figure out how much power I could generate from a peltier device from a given temperature difference. It seems it would depend on the size of your peltier. A single peltier would produce a very low voltage so you would need several in series, an expensive project considering how little electricity costs, and quite large unless it were (an even more expensive) specialized device like this: http://www.hi-z.com/hz2.php With water as the medium on each side of the peltier, what temperature difference would I need to have to power a small water pump to circulate the water round my CPU cooler block? Depends on the water pump and flow rate desired? If you are intending to use waste heat from the CPU you have a problem, that to create the temperature gradient needed you would have to let the CPU get very hot or create a sub-ambient temperature on the cold side, again using externally supplied energy to pump heat off the cold side. In other words - could a cooling system be designed to actually drive/power itself from the very heat it is trying to remove? Perhaps convection would be required to start or subsedise the equation, but do 'we' think this is possible?? Possible yes... on a NASA budget and developed for years. Not the best solution here on earth. Could this be scaled up to drive a water pump for a small pool, driven by a peltier that is powered by sun energy heating water on one side in a black, heat absorbing tank and cold water from the pool on the other side? No, practically speaking the size and cost of doing it would negate any real benefit. Peltiers are not very efficient, you'd be better off with solar panels which aren't very efficient either... even for powering the computer water pump from the slight bit of light in the computer room instead of sunlight by using more/larger panels. |
#3
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Peltier Questions
GT wrote:
I'm trying to figure out how much power I could generate from a peltier device from a given temperature difference. With water as the medium on each side of the peltier, what temperature difference would I need to have to power a small water pump to circulate the water round my CPU cooler block? In other words - could a cooling system be designed to actually drive/power itself from the very heat it is trying to remove? Perhaps convection would be required to start or subsedise the equation, but do 'we' think this is possible?? Could this be scaled up to drive a water pump for a small pool, driven by a peltier that is powered by sun energy heating water on one side in a black, heat absorbing tank and cold water from the pool on the other side? There are devices, that demonstrate the kind of temperature differential and heat flux needed for decent power generation. http://www.leevalley.com/en/gifts/pa...at=4,104,53221 "Thermoelectrics to replace car alternators and improve MPG" http://www.gizmag.com/thermoelectric...ove-mpg/10928/ But to address the problem, of "powering a cooling system", you need to compare the efficiency of water cooling to heatpipes. There is no comparison. Heat pipes are much more efficiency at heat flux transport, than an equivalent water cooling system. And it's because of the larger amount of heat per gram of material involved in a phase change. A heat pipe uses phase change as the transport mechanism. The only thing I don't know, is to what distance the capillary effect, can be used to transport condensed liquid back to the source. Water cooling systems are used, because they're relatively cheap, and easy to install. Custom heat pipes, bent to fit your installation, wouldn't be nearly as easy to set up. The capillary effect is available, when the inside surface of the heat pipe is sintered. The condensed liquid can actually go uphill, but with some loss of effectiveness. Zalman built a couple computer cases, that use heatpipes to connect heat sources, to the outer wall of the computer case. The computer is a giant convection cooler. The case pictured here, was around $1000. http://www.overclockers.ru/images/la.../10/back-b.jpg http://www.overclockers.ru/images/la...eatpipes-b.jpg http://en.wikipedia.org/wiki/Heat_pipe If you have a heat source and sink, there is always stuff like this. The Stirling engine allows you to get close to the Carnot limit, although at the expense of a non-compact solution. Some day, we may see more of these. http://en.wikipedia.org/wiki/Stirling_engine http://en.wikipedia.org/wiki/Carnot_heat_engine Paul |
#4
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Peltier Questions
"Paul" wrote in message
... GT wrote: I'm trying to figure out how much power I could generate from a peltier device from a given temperature difference. With water as the medium on each side of the peltier, what temperature difference would I need to have to power a small water pump to circulate the water round my CPU cooler block? In other words - could a cooling system be designed to actually drive/power itself from the very heat it is trying to remove? Perhaps convection would be required to start or subsedise the equation, but do 'we' think this is possible?? Could this be scaled up to drive a water pump for a small pool, driven by a peltier that is powered by sun energy heating water on one side in a black, heat absorbing tank and cold water from the pool on the other side? There are devices, that demonstrate the kind of temperature differential and heat flux needed for decent power generation. http://www.leevalley.com/en/gifts/pa...at=4,104,53221 Ahh - might as well forget it I think. If 170 degree difference is only enough to drive a small, effecient fan, then water pumps are out of the question for a 30-50 degree temperature difference! Looks like I'd be pushed to drive a few LEDs with that! Thanks for the links and info, but I'll give up that idea straight away! |
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