| Author | Message | ||
| JW Smythe (Jwsmythe)
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Ok, here's a stupid question for all of you... Has anyone seen anything on using thermoelectric/peltier air conditioning on a bus? I just sent an email off to one place that seemed to have the only thing resembling large enough to even possibly handle our size, so we'll see if they write back.. For those that don't know, a peltier cooler is the cooling part of what makes those little 12v beer coolers work. Some CPU fans had the peltier cooler between the CPU and heat sink too. Interesting stuff. I thought it would be interesting to have an absolutely quiet air conditioning. Well, except for the blower fan noise, but a good fan should be quiet. | ||
| truthhunter@shaw.ca Rating: N/A |
I had surfed a little on this several years back, found that one could assemble a system but cost prohibited. I am not clear on what to expect as with power efficiency , which is also very important over the long run. My small amount of surfing also lead me to a related project with one of the truck companies that was testing this technology as thermocouples in the exhaust system to recuperate heat energy and transform it into electricity with the idea of replacing the alternator, a very small gain in the efficiency saved by not turning a alternator on the truck , but again expensive and not cost effective. | ||
| David Hartley (Drdave)
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Peltier modules generally only can operate with a 70 degree temperature differential between the hot and cold sides. There are some hybrids that can operate with higher differntials but are stacked. The also require huge amounts of d.c. current to operate for a given size. They also require lots of heatsink area. A typical PM is about 1" square and pulls about 3 amps or so at 12 volts which is what is used in the coolers | ||
| JW Smythe (Jwsmythe)
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70 degrees sounds good. If it's 100 degrees outside, that would bring the inside temp down to 30.  I think I'm going to buy one or two modules to play with. They're going cheap on eBay, so it'll be a fun toy to play with, and we'll see how much power I manage to suck up with it. Then I can judge if 20 are going to be more juice than a pair of roof mounted 110vac air conditioners. | ||
| truthhunter@shaw.ca Rating: N/A |
look forward to your findings JW S. | ||
| Nick Badame Refrigeration Co. (Dnick85)
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JW, So 38.400 square inches will require 115,200 amps DC. Sounds like you will need a serious power plant to cool your coach??? Dr. Dave Also mentions lots of heatsink????? Mabe your entire outter shell will be 250 Degrees? JW, It sounds like you should look down another venue Sorry- Nick- | ||
| Gus Causbie (Gusc)
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Nick, You need to redo your math, he didn't say it would only cool one square inch. In fact, he said it would cool a cooler-didn't say what the volume of the cooler is though. | ||
| Ron Walker (Prevost82)
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JW...if you duct your a/c units you won't even hear them on low speed and on high speed it makes great white noise for sleeping at Fly'g J's or noisy rest stops, but are 1/2 the noise as a direct vent. | ||
| David Hartley (Drdave)
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Oh.. And more http://www.kryothermusa.com/Thermoelectric%20Air%20Conditioners%20&%20Coolers.htm There's a lot of info on these coolers, Peltier modules are everywhere. All share a certain hunger for fairly high current usage but will last a very long long time. | ||
| truthhunter@shaw.ca Rating: N/A |
hum,If NB guesstimate is valid the with a 250 degree bus shell temperature used as a heat sink, you could attach some of those thermocouples at that tempature and make a lot of "perpetualy free electricity" not to mention keeping the grizzly bears and vandals from touching your bus for long. Of course in the perfect world you would have to spend a lot on insurance for the liability of pedestrian/admirer hand burns. Now were can we salvage all this equipement for 2 cents on the $100 bill? | ||
| David Hartley (Drdave)
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1500 btu a/c unit http://www.eicsolutionsinc.com/thermoelectric_cooling_systems.htm Surplus sources & info http://www.peltier-info.com/surplus.html | ||
| David Hartley (Drdave)
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Here's a thought.. Just came up with this one. " or while we are dreaming :o " Build an array to mount on the roof, make a hot side/cold side sandwich that absorbs the suns heat, have water tubes in it to make hot water, then use excess heat from the absorber plate to run a series of peltier modules to generate electricity, The cold side (bottom) would have tubes to take out cooler water and provide the surface-to-surface temperature differential to make the power. The trick would be that if designed properly you could charge batteries while heating water and running the pumps. Then if you need cooling just apply power back to the modules to chill the water from the bottom side, make hot water on the top side and run the chilled water to a air/water heat/cool coil down in the coach. Or make a second roof shell with the skins bonded to peltier modules. Top side painted black and bottom side equipped with water tubes to run a heat exchanger for a/c... | ||
| truthhunter@shaw.ca Rating: N/A |
When are some of those coldfusion nay say going to have their "crack" at this one. I am starting to perspire under my Alcan hat. Wishing I had installed a few of those solid state refer units when I had the chance! But back to the basics in the mean time- those larger 1500 btu commercial units seem to require around 4 times the power to achieve the same heat exchange as a conventional carbunkle A/C Heat Pump. Not including any modifications to perpetuate power regeneration/thermal storage. | ||
| Nick Badame Refrigeration Co. (Dnick85)
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Guss, Still, As per site given by Dr. Dave If a 1500 btu unit draws 6.3 amps@ 120v Need min. 30,000 btu [typical bus] Sorry, I come up with over 125 amp draw?? Not Too Pratical! Nick- | ||
| David Hartley (Drdave)
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1,500 btu is enough to stuff cold air through a piece of tubing down the drivers shirt! Or maybe with a good blower maybe up through the seat bottom? Oh... How about a Bikers helmet with a/c ? Now there's an idea.... | ||
| Nick Badame Refrigeration Co. (Dnick85)
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Dr Dave 1500 btu's isn't even enough to cool my set of you know what's!! in a cold spell Nick- | ||
| David Hartley (Drdave)
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It's a matter of density and airflow.. Harrrr.. Harrr | ||
| JW Smythe (Jwsmythe)
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I went ahead and ordered two 62mm 350W peltier junctions. We'll see how they perform, just screwing around at home. I think I have a 12v adapter around the house somewhere. At most, I'll be really anxious about doing it larger scale. At worst, I'll have something to cool my drinks. It *SHOULD* be about 2400 BTU's, which should be able to give a good chill a small room. The specs say 0-15V, 0-30A, with an operational range of -60 C to +180 C . Oh my, I guess if it's 76 degrees below 0, I won't have any heat. Are there roads to the arctic circle? I don't know where to find +350 F | ||
| David Hartley (Drdave)
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You will need some 4X4 inch aluminum heatsinks to attach those modules to. I have a an Igloo coolmate 40 qt cooler and it has fans on each of the heatsinks. (boxer fans 12 volt) A 24 pack of pepsi takes 10 hours to cool down to a nice drinking temperature. Uses about 3.75 amps running continously. If you want to shed more heat and pump more cold you will need some really big heatsinks. sized basically equally. They also generate more heat than they absorb due to current losses. Oh.. BTW.. engineers design specs don't really apply in the real world so don't be upset if they don't exactly work as advertised. But it's worth the tinkering just for fun... | ||
| JW Smythe (Jwsmythe)
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Ya, I know specs are never what I should expect. These appear to be much larger than the ones showing up in the coolers. I saw one ad on eBay selling bulk heatsink material. It was feet long. Unfortunately, now that I've decided I should give this a shot, I can't find the damned thing. I did find a manufacturer, so I may see if they have some scraps in long lengths. Otherwise, I have a lot of old CPU heatsinks here, so I'll just strap those on to screw with 'em. Our 1u servers come with their own heatsinks that actually fit in the case, so we keep 'em or toss them in the trash. Have you played with them at all? I was reading on another board that these things are spec'd for up to 15v, but they're most efficent at 7v. They also mentioned to hook them in series to drop the amp load. I'll try different combinations with the two units, and see how it works. I'm anxious about playing with them now. I had taken one of the igloo coolers apart years ago, and it had a tiny peltier module. It could have used a larger module. Our trips were only a few hours, so it never was very good at cooling our cooler. |