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Quicksilver's Avatar
 
Join Date: Jul 2002
Location: SC - (Aiken in the 'other' SC)
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Lightbulb New A/C idea. Somebody build it!

Ran across this truely different A/C idea on Slashdot this morning. It uses existing technology and should be much lighter then stock. It should be possible to package it smaller also.

http://www.sltrib.com/utah/ci_2841984

I know that these chips have been used to do 'high performance' cooling of computer chips and portable 12V coolers. Now it is time to do some research and see what specs these things have.
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Old 07-21-2005, 06:21 AM
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Looks like the A/C equivalent of the E-Ram
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Old 07-21-2005, 06:32 AM
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Another great idea from the land of cold fusion, described in "breathless" style by a reporter who likely wouldn't know Poisson's ratio from the Peltier effect. The Peltier effect has been known and utilized for a long time. The thermoelectric devices described have a low coefficient of performance (COP) like .4 to .7
compared to 3 for an ordinary automotive system using R-134a.
One would need a big alternator to run enough of these "cooling chips" to cool down a 911. Cheers, Jim
Old 07-21-2005, 07:30 AM
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45% efficiency for a traditional AC system, and 5-8% for these chips according to what I read.
They'll need considerable advancements to make it work, and if you ran it off of your engine (let's say directly somehow like the compressor), with 5-8% efficiency versus 45% you'd need 38HP out of your engine for the same cooling effect you're presently getting with 5HP.
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Old 07-21-2005, 07:55 AM
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I've tinkered with peltier devices (building my own coolers etc)
problem is the chip heat must be dissipated efficiently and the heatsink to air interface is also not very efficient. They're about 3/16" thick and the hot and cold side must be attached to their heat sinks (so the heat dump side is close to the cooling side) You could put it through body metal, like the floor pan, and line the belly with heat sinks, and the floor with cold side sinks.
but you have to move a bunch of air on the inside. Then there's the inefficiency mentioned above. each chip needs huge current... I think my 2" x 2" chip draws 5 amps and will get a 6pack down to 50 degrees.
so you would need alot of chips. the delta T is only like 25-30 degrees from ambient. So, you'd need a really large high current alternator or generator. not really practical now - I've been watching these devices for years, just waiting for an efficiency improvement....
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Old 07-21-2005, 08:33 AM
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Not to rain on these kid's parade (kudos to them for trying), but the reporter fails to note that "Freon" based AC systems haven't been installed in cars since 1995. The current CFC-free refrigerant is environmentally safe.

I think those "clueless big-corporation GM engineers" back in 1964 were probably right that the idea is impractical. Gotta love reporting today.
Old 07-21-2005, 09:09 AM
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Peltier devices have been around for a long time. They have some serious limtations. (mostly thru-put . . .they are slow to move heat)
Quote:
Originally posted by jkarolyi
. ..Gotta love reporting today.
My thoughts exactly.

They say ".... to run their air-conditioners, which draw power from the engine. By adopting their contraption - which taps into the electrical system, .... " (Pay no attention to losses from generating the energy)

It's like the reporting "car built by physics students, achieves 100mpg, as it went down its mountain pass test course."

But hey; "It's been a total, unbelievable dream,"
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Old 07-21-2005, 09:55 AM
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One of the elective courses I took at school: "Advanced Energy Conversion Systems". There are now commercially available thermoelectric coolers which are ideal for...beer and a sandwich!

Not yet practical for the Porsche. Maybe by the time we can start filling up on hydrogen instead of Sunoco 260...

Pat
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Old 07-21-2005, 10:09 AM
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