[ausev] electric a/c system

[jtp]

Mark,
Please remove my name as a member of Austin EV, and from listing on the 
discussion forum.
 Thank You.
Dan Petit.











jtp wrote:
> In considering an electric prius ac compressor,  there are some power 
> management issues such as how much range you are starting off with in 
> the first place, then, of course, subtracting 15 to 20 percent for ac 
> power draw.  When I am servicing any auto 134a system,  it is clear 
> that the way to avoid very high cooldown demands are to prevent the 
> sunlight from building up too much latent heat in the first place.  
> Management of heat buildup with solar films and reflective barriers 
> placed in windows would help, but there is nothing better than the 
> possibility of parking in a shaded area for long term parking of more 
> than an hour. 
>   Generally,  134a systems need to be carefully calibrated in order to 
> prevent refrigerant superheat.   Superheat can have a compressor 
> taking far more power than expected, and reduce range more than 
> expected.   However,  designing in management values in evaporator air 
> transfer volume (not using the high speeds all the time), as well as 
> more refined cycling of the compressor may be the answer since you 
> would not be using all of the compressors' rated power demand at all 
> times, especially in a morning commute, when cycling could be reduced 
> to very minimums.  As well, the system may be designed to refrigerate 
> the cabin for 20 minutes with plugged-in power at home, thus 
> eliminating just about all of the excessive power demand potential, 
> even if it is parked in sunlight.   If there were an outlet available 
> at work, then the same logic could apply.  I really like Mark's Ford 
> Taurus' remote engine start system.  One like that could certainly be 
> used to pre-chill your EV with electric AC compressor refrigeration.
> Dan Petit.
>
>     ----- Original Message -----
>     *From:* Chris Cooper <mailto:chris.cooper at mail.utexas.edu>
>     *To:* AustinEV News Announcements and General Discussion
>     <mailto:ausev at austinev.org>
>     *Sent:* Thursday, August 24, 2006 8:04 AM
>     *Subject:* Re: [ausev] electric a/c system
>
>     Been there. Done that.
>
>     Peltiers are about 40% efficient so you would produce more heat
>     than cool. You would have to sink the hot side outside of the area
>     to be cooled. Car A/C units produce about 10,000-20,000 BTU's and
>     are about 70-90% efficient depending on compressor speed and
>     outside air cooling the condenser. You would need about 20
>     Peltiers to even crack the heat in a vehicle. That's 960watts best
>     case. If you wanted to experiment with Peltiers, I would go the
>     route of localized cooling; that's my next project. Are we back to
>     a space suit now? Or at least a space helmet? What is the end
>     result? Cooling the air in the cabin, or cooling YOU? Something to
>     think about. One advantage of Peltiers is you can connect them in
>     series and drive them directly with high voltage. A 96V system
>     could directly drive 8 Peltiers.
>
>      
>
>     Maybe the comical pictures of vehicles I've seen with a window
>     unit hanging out of the rear window  of a car actually have some
>     merit to them... they are about 90% efficient nowadays. You would
>     need a pretty hefty inverter, but inverters are about 90%
>     efficient too and there are some 48V inverters out there. You can
>     get about 5000BTU's on less than 550 watts.
>
>      
>
>     I had the opportunity once to drive one of the GM EV1 prototypes a
>     few years back and I asked the engineer how the A/C worked. It was
>     basically, very basically, a 330V(?) self contained A/C compressor
>     unit similar to  but smaller than a home central unit. It ran full
>     speed continuously eliminating the loss of cooling you get from
>     idling at stop lights, etc...
>
>      
>
>      
>
>      
>
>     Chris Cooper
>
>     Manager, Computer Services
>
>     Department of Biomedical Engineering
>
>     University of Texas @Austin
>
>     ------------------------------------------------------------------------
>
>     *From:* ausev-bounces at austinev.org
>     [mailto:ausev-bounces at austinev.org] *On Behalf Of *Joey Carroll
>     *Sent:* Wednesday, August 23, 2006 4:26 PM
>     *To:* ausev at austinev.org
>     *Subject:* [ausev] electric a/c system
>
>      
>
>     Hi everyone,
>     New guy here. No EV yet, but im looking at converting an 84 CRX,
>     and I had some input on the 12v Aircon systems. I'm not sure if
>     anyone has seen this story before, its about how 2 teenagers made
>     a compressor free air conditioner using peltier thermoelectric
>     chips. I know they aer terribly inefficient compared to phase
>     change cooling, but I think there is some potential there. I
>     recently got 2 of these chips off ebay for around $16, just to
>     play around with, I'll bring them to the next open garage or meet
>     if anyone wants to check them out.
>     link: http://www.treehugger.com/files/2005/07/teens_invent_fr.php
>
>     ------------------------------------------------------------------------
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