[ausev] electric a/c system

Thu Aug 24 17:54:47 GMT 2006

    A generator would be horrible ick. It would be better to drive my wifes prius if I had to do that, which I have done with all the 100+ degree days. Hopefully one could get one that would work off a modified sign wave inverter to save some cost. Maybe they even offer smaller units that use less power which would help immensly.
    It may sound like a bunch but 1800 watts isn't too bad for such a short drive that an EV might have. It isn't much more then my ceramic heater used to warm up a frozen EV when I was back in connecticut. Up there I had the double ding of Heat for the person using 10 amps or so and cold batteries cutting range when the vehicle sat at the train station 14 hours in the cold so overall A/C would be easier on the pack even with this oversized unit. 
    Plug in cooling sounds good for those lucky enough to have a plug at work where it will pick up all the heat. Sadly my vehicle is in full sun for 8+ hours a day with no possibility of a plug. I'd only run A/C on the way home because in the AM it usually isn't hot enough to matter and if it wasn't a quick run of the AC while plugged in might be more then enough. In that case for my less then half hour drive it would useat most 900 watts out of my pack. For my S-15 pickup that might cut my range by 2-3 miles. Since my batteries are so much warmer in the summer that might edge up capacity a bit to offset that.

----- Original Message ----
From: Chris Cooper <chris.cooper at mail.utexas.edu>
To: Mark Hastings <evblazer at yahoo.com>; AustinEV News Announcements and General Discussion <ausev at austinev.org>
Sent: Thursday, August 24, 2006 11:01:04 AM
Subject: RE: [ausev] electric a/c system

Those RV A/C units work GREAT for self-contained cooling. 
You’ll need 1800watts to run it and <3000 watts to start it. 
Pull a generator on a trailer or in the truck bed?
You could definitely keep your vehicle cool if you plugged it in to house power in between trips so it wouldn’t have to work as hard on battery power. EMS ambulances to this all the time.
Perhaps this may be part of the answer? Cool down the vehicle before you leave?

C²

From: ausev-bounces at austinev.org [mailto:ausev-bounces at austinev.org] On Behalf Of Mark Hastings
Sent: Thursday, August 24, 2006 10:32 AM
To: AustinEV News Announcements and General Discussion
Subject: Re: [ausev] electric a/c system

Last year I used a single peltier with a couple large fans and it worked well for spot cooling through the rear of my seat. For the summer I put in a screen like seat back that you might see on a recumbent bike. This really helped for my evening commute home. I did arrive home a little warm but my back wasn't soaked like it was with both the vynil and no circulation or cooling. I didn't use it this summer since my EV was mostly out of service due to a large number of age related issues, both mine and the 86' S-15 pickups.

Recently I have been looking into an RV AC like: 
http://www.rvsupplywarehouse.com/product/detail.cfm/pid/2711
Since the S-15 is so high I actually thought of putting a low profile one under the cab or on/under the bed and ducting it in. It is a little more expensive then a window unit but at least it is built for mobile use. If I got a new hood it might make a good fake little hood scoop since I'd have the space under the hood to do some ducting.

----- Original Message ----
From: Chris Cooper <chris.cooper at mail.utexas.edu>
To: AustinEV News Announcements and General Discussion <ausev at austinev.org>
Sent: Thursday, August 24, 2006 10:04:53 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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