AC Mod: Peltier Junctions

[ttoyoda]

And I figure I can just use the existing AC radiator and pipe the heat from the hot side to that in order to keep them cool.

If you can turn your existing AC radiator (you do really mean the condenser in front of the car radiator?) into a working heatpipe without changing its orientation so it is above your peltiers (for gravity return of the working fluid) then you are WAY smarter than anyone I have ever met... As for your question, the short answer is I don't know. The longer answer (question?) is how do you know that 300 watts of cooling will do anything for you? Where did you come up with that number?

[abshnasko]

I have experience working with peltiers and I've used some 75watt junctions before. I'm confident that 4 of them working together can provide reasonable comfort. Im trying to increase FE, therefore EXTREME air conditioning is not the purpose here. I'm looking for a way to make my ac use less resources from my car... if I get a lower performing ac then fine, in fact im expecting this... its just that I know of no way to mod my current air conditioner to use less energy.

also, I know of ways to use copper tubing to pipe the heat up to the front radiators without having to relocate it. This type of relocation of heat is common in desktop computers.

[ttoyoda]

also, I know of ways to use copper tubing to pipe the heat up to the front radiators without having to relocate it. This type of relocation of heat is common in desktop computers.

Perhaps you know all this already, but are you aware that this "copper tubing" actually has a poreous wick or very fine grooves on the inner walls which (by surface tension) wicks the working fluid back to the hot end of the heat pipe, and at the hot end the liquid working fluid is vaporized by the heat, with the vapor drifting thru the hollow center of the tube to the cold end? And that the system has to be evacuated of all non-condensible gasses? That the interior of the system must be very clean to avoid wick problems? Also, historically, these wicks become ineffective after years of use and the heat pipe stops working. That is ok if you are using the heatpipe on a sattelite, with limited lifespan anyway. Assuming the wear-out of the wick problem has NOT been fixed, there are going to be some unhappy computer users some years from now.
It is unclear to me how you plan to condense the working fluid in the cars original condenser and then still get it picked up by a wick to bring it back to the hot end. But if you do, my hat off to you.

[JohnnyGrey]

its just that I know of no way to mod my current air conditioner to use less energy.

Cycle it?

Underdrive pulley? (for fixed displacement compressors)

Using recirculation mode?

If you have a variable displacement compressor, it will only take as much power as it needs to keep cool, which is reduced by using recirculation and adding window tint.

[abshnasko]

Ok thank you all for the suggestions. Since not one of you attempted to answer my original question which I repeated twice (see posts #10, #6, and #1) I will look somewhere else for the answer.

I'm looking for a well thought-out, perhaps of mathematical origin, of whether 300watts of additional electrical load on the alternator uses more or less energy than the ac compressor. If someone knows about air conditioners and can provide a solution to this question, please PM me. In the mean time, I will continue my googling.

[JohnnyGrey]

Yes, a 300W draw will cause less drag on the engine than the AC compressor - if your alternator can handle it. Expect to lose 1hp, where the AC might use 10 or more.

However, I think you'll find a 300W TEC to be grossly inadequate for your purposes. Did you get my point on the importance of blocking UV/IR rays at the windows? 1KW of heat per square meter is nothing to write off.

[jamesqf]

How about a really low-tech way to reduce temperature? Buy one of those plastic spray bottles, fill it with water, and squirt a bit around the car. I do it before starting in hot weather, to cool off the steering wheel & dash (which around here can get so hot they're painful to touch).

[Logic]

IIRC TECs have an efficiency of around 7% and the stock AC in your car is much higher than that.
The fans etc that come on already make use of your solar and probably pull about as much power as the solar makes.
So no; don't use TECs.

What you might consider is:

• The 'auto switch off aircon' (and alternator etc) during acceleration and 'auto switch it on during slowing/braking' when you have 'free energy' if/when you gear down.
• Evaporative cooling using an ultrasonic mist maker you put in that interior air intake under the grille near your wipers where there's a high pressure area.

NB that Evap won't work in a humid climate.