Air Conditioning

<div class='quotetop'>QUOTE(orr4hoos\";p=\"77940)</div>

The AC is wholly electric and does not directly depend on the gas engine at any time. I have found that it works just as well as the AC on my other cars (Camry and Windstar). As for the AC's effect on fuel use, it's bound to cause some reduction since the gas engine will have to run more to keep the batts charged. My batt level regularly dips below 5 bars (out of 10 on the display) when using AC, while it rarely dips below 7 when not using AC. I've only started using the AC regularly over the past week or so, and I have noticed a bit of a decline in fuel economy. For the first 150 miles on the current tank I did not use AC and averaged about 47 mpg (according to the computer). For the past 70 miles or so I've been using the AC a lot, and my average mpg is down to about 45. I can't say that my driving pattern has changed significantly in the past 70 miles, so I would attribute most or all of the change to the use of AC.

 

The Prius a/c works great. Auto climate is a nice touch and a rare feature in vehicles of the Prius price point. Show me a Corola or a Focus with auto climate.

The Prius a/c is also very efficient. It uses a variable speed compressor which means that the system runs the A/C compressor at the speed necessary to acomplish whatever goal is set for the climate control system. a/c in cars today is run off from the pullys on the engine. The Prius design is such that there is no engine drag or pull down that you feel from some vehicle a/c systems, especially on smaller vehicles. Plus most vehicle a/c systems don't cool as well, while idiling or at a stop. The Prius system is consistant whether at speed or at rest.

Sure there will be a fuel economy hit, but I don't think it is nearly as much as on a conventional vehicle. And there is certainly a performance boost by having the a/c not dependant on engine speed.

 

"there will be a fuel economy hit, but I don't think it is nearly as much as on a conventional vehicle."

I would like to see numbers on this. Considering the inefficienciues of conversion from kinetic to electrical and back (vs. direct drive of the compressor from the conventional ICE), the net effect may be positive or negative.

 

This presentation specifically claims a 19% reduction in fuel consumption over the belt-driven air-conditioning system in the old Prius.

 

Here we use the A/C in the car pretty much year round. And yes, you do get a hit in MPG, but it's not too great. During our 100+ days (May, June, July, August, part of September, and sometimes early October), I see a drop of 3-4 MPG.

Thanks,
Shawn

 

There are numbers posted here. I've posted the engineering papers on the A/C a couple of times.

Bottom line is it's about 40% more efficient than conventional AC.

 

get that back window tinted..big heat draw ...

 

Hijack:

sk66. Here's all my points for you being a Bronze sponsor of the site with only 7 posts under your belt!

Now, back to air conditioning:

 

I had the same concerns that you do re-air conditioning since I live in So. Florida and need it most of the year. I will tell you that you will never regret buying the prius. My A/C in on all the time and I am averageing over 50 mpg with normal driving and expect better when my engine is broken in. I did notice one trip on the interstate at 75 mph against a strong headwind a 5 gph dip but on the return trip made up for it and then some. I have owned some very exotic autos but this one I like the best of all.

 

After my first winter with my prius I eagerly await the days i can run my a/c ALL the time. The cold weather makes a much bigger hit on your mpg's than running the a/c ever did LOL

 

paprius4030
said it all, cold much worse than any amount of A/C ever could hit the MPG. I still think that the A/C compressor should be a hybrid unit like on the Accord hybrid. If the ICE is running use it to power the comp. if it's off ues electricity. On the hiway where the ICE is turning over to protect MG1 from overspeeding it might as well power the compressor instead of the losses converting A/C to D/C and then sending it to power the motor in the compressor.

 

after last summer my hit on mileage was 1-3 mpg.

 

<div class='quotetop'>QUOTE(Frank Hudon\";p=\"78249)</div>

The problem with Belt Driven Compressors is that they run at the speed of the ICE regardless of whether that is the most efficient use of that energy.

The Prius electric compressor is variable speed, so like the ICE it can run at whatever speed is necessary and most efficient at any given time, completely independent of the ICE, which, because of the PSD, also chooses it's most efficient setting.

The Prius A/C is about 40% more efficient than the old belt driven systems, as well as being more environmentally friendly by using less refrigerant, so I don't see any reason to go backwards.

 

It is hard to give hard numbers, since the Prius A/C is so variable from 2 degrees of freedom: Continuously Variable A/C compressor, and continuously variable cabin fan. Reaching a temp will of course use more energy than maintaining it.

Also note, HVAC can maintain a comfortable humidity level, as well as compensate for solar radiation. That sensor on the dash near the windshield is the solar radiation sensor for the HVAC. Canadians will also see a sensor for the Auto headlamps.

Personally, I'd say I see an avarage of 2MPG hit using A/C.

 

the belt driven comps also cycle off and on and that is controled by the expansion valve on the evaporator and the same is true for the electric driven comps in the G2 Prius.
What I said is when the ICE is running or turning over to protect MG1 from over speeding, the A/C system should use the ICE to power the compressor. This is what the Accord does, and I still think it would be better if the Prius used the same general type of design. When you go out to your car and it's 95-100 inside and your start it up the ICE runs, why not use it to power the compressor to assist in pulling down the temp. It'll still cycle on and off as determined by the expansion valve, then in a couple of blocks or miles when the car goes into S4 it reverts to electric unless the ICE is running. Using electricity to run some thing while the unit making the electricity is running isn't really necessary when at a manufacturing level the cost to implement the dual drive is probably only 50$

 

But Frank-
The scroll compressor is so much more efficient than belt driven compressors that it more than compensates for the conversion losses.

I can't believe that I'm disagreeing with you on this cuzudaman!

 

actually the Classic compressor is a scroll plate type as well. Edited to include Belt driven.

 

Reverts to Electric? Dual Driive? So you're adding parts, weight, complexity, cost and load to maybe gain a tiny theoretical efficiency by bypassing conversion of some energy to electricity.

How do you propose to completely unload the ICE from the belt connection when the compressor is NOT being used. Otherwise, you do just what current designs do, and throw away energy ALL THE TIME.

Sorry, but I strongly suspect Toyota thought it through pretty well, but just off the top of my head I see absolutely no benefit you your approach and plenty of downsides.

I like it just the way it is. Small, Light, Simple, nearly twice as efficient as belt driven A/Cs, and with a much smaller environmental footprint.

I suspect belt driven A/C will go the way of the dodo pretty soon. It just has no real advantage besides cost and inertia any more.

The next generation of the Denso Units will use C02 as the refrigerant, which will help even more with removing persistent pollutant hydrocarbons from the cycle.