A/C - gas or electric?
#11
06-22-2006, 06:01 AM
Active Enthusiast
Join Date: May 2006
Location: Houston, TX
Posts: 86
Re: A/C - gas or electric?
Originally Posted by Mr Bean
What the heck? I thought the first several posts laid out quite well that the Prius AC is independent of the ICE and therefore should not be a hit on the engine, particularly ten miles per gallon worth of a hit. It can be a hit as it draws the battery down to require the ICE to run and recharge but if you are already driving, this is likely occurring anyways as the ICE runs.
Regarding the window up down dilemma, click and clack on NPR talk about this one frequently adn their current logic holds that 30mph and below it does not increase drag enough to not have windows open. Over 30 and certainly over 50 they recommend the AC over window drag.
Regarding the window up down dilemma, click and clack on NPR talk about this one frequently adn their current logic holds that 30mph and below it does not increase drag enough to not have windows open. Over 30 and certainly over 50 they recommend the AC over window drag.
#12
06-22-2006, 06:24 AM
Engineering first
Join Date: Oct 2005
Location: Huntsville, AL
Posts: 5,613
Re: A/C - gas or electric?
Exactly:
There is no "free lunch" although sometimes, you can get a discount. <grins>
When driving in the hot Alabama summer with AC, my NHW11, 03 Prius will cycle the ICE at a long light to keep cool air coming from the AC. I would expect the NHW20 model to make it up by cycling the ICE to preserve battery charge. But one of the tricks I use is to turn up the AC temperature control when I come to a stop and turn it down only as I approach my local cruise speed.
The theory is ICE start/stop takes energy. By reducing the AC load when stopped and accellerating, I avoid AC triggered ICE start/stop and put the load on as I'm reaching an efficient ICE operating mode at cruise speed. I used to do this with my Camry too.
The MPG hit is real. The other day, in 95+ (F) heat cruising at 51 mph down the Parkway, I noticed that with AC, I was only getting 56 MPG on the display versus a 60+ MPG I'd ordinarily see. But then sometimes we have to pay for our creature comforts and the heat and humidity were brutal.
Not this season but someday in the future, I want to investigate ammonia-absorbtion cooling using waste exhaust heat. There is no 'free lunch' but this may be an effective, auxillary cooling source. But that will wait until next year.
BTW, that AC impact chart looks a lot like one from the Dept. of Energy report "INL/CON-05-00964", which Google can find very easily. The "Vancouver" report has a lot of additional details that I'd recommend for anyone.
Bob Wilson
Originally Posted by lakedude
Having electric AC does not eliminite drag on the engine. True with electric AC no belt goes directly from the ICE to an AC compressor but the load comes in the form of increased elecrical load which in turn eventually translates to an increased mechanical load on the engine. AC usage always reduces gas mileage reguardless of the method of powering the AC. Drag is drag.
When driving in the hot Alabama summer with AC, my NHW11, 03 Prius will cycle the ICE at a long light to keep cool air coming from the AC. I would expect the NHW20 model to make it up by cycling the ICE to preserve battery charge. But one of the tricks I use is to turn up the AC temperature control when I come to a stop and turn it down only as I approach my local cruise speed.
The theory is ICE start/stop takes energy. By reducing the AC load when stopped and accellerating, I avoid AC triggered ICE start/stop and put the load on as I'm reaching an efficient ICE operating mode at cruise speed. I used to do this with my Camry too.
The MPG hit is real. The other day, in 95+ (F) heat cruising at 51 mph down the Parkway, I noticed that with AC, I was only getting 56 MPG on the display versus a 60+ MPG I'd ordinarily see. But then sometimes we have to pay for our creature comforts and the heat and humidity were brutal.
Not this season but someday in the future, I want to investigate ammonia-absorbtion cooling using waste exhaust heat. There is no 'free lunch' but this may be an effective, auxillary cooling source. But that will wait until next year.
BTW, that AC impact chart looks a lot like one from the Dept. of Energy report "INL/CON-05-00964", which Google can find very easily. The "Vancouver" report has a lot of additional details that I'd recommend for anyone.
Bob Wilson
Last edited by bwilson4web; 06-22-2006 at 06:26 AM.
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