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evnow
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NREL : Impact of Climate Control in Electric Drive Veicles

Fri Jan 21, 2011 9:33 am

Here is a fantastic simulated study on the effect of climate control, preheating and capacity loss at various temperatures for EVs and PHEVs.

http://www.nrel.gov/vehiclesandfuels/news/2011/929.html

http://www.nrel.gov/vehiclesandfuels/vsa/pdfs/49252.pdf

Bottom line : 35% drop because of climate control. Small gains from preconditioning. Capacity loss 3.5% in hot places vs 1.2% in cold (per year).

(Source greencarcongress.com thr' gm-volt.com)
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AndyH
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Re: NREL : Impact of Climate Control in Electric Drive Veicles

Fri Jan 21, 2011 10:37 am

Very nice find - Well done!

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drees
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Re: NREL : Impact of Climate Control in Electric Drive Veicles

Fri Jan 21, 2011 10:48 am

I scanned it quickly, but didn't see anything about total energy consumption?

In other words - how does total energy consumption compare between pre-conditioning and not-preconditioning?

While preconditioning reduces the load on the battery increasing range, etc - the longer you work to keep the vehicle at a desired temperature, the more energy it takes - so I wonder if the increase in energy used for HVAC is offset by avoiding by charge/discharge losses...

I would guess that it depends a lot on trip length... Heating/cooling the car down for a 5 minute trip vs a 40 minute trip, for example.
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evnow
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Re: NREL : Impact of Climate Control in Electric Drive Veicles

Fri Jan 21, 2011 12:09 pm

AndyH wrote:Very nice find - Well done!

I should credit this to Lyle/greencarcongress. I'll update the post.
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LTLFTcomposite
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Re: NREL : Impact of Climate Control in Electric Drive Veicles

Fri Jan 21, 2011 12:24 pm

Interesting, although here in FL I think of an automobile as an air conditioned space that just happens to provide transportation. It should also be possible to compute how many minutes of air conditioning are sacrificed for each mile of driving. :-)
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planet4ever
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Re: NREL : Impact of Climate Control in Electric Drive Veicl

Sat Aug 06, 2011 3:44 am

I haven't studied this report in detail, but I feel like I must be missing something. Looking specifically at cooling for the LEAF, the range advantage of precooling is less than 2%. The only real kicker here seems to be their claims about battery life. Here their numbers seem quite suspect. Is it really likely that precooling a 95 degree cabin for ten minutes would reduce a 95 degree LEAF battery pack to 80 degrees if the outside temperature is 95 degrees? I'm no expert on thermodynamics, but I am visualizing a heavy flat block of material with no active circulation exposed to 95 degrees on one side and maybe 75 degrees on the other side. Run the precooling for an hour and you might get down to 85 degrees, no?

Apart from my skepticism on that, my real personal problem is that the only time I might encounter a situation like that is in the afternoon. And in the afternoon (at least on summer weekdays) my electric rate is between two and three times as high per kWh as at night when I charge the car. If I'm going to precool I'd rather do it with cheap electricity, i.e. not plugged in. Driving the car can use bursts of up to 80 kW (though not the way I drive), but cooling it seems never to use more than 5 kW. Is a 5 kW draw on a hot battery going to be as hard on it as a 50 kW draw?

And, by the way, the real bottom line here seems to be that if you are going to be driving your car on a hot day it is far better for the battery if you DO have the A/C on, so it can help keep the battery cool.

Ray
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evnow
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Re: NREL : Impact of Climate Control in Electric Drive Veicl

Sat Aug 06, 2011 9:33 am

planet4ever wrote:Is it really likely that precooling a 95 degree cabin for ten minutes would reduce a 95 degree LEAF battery pack to 80 degrees if the outside temperature is 95 degrees?

You are making the mistake of equaliting cooling/heating the cabin with cooling/heating the battery. Not the same at all. As the report title says - this is about climate control for the people in the cabin.
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ENIAC
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Re: NREL : Impact of Climate Control in Electric Drive Veicl

Sat Aug 06, 2011 10:05 am

evnow wrote:
planet4ever wrote:Is it really likely that precooling a 95 degree cabin for ten minutes would reduce a 95 degree LEAF battery pack to 80 degrees if the outside temperature is 95 degrees?

You are making the mistake of equaliting cooling/heating the cabin with cooling/heating the battery. Not the same at all. As the report title says - this is about climate control for the people in the cabin.
He's referring to table 6.

For scenarios that include thermal preconditioning, the battery pack temperature was adjusted from ambient temperature. That is, for thermal preconditioning scenarios, the battery was warmed above a cold ambient temperature or was cooled below a hot ambient temperature over a 20-minute period prior to driving. These climate control, ambient, and battery pack temperature scenarios are presented in Table 6.
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evnow
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Re: NREL : Impact of Climate Control in Electric Drive Veicl

Sat Aug 06, 2011 11:09 am

planet4ever wrote:And, by the way, the real bottom line here seems to be that if you are going to be driving your car on a hot day it is far better for the battery if you DO have the A/C on, so it can help keep the battery cool.

That is if the battery is kept cool by the A/C ... is that true ?
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Bassman
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Re: NREL : Impact of Climate Control in Electric Drive Veicl

Sat Aug 06, 2011 11:32 am

I don't know about the 2.1 KW steady load for AC. After the first 10 minutes my draw is typically less than 750 watts for AC running. I may get 3 to 4 miles reduced range if that, a far cry from their calculated 35% reduction or the reduction shown in their figure for Cooling. For the LEAF, I 'd say more like a 3 to 5% reduction without precooling the cabin. ;)
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