Robert Bruninga via EV wrote:
A huge advantage of EVs is sitting at an event (or drivein movie) in AC
comfort on a hot day without an engine running.
Id like to come up with some numbers to describe the total heat generated
by an ICE at idle running its AC compared to an EV.
Here is a technical paper.
http://www.invisaflects.com/wp-content/uploads/2016/08/vehicleair.pdf
All I can understand is figure 5 and 6. Figure 6 seems to imply that cool
down begins to take about 3 kW but tapers to under 200W as temperature
stabilizes.
But that conflicts with figure 5 that suggests the 2 PM heat gain is over
1000 W solar heat gain and 500 W lost due to ventilation. Big difference
between 200 W and 1.5 kW?
Anyway as a starting point, I am going to assume 1 kW cooling. Now assume
that the AC requires about 500 W electrical to pump about 1 kW of heat out
of the cabin. That 1 kW cooling is then exhausted outside more like 1.5 kW.
Now the ICE is assumed to be generating power from an ICE and so WHAT is
the amount of heat exhausted to the outside to achieve the same 1 kW of
cooling?
This reference shows BEV's are about 75% tank-to-wheels efficient and ICE's
are about 15% for a 5 to one ratio.
http://www.afteroilev.com/Pub/EFF_Tank_to_Wheel.pdf
But its much worse than that. I am going to assume that running an AC
compressor at Idle is not nearly as efficient as running it when the car is
moving down the road and the ICE is in a more efficient range. And the
compressor is mechanical and with belts. So, I am going to assume it is
50% worse at idle as electrical.
So I could claim that the exhaust heat surrounding an ICE parked with the
AC running is TEN times that from an EV.
Anyone want to refine these assumptions and results?
My feeling is that there is no simple answer. It would depend heavily on
the conditions!
I think I would approach it from the "fuel consumed" end. Measure the
amount of fuel the ICE uses when left idling for an hour with the the
A/C on, and then again with the A/C off (same day, same location, etc.)
This might be most easily done in a car that has an MPG computer, though
I don't know how accurate they would be while idling.
Then do the same thing with an EV. Again, this would be easier in an EV
that has gauges or instruments to monitor actual power consumption.
Both gallons of gas, and KWH of electricity can be converted to BTU.
That should provide a pretty good estimate of the relative efficiency,
and the amount of waste heat being generated.
PS: I hesitate to imagine how hot an Arizona drive-in movie would be
with every car in the lot running its ICE with the A/C on.
Lee Hart
--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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