GRA
Well-known member
SageBrush said:GRA said:Replacing/expelling heat built up while parked is a different matter, and in that situation cracking the rear windows makes sense, but that's short-term at the start of a drive, not continuous for hours. And of course I use a reflective sunshield and park facing south when there's no shade.
It is the same matter -- the total energy used for cooling for a trip. And it is almost always true, except for very long trips, that the lion's share of A/C work is related to removing the heat accumulated while parked when the windows are closed and the sun is not blocked, not the heat that enters the cabin while driving. On average, cars in the USA are driven about an hour a day, and sit for about 11 hours a day. Using A/C to dispel the heat from 11 hours a day while parked is the much larger problem.
Uh huh, and since virtually all my driving trips are long to very long, and the car is often parked at altitudes where the ambient temp is reasonable, most of the time just opening the rear hatch and doors while I'm loading the car after whatever activity I've been doing is enough to let any accumulated heat out, assuming I haven't been able to park in the shade. Having worked in solar I'm far more aware of the sun position and height, both current and progressing through the day, than the average person, so I park and shade accordingly.
Another way to estimate the A/C work during driving that is not related to dispelling retained heat is this:
Estimate glass as 1 meter*meter facing the sun, and average sun inclination at 45 degrees
Radiation is 1000 watts per metermeter facing normal to the sun*
So average heat entering the cabin through the glass is about 700 watts.
Presuming a COP of 3, about 200 -- 250 Wh of electrical energy used per hour for steady state A/C
Call it one mile of EV range spent per hour for A/C
Given modern, more efficient A/C systems I agree the difference is minimal, but then that's the point of doing the experiment, to see how minimal. As it happens I was able to charge at short enough intervals that it didn't matter (with either of the two cars I drove; I'm renting a 2022 Niro the middle of this month to drive on the same route, and we'll see how I do with its shorter range). BTW, it really bugs me that Hyundai decided not to offer the solar roof in the U.S., when it could handle all the sunny day hotel loads in summer, and depending on your latitude winter as well, plus allow you to replenish the battery during the day while it sits at the trailhead when you're out skiing, if you'd slept in it the night before and were using utility mode or heat. BEV range is especially impacted by heater use even with a heat pump, so their decision makes zero sense to me.