Jim R
Member
Wouldn't that be friction? Drag would be air resistance when in motion. Aircraft drag comes to mind.Mechanical losses due to half shafts, gearbox, and bearings spinning.
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Wouldn't that be friction? Drag would be air resistance when in motion. Aircraft drag comes to mind.Mechanical losses due to half shafts, gearbox, and bearings spinning.
In order for a heat pump to extract a reasonable amount heat from the air, it must be several degrees colder than the air. If it is near or below freezing cold out, the moisture in the air will freeze. All heat pumps deal with this; it's a solved problem. I would expect the heat pump to run at least an hour before needing to defrost. My home units usually make it several hours between defrost cycles.
Can't slow down HP because energy is required ASAP. The most amount is required within first 10 minutes.
And 90+% commutes are up to 30 minutes. So it won't even get to first defrost cycle.
Also in demo scenario, if HP is off, heat exchanger temp is -2*C. If it is "slightly active" it is -3*C. Full power -8*C.
It hardly matters. For air moisture, for snow. It will just jam the fins if vehicle is in motion in all 3 modes.
And like I demonstrated, energy required to melt is insignificant. Time for defrost is more important. It can easily be done
within 4 minutes. And I believe Tesla can push it to 3 minutes. 10% downtime in worst case scenario is ok.
Slowing down HP to try to avoid it... Well, the only way for that is to waste lots of battery power (same as PTC).
PS: all heat pumps (AFAIK) are all inverter based. So... they pretty much never work at 100%.
They hardly can work at 100%. There are very specific requirements for HP to be able
to "be cranked up to 100%". My car does that maybe 10-30 minutes per year.
Read. The. Patent.All EVs with heat pump have defrost cycle. It works only when vehicle is stationary for few minutes OR
vehicle has radiator shutters that are more-or-less airproof.
Tesla will also do defrost cycle. Refrigerant is rerouted to external heat exchanger heating it up making it hot.
Read. The. Patent.
Battery. Is. Not. A heat source. In cold. Conditions.
Similarly Toyota is not "self charging hybrid".
Patent ≠ actual design used
Mostly agree with all that, but what is the advantage of frosting/ freezing over the radiator just have to defrost it again? Why not instead run the system on the edge of frosting?
Unless your defrost drops off chunks of ice, the energy transfer to/ from the moisture is net neutral with net loss to the environment.
I don't think you know exactly how a heat pump works. Ice just naturally builds up on one side. My house heat pump goes through periods of time where it's running the "A/C" to heat up the radiator to melt any ice. So during that time it's blowing cold air in to the house and the heat will be on the coils to melt the ice buildup.
I don't think you know exactly how a heat pump works. Ice just naturally builds up on one side. My house heat pump goes through periods of time where it's running the "A/C" to heat up the radiator to melt any ice. So during that time it's blowing cold air in to the house and the heat will be on the coils to melt the ice buildup.
Compressor wiring/windings/fuse might handle 1kW and even 2kW. but not 4kW.
There is no reason to remove PTC/resistive heater from the vehicle.
Though moving it from HVAC under the frunk has some advantages.
In some scenarios compressor has to stop. This is why second heating apparatus must be available.
How can you say it needs 4kW of heat, but then claim the LV PTC can fulfill that with only 14*40*2 = 1.12kW (assuming it is 40A)? Side note: Those are for split temperature control and are mostly likely medium speed PWM, so not relay operated.Disagree x 4
mongo
MP3Mike
Eugene Ash
Big Earl
Well.. as we see, resistive heaters are still there. Though they are still inside HVAC unit.
Though making them 14V ones simplifies the design. I bet they are around 40A each with just on/off relay/transistor.
If HP stops for more than few minutes car will be undriveable in winter. And there is absolutely no redundancy.
Resistive heaters reduce the risks and add comfort.
Coolant pumps are redundant to each other, therefore no worries there.
BTW, last winter that exactly happened with my car. HP stopped
(pressure sensor failure, possibly low refrigerant as well). All went well.
Fixed the problem a month later without problems with daily commuting.
I don't believe air moisture has condensation heat to give out to the fins. Though solidification heat is available.
I believe the weight of air moisture that is in gas state (humidity) is much smaller than the part that is liquid (fog).
Mostly it is that "wetness" in air that solidifies on the heat exchanger.
But yes, overall amount of energy is ridiculously tiny to consider in the equation. That I did state
For "normal" vehicle behavior in cold weather, 1, 2 and even 3kW is not enough.
Likely compressor maximum power intake is around 3kW. Maybe 3500W. Assume COP 1.0.
That is not enough in extreme cold temps (below -25*C). Adding one extra kilowatt will be somewhat
helpful and maybe, MAYBE, tiny amount (200-500W) could be extracted from drivetrain and electronics.
Yea. I'm not sure will lossy motor mode will be used if compressor is not doing that. Maybe for SuC preparation. That would help with speed.
Frost that appears at the expansion valve will reduce effectiveness of that "corner" pretty fast. After a while most of the heat exchanger surface is equalized accordingly.
Yes. Glycol as a media for energy transfer is interesting. Ground source heat pump systems actually use ethanol blend not glycol (at least modern systems). It is less viscous and has better properties for heat transfer. Also better for environment. Totally drinkable
For vehicle to be driveable windscreen must be clear. Tesla does not offer heated windscreens.
But 1kW of heat can defrost windscreen for vehicle to be driveable at -20*C.
Also cabin will be at acceptable temperature (a little above zero).
Heated surfaces (steering wheel, seat) will add comfort.
For "normal" vehicle behavior in cold weather, 1, 2 and even 3kW is not enough.
Likely compressor maximum power intake is around 3kW. Maybe 3500W. Assume COP 1.0.
That is not enough in extreme cold temps (below -25*C). Adding one extra kilowatt will be somewhat
helpful and maybe, MAYBE, tiny amount (200-500W) could be extracted from drivetrain and electronics.
In total, that will be sufficient for Model 3 and Y (still not enough for X). Drivetrain and plumbing is cooled
with very cold air flow during driving. For HP to extract energy from there it must cool it noticeably
below ambient. If ambient is -25*C then HP can't actually go easily to -35*C. Also that starts to
mess with oil viscosity and frost on the drivetrain.
Also if driver is heading to supercharger, system will struggle with no spare capacity. Car might be
stuck at SuC for half an hour before charging starts. That actually is still a problem with Model 3 without HP.
All this is not important when COP is 2.0 or more. But often it is not. At some moment before defrost
cycle starts COP drops to near 1.0.
Energy extracted from vehicle itself is not multiplied with COP factor. 300W out of
vehicle drivetrain is 300W of heat to cabin.
I wouldn't bet that LV heaters are PTC.