Why does Tesla use a Resistance Heater instead of Heat Pump

[D.E.]

Heat pumps work essentially by extracting heat from the outside air. They work well for moderately cold temperatures but when things get very cold, the heat pump will be unable to extract heat from the outside air. So you’d need resistance heat as a backup for extremely cold temperatures.

A heat pump requires a lot of hardware. Resistance heat require just a resistance coil and a fan. The resistance setup will be much lighter and simpler. Since you’d need resistance heat in any case, the heat pump setup becomes a costly, heavy, complicated addition. The heat pump would be more battery efficient for moderately cold temperatures but the weight, hardware, and cost overhead is likely not worth the battery power savings.

 

[arnis]

whether it makes sense for a global vehicle fleet.

It doesn't make any sense to make one variation/setup of vehicle for the whole world.

A heat pump requires a lot of hardware.

What hardware? "Heat pump" is not an additional device.
No need to make excuses for disadvantages of some party, especially with incorrect statements.

 

[mongo]

It doesn't make any sense to make one variation/setup of vehicle for the whole world.

Does it make sense to create variations in your fleet to support a subset of the world/ option package? Full NRE and support cost for a reduced production volume.

 

[arnis]

Yes. For example winter tires. Or steering wheel that is on the other side.

Tesla ONLY adds whatever feature if it is a bare minimum. Like steering wheel that is on the side of opposite traffic. But it's not ok to "have only things that make vehicle usable because we want maximum sales".

 

[nimrooz]

What hardware? "Heat pump" is not an additional device.

You're correct, a heatpump or ac is a collection of parts, like condenser, evaporator, compressor, etc. Put together to make a unit that either cools, heats or both.
However, it would be an additional device in the model s, as the ac runs on R1234yf, and heatpumps/aka heat exchangers usually runs on another type, like R410.

 

[riles246]

You're correct, a heatpump or ac is a collection of parts, like condenser, evaporator, compressor, etc. Put together to make a unit that either cools, heats or both.
However, it would be an additional device in the model s, as the ac runs on R1234yf, and heatpumps/aka heat exchangers usually runs on another type, like R410.

You’re basically saying that Tesla’s don’t have heat pumps because they don’t have heat pumps. The point is- why didn’t they put in the R410 system to begin with instead of the R1234yf?

 

[nimrooz]

Environment and costs I guess.
R1234yf is the newest and most environmentally friendly.

 

[Benjanos]

Heat pumps work essentially by extracting heat from the outside air. They work well for moderately cold temperatures but when things get very cold, the heat pump will be unable to extract heat from the outside air. So you’d need resistance heat as a backup for extremely cold temperatures.

A heat pump requires a lot of hardware. Resistance heat require just a resistance coil and a fan. The resistance setup will be much lighter and simpler. Since you’d need resistance heat in any case, the heat pump setup becomes a costly, heavy, complicated addition. The heat pump would be more battery efficient for moderately cold temperatures but the weight, hardware, and cost overhead is likely not worth the battery power savings.

This is exactly correct. Tesla made the right move IMO.

 

[arnis]

R1234yf is the newest and most environmentally friendly.

Both not totally true. But the fact that it is not suitable for HP capable HVAC makes it irrelevant for EV-s in the long run.

 

[nimrooz]

Both not totally true. But the fact that it is not suitable for HP capable HVAC makes it irrelevant for EV-s in the long run.

Maybe there is a newer one, but which is it? Because as far as I remember, R1234yf is the newest AC gas?
And yes, exactly my point, it's unsuitable for hp.

 

[Legen---dary]

Hopefully one day Tesla will rewrite the book on HVAC, and build a device that uses high-pressure helium within a Stirling cycle heat pump that's fully reversible. A unit that could be the core of a small home AC, or used across all of their vehicles.

 

[Toumal]

What hardware? "Heat pump" is not an additional device.

My Zoe had a heat pump. Everything D.E. said is correct. You need a condenser, evaporator, a big and noisy fan, etc - it is an impressive amount of hardware. Also, the efficiency benefit disappears at below 4 degrees Celsius. The PTC comes on and essentially heats the car. When I had a minor frontal collision, most of the repair cost was due to heatpump components

 

[arnis]

My Zoe had a heat pump. Everything D.E. said is correct. You need a condenser, evaporator, a big and noisy fan, etc - it is an impressive amount of hardware. Also, the efficiency benefit disappears at below 4 degrees Celsius. The PTC comes on and essentially heats the car. When I had a minor frontal collision, most of the repair cost was due to heatpump components

Oh my god. It is not good to state things that are out of someone's expertise.

All these components exist on vehicles with no heat pump. All vehicles with AC have those things. Because heat pump is the same thing as air conditioning. Difference is in few valves that redirect refrigerant to run in reverse. There is one evaporator but it is inside a HVAC box and will never be damaged in reasonable car crash.

Also your 4-degree celsius story is nonsense. Or it might be Zoe specific due to some defect or software problem.

 

[Toumal]

You are blissfully ignorant of the reverse cycle setup of the Zoe. And you have never compared the two it seems. You probably think the superbottle is the same thing. It is not.

Read up first before schooling others. Or take a look yourself like I did.

 

[nimrooz]

Also your 4-degree celsius story is nonsense. Or it might be Zoe specific due to some defect or software problem.

I think that is a Zoe specific problem, as others I know with a Zoe have the same problem, and also that it won't turn on when driving with low battery.
It's just undersized I guess.
However, modern heatpumps today works well in the -10c down towards -20c.
But they loose their efficiency for every degree downwards from 0c. And de-ice more often the colder it is.
And every time it's de-icing it won't heat the user space.
I guess I would maybe use a blend of resistor an hp if I where to make the most energy friendly (battery friendly) heating mechanism in a car. But then the cost is higher...

Edit: I have newer driven a Zoe, or looked under the hood, so I really don't know, but 2 friends with Zoe says the same thing.

 

[Toumal]

I can only talk about the Zoe. I agree it is probably an issue with their design. It was touted as a feature but in operation it was a nightmare. Getting the windows to defog in -20C was difficult and the thing made a huge racket, easily as noisy as an actual gas engine.

 

[arnis]

HP efficiency is a function of refrigerant gas type, compressor maximum pressure capability, external condenser size and external temperature and humidity. Most heat pumps, incl automotive, can cope with -10C and do NOT cope with -20C.

 

[Saimaannorppa]

More than a heatpump (which has marginal gains in specific temperature range), I would like Tesla to improve insulation on cars. Adding a layer of insulation to cabin would work in all conditions, and would also benefit in cooling and road noise.

If you strip down the interior, you’ll notice there is very little insulation material anywhere. Same is of course true for any car, but an EV would benefit greatly.

The best way to conserve energy is to make use of it unnecessary in the first place.

 

[arnis]

I agree. But Tesla's most problematic region is the heating up. Battery and cabin. Insulation doesn't change that.
Tesla owners, on average, do not drive long distances. Therefore insulation has mediocre effect.
Björn from Norway does long distances and... well... after heating up the vehicle, consumption of heating is acceptable.
Though before INSULATION... they MUST HAVE SHADES. Especially roof, incl half of Model X windshield and half on 3 back window.

 

[arnis]

Maybe there is a newer one, but which is it? Because as far as I remember, R1234yf is the newest AC gas?

Well... newest and cleanest (and more efficient) refrigerant is R744. We know it as CO2. Technically it is not a new gas. Just newest system.
Merces already makes few models with this carbon dioxide as refrigerant. System costs slightly more but is also more efficient,
including heating cycle... that is definitely good news for EV's.

This gas is ideal for cold and mild climates but doesn't actually work when external temps are very high (30+C for example).
Therefore, again, one system for the whole world is definitely NOGO.
1234 gas for hot climates and not heat pump. CO2 based heat pump system for climates where temps go below freezing. Usually both extremes are not happening.

VW id3 - soon on the market, will have both options. Heat pump (R744 based) and regular.