Will Model 3 get a heat pump for cabin heating?

[scaesare]

Tesla seems to think it helps...

I believe what we are seeing here confirms that the waste heat from the drive unit can heat the battery pack, but not the cabin, as posted above.

In "cooling" mode the Cabin loop is "closed" (via valves 157 & 159) and coupled to the refrigerant loop via heat exchanger (133). The Pack loop is also coupled to the refrigerant loop in this mode. The Drive unit loop is isolated.

In "heating" mode, valves 157 & 159 put the Drive Unit loop in series with the heat exchanger via line 151 and pump 149. The cabin radiator (153) is now isolated, with no coolant flow through it. Any heat delivered to the cabin is via the electric PTC heater (161). The warm coolant from the drive unit only exchanges heat to the pack via the heat exchanger (133) at this point.

In other words, when the drive unit loop is switched "in" to the heat exchanger loop, the cabin radiator is switched "out".

Now, I do admit that 153 is labeled "H/C RADIATOR", which I assume stands for heating & cooling, so I could be wrong here. But I think this is from a patent, and not necessarily what was exactly implemented. The reason for this is that the diagnostic screens we deiscussed in the Thermal Management thread differ in that they don't show the cabin receiving drive unit heat. Those who have seem them animated in real time agree that the flow never shows that.

 

[JeffK]

I believe what we are seeing here confirms that the waste heat from the drive unit can heat the battery pack, but not the cabin, as posted above.

Not true, let's look at the wording from the patent itself:

subsystem 107 is coupled to subsystem 101 via flow control valves 155, 157, and 159, thus allowing the coolant heated by subsystem 101 to flow through radiator 153. Additionally, in a preferred embodiment of the invention, a heater 161 (e.g., a PTC heater) is integrated within radiator 153, thus allowing cabin heating prior to that achievable by subsystem 101 alone.

In other words, they are saying the drive motor and electronics heat the coolant, the coolant then flows through the radiator 153 (the cabin). 161 is the PTC and the cabin is heated by both 153 (from 101) and 161.

Pasting the image again for convenience

I hope the wording from the patent makes it more clear.

 

[scaesare]

Not true, let's look at the wording from the patent itself:



In other words, they are saying the drive motor and electronics heat the coolant, the coolant then flows through the radiator 153 (the cabin). 161 is the PTC and the cabin is heated by both 153 (from 101) and 161.

Pasting the image again for convenience


I hope the wording from the patent makes it more clear.

As I had said:

But I think this is from a patent, and not necessarily what was exactly implemented.

I linked to a thread on this earlier... here's another pic that may make this clearer:

You can see that when in series mode, the heat from the drive unit does NOT pass through the HVAC block where the cabin conditioning occurs.

And, you can note that in the actual implementation, those coils in the HVAC block that are what the cabin air passes through, they are labeled "EVAP", not "H/C" as I noted in my caveat regarding the patent. THis indicated they are for A/C usage, not heating. The PTC is the only source of heat.

This operation has been confirmed by @Ingineer, who knows these cars inside and out (I encourage you to look at his posting history before to confirm).

This is really no different then a number of other Tesla patents, such as those noting intumescent coatings on the cells, that aren't always implemented in the current model S designs...

 

[JeffK]

This operation has been confirmed by @Ingineer, who knows these cars inside and out (I encourage you to look at his posting history before to confirm).

Here's a more succinct post for anyone interested How many coolant pumps does S have?

 

[gregincal]

Note that it's probably academic anyway. If it's even fairly cold out (say below 45 degrees F), then the waste heat from the drive unit isn't even sufficient to warm the battery pack, much less the cabin. Resistive heating is used for both, and the wh/mile spikes up no matter what you have the cabin temp set to (at least that's my experience). There just isn't that much waste heat.

 

[scaesare]

Note that it's probably academic anyway. If it's even fairly cold out (say below 45 degrees F), then the waste heat from the drive unit isn't even sufficient to warm the battery pack, much less the cabin. Resistive heating is used for both, and the wh/mile spikes up no matter what you have the cabin temp set to (at least that's my experience). There just isn't that much waste heat.

I expect that's why they didn't bother to implement cabin heating... just not enough energy there to do both... and warming the battery to allow it to produce greater power was probably the priority...

 

[AustinPowers]

Just keep in mind the Leaf, e Golf, and likely your house have some form of supplemental heat. The heat pump simply helps reduce energy usage of these other technologies, which is great for efficiency, but it cannot provide instant heat on its own.

Don't know about the Leaf, but the e-Golf with heat pump, afaik has no other supplemental heat system.
And our house definitely hasn't. It was built from the start with the heat pump as its one and only heating system. And as I said, it works perfectly fine, even in the coldest winters we had.

Caveat: of course it isn't "instant on / instant off". If you want to heat the house up from "zero", it does take up to a few hours until it reaches the target temperature. But as our standard room temperature in winter is about 20 degrees Celsius in "normal" rooms like living room or kids bedrooms, and about 22 degrees Celsius in special rooms like the bathroom and kitchen where we spend most of the free time, it doesn't take that long to heat up even from the "off"-setting we use during spring/summer/autumn.
Pity only that we didn't get the cooling-function (i.e. heat pump in reverse) for summer, as at the time of construction of our house we had to save money wherever we could, so we skipped this quite expensive add-on option. In hindsight we should have spent that money anyway, but one is always wiser later...

 

[stopcrazypp]

Don't know about the Leaf, but the e-Golf with heat pump, afaik has no other supplemental heat system.
And our house definitely hasn't. It was built from the start with the heat pump as its one and only heating system. And as I said, it works perfectly fine, even in the coldest winters we had.

Caveat: of course it isn't "instant on / instant off". If you want to heat the house up from "zero", it does take up to a few hours until it reaches the target temperature. But as our standard room temperature in winter is about 20 degrees Celsius in "normal" rooms like living room or kids bedrooms, and about 22 degrees Celsius in special rooms like the bathroom and kitchen where we spend most of the free time, it doesn't take that long to heat up even from the "off"-setting we use during spring/summer/autumn.
Pity only that we didn't get the cooling-function (i.e. heat pump in reverse) for summer, as at the time of construction of our house we had to save money wherever we could, so we skipped this quite expensive add-on option. In hindsight we should have spent that money anyway, but one is always wiser later...

Keep in mind the supplemental heat is sometimes built into the heat pump itself with resistive elements.

 

[McRat]

Don't know about the Leaf, but the e-Golf with heat pump, afaik has no other supplemental heat system.
And our house definitely hasn't. It was built from the start with the heat pump as its one and only heating system. And as I said, it works perfectly fine, even in the coldest winters we had.

Caveat: of course it isn't "instant on / instant off". If you want to heat the house up from "zero", it does take up to a few hours until it reaches the target temperature. But as our standard room temperature in winter is about 20 degrees Celsius in "normal" rooms like living room or kids bedrooms, and about 22 degrees Celsius in special rooms like the bathroom and kitchen where we spend most of the free time, it doesn't take that long to heat up even from the "off"-setting we use during spring/summer/autumn.
Pity only that we didn't get the cooling-function (i.e. heat pump in reverse) for summer, as at the time of construction of our house we had to save money wherever we could, so we skipped this quite expensive add-on option. In hindsight we should have spent that money anyway, but one is always wiser later...

In the USA, cars have to pass a defrosting test for FVMSS. This pretty much guarantees you can't go heat pump without a resistive heater added, or it fails the defrost time test. American ICE cars run the A/C while defrosting with engine heat. A heat pump can't run in A/C mode and heater mode at the same time.

 

[JeffK]

Don't know about the Leaf, but the e-Golf with heat pump, afaik has no other supplemental heat system.

An image similar to this is in the Nissan Leaf service manual

from the vw site:

To help ensure optimal performance in cold weather, a newly developed heat pump system that is fitted in the SEL Premium model uses both ambient air and heat from the drive system components to warm the cabin rather than relying solely on the high-voltage heater, which can help to reduce on-board electrical consumption, especially in winter driving.

this is also quoted from news websites:

A newly developed heat pump—which will be applied in the US e-Golf—enables better driving range in colder temperatures. An add-on module to the electric heating (high-voltage heater) and electric air conditioning compressor, the heat pump recovers heat from the ambient air and the heat given off by the drive system components. This significantly reduces the high-voltage heater’s electric power consumption to keep the passenger cabin comfortable. When the heat pump is used, this increases the driving range in cold weather of the e-Golf by more than 30% compared to a conventional heating system.

 

[ItsNotAboutTheMoney]

I know several Leaf and e-Golf owners that also have a heat pump for cabin heating, and all of them are very happy about the effectiveness of those systems, even in cold winter weather.

Our house also has a heat pump for all our central heating, and even though I was sceptical at first about efficiency, after almost nine years I can honestly say it's been perfect for us. Far cheaper than oil or gas heating while just as comfortable, even in very cold winters, of which we had a few, especially in the first years after we had had the system.

I would be very happy if the Model 3 had a heat pump. Otoh, if they use a different yet equally efficient system, I won't mind either. We will find out soon enough.

Define cold.

 

[AustinPowers]

Define cold.

Where we live, the coldest it got in the last few years was about -20 degrees Celsius, which would be around -4 degrees Fahrenheit.

 

[arnolddeleon]

In the USA, cars have to pass a defrosting test for FVMSS. This pretty much guarantees you can't go heat pump without a resistive heater added, or it fails the defrost time test. American ICE cars run the A/C while defrosting with engine heat. A heat pump can't run in A/C mode and heater mode at the same time.

Well, the original Toyota RAV4-EV 1997-2002 did not have a resistive cabin heater, just a heat pump. It solved the windshield defrosting with high voltage heated windshield. IIRC it possibly also had dual coils in the dash to allow it produce dry warm air for the windshield. To maximize range the in winter you didn't even turn the heat pump on, you just used the heated seats and heated windshield. Tesla drivers are so spoiled with their huuuuge batteries ;-)

arnold

 

[JeffK]

Well, the original Toyota RAV4-EV 1997-2002 did not have a resistive cabin heater, just a heat pump.

On the first generation models from 1997 to 2003 wikipedia says:

The passenger compartment is heated and cooled electrically using a heat pump (the first fleet application of a heat pump in a road vehicle) with supplemental electrical resistance heating as backup.

but I can't actually find hard evidence from Toyota either way. It looks like only around 1500 were ever produced between those years and very few were sold to consumers (328), most were fleet vehicles for California (with California weather). We do know for sure that all gen II models of the RAV 4 EV do have a PTC heater with the heat pump so either way the first gen wasn't adequate.

 

[McRat]

The EV1 and S10 EV were both heat pumps. Wiki is wrong. The S10 EVs were fleet sales and street legal.

 

[SageBrush]

Tesla doesn't currently use a heat pump but they do pump in heat from the drivetrain and electronics according to their patent. Supposedly once warmed up and the car has been moving, the Tesla heater only draws 1-2 kW to maintain temp which is similar to the leaf. I don't have hard measurements so maybe someone can confirm.

That would be outstanding, although my napkin arithmetic says not much waste heat is available. That is the point of an electric drivetrain.

If you figure 15 kW to drive the highway and 15% is waste, you have 2250 watt waste heat.

Addendum: arithmetic corrected

 

[Yggdrasill]

That would be outstanding, although my napkin arithmetic says not much waste heat is available. That is the point of an electric drivetrain.

If you figure 15 kW to drive the highway and 15% is waste, you have 225 watt waste heat.

2.25 kW, not 225W.

 

[JeffK]

The EV1 and S10 EV were both heat pumps. Wiki is wrong. The S10 EVs were fleet sales and street legal.

Who were you replying to? The wiki I posted was from the RAV4 EV nothing to do with GM EV1 or an S10 EV

 

[SageBrush]

2.25 kW, not 225W.

Yes -- thank you. I was about 30 seconds too late catching my error before you

I kept looking at that 225 W figure and thinking "why did they even bother?" LOL
Anyway, we should keep in mind that some of the waste heat will be retained by the battery for its own comfort.

I wonder if the complementary approach needed here is to reduce undesired ambient air leaking into the cabin and a low cabin heat capacity.

 

[McRat]

Who were you replying to? The wiki I posted was from the RAV4 EV nothing to do with GM EV1 or an S10 EV

It claims Toyota was first heat pump car. That is not likely since they were other heat pump cars before Toyota released one to the public. I will admit I do not which car came first, but it was not Toyota.