Tesla's Heat Pump System and Octovalve

[TrevRex]

Now I see the words Heat pump, as though there is a component called a Heat Pump in our Teslas, get thrown around a lot on this forum but according to this video there is no Heat Pump per se in our cars but a Heat Pump System that has from my quick count on some cars (depend on RWD or AWD) 22 different heats sources that gets transferred around the car so the words Heat Pump System.

Now the video has a excellent timeline feature as part of the video and an excellent presentation IMO of the Heat Pump System and the Octovalve.

Moderators please shift this post if I have stuffed up my search to see if a new thread is warranted for this topic.

 

[Quickst]

It's just a bit of plumbing and a few pumps, moving coolant around the vehicle. Even the ICE cars have a heat pump - moving coolant from the hotter engine to the lower temperature cabin.
But all these are just moving heat down hill - from higher temp area to lower temp areas

The real heat pumps are the ones which move heat uphill - ie moving heat from lower temp areas to higher temp areas as in an AirCon (eg keeping cabin at 20C by moving heat out to the hotter 35C outside air)

What Tesla has done is to recognise there are heat sources even in a non ICE and has put in plumbing to harvest some of that already generated heat rather than using the battery to run a heater element to generate new heat.
Tesla says it uses up to 20% less energy by using its heat pump, but I am skeptical because it depends on the relative heat generated by all the 22 sources and the internal cabin and outside temperatures.

The octovalve just moves the coolant to where it thinks the heat is needed

 

[TrevRex]

I am adding this video from the same University and the same Professor to help explain the Octovalve modes of operations better IMO which can be seen in Service Mode on the car's display.

 

[brainhouston]

Not sure what the official technical qualifications for Heat Pump but most common one is the ability of AC system to work in reverse.
Newer Tesla's definitely have it.
Just like ur house Heat Pump, with only AC compressor/freon n reversing valve/hardware it can make evaporator (whats inside the house/car cabin) warm instead of cold. Everything else that tesla added is extra bells n whistles to save more energy.

ICE cars definitely don't have Heat Pumps, its not needed for an engine that produces waste heat..

 

[BitJam]

Moderators please shift this post if I have stuffed up my search to see if a new thread is warranted for this topic.

I had started a thread about this video a few weeks ago:

Everything you've ever wanted to know about the heat pump

This is what you'd get if Sandy Munro were a teacher, not an automotive engineer specializing in machine tools and manufacturing. I've watched this series of videos on the octovalve. It was impressive but mind numbing.

This guy is an excellent teacher IMHO. He tears things down like Munro et al but he then explains how it all works. Great stuff!

 

[Quickst]

ICE cars definitely don't have Heat Pumps, its not needed for an engine that produces waste heat..

Heat pump can pump heat up the thermodynamic incline - from cooler to hotter. These are your air conditioners. Both Tesla and ICE have them. A reverse cycle ac in a house can do that. Pump heat out of the house in summer to keep it cool. Then in winter in reverse pump heat from the cold outside air to keep inside warm. But it is pumping heat from cooler to hotter

The car AC heat pump can cool a cabin in summer by dragging heat from cabin and pumping it into the hot outside air and maintaining a cabin temp lower than outside. ICE not need to pump heat from a cond winter air and heat a cabin- it uses the hot engine. Tesla AC I believe is a true Reverse cycle AC.

Both ICE and Tesla have waste heat management which pumps heat from one part of the car to another but these only pump heat from hot areas to cooler areas. So traditionally not called heat pumps because they only pump waste heat from hotter to cooler.

In the case of ICE it pumps waste heat from engine to cabin using coolant and a pump to warm it

In the case of Tesla it pumps waste heat from any of its 22 sources of waste heat to heat any of the 22 parts which may need heat
Again using liquid coolant and pumps. But not AC refrigerant which uses refrigerant, pumps and compressors

If not enough heat from any of those sources, it uses the aircon to drag heat from cold winter air

It is unfortunate that Tesla calls it a heat pump. Because technically a heat pump is usually used for pumps which pump heat from cooler to hotter - technically maintaining a temperature difference between the two environments. The heat pump Tesla call as referenced above cannot do that. It cannot for example use waste heat and make other parts warmer than where they took the waste heat from. . Again it's real heat pump is the AC.

 

[cafz]

It is unfortunate that Tesla calls it a heat pump. Because technically a heat pump is usually used for pumps which pump heat from cooler to hotter - technically maintaining a temperature difference between the two environments. The heat pump Tesla call as referenced above cannot do that. It cannot for example use waste heat and make other parts warmer than where they took the waste heat from. . Again it's real heat pump is the AC.

It's all part of the same system, there's a pair of back-to-back manifolds that allows heat to be transferred between the coolant circuit and the refrigerant circuit.

 

[TrevRex]

Not sure what the official technical qualifications for Heat Pump but most common one is the ability of AC system to work in reverse.
Newer Tesla's definitely have it.

Where in that video I attached from the Professor presenting it does he mention a reversing valve is present on the newer Tesla vehicles that "reverses" the direction of the flow of refrigerant, which changes the direction of heat transfer that is used on Reverse Cycle AC as a heat pump?

Now he does mention what he calls "Heat Source 16. Hot high-pressure vapor recirculated into the receiver dryer through a mister." that in his words "it's basically short circuiting the refrigerant loop." and the valve controlling that function called the recirculation solenoid. I don't think we can call that a reversing valve and the Professor certainly doesn't from what I see.

 

[brainhouston]

Heat pump can pump heat ...

u lost me here...

 

[TrevRex]

I had started a thread about this video a few weeks ago:

Everything you've ever wanted to know about the heat pump

Ok Sir I did not search outside the Australian forum where I posted this thread and actually I never do.

 

[brainhouston]

Where in that video I attached from the Professor presenting it does he mention a reversing valve is present on the newer Tesla vehicles that "reverses" the direction of the flow of refrigerant, which changes the direction of heat transfer that is used on Reverse Cycle AC as a heat pump?

Now he does mention what he calls "Heat Source 16. Hot high-pressure vapor recirculated into the receiver dryer through a mister." that in his words "it's basically short circuiting the refrigerant loop." and the valve controlling that function called the recirculation solenoid. I don't think we can call that a reversing valve and the Professor certainly doesn't from what I see.

Tesla actually did slightly different 'reversing'
They put a separate 'cabin condenser' (he showed it at 12:00 min mark)
He didn't cover the reversing but its done by Super manifold with all those solenoids.

 

[Vostok]

As @Quickst said, a “heat pump” is a pump that moves existing heat in the atmosphere from one location to another, against the temperature gradient, by using the Carnot cycle.

An air conditioner is a heat pump, but historically in Australia the meaning of “air conditioner” was one that cooled only, i.e. pumping heat from inside a house to outside. That’s why “reverse cycle” was added to the term “air conditioner” to make it clear that those units could both cool and heat the inside of a house, by running the Carnot cycle in reverse.

In New Zealand, they have always been called “heat pumps”.

 

[TrevRex]

Tesla actually did slightly different 'reversing'
They put a separate 'cabin condenser' (he showed it at 12:00 min mark)
He didn't cover the reversing but its done by Super manifold with all those solenoids.

Sorry I did not get back to you earlier as I have been busy at work.

I submit you are getting confused with your analogy you express here IMO.

Yes Tesla put in a separate cabin condenser ,actually two (driver side and front passenger side) hence our dual zone climate control, solely for the reason of that a condenser, which we must remember is the hot part in the refrigeration cycle, is needed to provide heat when we are cold in the cabin if we want to use the refrigeration cycle to provide that needed heat. Or we need to "reverse" the refrigeration cycle so the same components can be used as in our Reverse Cycle AC systems depending on our cooling or heating requirements.

Now "those solenoids" you mention are all covered by the Professor in his video as he explains what they all do. 53:00 min mark "The six electronic expansion valves (EXV) Stepper Motors (Chiller, Evaporator, Left CC, Right CC, LCC, Recirculation)."

Now I may be wrong about you getting confused so can I please ask you what "reversing" the Professor "didn't cover"?

 

[brainhouston]

Sorry I did not get back to you earlier as I have been busy at work.

I submit you are getting confused with your analogy you express here IMO.

Yes Tesla put in a separate cabin condenser ,actually two (driver side and front passenger side) hence our dual zone climate control, solely for the reason of that a condenser, which we must remember is the hot part in the refrigeration cycle, is needed to provide heat when we are cold in the cabin if we want to use the refrigeration cycle to provide that needed heat. Or we need to "reverse" the refrigeration cycle so the same components can be used as in our Reverse Cycle AC systems depending on our cooling or heating requirements.

Now "those solenoids" you mention are all covered by the Professor in his video as he explains what they all do. 53:00 min mark "The six electronic expansion valves (EXV) Stepper Motors (Chiller, Evaporator, Left CC, Right CC, LCC, Recirculation)."

Now I may be wrong about you getting confused so can I please ask you what "reversing" the Professor "didn't cover"?

Sorry he did cover it later at 54:05, this is ur basic Heat Pump mode (he called it Heat Source 1 at 11:15)

He showed a traditional car AC system at 44:50, where Condenser is outside which gets hot n cools off by a fan and Evaporator inside the cabin that gets cold n give u cooling.
In case of ur house Heat Pump, reversing is done with some valve (not fully sure) but u don't have extra Condenser in ur furnace, the evaporator becomes condenser thru reversing function..
In Teslas case they stuck another set of Condensers in the cabin n all the "reversing" is done with solenoids on Super manifold. So technically not reversing per se but just different routing for refrigerant.
Depending on which solenoids are open u either get cooling thru evaporators or heating thru Cabin Condensers.
This is the Heart of the Heat Pump, everything else is additional ways of saving even more energy by not wasting it.

This is just my understanding so u don't have to accept it or believe it

 

[TrevRex]

Sorry he did cover it later at 54:05, this is ur basic Heat Pump mode (he called it Heat Source 1 at 11:15)

View attachment 947980

He showed a traditional car AC system at 44:50, where Condenser is outside which gets hot n cools off by a fan and Evaporator inside the cabin that gets cold n give u cooling.

Yes and like the Professor explains the condenser on Tesla for cooling is outside the cabin on the Super Manifold and is liquid cooled instead of a fan so the heat can be stored in the coolant and used for say heating the battery or for getting rid of excess heat through the radiator. Is abbreviated in the video LCC (Liquid Cooled Condenser).

In case of ur house Heat Pump, reversing is done with some valve (not fully sure) but u don't have extra Condenser in ur furnace, the evaporator becomes condenser thru reversing function..

Yes the reversing is done with the Reversing Valve and like I have said before "so the same components can be used" or like you say "the evaporator becomes condenser" and the condenser becomes the evaporator and vice versa depending on heating or cooling requirements.

In Teslas case they stuck another set of Condensers in the cabin n all the "reversing" is done with solenoids on Super manifold. So technically not reversing per se but just different routing for refrigerant.

Yes I agree. You have seen it is just different routing as the Professor was showing us I think.

Depending on which solenoids are open u either get cooling thru evaporators or heating thru Cabin Condensers.

Or like the Professor explains if you put a small amount of refrigerant though the evaporator at the same time as through the Cabin Condensers it dehumidifies the cabin. Like the Professor says "so your windscreen doesn't get all frosted up or even frozen on the inside".

This is the Heart of the Heat Pump, everything else is additional ways of saving even more energy by not wasting it.

Ok I will differ here and maybe call it the Culmination of the Heat Pump System. Because like the Professor explains it is just those heat sources he talks about that finally end up in the refrigerant that can be sent to the Cabin Condensers that we feel as heat in the cabin.

This is just my understanding so u don't have to accept it or believe it

I think the Professor will now give you a pass but we probably should ask him.

 

[Tronguy]

OK. We've got two Teslas in the household: A 2018 M3 LR RWD, which very definitely doesn't have a heat pump, and a 2021 MY LR, which does.

No question: The only ways on the 2018 M3 to get heat into the cabin is by:

1. Running an honest-to-golly resistive heater that warms the air. Which sucks electrical energy from the battery.
2. Taking warm "refrigerant" that runs through the motors and battery and, using that with a heat exchanger, warms the air going to the cabin.

One can tell that it's a cold day in the U.S. Northeast when the W-hr/mile on the 2018 M3 gets into the 350-400 W-hr/mile range. In the summer, it's more like 250 W-hr/mile. Winter time range goes down quite a bit as a result.

Now, let's talk about the 2021 MY. It does have a heat pump. Around here, what a heat pump fundamentally does is runs (in the winter) cold air through the radiator in the nose of the car. Good old gaseous, Freon-style refrigerant that is guaranteed colder than the outside cold air gets warmed up by the cold air passing through this radiator. This gas exiting this radiator has been warmed up a bit; it's either at the temperature of the external air or somewhat colder than the exterior air. The air leaving the nose radiator in the front of the car comes out colder than what went into said radiator. Implying that heat was extracted from the outside air.

This "warmed up" gas (pretty good for a gas that might be sitting at -20F) then goes into a compressor and comes out as a liquid that... is hot. Hotter than the cabin air, anyway. This is, by the way, the magic of the heat of evaporation of a material. Compress a gas into a liquid and it gets hotter; in the reverse direction, run a hot liquid through a nozzle, with a gas coming out, and the temperature of the gas is much colder than the liquid.

In any case, this hot liquid than passes through a second radiator. The source of air for this radiator is either the outside air or, if recirc is on, the cabin air. In any case, the air coming out of this radiator is now warm, while, at the same time, the liquid Freon-style refrigerant coming out of this radiator is cooled to be, say, warm. The warm air warms the cabin and defrosts the front and side windows.

One then runs the warm refrigerant through an expansion nozzle, liquid in, gas out - and the gas coming out will be dead cold. Much colder than than the outside air.

OK, so I may have lied a bit. It's possible that there's actually a total of three radiators: One in the nose, with Freon-style refrigerant; an intermediate one that has Freon-style refrigerant going to/from the compressor/nozzle and the nose radiator on one side, and the car coolant on the other; and a final radiator that has car coolant on one side and cabin air on the other.

But! The main point is that one is moving heat energy from (the admittedly frigid) air outside the car to the air in the cabin by playing silly buggers with refrigerant, refrigerant compressors, and nozzles. As one learns in Thermo 101 (for non mechanical engineers, don't-cha-know) this is a much more efficient process to heat air than by playing around with an electric, toaster-oven-style heater.

And it shows. In the same cold weather that's got my 2018 M3 doing 350 W-hr/mile, the 2021 MY hits around 300 W-hr/mile for the first couple of minutes of driving, then drops to 280 W-hr/mile. And stays there. In the summer, the MY gets around 250-270 W-hr/mile, so, there is a bit of a hit, but the range reduction is vastly less than with the older car.

So: This is not a drill. This is real data. Tesla says its got a heat pump in there in the newer cars. The data supports that.

 

[TrevRex]

OK. We've got two Teslas in the household: A 2018 M3 LR RWD, which very definitely doesn't have a heat pump, and a 2021 MY LR, which does.

No question: The only ways on the 2018 M3 to get heat into the cabin is by:

1. Running an honest-to-golly resistive heater that warms the air. Which sucks electrical energy from the battery.
2. Taking warm "refrigerant" that runs through the motors and battery and, using that with a heat exchanger, warms the air going to the cabin.

One can tell that it's a cold day in the U.S. Northeast when the W-hr/mile on the 2018 M3 gets into the 350-400 W-hr/mile range. In the summer, it's more like 250 W-hr/mile. Winter time range goes down quite a bit as a result.

Now, let's talk about the 2021 MY. It does have a heat pump. Around here, what a heat pump fundamentally does is runs (in the winter) cold air through the radiator in the nose of the car. Good old gaseous, Freon-style refrigerant that is guaranteed colder than the outside cold air gets warmed up by the cold air passing through this radiator. This gas exiting this radiator has been warmed up a bit; it's either at the temperature of the external air or somewhat colder than the exterior air. The air leaving the nose radiator in the front of the car comes out colder than what went into said radiator. Implying that heat was extracted from the outside air.

This "warmed up" gas (pretty good for a gas that might be sitting at -20F) then goes into a compressor and comes out as a liquid that... is hot. Hotter than the cabin air, anyway. This is, by the way, the magic of the heat of evaporation of a material. Compress a gas into a liquid and it gets hotter; in the reverse direction, run a hot liquid through a nozzle, with a gas coming out, and the temperature of the gas is much colder than the liquid.

In any case, this hot liquid than passes through a second radiator. The source of air for this radiator is either the outside air or, if recirc is on, the cabin air. In any case, the air coming out of this radiator is now warm, while, at the same time, the liquid Freon-style refrigerant coming out of this radiator is cooled to be, say, warm. The warm air warms the cabin and defrosts the front and side windows.

One then runs the warm refrigerant through an expansion nozzle, liquid in, gas out - and the gas coming out will be dead cold. Much colder than than the outside air.

OK, so I may have lied a bit. It's possible that there's actually a total of three radiators: One in the nose, with Freon-style refrigerant; an intermediate one that has Freon-style refrigerant going to/from the compressor/nozzle and the nose radiator on one side, and the car coolant on the other; and a final radiator that has car coolant on one side and cabin air on the other.

But! The main point is that one is moving heat energy from (the admittedly frigid) air outside the car to the air in the cabin by playing silly buggers with refrigerant, refrigerant compressors, and nozzles. As one learns in Thermo 101 (for non mechanical engineers, don't-cha-know) this is a much more efficient process to heat air than by playing around with an electric, toaster-oven-style heater.

And it shows. In the same cold weather that's got my 2018 M3 doing 350 W-hr/mile, the 2021 MY hits around 300 W-hr/mile for the first couple of minutes of driving, then drops to 280 W-hr/mile. And stays there. In the summer, the MY gets around 250-270 W-hr/mile, so, there is a bit of a hit, but the range reduction is vastly less than with the older car.

So: This is not a drill. This is real data. Tesla says its got a heat pump in there in the newer cars. The data supports that.

LOL . I think the Professor is saying there is just not one component of the heat pump or what he even calls one source of heat energy to make up "the heat pump" and so calls it a "Heat Pump System".

Those sources of heat include what he calls "Heat Source 3. The Radiator" and goes on to explain how the outside air even when cold has energy in it. That outside heat energy gets transferred to the coolant and gets extracted by the Chiller to end up in the refrigerant. Is that a type of heat pump? Yes as far as I know.

But is this the main source of the heat energy extracted when it's cold? He definitely says it's not the only source. I don't think he says or I may have missed it.

 

[Tronguy]

LOL . I think the Professor is saying there is just not one component of the heat pump or what he calls one source of heat energy to make up "the heat pump" and so calls it a "Heat Pump System".

Those sources of heat include what he calls "Heat Source 3. The Radiator" and goes on to explain how the outside air even when cold has energy in it. But this is just not the only source of energy. That outside heat energy gets transferred to the coolant and gets extracted by the Chiller to end up in the refrigerant. Is that a type of heat pump. Yes as far as I know.

But is this the main source of the heat energy extracted when it's cold, he definitely says it's not the only source, I don't think he says?

It’s a terminology problem, I think. When one gets down to it, all those heat exchangers (that is, things that vaguely look like radiators in old timey cars, and which have as their two input/output either air/coolant, air/refrigerant, or even coolant/refrigerant), pumps, compressor, nozzles, pipes, and valves are really all doing various flavors of One Thing: Moving Heat Energy From Point A to Point B.

Move heat energy out of the cabin and into the fresh air? Colloquially, people call that an air conditioner.

Move heat energy out of the motors and into the fresh air? People have seen that before with ICEs, and call it lots of things.

Move heat energy out of the motors and into the batteries? Sure, the system does that. And since the batteries dissipate energy, having the capability to move heat energy out of the battery into the fresh air, sure, why not?

Moving heat energy from the motors/batteries into the cabin? Heck, my (relatively ancient) M3 can do that, too, but it doesn’t do that very efficiently.

In newer Teslas, the ability to efficiently extract heat from the outside air and move it wherever it needs to go in the system has been added by dint of reversing what most people call the air conditioning system. And, Tesla being Tesla, they did this in a highly integrated, flexible way with that octovalve system.

But, if one squints a bit, one could say that the car is, “pumping” heat energy around. Saying it that way tends to put peoples’ mental knickers in a twist though, since “Heat Pump” is usually referred to those things with fans, outside radiators, and inside boxes that are used, with the right sets of valves and all, to both heat and cool houses.

What Tesla is doing is more complex than the simple case of a house: Yes, they’re moving heat energy into and out of the cabin air. But they’re also doing that, at the same time, in different directions, to the electric motors, batteries, in-car computer, and drive electronics, with the same integrated pile of hardware!

This is seriously cool stuff for the (mainly) mechanical engineering types who, traditionally, tend to live in this space. It’s no wonder that a professor at some university spends a significant amount of his class’s time digging through this tour-de-force to show the newbies How It’s Done.

 

[moa999]

It's small gains in efficiency, but at the end of the day a fair chunk of the heavy lifting still needs to be done by a good old resistive heater.

In a cold environment rather than just dumping 20°C inside air, and drawing in outside air at 0°C, your essentially pre-heating that outside air using the stored energy in the waste air and other heat sources in the car.

 

[GeoQuack]

It is unfortunate that Tesla calls it a heat pump. Because technically a heat pump is usually used for pumps which pump heat from cooler to hotter - technically maintaining a temperature difference between the two environments. The heat pump Tesla call as referenced above cannot do that. It cannot for example use waste heat and make other parts warmer than where they took the waste heat from. . Again it's real heat pump is the AC.

Yes it can. There is an evaporator (chiller) and condenser (LCC) in the coolant loop. Waste heat can be moved up in temperature gradient to somewhere that needs it.

For example, it uses less energy to take heat from the battery and move it to the cabin than getting it from the outside air. Therefore, if the battery is warm enough the octovalve runs in series radiator bypass and heat is moved from the battery to cabin, even if the cabin is warmer than the battery.

When connected to shore power and using preconditioning, range in cold environments is maximized by using the battery to store not only electrochemical energy, but heat energy as well in its substantial thermal mass.