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Heat pump

Booga

Member
Apr 21, 2016
466
203
Florida
Sorry, if "if and buts were candy and nuts we would all have a merry xmas"
I am sorry, "I think" and "maybe" just not my form of "Data Lets see real data
over a range of temps before we all become one of those people.
The data is attached and the source linked below. If it's anything like the Nissan Leaf, there should be an improvement in cold temperatures. The full article probably has more detail, but the range increase was 13% at -10C (14F).

Unitary Thermal Energy Management for Propulsion Range Augmentation (UTEMPRA) (Technical Report) | OSTI.GOV

As you get colder, this benefit decreases, because it has to revert to other forms of heat generation outside of the heat pump.
 

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sightman

Member
Jul 25, 2020
112
124
Quakertown, PA
So is the heat pump contributing to the increased range? I thought it would be more than the ~10%. I have a Fujitsu mini split heat pump for my finished basement and that thing is crazy efficient. 1.2kw when running and blowing 120F air at 10F outside temps
 

MP3Mike

Well-Known Member
Feb 1, 2016
15,805
35,204
Oregon
So is the heat pump contributing to the increased range? I thought it would be more than the ~10%.

It does, but there is basically no impact in warmer weather driving so the range is sort of between. It might help more than 10% in the winter and 0% in the summer. The reported range is all based on the EPA test procedures, not real life situations.
 
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SageBrush

REJECT Fascism
May 7, 2015
12,388
15,315
New Mexico
So is the heat pump contributing to the increased range? I thought it would be more than the ~10%. I have a Fujitsu mini split heat pump for my finished basement and that thing is crazy efficient. 1.2kw when running and blowing 120F air at 10F outside temps
1. Winter heating efficiency only helps when it is cold ...
2. The car is always spending energy on things that have nothing to do with heating, e.g road friction and air resistance.

Lets plug in some numbers:
Say winter is 1/3 of the year
Say your summer consumption is 250 Wh/mile and the winter consumption is 350 Wh/mile in cars without a heat pump
Then winter adds 100 Wh/mile. Say the heat pump drops the winter component consumption to 30 Wh/mile

The pre-heat pump car averaged (2*250+350)/3 = 283 Wh/mile year round
The heat-pump car averages (2*250+280)/3 = 260 Wh/mile

That works out to a 8% drop in annual energy consumption.
This does not look like a big deal overall, and it is not. But it sure helps preserve range in the winter.
 
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Mutant

Member
Oct 20, 2020
44
53
Waterloo, ON
It does, but there is basically no impact in warmer weather driving so the range is sort of between. It might help more than 10% in the winter and 0% in the summer. The reported range is all based on the EPA test procedures, not real life situations.
In real world condition that is not fully correct for the Tesla heat pump system. With the combination of the octovalve and heat pump there are warm weather advantages covered in an article on insideEvs Tesla Model Y Heat Pump Details Infrequently Discussed By The Media

There are 15 different modes of operation of redistributing heat/cooling between cabin, battery and drive unit which are tied to together via octovalve. Previous (non heat pump) model 3 has the cabin conditioning isolated from the battery/drive unit thermal management.

Mode 7 in the article is a condition during warm days that increase efficiency where the cabin is hot from sitting in the sun but the battery needs to be warmed in preparation for supercharging. So excess heat from the cabin can be directed to the battery through octovalve (very efficient with a COP I would suspect of 4) . With the old model 3, either external resistive heater or locked rotor (same as resistive heater with a COP 1) would be used to warm battery.

Just for reference for those that don't know, COP stands for Coefficient of Performance which is a measure of thermal efficiency. So COP of 1 is 100% efficient (1 kW input provides 1 kW of heat) and a COP of 4 is 400% efficient (1 kW input provides 4 kW of heat).
 

SageBrush

REJECT Fascism
May 7, 2015
12,388
15,315
New Mexico
there are warm weather advantages ...
Yep, but your example in interestingly enough of little direct advantage to most car owners.

  • An average Tesla owner uses Superchargers for ~ 1/10 of their miles. I think the pre-charge routine is about one kWh, so the average reduction in energy use is ~ 100 Wh per 300 miles or about 1/3 of a Wh per mile. We are talking rounding error here.
Don't get me wrong -- I think the Octovalve is brilliant and I love energy conservation. I'm just pointing out that in the "real world" owners will appreciate the new heating system in the winter.
 
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Mutant

Member
Oct 20, 2020
44
53
Waterloo, ON
Yep, but your example in interestingly enough of little direct advantage to most car owners.

  • An average Tesla owner uses Superchargers for ~ 1/10 of their miles. I think the pre-charge routine is about one kWh, so the average reduction in energy use is ~ 100 Wh per 300 miles or about 1/3 of a Wh per mile. We are talking rounding error here.
Don't get me wrong -- I think the Octovalve is brilliant and I love energy conservation. I'm just pointing out that in the "real world" owners will appreciate the new heating system in the winter.

I agree that the majority of owners that primarily use in home chargers will probably rarely see a measurable benefit (except summer long road trips) with this mode. However there are some owners that do not have access to in home charging (renters/apartment dwellers) that use superchargers for the majority of their charging needs. They may see a small improvement in overall energy consumption. It would be interesting to see if it might be more beneficial to park their vehicle in full sun before visiting a supercharger.

What annoys me is all the arguments that a heat pump only improves efficiency in limited temperature range. If Tesla was only providing heat pump tied exclusively into thermal regulation of the cabin, this would be true. But Tesla has tied the heat pump with octovalve into the thermal management of the entire vehicle gaining efficiency in multiple conditions.

For example on extremely cold days (-10 deg C) where the heat pump is forced to operate like a resistive heater (COP of 1), there is still the possibility of drawing heat from the battery and drive unit to heat the cabin thus reducing demand on the inefficient operation of the heat pump. This would especially be true if the driver is more aggressive (fast acceleration/deceleration) as the battery and drive unit would build more waste heat that can be transferred to the cabin. Note, I am not suggesting driving more aggressively will result in longer range than less aggressive driver (I wish but kinda defies the laws of physics) just that new heat pump system in such conditions will be more efficient than old non-pump system.
 
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SageBrush

REJECT Fascism
May 7, 2015
12,388
15,315
New Mexico
I agree that the majority of owners that primarily use in home chargers will probably rarely see a measurable benefit (except summer long road trips) with this mode.
If I'm thinking about this correctly, long trippers will also not notice the heat_pump/Octavalve benefit as it relates to Supercharging: During the driving to the next Supercharger the range estimate will not include the Supercharger pre-heating benefit. It will reduce Supercharging time -- about 1 kWh worth. What is that nowadays, about 15 - 20 seconds ?

Tesla driving bank robbers are licking their chops.

Nitpicking aside,
I hope you realize that I am in your camp -- the system-wide heat integration is fantastic.
Your tendency to take personally the lack of appreciation for the superb engineering makes me think you are a U Waterloo grad. ;)
 
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Mutant

Member
Oct 20, 2020
44
53
Waterloo, ON
If I'm thinking about this correctly, long trippers will also not notice the heat_pump/Octavalve benefit as it relates to Supercharging: During the driving to the next Supercharger the range estimate will not include the Supercharger pre-heating benefit. It will reduce Supercharging time -- about 1 kWh worth. What is that nowadays, about 15 - 20 seconds ?

Tesla driving bank robbers are licking their chops.

Nitpicking aside,
I hope you realize that I am in your camp -- the system-wide heat integration is fantastic.
Your tendency to take personally the lack of appreciation for the superb engineering makes me think you are a U Waterloo grad. ;)

My frustration was not necessarily directed at you but more general at those that view the upgrade as simply just the addition of a heat pump where there is so much more to the upgrade.

I am an engineer but not a U of W grad FYI ;)
 

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