Why does Tesla use a Resistance Heater instead of Heat Pump

[ThosEM]

There has never been a heat pump deployed as a heater that didn't have an auxiliary source of heat to provide for ultra-cold temperatures. I personally favor a heat pump with gas fired auxiliary heat instead of resistance heat. It could be biogas and hence carbon neutral. Flame is much better for heat and electricity is much better for turning shafts.

 

[AWDtsla]

There has never been a heat pump deployed as a heater that didn't have an auxiliary source of heat to provide for ultra-cold temperatures.

I'd like to welcome you to the year 2017. Where they certainly are.

 

[ThosEM]

I'd like to welcome you to the year 2017. Where they certainly are.

I hate to be snippy, but since you were insultingly sarcastic, details or it didn't happen.

 

[SmartElectric]

Like I said. I own a Tesla and Smart ED. They both have temperature managed battery packs and use resistive heating. I can do all my commute and errands in the Smart just as well as the Tesla.

But I get your point even if I don't think it makes any difference to my lifestyle. I charge up overnight on cheap surplus electricity here in Ontario and dont frankly have any concerns on the Tesla efficiency for my needs.

I think your concern is valid but misplaced. Tesla made perfectly sensible choices based on the details I posted earlier.

If you do lots of short trips in cold weather, you'll still be able to get everywhere you need to go. Now it's just a question of a few pennies difference on how much energy that took...

 

[AWDtsla]

I hate to be snippy, but since you were insultingly sarcastic, details or it didn't happen.

Take On Winter: Keep Your Home Warm With Hyper-Heating™ Technology
Extra Low Temperature Heating: Halcyon™ MULTI-ROOM MINI-SPLIT SYSTEMS - RESIDENTIAL - FUJITSU GENERAL United States & Canada

 

[mongo]

I'd like to welcome you to the year 2017. Where they certainly are.

Sure, you can install a unit without aux heat. But your house will freeze if the temperature dips too low (-15 F/ -25 C in the case of the unit you posted). On Feb 20,2015 average temp for the entire state of Michigan at 8 am was -18.5 F.

 

[jankratochvil]

You have a "P" 90D, the 90D had 10% more range than your car

Not more range, about the same range: Why do PxxD have lower range than xxD?

 

[AWDtsla]

Sure, you can install a unit without aux heat. But your house will freeze if the temperature dips too low (-15 F/ -25 C in the case of the unit you posted). On Feb 20,2015 average temp for the entire state of Michigan at 8 am was -18.5 F.

No, that's not how it works. Read the specs harder. I don't even have hyperheat models I've seen night time temps dip to -13F, and I don't appear to be frozen. I also don't have backup heat. According to some AC techs that know their stuff, you can pretty much linearly extrapolate the capacity down from even the lowest spec'd temp. It does not magically stop heating at -whatever F.

 

[mongo]

No, that's not how it works. Read the specs harder. I don't even have hyperheat models I've seen night time temps dip to -13F, and I don't appear to be frozen. I also don't have backup heat. According to some AC techs that know their stuff, you can pretty much linearly extrapolate the capacity down from even the lowest spec'd temp. It does not magically stop heating at -whatever F.

It does stop if the controller reads an outdoor temp of less than its design rating or too low of a supply temp from the evaporator (self protection to prevent liquid in the compressor).
I looked further at the owner's and installation guides, but I do see where it indicates that it operates below -15 F.

The thermal mass of a house can coast for a time. The use case you describe of warming a vehicle from a cold soak is different. If it is below the safety/ design rating of the system, there will be no heat.

Can system operation be extended lower? Sure, but there will be trade offs.

 

[SmartElectric]

Not more range, about the same range: Why do PxxD have lower range than xxD?

Nice anecdotal information.

But, if I'm wrong, then both Tesla and EPA (who agree) are wrong.
So, either your anecdotal information is definitive, or perhaps it isn't, but stating I'm wrong for using published factually gathered information is a bit rich.

As reported by manufacturer, the PxxD cars are less efficient than non "P" cars.
Bjorn Nyland has also confirmed this with hundreds of thousands of km of driving in a wide variety of Tesla models.

 

[wdolson]

Not more range, about the same range: Why do PxxD have lower range than xxD?

I note he has a 2015 P85D and a 2017 75D. They did something around the time of the refresh to improve the efficiency. The same version before and after the refresh are different.

There is also very little difference in real capacity between the new 75 and old 85 packs. The original 85KWh pack was really about 81 KWh and the 75 KWh pack is really close to 75 KWh. The P85D weighs more than the 75D and his P85D has an older battery, 'm surprised the 75D doesn't get more range.

 

[ThosEM]

Take On Winter: Keep Your Home Warm With Hyper-Heating™ Technology
Extra Low Temperature Heating: Halcyon™ MULTI-ROOM MINI-SPLIT SYSTEMS - RESIDENTIAL - FUJITSU GENERAL United States & Canada

I don't think I'm the only person to whom that is news. And it sounds too good to be true. The limits of heat pumps are thermodynamic, that is physics based, and not subject to technology improvements. If you are aware of geothermal or ground source heat pump systems, you know that a big investment is necessary to overcome the limitations without an auxiliary heat source, and for that matter, even geothermal systems have auxiliary heat, despite hardly ever needing to use it.

For my money, I'd need to see a second source on the Mitsubishi technique, which is not adequately explained by their sales material that you pointed to.

 

[AWDtsla]

that is physics based, and not subject to technology improvements.

As a reminder, absolute zero is -459.67F. There is plenty of heat in the air at any place on Earth. This is a technology limitation not a physics one.

For my money, I'd need to see a second source on the Mitsubishi technique, which is not adequately explained by their sales material that you pointed to.

I have the previous generation (the one only rated down to -5F) in my house without backup heat, there really isn't a problem, will continue to heat even well below -5F. Maybe find some owners in your area and ask them.

Also, you'll note that I included two different manufacturers, not just Mitsubishi.

 

[mongo]

As a reminder, absolute zero is -459.67F. There is plenty of heat in the air at any place on Earth. This is a technology limitation not a physics one.

Sure, anything above absolute zero has heat energy that could be transferred to another medium (assuming that transfer medium has had sufficient heat extracted from it that it is even lower in temperature than the heat source). That medium could then be compressed to such an extent that its temperature is now above the material you are trying to heat. Oxygen can be liquified (<90 K) by transfering energy from it.

However, assuming you had a transfer fluid to accomplish this, your COP most likely would have dropped to (or below) 1.

 

[AWDtsla]

However, assuming you had a transfer fluid to accomplish this, your COP most likely would have dropped to (or below) 1.

It's actually difficult to get below a COP of 1, as all 1 means is that the input electrical energy is delivered as heat, which is going *somewhere*, hopefully inside, minus mostly the fans converting electricity to kinetic energy of air.

 

[AWDtsla]

9 pages in and we're still arguing over if it's even *possible* even though there are products on the market *now* that you can buy and people use that do the job, including myself.

This might as well be any other forum on the internet, and the argument that EV's can't possibly work and that Tesla is just a scam to get tax subsidies. Same argument, different subjects.

 

[mongo]

It's actually difficult to get below a COP of 1, as all 1 means is that the input electrical energy is delivered as heat, which is going *somewhere*, hopefully inside, minus mostly the fans converting electricity to kinetic energy of air.

I was allowing for possibly that the system was losing energy to the near absolute zero heat source.

edit: due to defrost cycles

 

[mongo]

9 pages in and we're still arguing over if it's even *possible* even though there are products on the market *now* that you can buy and people use that do the job, including myself.

This might as well be any other forum on the internet, and the argument that EV's can't possibly work and that Tesla is just a scam to get tax subsidies. Same argument, different subjects.

I don't think anyone is arguing if it is possible, rather whether it is practical. A discussion of practicality requines discussion of the conditions where the system does not work as well as the alternative. See for example discussions on home heat pump defrost cycles during cold windy time periods

My POV, qualitative response, is that heat pumps are great for houses in cold/ temperate regions, not as much for arctic/ frigid places. For vehicle use, I do not believe that the cost and complexity that a heat pump adds provides sufficient benifits to justify it's inclusion. Basically, I don't see the operational range and duty cycle adding enough benifit. The HVAC will still require an electtic heater sufficient for the full heating load. The HP will add cost and increases the failure rate, it may save energy based on drive cycle and environment.
To give a quantitative response requires the operating point for the fleet of vehicles along with the design implementation...

 

[wycolo]

"Five feet down, ground temperatures lag three months behind seasonal air temperatures. The lag is six months at 15 feet. Soil temperatures are constant below 30 feet, and, incidentally, about equal to the average annual air temperature." *

15 feet deep would therefore be perfect for home geothermal due to this ideal 6 month lag giving the system positive reinforcement for both the heating season and the A/C season. Now you just have to match the house load to the surface area of the underground pipe you plan to bury. Then buy a heat pump that will handle that.

* Chicago Trib 24 Sept 2011
--

 

[AWDtsla]

I do not believe that the cost and complexity that a heat pump adds provides sufficient benifits to justify it's inclusion.

Hardware complexity is adding a reversing valve to the compressor loop, and sizing coils appropriately. Also might want to add resistive defrost, but not required. Rest is in software.