Efficient Heating

[ItsNotAboutTheMoney]

I wouldn't worry too much about it being in UK. From what I saw it rarely goes below −10°C so you should be ok .

I remember those two days. Coldest I experienced in the UK was walking to school in the morning after an overnight low of, I think, -22°C. (I at least found a reference to -20.7°C). Of course, I now get to enjoy mornings like that every year.

Anyway, back on topic, I'd like to see more efficient heating. Heat pumps are a good idea, but they aren't going to help when it's extremely cold, which means they won't help minimum range. Insulation, however, should help any time you need climate control, so I hope that Tesla's working on that and on improved thermal systems that are able to make full use of waste heat generation. (Could be handy given the recent event in France ). Insulation, heat re-capture and heat pump for the full benefit.

 

[Saghost]

Anyway, back on topic, I'd like to see more efficient heating. Heat pumps are a good idea, but they aren't going to help when it's extremely cold, which means they won't help minimum range. Insulation, however, should help any time you need climate control, so I hope that Tesla's working on that and on improved thermal systems that are able to make full use of waste heat generation. (Could be handy given the recent event in France ). Insulation, heat re-capture and heat pump for the full benefit.

The other challenge with a heat pump is defrosting. One of the most common uses for heat in the car is clearing the windshield - for which car have for 30+ years used the A/C simultaneously with the heat to blow warm *dry* air at the windshield. The coils of the heat pump can be hot or cold, but not both at the same time...

One suggestions I've made a couple times for this situation is a dual Heat Pump - one with maybe three times the capacity of the other. This would let you heat with one while cooling the other for defrosting, and might eek out a little more efficiency overall - presumably Heat Pumps are slightly more efficient when running close to full capacity, so by having the smaller system run to maintain temperature should be a little more efficient than using a bigger system at fractional power. (This might also open the door to a specially designed high efficiency compressor for the little system.)

 

[MP3Mike]

AFAIK on the Model S currently the heat management system takes heat from the battery and or the motor and as it heats the gycol it can be used for cabin heat (via heatsink to other glycol loop) in addition to the heater.

While Tesla included that in their patent they didn't actually implement it on the Model S. (At least according to a number of reliable sources, and the cooling diag screen in the car.)

I think they found out that it wasn't very useful as they needed to keep the heat in the battery.

Both the battery and cabin have their own restive heating elements to heat the respective glycol loops when necessary.

 

[nigeldodd]

I remember those two days. Coldest I experienced in the UK was walking to school in the morning after an overnight low of, I think, -22°C. (I at least found a reference to -20.7°C). Of course, I now get to enjoy mornings like that every year.

Anyway, back on topic, I'd like to see more efficient heating. Heat pumps are a good idea, but they aren't going to help when it's extremely cold, which means they won't help minimum range. Insulation, however, should help any time you need climate control, so I hope that Tesla's working on that and on improved thermal systems that are able to make full use of waste heat generation. (Could be handy given the recent event in France ). Insulation, heat re-capture and heat pump for the full benefit.

Heat pumps will help minimum range. For a lot of the year in the UK it is not extremely cold but a base level of heating is needed. A heat pump would be well suited. You would get 3 or 4 times as much heat out as the energy consumed. I would like to know if heat pumps for actual heating will be included in the Model 3. The sales rep did not know.

 

[wycolo]

> My house is heated via heat pump... sucks ass in the winter. [Jeff K]

The earth is 55 degrees F in US on average at sufficient depth to minimize seasonal variations. The underground coil to operate your heat pump was possibly not buried deep enough. Also possibly needs to cover more square footage or contain more tubing length. Have you compared with a local over-built system? I only have experience with concrete floor thermal mass effects which are quite nice until near the end of the hot/cold seasons when they become neutral.
--

 

[JeffK]

The underground coil to operate your heat pump was possibly not buried deep enough.

It's not geothermal. It's a standard above ground heat pump. Heat pumps are well known not to work well when outside temperatures are significantly below freezing. The auxiliary heat supplied by a gas furnace has to compensate.

 

[melindav]

And being in a rainy area, how would a heat pump do for de-fogging windows? Generally speaking a defrost setting uses the air conditioner to dry the air being blown on the windows.

 

[Bangor Bob]

It's not geothermal. It's a standard above ground heat pump. Heat pumps are well known not to work well when outside temperatures are significantly below freezing. The auxiliary heat supplied by a gas furnace has to compensate.

Is your heatpump one of the Carrier-type units with the big square or round outdoor heat exchangers? Unfortunately, those have always had poor cold-temperature performance. And frankly, poor efficiency at all times compared to more recent designs as well. SEER => 30 and HSPF > 12 is available today, but the Carriers (and Trane, etc.) just can't reach that performance level.

I'm heating my homes with mini-split style air-exchange heat pumps, a mix of Fujitsu and Mitsubishi Electric - whichever was best-in-class at the time. They keep up down to about -10F, and keep putting out some heat down to around -20F. At -20F they still have a COP of 1. That is, they're no worse than resistance heating. Any temperature above that they're better. Both places have woodstoves for backup, but they don't get used too much anymore - really only on the coldest nights.

For a car, a couple resistive heating elements in the dash could serve as backup for defrosting and auxiliary heating for a good reversible heatpump. I'm certain Tesla would build a superb one if they decide to do it - they tend to ace the engineering challenges...

 

[JeffK]

Is your heatpump one of the Carrier-type units with the big square or round outdoor heat exchangers? Unfortunately, those have always had poor cold-temperature performance.

That's exactly what it is

 

[omgwtfbyobbq]

Aside from the creative math part, everything you said was in my post that you're quoting and correcting. I would argue that any math which results in more than 100% efficiency is by definition creative - in this case, it's correct for the application and the comparisons, but still odd.

(If you measure the efficiency of any part of the heat pump, it is less than 100% - like any physical process. It only becomes greater than 100% as a system because of the way we define the system boundaries.)

In the context of heat pumps, efficiency references converting electrical energy into thermal energy as opposed to motors and engines converting thermal or electrical energy into mechanical energy, so we see numbers greater than 100%, but the two processes aren't comparable. In my opinion, it makes more sense to look at all these processes from the POV of exergy.

Exergy - Wikipedia

 

[mspohr]

In the context of heat pumps, efficiency references converting electrical energy into thermal energy as opposed to motors and engines converting thermal or electrical energy into mechanical energy, so we see numbers greater than 100%, but the two processes aren't comparable. In my opinion, it makes more sense to look at all these processes from the POV of exergy.

Exergy - Wikipedia

Heat pumps move energy, they don't create it so most can move 4x the energy as the input

 

[wycolo]

> It's not geothermal. It's a standard above ground heat pump. [JeffK]

If there is a yard available for a geo coil then the efficiency will soar. Just mate a heat exchanger to the input side of your 'standard' unit plus the underground tubing + fluid and circulating pump. If no yard then you could possibly trench around the building just as effectively. Since you have not changed the existing heat pump at all, the improvements you see are purely from what you did.
--

 

[omgwtfbyobbq]

Heat pumps move energy, they don't create it so most can move 4x the energy as the input

Eggsactly! Engines convert (energy is conserved ) heat energy into mechanical energy, while heat pumps use mechanical energy to move heat around.

 

[CT200h]

Heat pump seem to be the way to go for conditioning the air in the cabin. Heated seats and steering wheel for conductive direct contact areas.
Nissan did some research at their Michigan research center on radiant heat for the footwell area. At one point I thought it might be a feature in the Leaf , guess it still could be part of Leaf gen 2.
I could see radiant footwell working well. I also thought about heated floor mats being helpful.

 

[JamesPolk]

Modern minisplit heat pumps with variable speed compressors have efficiency ratings up to 14-15 HSPF. This is 400-440% efficiency vs resistant heat at 100%. SEER ratings are also at 30+ now.

This would be probably impossible to squeeze into a car though and changes would need to be made.

 

[JeffK]

Modern minisplit heat pumps with variable speed compressors have efficiency ratings up to 14-15 HSPF. This is 400-440% efficiency vs resistant heat at 100%. SEER ratings are also at 30+ now.

This would be probably impossible to squeeze into a car though and changes would need to be made.

What is their efficiency at -20 degrees? Can they actually blow hot air vs really slowly increasing the temperature of the cabin?

If it takes 20-30 minutes for the cabin to warm up then it's useless to many people.

 

[Jayc]

Model 3's cabin heating/cooling system could be more efficient by design so we may not require heat pumps after all.

http://jalopnik.com/we-may-have-an-interesting-leak-about-the-model-3s-inte-1791848511

All speculation of course.

 

[JeffK]

Model 3's cabin heating/cooling system could be more efficient by design so we may not require heat pumps after all.

http://jalopnik.com/we-may-have-an-interesting-leak-about-the-model-3s-inte-1791848511

All speculation of course.

The author simply never watched any of the videos from the Model 3 launch... this has been known since day 1.

Here's a quote from the article:

Initially, I assumed that the dash design just didn’t have them yet because Tesla hadn’t finished designing them. According to our source, I was wrong:

Clearly the author did no research.

 

[Jayc]

Clearly the author did no research.

And I didn't realise there was a separate thread here for the jalopnik link.