Heat pumps

Black_Knight · 22-08-2020 5:01pm #1

It comes up regularly, how X doesn't have a heat pump, and shame on them for not doing so. Are they really that big a deal in Irish climates?

I believe the Ioniq has one, but in the depths of winter i'm just glad it has a PTC heater, which from what I hear is what gives it the speedy warmth as soon as you turn on the car.

So. Much ado about nothing, or legitimately something of value to EVs in Ireland?

KCross · 22-08-2020 5:14pm

Very important for short range EVs. Largely irrelevant for the long range ones.

It would be ideal if they all had them but with it usually being about €1k+ to add it I’d rather have the money in my pocket if it was a long range EV I had.

Black_Knight · 22-08-2020 5:28pm

KCross wrote: »

Very important for short range EVs. Largely irrelevant for the long range ones.

It would be ideal if they all had them but with it usually being about €1k+ to add it I’d rather have the money in my pocket if it was a long range EV I had.

So my understanding is that they're slower to warm the cabin, but more efficient at doing it, hence why longer range EVs benefit from them, but... when you've a longer range EV, surely the extra range you get kinda removes the need for a heat pump to eeek out an extra few km. And in a short range EV, a slowly warming heat pump would drive me crazy if i'm just tipping about in a car that never gets warm.

Agreed with the 1k in my pocket. I'll pay for range already with a bigger battery, no need to pay again for a heat pump to give me an extra few km.

KCross · 22-08-2020 5:59pm

Black_Knight wrote: »

So my understanding is that they're slower to warm the cabin, but more efficient at doing it, hence why longer range EVs benefit from them, but... when you've a longer range EV, surely the extra range you get kinda removes the need for a heat pump to eeek out an extra few km. And in a short range EV, a slowly warming heat pump would drive me crazy if i'm just tipping about in a car that never gets warm.

You’ve it the wrong way around. Short range EVs benefit not long range ones.

And they’re not slow to heat. Faster than every ICE.

Black_Knight · 22-08-2020 6:44pm

KCross wrote: »

You’ve it the wrong way around. Short range EVs benefit not long range ones.

And they’re not slow to heat. Faster than every ICE.

Are they not slower than the PTC heater in the ioniq?

Faster than ice sure, but slower than other alternative EV cabin heating solutions?

KCross · 22-08-2020 6:50pm

Black_Knight wrote: »

Are they not slower than the PTC heater in the ioniq?

Faster than ice sure, but slower than other alternative EV cabin heating solutions?

It takes about 30s or so for the heat pump to “spin up” and give its heat but once it’s pumping heat it’s as good as a PTC but would typically use about a third or quarter of the energy of a PTC.

After that it’s down to the size of the heat pump. For example, a 5kW PTC will, of course, heat the car quicker than a 3kW heat pump but that’s a design decision not that a PTC is quicker to heat the cabin than a heat pump.

At very low air temps the heat pumps are also not great but for our climate they are fine.

Kramer · 22-08-2020 7:30pm

Black_Knight wrote: »

It comes up regularly, how X doesn't have a heat pump, and shame on them for not doing so. Are they really that big a deal in Irish climates?

So, say your car uses a resistive heater. On a coldish autumn/winter day, it uses 3kW, on average.
You embark on a 180km drive, mostly regional & urban roads, so it takes 3 hours @ 60km/h average.

You'd use 9kWh worth of energy for cabin heating :eek:.

Now, considering your Ioniq has a net capacity of 28kWh - would it be acceptable to use 1/3rd of your battery, just for heating? That would leave you just 19kWh for range.
Also consider when you charge on DC - take Ionity for example. You'd be paying upwards of €0.80/kWh for those 9kWhs used for heating on your trip - €7 for heating - likely derived from fossil fuels at a power station too.

Considering the environmental aspects - the government are incentivising houses to install heat pumps, not 2 bar electric fires, energy saved is energy saved - good for the planet.

Not having the most efficient heating system in a new EV, but choosing an antiquated, resistive heater, is like having old, timber, single glazed windows in a house or old tungsten filament bulbs everywhere - it's not efficient.

Of course, many will say just use the seat heaters & wear a jacket & wooly socks - that's certainly the most efficient way I suppose :pac:.

Since Tesla fitted a heat pump in the Model Y - you'd think they practically invented the concept whereas it's been taken for granted in the Leaf for the last 10 years!!

Black_Knight · 22-08-2020 10:08pm

KCross wrote: »

It takes about 30s or so for the heat pump to “spin up” and give its heat but once it’s pumping heat it’s as good as a PTC but would typically use about a third or quarter of the energy of a PTC.

After that it’s down to the size of the heat pump. For example, a 5kW PTC will, of course, heat the car quicker than a 3kW heat pump but that’s a design decision not that a PTC is quicker to heat the cabin than a heat pump.

At very low air temps the heat pumps are also not great but for our climate they are fine.

Perhaps I don't know how good I have it in the Ioniq.

So what about the Niro. Some have a heat pump (nordic countries). What's their reported range vs Irish/UK eNiros? Is it significant?

3d4life · 22-08-2020 11:33pm

Kramer wrote: »

.... On a coldish autumn/winter day, it uses 3kW, on average....

That seems very high. I mean, if you put a 2kW fan heater inside an Ioniq it would heat the inside up in no time. Once its warm heat requirement will be low ( just have to balance the heat loss ).

Nevertheless I would be muchly in favour of heat pump or some such over resistive. ( M3 & MY do some cute things with regard to heating and cooling.)

liamog · 23-08-2020 1:01am

Personally I like a car to have a heat pump. It just makes the range a bit more predictable in the winter.
I saw a rule of thumb that resistive heating results in a 40% drop in range at winter, versus a 20% drop with a heat pump.

Busman Paddy Lasty · 23-08-2020 8:23am

Black_Knight wrote: »

Perhaps I don't know how good I have it in the Ioniq.

So what about the Niro. Some have a heat pump (nordic countries). What's their reported range vs Irish/UK eNiros? Is it significant?

Noticed a 15% drop on the GoM with heat on. As stated by another poster the energy consumption tapers off as journey progresses. Even in winter I've seen the difference down to 3km (off 200km) toggling heat on/off, just not in the first 20km of driving.

Eco mode restricts the peak consumption of the heater too. No home charger yet so if I had morning preheating the heat cost would be way less. Some short early morning trips are 30kWh/100km because 40% of that is heating up cabin on the driveway before moving at all.

Due to heating only, no way would 40% reduction be seen in this climate especially as most will have preheating. The 3kW scenario is a different ball of wax as it's only now 5% of usable capacity per hour versus >10% in Ioniq.

KCross · 23-08-2020 9:49am

liamog wrote: »

Personally I like a car to have a heat pump. It just makes the range a bit more predictable in the winter.
I saw a rule of thumb that resistive heating results in a 40% drop in range at winter, versus a 20% drop with a heat pump.

Those percentages would need context though for them to be rules of thumb.
I.e what range car do they apply to.

That’s the main thing, it will take X kWh’s to heat the cabin. That X will be a higher percentage of a 24kWh car than a 64kWh car.

liamog · 23-08-2020 2:56pm

KCross wrote: »

Those percentages would need context though for them to be rules of thumb.
I.e what range car do they apply to.

That’s the main thing, it will take X kWh’s to heat the cabin. That X will be a higher percentage of a 24kWh car than a 64kWh car.

How is a percentage drop affected by a rule of thumb?

It doesn't take x kWh to heat the car, it takes x kWh per minute to first raise the temperature to a desired level and then to maintain that level of heat. The efficiency of the heating system really comes into it's own during journeys longer than 10 mins. Generally speaking we can approximate distance to time for the purpose of a rough percentage drop.

KCross · 23-08-2020 4:45pm

liamog wrote: »

How is a percentage drop affected by a rule of thumb?

Because your rule of thumb is based off range and range is directly proportional to the battery capacity, not the efficiency of the heating system. It also takes alot more energy to get the cabin up to temperature than to maintain it, so unless you are going to devise some specific journey to prove your point its not a good rule of thumb to use across the board.

Basically I cant see how that rule of thumb could be applied equally to all EV's from a 120km short range Leaf to a 450km long range Niro.

Feel free to give a worked example and I'll debate it!

23-08-2020 6:40pm

A heat pump isn't very efficient from under 6 degrees C and from 3 Degrees C it's practically useless, a small HP in a car that is.

The greatest effect to range in Winter will be cold battery, wind and wet roads.

liamog · 23-08-2020 8:45pm

KCross wrote: »

Because your rule of thumb is based off range and range is directly proportional to the battery capacity, not the efficiency of the heating system. It also takes alot more energy to get the cabin up to temperature than to maintain it, so unless you are going to devise some specific journey to prove your point its not a good rule of thumb to use across the board.

Basically I cant see how that rule of thumb could be applied equally to all EV's from a 120km short range Leaf to a 450km long range Niro.

Feel free to give a worked example and I'll debate it!

Ok an example. A car comes with two batteries, 30kWh and 60kWh.
The cars travel at 100km/h and uses 15kWh/100km, with no heating.
The cars have a range of 200km and 400km.

The car is available with two heating systems a heat pump (hp) and a resistive heater (ptc). The intent is to maintain a temperature of 22C. The heat pump requires 2kW/h to maintain that temperature, the resistive heater requires 6kW/h.

Over that 100km in 1 hour, the energy used is now 17kWh (hp) and 21kWh (rtc). That gives a range at a 100km as follows.

30kWh Car - 176km (hp), 142km (ptc)
60kWh Car - 352km (hp), 285km (ptc)
The ratios have of range reduction have stayed the same, allowing for a percentage reduction to be used as a rule of thumb whatever the overall capacity of the battery.

I know you are focusing on the initial energy to bring the cabin up to temperature, whereas I'm focusing on the energy required to maintain that temperature. Both factors are important, but I think when measuring impact on battery it's better to focus on energy usage over a period of time, as the impact on range is more likely to be felt on a singular journey, and you are not going to let the car return to ambient temperature every time you stop.

liamog · 23-08-2020 9:15pm

Hopefully soon, we'll get a proper sample, just need 6 ID.3s every heat pump and battery combination

KCross · 23-08-2020 11:02pm

liamog wrote: »

Ok an example. A car comes with two batteries, 30kWh and 60kWh.
The cars travel at 100km/h and uses 15kWh/100km, with no heating.
The cars have a range of 200km and 400km.

The car is available with two heating systems a heat pump (hp) and a resistive heater (ptc). The intent is to maintain a temperature of 22C. The heat pump requires 2kW/h to maintain that temperature, the resistive heater requires 6kW/h.

Over that 100km in 1 hour, the energy used is now 17kWh (hp) and 21kWh (rtc). That gives a range at a 100km as follows.

30kWh Car - 176km (hp), 142km (ptc)
60kWh Car - 352km (hp), 285km (ptc)
The ratios have of range reduction have stayed the same, allowing for a percentage reduction to be used as a rule of thumb whatever the overall capacity of the battery.

Well worked example, fair play!
I'm not sure we are talking about the same thing though.

- You have extrapolated the range from a 100km journey and applied that to the entire range of the car. That example only works if you are travelling the full range of the car in one session.

In reality you wont be doing that everyday. In reality you will be making multiple journeys (e.g. to/from work, shop run later, gym etc) that require the cabin to be brought up to temperature multiple times. Your example only assumes one session.

- You also doubled the battery capacity and simply doubled the range. That obviously wont be reality either and I know you did that to keep the math simpler but it affects your rule of thumb math

- The heat pump itself will have different efficiencies depending on outside temperature. The HP will give very different results coming from 0°C and 10°C. Its efficiency is not linear. That alone would make the rule of thumb hard to rely on.

Hopefully soon, we'll get a proper sample, just need 6 ID.3s every heat pump and battery combination

I wonder is there real world data for the Leaf as the entry level XE model has no heat pump. Would be easy enough to compare it to the one that does, at different temperatures.

We dont need to labour the point anyway. Its better to have a HP than not but if it costs €1k+ to add its hard to justify it in this country, unless you have a short range EV.

Just using your example.... getting 142km instead of 200km matters alot more in that EV than getting 285km's instead of 400km. The longer range EV still has plenty left in the tank for daily use. The short range EV not so much.

liamog · 23-08-2020 11:53pm

Yeah exactly, it mostly comes down to the use cases, if your use case is lot's of short journeys then obviously you'll spend more energy getting the car up to temperature each time.
Whereas for myself, the only time I'm really worried about range is when doing a long singular journey so that's when I'm most worried about the energy usage and prefer a simple rile of thumb.

Right now I treat our Ioniq as 180km in summer and 150km in winter. We get much better range than that most of the time, but not on the occasions where I need the range.
The e-Up! with it's PTC heater is around 120km in summer and 70km in winter. The heating impacts the range to a much higher percentage than the Ioniq.
From researching other cars, the ones with heat pumps seem to maintain there range to a much higher degree, so based on my own experience and research I came up with my rule of thumb

.

It would be great to see a proper experiment with two cars on the same trip, identical except for a heat pump.

Kramer · 24-08-2020 12:10am

KCross wrote: »

Its better to have a HP than not but if it costs €1k+ to add its hard to justify it in this country

But the environment! Think of the environment!

Spend the extra & get the heat pump. You can't put a price on the feelgood factor & kudos, knowing you'll save 48.26 penguins & 0.76 polar bears over the lifetime of the car :pac:.

KCross wrote: »

if it costs €1k+ to add its hard to justify it in this country

You could use that reasoning to justify any petrol or diesel over a BEV too though, or indeed buying a Tesla over an eNiro etc.

Heat pumps are better for the environment, more efficient & ultimately, the way to go, as evidenced by Tesla finally adopting them in the Model Y.

liamog · 24-08-2020 12:18am

Kramer wrote: »

Heat pumps are better for the environment, more efficient & ultimately, the way to go, as evidenced by Tesla finally adopting them in the Model Y.

Tesla adopted the heat pump because of the impact on range in winter. Sunny Californians don't need them, but if you live in America's hat then they are good to have. EVs don't have to be better for the environment, that's just a handy side effect!

Redlim · 24-08-2020 12:44am

Here's a smaller battery Kona v Kona winter test with English subtitles - 1 with and 1 without heat pump. Same tyres and even same colour to avoid any solar gains! Typical Irish winter temperatures also.

About 5% or 12 km advantage with the heat pump when driving approx 90km/h indicated, including the initial cabin heating to 23 degrees. Test started at 5 degrees outside temperature.

A second test at 120km/h with cabin set to 19 degrees was basically a draw as heating was no longer needed. Heat loss was very low from the already warm cabin even at higher speed. Outside temp of 10 degrees for this part.

https://m.youtube.com/watch?v=fR0mNbIccUw

Busman Paddy Lasty · 24-08-2020 7:06am

liamog wrote: »

The e-Up! with it's PTC heater is around 120km in summer and 70km in winter. The heating impacts the range to a much higher percentage than the Ioniq.

It would be great to see a proper experiment with two cars on the same trip, identical except for a heat pump.

Holy sh1te that's quite a drop in range from The Yorkshireman.

But how much of that is cold battery, wind and wet roads? eNiro, as well as all EVs I believe, winter range drops anyway without using heater. eNiro is like:

440km Summer no heating
410km Winter no heating
360km Winter with heating

20% drop in range but only half-ish due to PTC heater. There might be other K Triplet drivers that get better range in winter if they preheat cabin.

krissovo · 24-08-2020 9:59am

If its an option the Irish will not pay for it, as a general rule the only options you find on Irish cars is to make it look like a sporty version like the AMG or M-sport packs.

When we asked for a heat pump on my wifes I3 the salesman had a look of shock and then questioned whether it was a real option. Personally if a heat pump was an option in any future car purchase I would have it. I have not had any issues with heat pumps to date in our cars even in a cold winter.

24-08-2020 9:59am

Cold temps, colder air takes more energy to cut through the colder it gets add to that Wind and wet roads and this is the greatest impact to range along with the ability of the battery to store less energy.

There's no way to really calculate the value of a heat pump without proper current sensing on the wires directly to the heap pump and electric heater.

Below 5 Deg C there's no real advantage to the HP any more and around 3 degrees and below it's next to useless. That's what I observed in the Leaf, power consumption went up considerably below 5 Deg C.

24-08-2020 10:01am

krissovo wrote: »

If its an option the Irish will not pay for it, as a general rule the only options you find on Irish cars is to make it look like a sporty version like the AMG or M-sport packs.

When we asked for a heat pump on my wifes I3 the salesman had a look of shock and then questioned whether it was a real option. Personally if a heat pump was an option in any future car purchase I would have it. I have not had any issues with heat pumps to date in our cars even in a cold winter.

I wouldn't let the Heat Pump be the deciding factor on whether you bought the car, in reality with the range of todays cars it's meaningless anyway, better off with an upgraded Stereo or better driver aids.

KCross · 24-08-2020 10:33am

Its better to have a HP than not but if it costs €1k+ to add its hard to justify it in this country

Kramer wrote: »

You could use that reasoning to justify any petrol or diesel over a BEV too though, or indeed buying a Tesla over an eNiro etc.

Heat pumps are better for the environment, more efficient & ultimately, the way to go, as evidenced by Tesla finally adopting them in the Model Y.

That's not the same comparison really.

If you have a long range EV and you rarely drive the full range of the car in one session, having a HP will be meaningless to you, particularly in this country.

For example, lets say you do 150km's per day for your normal daily driving (commuting, school runs etc), thats a total of 36k km's so a decent amount of driving and lets say you have a 450km+ EV (Niro, Model 3/Y etc).

What benefit does the HP give you? None, because you have plenty range left in the tank where the efficiency of the HP doesnt materially affect you.

You can argue the environmental piece.

Now, if you are regularly driving to the range limit of the car then the HP has a benefit as it can mean that you do not have to stop for a DC charge thus saving you time. How many times that affects you is unique to everyone so they have to decide whether €1k+ is worth that.

In a short range EV like the Leaf it matters alot because you are starting out with a short range so efficiency is alot more important and probably why it is in the Leaf by default (except XE model) since 2013!

liamog · 24-08-2020 10:41am

Deleted User wrote: »

Below 5 Deg C there's no real advantage to the HP any more and around 3 degrees and below it's next to useless. That's what I observed in the Leaf, power consumption went up considerably below 5 Deg C.

That depends entirely on the refrigerant used. Heat pumps do not inherently stop working below 5C. The ID.3 heat pump uses a refrigerant that has a lower operating temperature which reportedly works to below -25C. Heat pumps are used for domestic heating in Scandinavian countries so it's a question of engineering the specific heat pump instead of a generalisation.

KCross · 24-08-2020 10:44am

liamog wrote: »

That depends entirely on the refrigerant used. Heat pumps do not inherently stop working below 5C. The ID.3 heat pump uses a refrigerant that has a lower operating temperature which reportedly works to below -25C. Heat pumps are used for domestic heating in Scandinavian countries so it's a question of engineering the specific heat pump instead of a generalisation.

Its not so much the refrigerant. Its the moisture in the air freezing when it hits the HP and the HP having to work harder to defrost it. The differences in efficiency for air based heat pumps is quite large across different temperature ranges as a result.

HP's for domestic heating in cold countries would usually use geothermal rather than air-2-water hp's, which avoids that problem as the coils are underground.

You are right that they dont just stop working though..... its just that their efficiency becomes terrible, almost the same as a PTC if you go cold enough.

liamog · 24-08-2020 11:06am

One of the touted benefits of the heat pump with the new refrigerant is that it's effective down to -25C. How it holds up to actual testing remains to be seen.

KCross · 24-08-2020 11:10am

liamog wrote: »

One of the touted benefits of the heat pump with the new refrigerant is that it's effective down to -25C. How it holds up to actual testing remains to be seen.

I dont think the refrigerant really matters as thats inside the coils and doesnt freeze anyway. The issue is the moisture in the outside air freezing when it hits the outside of the coils and the heat pump then has to work harder to defrost that... it doesnt matter that the refrigerant inside is still a liquid!

Unless this is some new technology you are talking about. Low freezing point refrigerants arent exactly new. Any data/links on it?

I do see this..
https://www.volkswagen.co.uk/electric/research/software-and-technology/heat-pump#

Is that what you are referring to?

Heat pumps

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