Why don't R1s have a heat pump?

[tcole]

I've been wondering this for a while and thought I'd ask if anyone has speculation about why Rivian might have decided not to use a heat pump in the R1s?

The 2022 Volvo C40 that I just sold had a heat pump and worked great through this last winter in Tahoe, the closest and most snowfall winter in something like 70 years.

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[chrismc]

Smaller more efficient EVs with much smaller batteries have a much greater benefit from heat pump efficiency- as the vehicle gets more efficient (like a truck) with a much larger battery you get diminishing returns on switching to a heat pump along with greater cost and complexity. Additionally, heat pumps don’t work as effectively at the hot and cold temperature extremes and the R1 as an “adventure vehicle” needs to be able to handle those.

 

[Redmond Chad]

Yeah, what chrismc said. I love heat pumps, especially since they work really well where I live. But I can see why a new OEM might prefer to go with a resistive heater, at least at first:

• It's cheaper
• It's less complex
• It warms up faster (luxury makes with a heat pump might ALSO have a resistive heater just for this reason)
• It works well even in extreme cold (where if you have a heat pump, you might need to ALSO have a resistive heater)

A heat pump definitely can save energy in mild weather. But the less mild the weather gets, the less you save...until some point you aren't saving anything, and/or you aren't getting enough heat in the cabin. In other words, a heat pump is great at saving energy when you least need to save energy. (Not that it's ever a bad time to save energy! It's just that when you need it the most, it's the least help).

Also as chrismc noted, the less efficient your vehicle is, the less you'll gain percentage-wise. Rivians aren't the least-efficient EVs on the market, but they're sure on that end of the scale.

I'd still love to see Rivian add heat pumps, but I can see why it wasn't a top priority to have them right off the bat.

 

[Dark-Fx]

Rivian has PTC heaters instead of heated coolant, which are a little more efficient and faster, and means one fewer coolant system to deal with like some other manufacturers have implemented.

 

[tcole]

Smaller more efficient EVs with much smaller batteries have a much greater benefit from heat pump efficiency- as the vehicle gets more efficient (like a truck) with a much larger battery you get diminishing returns on switching to a heat pump along with greater cost and complexity. Additionally, heat pumps don’t work as effectively at the hot and cold temperature extremes and the R1 as an “adventure vehicle” needs to be able to handle those.

Ok, I think I get what you're saying. To rephrase it a bit with some examples, the Volvo C40 has as 78kW/h battery. Using a heat pump there may save a large enough overall percentage of the vehicles power draw to make it worth the extra cost and complexity. Versus in an R1 with almost a 2x larger battery and substantially larger overall power draw, the heat pump gains are going to be less consequential, combined with the other tradeoffs below. I think I get it.

Regarding temperature extremes, I don't know anything about automotive heat pumps, so maybe this isn't comparable. But on the cold side, there are household heat pumps on the market (I have two on my house) that are still more efficient than resistive heat down to at least -13F. I think they are still at COP 2 at -13F, but below that start reducing their total BTU output. But those same units on the cooling side max out at 115F, which is not going to be good enough for anyone living in Phoenix or some place like that.

I don't know if that tradeoff between low temp performance for heating and high temp performance for cooling is inherent. But if it is, you'd potentially want to ensure cooling performance is good at a higher temp and also need a resistive heater to handle the low end, adding more cost and complexity.

 

[chrismc]

Regarding temperature extremes, I don't know anything about automotive heat pumps, so maybe this isn't comparable. But on the cold side, there are household heat pumps on the market (I have two on my house) that are still more efficient than resistive heat down to at least -13F. I think they are still at COP 2 at -13F, but below that start reducing their total BTU output. But those same units on the cooling side max out at 115F, which is not going to be good enough for anyone living in Phoenix or some place like that.

This is where things get interesting, as heat pump technology is rapidly evolving today after being pretty stagnant for a decade or two. On the structural HVAC side, there are a number of innovative heat pump designs just starting to come to market that use some refrigerant options that have not been used before such as CO2 and propane. They promise much greater efficiency and a much wider temperature range of operation. Automotive heat pumps are more traditional in refrigerant selection and design, but I expect these improvements will trickle down to autos in the next few years and make HPs a much more viable option for EVs in all climates.

 

[Zoidz]

Last year Rivian commented that they are working on/transitioning to heat pump for the "next generation platform". It's unclear if that specifically means next generation R1 or the R2, or both. They mention "in-house drive units" which is the now shipping R1 Enduro drive, so it's possible the R1 will get a heat exchanger in the future.

The company also said that it will “continue significant investments” in its next-generation platform, which includes new in-house drive units, charging systems, and a heat pump. The heat-pump-based thermal system under development will offer improved cold-weather efficiency, according to the company.

 

[electruck]

The discussion also isn't a simple as just resistive/ptc vs heat pump. It's possible some details changed before reaching production but this particular info still seems pretty spot on.

https://electricrevs.com/2018/11/29/rivian-the-powertrain-details-you-wont-read-about-elsewhere/

Coolant loops

There is a single overall vehicle water-based liquid coolant system with at least two sub-loops and a grill-mounted radiator and fan, according to Richard Farquhar of Rivian.

A first sub-loop runs through and cools components like the motors and motor inverters. A second sub-loop runs through the battery pack.

Computer-controlled valves and replicated water pumps allow these loops to either operate separately or be joined together in order to exchange heat between the components and possibly the radiator.

For instance, although the battery pack has its own dedicated electric heater it can sometimes be effective and more efficient to share heat from the motors and motor inverters with the battery pack in cooler weather.

The battery pack loop also has a “chiller” connection to the air conditioning system to help cool the pack when it gets too hot. There is also apparently a heat exchange path that allows battery pack heat to help warm the vehicle cabin in addition to or instead of electric resistive heating.

 

[R1Tom]

This is where things get interesting, as heat pump technology is rapidly evolving today after being pretty stagnant for a decade or two. On the structural HVAC side, there are a number of innovative heat pump designs just starting to come to market that use some refrigerant options that have not been used before such as CO2 and propane. They promise much greater efficiency and a much wider temperature range of operation. Automotive heat pumps are more traditional in refrigerant selection and design, but I expect these improvements will trickle down to autos in the next few years and make HPs a much more viable option for EVs in all climates.

You think things like scroll compressors with vapor injection?

 

[MacO512]

The heat pump needs to be designed very well like the Tesla Model 3/Y are to have a benefit. Those have their elaborate octovalve and really do help.

But just putting a basic heat pump without extensive engineering as VW/Audi have done doesn't provide a benefit.

 

[BigSkies]

I'd guess it's something they wanted to include but ran out of time before design freeze.

While theoretically not super complicated, I imagine there are well established suppliers for the components needed for the AC/heating systems they used versus needing to design something in-house for a heat-pump. It would have been one more hurdle in getting to market when time & money were constrained for launch.

While we're still early in the EV game, you can see different manufacturers focus their R&D in different areas. Each company is focusing on different elements today, and I imagine they'll have pretty similar features in a decade. It will just take time. Hyandai/Kia is focused on 800v systems, Ford put a lot of effort into the ProPower and home backup, and Tesla has been putting their R&D money into better fart buttons.

 

[NineElectrics]

I think it's a cost issue. Look at how cheap the cameras are; they were hoping nobody would notice the lack of a heat pump. It's a shame because the big glass roof leaks a ton of heat, and makes the whole "winter adventuring" thing a lot more difficult. My car gets 180 miles on road trips.

 

[NineElectrics]

I think it's a cost issue. Look at how cheap the cameras are; they were hoping nobody would notice the lack of a heat pump. It's a shame because the big glass roof leaks a ton of heat, and makes the whole "winter adventuring" thing a lot more difficult. My car gets 180 miles on road trips.

Interestingly, the very cheap Volvo EX30 will have a heat pump standard on all trims.

 

[Killer95Stang]

Interestingly, the very cheap Volvo EX30 will have a heat pump standard on all trims.

Just curious, since the R2 will most likely come with a heat pump at a lower price point. Are heat pumps ideal for every scenerio? I mean, I'm in Socal, so 3/4 of the year I'd be okay with corner vent windows like in my 63 Sprint. But would a heat pump "always" be more desirable. I'm just wondering if once the heat pump arrives, will people be complaining about them, because it is not ideal for their climate?

Edit... Just read this article... so... "it depends"

https://www.wired.com/story/heat-pu...mps come in,new electrified flagship, the EV9.

 

[NineElectrics]

Just curious, since the R2 will most likely come with a heat pump at a lower price point. Are heat pumps ideal for every scenerio? I mean, I'm in Socal, so 3/4 of the year I'd be okay with corner vent windows like in my 63 Sprint. But would a heat pump "always" be more desirable. I'm just wondering if once the heat pump arrives, will people be complaining about them, because it is not ideal for their climate?

Edit... Just read this article... so... "it depends"

https://www.wired.com/story/heat-pump-helping-but-not-solving-ev-cold-weather-problem/#:~:text=Today, heat pumps come in,new electrified flagship, the EV9.

That article contains this pretty strong quote: “Any electric vehicle that comes out right now and doesn’t have a heat pump is a dinosaur already,” says John Kelly, an automotive technology professor and instructor focusing on hybrid and electric vehicle technology at Weber State University." Wow.

A Rivian is definitely a "California car" right now, but if a heat pump should come standard, I don't see why anyone would complain. A Rivian already comes with air conditioning, which is actually a heat pump, just one which can only run in one direction. Presumably once they figure out how to make it run in both directions they'll could use the heat pump for both heating and air conditioning. So to me, the added complexity could be minimized. Maybe it will even get us faster charging, since it could theoretically be used to help cool the battery when DC fast charging. Unlike Audi, Rivian isn't great at a SoC past 80%.

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