AC / Heat / HVAC

[Blueassassin]

Do we know if the heat will be a heat pump set up or a heating element? Haven't seen anything on this not sure which is better either but here in Chicago its cold and I plan on the heat, heated seats and steering wheel working a lot. Which I know will impact range a lot as well.

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[CommodoreAmiga]

Most info we've seen points to NOT having a heat pump in the initial release.

Rivian did have a job posting for a heat pump engineer, so maybe a future revision will move to a heat pump.

 

[Blueassassin]

The model 3 used 3 times more power with the older heating element style heater that it had.

 

[cwoodcox]

Yep. Heat pumps can get crazier, moving 2x the energy input through the system is child’s play, residential systems can get back something like 3.5x the energy you put in if the conditions are correct.

Heat pumps should be used far more than they currently are. They’re amazing.

 

[discsinthesky]

I've been wondering how the electrical usage compares between heated or cooled seats/steering wheel vs heat pump for a comparable amount of comfort?

I think I understand the efficiency gain of a heat pump for heating the cabin air more efficiently compared to resistive heating for the air, but I wonder if the lowest energy use option is still seat heating and minimal cabin heating, heat pump or not.

Anyone have some insights on this? Is it the same conclusion for heating vs cooling?

 

[Drterreur]

I think I read somewhere that heat coming from the battery and motors was enough to heat the cabin. Also, the heat pump was not able to work in the full range of conditions the rivian was design to withstand (extreme cold)

 

[CommodoreAmiga]

I've been wondering how the electrical usage compares between heated or cooled seats/steering wheel vs heat pump for a comparable amount of comfort?

I think I understand the efficiency gain of a heat pump for heating the cabin air more efficiently compared to resistive heating for the air, but I wonder if the lowest energy use option is still seat heating and minimal cabin heating, heat pump or not.

Anyone have some insights on this? Is it the same conclusion for heating vs cooling?

Most manufacturers only use ventilated seats — not actively cooled. So in those vehicles you don’t get hardly any comfort from the ventilation, on its own. You must cool the cabin and then the seat ventilation circulates conditioned air through the seat.

however, heated seats and steering wheel do help in the winter. I know several EV owners who have learned to heat the cabin to a lessser temp and rely more on the seat heaters to make it liveable. Also, keep your layers on instead of removing your jacket(a).

 

[txtravwill]

Most manufacturers only use ventilated seats — not actively cooled. So in those vehicles you don’t get hardly any comfort from the ventilation, on its own. You must cool the cabin and then the seat ventilation circulates conditioned air through the seat.

however, heated seats and steering wheel do help in the winter. I know several EV owners who have learned to heat the cabin to a lessser temp and rely more on the seat heaters to make it liveable. Also, keep your layers on instead of removing your jacket(a).

The key is to heat up the cabin while plugged in before leaving, then you won't burn that energy from the battery (it does take a LOT of amps though when heating a very cold cabin, often just as much as charging at max almost).

 

[electruck]

I don't know that this has been confirmed 100% but I believe it has been stated they are not using a heat pump. They are however doing some smart things by sharing heat between the 3 different coolant loops (cabin, motor/inverter, battery) so it's not quite as simple a discussion as whether there is a heat pump or not.

Here's an excerpt from an article dated 11/29/2018 (and apparently updated some time later):

Coolant loops
Update: the description of the coolant loops has been updated.

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.

A Rivian patent describes a similar system although it’s unclear how precisely this relates to the actual implementation used in Rivian’s initially announced vehicles.

 

[cwoodcox]

cooling the cabin uses a heat pump (yep) so it’s not going to be a huge energy suck.

targeted heat (seat heaters and heated wheel) get more bang for your watt, your own body heat and the heat of the battery will eventually warm the cabin, the other two just help your extremities not feel so cold until that happens.

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