🤔 Impact of a heat pump on R1 efficiency?

[Eric9610]

I'm in Wisconsin, so the need is real

HP technology has diminishing returns as it gets colder outside. In most cases as mentioned by others your will never produce enough heat to meet your needs in very cold climates. The ideal range is like 40-60 degrees outdoor temp. Outside of that range efficacy has no advantage and they will struggle to heat.

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[BigSkies]

Another thing that really helps the Rivian is the panoramic roof. Even a little sun on a cold day gives a massive amount of heat gain.

I’ve had the AC kick on with a sunny day even when the outside temp is in the mid 30’s.

It doesn’t help at night, but it’s a massive difference during the day.

Heck, I could see a heat pump (moving heat from one place to another) functioning as a way to move heat from the cabin to the battery on sunny but cold days.

 

[R1 EVY]

A heat pump in a EV provides a small efficiency value but huge marketing hype value.

What's small in terms of mileage per kWh?

 

[hilld]

A heat pump in a EV provides a small efficiency value but huge marketing hype value.

It might actually just be part of the cost cutting. The vehicle already comes with AC, so to move from AC to HP, all you need is basically a reversing valve as that is what allows an AC until to run "backwards". They could then eliminate a lot of the resistance heat, wiring, etc and save some money, getting closer to their goal of cutting costs out of the vehicle to achieve profitability earlier.

 

[R1Tom]

It might actually just be part of the cost cutting. The vehicle already comes with AC, so to move from AC to HP, all you need is basically a reversing valve as that is what allows an AC until to run "backwards". They could then eliminate a lot of the resistance heat, wiring, etc and save some money, getting closer to their goal of cutting costs out of the vehicle to achieve profitability earlier.

Hp limitations still mean resistive heat and all the wiring will be needed....for those cold days.

 

[hilld]

Hp limitations still mean resistive heat and all the wiring will be needed....for those cold days.

Yes, but much less of it. A lot of heating will come from the motors and battery cooling requirement. Instead of 10kW of resistance heating, maybe they will only do 2kW (I have no idea on the actual numbers), but this will allow them to use much small gauge wiring, relays, heating elements, etc.

 

[rhumbliner]

If you want a really deep dive into how Tesla implements their heat pump system just google this You Tube video from Weber State University:

“Understanding Tesla's Heat Pump System”.

 

[Proxy]

A YouTuber in England gathered a bunch of EV’s, charged them to 100% and then let them sit overnight. The next day with temps just above freezing they ran them all at the same time and route till they wouldn’t move. That was a perfect set of testing conditions that perfectly favor a heat pump. The cars with a heat pump were much closer or higher than rated. If they had preconditioned the battery and interior for the start of the test it probably would have been a lot closer. So, if your use case is those conditions, a heat pump is better. Me? I prefer resistance heating in So Cal and the simplicity and production cost savings it brings.

 

[R1 EVY]

If you want a really deep dive into how Tesla implements their heat pump system just google this You Tube video from Weber State University:

“Understanding Tesla's Heat Pump System”.

Thank you. Here are the highlights. That was amazing.

Summary
Tesla vehicles use a heat pump system for cabin heating, which is more efficient than traditional methods. The heat pump utilizes various sources of heat energy, including the cabin condenser, blower motor, and vehicle radiator.

Highlights

• 0:35 Three types of cabin heating systems: old-school heater core, PTC air heater, and heat pump
• 2:47 PTC air heater and PTC coolant heater consume more power compared to the heat pump system
• 5:10 Heat pump system can transfer heat energy from up to 16 different sources in the vehicle
• 7:25 Cabin condenser, blower motor, and vehicle radiator are sources of heat energy in the heat pump system

Key Insights

1. The type of cabin heating system in an electric vehicle can significantly impact driving range in cold temperatures.
2. The heat pump system in Tesla vehicles is more efficient and consumes less energy compared to traditional heating methods.
3. Tesla’s heat pump system utilizes multiple sources of heat energy within the vehicle to provide effective cabin heating.
4. The cabin condenser, blower motor, and vehicle radiator are key components involved in the heat transfer process.
5. Tesla’s heat pump system can achieve a coefficient of performance (COP) as high as 5.6, indicating efficient heat transfer.
6. The heat pump system allows Tesla vehicles to maximize range by reducing energy consumption for cabin heating.
7. Other electric vehicle manufacturers, such as General Motors and Nissan, also use heat pump systems for cabin heating.

 

[jjswan33]

HP technology has diminishing returns as it gets colder outside. In most cases as mentioned by others your will never produce enough heat to meet your needs in very cold climates. The ideal range is like 40-60 degrees outdoor temp. Outside of that range efficacy has no advantage and they will struggle to heat.

I know that is conventional wisdom but I saw a video from OOS Kyle a while back where he tested a Tesla with a Heat Pump vs resistive heater in very cold weather and the heat pump appeared to perform much better.

 

[R1 EVY]

A YouTuber in England gathered a bunch of EV’s, charged them to 100% and then let them sit overnight. The next day with temps just above freezing they ran them all at the same time and route till they wouldn’t move. That was a perfect set of testing conditions that perfectly favor a heat pump. The cars with a heat pump were much closer or higher than rated. If they had preconditioned the battery and interior for the start of the test it probably would have been a lot closer. So, if your use case is those conditions, a heat pump is better. Me? I prefer resistance heating in So Cal and the simplicity and production cost savings it brings.

So if I preheat in a garage, then the heat pump will only provide a minimal improvement?

 

[Eric9610]

I know that is conventional wisdom but I saw a video from OOS Kyle a while back where he tested a Tesla with a Heat Pump vs resistive heater in very cold weather and the heat pump appeared to perform much better.

This is more about refrigerant flow and pack cooling / heating more than HP alone.

Since Rivian has done a really good job with pack temp management. A HP will have limited impact. The more heat you can pool from motors and pack the better heating you have.

 

[Proxy]

So if I preheat in a garage, then the heat pump will only provide a minimal improvement?

In my opinion for daily driving, yes. For a 1,000 mile road trip, it will make about the same impact as driving 1 mph slower.

 

[HaveBlue]

The Rivian scavenges heat from the invertors and supplements it with a PTC element. A heat pump, though more efficient, is not going to be as big a difference as switching to a heat pump in a home heating or water heater situation. The reason is that a home isn't producing waste heat that can be captured to supplement a heating element. When you switch from a resistive electric water heater that is even worse than a PTC to a heat pump, the cost to operate can drop to one third. The Rivian falls in between those scenarios with some recovered waste heat. If the drive motor is at 100F and you want 70F in the cabin, there's spare heat to be had and can also utilize a more efficient PTC over conventional resistive elements.

 

[Zoidz]

I know that is conventional wisdom but I saw a video from OOS Kyle a while back where he tested a Tesla with a Heat Pump vs resistive heater in very cold weather and the heat pump appeared to perform much better.

I posted about this a few weeks ago in another thread.

Kyle’s video is accurate in terms of which vehicle warms up faster, but Kyle’s conclusions are flawed. The heat pump equipped Tesla has 30 modes of operation and 16 heat sources. At that low of temperature, Tesla is using resistive heat sources in addition to the heat pump. They are also heating up the motors and other components to warm up quicker. Heat pumps are inefficient at low temperature and the laws of thermodynamics don’t change, even if Elon makes it look that way. Yes, the heat pump saved some battery, but it is not responsible for the quicker heating. Kyle’s video plays to the hype without understanding what’s really happening.

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