Heater

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KarenRei

Well-known member
Joined
Apr 23, 2010
Messages
130
I'm curious if Nissan can yet say how the heater works:

* Is it a resistive heater or a heat pump?
* If a heat pump, is it a reversible heat pump (i.e., the same unit powering the AC)?
* If a heat pump, does it use motor and/or pack waste heat as the source heat well to reduce the energy required for the heat pump, or just outside air?

Obviously, the most energy-efficient case would be to use a heat pump that makes use of motor and/or pack waste heat to reduce the amount of energy needed. EVs don't put out nearly as much waste heat as gasoline cars, but they still put out some! A 90% efficient motor running at 15kW is putting out 1.5kW of waste heat, or about the heat of your average plug-in space heater. And obviously, the worst case would be a resistive heater, since that means you get a COP of just under 1.0 instead of 2-3, meaning 2 to 3 times as much energy needed to keep the car warm.
 
Mark Perry said that it will be a resistive heater. But to help drivers use it less and reduce heating current, they're providing heated seats and a heated steering wheel...
 
Although a power drain, I prefer the resistive heater. I hate added complexity and this car has the beauty of being a simple design (not low tech, just simple). A heat pump is just one more set of mechanical components to go bad. Plus, in my locale (Pennsylvania) heat pumps (other than geo-thermal) do not report for duty after it starts to get to the real winter!
 
An air conditioning system *is* a heat pump. So there's already a heat pump onboard. It's just not reversible, apparently. A shame.

Resistive heaters use 2-3x as much power for the same amount of heating. More, if the competing heat pump uses the motor as a heat source.
 
KarenRei said:
An air conditioning system *is* a heat pump. So there's already a heat pump onboard. It's just not reversible, apparently. A shame.

Resistive heaters use 2-3x as much power for the same amount of heating. More, if the competing heat pump uses the motor as a heat source.

What kind of price difference would be there - between a reversible heat pump and a normal AC ?

We should always remember, Nissan built this for a price point - unlike Volt which will price it based on cost (where now they have a problem because of Leaf).
 
If one only travels for 2 hours, and the heater draws 2kW, then that is 4 kWh out of 24, about a 16% usage (drop in range).

In AZ (and southern CA), we do not use the heater very much.

But, ... in "northern" places ... it can be a LOT colder.

In AZ, with 115 degree ambient air and a full sun radiation load, one wonders if the AC will be sufficient. The AZ driving data next summer should tell us a lot.
 
garygid said:
If one only travels for 2 hours, and the heater draws 2kW, then that is 4 kWh out of 24, about a 16% usage (drop in range).

In AZ (and southern CA), we do not use the heater very much.

But, ... in "northern" places ... it can be a LOT colder.

In AZ, with 115 degree ambient air and a full sun radiation load, one wonders if the AC will be sufficient. The AZ driving data next summer should tell us a lot.

I used to use A/C here before I went to Sri Lanka, where 115 here is nothing compared to the high heat and humidity (99-100% ALL the time) there. So I stopped using my A/C UNLESS I have a passenger, which means I don't plan on using the A/C much at all. Same for the heater...very rarely do I need it here.
 
garygid said:
In AZ, with 115 degree ambient air and a full sun radiation load, one wonders if the AC will be sufficient. The AZ driving data next summer should tell us a lot.

I have to wonder what will happen to AZ in 10 to 15 years. I expect major depopulation as it becomes hotter, drier and fossil fuels get costlier and scarce.
 
evnow said:
garygid said:
In AZ, with 115 degree ambient air and a full sun radiation load, one wonders if the AC will be sufficient. The AZ driving data next summer should tell us a lot.

I have to wonder what will happen to AZ in 10 to 15 years. I expect major depopulation as it becomes hotter, drier and fossil fuels get costlier and scarce.

Yeah, but it's a dry heat :)

From what I saw on the evening news, nobody there is yet concerned about declining population.
 
Add that to the feature content list for Leaf 2.0 - reverse cycle A/C for heat

One problem you have with heat pumps/reverse cycle AC for heating is they lose effectiveness at lower temps.
 
LTLFTcomposite said:
Add that to the feature content list for Leaf 2.0 - reverse cycle A/C for heat

One problem you have with heat pumps/reverse cycle AC for heating is they lose effectiveness at lower temps.

Indeed. But they're still a lot more efficient than resistive.

To simplify it, an air conditioner is a device that moves heat from one radiator to another, wherein the one having heat removed from it has a fan over it that leads into the vehicle, while the one having heat pushed into it has a fan over it that blows to outside air. A reversible heat pump can change which radiator is which. Another alternative is to keep the radiators the same, but simply switch where the ducts are leading.

It's just a matter of ducts and solenoids.
 
I'm guessing the problem for an 'all heat pump' solution is the problem faced by my original heat pump installation here in Pennsylvania for my house. Once it gets down into the 30's (F) it just can't keep up. In any event, it will be interesting to see how it all works in a real application in the North.
 
daniel said:
LTLFTcomposite said:
From what I saw on the evening news, nobody there is yet concerned about declining population.
Just wait until they start having water outages!

Eh, what'll happen is that agriculture fed by the Colorado River will start getting pushed out of business. Farmers can't afford to pay nearly as much for water as people can pay for water for their homes. If it gets bad enough, you'll see desalination plants in California and an adjustment of the Colorado River Compact, with the upper states helping pay the cost in exchange for more of the river's water. Desalination water is generally too expensive for agriculture, but again, what's too expensive for agriculture isn't necessarily too expensive for homes.

Also, there's some interesting new desalination techs out there. My favorite -- although it'll require some massive-scale high-throughput ion-selective membranes or salt bridges to work -- is this really clever one involving evaporation ponds. So, basically, black-bottomed open-air evaporation ponds aren't very expensive. They're a *lot* cheaper than covered ones that try to collect condensation from the evaporation. So you can get very salty brine, many times saltier than seawater, really cheap. Now, that's the opposite of what you want, right? You want freshwater. So what they do is they link it up to two different ponds of normal concentration seawater with ion-selective channels -- one pond gets positive ions, like sodium, and the other pond negative ions, like chlorine. Now, obviously, the ions *really* want to travel out of this super-concentrated brine into these other ponds so they can all be equal saltiness... but they can't. If they did, they'd be mismatched! So, they bring into play a third pond of regular seawater. It also provides an ion channel to each of the other two seawater ponds, of the opposite type -- that is, the pond that has a positive ion channel to the brine gets a negative one, and the one that had a negative ion channel to the brine gets a positive one. So the brine gets to push ions down from its extreme concentration, so long as an opposite ion gets sucked out of the third seawater pond. Since the ions *really* want to leave the super-concentrated brine, that's no problem. And so what you end up with is all of the salt being sucked out of the third seawater pond in the process. Freshwater, with no electricity input! Again, though, the issue is making said membranes high enough throughput and low enough cost.
 
One dual-port valve to re-direct the refrigerant's flow right after it leaves the one-way compressor?

Either to the inside radiator (cabin heating) or to the outside radiator (cabin cooling).
No air-duct switching needed.
 
KarenRei said:
LTLFTcomposite said:
Add that to the feature content list for Leaf 2.0 - reverse cycle A/C for heat

One problem you have with heat pumps/reverse cycle AC for heating is they lose effectiveness at lower temps.

Indeed. But they're still a lot more efficient than resistive.

To simplify it, an air conditioner is a device that moves heat from one radiator to another, wherein the one having heat removed from it has a fan over it that leads into the vehicle, while the one having heat pushed into it has a fan over it that blows to outside air. A reversible heat pump can change which radiator is which. Another alternative is to keep the radiators the same, but simply switch where the ducts are leading.

It's just a matter of ducts and solenoids.

I've never seen a reverse cycle system that worked that way. Converting an automotive ac system to a heater with ducting doesn't sound to practical. The condenser is out in front where it gets airflow (probably why you still see a fairly sizable grill). The usual approach of reversing the gas/liquid flow would be a lot easier IMO.

As for reverse cycle systems being more efficient than resistive, that's true up to a point. In really cold temps they don't work at all.
 
garygid said:
One dual-port valve to re-direct the refrigerant's flow right after it leaves the one-way compressor?

Either to the inside radiator (cabin heating) or to the outside radiator (cabin cooling).
No air-duct switching needed.

If the compressor is powered by a DC motor maybe you can switch between heat and AC by just switching the polarity! :)
 
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