KarenRei
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Heater

Sat Apr 24, 2010 12:20 pm

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.

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Randy
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Re: Heater

Sat Apr 24, 2010 1:04 pm

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...

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sjfotos
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Re: Heater

Sat Apr 24, 2010 1:26 pm

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!
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KarenRei
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Re: Heater

Sat Apr 24, 2010 2:17 pm

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.

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evnow
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Re: Heater

Sat Apr 24, 2010 2:35 pm

KarenRei wrote: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).
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sjfotos
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Re: Heater

Sat Apr 24, 2010 2:57 pm

Thank you Karen, you make a good point of course. I was thinking more along the lines of the heating solution.
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garygid
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Re: Heater

Sat Apr 24, 2010 3:12 pm

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.
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Re: Heater

Sat Apr 24, 2010 3:46 pm

garygid wrote: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.
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evnow
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Re: Heater

Sat Apr 24, 2010 5:10 pm

garygid wrote: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.
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LTLFTcomposite
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Re: Heater

Sat Apr 24, 2010 5:19 pm

evnow wrote:
garygid wrote: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.
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