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evnow
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Re: Heater

Sat Apr 24, 2010 8:56 pm

KarenRei wrote: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.
All this is possible in a growing economy - when fossil fuel gets expensive and scarce - these things become prohibitively expensive (both energy & costwise). This is not a problem to be solved - it is a predicament.
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KarenRei
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Re: Heater

Sat Apr 24, 2010 9:44 pm

I think turning this into a "Peak Energy" argument will take this thread down the wrong tangent. Let's just agree to disagree for now on that. ;) Plus, since drinking water is a necessity, even in a contracting economy scenario, it will always be the last thing people sacrifice. Everything else goes first.

mitch672
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Re: Heater

Sat Apr 24, 2010 9:47 pm

Of course you are right Karen.

the next wars will not be fought over oil, but over water.
We can replace oil (not easily or cheaply as we are discovering), water is impossible to replace.
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KarenRei
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Re: Heater

Sat Apr 24, 2010 9:49 pm

sjfotos wrote: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.
Indeed. Of course, your house doesn't have an electric motor and inverter dumping a kilowatt or two of waste heat that you could use as a heat source to reduce the heat differential ;)

Any way, if we're talking a conversion here, or properly designed factory install, you've still got the resistive heater to help out should the temperature difference get too extreme.

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sjfotos
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Re: Heater

Sat Apr 24, 2010 9:59 pm

All true. Apparently an entire team of Nissan engineers were unable to figure that out. ;)
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KarenRei
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Re: Heater

Sat Apr 24, 2010 10:10 pm

sjfotos wrote:All true. Apparently an entire team of Nissan engineers were unable to figure that out. ;)
Huh... I just found someone's masters thesis on basically just what I proposed ;)

http://sherhpa.fiz-karlsruhe.de/script/ ... arreto.pdf

Looks like Audi's e-tron concept involves a heat pump:

http://www.smartplanet.com/business/blo ... ctric/864/

EV1 used a reversible heat pump, and that was a decade ago:

http://www.docstoc.com/docs/11535306/EV1-Electric-Car/

As a northerner, I'd gladly pay good money extra for a heat-pump heating system. To me, such a feature would be worth $3k or so -- an more than an order of magnitude more than it'd cost them to add such a feature. If it utilized waste heat, it could buy you 15 miles or so range when it's cold out.

Seriously, what would they need? A retractable air intake cover, an external temperature sensor (if they don't already have one), some ducting from the pack fan, some ducting from the motor cooling system (not sure what type they use), three or four solenoids, and some extra controls and control circuitry. That's nothing.

Dav
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Re: Heater

Sat Apr 24, 2010 10:59 pm

The RAV4-EV uses a reversing heat pump. People who took some back east do say it only works down to a certain temperature.

They also say that using the "pre-heat" option, so the car is fully heated while plugged into the landline, generally allows the heat pump to keep the interior at an acceptable level to an appreciably lower outside temperature.

But really, it (the heat pump) was a prototype and only marginally acceptable for any use. Not cold enough air and not warm enough heat.

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Re: Heater

Sat Apr 24, 2010 11:08 pm

All engineering decisions involve a trade-off between costs, feasibility, and likely price point acceptance. In the absence of any other evidence I am guessing that the collective judgment of the Nissan Team is superior to speculative musings.
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KarenRei
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Re: Heater

Sat Apr 24, 2010 11:15 pm

Dav wrote:The RAV4-EV uses a reversing heat pump. People who took some back east do say it only works down to a certain temperature.

They also say that using the "pre-heat" option, so the car is fully heated while plugged into the landline, generally allows the heat pump to keep the interior at an acceptable level to an appreciably lower outside temperature.

But really, it (the heat pump) was a prototype and only marginally acceptable for any use. Not cold enough air and not warm enough heat.
The RAV4EV didn't make use of pack or motor waste heat -- which is about the output of a plug-in space heater. And combine a resistive heater with it, and you're good for heat even in Alaska.

It's just such a small amount of extra hardware for such a huge energy consumption benefit in cold weather. I mean, you've already got the heat pump... (AC)...

As for the argument, "Nissan engineers looked at it and decided no" -- well, other EV engineers looked at it and decided the opposite.

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Re: Heater

Mon Apr 26, 2010 3:18 pm

I don't care about the technology used, only that it work. Since I drive very little, and expect to use no more than 10 - 20% of the battery capacity on any given day for powering the vehicle, i.e. the transportation part, I can afford running more current for either heat or A/C, but of course the more efficient they can make it the better. I may choose to park it outside most of the year just so the interior is warmed by the sun, since I rarely leave before 10 or 11 am, although usually the sun takes care of that pretty quickly anyway once I emerge from the garage. That will require a charger than can be accessed from either side of the garage wall, or perhaps I can run the cord under the roll-down door. There is already a 110V socket in an accessible place, so I could trickle charge. I think all of this kind of thing is sort of one big experiment that Nissan will have to follow among the early adopters to see what works, but people are resilient and will adapt.
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