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KarenRei said:
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.
 
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.
 
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.
 
sjfotos said:
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.
 
sjfotos said:
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/tool/forg/doc458/Final_Report_Heating_and_Cooling_an_EV_Ricardo_Arboix_Barreto.pdf

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

http://www.smartplanet.com/business/blog/smart-takes/audis-e-tron-concept-car-four-motors-all-electric/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.
 
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.
 
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.
 
Dav said:
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.
 
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.
 
Karen,
I do appreciate the citations and the perspective. I am simply making the observation that I think it very unlikely that a team of engineers at a major global company did not consider the relative merits of the system you describe. They have many factors to balance and though I have a great amount of respect for advanced engineering topics, the automotive industry does have some reason to adopt a more conservative solution when the call gets close. The number of things that can go wrong are endless even in the well understood systems.
 
A heat recovery system like that would have almost certainly added to the cost, weight, or schedule. They figure the bulk of their sales will be in temperate coastal regions.

Here in south Florida home A/C systems are almost exclusively resistance heat. The systems are cheaper initially and are slightly more efficient at cooling than reverse cycle systems. Heat is almost never used here. A couple hundred miles north heat is needed more and reverse cycle is popular.

Weighing just the factors I can speculate over it's easy to see how Nissan arrived at the decision they did.

BTW what is the heat system on the Aptera?
 
LTLFTcomposite said:
A heat recovery system like that would have almost certainly added to the cost, weight, or schedule. They figure the bulk of their sales will be in temperate coastal regions.

They have a partnership for launch in DC and TN. Those may not be Minnesota winters, but they're not exactly mild, either.

The systems are cheaper initially and are slightly more efficient at cooling than reverse cycle systems.

If you already have a heat pump (the AC), the difference is a tiny bit of ducting and a couple solenoids. There's practically no COP difference for cooling, but a tremendous one for heating.
 
Dav said:
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.
I guess we can consider the whole car to be a prototype. But I disagree that the HVAC system is only "marginally acceptable for any use." Not by a long shot. A few of us had issues with the HVAC EARLY ON - but when the thing works correctly (as mine does now) it can get both far too hot and far too cold for my comfort. I do live in a mild climate... but then so do millions of people. For them, this system is far from "marginally acceptable!" It actually works amazingly well for how efficient it is.
 
I live in Chandler AZ and it is nice still building more house so I am not sure the population is moving away? I have a Nissan Leaf reserved I pick the SL in black but wanted a mix gray/ brown kinda like coffee in color. The black will look sharp and be hard to keep clean. I ask around some people about black being hotter then a lighter color but most said there was no difference hot is hot in AZ. I am hoping to get to work and back which is about 75 mile.
 
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