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From: John De Armond
Subject: Re: How do I heat my EV in winter?
Message-ID: <>
Date: Mon, 04 Oct 93 05:49:07 GMT

mwilson@ncratl.AtlantaGA.NCR.COM (Mark O. Wilson) writes:

>In <> writes:

>|For heating an electric car in winter I would think you should be willing to
>|accept minor power losses and just use the damn batteries to run a resistance
>|heater.  I mean, if you are using 20hp of engine capacity, that is a 15
>|kilowatt draw.  Running a 1 kilowatt space heater at the same time is only
>|going to drop your range by 6-7%.  If you are really worried, keep the

>Nor will it keep your car very warm. Up your heater to 5K - 10K watts.

I've seen so many wild numbers tossed about that I feel the need for a
reality check.

First off a 1-1.5 kw heater WILL keep a car comfortable in weather
typical of the east.  I know cuz I drove around a good part of one winter in
Middletown, PA with a small gas generator strapped down to the bed of my
El Camino and a 1.4 kw heater sitting in the passenger floorboard.  This
beause I was too lazy to change the %&^*^&* heater control valve.
This heater kept me more than warm and adequately melted snow and
ice off the windows.

10 or 20 or even 30 kw heaters are not required because:

*	We generally don't heat the whole cabin.  Heated air is directed on
	the feet and thence up across the front of the body.

*	The padding in the seat provides enough insulation that little heat is
	needed to keep that part warm.

*	Dead air space and/or sound deadening materials in the body serves
	as decent insulation.

Beyond that, it would perhaps be useful to look beyond the current
crude but wasteful heating paradigm that works when gross amounts of waste
heat is available.  What would an engineered approach to heating with
limited energy resources involve?  Pretty much the same as is used in
energy efficient houses and maybe some innovation. Consider:

*	Limit air infiltration - easy to do with no engine out front.
*	Lightweight, high efficiency thermal insulation.  NASA has spent
	a BUNCH of our money figuring out how to do this.
*	Double-pane glass, perhaps even with a vacuum in the trapped volume.
*	Preheat the car while connected to the mains and perhaps store
	some added heat in phase change thermal batteries such as those
	designed by Volvo and written up on the SAE journal last year.

Now, what can we do to further reduce the energy requirements?  Direct
application of heat where it is needed is one way.  Thin film window
heaters - already in production - is one, heating seats is another.
A bit more sophisticated would be infrared heating panels.  Anyone
who has worked under a Glow-Ray heater 20 feet up in a warehouse
understands how effective this can be.  The IR emitted by a low
energy density panel penetrates even moderate clothing to warm the body.
This can be further refined by concentrating heat on the feet, hands
and heat - the parts of the body most critical to the sensation of being

Using these techniques, I'd expect to be able to heat a 4 passenger
vehicle with well under 1 kw.


From: John De Armond
Subject: Re: How do I heat my EV in winter?
Message-ID: <>
Date: Wed, 06 Oct 93 08:55:39 GMT (Russ Brown) writes:

>In article <> (John De Armond) writes:

>>Using these techniques, I'd expect to be able to heat a 4 passenger
>>vehicle with well under 1 kw.

>How would all this work at 10 below zero at speeds of 55 mph, especially
>with windows to defrost (and a little snow on the road, too)?  Of
>course, even if it wouldn't last for a 90-mile trip, it would be better
>than riding a bicycle in these conditions.

The more advanced techniques such as sophisticated insulation,
vacuum pane windows and so on will reduce the effects of outside
conditions.  To paraphrase an old saying, a little bit more of
practically nothing is still practically nothing.

>During some of the year, the _real_ world is not like Cobb County,
>Berkeley, or Marin County.  :-)

Believe it or not, I've lived all over the country including (UGH) the
northeast.  My escapades with the electric heater and generator were in
Harrisburg, PA.  Down here I'd not bother.  Indeed, the El Camino
STILL needs a new heater valve.  (It always did seem to me to be some
sort of cosmic irony to pull onto the Three Mile Island site with
my little generator churning away in the back :-)

To an extent this is all mental masturbation since I don't believe a
pure EV will ever be widely deployed as a general purpose transportation
solution.  Sure it will fill some specific needs such as SoCal
transportation and maybe even short trips for people elsewhere.  But I
don't ever think we'll see the day where people are trying to drive
their 4WD EVs in Fargo, ND.  The pure EV will be a fair weather-only
vehicle.  And once we move toward more practical hybrid vehicle designs,
the heat source becomes somewhat moot since the vehicle can carry enough
chemical energy to do both jobs.  Even hydrogen-fueled fuel cells
generate more than enough heat for comfort heating.  I suspect cars will
be fueled with some form of liquid hydrocarbon at least for my lifetime
and probably my kids (if I had any.)

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