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Re: (long) Re: PROPOSED GOVERNMENT DRIVING RESTRICTIONS
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Subject: Re: (long) Re: PROPOSED GOVERNMENT DRIVING RESTRICTIONS
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From: enyman@vt.edu (Rick Nyman)
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Date: Tue, 25 Jul 1995 23:25:10 GMT
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Newsgroups: dc.driving
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Organization: Virginia Tech Graduate (Mechanical Engineering)
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References: <3usfgn$oh1@eddie.intr.net> <3uv6i7$244@cville-srv.wam.umd.edu> <EHAHN.95Jul24125646@bass.mitre.org>
ehahn@bass.mitre.org (Ed Hahn) wrote:
>In article <3uv6i7$244@cville-srv.wam.umd.edu> sorandi@wam.umd.edu (Persepolis) writes:
>Now, don't get me wrong; I would love to see solar or wind power
>working, but the studies I've seen show that at most these particular
>technologies could only supply a small fraction (something like 10%)
>of today's total energy demand of the US, given weather patterns and
Actually, there are power plants using many alternative methods
already online. But their capacity is already used up. Utilities
don't install large amounts of extra capacity unless they need it and
can pay for it.
>Even assuming that the electricity can be generated efficiently,
>looking at the thermodynamic efficiencies of transporting, storing
>in batteries, and then converting to motion the electrical energy, I'm
>not sure how much better off you'd be than if you burned fossil fuels
>at the end point (i.e. in the vehicle) in the first place.
It depends. Right now, they're claiming low 30's for car efficiency
and about the same for the installed generation facilities (although
some combined cycle gas turbine/steam turbine plants are getting up to
60% efficiency - a fantastic number). I don't know what the losses in
the grid do though.
>In summary, I do believe that we should study energy alternatives and
>electric vehicles, but I don't think that we can handwave the
>arguments for or against either one.
Just one thing to remember in the electric car wars. I've heard that
the average house uses 1-2kW of electricity at any given time. (Of
course it peaks higher during the day and is lower at night). Perhaps
this is a bit low and it's closer to 2.5kW, including HVAC and
lighting better than most have. This is the same as a continuous 40
amp load at 120 VAC (That's 40+ 60 watt light bulbs) - I hope this
seems as high as it is, remember this is averaged over a 24 hour
period).
Now look at an electric car. The current HVAC systems in electric
cars are rated around 6kW (yes, car air conditioners are rated around
3 tons, same as many house air conditioners - but car ones often run
continuously) The drive motors in small cars are rated around 60kW
with the cruising power to be around 15kW.
Depending on how much driving you do, if you assume 2 hours/day at
21kW (We're assuming HVAC on all the time, but also 100% battery
efficiency and you're not driving like a maniac - I live in the DC
area and that's not the case here - the reduces economy a lot), than
you're using (21/12 because you're using the car 1/12th of the time
over a 24 hour period) 21/12=1.75kW on the average. This is within
the range that I suggested above and over 2/3 the power used in my
hypothetical house.
The range for the house above, at $.06 per kWh would be $43.20 to
$86.40 per month for electric costs. The hypothetical house would
have a $108 bill.
So the electric car would cost $75.60 per month in electricity. Now I
live in the DC area where electricity costs more like 9 cents per kWh
- it would cost me $113.4 per month for the power. I don't know about
you, but I pay far less than that in gas. I don't forsee electric
cars helping these costs much either because utilities would be forced
to build more power plants to handle the load - someone's gotta pay
for them.
--
Rick Nyman <enyman@vt.edu>
A recent graduate of Virginia Tech's Mechanical Engineering department.
(Still looking for a job)
Home Page: http://sfbox.vt.edu:10021/E/enyman/index.html
My ASMEnet account: nymane@asme.org
References: