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Grex Science Item 80: Musings on electric vehicles, the price of oil and global warming
Entered by russ on Sat Oct 5 02:44:51 UTC 2002:

I was going over some of the figures regarding the Tango commuter
car (somewhere below www.commutercars.com) and found a pointer to
the site of the company which makes Yellow Top batteries.  (These
are a brand of deep-discharge cells popular with electric-car folks.)

One of the graphs on the battery site is very interesting.  It has
two curves, one of lifespan (in cycles) vs. discharge depth and total
energy transferred vs. discharge depth (presumably over the number of
cycles).  The total energy transferred peaks at about 25% depth of
discharge (DoD) at around 4500 KWH/unit and 4000 cycles (figure 500
cycles/year for a commuter car recharged at work, that's 8 years).
Even at 50% DoD, the lifetime is something like 1200 cycles; that's
2.4 years at 500 cycles a year.

The commutercars.com site mentions that the cost of operating the Tango
would be about half that of gasoline (presumably at current prices); I'm
assuming that this is at the minimum-cost point.  This appears to be borne
out by the figures from the supplier.  The cost of operating the electric
vehicle would be much smaller than that of gasoline if all the external
costs (such as defense of the Persian Gulf) was included in the price of
imported oil.

Looks like people could find this attractive today if EV charging slots
were common, and extremely attractive if oil prices rose by a whole lot.
Once vehicles were using a lot less oil, their contribution to atmospheric
CO2 levels (and thus global warming) could be reduced greatly.

6 responses total.

#1 of 6 by gull on Sat Oct 5 04:25:02 2002:

...except that a lot of the charging power would come from oil, anyway.

#2 of 6 by rcurl on Sat Oct 5 06:09:13 2002:

More likely coal (at even higher CO2 burden/kwh). 

It is interesting (if true) that running the vehicle on electricity rather
than gasoline would simply cost less per mile driven. I suppose this
would come from the higher efficiency of central electric power stations
running on a cheaper raw material (coal). But doesn't gasoline carry a
heavier tax burden, which is also something that contributes to its
greater cost? I think the "balance" between electricity vs liquid fuel
depends on a very large number of factors that are also manipulateable.

#3 of 6 by russ on Sun Oct 6 12:53:35 2002:

Re #1:  Peaking power tends to come from gas these days, base load
from coal or nuclear.

Re #2:  Depends on the plant, but it wouldn't surprise me if the coal-fired
plant emits less CO2 per KWH at the wheels than a gasoline engine idling
in rush-hour traffic.  The electric car "idles" for free.

I seem to recall that the Federal gasoline tax is about $0.19/gallon,
and the state tax is somewhat smaller than that.  This is *maybe* 20%
of the price of fuel at the pump, so electricity would be cheaper than
that even if the fuel tax disappeared (or an equivalent tax was levied
on electricity for road use).  That changes the ratio from ~50% to ~70%.

If my proposed $3.50/gallon political-risk tax were levied on gasoline,
the current tax differential disappears into the noise.

I think the interesting part of this is that a large fleet of electric
(and especially grid-chargable hybrid) vehicles offers the utilities a
huge dump load which can be used to manage imbalances or soak up supplies
from spotty sources.  Take photovoltaic power; the big payoff for PV is
supposedly by offsetting afternoon peak summer loads, but they produce
plenty in the morning when the A/C isn't running flat-out yet.  Now fill
the parking lot with a bunch of cars with 20 KWH of battery capacity on
board, and each one of them is down about 20% when it gets there.  The
obvious thing to do is to dump about a KW into each car from 8 AM until
noon, then offset the A/C load from 1 PM to 7 PM.  This has the effect of:

1.)     Taking peak loads off the grid, cutting peaking requirements.
2.)     Eliminating emissions from the vehicles.
3.)     Distributing generation to minimize load on the grid.
4.)     Reducing the net cost of transportation.

Four birds, one stone.

#4 of 6 by rcurl on Sun Oct 6 18:56:32 2002:

Where have you been, russ? The total tax is 42 cents/gal. From a web site: 

"The 42 cents in taxes comes from three different sources: first, the
federal government imposes a tax of 18.4 cents per gallon on all gasoline; 
second, the Michigan state sales tax of 6 percent is the levied on top of
the federal tax (yes, motorists even pay sales tax on the federal tax!); 
and, finally, Michigan adds its own 19 cent per gallon state gasoline tax
on the top of all of this.  In the end, about a third of the price paid at
the pump goes to taxes. "

#5 of 6 by russ on Mon Oct 7 02:05:30 2002:

Okay, I stand corrected on the gas tax.  It isn't about 20% of the
price of a gallon of regular gas, it's more like 25-28%.  (My excuse?
I wasn't able to check when I was writing that.  Good enough?)

My point about current fuel taxes vanishing into the noise if a
political risk/Al Qaeda financing/fossil carbon fee of $3.50/gallon
is added to the current price still stands.

#6 of 6 by rcurl on Mon Oct 7 05:35:32 2002:

The point being discussed was the fuel cost of electric vs gasoline car
transportation. 

Steps to be taken to use less fuel, by technology and by financial
policies, are another matter.

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