Lord knows I have to defer to your judgment and other experts' in an

EV-making discussion.

But, with respect, on this more general science issue, I want to try

to understand something here about this relationship between energy

efficiency and mileage. I do not think there is necessarily a

linear relationship between the percentage energy efficiency and

miles per unit energy. My reasoning is something along these lines.

Theoretically, in the ideal, one can get an infinite distance from a

miniscule energy input. "A body in motion stays in motion unless

acted upon by an outside force".

So, if we had an ideal car on a non-friction surface and no

resistance (wind or otherwise), after the original "impetus" of

energy, the car should go forever. The distance traveled would be

infinite.

Now, if we include real-world performance issues of acceleration and

deceleration, wind resistance, etc. then do we come closer to a

linear mathematical correlation between energy efficiency and

mileage?

I don't know the upper limits on mileage per MegaJoule, given

idealized thought experiments or alternatively given some defined

real-world constraints (a certain weight to a vehicle, some internal

friction, acceleration and decelleration, wind resistance, etc.).

I've just always wondered about this question as to what we mean

when we say "energy efficiency" and relate it to mileage.

It seems to me I have read once or twice articles about college-type

contests where teams shoot for the most awesome mileage they can get

and throw away virtually every other consideration. The speed

traveled, the number of possible passengers, etc. etc... these

factors are all subordinated to mileage. And in those contests I'm

pretty sure the mileage figures attained have been astounding, I

think well into the hundreds of miles per gallon (but I could be

wrong... haven't seen this data for years).

In any event, I'm not sure how I should view this issue of mileage

and energy efficiency.

--- In evworld@yahoogroups.com, Rick Woodbury <rick@c...> wrote:

> Al Zelicoff, MD wrote:

>

> > 5. Yet, the MDI is advertised as being able to travel about 200

> > kilometers on an air-charge. Given that it is no more

aerodynamic than

> > battery powered cars (although it is less weighty) and that

electric

> > motors are, for all intents and purposes nearly 100% efficient in

> > converting on-board energy into movement, this suggests that the

MDI is

> > 20 to 30 times more efficient yet. That just doesn't make sense.

>

> No it doesn't. If a vehicle were 60% efficient and traveled 60

miles on a

> charge for example, as it became 100% efficient it would go 100

miles. That

> would mean no heat loss from friction, no aerodynamic drag, or any

other

> factors, i.e., impossible. Obviously 20 to 30 times more efficient

is 20 to

> 30 times impossible.

>

> There was an electric motor company in China advertising that

their motor

> was so efficient that it could get several times the range of a

conventional

> motor. Obviously they were smoking the same stuff. Current

electric motors

> are 85% efficient or more, meaning that there is very little heat

loss. If a

> motor were 100% efficient (absolutely impossible since there is

always some

> friction and other losses) it could go 15% further on a charge.

Obviously

> range must be increased by carrying more energy not so much through

> efficiency gains. A lithium-ion pack can carry many times the

energy per

> weight and volume of lead acid. That makes sense.

>

> Thanks for doing the energy calculations for compressed air. I've

always

> thought it was highly suspect, but never took the time to disprove

it. I

> know that it takes a 6 hp air compressor to run a 1 hp or less air

tool and

> the compressor can't keep up at that. There is a lot of loss in

heat when

> the air is compressed too.

>

> A compressed natural gas car can get a 200 mile range using all of

the

> energy in the gas itself from a 5,000 psi cylinder. A home

compressor works

> for many hours to reach that pressure. To think you could throw

away the

> energy in the gas and run 200 kilometers on the pressure is

ludicrous.

>

> It's hard to get 200 Wh/mi with an electric car with it's highly

efficient

> motors. How can one expect to get the same or better efficiency

out of a

> reciprocating engine. An internal combustion engine is about 13%

efficient.

>

>

> Rick Woodbury Phone: (509) 624-

0762

> President, Commuter Cars Corporation Toll-free: (800) 468-

0944

> Doubling the capacity of freeways Fax: (509) 624-

1466

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1815

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> 715 E. Sprague Ave., Suite 114 Email: rick@c...

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