This discussion about how to present a standard way of efficiency has two
components - technical and useful for public. the discussion so far have
evolved around the technical/scientific and not the practical use.
The bottom line is the pocketbook - what's the best way to minimize cost to
the user.
xJ/km seems to fulfill this best since it relates to every day life for
vehicles. Then prices can be posted in a standard xJ/km so people can directly
compare costs. In effect that's what the designations of regular, high test
(hi-energy), diesel grade fuels do for customers, and they give you,
indirectly, a bottom line dollar or Euro cost for efficiency to get you from
one place to another.
xJ/km then could also be used as a common denominator for the cost of
moving people or freight by rail, bus, car, air, ship, etc. which people would
understand.
Stan Doore
----- Original Message -----
From: J. Ward
To: U.S. Metric Association
Sent: Friday, July 11, 2008 12:00 AM
Subject: [USMA:41392] Newton for automobile efficiency
Perhaps newtons could be useful for energy consumption of automobiles. It
would be a way to compare vehicles with different technologies, such as
gasoline, diesel, electric, hydrogen, etc. I've seen electric vehicles
advertised with their "efficiency" expressed in miles per gallon. I assume
this is calculated by considering the chemical potential energy of gasoline if
burned in oxygen. It seems sad to start with a motor whose mechanical and
electrical powers are measured in kilowatts, with batteries supplying
electricity measured in amperes and volts, and then to bastardize these
standard units into units of equivalent gallons of gasoline. The results are
also misleading since the efficiency of the power generation were not taken
into account, e.g., how much coal was used to drive a certain distance?
Anyway, I would prefer to use newtons over generically measuring energy in
units of gallons of gasoline. Reminiscent of the dreaded BOE....
J.
