Hydrogen, batteries, gasoline, diesel, biofuel, etc. How to compare the
energy and efficiency of these?
Why not J/km (Joules per kilometer) as the common unit of SI measurement?
Cost per kilometer is really what we want to know for economic purposes isn't
it?
Stan Doore
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----- Original Message -----
From: Nat Hager III
To: U.S. Metric Association
Sent: Thursday, July 10, 2008 4:34 AM
Subject: [USMA:41377] FW: Impressions of a Futurecar - FlowChart (usnews.com)
Sorry, missed the most controversial part..
Hydrogen car article in US News...
>>>Kilograms per what? The Hydrogen 7 has one of those onboard computers that
display your fuel efficiency-for both gasoline and hydrogen. Gas mileage, of
course, is measured in the familiar mpg. But hydrogen mileage is flipped around
and expressed in kilograms per 100 kilometers. This took a bit of noodling to
understand, like figuring out the inverse of a currency exchange in a foreign
country. Simply put, it's the metric version of how many gallons it takes to go
100 miles. If you're averaging 4 gallons per 100 miles, for instance, that's
the same as 25 miles per gallon; 3 gallons per 100 miles would be 33 mpg. So in
hydrogen terms, the lower the number, the better.
I started out averaging 3.3 kilograms of hydrogen per 100 kilometers. I tried
to drive gently and see if I could improve on that, and I got it down to 2.9
for a while. Then I hit traffic, and it went back up to 3.2. I studied the
instant efficiency reading, too, which ranged from 0 to 10. When coasting at
about 50 miles per hour-a very efficient speed for most cars-my hydrogen
consumption was less than 2 kilograms. But when pressing hard on the
accelerator to pass somebody, I pegged the meter, burning the maximum 10
kilograms (or more).
If hydrogen catches on, there will have to be standardized metrics for
expressing fuel economy. My guess is that the federal government will adopt
something similar to the mpg construct, while taking account of the fact that
hydrogen is typically measured by weight, not volume. So an Americanized
version might be expressed as miles per pound. If that were the case, my 3.3
kilograms per 100 kilometers would equate to about 8.5 miles per pound of
hydrogen. I think. Or maybe we'll just have to join the rest of the world and
learn the metric system.
>>>
http://www.usnews.com/blogs/flowchart/2008/7/9/impressions-of-a-futurecar.html
Nat
