The EIA has a "wonderful" page to help us poor folks when dealing with
their diverse units. It's called their "Energy Calculator" and it's at
http://www.eia.gov/kids/energy.cfm?page=about_energy_conversion_calculator-basics
(Notice, that on their website this is aimed at kids! See the directory
structure above.)
Several sources of energy are listed, with some conversion factors
provided behind the screen. Just for fun, put 1000000 (that's 1 000 000
without the spaces) in the Btu column for each source. One finds that a
million British thermal units are equivalent to
1091.86844 MJ for coal,
1055.09965 MJ for electricity,
1058.14634 MJ for natural gas,
1055.05517 MJ for crude oil,
1055.05521 MJ for gasoline,
1055.08688 MJ for diesel fuel & heating oil, and
1055.10671 MJ for food in "food calories" (kcal, or "Cal").
One wonders why the values did not come out to be the same in each case!
Now, I don't believe the EIA actually uses differently sized Btus. I
think that it's just a screwed up government webpage, containing a
gremlin causing round-off errors. Well, I hope so, anyway.
Interestingly the EIA defines the British thermal unit here and there as
that energy required to heat one pound of water enough to raise its
temperature by one degree Fahrenheit. It does not specify the
temperature at which that occurs, thus suffering the same problem as the
calorie. Depending on the temperature at which that determination is
made, the value of the Btu (and the calorie) will vary due to the
non-constant heat capacity of water with temperature. For example, the
calorie at 15 °C is not the same as the calorie at 20 °C; the same is
true for the Btu. That's why the joule is much to be preferred. The
joule comes in only one size, regardless of temperature, energy source,
nationality, or creed.
Yes, barrels and gallons of petroleum products and tons of coal will
vary in energy content with the quality and properties of the particular
batch, but energy units should not vary amongst themselves.
It certainly is too bad that the EIA has chosen to defy Acts of Congress
and Executive Orders by refusing to metricate their pages of information.
I am including the EIA webmaster on this email and will report any
replies I might receive. Perhaps he or she was not aware of the coding
problem in this webpage.
Jim
--
James R. Frysinger
632 Stoney Point Mountain Road
Doyle TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
