Thanks for the good info.
Incidentally, use of the unit bar and mbar was terminated years ago in
favor of the SI Unit Pascal by the NOAA-National Weather Service, the American
Meteorological Society (AMS), the World Meteorological Organization (WMO) and
other weather organizations around the world.
Mass and the kilogram (kg) is far better than volume as a base unit for
energy since materials have various densities with different energy content for
the same volume. For example, and cup of flour can have different mass
depending on how much the flour is compacted within the measuring tool (cup).
Stan Doore
----- Original Message -----
From: Stan Jakuba
To: U.S. Metric Association
Sent: Wednesday, September 17, 2008 9:54 AM
Subject: [USMA:41733] Re: Fuel rating and dispensing
It occurred to me that those interested in this subject might appreciate the
attached table.
----- Original Message -----
From: Stan Jakuba
To: U.S. Metric Association
Sent: 08 Sep 17, Wednesday 09:22
Subject: [USMA:41732] Fuel rating and dispensing
It is not Joules per kilogram but joules per kilogram. Otherwise I agree
with you as discussed several times. Indeed, fuels should be rated for their
energy (heat in this case) contents at the "pump." This was the practice with
coal for centuries. With the liquid hydrocarbons such as gasoline, the
variablity is not as great as with coal, small enough to be commonly ignored.
But the impact within the permitted range of some 42 MJ/kg to 44 MJ/kg is
detectable in a car's fuel consumption, and certainly on a dynamometer.
So it will be with hydrogen - there is no such thing as pure hydrogen when
it comes to dispensing it for public consumption. There are always other
substances present, and money can be made by increasing their concentration, in
other words, removing them less carefully. Energy density dispensing, with mass
or volume, removes that possibility for cheating.
There are parts of the world where people are billed for the energy used,
not the volume or mass of fuel burned. For example, heat meters are attached
with radiators in appartment buildings, the billing done by reading each sensor
remotely. Electrical heating is the ultimate example of the for-energy billing
(for-kWh, usually, unfortunately, rather than for-joules).
Any fuel, coal, gasoline, gas, hydrogen, should be (and is, I presume, at
the refinery or shipper's "dock") priced by its mass or volume, with, in either
case, the heat contents. The choice of mass or volume is a matter of
convenience of dispensing, the choice depending on circumstances.
Speaking of the Metric Today article, there is a sad testimony of our
regulators' ignorant attitude towards SI as the ultimate goal. Why would they
even consider the bar instead of the pascal is beyond me. Well, it just
reflects on their knowledge, the lack of it. Instead of "let's see what the
Europeans do" they should look at the historical trend towards coherence in the
formation of all derived units and follow it.
Stan Jakuba
----- Original Message -----
From: STANLEY DOORE
To: U.S. Metric Association
Cc: US Metric Assoc
Sent: 08 Sep 16, Tuesday 05:22
Subject: [USMA:41712] Metric fuel labels
Metric Today published by the US Metric Association (www.metric.org)
reports that hydrogen (H2) is proposed be sold in units of mass using the
kilogram (kg) at service pressures of 35 MPa and 70 MPa (megapascal). Tire
pressures are already shown in metric (kPa).
Using the International System of Units (SI) in the United States
begins an era which should be used to label fuels by energy content using
Joules (J) and J/kg (Joules per kilogram). J/kg is a badly needed common
denominator for energy content.
The SI would allow consumers to compare the amount of energy they are
buying/using for each type of fuel - high-test gasoline, regular gasoline,
kerosene, diesel, JP4, CNG, biofuels, a mixture of fuels like gasoline and
ethanol (E-85 & E-10), electricity, etc. It's confusing now. The SI would
bring them together for better decision-making. Mass has been used for years
for bulk fuel transportation (tons of petroleum) and mass for aircraft
refueling.
Buying fuel by energy content and mass (J/kg) would help to improve
public understanding. And, it should be linked with the kilometer (km) for
distance instead of miles. It makes sense since there is a move to change road
signs to meters and kilometers.
Stan Doore
