There is one overriding advantage of kg/100 km (or g/km) over MJ/km - it bears a close relationship to the amount of CO2 being produced which is itself a cost.
_____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of lps Sent: 14 July 2008 23:10 To: U.S. Metric Association Cc: U.S. Metric Association Subject: [USMA:41416] Re: Newton for automobile efficiency Here are the energy values for various fuels. I took this from http://en.wikipedia.org/wiki/Gasoline I removed the imperial measurements. My car averages about 7 L/100 km using premium gasoline or 2.765 MJ/km Interestingly my diesel generator uses 2 L/h to generate 5000 kW・h. Does that mean that 77.2MJ of diesel fuel (2 liters) generates 18 MJ of electricity in one hour? Assuming it is under full load. This makes me wonder how much actual power is output by a liter of fuel in my car. I am sure not all of the energy is transferred from the fuel into forward motion. Fuel type <http://en.wikipedia.org/wiki/Gasoline> ↓ MJ/litre <http://en.wikipedia.org/wiki/Litre> <http://en.wikipedia.org/wiki/Gasoline> ↓ MJ/kg <http://en.wikipedia.org/wiki/Gasoline> ↓ Research <http://en.wikipedia.org/wiki/Octane_rating> octane number (RON) <http://en.wikipedia.org/wiki/Gasoline> ↓ Regular Gasoline 34.8 44.4[11] <> Min 91 Premium Gasoline 39.5 Min 95 Autogas (LPG) (60% Propane + 40% Butane) 26.8 46 108 Ethanol 23.5 31.1[12] <> 129 Methanol 17.9 19.9 123 Butanol 29.2 91-99 Gasohol (10% ethanol + 90% gasoline) 33.7 93/94 Diesel 38.6 45.4 25(*) Aviation gasoline (high octane gasoline, not jet fuel) 33.5 46.8 Jet fuel (kerosene based) 35.1 43.8 Liquefied natural gas 25.3 ~55 Hydrogen 121 130[13] <> STANLEY DOORE wrote: You're correct Jim. J/m is probably the best all-around choice for the purpose. We don't know what standard, medium grade and high-test gasoline or diesel are anyway. The k cancel out as you've implied. Now to get to the bottom line of easily understood and useable cost presentation. Stan Doore ----- Original Message ----- From: "James Frysinger" <mailto:[EMAIL PROTECTED]> <[EMAIL PROTECTED]> To: "U.S. Metric Association" <mailto:[email protected]> <[email protected]> Sent: Monday, July 14, 2008 12:41 PM Subject: [USMA:41410] Re: Newton for automobile efficiency Conveniently, an energy cost in kJ/km is numerically equal to that energy cost in J/m. In fact, they ARE identical algebraically. Thus one can quote a figure in kJ/km to the public while using that same number in calculations in the lab or design shop. This is convenient when databases or spreadsheets are used, since the units are normally carried in separate fields or cells. Wind speeds are a different matter, of course. A wind speed in km/h is NOT numerically equal to that wind speed in m/s. One must take care lest a Martin-Lockheed event occur (mixing numbers with incorrect units). Jim STANLEY DOORE wrote: Pat et al. Yes Pat, J/m is cleaner and consistent with the SI; however, people don't relate very well to meters when traveling without having to make a conversion. We found years ago that the Soviet Union used m/s in reporting wind speed instead of knots in reporting their weather observations. That didn't go over very well. However, we used m/s in our numerical analysis and forecast models (and still do) for computational reasons by converting whatever the countries, including the US, reported for wind speed to m/s as our standard. We made the conversion even for the US observation reporting system from miles per hour and/or knots to m/s too since the US used both. In the 1970s I tried to get all US agencies to take observations in m/s but that didn't go over very well, including readouts for new automatic wind speed devices. I don't know what the NOAA, DoD and other US agencies observation standards are today. I think the FAA still uses knots. Regards, Stan Doore ----- Original Message ----- *From:* Pat Naughtin <mailto:[EMAIL PROTECTED]> <mailto:[EMAIL PROTECTED]> *To:* U.S. Metric Association <mailto:[email protected]> <mailto:[email protected]> *Cc:* USMA Metric Association <mailto:[email protected]> <mailto:[email protected]> *Sent:* Saturday, July 12, 2008 7:41 PM *Subject:* [USMA:41403] Re: Newton for automobile efficiency On 2008/07/12, at 7:46 PM, STANLEY DOORE wrote: 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 Dear Stan and All, Using the figures from http://www.bwl.admin.ch/themen/00509/00528/index.html?lang=en it follows that walking at a comfortable speed of 4 kilometres per hour would require using energy at a rate of 150 kilojoules per kilometre. I think that I would be more comfortable if this was expressed as 150 joules per metre. This would meet a number of conditions: 1 It would comply with the ISO SI Guide (English Edition 2 2008) rule (page 10) that: /Prefixes in the denominator should preferably be avoided./ 2 It also uses the ISO SI Guide rule (page 10) that /The prefix /(for the numerator)/ should generally be chosen so that the numerical value will be between 0,1 and 1000, …'/ 3 Far less importantly, it complies with my suggestion that you can make calculations easier, and communication much better, if you choose SI prefixes and units so that the range of values likely to be used with that prefix/unit combination will fall into the range of whole numbers without common or vulgar fractions and without decimals (See: http://www.metricationmatters.com/docs/WholeNumberRule.pdf ). Some other approximate values (to compare with walking) are: Cycling 80 joules per metre Walking 150 joules per metre Jogging 270 joules per metre But note that some human activities take much more energy Swimming 60 000 joules per metre For motor transport (numerical factors from http://bioenergy.ornl.gov/papers/misc/energy_conv.html ) Motor bike 150 joules per metre Car 300 joules per metre Truck 600 joules per metre Cheers, Pat Naughtin PO Box 305 Belmont 3216, Geelong, Australia Phone: 61 3 5241 2008 Metric system consultant, writer, and speaker, Pat Naughtin, has helped thousands of people and hundreds of companies upgrade to the modern metric system smoothly, quickly, and so economically that they now save thousands each year when buying, processing, or selling for their businesses. Pat provides services and resources for many different trades, crafts, and professions for commercial, industrial and government metrication leaders in Asia, Europe, and in the USA. Pat's clients include the Australian Government, Google, NASA, NIST, and the metric associations of Canada, the UK, and the USA. See http://www.metricationmatters.com/ for more metrication information, contact Pat at [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> <mailto:[EMAIL PROTECTED]> or to get the free '/Metrication matters/' newsletter go to: http://www.metricationmatters.com/newsletter/ to subscribe.
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