Do you mean I have to solve the problem, not just complain about it? :) That seems fair!
For gasoline and diesel, most of the rest of the world uses liters per hundred kilometers. To properly consider alternate fuels, I would suggest that all fuels be represented by their Lower Heating Value* (energy content), not their volume or mass. The obvious representation to closely parallel the existing would be megajoules per 100 kilometers for ALL fuels. (A kilowatt-hour of electricity is 3.6 MJ) However, the numbers are getting small, and the 100 factor departs from the usual steps of 1000-fold in units. I believe it would be better to multiply by 10 and use megajoules per 1000 kilometers (which could be expressed as a megameter). Alternatively the megas could divide out leaving joules per meter, certainly better in computation, but another representation might be more relatable to the public, and easier to tie to meaningful driving distances and volumes or masses of fuel. I would note that 1000 km is a reasonable monthly driving distance for many people, and the cost per 1000 km would be a reasonable budgetary visualization. *Some may be unfamiliar with LHV. Fuels have two heating values, Lower and Higher Heating Value, LHV and HHV. Fuels burn to CO2 and H2O (Hopefully, there are small amounts of various pollutants). The water is usually in the form of vapor. HHV assumes the heat of vaporization can be usefully extracted and put to some purpose. LHV assumes it is lost in the exhaust. HHV is important for theoretical thermodynamics and some applications. For an internal combustion engine, LHV better corresponds with how an engine will utilize alternative fuels, and is the most useful way to measure energy-adjusted amounts of fuel. Bottom line: The 28 kW·h/100 mi should be 626 MJ/Mm (or J/m) Airlines like to express their fuel economy per passenger-mile, but they cheat and count seats, not passengers. To compare to alternate modes of public transportation, perhaps automotive fuel economies should be divided by the number of seat positions. However, I acknowledge that automobiles often have lower occupany (1 of n) than public transportation which may have occupancy of 50-100%. To compare oranges and apples, you have to decide how to compare the entire class: "fruit" as a minimum, possibly "food." ________________________________ From: Ron Stone <[email protected]> To: [email protected]; U.S. Metric Association <[email protected]> Sent: Sun, June 26, 2011 7:49:06 AM Subject: Re: [USMA:50747] Re: MPGe = miles per gallon equivalent? On Sun, Jun 26, 2011 at 4:48 AM, Ron Stone <[email protected]> wrote: many of us may still be wondering how might MPGe be represented in SI (metric) terms. > > > >On Sun, Jun 26, 2011 at 4:26 AM, John M. Steele <[email protected]> >wrote: > >I must call foul, but I am unclear whether I am calling foul on: >>*EPA's methodology >>*Tesla's honesty >>*Andrew's investigative reporting and numeracy >>Quoting from the article, >>## >>Now Tesla has raised the stakes again by introducing the Tesla Roadster 2.5 >>that >>boasts an MPGe rating of 112 MPGe on the highway and 124 MPGe in the city. >>This >>combined rating puts the overall MPGe for the Roadster 2.5 at 119 MPGe. >>When the new 2.5 Tesla Roadsters will become available is anyone's guess. >>However, with the original Roadster boasting an overall MPGe rating of 111 >>the >>improved 2.5 model is undoubtedly going to be a success. One interesting >>thing >>to point out is that other than the more efficient MPGe rating the rest of >>the >>Tesla Roadster 2.5 statistics remain unchanged from its predecessor; i.e. >>annual >>fuel costs, approximate range, and kW-hrs per 100 miles. >>## >> >>119 MPGe and 111 MPGe can not BOTH be represented by 30 kW·h/100 mi. Using a >>DoE data sheet (and some conversion) reformulated gasoline (would EPA use any >>other kind) is 119.87 MJ/gallon. Using this figure, I confirm that 111 MPGe >>is >>30 kW·h/100 mi, but 119 MPGe is 28 kW·h/100 mi. Obviously the useful, >>meaningful expression of fuel economy for an electric vehicle is just some >>decoration the EPA makes them throw on the label. >> >>It is not simple reporting error. The labels have been previously reported >>with >>graphics. Only fake gallons are real! >>http://green.autoblog.com/2011/05/26/epa-rates-tesla-roadster-at-111-mpge/ >>http://news.consumerreports.org/cars/2011/05/extreme-epa-window-sticker-tesla-roadster-rated-111-mpge.html >> >> >>Pat and I challenge each other on conversion. I am going to offer a new >>defense >>of conversion: >>"He who can't convert in a 'dual' society gets hoodwinked." >>I agree with Pat that we need to get past conversion and truly metricate, but >>we >>have a Congress that currently guarentees that can't happen because they >>will pass (and demonstrably have passed) laws to prevent it. I blame >>Congress, >>not centimeters. >> ________________________________ From: Pat Naughtin <[email protected]> >>To: U.S. Metric Association <[email protected]> >>Sent: Sat, June 25, 2011 11:39:40 PM >>Subject: [USMA:50743] MPGe = miles per gallon equivalent? >> >> >>Dear All, >> >> >>You will be interested in this reference from Reuters: >>http://www.reuters.com/article/2011/06/24/idUS27637249720110624 where they >>write: >> >> >>So, the EPA had to come up with a new unit of measurement in order to help >>the >>public understand all those crazy and complicated numbers. Essentially, the >>EPA >>had to dumb stuff down so people could understand what they were talking >>about- >>if the EPA has to make up a new system of measurement to replace an existing >>system of measurement that is deemed to tricky by the masses,I guess this >>sort >>of puts the final nail in the coffin for the metric system ever being adopted >>in >>the U.S. >>I emphasised the last sentence of the quote. Better still, I will repeat it >>here: >> >> >>I guess this sort of puts the final nail in the coffin for the metric system >>ever being adopted in the U.S. >> >> >>Cheers, >> >> >>Pat Naughtin LCAMS >>Author of the ebook, Metrication Leaders Guide, see >>http://metricationmatters.com/MetricationLeadersGuideInfo.html >>Hear Pat speak at: http://www.youtube.com/watch?v=_lshRAPvPZY >>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/ to subscribe. >> > > > >-- > > >----------------- >Ron Stone >---------------------------- >on Twitter (at) photonron >--------------------------------------------------------- >disclaimers or other restrictions may apply to this message. >-------------------------------------------------------------------------------------------- > > > > -- ----------------- Ron Stone ---------------------------- on Twitter (at) photonron --------------------------------------------------------- disclaimers or other restrictions may apply to this message. --------------------------------------------------------------------------------------------
