---------- Forwarded message ---------- From: Ron Stone <[email protected]> Date: Mon, Jun 27, 2011 at 12:46 AM Subject: Re: [USMA:50747] Re: MPGe = miles per gallon equivalent? To: "John M. Steele" <[email protected]>
thanks very much for explaining comparisons of fuel economy in terms of SI (metric)! this is an important topic for consumers and the public. i think that regulated comparisons of fuel economy or energy economy should be presented in terms of SI units. however if pre-metric terms (like mile or gallon) are presented as supplementary information, that would be more appropriate. i think that this topic should have its own wiki reference as 'fuel economy' or 'energy economy'. cheers, Ron On Sun, Jun 26, 2011 at 5:36 AM, John M. Steele <[email protected]>wrote: > 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. > > -------------------------------------------------------------------------------------------- > > > -- ----------------- 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. --------------------------------------------------------------------------------------------
