Talk:Gasoline gallon equivalent

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THERE IS A SERIOUS ISSUE WITH THIS ARTICLE. Most of the references for the heat content of fuels reference an About.com article. Those articles are low grade consumer fluf articles written bo just about anyone. While the numbers seem in the right ballpark, there source referenced has no real credibility and follows no academic or journalistic guidlines. The source of hard numbers in this article needs to be more rigorously refrenced. Scientific data and constants should be taken from more appropriate sources. Often you can find THE definitive source. For example, there are certain books that are widely considered to be the definitive reference for certain constants and such. For example , you might use such a source to cite when stating pi to 100 digits. However, an article on about.com stating the digis if pi would be innapropriate. Similarly,an article in a newspaper that stated it would be a poor choice as well. A better choice would be something like the CRC Handbook of tables and formulas.For something like this, your best bet is to find a good source that's documented it's information and track those back to double check, and cite things approprately

Opening comment

Here is the original gasoline-equivalent gallon article. I think it's all included in the GGE article, but I'll put it here in case I missed something Ephdot (talk) 14:14, 21 March 2008 (UTC) " A gasoline-equivalent gallon is a concept used to compare the energy content of gasoline and alternative fuels, which often have different caloric values than gasoline. Therefore, in order to properly compare prices between fuels, they may be sold in quantities energetically equivalent to a gallon of gasoline.

The energy content is determined by a fuel's enthalpy of combustion. This, however, can be problematic. Different fuels tend to be more efficient than others. Ethanol, for example burns more slowly and at a lower temperature than gasoline. This makes it easier to extract the chemical energy stored inside it. While a gallon of gasoline has about 50% more energy than ethanol, cars that run on ethanol can get very similar mileage to gasoline powered vehicles when they are optimized to take advantage of ethanol's higher octane rating. This optimization involves increasing the gasoline engines compression ratio from a normal of 9 or 10 to one, to as high as 16 to one. This involves significant and expensive refitting with different pistons (to reduce the combustion chamber size) and mechanical alterations to assure valve to piston clearance. When this optimization is completed, the engine is no longer suitable to operate on 100% gasoline, as the high compression ratio will cause severe knocking (which is very harmful to the engine). Ordinary consumers driving a "flex-fuel" vehicle can expect a substantial drop in fuel mileage when using 85% ethanol products (the compression ratio is fixed mechanically, and electronic sensors can only modify the timing of the spark and allow the electronic fuel injectors to provide more of the reduced BTU value fuel).

Very confusing and misleading !

"Notice that energy content cannot be fully converted to mechanical energy due to the limited thermal efficiency of a heat engine. Electricity is a carrier of energy, usually from one mechanical device to another. Thus an electric vehicle that is said to operate at around 90% efficiency (Tesla Roadster) actually operates in conjunction with a utility electric generating system that operates at 34% (US national average for fossil fuel generation). Typical automobiles are said to operate at around 15% efficiency.[5] However, the specially designed gasoline engine in the Prius is said to achieve better than 30% efficiency. Thus, the previously referenced Tesla Roadster actually operates at a system thermal efficiency that is modestly better than the Prius efficiency, after making some allowance for the electric part of the Prius system."

The Prius engine might be 30% efficient at a specific running point. It is not ALWAYS 30%. It won't be 30% efficient operating at part load. 30% efficiency is darn hard to attain with a gasoline engine.

The 15% automobile efficiency you are referring to is actually overall engine efficiency and takes into account idling, part load, etc. On top of that, you must deduct transmission losses, differential losses, etc. Cars are not 15% efficient overall.

Modern power plants are about 50% efficient. Combined cycle, etc. There is no way the US average is 34% efficient, especially if you consider solar and wind which are assumed 100% efficient.

A Tesla Roadster is not 90% efficient. The motor in the Roadster might might be 90% efficient, but what about the charge discharge cycle, the motor controller, the drive train, etc ?

Then there is the regeneration factor, which nobody seems to account for. In stop and go traffic, its huge.

This page needs a lot of work. —Preceding unsigned comment added by Elmerfud (talk • contribs) 15:48, 1 May 2008 (UTC)

Engine Efficiencies

I removed this section because it really does not belong into the GGE article. The GGE article is about a unit of energy that is consistent across different fuel types. This paragraph is about the conversion from fuels to mechanical energy, which is always lossy. Let's find a better home for this.

"Note that energy content in an internal combustion engine cannot be fully converted to mechanical energy due to the limited thermal efficiency of a heat engine. Electricity is a carrier of energy, usually from one mechanical device to another. Thus an electric vehicle that is said to operate at around 90% efficiency (Tesla Roadster) actually operates in conjunction with a utility electric generating system that operates at 34% (US national average for fossil fuel generation). Typical automobiles are said to operate at around 15% efficiency. However, the specially designed gasoline engine in the Prius is said to achieve better than 30% efficiency. Thus, the previously referenced Tesla Roadster actually operates at a system thermal efficiency that is modestly better than the Prius efficiency, after making some allowance for the electric part of the Prius system."

Kgrr (talk) 12:58, 9 October 2008 (UTC)

References

BTU per gallon of gasoline

• 1 kilowatt hour = 3,412.14163 BTU

But nobody seems to know how much energy is supposed to be in a gallon of gas.

• 1 Gallon = 124,000 Btu (rounded to nearest 1000)(based on U.S. consumption, 2007)DOE
• 1 Gallon = 115,000 Btu ORNL
• 1 Gallon = 114,100 Btu About.com
• 1 Gallon = 114,063 Btu NAFA.org
• 1 Gallon = 114,000 Btu EPA
• 1 Gallon = 110,400 Btu/gallon in California [www.vta.org/bart/documents/final_eir/vl_1_ch_4_08_energy.pdf VTA]

• 1 Gallon = 114,000 Btu/gallon according to NIST. They came up with the GGE concept in 1994.NIST

I will assume NIST's figure for 114,000 Btu per gallon of base gasoline is their standard, since they are the ones behind the GGE concept. EPA's figure agrees with this in most places. Kgrr (talk) 16:02, 1 January 2009 (UTC)

Even some government institutions cannot be internally consistent:

• 1 Gallon = 115,400 Btu/gallon ORNL

This figure seems to gain a lot of traction:

• 1 Gallon = 114,264 Btu/gallon AFDC
• 1 Gallon = 114,264 Btu/gallon Province of Alberta, Canada
• 1 Gallon = 114,264 Btu/gallon Chemistry course

Kgrr (talk) 15:07, 2 January 2009 (UTC)

But what is "gasoline"? Surely the exact chemical composition varies, and this accuonts for the variation in BTU/gallon? If you had pure octane or pure nonane or whatever, it would have a consistent heating value...but gasoline is m ade up of dozens (hundreds?) of chemical species. --Wtshymanski (talk) 20:34, 11 December 2009 (UTC)

article says "GGE calculated for gasoline in US gallons at 114000 BTU per gallon," but this is slightly off from the more recent Miles_per_gallon_gasoline_equivalent and standardized ""EPA's formula, in which 33.7 kilowatt hours (121.32 megajoules) of electricity is equivalent to one gallon of gasoline" which is 114989.17 BTU, only one percent off, but still should be reconciled. Will do, sans objection. Also, add column kWh/liter, more SIish. GangofOne (talk) 01:15, 2 August 2015 (UTC)

There is a fairly wide range of gasoline formulations in any one place, and many more around the world. Any attempt to make this page useful will select a reasonable average value. It should be identified as such. 2600:1009:B166:2ED2:28A0:D57C:3DB1:640C (talk) 12:12, 9 April 2019 (UTC)

Table Values Off

How can diesel have more energy per gallon yet be equivalent to fewer equivalent gallons of gasoline? The values in the table likely need to be inverted. By the way, I remember from a standard engineering text, Internal Combustion Engine Fundamentals by John B. Heywood, that gasoline typically contains 45 MJ/kg. kevinthenerd 19:30, 7 February 2010 (UTC) —Preceding unsigned comment added by Kevinthenerd (talk • contribs)

Edit: I see what the table is trying to show now, but it should be made clear that the measurements in the table are for the substance on the left, not the gasoline. Perhaps "amount equivalent to 1 US Gallon" should be used instead. kevinthenerd 19:33, 7 February 2010 (UTC) —Preceding unsigned comment added by Kevinthenerd (talk • contribs)

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As to the reference used for some of the GGE values of the table, here there is one I believe is much more reliable, and which has the same information.

https://www.afdc.energy.gov/afdc/prep/popups/gges.html

I hope this helps. However, if even governmet entities cannot agree as how much energy a gallon of gasoline has, then this reference might not be as reliable as I first thought.

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—Preceding unsigned comment added by 190.45.220.130 (talk) 02:26, 1 September 2010 (UTC)

reverts

It's better to link to standard conditions than to make an editorial comment in the article. --Wtshymanski (talk) 00:50, 12 May 2010 (UTC)

There are no standard conditions stated in the cited reference. In fact, the article is talking about natural gas and the cite is talking about COMPRESSED natural gas. Totally made up data. The wikipedia article does not state temperature or pressure at 126 cubic feet. PV=nrt is the law of gases. (Physics 101). That could be 63 cubic feet at twice the pressure or 32 cu feet at 4 times the pressure. A natural gas car would have pressurized container. Stating a volume without the pressure or temp is worthless. Find a better data point.... Let's delete the whole 126 cu feet until a better cite is found. 71.131.7.24 (talk)

that's why the link to standard conditions is needed. Why would anyone give a gas volume other than at standard conditions without giving the conditions? let's check the maths, anyway. 1 cubic foot of natural gas has a mass of 4.392 lbs per 100 cubic feet at 60 f and 14.7 psig, according to http://www.epa.gov/nvfel/methods/ngfe.pdf. This article says a gallon of gasoline energy is equivalent to the energy from 5.66 lbs of natural gas. 5.66/4.392 = 128.87 cubic feet. shock, horror, off by 2%. Of course the density of natural gas varies, too. --Wtshymanski (talk) 01:20, 12 May 2010 (UTC)

Put the correct cite in. Current cite is about COMPRESSED natural gas, but the sentence in the article is about UNCOMPRESSED natural gas. Cites belong in the article, not in the discussion. Also, the cite you give is several calculations away from what is stated. I don't mind if you include calculations in the article, but it has to be cited and presented in a manner an encyclopedia user can use or understand. Most users are not that smart. And citing 14psi is not a real world example. 99.99% of natural gas pipes and automobile CNG fuel tanks are many times the pressure and this sentence is MISLEADING by using 14psi. No auto fuel tank would be at 14psi and the subject is Gasoline equivalent (which implies cars, the biggest users of gasoline). 71.131.7.24 (talk)

I've lost track of your point in all this. What is it that you want the article to say? Do we have to teach the gas laws in ever single article that mentions gasses, or can we trust that our references are written by people who are competent? (We can't trust Wikipedia editors to be competent for obvious reasons.) Your contempt for encyclopedia readers is not a desirable quality in an editor; it's much better to be in the "Look at this...isn't it cool? And did you see this and that and over here, too." mode than the "I'm much smarter than you, you poor schmuck, let me lecture you in a patronizing and arrogant manner." mode.

The cite I referenced above was a reference for the density of natural gas, which I didn't want to guess at from CH4 molecular weight and recollection of the volume at STP from chemistry class 35 years ago. Possibly the cite above would support 126 cu ft of natural gas is about 1 gallon equivalent. Check it out! --Wtshymanski (talk) 13:34, 12 May 2010 (UTC)

SI Units please

This article would be much more useful if it used standard metric SI units Joules, Watts, litres or at least provided the SI equivalents when using the strange US measure like BTU and gallons. —Preceding unsigned comment added by 83.104.53.197 (talk) 11:57, 24 December 2010 (UTC)

I had the same thought, I did not find a quick answer to a basic question. 1 gallon of gasoline is equivalent to about 120 megajoules. — Preceding unsigned comment added by 2601:600:9500:3180:A4FF:24FE:27F:FC6 (talk) 20:02, 21 June 2019 (UTC)

Gallons to Gallons (vs. SI)

What's the point of saying "1.5 gallons of ethanol are equivalent to 1 gallon of gasoline" instead of saying "ethanol contains 1.5 less energy per volume" or similar. We do not need units here at all. Such gallon-to-gallon units should be scrapped and deleted from the history of "science". It is as if saying "1 kg of eggs is worth 3 kilograms of milk calories" instead of just giving the actual caloric values. — Preceding unsigned comment added by 93.89.198.12 (talk) 12:50, 17 February 2015 (UTC)

Big error in "GGE calculated on Non-Liquid Fuels" table.

I haven't edited an article before, so perhaps someone else who is more familiar with editing would be kind enough to correct the following described error in the article.

There is a big error in the energy density figures in the "GGE calculated on Non-Liquid Fuels" table in the article. The error would lead to completely erroneous conclusions in the current debate on natural gas as an alternative to gasoline or diesel as motor vehicle fuels.

Currently, the article has uncompressed natural gas at standard temperature and pressure is listed as "Compressed natural gas"! CNG is a totally different fuel source than uncompressed nat gas at STP.

Unpressurized nat gas takes approx 127 ft2 for each GGE, which means it is 1000 TIMES LESS (Approximately 1000 gallons of liquid in 127 cubic feet) energy dense than gasoline! With such low energy density relative to gasoline, CNG vehicles would be completely untenable, as one would need to tow a small blimp of nat gas behind your car.

Later in the article, the all the correct numbers are present in the "Compressed Natural Gas" text section. (But again the table is all wrong, as it doesn't have CNG listed, just uncompressed NG in a row mistakenly labeled CNG.)

CNG is defined as natural gas at 2900-3600 psi. At these pressures, it has approximately 1 GGE per .5 cubic foot, (or 2 GGE per cubic foot), which gives approximately 1/4 the energy density to CNG compared to liquid gasoline.

As a newb, I'm not comfortable editing the article, and one would need to do the math out to a few decimal places, but essentially the existing line in the table listed as "Compressed Natural Gas" needs to be changed to "Uncompressed Natural Gas at STP", and a new line needs to be added titled "Compressed Natural Gas", showing it with the (approximately) correct 2 GGE of CNG per cubic foot. — Preceding unsigned comment added by Zmkk (talk • contribs) 17:20, 8 June 2012 (UTC)

Another error in Non-Liquid Fuels - nitromethane, with a melting point of -29°C and a boiling point around 100°C, is certainly as "liquid" as any other common liquid fuel, and when used as a fuel it is used as a liquid, or as part of a liquid mixture. I have moved the nitromethane data to the bottom of the Liquid Fuels table, but I have not verified the numbers. Sensible jones (talk) 20:14, 1 February 2016 (UTC)

External links modified

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e100 higher than e85?!

Can it be that ethanol e100 has a higher gge and lower kw/h produced per gallon than e85?! This seems not possible. Is it a mistake?פשוט pashute ♫ (talk) 16:14, 14 February 2017 (UTC) E-85 is 15% gasoline, which has a higher energy content than ethanol. So of course E-85 has to have more energy per volume than E-100 which is 100% ethanol. — Preceding unsigned comment added by 75.162.88.156 (talk) 02:17, 14 November 2018 (UTC)

The representation shows gallons of ethanol equal to one gallon of gasoline. It is correct. The higher GGE value indicates lower heat value. 2600:1009:B166:2ED2:28A0:D57C:3DB1:640C (talk) 12:17, 9 April 2019 (UTC)

External links modified

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EV's versus Gasoline

The average electric vehicle on the road in the U.S. in 2018 gets 3 - 5 miles per KWh, which is about 6 - 9 KWh's per gallon equivalent. Allowing 20% heat loss during charging that is about 7 - 11 KWhs per gallon equivalent. The difference between this rate and the rate on the page is that the rate on the page is the heat content of KWh's, while electric motors are 100% efficient and gasoline motors (internal combustion engines or ICE's) are approximately 16% efficient.

One other comment noted the inefficiency of the production of electricity but did so out of context. Their example was for 100% coal and there is no place in the U.S. where you can buy electricity which is 100% coal. (All grid power is blended - you could obtain 100% coal generated electricity directly from any coal plant or any transmission line connected to one of those plants). Wind and solar have no relevant heat loss rate, as do other renewable resources. Natural gas could theoretically be 62% efficient as an electric fuel, but the national average is ~45%. There are theoretical inefficiency rates for renewables, but they are not heat loss rates. For this page, it is probably appropriate to treat electricity as a fuel the same way we don't count the BTU heat input used for petroleum and natural gas extraction - which is substantial. Other pages can address energy return on investment and similar metrics.

I'm not able to identify good references that speak directly to this point - not now, and I'm a novice on Wikipedia so I don't want to edit. I already posted one note somewhere else which seems to be an orphan page. I don't know if I will ever figure out how to delete that message. 2600:1009:B166:2ED2:28A0:D57C:3DB1:640C (talk) 12:07, 9 April 2019 (UTC)

It seems to me that the purpose of this table is for consumers to compare what they can buy. Buying gasoline at the corner station, the price already includes costs or production and refining. Electricity from the power company includes inefficiencies of generation, transmission, equipment (distribution) costs, and such. Natural gas, as delivered to houses, is not CNG, so the compressor would need to be added. Gah4 (talk) 19:34, 18 May 2020 (UTC)

CO2

Would it be too much, assuming WP:RS, to put the CO2 of combustion for carbon based fuels? Maybe there would be another article for it, but this seems like a good place. Gah4 (talk) 19:36, 18 May 2020 (UTC)