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Gasoline gallon equivalent (GGE) or gasoline-equivalent gallon (GEG) is the amount of alternative fuel it takes to equal the energy content of one liquid gallon of gasoline. In 1994, the U.S. National Institute of Standards and Technology or NIST defined "Gasoline gallon equivalent (GGE) means 5.660 pounds of natural gas."1
GGE allows consumers to compare the cost of competing fuels against a commonly known fuel -- gasoline. Compressed Natural Gas (CNG) for example, is a gas rather than a liquid. It can be measured by its volume in cubic feet (CF), by its weight in pounds (LB) or by its energy content (BTU). Electricity's energy is measured in Kilowatt-Hours (kWh). It is difficult to compare the cost of gasoline with other fuels if they are sold in different units. GGE solves this. A GGE of CNG and a GGE of electricity all have the same energy content as one gallon of gasoline. CNG sold at filling stations is priced in dollars per GGE.
Contents |
Table of GGE
| Fuel | Gallon Gasoline Equivalent | BTUs/Unit |
|---|---|---|
| Gasoline (base)2 | 1 US gallon | 114,000 BTU/gallon |
| Gasoline (conventional, summer)2 | 0.996 US gallon * | 114,500 BTU/gallon |
| Gasoline (conventional, winter)2 | 1.013 US gallon * | 112,500 BTU/gallon |
| Gasoline (reformulated gasoline, ethanol)2 | 1.019 US gallon * | 111,836 BTU/gallon |
| Gasoline (reformulated gasoline, ETBE)2 | 1.019 US gallon * | 111,811 BTU/gallon |
| Gasoline (reformulated gasoline, MTBE)2 | 1.020 US gallon * | 111,745 BTU/gallon |
| Gasoline (10% MBTE)3 | 1.02 US gallon | 112,000 BTU/gallon |
| Gasoline (regular unleaded)4 | 1 US gallon | 114,100 BTU/gallon |
| Diesel #24 | 0.88 US gallons | 129,500 BTU/gallon |
| Biodiesel (B100)4 | 0.96 US gallons | 118,300 BTU/gallon |
| Bio Diesel (B20)4 | 0.90 US gallons | 127,250 BTU/gallon |
| Liquid natural gas (LNG)4 | 1.52 US gallons | 75,000 BTU/gallon |
| Compressed natural gas (CNG)4 | 126.67 cu. ft | 900 BTU/cu. ft |
| Hydrogen at Atmospheric Pressure | 357.37 cu. ft | 319 BTU/cu. ft5 |
| Hydrogen by weight | 1.004 kilograms (2.21 lb) *6 | 119.9MJ/kg (51,532 Btu/lb)7 |
| Liquefied petroleum gas (LPG)4 | 1.35 US gallons | 84,300 BTU/gallon |
| Methanol fuel (M100)4 | 2.01 US gallons | 56,800 BTU/gallon |
| Ethanol fuel (E100)4 | 1.500 US gallons | 76,100 BTU/gallon |
| Ethanol (E85)4 | 1.39 US gallons | 81,800 BTU/gallon |
| Jet fuel (naphtha)8 | 0.97 US gallons | 118,700 BTU/gal |
| Jet fuel (kerosene)8 | 0.90 US gallons | 128,100 BTU/gal |
| Electricity4 | 33.40 Kilowatt hours * | 3,413 BTU/kWh910 |
*calculated based on 114,000 BTU/gallon base gasoline
Compressed Natural Gas
One GGE of natural gas is 126.67 cubic feet. This volume of natural gas has the same energy content as one US gallon of gasoline (based on lower heating values: 900 BTU/CF of natural gas and 115,000 BTU/gallon of gasoline).11
One GGE of CNG pressurized at 2,400 psi is 0.77 cubic feet. This volume of CNG at 2,400 psi has the same energy content as one US gallon of gasoline (based on lower heating values: 148,144 BTU/CF of CNG and 115,000 BTU/gallon of gasoline.11 Using Boyle's Law, the equivalent GGE at 3,600 psi is 0.51 cubic feet which corresponds to 14.5 liters or 3.82 actual US gallons.
The National Conference of Weights & Measurements (NCWM) has developed a standard unit of measurement for compressed natural gas, defined in the NIST Handbook 44 Appendix D as follows: "1 Gasoline [US] gallon equivalent (GGE) means 2.567 kg (5.660 lb) of natural gas."12
When consumers refuel their CNG vehicles in the USA, the CNG is usually measured and sold in GGE units. This is fairly helpful as a comparison to gallons of gasoline.
Ethanol
One GGE of ethanol is 1.5 gallons. This volume of ethanol has the same energy content as one US gallon of gasoline. This is because a gallon of ethanol has a lower heat value or energy content (76,100 BTU) when compared to a gallon of gasoline (114,100 BTU).
Ethanol burns more slowly and at a lower temperature than gasoline. This makes it easier to extract the chemical energy stored inside it.citation needed 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 engine's 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).citation needed
E85
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).citation needed
See also
References
- ^ "Handbook 44 Appendix D - Definitions". NIST (2007). Retrieved on 2009-01-02.
- ^ a b c d e f "Fuel Economy Impact Analysis of RFG". US Environmental Protection Agency (2007-08-14). Retrieved on 2009-01-01.
- ^ http://www.nafa.org/Template.cfm?Section=Energy_Equivalents
- ^ a b c d e f g h i j k http://alternativefuels.about.com/od/resources/a/gge.htm
- ^ http://www.mb-soft.com/public2/hydrogen.html
- ^ http://ts.nist.gov/WeightsAndMeasures/upload/H2-Laws-and-Reg-Paper-USNWG-JUN2008.pdf
- ^ http://www.nrel.gov/hydrogen/pdfs/43741-2.pdf
- ^ a b http://www.eia.doe.gov/emeu/rtecs/nhts_survey/2001/tablefiles/c0464(2005).pdf
- ^ "Energy Conversions". Oak Ridge National Laboratory. Retrieved on 2009-01-01.
- ^ "Conserving Energy and Water - Energy Terms/Conversions". Pacific Northwest National Laboratory (2008-06). Retrieved on 2009-01-01.
- ^ a b "Properties of fuels". DOE: Energy Efficiency and Renewable Energy. Retrieved on 2008-10-08.
- ^ "Uniform Engine Fuels, Petroleum Products and Automotive Lubricants Regulation" pp.149-164. NIST. Retrieved on 2008-10-08.
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