March 20, 2014

The following slides were taken from a post by Charles Murray-Senior Technical Editor, Electronics & Test. The text and commentary are mine. 

Compressed natural gas (CNG) has been a possible alternate fuel for quite some time.  Natural gas is basically methane in varying percentages due to geographical considerations and constituents found in the “mix”.   The heating value ranges between 900 and 1200 Btus/Ft³ with a nominal octane rating of 130.   One gasoline gallon equivalent (GGE) of natural gas is 126.67 cubic feet (3.587 m) at standard conditions.   GEG is the amount of alternative fuel it takes to equal the energy content of one liquid gallon of gasoline. GGE allows consumers to compare the energy content of competing fuels against a commonly known fuel—gasoline.  GGE also compares gasoline to fuels sold as a gas (Natural Gas, Propane, and Hydrogen) and electricity.

This volume of natural gas has the same energy content as one US gallon of gasoline (based on lower heating values: 900 BTU/cu ft of natural gas and 115,000 BTU/gal of gasoline).   One GGE of CNG pressurized at 2,400 psi (17 MPa) is 0.77 cubic foot (21.8 liters).   Again, 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/cu ft of CNG and 115,000 BTU/gal of gasoline. Using Boyle’s Law, the equivalent GGE at 3,600 psi (25 MPa) is 0.51 cubic foot (14.4 L or 3.82 actual US gal).

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.”

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. These facts make it an ideal alternate fuel due to minimal changes and modifications being necessary for automotive engines.  When you throw in the bio-fuel option producing a hybrid vehicle, you have a winning combination.  This eliminates problems with infrastructure not providing stations for filling CNG tanks in a judicious manner.  Let’s take a look at several vehicles to see the status of CNG/Bio-fuel development.

2015 Siverado 2500HD


FORD F-150 (2)








RAM 2500 (2)






As you can see, the automotive industry is definitely “on-board” with alternative energy and CNG is one compressed gas they are banking on for the future.  We will see commercial entry for these models in the very near future.  It will be very interesting to see how they are accepted by the marketplace.   I welcome your thoughts.  Many thanks.

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