Metro Magazine

AUG 2014

Magazine serving the bus and rail transit & motorcoach operations since 1904

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A6 METRO-MAGAZINE.COM BUS OPS AUGUST 2014 C ompressed natural gas (CNG) is considered one of the cleanest, safest and lowest cost vehicle fuels, and it's produced in North America. However, it isn't as simple to han- dle as conventional fuels such as gasoline and diesel. Not only are there added vehicle costs, the decision to construct a CNG fueling station is a major factor in switching a feet. CNG stations are a signifcant capital and operating commit- ment that should be given full consideration before purchasing decisions are made. Here are some things for you to consider. Make a Plan for Transition Develop a plan for CNG transition early, as it is necessary to think ahead about facility design. It is possible to oversize a facility, but it is more common to undersize equipment, par- ticularly the compressor. Small compressors can lead to slow or incomplete fueling. First, assemble current fueling records: • Gallons of fuel consumed per day by vehicles that will oper- ate on CNG. Average fuel consumption for the feet should be used, not the maximum or the tank capacity. • Number of vehicles to be fueled per day, noting that CNG vehi- cles often carry less fuel than liquid-fueled vehicles, and there- fore, may require more frequent fueling. Also note the feet FLEET SOLUTIONS spare ratio must be known and applied to fuel consumption. • Fueling patterns and timing at the site. For example, do ve- hicles return to the yard for several hours a day or come only for fueling? • Will vehicles be bi-fuel CNG/gasoline or dedicated CNG? This will impact the level of redundancy required in the CNG station. Some vehicles may not be immediate candidates for CNG. These include older vehicles scheduled for disposal in the near term and low-use vehicles. Diesel vehicles are often dif- fcult to satisfactorily convert to CNG, so it may be advisable to wait until the next trading cycle and replace them with OEM- dedicated CNG engines in new vehicles. The CNG station facility should be planned and constructed to allow for CNG feet growth by designing it for the ultimate feet needs even though some equipment — additional com- pressors or storage — may not be installed at the outset. Useful Facts • 1 GGE (gasoline gallon equivalent) is defned by National In- stitute of Standards and Technology (NIST) as 5.660 pounds of natural gas. It is the equivalent energy to a gallon of gaso- line. It is approximately 120 to 125 standard cubic feet (scf) of natural gas. • 1 DGE (diesel gallon equivalent) is not legally defned, yet it is the equivalent energy to a gallon of diesel fuel and is ap- Tips for Designing a CNG Fueling Station You've made the decision to transition to compressed natural gas (CNG) for your vehicle feet — understanding CNG station options is your next step. By Rob Adams, P.E.

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