Compressed natural gas (CNG) is being studied regarding for it performs in sub-freezing temperatures and for how its fueling procedures can be accelerated to be more in line with that of liquid fuels.

In regard to winter performance, a Canadian study has found CNG does fine in severe cold winter weather with a number of common-sense precautions that apply to other fuels, such as diesel, as well. The Canadian Natural Gas Vehicle Alliance (CNGVA) is circulating a recent "Evaluation of Winter Performance of CNG Refuse Trucks," completed by Ontario-based consultants Alex Lawson and Neil Cooke, chairman of the transportation, math and science school at Red River College in Manitoba.

The researchers studied refuse fleets operated by EBI in the greater Montreal area and Emterra Environmental in Winnipeg, concluding that the biggest potential hindrance to CNG in cold temperatures is excessive water content in the fuel, which can be mitigated. The colder the temperature, the drier natural gas used in vehicles has to be, they said.

So fuel quality and contaminants are the most common issues that can undercut performance, and the CNGVA is circulating the study to help educate fleet operators to take precautionary steps, such as having a dryer at fueling sites.

Separately, at the North America Natural Gas Conference and Expo in Atlanta earlier in November, a new solenoid valve and Tuffshell Ground Storage module were demonstrated as the next potential advance in speeding up CNG refueling for heavy-duty vehicles.

Hexagon Lincoln said the solenoid valve is aimed at the fast-fill needs of heavy-duty CNG trucks. Hexagon has an agreement with OMB Saleri to use its new "Miami" solenoid valve, which is designed for heavy-duty CNG vehicles.

"The Class 8 CNG truck application has unique requirements, and large capacity cylinders and fast filling capability are critical in this environment," said Chet Dawes, Hexagon Lincoln vice president for CNG automotive products. "Traditionally, CNG has experienced slower fill speeds than liquid fuels. This new valve helps to improve performance in CNG filling while offering a safety advantage over manually operated valves."

Hexagon also touted a new stationary storage module using a 26.7-inch diameter Tuffshell CNG cylinder. It is described as "lightweight," making it easier to move and stack and store natural gas at the fueling facility.

In Canada, the 42-page report on heavy-duty CNG refuse trucks examined the 18 CNG-fueled Peterbilt trucks operated by EBI, which is establishing a network of public-access fueling locations in the Montreal metropolitan area. It also examined the 58 CNG-fueled Crane Carrier trucks operated by Emterra.

The conclusion is that in addition to a dryer to keep water content low in the CNG, fleet operators also need to take steps to avoid contamination of the CNG in winter from compressor oil getting into the gaseous fuel.

As occurs with diesel engines when operating climate becomes colder, more preventive maintenance and attention is required, such as "vehicle modifications, vehicle preparation, operating practices and maintenance procedures" that are typically required to ensure satisfactory vehicle operation, the report said.