You May Know More About LNG Vehicles Than You Think

Transportation applications for LNG. It’s a new direction ENGIE is taking for a very good reason—lots of benefits for the company, the environment, and customers. But what are the applications for LNG in transportation? It’s liquefied natural gas that’s transportable for use as a vehicle, marine, or locomotive fuel; for commercial and industrial applications; and for high horsepower applications, including diesel generators.

One market segment is LNG-powered tractors for long-haul trucking and the fueling stations that support that growth. ENGIE’s station is adjacent to the Everett LNG Terminal.

What is it like to use an LNG fueling station? Actually, it’s not that much different than a conventional gas station, except that the components of an LNG fueling station are designed to handle cryogenic temperatures.

A driver of an LNG-powered tractor pulls into the fueling station. He or she turns off the engine, gets out of the vehicle, lifts up on the fuel nozzle, and inserts it into the vehicle’s fuel tank. Before filling up the vehicle, the fuel nozzle vents excess tank pressure to the fueling station’s storage tank. Once this process is complete, a card is swiped and fueling commences—with the fuel pumped from the station’s storage tank located above ground, rather than underground.

An LNG-fueled tractor is built from the ground up to operate on LNG. The fuel tank is constructed much like a double-walled insulated bottle to ensure that the fuel remains super cold. Typical tank capacities are 80, 100, or 120-gallons, which are comparable to a 50 to 75-gallon diesel tank and capable of traveling about 350 miles between fill-ups. As with a diesel tractor, the ability to add a second LNG fuel tank exists, and that effectively extends the range of an LNG tractor to more than 600 miles.

When the engine in an LNG tractor starts up, the LNG fuel is pumped from the tank to a vaporizer at 2,200 psi (pounds per square inch). Utilizing heat from the engine, the LNG becomes a pressurized vapor. It is then sent to an accumulator tank and a fuel condition module, which ensures that the engine receives a consistent flow of vaporized fuel. From there, the fuel enters a combustion chamber, where it is mixed with a small amount of diesel (the ratio of natural gas to diesel is 19:1) and air. While in the combustion chamber, the pressure and heat ignite the diesel, which in turn, ignites the natural gas and provides power to the vehicle. This is where the major differences between a conventional diesel tractor and an LNG-powered tractor end.

It shouldn’t be surprising that the cost of an LNG tractor is somewhat more than a diesel tractor. After all, demand for LNG tractors is still relatively low, they utilize new technologies, and they are designed to handle a super-cold fuel. Although an LNG tractor is more costly than a conventional diesel tractor, fuel cost savings is significant and the pay-back period can be relatively short. Other advantages of an LNG tractor include a 30-40 percent reduction in NOx and CO2 emissions, with no particulates or soot produced. Fewer emissions mean a cleaner atmosphere, less smog, fewer smells, and an engine that requires less maintenance. Rides are smoother and quieter, too.

So the next time you’re driving behind a semi truck, and you see and smell fresh air and no exhaust… and the driver looks happier, healthier, and wealthier, you’ll know why. The vehicle’s probably being powered by LNG.