Natural gas, already proven as a fuel to power generator sets, buses, stationary engines, homes and factories, is finding new use as a transportation fuel.
Environment is usually touted as the main reason for switching to the clean fuel, but lower prices and the daily waste of excess natural gas also figure into the equation.
As an example of how much natural gas disappears into the atmosphere, more than 35 percent of natural gas production from North Dakota’s Bakken oil patch is burned off as waste because oil companies cannot handle the high volume, says the U.S. Energy Information Administration.
It’s estimated that 100 million cubic feet of natural gas are lost each day. Using a hypothetical depressed wellhead price of only $3 per 1,000 cubic feet, that volume of wasted natural gas in North Dakota has an annual value of $110 million in lost revenue.
Because of the abundance, experts believe natural gas will never experience the artificial shortages and dramatic price fluctuations often experienced with gasoline and diesel. Investment in natural gas as a main fuel source for transportation is viewed as a safe bet over the long term.
Some proponents of natural gas as a transportation fuel concentrate on compressed natural gas. The drawback is that CNG requires high-pressure fuel tanks and compressors capable of squeezing the gas into tanks at 3,500 pounds per square inch.
Other companies focus on liquid natural gas (LNG) because it doesn’t require high-pressure tanks or compressors. LNG is super cooled to -160 C and stored in insulated, non-pressurized tanks. The cooling process reduces the volume to 1/600th of its vapour state once it is in a liquid state, according to a Cummins news release.
Cummins said LNG provides better energy density in diesel equivalent, which reduces the actual volume of fuel required for long distance travel.
It takes 127 litres of LNG to travel 160 kilometres in a tractor-trailer rig. It takes 264 litres of CNG to go the same distance. Cummins recently announced plans to produce dual-fuel engines for mine-haul trucks. Dual fuel technology substitutes LNG for diesel, thus reducing the amount of diesel fuel required.
“To convert a diesel engine to a dual fuel engine, Cummins adds a gas fuel system, additional sensors and controls and a diesel oxidation catalyst,” said Cummins spokesperson Sarah Sullivan in an email interview.
The first engine in the dual fuel lineup is the QSK60, which was introduced 12 years ago. Output ranges from 1,782 to 2,850 horsepower. Other QSK Series engines will follow in the dual fuel conversion, all of which will meet Tier 4 Final standards.
The engines depend on integrated controls to optimize the LNG substitution rate, depending on operating conditions.
The transition between the two fuels is automatic and seamless. The engines can run 100 percent diesel or a blend up to 70 percent LNG.
“The rapid expansion and abundance of natural gas in many areas of the world has driven a dramatic cost advantage of natural gas over diesel, said Mark Levett of Cummins’ high horsepower division.
“The ability to substitute diesel with natural gas drives down the total cost of ownership of equipment.”
He said the new technology provides operators of high-horsepower mining equipment an opportunity to dramatically reduce fuel costs.
Power density is critical in this industry and large amounts of fuel are burned.