Company engineers meanwhile are exploring the possibility of using dimethyl ether, or DME, in North America. Stored and handled like propane, DME is produced from natural gas or biomass such as wood byproducts, and can be burned in diesels with few changes.
The upcoming 13-liter natural gas engine will be a dual-fuel design, using liquefied natural gas as the main fuel with "trace amounts" of diesel for pilot ignition. This is 30% more efficient than spark ignition and will add range to the truck it powers, which is important for over-the-road operations, said Olof Persson, CEO of Volvo Group, who announced the engine at an environmentally oriented meeting in Miami.
The meeting coincided with festivities for the Volvo Ocean Race, a nine-month round-the-world sailboat competition that the company sponsors in part to highlight its environmental concerns. Boats tied up last week in Miami, the only American port on the itinerary.
The dual-fuel heavy-duty engine "will respond to a national interest in natural gas in the U.S.," Persson said. "It is not a renewable source of energy, but it is available and clean-burning." Vast reserves and extensive drilling and production in the U.S. have driven down natural gas prices to about half that of diesel fuel.
With this engine, Volvo plans to use liquefied natural gas (LNG), more of which can be stored aboard a truck than compressed natural gas (CNG). LNG is shaping up as the preferred alternative fuel for OTR tractors, he noted.
The current 8.9-liter Cummins ISL-G in Volvo and Mack trucks will continue to use CNG, Persson said, as will the 11.9-liter ISX-G, due out early next year. Trucks with these engines tend to run local and regional routes and return home frequently for refueling, and can effectively use the less dense compressed fuel whose tanks consume more space on a chassis.
The Cummins heavy-duty engines need only a three-way catalyst to meet EPA 2010 emissions standards, executives noted. There is no diesel particulate filter or urea injection aftertreatment equipment.
The dual-fuel 13-liter engine will need a DPF and urea injection, though the parts might be smaller and lighter because of the small amounts of diesel fuel that it will use. Test engines in Europe have reliably covered thousands of miles, and "customers are very satisfied with it," Persson said.
The dual-fuel engine will be offered in Volvo truck and tractor models, and there'll also be a Mack version, said Denny Slagle, executive vice president, Volvo Group. Volvo Trucks North America and Mack Trucks are owned by Volvo Group in Gothenburg, Sweden, where Persson is based.
Regarding dimethyl ether, Volvo Group has conducted hundreds of thousands of miles of customer field testing of DME-powered trucks in Europe, said Ron Huibers, sales and marketing president for Volvo Trucks North America.
Strong results from 10 vehicles operating in a variety of applications indicate DME holds much promise as a heavy-truck fuel, and could become a viable alternative to CNG or LNG based on performance, environmental impact, safety and distribution.
DME mirrors the exceptional performance qualities and high energy content of diesel while significantly reducing greenhouse gas emissions, he said. It is an excellent compression ignition fuel which, like diesel, uses a common-rail fuel system and requires no spark ignition mechanism.
DME does not require cryogenic temperatures, like LNG, or high storage pressures, like CNG's 3,600 psi. DME is handled like propane, with tank pressures of 75 psi, and it is non-toxic. DME burns with a blue flame and requires no diesel particulate filter and might not need urea injection.
DME packages densely enough to allow long range operations or to allow room for vocational truck equipment on the frame, Huibers said. The infrastructure to supply DME to trucks will develop with the market.
Little DME is now being made in the U.S., but Volvo is aware of a new DME plant under construction in Imperial County, Calif., and believes more will follow, he added.
"Our strategy is not to put all our eggs in one basket," said Persson in explaining Volvo's Blue Power program, which might include DME as well as the two forms of natural gas.