OEM Experiments With Hybrids, but Focuses Efforts on Alt-Fuels

WENDOVER, Utah — A Volvo Group-manufactured hybrid truck set two preliminary world speed records last month, but the company’s North American brand has no plans to use that technology in trucks, instead focusing its efforts on alternative fuels.

“Unfortunately, owing to the way we market in North America, we’re not selling hybrids in North America at this point in time,” said Ed Saxman, the company’s drivetrain product manager.

Saxman gave a presentation here about Volvo’s alternative drivetrain efforts after Mean Green, a heavily modified truck, set two speed records for heavy hybrid vehicles, subject to official confirmation.

Volvo said it has found that hybrid technology for heavy-duty engines works best in transit buses and trash collection, two vehicle types that require frequent braking, he said.

A hybrid transit bus “goes up to the stop quietly, with no loud fuss. Then it’s got a smooth take-off, and at around 30 kilometers per hour, diesel just cuts in and it drives,” Saxman said.

Volvo makes, among other vehicles, a hybrid version of the iconic red double-decker bus used in London, and the hybrids are part of the current fleet there, Saxman said.

The Swedish company’s approach to heavy-duty hybrid technology is a “parallel” hybrid, he said. The vehicle has a separate diesel and electric motor, and the operator can choose to use one, the other or both.

“It’s really good in refuse collection, inner-city delivery and city buses,” he said. Volvo produces these vehicles in markets outside of North America, but since it does not make buses, trash trucks or medium-duty trucks in North America, the technology is not available here.

A Volvo hybrid transit bus uses up to 37% less fuel than a similar all-diesel bus, Saxman said, while a trash truck uses 30% less fuel. Both vehicles emit less carbon dioxide and are quieter than their all-diesel counterparts, and can use an all-electric mode if needed.

Part of the fuel economy comes from reducing the size of the diesel engine, which is easy when the electric engine is available, he said. Hybrid buses have diesel engines as small as 5 liters.

But the 200-horsepower electric engine gives about 800 foot-pounds of torque as soon as the vehicle starts, allowing it to accelerate quickly and wait for the diesel engine to kick in, Saxman said.

“The electric engine can make torque from stall. The diesel can’t,” he said. This gives Mean Green an advantage over an all-diesel truck, especially in runs that require it to start from a stall.

Volvo’s lack of heavy-duty hybrids in the United States “doesn’t mean we don’t have the technology,” Saxman said. “We certainly have the technology.”

But over-the-road trucking does not provide enough braking to make hybrids viable, he said. Hybrids depend on regenerative braking to recharge the batteries, and over-the-road trucks brake relatively infrequently.

Instead, Volvo is focusing on alternative fuels, such as natural gas. The truck maker is planning to sell a natural gas truck in 2014 using a Cummins Inc.-Westport Power Inc. engine, and eventually produce its own natural gas engine to sell (3-26, p. 1).

Volvo has also developed, for demonstration purposes, trucks that run on biodiesel, synthetic diesel, di-methyl ether, methanol, ethanol, biogas, biogas with bio-diesel and hydrogen with biogas.

In all of those fuels, “the driving thing here wasn’t just an alternative fuel, but a CO2-neutral fuel,” Saxman said, explaining that all of those fuels do not cause the truck to emit carbon dioxide.

Volvo demonstrated those fuels in 2008 at an event in Washington, D.C., he said. Each has its own advantages and disadvantages, especially in terms of the costs of the fuels, how easily infrastructure could be developed for them and what it would take to redesign trucks around them.

In general, Volvo spends a great deal of time experimenting with drivetrain technology, Saxman said.

“Volvo’s been doing a lot with different powertrain philosophies. We haven’t limited ourselves just to one different thing,” he said. “We’ve had many different systems that have not made it past production.”