Quieter, cleaner trucks and buses will soon be rolling down our streets.
People usually do not associate the word "green" with diesel trucks, but big diesels are getting cleaner. All new heavy-duty diesel engines sold in the U.S. after 2007 must meet strict new Environmental Protection Agency (EPA) standards that filter almost all the black soot particles and much of the nitrogen oxides that cause acid rain. The next set of standards, set to go into effect in 2010, will reduce nitrogen oxides even further.
The dirty little secret of the cleaner diesel engines: they burn more fuel--a big problem for fleet operators facing a 44% rise in diesel fuel costs over the last year. Commercial vehicles--the main consumers of diesel fuel--can accumulate 75,000 miles in a year. With diesel at $4 a gallon in some states, filling the tank on a long-haul truck now costs around $1,000. Even a small decrease in fuel efficiency can make a big difference to truck operators' bottom lines.
More at Forbes
This is why heavy-duty truck manufacturers are now paying a lot of attention to diesel hybrids. Automakers have offered passenger cars and light trucks with hybrid systems for a decade, but it took new EPA standards and $100-a-barrel oil to create enough commercial demand for hybrid big rigs, garbage trucks and dump trucks.
Much of the hybrid technology developed for gasoline engines can work with a diesel engine. The appeal: A hybrid truck can deliver fuel savings of 5% to 60%, depending on how it is driven. For one type of hybrid technology, the EPA estimates the average urban delivery truck could save more than 1,000 gallons of diesel fuel per year.
Hybrid power systems work best in vehicles that stop and start all the time, which means that they are ideal for delivery trucks, garbage trucks and school and city busses. For a long-haul vehicle, the savings would be significantly less.
One way hybrids save energy is by using an electric motor, or even a pressurized hydraulic system, to boost the performance of the internal combustion engine when the vehicle is accelerating or under heavy load. The energy can be stored chemically (in a battery), electrically (in a capacitor) or mechanically (in a pressurized hydraulic system).
This makes it possible to use a less powerful and more efficient internal combustion engine in the vehicle. Hybrids can also recover energy that would otherwise be lost as heat during braking. This results in less wear and tear on the conventional friction brakes--something that matters if you are buying brakes for all the garbage trucks in New York or all the buses in Boston.
Hybrids also save energy by shutting down the fuel-powered motor when the vehicle is at a stop or just crawling at a low speed: No more idling engines. The electric motor or secondary propulsion system can power the vehicle forward for short distances and restart the main motor when the vehicle needs more power.
Another benefit is greater torque when launching from a full stop. Diesel engines designed to pull many tons are always a bit slow to accelerate, but we got a chance to experience firsthand the benefit of hybrid technology when we test-drove a hybrid dump truck that Mack Trucks, a member of the Volvo Group, will soon deliver to the U.S. Army's Aberdeen Proving Grounds.
The 66,000-pound truck starts silently and moves forward a few hundred feet before the noisy diesel motor rumbles to a start. When the truck stops, the engine powers off but the lights, steering and other electric systems continue to run without a flicker.
Put the hybrid truck back in gear and it shoots forward as the system activates the electric motor. So garbage trucks can move from trash can to trash can faster and with less noise. "The diesel engine shuts down completely when there is enough power stored to run all the systems," explains John Jerwick, an engineer at Mack's engine plant at Hagerstown. Md. Jerwick has been working on diesel-electric hybrid technology for four years in a joint project with the U.S. Air Force.
Today, a handful of hybrid trucks and buses are on the road, and most are test vehicles. Madison, Wis., put five diesel-electric city busses into service in September. Cleveland engine maker Eaton has been testing 220 hybrid engines with its customers for the last four years. One of its customers, UPS, has 50 hybrid short-haul delivery trucks in its fleet. FedEx has 75 and Coca-Cola is using hybrids for deliveries in places such as New York City, where traffic prevents them from traveling much faster than 30 mph.
Those numbers are about to rise sharply. Every leading truck manufacturer plans to ramp up hybrid production as soon as possible. Daimler, which owns Freightliner, plans to manufacture 1,500 hybrid trucks and produce a hybrid version of its Thomas-Built school bus, all using hybrid technology developed by Eaton. Eaton is now delivering medium-duty diesel-electric hybrid power systems to Kenworth Truck, Peterbilt Motor and International Truck as well. Once production capacity increases, Eaton estimates that hybrids will make up about 10% of all new commercial truck sales in the U.S.
Local governments as well as the military are subsidizing the initial development and testing of hybrid trucks. California, for example, is spending $200 million to reduce emissions from school bus fleets. Navistar International, the country's largest maker of school busses, says the Energy Policy Act of 2005 can provide federal tax credits of up to $12,000 per unit for diesel hybrid purchases.
That may not be quite enough to offset an initial 35% premium over conventional vehicles, but with diesel averaging $3.88 a gallon nationwide, fleet operators will be weighing their options: pay more up front at the dealer or pay more at the pump for years to come.