Building the perfect green truck all starts with the application. Pickup and delivery brings multiple stops, varying payloads, relatively low mileages, and urban or non-highway routes. The typical vehicle is a medium-duty truck with a van body and a diesel engine. It's usually driven by someone whose primary responsibility is servicing customers on the route, and who considers truck driving secondary.
That type of duty cycle is custom-made for a diesel electric hybrid, especially one using parallel hybrid technology. Basically, an electric motor/generator armature is placed on the flywheel or somewhere else in the drivetrain. When the vehicle brakes are applied, the armature acts as an electric brake, generating electric current as it slows the vehicle, which is then stored in batteries. Starting the vehicle from a complete stop, the current is drawn from the batteries, turning the armature into an electric motor to launch the truck. Once underway, the diesel engine takes over.
Frequent stops in a P&D application mean there are many opportunities to capture braking energy. Since overcoming inertia to start from a stop requires more energy than keeping the truck moving once it's underway, using the “free” electric energy created and stored in the hybrid's batteries can cut fuel consumption up to 30% when a truck has to stop and start frequently making its deliveries and pickups.
Weight conditions in P&D are also optimal for hybrids. Usually a Class 6 or 7 vehicle, a P&D truck spends little time at gross weight limits since by definition its load is constantly fluctuating as the driver drops off freight or makes pickups. With the electric motor function of the hybrid system providing the power spike needed to launch the vehicle, hybrids can also downsize to 6- or 7-liter diesels, further contributing to fuel economy.
And for P&D fleets looking to push the envelope, the hybrid's fuel economy can be complemented by a variety of other systems well suited to that application. For example, automated mechanical or automatic transmissions often help fuel economy in P&D since the drivers are less likely to be experienced truck drivers who know how to shift for maximum fuel economy. Automating that part of the driver's responsibility brings consistent low-rpm shifts that can mimic a skilled driver's performance and fuel savings.
Navigation systems for those not following regular routes can lower out-of-route miles, further improving fuel economy. Onboard tire inflation systems can keep tire pressures at optimum levels in trucks that might not be working out of terminals with dedicated maintenance personnel.
In the end, consuming less fuel means lower emissions of greenhouse gases, making the diesel electric hybrid with such complementary add-ons the most logical “green truck” for P&D.
