The battery-powered hybrid technology used throughout the automotive industry is making its way into the off-highway marketplace. Volvo Construction Equipment demonstrated a prototype of its L220F hybrid wheel loader at ConExpo, saying the vehicle can save fuel and extend engine lifetimes.
The wheel loader augments its D12 engine with an integrated starter generator (ISG), which sits between the engine and the transmission, charging when the engine is at rest and powering the transmission during startup. It is coupled to a lithium battery pack that has “significantly more” capacity than lead acid batteries. The battery pack provides power at levels when diesels falter. Electric motors provide a torque boost to augment the low torque of diesel engines operating at low engine speeds.
“The torque of electric motors is high from the beginning. When you’re looking at startup or takeoff, the boost from the electric motors let the diesel operate at lower revs so there’s much less stress on the engine,” said Arvid Rinaldo, called the father of the hybrid system by Volvo CEO Tony Helsham.
In addition to reducing wear and tear on diesel engines, running the diesel at lower speeds will reduce noise, which is important in many urban areas. Reducing engine speed will save fuel, as will a reduction in idling hours. The batteries also power the climate control system so engines do not have to idle to keep operators comfortable.
“Wheel loaders spend up to 40% of their time idling,” said Rinaldo. “Now operators can shut down the diesel and run air conditioning and radios for up to an hour. As soon as the operator hits the throttle, they’ll have 67 hp within 1 s.”
During the prototype testing phase that will continue for around a year, Volvo will be studying and quantifying factors such as reduced emissions and fuel conservation.
“With our prototype, we’re promising at least a 10% improvement in fuel consumption,” said Rinaldo, who would not say how much the hybrid system would add to vehicle costs.
Instead, Helsham noted that “the payback time will be about two years.” He noted that engineers in the construction group are leveraging development work done by Volvo cars.
Rinaldo added that continuing technical advances should boost fuel savings. The prototype now being tested charges its batteries when the diesel is not working, but production versions set to ship late next year will use regenerative braking. Capturing energy during braking is common in most automotive hybrids.