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Konecranes – world first with hybrid reachstacker

Konecranes – world first with hybrid reachstacker

The innovative 45-tonne capacity lift-truck features a hybrid diesel/electric driveline, electrified hydraulic lifting system and super capacitor based energy storage. The company claims that these will cut fuel consumption and emissions by at least 30% compared to the equivalent diesel powered vehicles, while offering improved performance, acceleration and response to driver’s commands.

“Propulsion and lifting are powered by dedicated electric motors, all of which can operate in regenerative modes using stored energy generated from braking and load lowering. This results in a substantial reduction in fuel consumption and environmental impact. Meanwhile, productivity is increased in terms of quicker response and higher acceleration,” says Anders Nilsson, technical director, Konecranes Lift Trucks.

He suggested that “potentially”, the diesel engine in the hybrid could be replaced by another source of electrical energy, as technology and price allow, such as fuel cells or energy storage that can be recharged via the power grid.

Conventional reachstacker drivelines are diesel/mechanical systems, consisting of a diesel engine, torque converter and transmission. The engine produces energy for propulsion but its flow is mechanical, requiring a complex mechanical gearbox. In contrast, in the hybrid the driveline is a serial configured diesel/electric system, consisting of a diesel engine, an electrical generator and an electrical traction motor.

The diesel engine runs at constant RPM for optimum fuel efficiency and powers the generator. Propulsion is provided by an electric motor that is an integral part of the drive axle. This motor also generates electrical energy when braking, minimising the need for mechanical braking thus saving energy.

A conventional diesel engine mechanically drives variable displacement piston pumps that provide the hydraulic energy for lifting and steering, with the energy generated in load lowering dissipated to the ambient and wasted.

In the hybrid the hydraulic pumps are electrically driven and electronically controlled for lifting and steering, the speed of these pumps can be controlled independently of the diesel engine speed.

More importantly, the return flow from the hydraulic cylinders is not converted into heat but fed back through the pumps that act as hydraulic motors, thus regenerating electrical energy. This is stored in a super capacitor system connected to the truck’s electrics for later use, including boosting the diesel-powered electrical generator at times of peak power demand.