Mecalac, the French side of the Franco-German Mecalac Ahlmann Group, debuted a prototype diesel-electric hybrid multifunction wheeled excavator at Intermat that is expected to offer reduced fuel consumption, CO2 emissions, and noise levels.
Based on an existing 9-t (9.9 ton) 12MTX machine, the hybrid claims the same amount of power as the standard 74 kW (101 hp) model but uses a 51-kW (68-hp) diesel and a 15/30-kW electric generator located where the pump coupling flange is normally located.
The thought process behind the system is straightforward: the diesel alone rarely operates at full power; rather, Mecalac’s studies show that the average power use is around 51 kW. Mecalac Ahlmann spends almost 6% of its revenue on R&D.
The hybrid system, with a smaller diesel, generator/electric motor, and 400-V lithium-ion battery, keeps the diesel running at an optimum level and provides additional power when more than 51 kW is required. In cases where less than 51 kW is needed, the batteries are charged. Energy recovery is also possible during braking periods.
Control of these interacting systems is imperative for success, and to maximize efficiency, electronics manage the diesel, additional power from the electric motor, current into the battery, and start and stop features. As the hybrid system works automatically, there will be no additional work for the operator and no change in the controls.
A reduction in sound levels, both for the driver and for the exterior working environment, is due to the reduced size of the diesel and the stop/start function that switches off the motor when no movement is needed. With this function, the generator becomes the starter motor, eliminating the standard starter and alternator, and also cutting emissions, noise, and consumption until movement is needed.
The hybrid claims a 25% fuel savings over the standard 12MTX, due to the stop/start function and the smaller diesel engine. Increased productivity is also possible due to the instant torque from the electric motor; the torque from the combined diesel-electric system is greater than that of the standard 12MTX 74 kW diesel.
The 12MTX hybrid is an excavator and a loader, with an articulated frame. The articulation gives a tight turning circle, with an outside diameter of 4.9 m (16 ft). The hybrid can manage a top speed of 27 km/h (17 mph), the same as the standard 12MTX. It is likely that the concept will become a reality, although it could be more than two years before production begins.