Mobile harbour cranes benefit from hybrid drive innovation

This significant improvement in energy efficiency contributes to both the economical and environmentally compatible operation of mobile harbour cranes.

Gottwald has developed a hybrid drive which includes short-term storage for recovered energy, derived for example from the crane’s deceleration motions, which is then made available to the machine’s power system for the next work cycle. Conventional brake resistors only come into play if the capacity of the energy storage system is exceeded. The company points out that mobile harbour cranes work with rapid load changes combined with discontinuous hoisting, lowering and slewing actions including the associated acceleration and deceleration movements.

This is why storage systems that can both retain and return energy quickly and allow high cycle rates in rugged day-to-day crane operation are necessary. In this context, Gottwald has performed tests on mechanical, electrochemical and electrostatic short-term storage systems.

The key requirements are met by electrostatic wear and friction-free double-layer capacitators (ultracaps) with typical charge and discharge times of 30 seconds maximum in this kind of operation and with a service life of one million cycles. An outstanding advantage of this system is that the energy is stored as electricity and is not converted at all, which provides a high degree of efficiency.

As part of the pilot project Gottwald chose a G HMK 6407 mobile harbour crane, a variant of the Model 6, which was used in a maritime terminal for handling empty and full containers and fruit pallets for approximately 4000 hours per year. This crane has a maximum lifting capacity of 100t, hoisting speeds up to 90m/min and an installed diesel engine power of 895kW.

During the test phase, which immediately followed the upgrade of the crane to dynamic brake resistors and the installation of the new ultracaps, it was demonstrated that fuel savings well in excess of 10% can be achieved. At the same time, the quieter running characteristics of the diesel engine resulted in reduced noise emissions.

As well as fitting new cranes with this technology, Gottwald will be offering existing owners of its mobile harbour cranes upgrades to environmentally friendly, cost-cutting dynamic brake resistors and hybrid drives.

These are equally applicable to mobile harbour cranes for bulk handling applications. Here they are configured as four-rope grab machines equipped with two hoists and often working 6000 hours a year.

In addition Gottwald intends in the medium term to take advantage of the latest drive technology to downsize its on-board diesel engines to achieve even higher economic and ecological savings.