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Model 6 Mobile Harbour Crane handling containers. A crane of this type was used by Gottwald for successful tests with its new hybrid drive. |
Düsseldorf, 23 March 2010 – With its new hybrid drive, Gottwald Port Technology GmbH, a subsidiary of Demag Cranes AG, demonstrates that improved energy efficiency contributes to both the economical and environmentally compatible operation of Mobile Harbour Cranes. This technology uses state-of-the-art diesel generators in connection with dynamic brake resistors and short-term energy storage to achieve fuel savings in the double-digit percentage range.
Diesel-Electric Mobile Harbour Cranes
It has been possible for some time now, if a machine uses electric drive
technology, to return the energy recovered from the machine's deceleration motions to the crane's
internal power system. If, however, no consumers in the system currently require that energy, this
excess energy is dissipated in brake resistors, i.e. converted to heat. Where, in the past, these
resistors could only be switched in in relatively large steps, today it is possible to make use of
dynamic brake resistors to improve the machine's energy rating considerably.
In response to demands for further improvements in efficiency, Gottwald has developed a hybrid drive which includes short-term energy storage for the recovered energy which is then made available to the crane's power system for the next work cycle. The conventional brake resistors only come into play if the capacity of the energy storage system is exceeded.
Choice of a Suitable Short-Term Storage System
Mobile Harbour Cranes work with rapid load changes combined with discontinuous hoisting,
lowering and slewing actions including the associated acceleration and deceleration actions. This
is why storage systems that can store and return energy quickly and allow high cycle rates in rough
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 capacitors (ultracaps) with typical charge
and discharge times of max. 30 s in this kind of operation and with a service life of 1 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.
Pilot Project Confirms Sustainability Approach
The G HMK 6407 Mobile Harbour Crane, a variant of Model 6, is used in a maritime terminal for
handling empty and full containers and fruit pallets for approx. 4,000 hours per year. This
handling machine has a maximum lifting capacity of 100 t, hoisting speeds of up to 90 m/min and an
installed diesel engine power of 895 kW. 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 in the double-digit percentage range can be achieved. At the same
time, the quieter running characteristics of the diesel engine resulted in reduced noise
emissions.
Taking More Advantage of Potential Green Technologies
As well as fitting new cranes with the technology, Gottwald will be offering existing owners
of their Mobile Harbour Cranes upgrades to environmentally friendly, cost cutting dynamic brake
resistors and hybrid drives. The new drive technology is of particular interest to operators of
Mobile Harbour Cranes with comparable workloads and cargo handling profiles as the prototype and
for harbour crane applications such as intensive container handling and professional bulk handling,
where they are configured as 4-rope grab machines, equipped with two hoists and frequently work
6,000 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 economical
and ecological savings.
Green Drive Technology by Gottwald
Under its "Gottwald Green Range" label, the company is developing green technologies with a
view to making the sustainable management of maritime and intermodal terminals a reality. In
mid-2009, Gottwald launched the first battery-driven Automated Guided Vehicle (AGV) and has now
completed successful testing. With its new hybrid drives, Gottwald has taken a further step towards
improving the electric drive system used on Mobile Harbour Cranes – electricity being the most
energy-efficient source and, as a result, the one most commonly found in terminals.
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