Düsseldorf (Germany), 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.
This is shown by the results of comprehensive tests carried out with a diesel-electric
Model 6 crane, completed by Gottwald, the only manufacturer of Mobile Harbour Cranes
with electric drive technology. The result is that Gottwald is able to improve the efficiency
of Mobile Harbour Cranes which cannot be hooked up to an external power supply due to
the quay infrastructure, which empowers terminal operators to sustainably reduce fuel
consumption, fuel costs and exhaust gas emissions. By the same token, Gottwald makes
it possible for terminal operators to position themselves in a strong position when it comes
to negotiating terminal concessions.
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.
About Gottwald Port Technology GmbH
Gottwald Port Technology GmbH, based in Du¨sseldorf, Germany and a subsidiary of
Demag Cranes AG, is a manufacturer of Harbour Cranes and terminal automation
technology. With a total of over 1,300 Mobile Harbour Cranes sold, the company is world
market leader in this product sector. In the field of terminal automation, Gottwald Port
Technology offers system solutions that incorporate both the company's own software and
hardware. Gottwald Port Technology supplies customers in around 100 countries.