The hybrid drive combines state-of-the-art generators in connection with dynamic brake resistors and short-term energy storage to achieve fuel savings in the double-digit percentage range, Gottwald said.
The short-term energy storage for recovered energy is made available to the crane’s power system for the next work cycle.
Energy recovery is an established technology, Gottwald said, but if there is no consumer in the system for the recovered energy, it is dissipated to brake resistors and converted to heat, with the resistors only able to be switched in in relatively large steps. Conventional brake resistors only activate if the capacity of the energy storage system is exceeded.
The use of modern day dynamic brake resistors improves a machine’s energy rating considerably, Gottwald said. The Gottwald hybrid drive system uses an electrostatic short-term energy storage system utilising wear- and friction-free double-layer capacitors with typical charge and discharge times of a maximum 30s and a service life of one million cycles. This system stores energy as electricity and does not convert it at all for a higher degree of efficiency.
The hybrid drive system has been piloted on a G HMK 6407 mobile harbour crane, in operation in a maritime terminal handling loaded and unloaded containers and fruit pallets for around 4,000 hours per year. The mobile harbour crane has a lifting capacity of 100t, hoisting speeds up to 90m/min and an installed diesel engine power of 895kW.
Testing of the hybrid drive system showed that fuel savings in the double-digit percentage range can be achieved, as well as reduced noise emissions from the diesel engine.
Gottwald said 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 the cranes are configured as 4-rope grab machines, equipped with two hoists and frequently work 6,000 hours per year.
Gottwald said it will be offering this technology on all new cranes, as well as an upgrade to existing owners of mobile harbour cranes. Gottwald is also aiming to downsize its on-board diesel engines using this drive technology for further economical and ecological savings.