Gearboxes for wind-harvesting kite ships

Startup OCEANERGY’s new green hydrogen energy ships were inspired by kitesurfing — a sport practised by OCEANERGY CEO Dr Wolfram Reiners.

“The basic idea was to harness the forces acting on the kite that pull the kite’s ropes and convert them into electricity,” he said. At the heart of the Kite Hydrogen Ship concept is the patented K1 Kite Propulsion system, which can be imagined as a green power socket for the onboard electrolysis process.

To support production of its wind-powered hydrogen, OCEANERGY opted to use WITTENSTEIN alpha’s robust TPK+ gearboxes with their intelligent cynapse functionality, which includes integrated sensors, logic and an IO-Link data interface in the gearboxes.

“These smart gearboxes will supply essential operating and status data, while the energy ships that produce green hydrogen in the six permanent oceanic trade wind zones will be smartly navigated there according to the wind forecast,” explained Ulrich Dobler of the Stuttgart-based startup’s executive board.

Hypoid right-angle gearboxes from WITTENSTEIN alpha’s TPK+ series are used to control the kite’s four ropes, which can be up to 1200 m long. (L–R) Ulrich Dobler (OCEANERGY CEO) with Andreas Kolibius (Sales Engineer for WITTENSTEIN alpha). Image credit: WITTENSTEIN SE.

The challenge for the smart hypoid gearboxes is to control the kite’s four frequency converter-driven ropes as they generate electricity during the harvesting journey by launching and pumping the kites. Dynamic wind loads can reach up to four tons per rope. A large part of the energy that is generated in this way by the K1 Kite Propulsion system is utilised directly on board for the production of green hydrogen.

“A hydrogen plant of this kind is designed to produce around 1000 tons of green hydrogen during its eight-week harvesting journey,” Dobler said. “That adds up to a good 6000 tons per year — enough to supply about 40,000 hydrogen cars or power an Airbus for almost 12 months.” The aim of the energy ship fleet now in the pipeline is to produce green hydrogen costing just 2 euros per kilo by 2035; a significantly lower cost than with any other green technology known to date, according to the company.

The gearboxes’ right-angle design is central to the ultraspace-saving principle of the entire K1 Kite Propulsion system and its integration into a seaworthy container. These size 300, two-stage gearboxes have a ratio of i=100 and are characterised by high torsional rigidity, low torsional backlash and greater absorption of external forces. The hypoid teeth simultaneously provide high torque and smooth running.

Cynapse functionality enables gearbox monitoring online on the high seas

When a Kite Hydrogen Ship sets off semi-autonomously on a harvesting journey, the kites — and hence the propulsion system’s main axis — will be subjected to extremely diverse movements and forces. This was what led OCEANERGY to deploy the TPK+ with cynapse functionality. “Transmission functions and operating data like acceleration values can be monitored and analysed remotely in this way on the high seas,” said Felix Bartels, Senior Mechanical Engineer.

OCEANERGY also uses WITTENSTEIN alpha gearboxes for other propulsion tasks on board its Kite Hydrogen Ships. For instance, the manual control unit of the K1 Kite Propulsion system features a low-backlash TP+ planetary gearbox from the alpha Advanced Line; a compact, torque-dense NVH worm gearbox from the V-Drive Value family; and two TPM+ rotary servo actuators.

Additionally, the slewing ring utilises a torque-dense and torsionally rigid XP+ planetary gearbox with special output geometry as the basis for its ultracompact design.

For more information about the Kite Hydrogen Ships, visit www.oceanergy.com.

Top image caption: Searching for a sustainable path to green hydrogen production, OCEANERGY developed the ‘Kite Hydrogen Ship’ technology, which allows green H₂ to be produced directly on board by harvesting wind energy and electrolysing sea water.