Pull and Lock Marine (PALM)
Apollo Offshore Engineering Ltd
Mocean Energy Ltd, Carnegie Clean Energy, Bombora Wave Power, The European Marine Energy Centre Ltd, MacArtney UK Ltd, Seacroft Marine Consultants Ltd
Apollo developed the Pull and Lock Marine (PALM) connector in Stage 1 of the development
process and were successful in progressing to Stage 2.
The PALM achieves a robust, close fit mechanical and electrical connection in a single pulling action from a tug's winch. It comprises an upper ‘receptacle’ attached to the WEC, and a lower ‘plug’ element on top of a mooring system. During connection, the tug pulls the plug through a series of guides inside the receptacle via a pre-reeved fairlead. These orientate and direct the plug into its locked position, while electrical connection is achieved through wet-mate stabs. Disconnection is similarly achieved by a single winch wire pull.
Hinged joints release the required degrees of freedom for operations and the system is designed to be rugged for harsh environments. The central innovation is the passive mechanical operation of effecting the connection or disconnection. No hydraulic or servo actuators are required. The reliance only on tug action and proven mechanical components draws on learning from other sectors. It is anticipated that the system may also be applicable in floating wind and tidal stream devices.
Stage 2 activities include:
- Development of the PALM for specific WEC designs, including design modelling, drawings and engineering calculations.
- Working with manufacturers to specify electrical connectors and slip rings.
- Survival analyses of moorings, mechanism and WEC interface.
- Analysis of operational methods, seastate limits and potential workability.
- Investigation into materials, coatings, and cathodic protection.
- Component-level FMECA.
- Detailed operational plans, including storyboards and HIRA.
- A development strategy and cost model for future commercialization.
- A plan for the stage 3 including the physical testing of a prototype.
The analysis considered two test case implementations of the PALM on actual wave energy converter (WEC) designs. These were:
- Mocean’s Blue X device, which includes a combined mechanical and electrical connection mounted underneath the WEC.
- Carnegie’s CETO 6 device, with a mechanical seabed-mounted connection that experiences much higher mechanical loads but does not include an electrical connection.