Experimental investigation of WEC array interactions

The Australian Maritime College (AMC) with partner Swinburne University of Technology, is addressing a critical knowledge gap in understanding the performance of ocean wave-energy devices in arrays when operating in relatively close proximity. This work is a critical part of a collaborative project supported by the Australian Renewable Energy Agency (ARENA) and wave energy companies BioPower Systems and Carnegie Wave Power.

The project involves a novel set of physical experiments to investigate array interactions of Wave Energy Convertors (WECs). The experimental set up is a first of kind following a full hydrodynamic and mathematical analysis of the interactions, described as ‘the Phenomenological Theory’.

The main premise underlying the design of these experiments is as follows:

1) The models should be as generic as possible to encompass a maximum type of WEC behaviours.

2) Under linear wave theory, the total wave field can be separated into its diffraction and multiple radiation subparts.

3) The typical radiation wave field induced by a WEC motion can be separated in two distinctive forms:

1. Monopole
2. Dipole

4) Using the method of superposition the radiated wave patterns and the diffraction pattern can be combined proportionally to produce the total wave field comparable to a real world WEC.

5) The experiments will produce a set of bench mark results to compare and validate a numerical tool which will ultimately be able to assist government agencies and WEC developers in designing WECs arrays.

The measurement systems include a set of load cells in each of the WEC devices resulting in the 6 components of the total force and moments and a state of the art stereo videogrammetry system to measure the wave field elevation.

The presentation will include the full hydrodynamic theory justifying the experimental approach, a description of the experiments and results, and examples of these results applied to the optimisation of Power Take Off (PTO) parameters of an array for maximising power production.