Bauer, P., Dillon-Gibbons, C., Iyer, N., Kilner, A.A., Eassom, A., Gumley, J., Thurumella, H., Paper Number OTC-32194-MS, Proceedings of Offshore Technology Conference, May 1st-4th, Houston, Texas, USA, 2023.

Abstract

Wave Energy Converters (WEC) are devices that convert the kinetic energy of the waves into useful electrical energy. There are multiple types of WEC devices that have been developed over the years. These devices act as a source of clean energy and can be used to generate electricity. This paper provides a numerical assessment of a WEC device comprising of a moored buoy with a Power Take-Off (PTO) system driven by line tension. This WEC system was developed by Laminar Scientific. AMOG was contracted by Testing and Expertise for Marine Energy (TEAMER) to provide a numerical assessment of this WEC device under metocean conditions present at the PacWave site. 

The WEC system was modeled using the hydrodynamic package OrcaFlex, over a range of regular and irregular sea-states of varying wave height and period. Four optimization steps were made to the model, altering parameters of the original model such as size and geometry. 

The simulations indicated that the WEC device power output is highest for large surge and heave motions of the buoy. The simulations also predicted that increasing the surge and heave motions lead to a critical point beyond which the PTO system was no longer able to respond rapidly enough to maintain minimum tension in the mooring lines. Beyond this point snatch loads were predicted to occur potentially exceeding the Minimum Breaking Load (MBL) of the lines and accompanied by unstable rotational motions of the buoy. Increasing the size of the buoy was predicted to prevent these snatch loads and associated unstable rotational motions of the buoy from occurring in the range of sea states investigated. The parameters which were predicted to have the most impact on the system performance were the buoy size (mass, moments of inertia, and volume) and the rotational inertia of the PTO system. Increasing the buoy size and decreasing the PTO rotational inertia was predicted to improve the power generation capabilities of the device.

Copyright 2023, Offshore Technology Conference DOI 10.4043/32194-MS