Backward bent-duct buoy or frontward bent-duct buoy? Review, assessment and optimisation

This work focuses on the investigation of bent-duct buoy oscillating-water-column (OWC) wave energy converters (WEC), which have been generally studied in their backward configuration (BBDB). This work studies both backward and frontward configurations through systematic phases starting from a reference model of a BBDB OWC WEC. Firstly, an appropriate numerical model is defined to assess the performance of BBDBs equipped with linear turbines. Secondly, having variations from the reference model, a parametric sensitivity analysis is carried out to study the influence of the main geometric variables, when designing a bent-duct buoy in both backward and frontward configurations. Results show a better performance of frontward configurations in most cases. Afterwards, an optimisation study is performed for a specific site. Results confirmed that the frontward configuration for the optimised geometry outperformed the backward configuration, and the selected geometry also performs better than the original reference at the site selected. Finally, a techno-economic assessment is carried out for the reference BBDB and for the optimised bent-duct buoy. Despite the substantial increase in annual mean power output, results confirm that the wave commercial projects are not economically feasible under current assumptions. This requires more efforts from developers and from regulators/policy makers to develop mechanisms to promote wave energy projects.