Overview of advancements in overtopping breakwater for wave energy conversion (OBREC): Harnessing coastal power for renewable energy and enhanced coastal protection

Coastal engineering is increasingly moving toward multifunctional systems that integrate shoreline protection with renewable energy generation. Among these innovations, the Overtopping Breakwater for Wave Energy Conversion (OBREC) stands out as a promising technology that converts wave energy into electricity while enhancing coastal resilience. This paper presents a systematic review of OBREC research conducted between 2014 and 2024, synthesizing global developments across experimental, numerical, and prototype studies. The analysis identifies distinct national approaches, including Italy's full-scale implementation, Malaysia's CFD-based ramp optimization, China's multi-level MOBREC configuration, and Thailand and South Korea's hydraulic sensitivity investigations. Each contributes valuable methodological insights into OBREC performance and design evolution. Comparative assessment reveals persistent research gaps, particularly regarding turbine integration and the adaptation of low- and very-low-head technologies to OBREC's intermittent flow regime. The review also examines power prediction models, capacity factors, and economic indicators, highlighting inconsistencies in performance assessment. By integrating findings on hydrodynamics, turbine technology, and environmental implications, this study provides a comprehensive foundation for advancing OBREC toward practical, efficient, and sustainable coastal energy applications.