Long-term impacts and design considerations of dual-purpose wave farms for energy generation and coastal protection

The dual use of wave farms for renewable energy generation and coastal protection presents a promising strategy to reduce the Levelized Cost of Electricity (LCoE) and improve the economic feasibility of wave energy. However, no prior study has quantified the long-term morphodynamic impacts of wave farms or evaluated how seasonal wave conditions influence energy output and coastal protection effectiveness. This study presents the first integrated assessment of a nearshore WaveRoller Wave Energy Converter (WEC) array over 1-, 10-, and 20-year periods, using a field-validated, coupled depth-averaged (2DH) hydrodynamic, spectral wave, and sediment transport model in Delft3D. Nine deployment configurations were simulated to explore how array layout (spacing and distance from shore) affects wave attenuation, sediment retention, and energy output. Results show that the WaveRoller array produced 562.3 MWh annually per device, with a capacity factor of 18.34 % and a capture efficiency of 49.9 %. The system also retained up to 278,427 m 3 of sediment after 20 years, with a sediment retention per unit area of 1.941 m 3 /m 2 . Wave attenuation was greatest during low-to-moderate energy conditions, suggesting year-round protection benefits. Sensitivity analyses revealed a trade-off between energy yield and erosion mitigation, with tighter spacing enhancing sediment retention and moderate distances offshore improving energy yield. By quantifying energy production and erosion mitigation under different design scenarios, this study demonstrates the dual functionality of wave farms and supports their use as multi-functional coastal infrastructure. These results offer a foundation for future techno-economic models that incorporate both energy and coastal protection outcomes. • First long-term study of dual-use wave farms for energy and coastal protection. • Wave farm retained 278,427 m 3 of sediment over 20 years, reducing erosion by 42 %. • Annual output of 562.3 MWh per device with 49.9 % capture efficiency. • Wave attenuation peaked during low-energy conditions, offering year-round protection. • Tighter spacing enhances protection; greater distance offshore increases energy output.