A state-of-the-art review of submerged wave energy converters

Current wave energy converter (WEC) design focuses primarily on surface-piercing concepts due to the higher energy density, enabling more energy absorption, but faces challenges in extreme wave conditions. Submerging WECs during extreme events can improve survival by reducing wave excitation, though it may also decrease power performance due to the lower energy density. WECs designed specifically for subsurface conditions offer a potential solution to these challenges by being designed to operate at depths that reduce extreme wave loading and limit conflicts with other ocean users. To date, no work reviews the state-of-the-art submerged WEC concepts regarding categorizing archetypes, identifying their capabilities and constraints, and synthesizing research gaps. The lack of aggregated information hinders understanding the benefits, limitations, and common challenges across concepts with similar subsurface operating functions. This paper seeks to fill this gap by reviewing the state-of-the-art submerged WECs and identifying designs from early-stage to demonstration concepts to categorize what archetypes exist. This literature review shows six different submerged WEC archetypes: point absorber, oscillating surge, oscillating water column, bulge wave, pressure differential, and flexible membrane. These findings provide a general overview of the field’s development status and a detailed overview of each archetype — covering the operating principles and the status of research. We then identify research gaps and outline topics that need further investigation to improve our understanding of submerged WECs. This information will help guide future development in subsurface WEC technology, underscoring its potential benefits for sustainable energy and offering valuable insights for researchers, designers, and communities.