Dual wave farms for energy production and coastal protection

The synergetic application of wave farms, i.e., arrays of wave energy converters (WECs), for protecting the coast in addition to their main objective of generating carbon-free energy can place this renewable resource as a major element in ocean and coastal management. In particular, their ability to mitigate coastal erosion by reducing the amount of wave power reaching the coast will be put to use - and this is the motivation for this work. We propose a new approach in which the wave farm has a dual purpose: to generate carbon-free energy and to contribute to coastal erosion management. We illustrate this approach by means of a case study: a dual-purpose wave farm off Xago, a beach-dune system in Asturias (N Spain) subject to severe erosion - manifested dramatically in the retreat of the dune - and located in the area earmarked for the first wave farm in Spain. The objective of this work is to establish whether or not the wave farm may be useful to counter the erosion of the beach-dune system. To this end a wave propagation model is coupled with a state-of-the-art coastal processes model and applied to analyse the response of the system under storm conditions in two scenarios: with and without the farm. The efficiency of the wave farm in mitigating erosion is determined by comparing the results in both scenarios by means of a series of coastal indicators defined ad hoc. We find that the farm reduces storm-induced erosion particularly where it is most acute, in the dune front, and thus contributes to alleviate the current erosive trends. This opens up exciting possibilities of using dual wave farms in lieu of, or as a complement to, coastal structures or beach nourishment. As wave energy develops into a major renewable energy source in the coming decades, dual wave farms are poised to constitute a breakthrough in coastal erosion management.