A study by researchers from the Interdisciplinary Centre of Marine and Environmental Research (CIIMAR) and the Faculty of Engineering of the University of Porto (FEUP) analyzes the potential and feasibility of a wave energy converter park off the coast of Esposende, with the dual aim of producing electricity from renewable sources and promoting coastal protection by mitigating local sea waves.

The study “Assessment of electricity production and coastal protection of a nearshore 500 MW wave farm in the north-western Portuguese coast”, now published in Elsevier’s international scientific journal Applied Energy, was developed by researchers from CIIMAR’s Marine Energy and Hydraulic Structures group and aims to bring a new vision to wave energy farms by combining them with coastal protection needs.

The use of wave energy contributes to the “green” energy transition towards which we have been moving in recent decades. However, commercially viable exploitation of this abundant renewable energy resource implies large wave energy parks, which can generate conflicts with other activities associated with coastal areas. But this doesn’t always have to be the case. The study in question indicates that there doesn’t have to be competition between the introduction of wave energy solutions and the functioning of the coastal zone (such as tourism, fishing and/or conservation reserves), suggesting that energy harnessing can have complementary applications, such as mechanisms for coastal protection. Specifically, the study addresses an exploratory proposal for a multi-functional park of wave energy converters (CEOs) for the Esposende region that, in addition to producing energy, can actively contribute to coastal protection.

According to Daniel Clemente, first author of the article, the multifaceted option is a very efficient application of technologies: “if we can protect our coast and generate renewable energy at the same time, why not explore? We need disruptive solutions for these two issues, but without neglecting to minimize possible conflicts with other uses of maritime space,” he explains. Francisco Taveira Pinto, leader of the Marine Energy and Hydraulic Structures group reinforces the idea: “the study illustrates the importance of the multifunctionality of harnessing wave energy.”

Green energy production

It is estimated that the two best performing structures in this wave energy park proposal (“W” at 280° and aligned “III” at 295° of the CEOs parks) could produce up to 341,353 GWh/year and 316,351 GWh/year, respectively. If we consider that the average electricity consumption per capita in Esposende is around 3,215 kWh in 2022, the best configuration could meet the annual needs of more than 100,000 inhabitants.

Coastal protection

The Portuguese coastline is very exposed to sea waves, with high energy levels, which raises challenges ranging from the construction of protective structures to the study of hydrodynamic interactions with coastlines such as erosion and flooding. This study made it possible to ascertain the local impact of the proposed park in terms of reducing the intensity of sea waves in a large area to the leeward of this location, by absorbing energy from the CEOs. The impact was particularly noticeable in terms of wave height and inherent energy, with significant attenuation as the coastline approached. Wave height reductions were, in some cases, greater than 25%.
Instead of following a more traditional logic of implementing “heavy” engineering solutions, this study allows us to take advantage of the energy available. Paulo Rosa Santos, co-leader of the same group at CIIMAR, tells us about the relevance of this innovative solution: “It is imperative to find and demonstrate the effectiveness of innovative and disruptive solutions to the traditional problems of coastal areas. This study shows that it is possible to protect the coast from the actions of the maritime environment and simultaneously produce clean electricity, thus supporting Portugal’s energy transition and self-sufficiency.”

A green energy country

In 2023, more than 60% of mainland Portugal’s electricity came from renewable energy sources, mainly hydroelectric, wind and solar. By incorporating wave energy, Portugal could become virtually self-sufficient or even an exporter of electricity, key milestones for national and European “green” energy transition and autonomy strategies. This energy could also feed other users and niche markets, such as offshore aquaculture and desalination, both of which have high national potential.

The future

The study in question has made it possible, in a realistic and comprehensive way, to transform a problem – coastal erosion off Esposende – into a multi-functional opportunity for renewable marine energy production and coastal protection, which can not only serve the local population affected by the case study, but provide a starting point for other work off the Portuguese coast. Contact with local communities and stakeholders will be fundamental for a viable, approved and improved proposal, in order to guarantee a solid solution that benefits all stakeholders, while satisfying energy needs and preserving the environment and landscape. According to Daniel Clemente, “in future stages, it will be important to further consolidate this challenging aspect with local communities and institutions, should there be interest in exploring the study’s proposal”, a goal that remains open for this and other possible parks along the Portuguese coast.

Ends.