• Energy Research

This study investigates the impact of climate change on the wave energy potential along the Atlantic coast of the Iberian Peninsula, a region acknowledged for its high wave energy resource. The research focuses on the annual and intra-annual variations in wave power for the high-emission RCP8.5 global warming scenario over different time frames: historical, near-future, and far-future. The results show a decreasing trend in the wave energy resource throughout the study area, with the most notable reductions observed in the northwestern region. The reduction in maximum annual power ranges from 15.1 to 7.2 kW/m. Changes in atmospheric circulation patterns and ocean surface temperature gradients induced by climate change effects could explain these results. This study also discusses the impacts of wave power projections on the design of wave energy converters and their future operation. The outcomes are of high interest to adapt the renewable energy infrastructure to a changing climate, ultimately also aiding in the strategic planning and cost-effective design of future wave energy projects.

The combined exploitation of wave and offshore wind energy resources is expected to improve the cost competitiveness of the wave energy industry as a result of shared capital and operational costs. In this context, the objective of this work is to explore the potential benefits of co-locating CECO, an innovative wave energy converter, with the commercial WindFloat Atlantic wind farm, located on the northern coast of Portugal. For this purpose, the performance of the combined farm was assessed in terms of energy production, power smoothing and levelised cost of energy (LCoE). Overall, the co-located farm would increase the annual energy production by approximately 19% in comparison with the stand-alone wind farm. However, the benefits in terms of power output smoothing would be negligible due to the strong seasonal behaviour of the wave resource in the area of study. Finally, the LCoE of the co-located farm would be drastically reduced in comparison with the stand-alone wave farm, presenting a value of 0.115 per USD/kWh, which is similar to the levels of the offshore wind industry as of five years ago. Consequently, it becomes apparent that CECO could progress more rapidly towards commercialisation when combined with offshore wind farms.

The offshore wind is the sector of marine renewable energy with the highest commercial development at present. The margin to optimise offshore wind foundations is considerable, thus attracting both the scientific and the industrial community. Due to the complexity of the marine environment, the foundation of an offshore wind turbine represents a considerable portion of the overall investment. An important part of the foundation’s costs relates to the scour protections, which prevent scour effects that can lead the structure to reach the ultimate and service limit states. Presently, the advances in scour protections design and its optimisation for marine environments face many challenges, and the latest findings are often bounded by stakeholder’s strict confidential policies. Therefore, this paper provides a broad overview of the latest improvements acquired on this topic, which would otherwise be difficult to obtain by the scientific and general professional community. In addition, this paper summarises the key challenges and recent advances related to offshore wind turbine scour protections. Knowledge gaps, recent findings and prospective research goals are critically analysed, including the study of potential synergies with other marine renewable energy technologies, as wave and tidal energy. This research shows that scour protections are a field of study quite challenging and still with numerous questions to be answered. Thus, optimisation of scour protections in the marine environment represents a meaningful opportunity to further increase the competitiveness of marine renewable energies.

Harnessing and using marine renewable energy at seaports is a promising solution to put these energy-intensive infrastructures on the right track to energy self-sufficiency and environmental sustainability, reducing their carbon footprint. This paper presents a summary of the main conclusions and achievements of a recently concluded R&D project that encompassed the experimental study of an innovative hybrid wave energy converter integrated into a case-study rubble-mound breakwater in the Port of Leixões, Portugal. It also describes the prospective studies planned in two ongoing projects, PORTOS – Ports Towards Energy Self-Sufficiency and WEC4Ports – A hybrid Wave Energy Converter for Ports, intended to further develop and assess this promising technology. It has been demonstrated that its wave-to-wire efficiency and annual energy production are 27.3% and 35.0 MWh/m per year, respectively, for the case-study location. Hence, a 240 m long device could provide more than half of the port’s electricity consumption, which vows for the device’s potential. Moreover, the impact of its integration into the case-study breakwater showed that it leads to a 50% reduction of overtopping discharges over the structure, and no significant effects on the structure’s wave reflection, although the stability of the toe berm blocks was negatively impacted. Overall, the conclusions obtained are favourable to the integration of this technology into rubble-mound breakwaters. Notwithstanding, further research is still needed, namely in terms of wave forces acting upon the structure, important for the assessment of the functional performance and lifecycle readiness of the technology, and the use of PTO control strategies. This is being addressed in PORTOS and WEC4Ports projects.

Tidal power technology is at its mature stage and large deployments are soon expected. The characteristics of tidal energy and its advantage to be predictable make it an ideal type of resource to be coupled with energy storage facilities. Despite this, most energy storage facilities are expensive. The fact that water has a high specific heat capacity makes this a potential cost-effective medium to be used for storing large amounts of thermal energy for balancing renewable energy output. This paper is an investigation on the possible application of integrating hot water reservoirs for storing tidal energy during power output peaks for domestic use. The main objective of this study is to evaluate the major factors incident on the proposed solution and to provide considerations on which real remunerations the proposed idea could bring to communities or to single families. For this purpose, a simplified numerical analysis, concerning three different scenarios, was performed. These scenarios differ by type of buildings and type of thermal energy demand. The study mainly concerns remote communities. Findings indicated that the proposed idea is technically feasible and if applied in the context of residential compounds, this could be more attractive in economic terms.

Abstract Marine Renewable Energy (MRE) sources, such as offshore wind, waves, tides, ocean currents, thermal and salinity gradients, appear as promising low-carbon forms of energy. However, with the sole exception of offshore wind, MRE exploitation is far from being commercially feasible. Among the obstacles faced by the sector, the complex legal framework that applies to MRE projects stands out. In this context, the objective of this work is to assess the main aspects of the MRE legal framework, and when necessary, propose corrective measures for further development of the sector. For this purpose, the countries of the Atlantic region of Europe (France, Ireland, Portugal, Spain, and the UK), which present one of the world's largest MRE resource, were used as a benchmark. Overall, the adoption of marine planning policies contributes positively to the development of the sector, defining priority areas for MRE exploitation and establishing clear preference criteria with other maritime activities. Furthermore, streamlining licensing procedures and periods, ideally adopting a one-stop-shop approach like the case of Scotland, becomes essential to attract new developers and investors to the MRE sector. Finally, the examples of Ireland, Portugal and especially the UK, show that the adoption of MRE sectoral plans, including actions for financial support, technology progress and supply chain development, is essential to achieve a fully-fledged MRE industry.

Absorbing wave power from oceans for producing a usable form of energy represents an attractive challenge, which for the most part concerns the development and integration, in a wave energy device, of a reliable, efficient and cost-effective power take-off mechanism. During the various stages of progress, for assessing a wave energy device, it is convenient to carry out experimental testing that, opportunely, takes into account the realistic behaviour of the power take-off mechanism at a small scale. To successfully replicate and assess the power take-off, good practices need to be implemented aiming to correctly scale and evaluate the power take-off mechanism and its behaviour. The present paper aims to explore and propose solutions that can be applied for reproducing and assessing the power take-off element during experimental studies, namely experimental set-ups enhancements, calibration practices, and error estimation methods. A series of recommendations on how to practically organize and carry out experiments were identified and three case studies are briefly covered. It was found that, despite specific options that can be strictly technology-dependent, various recommendations could be universally applicable.