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Offshore wind with high energy density and low turbulence has attracted the global scientific community towards the development of the Offshore Wind Turbines (OWTs). Today, most of the shallow water sites are already occupied, and the industry is looking to install turbines at the deep water sites (water depth > 50m). However, an OWT support structure designed with the conventional concepts becomes massive and expensive in deeper waters. In contrast, floating OWTs are more expansive than the bottom supported ones, and considered suitable for a water depth of 60 m or more. A novel support structure concept termed a ‘bottom supported tension leg tower’ (BSTLT) has been proposed recently and the possibility of using bottom supported structures in deeper waters is shown. In this paper, an extension of the BSTLT concept has been achieved using inclined tethers with a monopile. The preliminary technical feasibility including the sensitivity of the natural frequencies and dynamic analyses considering the in-place operating and the extreme design conditions has been studied for 50 m water depth. The results show that the proposed concept can be utilized to make the monopile based support structures more cost-efficient for the water depth stated above.

In recent years, seaports have faced increasing pressure to transition towards a low-carbon and more sustainable energy model. In this context, the exploitation of the local wave energy resource may appear as a promising alternative. Therefore, the objective of this work is to present a methodology to select the best WEC-site combination to supply the energy demands of ports. To illustrate this methodology, the Port of Leixões (Portugal) is used as a case study. For the selection of wave energy sites in port areas, the methodology proposes a detailed spatial characterisation of both the wave resource and marine uses. For the area of study, having considered the main marine uses (sediment disposal, biodiversity, aquaculture, recreational and navigation), two exploitable wave energy sites (Areas I and II) with average annual energy resources of 24 and 17 kWm−1, respectively, were found. Next, the methodology proposes a techno-economic optimisation of WECs, based on the local wave conditions of Areas I and II, to minimise their associated Levelised Cost of Energy (LCoE). The results obtained confirm the effectiveness of the methodology, with the novel oCECO device, appearing as the most feasible option (with an LCoE of EUR 387.6/MWh) to exploit the wave potential in the surrounding areas of the port.

This paper discusses a disruptive approach to wave energy conversion, based on a hybrid solution: the E-Motions wave energy converter with integrated triboelectric nanogenerators. To demonstrate it, a physical modelling study was carried out with nine E-Motions sub-variants, which were based on three original hull designs (half-cylinder (HC), half-sphere (HS) and trapezoidal prism (TP)). A unidirectional lateral tribo-device was incorporated within the E-Motions’ hull during the experiments. The physical models were subjected to eight irregular sea-states from a reference study on the Portuguese coastline. Results point towards a significant hydrodynamic roll response, with peaks of up to 40 °/m. Three peaks were observed for the surge motions, associated with slow drifting at low frequencies. The response bandwidth of the HC sub-variants was affected by the varying PTO mass-damping values. By comparison, such response was generally maintained for all HS sub-variants and improved for the TP sub-variants, due to ballast positioning adjustments. Maximum power ratios ranged between 0.015 kW/m3 and 0.030 kW/m3. The TENGs demonstrated an average open-circuit voltage and power per kilogram ratio of up to 85 V and 18 mW/kg, respectively, whilst exhibiting an evolution highly dependent upon wave excitation, surge excursions and roll oscillations. Thus, TENGs enable redundant dual-mode wave energy conversion alongside E-Motions, which can power supporting equipment with negligible influence on platform hydrodynamics.

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.

Coastal zone management plans need to consider scenarios of coastline evolution and associated uncertainties. In this paper, the main causes of shoreline retreat and coastal erosion (natural and anthropogenic) in the north coast of Portugal are discussed. The importance of increasing knowledge on coastal dynamics to improve long-term predictions of coastline changes is highlighted since it is essential to establish proper management tools. It is also shown that the Portuguese coastal ecosystems are not resilient enough to extreme events and that the Portuguese coastal zone, like very many others worldwide, and will be severely affected by the effects of climate change. It is concluded that extreme events need to be properly characterized and their impacts assessed since they have important implications in terms of uses of either the coastal zone or the coastal waters. Without that analysis, coastal management plans will be lacking technical and scientific information and data that could help decision-makers define the best strategies to control erosion levels and the impact of extreme events related to climate change effects. Finally, a detailed assessment of the coastline evolution was performed for the new Caminha-Espinho coastal management program, for the time horizons 2050 and 2100, based on historical data. The methodology used for the evaluation of the rates of shoreline change, hazard mapping and definition of set-back lines is presented. Selected examples are given to demonstrate the potential of this methodology in supporting the development of coastal zone management plans, but also to highlight the limitations and uncertainties linked to the complexity of the phenomena under analysis.

Em resposta à solicitação da empresa Cabelte, S.A., sito na Rua de Espírito Santo, Arcozelo, 4410-420 Vila Nova de Gaia - Portugal, o Instituto de Hidráulica e Recursos Hídricos (IHRH) da Faculdade de Engenharia da Universidade do Porto (FEUP) elaborou o presente Relatório relativo à medição de Níveis Hidrostáticos (NHE) em duas Captações da Cabelte, S.A., Arcozelo - Vila Nova de Gaia, tendo como referência os elementos fornecidos, conhecidos e medidos à data deste relatório. Este estudo tem como objetivos: · Observação dos NHE em duas captações de águas existentes nos terrenos da empresa Cabelte, S.A., sito na Rua de Espírito Santo, Arcozelo, 4410-420 Vila Nova de Gaia; · Medições, com recurso a duas sondas de nível, dos NHE em duas captações (adiante identificadas por Furo 1 Central Norte e Furo 2 Central Sul) situadas nos terrenos da empresa Cabelte, S.A; · Neste documento é apresentada a metodologia seguida na realização dos trabalhos de campo, os equipamentos utilizados e os resultados obtidos com base nas medições efetuadas. O estudo foi coordenado pelo Prof. Francisco Taveira Pinto, Professor Catedrático da FEUP e pelo Prof. Joaquim Góis, Professor Auxiliar da FEUP

The buckling tendency of an offshore pipeline buried in a liquefiable soil aggravates under earthquake situations. Moreover, to understand the upheaval displacement behavior of an offshore pipeline under dynamic loading, it is crucial to understand the variation of liquefaction potential within the soil bed. Thus, in the present study, the variation of the liquefaction potential within the soil body and its effect on the pipeline upheaval displacement (u) and post-shake uplift resistance (Vup) is investigated using a finite element package called PLAXIS 2D. The study was performed for different seismic and soil conditions. To define the soil, two advanced constitutive models are used. The static stages are modelled with the ‘Hardening Soil Model with small strain’ (HSS model), while the dynamic stage is modelled with the PM4Sand model. Moreover, the problem is defined as a 2d plane strain problem. The pipe is considered to be covered with Nevada sand. Several parameters such as a sand-density index (Dr), pipe embedment depth (H), seismic frequency (f) and amplitude are varied to study the variation of the soil liquefaction potential, the pipe upheaval buckling and the post-shake uplift resistance. The model is validated with past studies and a considerable match is obtained. The liquefaction potential is shown using the shadings of a user-defined parameter called a pore water pressure ratio (ru). Moreover, the variation of pipe upheaval displacement (u) and pipe uplift resistance (Vup) are shown using various plots. Thus, it is observed that the liquefaction potential is reduced with an increase in the frequency and the amplitude of the seismic signal. Moreover, the peak upheaval buckling, and the duration of earthquake loading to reach the peak upheaval buckling, decreased with an increase in the earthquake signal frequency. Again, the variation of post-peak uplift resistance of the buried pipeline with the pipe embedment depth is observed to be independent of the signal parameters. However, the variation of uplift resistance of the pipeline with the soil relative density is influenced by the signal parameters.

Layout optimization of wave energy offshore parks is a challenging task, as it encompasses various design objectives and constraints attributed to the complex hydrodynamic interactions. The wave energy converter (WEC) park performance is affected by local environment and device characteristics. To solve this challenge, advanced numerical algorithms, including artificial intelligence, have been applied to a wide range of case studies. Nevertheless, this process remains incomplete, which keeps it as a pertinent research topic in the field of WEC development. The present paper provides an overview of the current state and research trends of offshore WEC park layout optimization. To analyze the state-of-the-art, the paper targets the last decades' research on this topic, summarizing the studies, addressing the optimization objective and the employed methods and separating them according to the corresponding technique. The review showed that the results strongly depend on the methodologies applied. Furthermore, a preferential use of computational intelligence techniques has been observed in recent years. (c) 2022 Elsevier Ltd

Assessing the evolution of the performance of water supply and sanitation services is essential to monitor progress towards the universalization of water services, as specified by the Sustainable Development Goal 6 of Agenda 2030, adopted by United Nations member countries. Brazil, a developing country with a continental size and geographical diversity, will face significant challenges to achieve this goal. The main objective of this paper is to evaluate the evolution of productivity of water supply and sanitation services in Brazilian municipalities in the period 2012-2019. The analysis also explores whether water services' performance is balanced across the country, with a specific analysis of performance at the macroregion level. From a methodological perspective, this research evaluates productivity change over time using a Malmquist Productivity Index estimated with a metafrontier, satisfying the circularity property. It also develops a pseudo Malmquist index that compares productivity levels across macro-regions. The results revealed a productivity loss of approximately 4% at the national level, with an unequal profile across the macro-regions. The Southeast municipalities stand out for exhibiting, on average, higher productivity levels than the South and Northeast municipalities.

This work was partially supported by the project PORTOS—Ports Towards Energy SelfSufficiency, with the reference EAPA_784/2018 and co-financed by the Interreg Atlantic Area Program through the European Regional Development Fund, and by the OCEANERA-NET COFUND project WEC4Ports—A hybrid Wave Energy Converter for Ports, with the reference OCEANERA/0004/2019, under the frame of FCT. This work was funded by the project ATLANTIDA (NORTE-01-0145-FEDER000040), supported by the North Portugal Regional Operational Programme (NORTE2020), under the PORTUGAL 2020 Partnership Agreement and through the European Regional Development Fund (ERDF).

Wave climate and associated energy characterization is essential for an assessment of a country’s renewable energy potential. A wave model was validated against satellite data with good performance in terms of error metrics. The hindcast data, covering the period 1979–2018, was used to describe the spatial, seasonal and interannual variability and trend of wave energy flux along the United Arab Emirates coastline. The annual mean wave energy flux along the study area is higher at the central region reducing towards the south and north. The wave energy shows a clear seasonality and interannual variability for all locations with higher and lower energy during winter and autumn, respectively. A trend analysis of the historical data indicates an increase in annual mean energy flux along the coast. Alongshore, seasonal and interannual variability of wave energy flux and direction should be considered in the initial stages of marine renewable energy projects. A detailed analysis of historical wave energy trends and influence of large-scale climate indices will be particularly relevant for longer-term projects.

Em resposta à solicitação da Cabelte, Cabos Eléctricos e Telefónicos, S.A., sito na Avenida da Indústria, nº 380 e 382 Ribeirão - V.N. de Famalicão - Portugal, o Instituto de Hidráulica e Recursos Hídricos (IHRH) da Faculdade de Engenharia da Universidade do Porto (FEUP) elaborou este Relatório Final relativo à medição de a Níveis Hidrostáticos (NHE) em Captações da Cabelte, S.A., Ribeirão - Famalicão, desenvolvido tendo como referência os elementos fornecidos, conhecidos e medidos até à data. Este estudo tem como objetivos: * Observação dos NHE em duas captações de águas existentes nos terrenos da empresa Cabelte, Cabos Elétricos e Telefónicos, S.A., sito na Av. da Indústria, 380 e 382, Bragadela, 4760-706 Ribeirão (Famalicão); * Medições, com recurso a duas sondas de nível, dos NHE em duas captações (adiante identificadas por P18 e P19) situadas nos terrenos da empresa Cabelte, Cabos Elétricos e Telefónicos, S.A. * Neste documento é apresentada a metodologia seguida na realização dos trabalhos de campo, os equipamentos utilizados e os resultados obtidos com base nas medições efetuadas. O estudo foi coordenado pelo Prof. Francisco Taveira Pinto, Professor Catedrático da FEUP e pelo Prof. Joaquim Góis, Professor Auxiliar da FEUP.

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.

Buckling is a crucial phenomenon to be considered in offshore pipelines and is dependent on the resistance of the surrounding soil, which depends on the diameter of the pipe (D) and embedment depth (H). In this study, the behaviour of the failure mechanisms and the capacity factors are investigated for a practical range of embedment depth (H) and diameter of offshore pipelines (D), using Indian coastal clay properties. A 2D plane-strain model was created using a finite element package PLAXIS 2D validated against previous studies. The immediate breakaway and no breakaway conditions are analyzed. The capacity factors are observed to increase with increasing embedment depth, up to a peak value and remain constant for further increase in embedment depth. The capacity factors are observed to be decreasing with increasing pipeline diameter. The failure mechanisms are shown using displacement contour diagrams and stress contours.