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Abstract This work aims to get a better insight into the behaviour of CECO, an oscillating-body wave energy converter that presents a singular feature: the motion of its oscillating part is restricted to translations along an inclined axis. In order to study in the time domain the response of CECO for a wide range of wave conditions, a hybrid numerical approach based on the Boundary Element Method (BEM) and the Morison’s equation was used. The effects of the power take-off system were included in the numerical model and calibrated with the results from previous wave basin experiments. The results show that CECO is able to capture up to 40% of the incident wave energy when the direction of translation is 45°. However, if the direction of translation is vertical, the amount of captured wave energy decreases almost three times. This investigation demonstrates the advantage of limiting the oscillation of the CECO floating part to an inclined direction and reaffirms the concept as a promising technology for wave energy conversion.

Oscillatory wave energy converters of the sloped type may allow absorbing power from ocean waves efficiently if a valid optimal design is used. In earlier studies, the optimized geometry for the CECO device was defined by implementing a simplified frequency-domain model. In this paper, that geometry is evaluated against the former one by taking into consideration a more realistic modelling approach and assessment scenario. The two geometries were benchmarked through a time-domain model, which allows taking into account realistic sea states and the use of end-stops to limit the amplitude of CECO motions. It was concluded that the optimized geometry allows extra energy production for most of the irregular sea states evaluated (45% more annual energy production). Performance indices were also used to compare the two geometries and it was concluded that the optimized geometry was particularly advantageous for the more energetic sea states. Overall, this study clearly shows that the choice of the generator rated power and end-stops span length are key aspects in determining realistically the annual energy production of sloped-motion wave energy converters.

Abstract This work investigates the performance of CECO, a third-generation wave energy converter of the oscillating bodies group. The power matrices of the device – which represent the wave power absorbed for different sea states – are obtained for five PTO inclinations. Then, the wave climate along the west coast of the Iberian Peninsula is characterized by means of the wave energy resource matrices. With the power matrices and the wave energy resource matrices, the performance of the device along the area of study is determined for each PTO inclination. To achieve this, the performance of CECO is assessed by means of a panel model based on the boundary element method, while the wave conditions in the area of study are assessed with a wave propagation spectral model. The results allow fulfilling an important knowledge gap concerning the impact of the PTO inclination on the performance of CECO, which was found to be very significant. In addition, the insight obtained will contribute to optimize future versions of CECO and other wave energy converters of the oscillating body type.

This work reviews the advances in the development of CECO, a wave energy converter (WEC) of the floating oscillating bodies subgroup that has its motions and power take-off system (PTO) restricted to an inclined direction. For this purpose, the review is conducted on the basis of the Technology Readiness Levels (TRLs), the most frequently used metric to assess the maturity of a technology. The main conclusions and milestones of each stage are also presented along with an introduction to the ongoing works and a general picture of future research lines.

CECO is a wave energy converter (WEC) of the oscillating body type equipped with an inclined PTO system and being developed at the Faculty of Engineering of the University of Porto. In the last years, several research studies have been performed to assess and to improve the performance of this WEC, using both physical model tests and numerical simulations. The main objective of this paper is reviewing the most significant findings of past research works, so as to provide a detailed overview about the present status of knowledge, but also presenting recent outcomes on the development of CECO and the next research steps. It discusses the influence of the PTO slope angle and damping on the efficiency of CECO harvesting wave energy and describes its energy conversion stages. Furthermore, the intra-annual variability of the wave resource (i.e., on a monthly basis) is considered in the analysis of the influence of the PTO inclination and local water depth at the deployment site on CECO captured energy and captured energy efficiency, along the North Atlantic coast of the Iberian Peninsula. The results have shown significant differences between the summer and winter months and also highlighted the fact that the initial geometry of this WEC is more suitable for the less energetic wave climates, characteristic of the southern locations of the case study area and of shallow waters. The conclusions obtained supported the design of an enhanced version of CECO, prepared for the more energetic stretches of the study area, which presents a hydrodynamic efficiency of more than twice the original one, for the target wave conditions.

This is the first assessment of the wave energy resource in Peru, an emerging country with an increasing energy demand and a high dependence on fossil fuels. On the basis of wave buoy measurements, we characterize the offshore wave energy resource and analyze its temporal variability, comparing the results with those obtained in previous works for other regions. A wave propagation numerical model (SWAN) is used to determine the nearshore spatial distribution of wave energy. A total of 357 offshore sea states, representing 90% of the wave energy and 94% of the time in an average year, were propagated. The wave energy in Peru presents a resource exceeding by more than seven times the total electric demand of the country. Because of the large amount of resource available and its low seasonal variation, wave energy must be considered in Peru as an alternative to conventional energy resources.

Wave farm planning in a coastal region should lead to the selection of: i) the type of technology of wave energy converter (WEC) providing the highest performance at specific sites and ii) the sites for wave farm operation allowing an integrated coastal zone management (ICZM). On these bases, the deployment of a wave farm should be based on an accurate analysis of the performance of different WECs at coastal locations where wave energy exploitation does not interfere with other coastal uses, and the environmental impact is minimised (or positive, e.g. allowing coastal protection). With this in view, in this piece of research the intra-annual performance of various WECs of the same type (buoy-type) is computed at different locations in NW Spain allowing an ICZM perspective. For this purpose, the intra-annual version of WEDGE-p® (Wave Energy Diagram Generator – performance) tool is implemented. The results show that, as opposed to previous analysis on WECs with different principle of operation, the level of performance of buoy-type WECs at specific locations may present strong similarities. In this case, an accurate computation of different performance parameters along with their joint analysis emerge as a prerequisite for an informed decision-making. WEDGE-p® tool is the result of an extensive work developed in the framework of several research projects supported by the Ministry of Science and Innovation: Evaluación de los Recursos Energéticos Renovables (Ref. DPI2009-14546-CO2-02), Xunta de Galicia: Consolidación e estruturación – 2016 CIGEO (Ref ED431B 2019/30), Fundación Iberdrola: Online Application and High Resolution Management System for the Exploitation of the Wave Energy Resource in the Atlantic Region of Europe, and Fundación Barrié: Development of a Geospatial Database for the Exploitation of the Wave Energy Resource along the Galician Coast. During this work I. López was supported by the postdoctoral grant ED481B 2016/125-0 of the ‘Programa de Axudas á etapa posdoutoral da Xunta de Galicia’. The authors are grateful to Puertos del Estado for providing the wave data, and to Instituto Español de Oceanográfía (IEO) and Instituto Técnolóxico para o Control do Medio Mariño de Galicia (Intecmar) for the ocean uses and environmental data. SI

Abstract CECO is a recently proposed Wave Energy Converter (WEC), which harnesses both the kinetic and potential energy of waves. Currently, CECO is at the third level of technology readiness (TRL3). In this context, maximising the wave energy absorption under a wide range of wave conditions is crucial for the future development of the device. Therefore, this work aims to explore in detail the main parameters (operating water depth and wave conditions) that influence CECO's performance in terms of Captured Energy ( C E ) and Captured Energy Efficiency ( C E E f f ). For this purpose, a panel-based model, which was calibrated from previous physical model tests was used to construct the CECO matrices of absorbed wave power at different operating water depths. The wave conditions of the Atlantic coast of the Iberian Peninsula (2005–2014), which were modelled using SWAN, were used as case study. Overall, CECO offers promising results for C E and C E E f f , reaching values up to 600 M W h and 45%, respectively. In addition, it was found that CECO's power absorption reaches its maximum for values of peak wave periods ( T p ) ranging from 10 to 13 s and the fact that the operating water depth does not impact significantly the performance of the device.