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Note: This is a preprint of paper #1914 presented at the 14th European Wave & Tidal Energy Conference (EWTEC) 2021 in Plymouth, UK. The final version of paper with the same title can be found in the EWTEC 2021 proceedings. Abstract: Lift-based Wave Energy Converters (WECs) have a number of attractive features, including the potential for unidirectional rotation, simplifying power take-off and reduction in wave loads by reducing generation of circulation, increasing survivability. The common assumption of small body, small amplitude response, together with the Haskinds Relationship is used to determine the optimum motion for a lift-based WEC to maximise power capture. It is shown that whilst for a 2D hydrofoil in deep water the optimum motion is circular, the optimum motion for a finite-width hydrofoil is generally elliptical due to differences in the hydrodynamic damping coefficients associated with the vertical and horizontal motions of the hydrofoil. It is shown that more circular hydrofoil motion can be achieved by utilising the elliptical motion of the water particles in shallow water. This occurs because the increased horizontal water particle motion in shallow water results in an increase in the wave-induced lift force associated with horizontal fluid particle motions, and thus a reduction in the optimum amplitude of motion in this direction. Preliminary calculations suggest that for a 30 metre wide hydrofoil in wave periods of about 10 seconds, the ideal water depth (where the optimum hydrofoil motion is circular) occurs at around 25 metres, which is a highly utilisable water depth. Other advantages of deployment in shallower water include an improvement in the alignment of the waves parallel to the hydrofoil and a reduction in the structural task associated with reacting against the seabed. ; This work was produced as part of the LiftWEC Project. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 851885. This output ...

This document constitutes Deliverable 'D2.1 Preliminary Report on Synthesis of Design Knowledge' of the LiftWEC project. LiftWEC is a collaborative research project funded by the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No 851885. It is the intention of the project consortium that the LiftWEC project culminates in the identification of one or more promising configurations of a Wave Energy Converter operating through the use of a rotating hydrofoil that generates lift as the primary interaction with the incident waves. This report is intended to provide a preliminary foundation of the knowledge required to undertake the design of LiftWEC configurations in the project. ; This work was produced as part of the LiftWEC Project. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 851885. This output reflects the views only of the author(s), and the European Union cannot be held responsible for any use which may be made of the information contained therein.

This document constitutes Deliverable D2.3 'Review of Current Lift-Based WEC Concepts and Specification of Preliminary Configurations' of the LiftWEC project. LiftWEC is a collaborative research project funded by the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No 851885. It is the intention of the project consortium that the LiftWEC project culminates in the identification of one or more promising configurations of a Wave Energy Converter operating through the use of one or more rotating hydrofoils that generate lift as the primary interaction with the incident waves. This report compiles information on pre-existing lift-based Wave Energy Converters, reports on the development of Preliminary LiftWEC Configurations and provides direction to research efforts during the second phase of the LiftWEC project. In this document a literature survey is presented. This literature survey outlines information in the public domain relating to pre-existing lift-based Wave Energy Converters, as well as a small number of other devices which may be of interest to the consortium. As there are very few lift-based Wave Energy Converter concepts only a small number of devices are discussed. Furthermore, as there has historically been little interest in lift-based wave energy conversion, there is typically very little published literature even on those concepts. The notable exception to this is the CycWEC device, which has been the focus of study for a single research group for over 10 years and has been the focus of approximately 15-20 different publications. The CycWEC device is under development by the Atargis Energy Corporation and is a lift-based wave energy converter consisting of a pair of rotating hydrofoils that exploit lift to generate rotational shaft torque and ultimately, generate useful electrical output. The learning obtained from the literature review was both directly and indirectly fed into the first LiftWEC project workshop. The aim of this workshop was to generate a suite ...

Note: This is a preprint of paper #2074 presented at the 14th European Wave & Tidal Energy Conference (EWTEC) 2021 in Plymouth, UK. The final version of paper with the same title can be found in the EWTEC 2021 proceedings. Abstract: The majority of devices designed to extract energy from ocean waves operate through exploitation of the buoyancy (Froude-Krylov) and/or diffraction force regimes. Such devices extract energy through interaction with the displacement and/or acceleration of fluid particle motions respectively. By comparison, very little consideration has been given to systems which extract wave energy through coupling with fluid particle velocities. This paper performs a preliminary investigation into the hydrodynamics of a Wave Energy Converter (WEC) that is driven through interaction with the wave-induced fluid particle velocity. In particular, the work focuses on lift-based WECs consisting of a number of wave-driven, rotating hydrofoils. The paper develops a mathematical framework for such a system operating in regular, linear waves in 2D. It is noted that despite the unique nature of the device, it is possible to represent its operation using mathematics which are already familiar to the wave energy sector. The mathematical framework is subsequently used to investigate the performance of a pair of wave-driven, rotating hydrofoils. Results show that power capture efficiencies up to approximately 80% are potentially possible for the particular system considered under the constraints assumed. It is also found that the system is relatively insensitive to variations in design and control conditions. This suggests that further investigation is warranted to determine if lift-based WECs might represent a reasonable means of wave energy extraction. ; This work was produced as part of the LiftWEC Project. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 851885. This output reflects the views only of the author(s), and the ...

This document constitutes Deliverable D2.4 'Specification of Design and Evaluation Support Software Tools' of the LiftWEC project. LiftWEC is a collaborative research project funded by the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No 851885. It is the intention of the project consortium that the LiftWEC project culminates in the development of one or more promising configurations of a Wave Energy Converter operating through the use of one or more rotating hydrofoils that generate lift as the primary interaction with the incident waves. This report details a suite of Concept Design and Concept Evaluation support tools that will be developed to support the project in this goal. Concept Design support tools are tools that will be used to provide a rapid, approximate, yet representative indication of system characteristics for one or more particular characteristics of a wave-driven rotating hydrofoil system. The Concept Design support tools will enable users to gain familiarity with the fundamental system physics and develop an initial understanding of the potential influence of key design decisions on system performance without the need to resort to complex, high fidelity, computationally expensive numerical methods. Thus, Concept Design support tools will not exhaustively model all relevant physical processes influencing the given system performance characteristic, but rather will allow rapid, iterative investigation of the design space to identify key variable interdependencies. It is intended that Concept Design support tools will be developed which can; (1) identify the Optimum Hydrofoil Path, (2) estimate the system Power Capture, (3) identify the magnitude and nature of Cyclic/Reactive Energy cycled within the system, (4) estimate the Fundamental Reaction Forces, (5) estimate the Hydrofoil Reaction Torque, and (6) estimate the Annual Energy Production and Annual Structural Loading. The specifications of these Concept Design support tools are presented in this ...