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This paper presents a comprehensive review of boundary element methods for hydrodynamic modelling of wave energy systems. To design and optimise a wave energy converter (WEC), it is estimated that several million hours of WEC operation must be simulated. Linear boundary element methods are sufficiently fast to provide this volume of simulation and high speed of execution is one of the reasons why linear boundary element methods continue to underpin many, if not most, applied wave energy development efforts; however, the fidelity of the physics included is inadequate for some of the required design calculations. Judicious use of non-linear boundary element methods provides a route to increase the fidelity of the modeling while maintaining speed and other advantages over more computationally demanding alternatives such as Reynolds averaged Navier–Stokes (RANS) or smooth particle hydrodynamics (SPH). The paper presents some background to each aspect of the boundary methods reviewed, building up a relatively complete theoretical framework. Both linear and nonlinear methods are covered, and consideration is given to the computational complexity of the methods reviewed. The paper aims to provide a review that is useful in selection of the most appropriate techniques for the next generation of WEC design tools.

In this study, systems engineering techniques are applied to wave energy to identify and specify stakeholders’ requirements for a commercially successful wave energy farm. The focus is on the continental scale utility market. Lifecycle stages and stakeholders are identified. Stakeholders’ needs across the whole lifecycle of the wave energy farm are analyzed. A list of 33 stakeholder requirements are identified and specified. This list of requirements should serve as components of a technology performance level metric that could be used by investors and funding agencies to make informed decisions when allocating resources. It is hoped that the technology performance level metric will accelerate wave energy conversion technology convergence.

This paper presents a study of several factors that affect the long-term performance of Wave energy Converters (WECs) based on the methodology presented in de Andres et al. (2013). This methodology consists of a sea state selection technique (MaxDiss), then this selected sea states are introduced into a numerical model in order to calculate the power performance. Finally this data are interpolated with a non linear technique (Radial Basis functions) in order to obtain the long term performance of a WEC on a long met-ocean data series with low computational requirements. In this paper, three types of converter, a one body heaving converter (follower), a two-body resonant converter as well as a deep water flap are investigated. Also four different locations with different met-ocean conditions in terms of the scatter plots and the sea conditions (swell-wind sea) distribution were selected (North of Spain, West of Denmark, Chile and West of Ireland). The methodology worked perfectly for all the selected alternatives, although it was demonstrated to work better for non-resonant converters that are not band limited in their frequency response. Also, the classical method of power production assessment based on the power matrix was reviewed, analysing the analytical spectrum assumption. The influence of more than one peak spectrum on the power production was found to be large on a sea state by sea state basis (±200%) but also on the Annual Energy Production (±40%).

This paper will introduce the Systems Engineering process utilized by the Structured Innovation team. Following the process this paper will present two key elements derived from the analysis of a success-ful Wave Energy Farm: the capabilities and the functions. The capabilities are the goals of a Wave Energy Farm as determined from a condensed list of the stakeholder needs. The functions are the activities or behav-iors performed by the Wave Energy Farm in order to achieve the capabilities (i.e. the goals). At the framework level, both the functions and the capabilities remain independent of the design and these will be used to devel-op the list of requirements for a WEC in future work.

The successful development process of WECs demands large amounts of time and means. The optimal development trajectory manages to keep these expenses to a minimum while delivering an economically viable product at the end of its development. As related expenses (time and money) increase exponentially with the development stages (TRLs) while flexible parameters decrease rapidly, it is of the highest importance to optimise the WEC principles at an early stage (TRL 1-4) up to the level where the economic potential of the WEC is ensured (TPL > 7).

In wave energy, perhaps more so than any other industry, the economics of product development and product ownership are not separate from the product engineering and design. This is the case because, despite high potential of untapped energy resource and the constant attention of academic research and innovative companies and inventors, as yet no one has verifiably achieved a minimum viable product in a wave energy conversion system.

In this work, we present a methodology for the assessment of the economic value of ocean wave energy schemes. Such an assessment is a necessary tool for supporting investment decisions in the development of wave farms and in the development of wave energy converter (WEC) technology. To overcome the lack of operational experience, the methodology presented includes detailed operational simulations which relate the operational costs and the availability of the plant for power production to the characteristics of the device, the location, and the maintenance strategy chosen. The methodology consists of firstly, a productivity and costs assessment which embodies the operational simulations and secondly, a financial calculator which employs discounted cash-flow techniques to produce selected economic indicators. A case study, consisting of one hundred WECs units deployed off the West Coast of Ireland, is presented to exemplify the use of the methodology. The paper also explores how the key inputs to the assessment affect the economic performance of the case study project via a sensitivity analysis.

This work describes the overall aspects of the Competition on Hydrodynamic Modelling of a Rigid Body, a competition outlined to evaluate different ways to model and simulate the motions of a rigid body in waves. The main objective is to determine a hydrodynamic model for a submerged horizontal cylinder which best predicts a recorded motion to a specific excitation in panchromatic waves. A blind study was performed by the competition participants, i.e., the simulation results were obtained without knowledge of the actual recorded motion of the cylinder. Only the geometry of the cylinder in solid model and the time series of the incoming waves were issued to the participants. The proposed approaches by the participants for modelling the rigid body and the fluid motions are based on the boundary-integral equation methods (potential flow theory) with additional viscous damping forces, where the drag terms are calculated either empirically or via the Navier-Stokes equation method. This paper describes the details about rationale for choice of the rigid body, the experimental tests, the competition criteria and an overview of all modelling approaches proposed by the competition participants.Copyright © 2015 by ASME

To facilitate commercially relevant numerical design optimization in wave energy conversion accurate and validated simulations of wave body interactions are necessary. Wave energy, more so than almost any other industry, can benefit from such numerical optimization because of the high cost and long period of design iteration in experimental and field testing. For the foreseeable future wave energy device design and optimization will continue to rely heavily on potential flow solvers. Two important prerequisites to successfully using simulations based on these codes are firstly a need to validate the simulation implementation by comparison with experiment and secondly a need to supplement the potential flow solution with experimentally (or CFD) derived coefficients for the forces that are neglected by the potential flow solver. This paper attempts to address both of these prerequisites. A comparison of numerical simulations and physical wave tank experiments on a submerged horizontal cylinder moored in waves is presented. Good agreement between numerical model and experiment is achieved. At operating points where the body response is linear a numerical model based purely on potential flow and linear mooring stiffness achieves excellent results and at operating points where the body response is non-linear a time domain model with frequency independent quadratic damping is shown to give good agreement for a wide range of wave periods and amplitudes.

When large relative displacements take place between the bodies in a multi-body Wave Energy Conversion system linearisation of the constraints on motion imposed by the joints between the bodies is no longer valid and a non-linear timedomain analysis is necessary. As a part of the Techno-Economic Optimisation of Wave Energy Conversion (TEOWEC) software, which has been developed at the Centre for Ocean Energy Research (COER), NUI Maynooth, we developed an algorithm for the dynamic simulation of Multi-Body Systems for Wave Energy Conversion (MBS4WEC) with fully non-linear representation of the body-to-body joints. The algorithm is based on the Jointcoordinate formulation, which provides a systematic procedure to transform the mixed differential-algebraic equations of motion in body coordinates, for open chain systems, to a minimal set of ODEs. When a closed-loop chain occurs, the same method can be adopted by removing one or more kinematic joints from each loop. Knowing the topology of the system, a path matrix is generated and together with the formulation of data structures representing the body-to-body joints, the Velocity Transformation Matrix is computed. The main advantage of this approach is a fast and automatic generation of the Velocity Transformation Matrix, which leads to a higher computational efficiency, especially for complex systems. This paper presents the equations underpinning the method together with results for simulation of two specimen floating multi-body systems. These two are a simple multi-body hinged barge and a device with a sliding internal reaction mass. In each case the results are contrasted to the results produced by a linearised analysis of the same system.

OES Task 10 Modelling, Verification and Validation of Wave Energy Converters (WECs) is a task under the IEA Technology Collaboration Program for Ocean Energy Systems (OES). The longterm goals are to assess the accuracy of, and establish confidence in, the use of numerical WEC models, to determine a range of validity of existing computational modelling tools, to identify uncertainty related to simulation methodologies and finally to define future research. To some extent, this project builds on the experience from a similar effort carried out to verify modelling of wind turbines as part of the IEA Wind Task 30 on wind OC3-OC5.

This is the first joint reference paper for the Ocean Energy Systems (OES) Task 10 Wave Energy Converter modeling verification and validation group. The group is established under the OES Energy Technology Network program under the International Energy Agency. OES was founded in 2001 and Task 10 was proposed by Bob Thresher (National Renewable Energy Laboratory) in 2015 and approved by the OES Executive Committee EXCO in 2016. The kickoff workshop took place in September 2016, wherein the initial baseline task was defined. Experience from similar offshore wind validation/verification projects (OC3-OC5 conducted within the International Energy Agency Wind Task 30) [1], [2] showed that a simple test case would help the initial cooperation to present results in a comparable way. A heaving sphere was chosen as the first test case. The team of project participants simulated different numerical experiments, such as heave decay tests and regular and irregular wave cases. The simulation results are presented and discussed in this paper.