Non Linear Simulation of a Wave Energy Converter With Multiple Degrees of Freedom Using a Harmonic Balance Method

Novo, Riccardo; Bracco, Giovanni; Sirigu, Sergej Antonello; Mattiazzo, Giuliana; Mérigaud, Alexis; Ringwood, John V.

doi:10.1115/omae2018-78067

Cited by 6 publications

(4 citation statements)

References 8 publications

(16 reference statements)

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“…However, for an example case with Coulomb damping in the PTO and a correspondingly non-smooth WEC output, the NLFD takes a long time to converge, and in fact, takes longer than the RK2 integrator and does not achieve the same level of accuracy. The NLFD method is extended to multiple DoF in Novo et al [342], considering the pitching hull motion and the internal gyroscope dynamics of the ISWEC device operating at a site in the Mediterranean Sea as a case study. The study showed that the NLFD method is sensitive to the algorithm starting point and found for some highly energetic sea states the method did not converge.…”

Section: Nonlinear Frequency Domainmentioning

confidence: 99%

Efficient Nonlinear Hydrodynamic Models for Wave Energy Converter Design—A Scoping Study

Davidson

Costello²

2020

JMSE

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This review focuses on the most suitable form of hydrodynamic modeling for the next generation wave energy converter (WEC) design tools. To design and optimize a WEC, it is estimated that several million hours of operation must be simulated, perhaps one million hours of WEC simulation per year of the R&D program. This level of coverage is possible with linear potential flow (LPF) models, but the fidelity of the physics included is not adequate. Conversely, while Reynolds averaged Navier–Stokes (RANS) type computational fluid dynamics (CFD) solvers provide a high fidelity representation of the physics, the increased computational burden of these models renders the required amount of simulations infeasible. To scope the fast, high fidelity options, the present literature review aims to focus on what CFD theories exist intermediate to LPF and RANS as well as other modeling options that are computationally fast while retaining higher fidelity than LPF.

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Section: Nonlinear Frequency Domainmentioning

confidence: 99%

Efficient Nonlinear Hydrodynamic Models for Wave Energy Converter Design—A Scoping Study

Davidson

Costello²

2020

JMSE

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“…The PTO is an electrical torque generator connected to the gyroscope support frame through a gearbox with a gear ratio 1/10. The maximum energy extraction rate is obtained by properly tuning the flywheel spinning speed with the incoming sea state and controlling the PTO torque [35].…”

Section: Iswec Devicementioning

confidence: 99%

Experimental Investigation of the Mooring System of a Wave Energy Converter in Operating and Extreme Wave Conditions

Sirigu

Bonfanti

Begović

et al. 2020

JMSE

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A proper design of the mooring systems for Wave Energy Converters (WECs) requires an accurate investigation of both operating and extreme wave conditions. A careful analysis of these systems is required to design a mooring configuration that ensures station keeping, reliability, maintainability, and low costs, without affecting the WEC dynamics. In this context, an experimental campaign on a 1:20 scaled prototype of the ISWEC (Inertial Sea Wave Energy Converter), focusing on the influence of the mooring layout on loads in extreme wave conditions, is presented and discussed. Two mooring configurations composed of multiple slack catenaries with sub-surface buoys, with or without clump-weights, have been designed and investigated experimentally. Tests in regular, irregular, and extreme waves for a moored model of the ISWEC device have been performed at the University of Naples Federico II. The aim is to identify a mooring solution that could guarantee both correct operation of the device and load carrying in extreme sea conditions. Pitch motion and loads in the rotational joint have been considered as indicators of the device hydrodynamic behavior and mooring configuration impact on the WEC.

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“…A practical implementation of an all-encompassing design optimisation is challenging, mainly due to the vast multi-dimensional search space which cannot be tackled with conventional global optimisation approaches due to computational limitations. Moreover, often there is no analytical representation of the relationship between input and output variables, due to hydrodynamic curves defined by points through panel-based simulations (BEM) and implicit nonlinearities requiring simulation via time-advancing schemes [17], or in some conditions, harmonic balance [18]. Therefore, both cost function and constraints usually behave as grey or black boxes.…”

Section: Introductionmentioning

confidence: 99%

Techno-Economic Optimisation for a Wave Energy Converter via Genetic Algorithm

Sirigu

Foglietta

Giorgi

et al. 2020

JMSE

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Although sea and ocean waves have been widely acknowledged to have the potential of providing sustainable and renewable energy, the emergence of a self-sufficient and mature industry is still lacking. An essential condition for reaching economic viability is to minimise the cost of electricity, as opposed to simply maximising the converted energy at the early design stages. One of the tools empowering developers to follow such a virtuous design pathway is the techno-economic optimisation. The purpose of this paper is to perform a holistic optimisation of the PeWEC (pendulum wave energy converter), which is a pitching platform converting energy from the oscillation of a pendulum contained in a sealed hull. Optimised parameters comprise shape; dimensions; mass properties and ballast; power take-off control torque and constraints; number and characteristics of the pendulum; and other subcomponents. Cost functions are included and the objective function is the ratio between the delivered power and the capital expenditure. Due to its ability to effectively deal with a large multi-dimensional design space, a genetic algorithm is implemented, with a specific modification to handle unfeasible design candidate and improve convergence. Results show that the device minimising the cost of energy and the one maximising the capture width ratio are substantially different, so the economically-oriented metric should be preferred.

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Non Linear Simulation of a Wave Energy Converter With Multiple Degrees of Freedom Using a Harmonic Balance Method

Cited by 6 publications

References 8 publications

Efficient Nonlinear Hydrodynamic Models for Wave Energy Converter Design—A Scoping Study

Efficient Nonlinear Hydrodynamic Models for Wave Energy Converter Design—A Scoping Study

Experimental Investigation of the Mooring System of a Wave Energy Converter in Operating and Extreme Wave Conditions

Techno-Economic Optimisation for a Wave Energy Converter via Genetic Algorithm

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