An application of model predictive control logic to inertial sea wave energy converter

Genuardi, Lorenzo; Bracco, Giovanni; Sirigu, Sergej Antonello; Bonfanti, Mauro; Paduano, Bruno; Dafnakis, Panagiotis; Mattiazzo, Giuliana

doi:10.1007/978-3-030-20131-9_351

Cited by 17 publications

(9 citation statements)

References 8 publications

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“…The derivation of the dynamic model equations for the complete system (hydrodynamics of the hull and PTO equations) is not in the scope of this work and details can be found in [36]. Furthermore, an accurate description of the internal components of the full-scale device and a more detailed discussion on the hull design can be found in [37].…”

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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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

Self Cite

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“…Economic viability is the sine qua non condition for commercial competitiveness and industrial sustainability of the wave energy conversion sector and it can be achieved only through substantial reduction of costs and increase in performance. Both such objectives can be accomplished only through holistic design, control, and optimization studies, the effectiveness of which strongly depends on the accuracy of mathematical models [2,3]. However, a major limiting factor for the feasibility of application of a particular mathematical model is the computational time.…”

Section: Introductionmentioning

confidence: 99%

NLFK4ALL: An Open-Source Demostration Toolbox for Computationally Efficient Nonlinear Froude-Krylov Force Calculations

Giorgi¹,

Bracco²,

Mattiazzo³

2021

14th WCCM-ECCOMAS Congress

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Accurate modelling of wave-structure interaction is essential for a successful and reliable design of offshore structures and their ancillary systems. However, the fidelity of mathematical models is challenged when nonlinearities become significant, i.e. when the floater operates in severe sea states and/or it shows large dynamic responses compared to the incoming wave. This is normally the case for wave energy converters (WECs) because large motions are desirable for better power extraction, while conventional offshore structures are usually designed to prevent large responses and ensure stability. Fast computation is a further mandatory requirement for mathematical models that are used for design purposes. This is particularly true for wave energy applications, since extensive parametric studies are needed to minimize the cost of energy, i.e. increase power extraction capabilities while limiting capital and operational expenditures. Furthermore, model-based control strategies, essential for substantial increase of the WEC performance, require representative mathematical models. The requirements of accuracy and low computational time are usually contrasting, so an appropriate compromise should be defined. This paper proposes a nonlinear Froude-Krylov (NLFK) force model for axisymmetric floaters. The symmetry of the geometry (common for WECs) is exploited to achieve a low computational time (about real-time computation). Furthermore, since NLFK forces are the main nonlinearities for such devices, the obtained accuracy is higher than linear models. An open-source Matlab demonstration toolbox is introduced, called NLFK4ALL (doi: 10.5281/zenodo.3544848), which provides a ready-to-use implementation of the NLFK approach in six degrees of freedom. Accuracy and computational aspects of the method are here discussed, such as the complexity of the analytical description of the intersection between free surface elevation and the floater, and the impact of tolerances on the convergence of the numerical integration.

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“…Since parametric resonance and mooring loads are mutually influencing, the mooring system can be effectively exploited as an additional degree of freedom for the WEC developer: The configuration of the mooring lines can be optimized to limit the effect of parametric instability, while being compliant with the main power production objective [35]. For example, [28,36] show how the magnitude of the parametric response is affected by the stiffness of the system, which can be modified by appropriate mooring design.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Mooring Line Parameters in Inducing Parametric Resonance on the Spar-Buoy Oscillating Water Column Wave Energy Converter

Giorgi

Gomes

Bracco

et al. 2020

JMSE

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Although it is widely accepted that accurate modeling of wave energy converters is essential for effective and reliable design, it is often challenging to define an accurate model which is also fast enough to investigate the design space or to perform extensive sensitivity analysis. In fact, the required accuracy is usually brought by the inclusion of nonlinearities, which are often time-consuming to compute. This paper provides a computationally efficient meshless nonlinear Froude–Krylov model, including nonlinear kinematics and an integral formulation of drag forces in six degrees of freedom, which computes almost in real-time. Moreover, a mooring system model with three lines is included, with each line comprising of an anchor, a jumper, and a clump weight. The mathematical model is used to investigate the highly-nonlinear phenomenon of parametric resonance, which has particularly detrimental effects on the energy conversion performance of the spar-buoy oscillating water column (OWC) device. Furthermore, the sensitivity on changes to jumper and clump-weight masses are discussed. It is found that mean drift and peak loads increase with decreasing line pre-tension, eventually leading to a reduction of the operational region. On the other hand, the line pre-tension does not affect power production efficiency, nor is it able to avoid or significantly limit the severity of parametric instability.

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An application of model predictive control logic to inertial sea wave energy converter

Cited by 17 publications

References 8 publications

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

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

NLFK4ALL: An Open-Source Demostration Toolbox for Computationally Efficient Nonlinear Froude-Krylov Force Calculations

The Effect of Mooring Line Parameters in Inducing Parametric Resonance on the Spar-Buoy Oscillating Water Column Wave Energy Converter

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