• Energy Research

This study deals with the initialization of three-dimensional wave field computations. We carry out such simulations with an HOS model developed at LMF-ECN since 2002 and based on the work of West et al. (1987) and Dommermuth & Yue (1987). In such models, initial conditions for three-dimensional realistic sea state computation are obtained by linearly distributing energy density spectrum. This however implies a relaxation of the non-linear effects as proposed by Dommermuth (2000) for bi-dimensional monochromatic wave train and Tanaka (2001), over several tenths of wave periods. The present work tests those former initialization methods and exposes an alternative initialization based on a non-linear three-dimensional approach. Non-linear interaction processes are both accounted in the spectra of elevation and potential of velocity, in accordance with the formulation of Dalzell (1999) at second order in wave steepness. Non-linear energy calculation is then addressed and the efficiency of the methods as well as their possible impact on properties and statistics of the wave field are investigated.

This study deals with the initialization of three-dimensional wave field computations. We carry out such simulations with an HOS model developed at LMF-ECN since 2002 and based on the work of West et al. (1987) and Dommermuth & Yue (1987). In such models, initial conditions for three-dimensional realistic sea state computation are obtained by linearly distributing energy density spectrum. This however implies a relaxation of the non-linear effects as proposed by Dommermuth (2000) for bi-dimensional monochromatic wave train and Tanaka (2001), over several tenths of wave periods. The present work tests those former initialization methods and exposes an alternative initialization based on a non-linear three-dimensional approach. Non-linear interaction processes are both accounted in the spectra of elevation and potential of velocity, in accordance with the formulation of Dalzell (1999) at second order in wave steepness. Non-linear energy calculation is then addressed and the efficiency of the methods as well as their possible impact on properties and statistics of the wave field are investigated.

Floating marine structures implement real-time wave excitation force prediction to address optimal control issues. The accuracy of force prediction relies on adequate wave forecasting. This paper presents a comprehensive analysis of deterministic wave forecasting by considering various wave steepnesses and directional spreads. In addition, we introduce new methods for predicting wave excitation forces acting on the floating body of interest. The methods are based on a set of frequency coefficients of wave excitation forces, which are generated in conjunction with wave amplitude parameters optimized in the data assimilation and frequency response functions obtained from boundary element method tools. These approaches offer the advantage of streamlining the calculation process, eliminating the need for simulating wave surfaces through wave propagation. Moreover, for the first time, we study a prediction zone for wave excitation forces by comparing predicted forces with theoretical forces. Lastly, the force prediction is validated against experiments conducted on a captive platform model in both unidirectional and multidirectional sea states.

Floating marine structures implement real-time wave excitation force prediction to address optimal control issues. The accuracy of force prediction relies on adequate wave forecasting. This paper presents a comprehensive analysis of deterministic wave forecasting by considering various wave steepnesses and directional spreads. In addition, we introduce new methods for predicting wave excitation forces acting on the floating body of interest. The methods are based on a set of frequency coefficients of wave excitation forces, which are generated in conjunction with wave amplitude parameters optimized in the data assimilation and frequency response functions obtained from boundary element method tools. These approaches offer the advantage of streamlining the calculation process, eliminating the need for simulating wave surfaces through wave propagation. Moreover, for the first time, we study a prediction zone for wave excitation forces by comparing predicted forces with theoretical forces. Lastly, the force prediction is validated against experiments conducted on a captive platform model in both unidirectional and multidirectional sea states.

This paper details a comprehensive study of deterministic real-time wave forecasting in directional seas. By using wave models on the basis of a Lagrangian description, a good balance was achieved between computational efficiency and model accuracy. Nevertheless, due to the highly non-uniform spatial distribution of data and the relatively small size of data in time inherent to remote optical measurements, the initial conditions are determined through an optimization process, which is computationally demanding, especially in multidirectional sea states. Accordingly, in order to offer a real-time system of wave prediction in the case of multidirectional waves, we propose a simplified and succinct assimilation method for the process of wave reconstruction. We also develop a three-dimensional spatio-temporal prediction zone where the future evolution of wave fields can be estimated based on wave measurements. Lastly, we outline a tank-scale experimental campaign conducted to mimic the measurements of a LIDAR in a real configuration. A comparison of model performances with the experimental observations shows that in a multidirectional approach, it is necessary to consider wave components in direction as well as in frequency to achieve nearly the same accuracy as for unidirectional seas.

This paper details a comprehensive study of deterministic real-time wave forecasting in directional seas. By using wave models on the basis of a Lagrangian description, a good balance was achieved between computational efficiency and model accuracy. Nevertheless, due to the highly non-uniform spatial distribution of data and the relatively small size of data in time inherent to remote optical measurements, the initial conditions are determined through an optimization process, which is computationally demanding, especially in multidirectional sea states. Accordingly, in order to offer a real-time system of wave prediction in the case of multidirectional waves, we propose a simplified and succinct assimilation method for the process of wave reconstruction. We also develop a three-dimensional spatio-temporal prediction zone where the future evolution of wave fields can be estimated based on wave measurements. Lastly, we outline a tank-scale experimental campaign conducted to mimic the measurements of a LIDAR in a real configuration. A comparison of model performances with the experimental observations shows that in a multidirectional approach, it is necessary to consider wave components in direction as well as in frequency to achieve nearly the same accuracy as for unidirectional seas.

Due to the ever-increasing electricity demand, along with the need to reduce the dependence on fossil or nuclear resources, a growing amount of renewable energy is integrated in the energy mix of many countries. However, the cost-effective integration of wave energy remains difficult as its cost is still not competitive compared with other energy sources. This paper deals with the energy production management of a simulated wave energy converter farm based on point absorbers that could be installed in the vicinity of the SEM-REV site. The approach considers the electrothermal behaviour of the export cable in combination with techno-economic aspects. The method can be used to extend the power export capability of a test site at no cost, which could be very interesting to install more marine renewable energy (MRE) converters and/or of greater rated power. Our study shows that exploiting the thermal inertia of a wave farm submarine export cable, while also considering techno-economic aspects, may lead to an increase of 18% in the annual energy production without modifying this cable.