MS6.2 - Dynamic of marine energy systems

The widespread deployment of offshore wind turbines requires the use of fast, low-cost, and reliable installation methods. While impact pile driving is predominantly used for offshore monopile foundations, vibratory pile driving provides an interesting alternative. The selection of a suitable installation technique is based on cost, marine environment, noise pollution, and soil conditions. To study installation effects, this research aims to develop 1g laboratory scale tests of both impact and vibratory pile driving in a sand filled and saturated container. Numerical models are employed to study the dynamic behavior of the 1g scale test, allowing for a better understanding of the design of the test setup. Particular attention is related to the reflection of waves at the boundary of the container and the frequency content of the vibratory and impact driving force, as to get the best correspondence with the full-scale pile installation in situ. The numerical model includes (1) a multi-body dynamic model to compute the impact or vibratory loads on the pile head, and (2) a finite element model of the sand box – pile system. This allows us to study the dynamic interaction between the pile and the soil, wave propagation in the sand box, and estimate the soil’s response. Furthermore, a similar model is used for the full-scale size, where finite elements are coupled to perfectly matched layers to account for the unboundedness of the soil domain. The comparison of both scales is then used to optimize the test setup. A good correspondence to a full–scale test (both statically and dynamically) is obtained, allowing to upscale the 1g laboratory scale tests results.

Ocean wave energy has immense potential and can provide at least twice as much electricity as globally produced now due to its high energy density. In order to efficiently extract this energy and make this commercially viable, Wave Energy Converters (WECs) need to interact with the resource in an optimized way for the expanse of sea states. This interaction is critical to power production by these devices and hence an accurate modelling of this is paramount. The Boundary element method (BEM) based on the linear potential flow theory has yielded accurate results at low computational costs when compared to complex Computational Fluid Dynamics methods. Hydrodynamic Analysis of Marine Structures (HAMS) and Capytaine are recently developed open-source BEM frequency domain solvers, originally created for the hydrodynamic analysis of large marine structures. These solvers have since been utilized for studying wave energy converters, though, for very few converter geometries. Owing to the implementation of parallelization in both HAMS and Capytaine, both these solvers could be capable for significantly lower computational costs as compared to the traditional BEM solvers such as Nemoh. This research aims to compare hydrodynamic coefficients and computational costs in Nemoh, HAMS and Capytaine for various WEC geometries.

Climate change is expected to have an impact on wind patterns, and therefore the generation of waves. Phase 6 of the Coupled Model Intercomparison Project (CMIP6), provides various realization of outputs integrated global coupled models for different centuries. Wind quality is a cornerstone for wave energy as it is the primary generation driver in any wave model. Therefore, proper quantification of wind wave interactions is key in the evaluation of future wave energy potential. In this study, a wave hindcast for the North-East Atlantic, using the WaveWatchIII model forced by CMIP6 winds is presented. The model uses a grid of 0.25° of spatial resolution, covering a longitude range of -21.0° to 10° (west to east) and a latitude range of 18° to 80° (south to north). The main objective of this work is to assess the quality of historical winds from all the CMIP6 wind data that are available under the first realization criteria (r1i1p1f1) at the time of this study. This leads to understanding limitations and proposing a selection method to choose the optimal wind dataset to force the wave model within the analyzed area. Thus, the optimal CMIP6 historical winds for the North-East Atlantic are used to create a 10 years hindcast(from 2003 to 2012). To further assess the suitability of the selected winds dataset for wave generation, results are compared with the ERA5 wave product. The available CMIP6 models show region-specific variations depending on the Regional Climate models used for their developments. The results show the impact of zonal and, meridional wind intensities, on wave characteristics in different regions over the domain.