Abstract

In this paper, we determine optimum layouts of a cluster of oblate spheroidal heaving point absorbers in front of a wall, that maximize the annual averaged power absorbed by the cluster, while satisfying specific spatial constraints. An iterative optimization process is developed by coupling a hydrodynamic model with a genetic algorithms solver. Optimization is performed for three near-shore sites in the Aegean Sea, Greece. Optimum layouts are obtained considering part of or the whole wall length, available for the PAs' sitting. The effect of the incident wave direction on the optimum layouts' formation and the absorbed power is also assessed. Finally, the dependence of the maximized absorbed power upon the deployment site is illustrated.

Introduction

Contemporary technological advances seek the efficient exploitation of the vast wave energy potential. Accordingly, the technology of Wave Energy Converters (WECs) is continuously being developed during the past years, aiming at delivering commercially competitive solutions that maximize efficiency, ensure survivability, reduce costs and minimize environmental impacts. Heaving type Point Absorbers (PAs) correspond to one of the most technologically advanced type of WECs, characterized by the "one-mode" operation simplicity. Some characteristic examples of PAs are the Wavestar (Hansen et al., 2013) and the Seabased AB (Chatzigiannakou et al., 2017). In order to absorb an adequate amount of power and, thus, contribute to the reduction of the high Levelized Cost of Electricity (LCoE), representing currently one of the main drawbacks of WECs (Rusu and Onea, 2018), multiple PAs in the form of clusters (arrays) can be deployed (e.g., Stratigaki et al., 2014; Balitsky et al., 2018).

Alternatively to offshore marine areas, PAs clusters can be also deployed at near-shore locations. In those cases, coastal structures, such as vertical (wall-type) breakwaters, occupying a large ocean space, may exist, while the relevant asset owners and operators may seek for additional integrated alternative uses of the existing marine facilities. Within this context, clusters of PAs can be deployed in the seaward side of wall-type breakwaters facilitating the exploitation of both the incident waves and the waves reflected from the wall. This idea falls within the wider approach of integrating WEC technologies with coastal structures (e.g., Zhao et al., 2019; Rosa-Santos et al., 2019; Vicinanza et al., 2012; Michailides and Angelides, 2015) and it can support the realization of cost-efficient solutions through costs sharing.

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