Screening of Available Tools for Dynamic Mooring Analysis of Wave Energy Converters

Jonas Thomsen,Jens Kofoed,Francesco Ferri

doi:10.3390/en10070853

Abstract

The focus on alternative energy sources has increased significantly throughout the last few decades, leading to a considerable development in the wave energy sector. In spite of this, the sector cannot yet be considered commercialized, and many challenges still exist, in which mooring of floating wave energy converters is included. Different methods for assessment and design of mooring systems have been described by now, covering simple quasi-static analysis and more advanced and sophisticated dynamic analysis. Design standards for mooring systems already exist, and new ones are being developed specifically forwave energy converter moorings, which results in other requirements to the chosen tools, since these often have been aimed at other offshore sectors. The present analysis assesses a number of relevant commercial software packages for full dynamic mooring analysis in order to highlight the advantages and drawbacks. The focus of the assessment is to ensure that the software packages are capable of fulfilling the requirements of modeling, as defined in design standards and thereby ensuring that the analysis can be used to get a certified mooring system. Based on the initial assessment, the two software packages DeepC and OrcaFlex are found to best suit the requirements. They are therefore used in a case study in order to evaluate motion and mooring load response, and the results are compared in order to provide guidelines for which software package to choose. In the present study, the OrcaFlex code was found to satisfy all requirements.

Highlights

There is a variety of environmental loads on offshore structures, dominated by loads arising from current, wind and wave, which contribute to the motions of the structure
The purpose of this study is to identify the requirements of the software tools for wave energy converters (WECs) mooring analysis when the main concern is to have a tool that allows for obtaining a certified mooring system
The comparison of software packages for mooring analysis illustrates that most of the existing software packages have the potential of fulfilling requirements defined in the design standards and thereby allowing for a certified mooring system

Summary

Introduction

There is a variety of environmental loads on offshore structures, dominated by loads arising from current, wind and wave, which contribute to the motions of the structure. These are vital for consideration when analyzing and designing floating structures, as it is necessary to control the motions in order to satisfy restrictions on the allowed excursion limit or to ensure the stability of the structure. The wave energy sector has many different concepts and devices for wave energy conversion; many of which are floating structures with the need for a mooring system [9]. The need for optimizing WEC moorings is significantly greater

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