Comparison of Foundation Systems for Wave Energy Converters Wavestar

In order to deliver cost competitive solutions, Wave Energy Converters (WEC) must be optimized in several fields, e.g. transportation, installation, structure, machinery etc. Large expenses lie on the superstructure support, i.e. the offshore foundation. Geotechnical analysis and optimization of six possible foundation solutions for WEC are presented in this article. The study is performed for WEC superstructure supported by two or four foundations. In the four-column system horizontal wind and wave loads are transformed as a pair of vertical forces, acting in tension and compression. When the overturning moment is large, it might be desirable to increase the width distance, achieving smaller vertical forces. For this reason, several distances between the supporting columns are investigated. Additionally, a two-column system is analysed as it is expected to be more cost effective. In such a solution horizontal wind and wave loads are dominant.

Gravity based, pile and bucket foundations are universally applied solutions for the offshore structures. The suitability of these types for a WEC is analysed and commented. The foundations are designed to satisfy ultimate and serviceability limit state requirements. For each of the foundation solutions, three geotechnical design steps are followed, employing analytical calculations, numerical 2D and 3D finite element programs.