Recognising the critical role that substructures play on the Levellised Cost of Energy, a dedicated session was held on Tuesday 10th March at EWEA Offshore that discussed various foundation solutions.
One of the session speakers was Dr. Azadeh Attari from engineering consultants, Gavin and Doherty Geosolutions (GDG), who presented preliminary results from the European Commission funded research project – LEANWIND.
This presentation specifically dealt with a parametric study into Gravity Based Foundations (GBFs) undertaken by GDG in collaboration with Acciona Infraestructuras, which investigated the impact of different geometrical and material parameters on the performance of GBFs over the various phases of construction, transport and installation.
GBFs are particularly attractive at wind farm sites with complex ground conditions such as shallow bedrock where monopiles may not be viable. Various limit states were considered in this study including geotechnical, structural and hydrodynamic failure modes.
The output of the investigation highlighted that GBFs designed for floatation during transport and installation were seen to be very sensitive to the ballasting operations. Furthermore, the initial draft needed to facilitate the initial floatation and load out of buoyant GBFs was shown to require very deep water which creates a major supply-chain bottleneck on port infrastructure due to the limited availability of deep water quaysides and docks.
The next phase of this study is to quantify the cost-benefit of both lifted and buoyant GBFs to determine the relative benefit of these solutions in different wind farm site conditions. Additional details can be obtained by contacting Dr. Azadeh Attari at GDG.