Research papers on design methods for offshore wind power monopile foundations in clay and sand seabed conditions detail new industry-specific guidance to model the interactions between monopiles and the soil. Field-testing validation of these bespoke methods suggests that previous approaches under-estimate the support that the seabed soil provides to the foundation, resulting in over-conservative design calculations for monopiles.
Estimates suggest that these more accurate methods have the potential to reduce steel requirements for foundations by up to 30 percent for some design conditions, realising significant cost savings. The new design methods are the outputs of the Pile Soil Analysis (PISA) project, a £ 3.5 million joint industry research project (JIP) led by Ørsted and run through the Carbon Trust’s Offshore Wind Accelerator programme. The Academic Working Group was led by Oxford University, and involved Imperial College London and University College Dublin.
Previous estimates for the behaviour of wind turbine foundations were based on offshore oil and gas platform design methods, where the foundation piles are smaller in diameter, longer and must resist different loading conditions during use. The new design methods specifically address larger diameter monopile geometries, as well as wind turbine loading conditions, to allow bespoke optimisation of turbine foundations and structures for specific geographic locations.
The field testing, which provided the validation data for the new design model, was undertaken in two locations with characteristics similar to those found in the North Sea; clay conditions in Cowden UK; sand conditions in Dunkirk France.