Offshore turbines in coastal areas are a promising method for the production of clean energy due to greater wind potential than land based turbines. They also avoid the problems associated with deeper installations in the open sea, such as difficult access, expensive maintenance and the extensive lengths of cabling required. Shallow water installations, however, have their own challenges, such as breaking wave trains at decreasing depths. This involves a series of waves that travel in the same direction, spaced at regular intervals, which can threaten the integrity of the pillars supporting the turbines. The main aim of the project SAFEMILLS (Increasing safety of offshore wind turbines operation: Study of the violent wave loads) was therefore to find a solution to the problem of steep waves slamming onto vertical wind turbine pillars. Researchers used an approach based on three-dimensional (3D) waves that could accommodate at a later stage the von Karman and Wagner approaches for wave impact. This enabled time varying components of loading, including force and pressure impulse, to be derived and used to achieve a solution based on elliptical cylinders. SAFEMILLS results will help find alternative structural bases for offshore wind turbines. These include truss type structures, which have the advantage of lower construction costs, easier removal, repair and maintenance, plus increased safety. The project’s findings will also benefit research into hydrodynamic slamming problems, violent wave impact, and the hydroelasticity of ships and offshore structures.
SAFEMILLS, wind turbine pillars, wave loads, 3D waves, elliptical cylinders