Investigating the impact of wind turbine rotor up-scaling on the viability of floating wind farms

Abstract

The technical viability of offshore wind projects depends upon a number of factors such as the site-specific wind resource, climatic conditions, sea depth, seabed composition and distance to the shore amongst others. The Mediterranean Sea with particular reference to the Maltese islands is characterised by deep seas relatively close to the shore. The wind climate offers less energy if compared to that of countries that are forerunners in the offshore wind sector due to the slower wind speeds. Floating wind turbine support structures will allow the development of wind farms in deeper waters. This will allow for a wider diffusion and larger-scale implementation of offshore wind farms on a global level. However such floating turbines are in an experimental phase and any existing structures are prototypes. This study investigates the prospects for a hypothetical 100 MW floating offshore wind farm on the western side of Malta. The study models a reference 126 m rotor diameter turbine and two up-scaled turbines having rotor diameters of 145 and 170 m. Simulations are performed to analyse the loads, displacements and other behavioural patterns during the operation of these turbines. These simulations along with calculations for the encountered stress determine that the up-scaled sizes are structurally stable and that their designs can be further improved. The study performs a levelised cost of energy (LCOE) analysis and shows that the rotor up-scaling process improves the economic viability of offshore wind turbines. This is because the improved energy yield offsets the higher investment costs required for such a project. This results in a lower LCOE for larger turbine sizes. This study hints that if the up-scaled sizes are improved as permitted by the stress analysis, the LCOE will further decrease as size increases.