Floating Vertical Axis Wind Turbines for offshore applications among potentialities and challenges: A review

Among the primary uses of Vertical Axis Wind Turbines (VAWTs) are small-scale applications, such as electricity generation in urban areas or isolated contexts, which are not grid-connected. However, a promising field of application for VAWTs to be investigated concerns floating offshore applications, where the more consolidated technologies based on HAWTs face significant challenges due to the harsh environment. The purpose of this study is to review the main floating VAWT concepts developed over the last few years and those currently under development, focusing on the projects and analysing the experimental prototypes and small-scale demonstrators. The main advantages of VAWTs compared to HAWTs are elaborated and presented: among the main ones is the more cost-effective maintenance due to the arrangement of the rotor nacelle assembly at the base of the VAWT, the increased static stability, which allows to reduce the mass of the floating foundation or to support a larger turbine, the reduced aerodynamic losses which allow turbines to be installed closer together and require a small installation area. A particular focus is made on the most urgent needs that demand to be addressed for the development of VAWTs, like the lack of experimental data and the installation of a multi-MW demonstrator to corroborate the technology reliability and challenges, such as the power upscale, the fatigue damage and mooring lines loads. Among the possible floating applications investigated is the energy supply for small isolated islands or offshore installations, like oil and gas platforms or fish farms.