Dynamic modeling of a vertical axis wind turbine.

Offshore wind power is becoming a profitable way to produce vast quantities of electrical power because of the high availability of the resource and progressive decrease of the design and installation costs. The most widespread technology is nowadays bottom-fixed offshore turbines, but studies are being carried to go in deep water, where floating systems are needed. This causes unprecedented challenges in integrated system design, and still a definitive optimal configuration is not present. So different designs, also concerning the turbine, are being studied. One of them is vertical axis wind turbines, because of their lower centre of gravity and upscaling properties. The aim of this thesis is to model and simulate a vertical axis wind turbine system in onshore conditions, to determine its behaviour for a future integration on a floating system. To do that, initially a short review about vertical axis turbines technology was done, together with a comparison of aerodynamic models. Then, a steady-state aerodynamic model is built on MATLAB to find principal solicitations and machine performances. Many turbines were tested on this model, and then 2 of them were chosen to be studied more deeply. To do a proper dynamical simulation, also a control system on 2 variables (torque and pitch) was implemented to improve both performance and safety of the system. In the following chapters the aerodynamic code was validated, first against QBLADE, then, with a refinement, against literature data. Then the real model on SIMSCAPE Multibody was built, starting from obtained aerodynamic data and CAD models of the machines. With this model, a productivity analysis was done. This simulation was done in turbulent wind conditions in the location of Carloforte, in the southwest of Sardinia, and in a dedicated part simulation conditions were described. The choice of the location influenced the occurrence of the windspeed values, and so the productivity of the system. It was found to be lower than the one of standard wind turbines, but some of its features could be promising for open-sea deployment. In the end, some considerations were done about productivity and possible improvements of the model.