Study Of The Blade Shape And Structure For V-shaped Vertical Axis Wind Turbine

The recent trend in the wind energy industry has revived the interest in the concept of vertical axis wind turbine with the increasing deployment of offshore wind farms.The VAWT designs don’t have benefits of forty years of intense research and development.Nevertheless,lessons can be learned from the development of horizontal axis wind turbines(HAWT)for the design of the VAWT.Vertical axis wind turbine(VAWT)may prove to be a suitable candidate for the offshore areas.This is mainly because of its simplicity in design and location of heavy and complex mechanical components near the water surface which will reduce the installation,operation and maintenance cost of the turbine.The study of a novel large-scale V-shaped VAWT was chosen as a probable candidate for the offshore area in the thesis.The major aims of this thesis are the aerodynamic design of the blade shape for the 2MW V-shaped vertical axis wind turbine and a conceptual design of the blade structure for the same blade.The research further includes a study of the various blade shape for a 100-W rotor having a similar appearance to the 2 MW rotor.In the end,the thesis aims to provide a methodology for the study of the fatigue life of a 2 MW V-shaped blade and also studies the fatigue life of the blade at a certain condition.A lower fidelity engineering model called Double Multiple Streamtube Model(DMST)is used for the initial design and estimation of the 2 MW V-shaped blade.The blade shape is studied for the different angles of inclination with the vertical axis,different chord length,and effect of different tapered blade.From the analysis of the results,a 90 m long blade inclined at 35-degree inclination with a vertical axis having a linearly tapered shape with the base chord length of 5m and the tip chord length of 2m was selected for the detailed study of the flow field in CFD.The 3D CFD simulation of the 3-bladed 2 MW rotor with the selected blade model is done at three different tip speed ratios(TSR).The highest Coefficient of Performance(Cp)of the rotor is found to be 0.44 at TSR 6.The CFD simulation of a similarly shaped blade for a 100 W rotor is done for comparison with the 2 MW blade model.The performance of two-blade is found to be completely different because of the different flow fields experienced by them.Apart from this,five different blade model is tested for the100 W rotor.The advantages of using a tapered blade are studied and verified from the CFD simulation.A conceptual design of the V-VWAT blade structure is proposed after performing the ultimate strength test of the blade according to IEC 61400-01 standard.The three different models of the blade structure are studied and a model is selected among them.The blade model is used for the study of the deformation and stress on the blade at eight different azimuthal positions under aerodynamic and gravitational load.In the end,a detailed methodology to study the fatigue life of the blade for V-VWAT is conceived.The fatigue life of the blade under fully reversed loading conditions using aerodynamic and gravitational forces on the blade is calculated.The fatigue life is found to be within a safe limit for an aluminum alloy blade under such conditions.