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Mast structure is one of the most important parts of a vertical-axis wind turbine which supports generator and rotor and represents one-third of the overall costs in the production of a standard wind turbine (approximately 30%). All this may cause significant economic and physical losses when it is damaged or collapsed. The purpose of this research is to investigate numerically the static strength and structural dynamic responses of 10-kW vertical-axis wind turbine masts subjected to the aerodynamic and gravity loadings (according to the IEC 61400-2:2006 and EN 1991-1-4:2005 standards) using the SolidWorks finite element software. Mast structures with four different heights (12, 14, 16, and 18 m) and three various outer diameters (0.6, 0.7, and 0.8 m), in each height configuration, were evaluated. These analyses were performed to identify the stiffness, resistance, reliability, and natural frequency stiffness requirements within the mast structures, in order to save manufacturing cost. Based on static analysis, no structural failure is predicted for all masts during wind turbine operation according to maximum von Mises stresses at the bottom of the mast and maximum total deflections on the top of the mast. In addition, the dynamic parameters of these 12 models of masts have been studied to obtain the natural frequencies and corresponding mode shapes. Finally, the recommendations to avoid resonance and design strategy for each mast model are discussed. [ABSTRACT FROM AUTHOR]

Sun-tracking system (STS) is a key factor for solar photovoltaic (PV) future and new answers for the solar market. It will expand large-scale PV projects (PV farms) worldwide, and it is possible to collect more energy from the sun. PV farms consist of thousands of STS that are subject to dynamic loads (wind, snow, etc.), vibrations, and gravitational loads. This paper presents the structural dynamic analysis of a 24 m² bi-axial STS (azimuth-elevation) at different elevation angles based on its modal parameters (natural frequencies, modal shapes, and modal damping ratios) and dynamic performance indices (modal participation factors (MPF), forcing frequencies, and mechanical quality factors) by means of the finite element analysis (FEA). The simulation results show that the structural dynamic design of the STS meets the desired structural requirements and agrees well with structural dynamic standards (EN 1991-1-4 and ASHRAE). These results can be used for further analysis on optimal design and vibration safety verification for the bi-axial STS (PV applications). [ABSTRACT FROM AUTHOR]