This work presents a new and useful method to dimension wind turbines and control systems and to optimize their mechanical design. This method allows determining the principal curves for characterizing a small capacity wind turbine designed with a Permanent Magnet Synchronous Generator (PMSG). For the wind turbine characterization it was considered the losses in the process of energy transformation in the wind rotor, electric generator and in the bridge rectifier. The equivalent electric model of the synchronous generator was used to determine the electric parameter performance. The work of the wind rotor was considered in its maximum power curve and the PMSG performance in the linear region of its magnetization curve. This leads to develop a new methodology for the complete wind turbine characterization from the nominal parameters of the wind rotor and the electric generator. This method also allows obtaining the power curves and the parameters of voltage, current and efficiency around the wind speed domain and angular speed in the wind rotor. The method was tested for small-capacity wind turbine (1 kW and 10 kW) performances and the numerical and experimental results are described.
Irreversible losses and heat transport in a magnetohydrodynamic flow of a viscous, steady, incompressible, and fully developed couple stress Al 2 O 3-water nanofluid through a sloping permeable wall channel with porous medium and under the effect of radiation heat flux and slip were analyzed. The fundamental equations were solved numerically by using Runge-Kutta together with the shooting technique and the results were in qualitative agreement with an exact solution obtained for a limit case. The impacts of couple stress, Darcy number, solid nanoparticle concentrations, conduction-radiation parameter, Hartmann number and hydrodynamic slip on flow, temperature, heat transport, and entropy production were examined. It was possible to achieve values of minimum entropy production not yet reported in previous studies. In this way, optimal values of couple stress and slip were obtained. The heat transport was also explored and optimal values of slip flow and conduction-radiation parameter with maximum heat transfer were found. Finally, in addition to the alumina, the distributions of velocity, temperature, and entropy generation in TiO 2-water and Cu-water were presented for different solid nanoparticle concentrations. It was obtained that the local entropy of TiO 2-water was lower than Cu-water and Al 2 O 3-water in the channel bottom region while it was greater in the upper region.
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