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Wind turbine systems are constructed using different types of generators, aero-mechanical components and control systems. Due to their ability to work in low speed, Axial Flux Permanent Magnet (AFPM) generators are becoming widespread in wind energy systems which contributes to eliminating the gearbox from the system, noticeable increase in efficiency and decrease in system weight. Due to the modular nature of the stator in AFPM generators, it is possible to control each module independently. In this paper, in addition to obtain the dynamic model of the turbine and AFPM generator, a control strategy is designed based on Mixed Integer Nonlinear Programming (MINLP) to incorporate both pitch angle and the number of active stator modules as control input signals. These control signals are used in order to maximize system efficiency and regulate output voltage in different wind speeds and electrical loads. Simulation results for a typical generator shows the effectiveness of the proposed method in speed control of the generator. • AFPMG's are becoming widespread in wind energy systems. • Modular structure AFPMGs makes it is possible to control each module independently. • Hybrid DVASMC/pitch-angle-control method is designed to regulate the voltage/speed. • Optimal Mixed Integer Nonlinear Programming control is shown to be efficient. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) is an efficient manufacturing method especially for ultra-high temperature ceramics (UHTCs) such as titanium carbides. Heating mechanism in SPS is a result of high electric current in the device including die, punch, and sample powder. Because the temperature distribution in the sintering process has considerable effect on the microstructure of the final sintered sample, in the present work, SPS of a cylindrical sample consist of a titanium carbide was investigated numerically. The governing equations of heat diffusion and electricity distribution in the whole device was solved using finite element method. In the heat diffusion equation, heat generation per volume was considered as a result of electric current in the device. Boundary conditions including radiation heat transfer and convective cooling by water flow were modelled by Stefan-boltzman and Newton cooling laws, respectively. The maximum temperature was observed at the center of the TiC sample. The radial temperature distribution in the sample showed considerable gradient as the minimum and maximum temperatures were 2000 °C and 1920 °C, respectively. Despite the radial direction, vertical temperature gradient was negligible in TiC sintering. Although the highest current density and consequent heat generation were observed at the die/punch interface with the minimum cross section, the maximum temperature of the whole apparatus was at the punch location. [ABSTRACT FROM AUTHOR]

• Proposing a novel SCPP connected to the building with vertical solar collector. • Analyzing experimentally and numerically with EnergyPlus and CFD softwares. • Using k − ε model for the 3-D CFD simulation. • Analyzing SCPP performance under various influencing factors. • Obtaining 705kW turbine's available power (4 times higher than at the Manzanares). The main challenge in designing solar chimney power plants (SCPPs) is to improve their performance by employing different techniques. This research aims to propose a new SCPP design for urban areas that can be installed on buildings, which is different from conventional SCPP conditions. The model was then analyzed experimentally and numerically (CFD and energy modeling) in order to prove its competency. For this study, ANSYS-fluent and EnergyPlus softwares were used and the case study building was the Energy Ministry of Iran. Seven parameters including air gap, thickness, slope, solar collector distance from the building's wall, chimney height, and diameter were selected for optimization to achieve maximum power outlet. A 1:50 scale of the building was also prepared for the experiment. The results indicated that increasing the height of the chimney leads to an increase in velocity. Additionally, each SCPP geometry has an optimal chimney diameter for its dimensions. It was also concluded that the operation of the system is affected by temperature and radiation, which causes higher power to be obtained in summers. The results showed that the power obtained from this power plant, which is on the same scale as the Manzanares power plant (absorber area, chimney height, and diameter), was approximately four times higher. The difference of this system compared to conventional systems is its completely vertical collector, which results in higher power with a lower chimney height. [ABSTRACT FROM AUTHOR]