ACTIVE OPTIMAL CONTROL STRATEGIES FOR INCREASING THE EFFICIENCY OF PHOTOVOLTAIC CELLS

Energy consumption has increased drastically during the last century. Currently, the worldwide energy consumption is about 17.4 TW and is predicted to reach 25 TW by 2035. Solar energy has emerged as one of the potential renewable energy sources. Since its first physical recognition in 1887 by Adams and Day till nowadays, research in solar energy is continuously developing. This has lead to many achievements and milestones that introduced it as one of the most reliable and sustainable energy sources. Recently, the International Energy Agency declared that solar energy is predicted to be one of the major electricity production energy sources by 2035. Enhancing the efficiency and lifecycle of photovoltaic (PV) modules leads to significant cost reduction. Reducing the temperature of the PV module improves its efficiency and enhances its lifecycle. To better understand the PV module performance, it is important to study the interaction between the output power and the temperature. A model that is capable of predicting the PV module temperature and its effects on the output power considering the individual contribution of the solar spectrum wavelengths significantly advances the PV module designs toward higher efficiency. In this work, a thermoelectrical model is developed to predict the effects of the solar spectrum wavelengths on the PV module performance. The model is characterized and validated under real meteorological conditions where experimental temperature and output power of the PV module measurements are shown to agree with the predicted results. The model is used to validate the concept of active optical filtering. Since this model is wavelength-based, it is used to design an active optical filter for PV applications. Applying this filter to the PV module is expected to increase the output power of the module by filtering the spectrum wavelengths. The active filter performance is optimized, where different cutoff wavelengths are used to maximize the module output power. It is predicted that if the optimized active optical filter is applied to the PV module, the module efficiency is predicted to increase by about 1%. Different technologies are considered for physical implementation of the active optical filter

A numerical comparison of the flow behaviour in Friction Stir Welding (FSW) using unworn and worn tool geometries

The tool is a key component in the Friction Stir Welding (FSW) process, but the tool degrades and changes shape during use; however, only a limited number of experimental studies have been undertaken in order to understand the effect that worn tool geometry has on the material flow and resultant weld quality. In this study, a validated model of the FSW process is generated using the CFD software FLUENT, with this model then being used to assess the detail of the differences in the flow behaviour, mechanically affected zone (MAZ) size and strain rate distribution around the tool for both unworn and worn tool geometries. Comparisons are made at two different tool rotational speeds using a single weld traverse speed. The study shows that there are significant differences in the flow behaviour around and under the tool when the tool is worn. This modelling approach can therefore be used to improve understanding of the effective limits of tool life for welding, with a specific outcome of being able to predict and interpret the behaviour when using specific weld parameters and component geometry without the need for experimental trials