Piezoelectric elements are inevitable in modern day physics playing a vital role in many applications. Any piezoelectric element requires compression to produce energy in the form of a weak electrical ac signal. Mechanical vibrations are known to cause deflections which are enough to produce energy from the piezoelectric materials. In this paper, a review of the piezoelectric materials is made on their basic modes of excitation for producing energy. Also, various mechanisms and techniques used to harvest energy recently are presented and discussed extensively. Piezoelectric energy harvesting using MEMS is emphasized much as this is the era of micromechanical systems. Most of the piezoelectric energy harvesting systems relies on cantilever-oriented deflection to produce maximum vibration. In general cantilever beams fitted with piezoelectric materials produce electrical energy from mechanical vibration when deflected; hence detailed review on the different shapes of cantilever is also submitted. Significant parameters contributing to improved performance are dealt with special importance.
In order to study and investigate the overall performance of bio fluids for solar thermal applications, this work consists of integration of Taguchi method with Taguchi Grey Relational Analysis. The preparation of bio fluids has three levels of input control parameters such as Type of oil, Percentage of concentration and Stirrer speed. Output optimization indicators for the experiment were chosen as Thermal conductivity, Density and Viscosity. The comparative study made consists of coconut oil, sunflower oil and castor oil in the bio fluids preparation. These oils are available readily in the market and are quite inexpensive. The bio fluids are prepared by mixing the above oil with water in appropriate concentration. The experiment is run for the optimal solution using Taguchi analysis using L9 orthogonal array. The influential parameters which are significant in contributing the performance of bio fluids were studied using ANOVA table. After multi objective parametric optimization, the control parameters optimization level shows the use of Sunflower oil with 15% concentration at 15000 RPM stirrer speed produces the optimal performance. Based on the Ranking and Sum of squares from ANOVA table, it is evident that the most influential parameter is the type of oil followed by Percentage of concentration and Stirrer speed respectively.
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