چكيده به لاتين
Energy and environmental crises during recent years have made it inevitable to move towards clean, renewable and sustainable energies in different scales, dimensions, and applications. In small scales, sustainable, clean and repair and maintenance free systems are required to supply the energy required for systems at smaller scales like micro electro mechanical systems (MEMS), nano electro-mechanical systems (NEMS), implantable medical equipment, mobile electronic equipment, nano-robots and etc. At the moment, batteries are the most common equipment to supply the energy required by these systems. Major problems of batteries include limited life, accessibility, big sizes and high weights (in comparison to the whole system) and environmental disposal problems. The invention of nano-generator can be considered as an answer to these problems. Nano-generator takes advantage of piezoelectric property in specific materials to extract energy from the environment. These new energy resources make use of mechanical vibrations in the environment, mechanical tensions, fluid flow (e.g. blood), and temperature difference and so on to supply the energy required by the target systems up to nano scales. This thesis seeks the analysis and investigation of mechanical, electrical and thermal effects in piezoelectric nano-generators. To this end, piezo-thermoelastic equations will be extracted using Hamilton’s principle and the Modified Couple Stress theory by modeling and simulating of nano-generator components. The Modified Couple Stress theory is a non-classical continuum mechanics theory which includes one length scale material parameter, so it can predict more accurate results for micro and nano systems. GDQ method was applied to solve the governing equations. Next, effective parameters on output voltage such as the excitation frequency, temperature gradient, damping ratio and length scale parameter were studied and finally, the optimal size range of nanowire’s length and size width were suggested to reach the maximum voltage. This research could be considered as a valuable tool for analyzing the PENGs in order to enhance the output voltage and design these novel energy harvesting systems easier and with lower cost.
