Modeling and testing of functional materials for energy system applications
Energy efficiency is one of the key concerns addressing the problem of global warming. Numerous research has been going on in order to improve the efficiency of energy conversion systems to reduce the polluted emission in the atmosphere. One of the approach is monitoring and maintaining the critical parameters of operation such as temperature to ensure the desired reactions, however, the harsh environment present in these systems makes the use of current temperature sensing solutions such very challenging to implement. Wireless temperature sensors are getting increasing attention as a potential solution, however, the need of energy storage devices such as battery, capacitors limit their range of operation significantly. In this dissertation a passive wireless sensor based on the concept of metamaterials is proposed. The sensor consists of an array of metal circular ring resonators embedded in a ceramic dielectric matrix. Ansys Ansoft HFSS was used to conduct a feasibility study and design the sensor. To avoid complicated manufacturing technique, commercially available Cu washers were used as the metal structure and it was embedded inside a matrix containing 70% Boron Nitride and 30% Barium Titanate. The sensor performance is investigated as a function of temperature up to 200 °C and the effect of misalignment in the test setup, change in humidity in the environment and compressive strain on the sensor performance was also investigated. Another approach of increasing the efficiency of the energy system is to reduce the waste energy by harvesting and implementing that waste energy into producing electricity and significant amount of research is being carried out on energy harvesting using piezoelectric and pyroelectric effect. The most widely investigated material for this purpose is PZT (Lead Zirconate Titanate), which contains Lead, which has detrimental effect on human health and environment. Also, the low curie point of PZT and other common piezoelectric and pyroelectric materials makes them unsuitable for operation at high temperature environments such as energy conversion systems. In this dissertation a new material LiNbO 3 is investigated as an alternative source of PZT for pyroelectric energy harvesting. It was demonstrated that a single wafer of LiNbO3 can generate 437.72 nW/cm3 of power and can charge a supercapacitor of 0.2F capacitance. A newly developed supercapacitor containing Porous carbon-CeO 2 (PC-CON) hybrid electrode was charged using the material and the performance was compared to a commercial supercapacitor of similar capacitance. The newly developed PC-CON supercapacitor displayed faster charging rate than the commercial supercapacitor. It was also found that the amount of energy harvested can be increased by connecting several LiNbO3 wafers in parallel and also by choosing a diode that has low leakage current and faster switching capability.^
Karim, Hasanul, "Modeling and testing of functional materials for energy system applications" (2016). ETD Collection for University of Texas, El Paso. AAI10151413.