Investigation on pyroelectric ceramic temperature sensors for energy system applications
Temperature monitoring for energy generation systems plays an important role for control of overall safety and efficiency. To operate the energy system at optimum operating conditions, it is important to measure the real time temperature. Furthermore, harsh environment temperature sensing is desired since most sensors in energy systems are exposed to high temperature, high pressure, and corrosive environments. There is an increasing demand of wireless sensor networks and major interest in energy system applications for harsh environment and remote sensing applications. For this study, LiNbO3 and Pb(Zr0.52Ti0.48)O3 (PZT) pyroelectric ceramic materials were used to develop temperature with wired and wireless connection respectively. Lithium niobate (LiNbO3) has high Curie temperature (1210 °C), thus making it promising to be use as a sensor material for high temperature applications. A study was performed to actively measure the temperature up to 500 °C using a pyroelectric ceramic lithium niobate (LiNbO3) as a sensor material. Different operating conditions were applied to the LiNbO3 sample sensor including cyclic heating and cooling, low rate of temperature change, high rate of temperature change at low temperature ranges (<100 >°C). For cyclic heating and cooling 2 mm and 1 mm thick LiNbO3 sensors have shown 8 % and 6.7 % deviation respectively. For low and high rate of temperature changes with time, the LiNbO3 sensor measured the temperature with 2% and 4% deviation, respectively. The LiNbO3 sensor was also tested at high temperatures. Before high temperature measurement testing, the temperature dependent pyroelectric coefficient of LiNbO3 was measured with a dynamic pyroelectric coefficient technique for different temperature ranges up to 500 °C. Temperature dependent pyroelectric coefficient of LiNbO3 was found to be between -8.5 x 10-5 C/m2 °C and -23.7 x 10-5 C/m2°C from room temperature to 500 °C. The LiNbO3 sample sensor was then tested for higher temperatures and measured the temperature up to 220 °C, 280 °C, 410 °C and 500 °C with 4.31 %, 2.1 %, 0.4 % and 0.6% deviation, respectively. For developing a wireless temperature sensor, PZT ceramic material was used to measure the temperature for its higher signal strength with higher pyroelectric coefficient compare to LiNbO3. An electromagnet was built with a pre-designed number of loops of wire, length, inner radius and outer radius. PZT sample was placed on top of a hot plate and it experienced maximum 0.84 °C/s rate of temperature change with time and maximum 4.59 µA current was generated by the PZT due this corresponding rate of temperature change with time. Current from the PZT was supplied to the electromagnet to generate a magnetic field. Before using the PZT sample as a sensor, the electromagnet was characterized by measuring the magnetic field with a gaussmeter from different positions of the electromagnet including at the center, at the edge, at 1.27 cm, and 1.54 cm apart from the edge of the electromagnet along its axis. The gaussmeter was able to detect the magnetic field at the center, at the edge, at 1.24 cm, and 1.54 cm apart from the edge of the electromagnet with 11 %, 0.4 %, 11 %, and 0.9 % deviation, respectively. A nickel/iron/molybdenum alloy core material was also placed inside of the electromagnet to intensify the magnetic field strength by the factor of magnetic permeability of the core material. Gaussmeter measured the magnetic field 1.54 cm apart from the edge of the electromagnet along its axis with and without core material inside of the electromagnet. It was found that the electromagnet with core material intensified the magnetic field by a factor of two compared to the electromagnet without the core material. It was also found that the core material was experiencing induced magnetic field after removing current flow through the electromagnet. As the magnetic field was used to calculate the temperature of the PZT, the induced magnetic field on the core material was not desirable. After characterizing the magnetic field detection, the PZT sample and electromagnet without core material were prepared to measure the temperature wirelessly. For the wireless temperature measurement, two different temperatures (100 °C and 120 °C) were applied to the PZT ceramic material by placing it on top of a hot plate. The generated current was measured using a picoammeter and the generated magnetic field from the electromagnet was measured with a gaussmeter probe at 0.254 cm apart from the edge of the electromagnet. For two operating conditions (100 °C and 120 °C), the PZT sample was able to measure the temperature wirelessly with maximum 7.5 % and 4.3 % deviation from the theoretical temperature, respectively.^
Sarker, Rashedul Hasan MD., "Investigation on pyroelectric ceramic temperature sensors for energy system applications" (2016). ETD Collection for University of Texas, El Paso. AAI10252774.