Rashedul H Sarker

Feasibility study of thermal energy harvesting using lead free pyroelectrics

Energy harvesting has significant potential for applications in energizing wireless sensors and charging energy storage devices. To date, one of the most widely investigated materials for mechanical and thermal energy harvesting is lead zirconate titanate (PZT). However, lead has detrimental effects on the environment and on health. Hence, alternative materials are required for this purpose. In this paper, a lead free material, lithium niobate (LNB) is investigated as a potential material for pyroelectric energy harvesting. Although its theoretical pyroelectric properties are lower compared to PZT, it has better properties than other lead free alternatives such as ZnO. In addition, LNB has a high Curie temperature of about 1142 °C, which makes it applicable for high temperature energy harvesting, where other pyroelectric ceramics are not suitable. Herein, an energy harvesting and storage system composed of a single crystal LNB and a porous carbon-based super-capacitor was investigated. It is found that with controlled heating and cooling, a single wafer of LNB (75 mm diameter and 0.5 mm thickness) could generate 437.72 nW cm–3 of power and it could be used to charge a super-capacitor with a charging rate of 2.63 mV (h cm3)–1.

A Lithium Niobate High-Temperature Sensor for Energy System Applications

Temperature monitoring for energy generation systems plays an important role for the control of overall safety and efficiency. To run 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. Lithium niobate (LiNbO3) has high Curie temperature (1210 °C), thus making it promising to be used as a sensor material for high-temperature applications. In this paper, a study has been conducted to actively measure the temperature up to 450 °C using a pyroelectric ceramic LiNbO3 as a sensor material. A 1 cm × 1 cm sample of LiNbO3 ceramic with 0.2 cm thickness was prepared as a sensor. The LiNbO3 sensor and a K-type thermocouple were placed inside a tube furnace to sense the temperature. Different temperature setting conditions were applied to the sensor, including slow heating rate, high heating rate, and steady-state conditions for prolonged time period to validate readability and repeatability of the sensor. Temperatures were calculated using current generated from the sensor upon heating or cooling. The calculated temperature from the sensor was compared with the temperature measured by the K-type thermocouple. A range of deviation from 2% to 11% was found between the temperature measured by LiNbO3 and thermocouple.

Prediction of gas-solid bed hydrodynamics using an improved drag correlation for nonspherical particles

Gas–solid beds are ubiquitous in industrial and energy production applications. Examples include fluidized beds, which are used in many systems such as in integrated gasification combined cycle power plants or in chemical looping systems. These examples and others involve complicated interactions between each phase of reactants in the system. The motivation of this work stems from the need for a better understanding of bed hydrodynamics in existing energy systems; results from this work can be used directly in software such as Fluent to more accurately predict flow behaviors of gas and solid phases. The experimental data are collected from two setups including an optically accessible drag measurement facility that was used to obtain the drag coefficient at various particle Reynolds numbers and a lab-scale gas–solid packed bed which was used to validate the computational correlation through pressure drop measurements across the packed bed. Results showed that the new correlation predicted drag coefficients as accurate as 10% and deviated by up to 15% for particles with sphericities less than 0.9. This is a significant improvement compared to existing correlations, which can deviate as much as 50% for the same range of tested values. Similar findings are observed when the drag correlation is implemented into Fluent. It was found that the model predicted pressure drop in a particle bed with nonspherical particles with an error as low as 5% and as high as 28% near the fluidization velocity.

Characterization of the pyroelectric coefficient of a high-temperature sensor:

Temperature is one of the most important thermodynamic properties measured and controlled in energy generation systems. To operate the energy system at optimum operating conditions for lower emission and higher efficiency, it is important to measure real-time temperatures. Furthermore, temperature sensing in intense environments is necessary since most sensors in energy systems get exposed to elevated temperatures, corrosive environments, and elevated pressures. One of the solutions for developing harsh environment sensors is to use ceramic materials, especially functional ceramics such as pyroelectrics. Pyroelectric ceramics could be used to develop active sensors for both temperature and pressure due to their capabilities in coupling energy among mechanical, thermal, and electrical domains. In this study, Lithium niobate (LiNbO3) pyroelectric ceramic material was used to develop a temperature sensor for high-temperature applications. LiNbO3 has high Curie temperature (1210°C) compared to other pyroelectric ceramic materials. A high Curie temperature material is important since the polarization properties of the material break down above the Curie temperature. Hence, the use of a material with a higher Curie temperature, such as LiNbO3, makes it promising to be used as a sensing 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. Due to the non-linear pyroelectric response of LiNbO3, the temperature-dependent pyroelectric coefficient of LiNbO3 was measured with a dynamic pyroelectric coefficient technique in temperature ranges up to 500°C. Temperature-dependent pyroelectric coefficient of LiNbO3 was found to increase from −0.5 × 10−5 to −3.70 × 10−5 C/m2°C from room temperature to 500°C. The LiNbO3 sensor was then tested for higher temperature sensing at 220°C, 280°C, 410°C, and 500°C and has shown 4.31%, 2.1%, 0.4%, and 0.6% deviation, respectively, compared with thermocouple measurements.

Pyroelectric energy harvesting with a high Curie temperature material LiNbO3

Energy harvesting has been gaining significant interest as a potential solution for energizing next generation sensor and energy storage devices. The most widely investigated material for piezoelectric and pyro-electric energy harvesting to date is PZT (Lead Zirconate Titanate), owing to its good piezoelectric and pyro-electric properties. However, Lead is detrimental to human health and to the environment. Hence, alternative materials are required to be investigated for this purpose. In this paper, a lead free material Lithium Niobate (LNB) is reported as a potential material for pyro-electric energy harvesting. Although, it has lower pyro-electric properties than PZT, it has better properties than other lead free alternatives of PZT such as ZnO. In addition, LNB has a high curie point of 1142 °C, which makes it suitable for high temperature environment where other pyro-electric materials are not suitable. Therefore, a single crystal LNB has been investigated as a source of energy harvesting under alternative heating and cooling environment. A commercial 0.2 F super-capacitor was used as the energy storage device.

Testing of a new drag relationship for non-spherical particle geometries using the two fluid model

The present work presents the implementation of a newly developed drag model into computational code Fluent. The drag correlation previously developed is used to predict the behavior of a gas-solid packed bed computationally. For the comparison, bed pressure drop is plotted for different superficial velocities for three different particle sphericities 0.5, 0.65, and 0.9 and compared to experiments. The computational domain consisted of dimensions equal to the experimental setup. The experimental test facility was equipped with pressure, flow, and visualization measurement capabilities with dimensions of 12 cm diameter and 0.8m height. The newly developed drag model was implemented through the use of a userdefined-function in Fluent using the two-fluid model. Results showed that the maximum difference between computational and experimental values were 11.8% which is within experimental uncertainty. Hence implementation of this drag model may help researchers using the two-fluid model to more accurately predict hydrodynamic behaviors in a gas-solid packed bed.

Flow Field Visualization and Drag Analysis of Particles in a Gas-Solid Fluidized Bed

In this work particle flow behaviors inside a gas-solid fluidized bed were documented. Spherical and non-spherical particles measuring 1 mm and 0.85-1.18 mm, respectively, were used as test particles. Flow structure, particles size, particle velocity were measured with shadowgraphy a non-intrusive technology. Also presented in this work is a drag model for non-spherical particles expressed in terms of particle sphericity and Reynolds number. The drag model presented here is applicable to a range between 0.48 to 0.68.

Effect of particle density on the hydrodynamic behavior of a gas-solid fluidized bed

In this work the effect of particle density was analyzed using two different types of materials, Canadian Hematite and glass beads with densities of 4989 kg/m 3 and 2230 kg/m 3 , respectively. Both of these materials were used in a gas-solid bed and the hydrodynamic behavior of the bed analyzed. For each material two sets of particles were created. One set of particles ranged in size from 90 to 425 μm and another from 125 to 300 μm. The 90 to 425 μm particles were mixed maintaining a specific composition presented later in this paper. For the 125 to 300 μm range the same amount of particles were mixed according to the weight percentage of each size range. Pressure drop of the bed was taken using a differential manometer. For the Hematite particle size range of 90 to 425 μm the pressure drop measured across the bed at minimum fluidization was 785 Pa. For these same conditions using the glass beads the pressure drop was measured to be 420 Pa, significantly lower than those for Hematite. This same trend was also observed for the 125-300 μm particle range for the same bed height. Using the second set of particles pressure drop at minimum fluidization for Hematite and glass beads was 981 Pa and 412 Pa, respectively. Various other measurements taken at different bed heights showed that the Hematite pressure drop was significantly higher than when using glass beads. Other results presented in this paper show that both pressure drop and minimum fluidization are significantly impacted by the increase of the material density.