Thermoelectric Energy Harvesting in Harsh Environments and Laser Additive Manufacturing for Thermoelectric and Electromagnetic Materials
| dc.contributor.author | Sun, Kan | en |
| dc.contributor.committeechair | Huxtable, Scott T. | en |
| dc.contributor.committeemember | Yu, Hang | en |
| dc.contributor.committeemember | Tafti, Danesh K. | en |
| dc.contributor.committeemember | Raeymaekers, Bart | en |
| dc.contributor.department | Mechanical Engineering | en |
| dc.date.accessioned | 2024-12-13T09:00:27Z | en |
| dc.date.available | 2024-12-13T09:00:27Z | en |
| dc.date.issued | 2024-12-12 | en |
| dc.description.abstract | This dissertation presents innovative research at the intersection of thermoelectric solutions, additive manufacturing, and nuclear safety technology, addressing critical challenges in sensor powering for extreme environments, energy harvesting, and materials fabrication. The research is divided into three key areas, each contributing to advancements in its respective domain. First, a self-powered wireless through-wall data communication system was developed for monitoring nuclear facilities, specifically spent fuel storage dry casks. These facilities require continuous monitoring of internal conditions, including temperature, pressure, radiation, and humidity, under harsh environments characterized by high temperatures and intense radiation without any penetration through their walls. The constructed system integrated four modules: an energy harvester with power management circuits, an ultrasound wireless communication system using high-temperature piezoelectric transducers, electronic circuits for sensing and data transmission, and radiation shielding for electronics. Experimental validation demonstrated that the system harvests over 40 mW of power from thermal flow, withstands gamma radiation exceeding 100 Mrad, and survives temperatures up to 195°C. The system, designed to operate stably for fifty years, enables data transmission every ten minutes, ensuring reliable long-term monitoring for nuclear safety and security. Second, the efficiency of thermoelectric generators (TEGs), unique solid-state devices for thermal-to-electrical energy conversion, was explored through a novel manufacturing approach using selective laser melting (SLM) and direct energy deposition (DED). Conventional TEG fabrication methods have limitations in achieving optimal efficiency due to design and material constraints. SLM-based additive manufacturing offers a scalable solution for creating geometry-flexible and functionally graded thermoelectric materials. This research developed a physical model to simulate the SLM and DED process for fabricating Mg2Si thermoelectric materials with Si doping. The model incorporates conservation equations and accounts for fluid flow driven by buoyancy forces and surface tension, enabling detailed analysis of process parameters such as laser scanning speed and power input. The results provided insights into temperature distribution, powder bed shrinkage, and molten pool dynamics, advancing the understanding and optimization of thermoelectric device fabrication using additive manufacturing. One step further, SLM and DED experiments were carried out to validate the simulation results and testify to the feasibility of applying laser powder bed fusion on semiconductor materials. Third, the research investigates the application of laser additive manufacturing to improve performance and reduce the production costs of magnetic materials. Soft magnetic materials, critical for various industrial applications, are fabricated using DED. The research optimizes DED printing parameters and processes through quality control experiments inspired by the Taguchi method and analysis of variance models. The resulting silicon-iron samples exhibit minimal defects and cracks, demonstrating the feasibility of the approach. Detailed optical and scanning electron microscopy, coupled with magnetic characterization, reveal that the rapid cooling process inherent to laser-based AM enables unique microstructures that enhance magnetic properties. Collectively, this work addresses pressing technological challenges in energy harvesting, materials fabrication, and extreme environment monitoring. The developed systems and methodologies have broad implications for nuclear safety, additive manufacturing, and the efficient utilization of advanced materials. By integrating interdisciplinary approaches and leveraging cutting-edge manufacturing technologies, this dissertation contributes to the advancement of sustainable and resilient solutions for modern engineering challenges. | en |
| dc.description.abstractgeneral | This dissertation explores groundbreaking advancements in energy solutions, manufacturing techniques, and nuclear safety, presenting technologies that address challenges in powering sensors, creating efficient energy harvesters, and developing advanced materials. The research spans three main areas, each providing innovative contributions to these critical fields. The first part focuses on a wireless system that powers itself and communicates data from inside sealed nuclear storage containers. These containers, used to store spent nuclear fuel, must be closely monitored for temperature, pressure, radiation, and humidity to ensure safety. However, traditional monitoring methods cannot penetrate the container walls and withstand the extreme conditions inside. This project developed a system combining four key components: a thermal energy harvester, an ultrasound-based communication method, durable electronic circuits, and radiation shielding. The system successfully harvests energy from the container's heat and uses it to power sensors and transmit data wirelessly every ten minutes. It is designed to operate reliably for fifty years, even under intense radiation and high temperatures, providing long-term solutions for nuclear safety monitoring. The second area investigates thermoelectric generators (TEGs), devices that convert heat into electricity. While TEGs have significant potential, traditional manufacturing techniques limit their efficiency and adaptability. By using cutting-edge laser-based additive manufacturing methods—Selective Laser Melting (SLM) and Direct Energy Deposition (DED)—this research developed new ways to create flexible and efficient thermoelectric materials. Advanced simulations were performed to model the manufacturing process, analyzing how factors like laser speed and power affect the final material properties. These models provided valuable insights into optimizing the process, which were then validated through experimental testing. The findings open the door to scalable and efficient production of thermoelectric devices for various energy applications. The third area addresses the fabrication of magnetic materials, essential for many industrial technologies. Traditional methods of creating magnetic materials can be expensive and prone to defects. This research applied laser-based additive manufacturing to produce soft magnetic materials, such as silicon iron, with fewer flaws and improved performance. By optimizing the printing parameters through experiments and statistical analysis, the team created materials with enhanced magnetic properties. Microscopic analysis revealed that the rapid cooling during manufacturing produced unique structures that contribute to the materials' superior qualities. These advancements have the potential to reduce costs and improve the efficiency of magnetic products in various industries. In summary, this dissertation tackles some of the most pressing challenges in energy, manufacturing, and safety technology. By developing systems that can monitor nuclear storage for decades, improving methods to harvest energy from heat, and creating better magnetic materials, this work paves the way for safer and more efficient solutions to modern engineering problems. These innovations are not only critical for nuclear safety but also hold promise for broader applications in sustainable energy and advanced manufacturing, contributing to a safer and more efficient future for industries worldwide. | en |
| dc.description.degree | Doctor of Philosophy | en |
| dc.format.medium | ETD | en |
| dc.identifier.other | vt_gsexam:42284 | en |
| dc.identifier.uri | https://hdl.handle.net/10919/123789 | en |
| dc.language.iso | en | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | Thermoelectric | en |
| dc.subject | Energy Harvesting | en |
| dc.subject | Laser Additive Manufacturing | en |
| dc.title | Thermoelectric Energy Harvesting in Harsh Environments and Laser Additive Manufacturing for Thermoelectric and Electromagnetic Materials | en |
| dc.type | Dissertation | en |
| thesis.degree.discipline | Mechanical Engineering | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |