Design of Thermoelectric Coolers and Transverse Thermoelectric Generators for Performance Enhancement

Abstract

This dissertation presents successful examples of designing novel thermoelectric devices to enhance output performance. Specifically, it focuses on designing and proposing new concepts of thermoelectric coolers and transverse thermoelectric generators. The first part, for chapters 2 and 3, focuses on developing next-generation thermoelectric coolers for heat dissipation. Chapter 2 presents a stretchable thermoelectric cooler's fabrication process and performance optimization to dissipate heat effectively. The cooling capability of the stretchable thermoelectric devices is confirmed under both conductive and convective heat load conditions. Chapter 3 shows the adaptive thermoelectric cooling system for local and transient heat management. The adaptive thermoelectric cooling system demonstrates fast cooling and effectively maintains the system temperature below the target temperature. Numerical analysis verifies that the adaptive thermoelectric cooling system offers exclusive cooling on hot spots, preventing overcooling in other regimes, which makes it consume 47% less power than a conventional thermoelectric cooling system. In the second part, for chapters 4 and 5, the design of novel transverse thermoelectric generators is proposed to enhance its output voltage significantly. Chapter 4 demonstrates that a novel device design employing a shape-engineered tilted-leg thermopile structure significantly enhances the output voltage in the transverse direction. Owing to the shape engineering of the leg geometry, an additional temperature gradient develops along the direction perpendicular to that of the applied heat flux, generating an additional output voltage. In addition, numerical analysis shows the tendencies of the electrical and thermal outputs of the tilted-leg device, which guides a way to further improve the output voltage. Chapter 5 shows a planar coil device that could maximize the output voltage by increasing the total length of the material within the device. It is rolled up into a coil structure to maximize the total length efficiently and achieve high heat flux sensitivity. Compared to the conventional thermopile thermoelectric heat flux sensors, the proposed structure can reduce the number of electrodes to decrease contact resistance and simplify fabrication. Our study in this thesis introduces the design of novel thermoelectric devices to improve their output performance and functionalities. These insights significantly contribute to fabricating new designs for broader thermoelectric applications. Examples of such applications include next-generation cooling platforms or wearable sensors.