High Performance Dispenser Printed Thermoelectric Generators

Thermoelectric generators can potentially be used to generate electricity from this low-grade waste heat and play an important role in powering the condition monitoring sensors. This work presents a novel method to synthesize thermoelectric materials to print scalable thermoelectric generator (TEG) devices in a cost effective way. The main focus of this work is performance advancements of dispenser printed composite thermoelectric materials and devices. Thermoelectric device design for condition monitoring applications, novel composite thermoelectric materials and cost effective and scalable manufacturing methods are foundational aspects of this work.;WSNs are a promising technology for ubiquitous, active monitoring in residential, industrial and medical applications. A current bottleneck for widespread adoption of WSNs is the power supplies. While the power demands can be somewhat alleviated through novel electronics, any primary battery will have a finite lifetime. This can pose a major problem if the network is large or the nodes are located in difficult to reach areas. Battery replacement is thus undesirable, costly, and inefficient for large-scale deployments of WSNs. Thermal energy is an attractive option to power WSNs due to the availability of low-grade ambient waste heat sources.;TEGs provide solid-state energy by converting temperature differences into usable electricity. These solid-state TEGs have great appeal due to their silent nature, have no moving parts and are CO2 emission free. In order to be used for powering the condition monitoring WSNs, the TEG should be able to provide certain average power at desired voltage levels. Based on heat transfer TEG design, high voltage output requires large number of couples packed in a small area in addition to high Seebeck coefficient and high temperature difference across the device.;The performance of TEGs devices depends on both material properties and device geometry The efficiency of TEG is governed by the dimensionless figure of merit, ZT, which depends on material properties. It has been challenging to increase ZT beyond 1 for commercial thermoelectric materials like Bi 2Te3 as n-type and Bi0.5Sb1.5Te 3 as p-type, since the thermoelectric parameters of ZT are generally interdependent. There are challenges on the device design side as well. The electrical resistance and the temperature difference across the device depend on the element length of the device. Electrical resistance increases with increase in element length resulting in lower power output. Temperature difference across the device increases with increase in element length resulting in higher power output. Therefore, a trade-off occurs between device element length and power output, which ultimately depend on the TEG application. Therefore, an application specific optimized device length is required to maximize power output.;Devices, utilizing waste heat to generate power, should be low cost in order to be competitive. Traditional pick and place methods to manufacture TEG devices are labor, materials and energy intensive. Whereas, the micro-fabrication technology involves expensive and complicated processes like lithography and thin-film deposition and is limited to micro-scale regime. These methods have limited cost-effective scalability for manufacturing of application-specific TEGs. The limitations of the commonly used manufacturing technologies provide an opportunity for additive manufacturing methods such as direct-write printing. Printing utilizes additive processing steps, thus reducing materials waste and cost per unit area. It is an automated process that can be used to print high-aspect-ratio devices with minimum labor. (Abstract shortened by UMI.).