Oxide-based High Temperature Thermoelectric Generators - Development of Integrated Design Technique and Construction of a Thermoelectric Module

In the field of energy management, thermoelectrics are niche candidates for electrical generator devices. For decades, scientists have been focused on thermoelectric (TE) material development. Thus TE module design techniques are still in relatively virgin state when comparing to the TE material development. This thesis is focused on development and optimization of thermoelectric generator (TEG) design techniques for high temperature (> 700 °C) applications. Some of the main targets of this optimization process are to achieve higher volumetric power density (VPD), and reduce the cost-per-Watt. Oxide based TE materials were used as the core of the TEG due to the focus on high temperature applications and the requirement that the TE materials should be stable at those temperatures. However, p- and n-type oxide TE materials do not perform ( values) at the same level and it is one of the major challenges identified in this project. Thus, the proposed TEG optimizations should address this challenge in an appropriate manner. The work has established a new TEG optimization strategy based on the existing well-known TEG design technique Reduced Current Approach (RCA). This extended version of RCA is able to produce TEGs with higher VPD, compared to RCA, when the p- and n-leg of the TEG has difference performance levels ( value) and thus the cost-per-Watt of the TEG can be reduced. Furthermore, the PhD project introduces the Unileg-TEG (U-TEG) concept for the oxide TEGs to address the issues of the thermoelectrically mismatched materials. U-TEG removed the weaker TE material and replaced it with a conductor. It is shown that U-TEG is a valuable concept to increase the VPD of a TE device that has mismatched TE materials. Moreover, U-TEG design is generalized using an idealized metal. Furthermore, well-known Ioffe’s method and RCA are compared using the temperature independent TE properties. This comparison opens up a new strategy to reduce the cost-per-Watt of the TEG, by increasing the dominancy of the cheaper TE material in a TEG design. In addition, the work has introduced an engineering approach for complex TEG designing technique RCA, to define the TEG architecture in a simple and time saving manner.