Abstract
For decades research and development has been committed to improving the Figure of Merit (ZT) of Bismuth Telluride (Bi2Te3) Thermoelectric Generators (TEG) and has reached its limit at ≈1. This Meta-study aims to determine if further improvements can be made when the size of TEGs decrease. To quantify the change from macro to nano scale the change in ZT, thermal and electrical conductance, Seebeck coefficient and power factor as the size of the thermoelements decrease has been investigated as well as how Wiedemann-Franz (WF) law holds on the nanoscale. This meta-study was conducted by evaluating and comparing developments in TEGs for the past three decades. Based on theory it was expected that increases in ZT would occur as the thermoelement dimensions are reduced due to increased scattering of electrons and phonons as well as the increased density of electronic states. Increases to ZT due to these effects was not observed in experimental data due to difficulties in nanoscale production. This meta-study observed some indicators that the theory is correct in reduced thermal conduction from increased phonon and electron scattering and that phonon scattering was greater than electron scattering. Furthermore, a weak indication that WF law is not applicable on the nanoscale due to the scattering suggesting a decoupling of electrical and thermal conduction which is not achievable in macro scale TEGs
Highlights
Thermoelectric generators (TEGs) and Thermoelectric Coolers (TECs) are solid state devices that produce an electrical potential difference when a difference of temperature exists
TEGs operate on the Seebeck effect (Equation. 1) to generate electricity and TECs operate on the Peltier effect to create a temperature differential
By gathering experimental data from researchers that have manufactured nano and micro sized TEGs this meta-study determines whether experimental results agree with theoretical literature
Summary
Thermoelectric generators (TEGs) and Thermoelectric Coolers (TECs) are solid state devices that produce an electrical potential difference when a difference of temperature exists. 1) to generate electricity and TECs operate on the Peltier effect to create a temperature differential. The difference in temperature causes electrical current to flow, producing useful power. Due to the lack of moving parts, TEG’s have been seen as attractive options for energy retrieval in waste heat recovery, such as waste heat from electronics or life support systems [2]. RTG’s use a radioactive heat source, such as Plutonium238, and have been used in numerous deep space probes, such as the Voyager and Cassini missions, as viable collection of energy through solar panels is not feasible due to the vast distances from the probes to the sun. RTG’s have been used in terrestrial probes or rovers, such as the Curiosity Rover, as well as several experiments left on the Moon by the Apollo missions
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