Thermoelectrics: From history, a window to the future

Abstract

Thermoelectricity offers a sustainable path to recover and convert waste heat into readily available electric energy, and has been studied for more than two centuries. From the controversy between Galvani and Volta on the Animal Electricity, dating back to the end of the XVIII century and anticipating Seebeck's observations, the understanding of the physical mechanisms evolved along with the development of the technology. In the XIX century Ørsted clarified some of the earliest observations of the thermoelectric phenomenon and proposed the first thermoelectric pile, while it was only after the studies on thermodynamics by Thomson, and Rayleigh's suggestion to exploit the Seebeck effect for power generation, that a diverse set of thermoelectric generators was developed.From such pioneering endeavors, technology evolved from massive, and sometimes unreliable, thermopiles to very reliable devices for sophisticated niche applications in the XX century, when Radioisotope Thermoelectric Generators for space missions and nuclear batteries for cardiac pacemakers were introduced. While some of the materials adopted to realize the first thermoelectric generators are still investigated nowadays, novel concepts and improved understanding of materials growth, processing, and characterization developed during the last 30 years has provided new avenues for the enhancement of the thermoelectric conversion efficiency, for example through nanostructuration, and favored the development of new classes of thermoelectric materials. With

Robust PEDOT:PSS Wet‐Spun Fibers for Thermoelectric Textiles

“…The thermoelectric efficacy of conjugated polymers tends to increase with σ until values of 10 2 –10 3 S cm −1 are reached, beyond which the thermal conductivity (κ) unduly increases. Overall, the thermoelectric figure‐of‐merit of a conjugated polymer, defined as ZT = α 2 σTκ −1 , where α is the Seebeck coefficient and T the absolute temperature, is likely optimized for the same range of electrical conductivities, and can reach a ZT ≈ 0.1 in case of p‐type organic materials 19…”

Inorganic thermoelectric materials: A review

“…In this work, they used Pb and Zn dopants to polycrystalline SnSe and formed Sn 0.98 Pb 0.01 Zn 0.01 Se and reported high ZT of 2.2 at 873 K . Owing to the hugely anisotropic transport properties of SnSe, single crystal SnSe presented the best TE performance at mid‐range temperatures . For instance, a very high ZT of 2.6 (at 923 K) with ultralow κ t and κ lat of ~0.35 and 0.23 Wm −1 K −1 , respectively, at 973 K was obtained by Zhao et al along the b ‐axis of orthorhombic unit cell in single crystal SnSe .…”

Thermoelectric harvesters and the internet of things: technological and economic drivers

“…Despite these limitations, over the last decade major improvements have been achieved in TEGs. Novel materials (or improved standard materials) have been reported having ZT values well in excess of 2 [10]. However, none of them has been yet qualified for production, and all of them reach anyway high ZT only at high temperatures.…”