Thermoelectric effect

High-performance thermoelectric materials lie at the heart of thermoelectrics, the simplest technology applicable to direct thermal-to-electrical energy conversion. In its recent 60-year history, the field of thermoelectric materials research has stalled several times, but each time it was rejuvenated by new paradigms. This article reviews several potentially paradigm-changing mechanisms enabled by defects, size effects, critical phenomena, anharmonicity, and the spin degree of freedom. These mechanisms decouple the otherwise adversely interdependent physical quantities toward higher material performance. We also briefly discuss a number of promising materials, advanced material synthesis and preparation techniques, and new opportunities. The renewable energy landscape will be reshaped if the current trend in thermoelectric materials research is sustained into the foreseeable future.

We demonstrate and discuss the performance of fully integrated and flexible micro thermoelectric generators (μTEGs). The devices are fabricated with a low-cost microfabrication process based on electrochemical deposition of a thermoelectric material into a polymer mold. Overall system optimization is demonstrated by means of NiCu and p- and n-type Bi2Te 3-based μTEGs. Influences of design, material, fabrication, and per- formance

As solar radiation is the most plentiful energy source on earth, thermoelectric energy harvesting emerges as an interesting solution for the Internet of Things (IoTs) in outdoor applications, particularly using semiconductor thermoelectric generators (TEGs) to power IoT devices. However, when a TEG is under solar radiation, the temperature gradient through TEG is minor, meaning that the TEG is useless. A method to keep a significant temperature gradient on a TEG is by using a solar absorber on one side for heating and a heat sink on the other side. In this paper, a compact TEG-based energy harvester that features a solar absorber based on a new class of solid matter, the so-called quasicrystal (QC), is presented. In addition, a water-cooled heat sink to improve the temperature gradient on the TEG is also proposed. The harvester is connected to a power management circuit that can provide an output voltage of 3 V and store up to 1.38 J in a supercapacitor per day. An experimental eval...

Spin caloritronics refers to generating spin current by thermal gradient. Spin caloritronics is an emerging new subfield of condensed matter physics concerned with coupled spin, charge, and energy transport in small structures and devices. In this paper, thermally induced spin transport in a magnetized zigzag graphene nanoribbon is explored. Using non-equilibrium Green’s function (NEGF) method in a tight-binding model, a temperature gradient applied between the left and right nonmagnetic electrodes, as thermal reservoirs in a magnetized zigzag graphene nanoribbon model junction so that the flowing of the up-spin and down-spin currents in the opposite directions can be induced which may be modulated by tuning of the back gate voltage. Furthermore, some thermoelectric properties of the junction, such as the spin-dependent Seebeck effect, electrical conductance, electron thermal conductance, and thermoelectric efficiency (ZT) of the model evaluated. Our calculations for the thermoelect...

ABSTRACT The effect of Ti substitution by Sc on the thermoelectric properties of the Heusler compounds NiTi0.3−xScxZr0.35Hf0.35Sn (where 0<x ≤ 0.05) was studied. The thermoelectric properties were investigated by measuring the electrical conductivity, Seebeck coefficient, and thermal conductivity. A reduction of the thermal conductivity by a factor of 2 was obtained by substitution of Ti by Sc. The pure compound NiTi0.3Zr0.35Hf0.35Sn showed n-type conductivity with a Seebeck coefficient of −288 μV/K at 350 K, while under Sc substitution the system switched to p-type behavior. A maximum Seebeck coefficient of +230 μV/K (350 K) was obtained by 4% Sc substitution, which is the highest value for p-type thermoelectric compounds based on Heusler alloys. The electronic structure was studied by photoelectron spectroscopy excited by hard x-ray synchrotron radiation. Massive in gap states are observed for the parent compound. This proves that the electronic states close to the Fermi energy play a key role on the behavior of the transport properties. Especially, they are responsible for the high, negative Seebeck coefficient of the parent compound.

High-temperature instability of the Ca3Co4−yO9+δ and CaMnO3−δ direct p-n junction causing the formation of Ca3Co2−xMnxO6 has motivated the investigation of the thermoelectric performance of this intermediate phase. Here, the thermoelectric properties comprising Seebeck coefficient, electrical conductivity, and thermal conductivity of Ca3Co2−xMnxO6 with x = 0.05, 0.2, 0.5, 0.75, and 1 are reported. Powders of the materials were synthesized by the solid-state method, followed by conventional sintering. The material Ca3CoMnO6 (x = 1) demonstrated a large positive Seebeck coefficient of 668 μV/K at 900 °C, but very low electrical conductivity. Materials with compositions with x < 1 had lower Seebeck coefficients and higher electrical conductivity, consistent with small polaron hopping with an activation energy for mobility of 44 ± 6 kJ/mol and where both the concentration and mobility of hole charge carriers were proportional to 1−x. The conductivity reached about 11 S·cm−1 at 900 °C...

The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice-versa. A thermoelectric device creates a voltage when temperature differ on side respect to next side. At the atomic scale, the temperature gradient causes charge carriers in the material to diffuse from the hot side to the cold side. In this case, electricity generated as a measure or change of the temperature difference of hot and cold sides of the thermoelement. The investigation involved using waste heat as input source. For this purpose, 72 bismuth telluride thermoelectric modules were used for energy conversion. The number of modules and their arrangement were delicate to select, where the power generated at the expense of temperature differences appeared between two sides of thermoelement. The 100 W generator was tested on chimneys, which outlet the hot gases to the atmosphere. Many of the design features, e.g. heat sink and fin designs were changed during this developme...