Thermoelectric phenomena

Thermoelectric effects refer to the direct energy conversion from thermal energy into electrical energy and vice versa. There are three important thermoelectric phenomena: Seebeck, Peltier, and Thomson effects. Seebeck effect refers the generation of electromotive force (emf) in a thermoelement by a temperature gradient. Peltier effect is a thermal current generation by an electrical current. The Peltier coefficient is a product of temperature and Seebeck coeffcient by Onsager's relation. At the interface between metal and thermoelectric semiconductor, the Seebeck coefficient drop cause the Peltier heat. And Thomson effect is a kind of continuous version of Peltier heat. In contrast to the irreversible Joule heat, the Thomson heat is reversible with electrical current direction.

Thermoelectric application

Transform ability between thermal and electrical energy can be applied to thermoelectric heat engine. While other electrical generators are using the magnetic flux change induced current generation, the thermoelectric power generator can induce DC current with direct energy conversion. Similarly, the inverse operation of heat engine leads to cooling device. In addition, it can be applicable to the special condition operation machine, such as radioisotope thermoelectric generator (RTG) for space mission.

Efficiency of thermoelectric conversion

By combining Seebeck-Peltier effects with eharge-energy conversation laws, we can derive the partial differential equation for thermoelectric effects. This equation has a very similar formula compared to heat equation. The only difference is that there are two major heat sources in thermoelectrics: one is reversible Thomson heat and the other is irreversible Joule heat. The exact temperature distribution can be obtained by solving this differential equation with proper thermal and electrical boundary conditions.

When we know the exact temperature distribution, the electrical and thermal currents are determined. Thus, we can finally compute the electrical power and thermal current, which are important for efficiency of thermoelectric conversion. Although thermoelectric figure of merit ZT has been widely accepted as a metric for thermoelectric performance of materials, counterintuitive examples have been reported that larger ZT can induced smaller efficiency. This finding highlight the importance of efficiency itself beyond ZT comparison. And, for real application, efficiency itself is important for device design.

WEB Thermo Electric Simulator (TES) (WEB TES), tes.keri.re.kr, web version of pykeri

Efficiency itself is the most important parameter for thermoelectric application. We have developed the python-based thermoelectric power simulator to compute the thermoelectric efficiency of materials and devices. For ideal 1-dimensional case where there is no heat loss by radiation and convection, the equation can be solved numerically and easily using our general theory of thermoelectric coversion: arXiv:1810.11148, arXiv:1910.11132.

Recently we develop and proudly launch a web simulator, "tes.keri.re.kr", where you can easily solve the temperature and compute the efficiency. As the web simulator is coded by java script, there is no personnel data issue. This website does not save any personel data. It compute the performances on your computer, not in our server, as the website is developed using javascript.

By copy-and-paste your data from the spread sheet, you can make continous functions for thermoelectric properties (TEPs) using our special interpolatoin algorithm (submitted and under revision).

With setting the electrical and thermal boundary conditions, we can set the thermoelectric heat equation. In the website we prepare Picard iteration method as an integral solver for thermoelectric heat equation, to obtain the exact numerical temperature. Then, the ideal power module performances are easily computed with high speed.

After simulation, one can copy one's efficiency result to paste and save it to the spread sheet (or excel).

Feature of WEB TES

• Web-based thermoelectric simulator for power generator, 1D without heat losses

• Very fast and accurate efficiency simulator

• Easy i/o for input and output data treatment: put material info -> draw TEP -> put device info -> run performance simuation -> get your output.

• No security issue regarding data save. You only need your own internet browser for computation

• Temperature dependent thermoelectric properties, beyond constant property model (CPM)

• Infinite dimensional recovery of TEP data using Chebyshev node sampling and Barycentric formula.

• Integral formula and Picard iteration for temperature solver as accelerated algorithm

• Thermoelectric electrical and thermal performance computations using leg geometry, thermal boundary condition.

• Power and efficiency as a function of current

• Detailed module analysis including electrical and thermal device parameters, average parameters for TEPs

Korea Electrotechnology Research Institute (KERI) is the government funded national institute working on Electro-Technology.

The thermoelectric team in KERI researches on the thermoelectric things from physics and science to engineering, from materials to devices, from phenomena to energy generation.