UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2022-07-01 16:43

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Conference: Bucharest University Faculty of Physics 2019 Meeting


Section: Physics and Technology of Renewable and Alternative Energy Sources


Title:
Thermoelectric Efficiency and Power enhancement of Sodium Cobaltite for future Industrial Applications


Authors:
Esmaeil JALALI LAVASANI(1,2), George Z─éRNESCU(2), Ioan STAMATIN(1,2), Robert ILIE(1)


*
Affiliation:
1) University of Bucharest, Faculty of Physics, PO Box MG 38, 077125, Bucharest-Magurele, Romania


2)University of Bucharest, Faculty of Physics, 3NanoSAE Research Center, PO Box MG 38, 077125, Bucharest

-Magurele, Romania



E-mail
gzarnescu@gmail.com, esmaeil.jalali@3nanosae.org


Keywords:
Seebeck coefficient, thermomagnetic effect, power and efficiency


Abstract:
In this paper we present a theoretical and experimental approach on how to maximize NaxCoO2 Seebeck coefficient and also the total efficiency of the p type thermoelectric leg, by doping with Na up to 2%. By increasing the sodium content we have observed also a dramatical decrease of the current. In order to compare the current and resistance for a usable geometry we have made two cylinders (or discs) one of 30mm diameter, 2.5mm thickness and the second one 10mm diameter and 10mm thickness. The Seebeck coefficient was increased to an incredible value of 4000 uV/K, only at a temperature of 480 K, this fact can be explained also theoretically because Seebeck coefficient has a logarithmic growth with conductivity and also with the increasing numbers of electrons (10^19 optimum) and electron carriers inside the material. For the current, because the sample is also magnetic due to the Cobalt structure, we have managed to increase it by almost ten times from 3uA to 30uA by placing the 30mm disc between two NeFeB strong disc magnets (0.9 T average magnetic field), but after we remove the magnets the effect disappears in maximum 20 minutes. This thermomagnetic effect or Nernst effect applied to the electrons can greatly improve the power generated by sodium cobaltites. While the number of electrons is increasing, due to the Hall Effect, magnetoresistance will have a large negative slope. We also have observed that there is a reversible potential of +-0.17-0.2V between the aluminum plates that can't be attributed to any thermoelectric effect because the temperature gradient was maximum 1 degree Celsius.


Acknowledgement:
This work was done also with the help of Project No. 143, "Body energy harvesting for backup power supplies" financed by Romanian Space Agency (ROSA)