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Performance Analysis of Thermoelectric Generator by Using Lead Telluride, Perovskites, Skutterudites and Tetrahedrites

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Performance Analysis of Thermoelectric Generator by Using Lead Telluride, Perovskites, Skutterudites and Tetrahedrites WEENTECH Proceedings in Energy 5 (2019) 66-78 Page | 66 4th International Conference on Energy, Environment and Economics, ICEEE2019, 20-22 August 2019, Edinburgh Conference Centre, Heriot-Watt University, Edinburgh, EH14 4AS, United Kingdom Performance analysis of thermoelectric generator by using lead telluride, perovskites, skutterudites and tetrahedrites Pradyumn Manea*, Deepali Atheayab aEngineering Physics Department, School of Engineering and Applied Sciences, Bennett University, Tech Zone – II, Greater Noida 201310, UP, India bMechanical and Aerospace Engineering Department, School of Engineering and Applied Sciences, Bennett University, Tech Zone – II, Greater Noida 201310, UP, India *Corresponding author’s mail: [email protected] Abstract In this research paper performance analysis of thermoelectric generator by using lead telluride, perovskites, skutterudites and tetrahedrites has been proposed. The performance of thermoelectric materials and thermoelectric modules has been calculated. These thermoelectric materials were combined to make thermoelectric couple which will be used in thermoelectric generator. The performance analysis of these thermoelectric couples were simulated on COMSOL Multiphysics 5.2 software. The results indicated that Pb1-xMgxTe0.8Se0.2 and n-type PbTe, Pb1-xMgxTe0.8Se0.2 and CoSb3-xTe x, Pb1-xMgxTe0.8Se0.2 and CaMn0.98Nb0.02O3, Cu12Sb4S13 and CoSb3-xTex indicated higher efficiency than other thermoelectric couples. The proposed system can be utilized for varied range of applications for waste heat recovery and renewable power generation in automotive, industrial, power plants and space sector at an excellent efficiency and lower cost. Keywords: Seebeck effect; Lead telluride; Perovskites; Skutterudites; Tetrahedrites. Copyright © 2019 Published by WEENTECH Publishers. This is an open access article under the CC BY License (http://creativecommons.org/licenses/BY/4.0/). All Peer-review process under responsibility of the scientific committee of the 4th International Conference on Energy, Environment and Economics, ICEEE2019 https://doi.org/10.32438/WPE.7319 Manuscript History Receipt of completed manuscript: 09 April 2019 Receipt of Revised Manuscript: 10May 2019 Date of Acceptance: 20 August 2019 Online available from: 26 September 2019 Nomenclature V Voltage output. TC Temperature at the cold terminal. Page | 67 TH Temperature at the hot terminal. ΔT Temperature difference. T Average temperature. S Seebeck coefficient. Sp Seebeck coefficient of the p-type thermoelectric material. Sn Seebeck coefficient of the n-type thermoelectric material. ρp Specific resistance of the p-type thermoelectric material. ρn Specific resistance of the n-type thermoelectric material. σ Electrical conductivity. σp Electrical conductivity of p-type thermoelectric material. σp Electrical conductivity of n-type thermoelectric material. k Thermal conductivity. kp Thermal conductivity of p-type thermoelectric material. kn Thermal conductivity of n-type thermoelectric material. zT Figure of merit of a thermoelectric material. ZT Figure of merit of a thermoelectric module. η Performance efficiency. 1. Introduction The demand for energy is increasing day by day with increase in population. Also, burning fossil fuels is not a good option as it degrades the environment. Thus, an alternative and renewable sources need to be found out to satisfy the growing demands without harming the environment. One such alternative is thermoelectricity which converts thermal energy directly into electricity without any moving parts. The research on the thermoelectricity or thermoelectric effect is going since many decades and due to the development of nanotechnology, lot of progress has been made in this field. On an average the efficiency of thermoelectric generator is around 5% - 8% and lead telluride (PbTe), bismuth telluride (BiTe), calcium manganese oxide (Ca2Mn3O8) are few common materials used in making thermoelectric materials [1]. There are numerous applications of the thermoelectric effect, few examples are discussed. Thermoelectric effect could be used to recover waste heat and convert them in to electricity. Around 60% of energy is lost in a system, this energy could be utilized further to generate electricity with the help of thermoelectric generator [2]. In automobile this means, reduction of carbon emissions up-to 1.5 tones and saving 400 liters – 800 liters of fuel annually due to increase in fuel efficiency [3]. Thermoelectric effect can also be used in hybrid vehicles by storing electricity generated from the waste heat from the engine and the exhaust pipe into a storing unit like the battery and then using the stored electricity to ride the vehicle, thus, no need of recharging the battery [3]. Thermoelectric effect can also be used in thermal power plants to increase the power plant’s efficiency by 10%. This effect could also be used in military and space exploration [4]. A thermoelectric module comprising of many thermoelectric couples, weighs less than a battery and occupies 1/20th space of a solar cell. Thermoelectric generators are portable, has no moving parts, no maintenance and has longer lifespan. The following table compares Seebeck coefficient and electrical conductivity between metals, semiconductors and insulators. Page | 68 Table 1 Average values of thermoelectric parameters of metals, semiconductors and insulators at 300K [5]. Properties Metal Semiconductor Insulator S (μV/K) ~5 ~200 ~1000 σ (Siemen/m) ~108 ~105 ~10-10 From the Table 1, we see that insulators have highest Seebeck coefficient but lowest electrical conductivity, on other hand metal has Seebeck coefficient but highest electrical conductivity. Therefore, semiconductors could give the best performance and could prove themselves to be the best thermoelectric material. Use of nanotechnology in thermoelectric materials has scaled the performance of thermoelectric module. Using nanotechnology in thermoelectricity, it is possible to decouple the Seebeck coefficient, electrical conductivity and thermal conductivity, thus, improving the figure of merit (ZT) of thermoelectric module and increasing the performance of the thermoelectric module [6]. In this paper, we have also chosen thermoelectric materials which use nanotechnology to give greater performance. As per Chen [1] the commercial thermoelectric generators have efficiency between 5% - 8% which is far behind commercial engines and photovoltaic power systems. The research also claims that Cu-Sb-S compounds is one of the cheapest thermoelectric materials which could be manufactured. Alphabet energy released E1 in 2014 which uses Cu-Sb-S based thermoelectric compounds to get maximum efficiency and at lower cost. In 2013, Ma et al. [6] reviewed the then current status of the development of composite thermoelectric materials with embedded nanoparticles. They compared the bulk thermoelectric materials and thermoelectric materials composing nanoparticles by grouping the studies according to optimal temperature operational range. As per their research, most studies have been devoted to materials within the medium temperature range, followed by low temperature materials, whereas high temperature materials have not yet received much attention within this area [6]. Today there’s a need to find a perfect combinations of thermoelectric materials and thermoelectric modules to achieve maximum efficiency in an economically viable manner. Our research claims that with right combinations of thermoelectric materials, thermoelectric couples with 18% efficiency can be achieved. We have simulated our data in COMSOL Multiphysics 5.2 software and analyzed the performance of various thermoelectric modules and thermoelectric couples which could be used in thermoelectric generator. 2. Description of proposed thermoelectric material and thermoelectric couple So far, five thermoelectric materials and eight thermoelectric couples has been studied. The properties of five thermoelectric materials were already validated. These five thermoelectric materials were combined to make thermoelectric couple and then these thermoelectric couples were simulated. Out of five thermoelectric material the most prominent thermoelectric material which was observed is a quaternary alloy of Pb1-xMgxTe0.8Se0.2 with a figure of merit (zT) of 2.2 at a temperature (Tmax) of 800K. This quaternary alloy is a lead telluride (PbTe) based compound. Lead telluride (PbTe) and its alloys are well known for their high thermoelectric performance and has played an important role in deep space exploration. The Seebeck coefficient is about 260μV/K with electrical conductivity and thermal Page | 69 conductivity to be 4 x 104 S/m and 1 W/m K respectively [7]. Since the alloy has a positive Seebeck coefficient it’s a p-type thermoelectric material. Perovskites are a class of materials that has a similar structure like calcium titanium oxide (CaTiO3), which display a myriad of exciting properties like superconductivity, magnetoresistance and many more. The general chemical formula for Perovskites material is ABX3, where A and B are two cations of different sizes and X is an anion which bonds to A and B. The Perovskite structure is generally adopted by many oxides that have the chemical formula ABO3. One of the oxide based Perovskite material is CaMn0.98Nb0.02O3 which has a figure of merit (zT) of 0.2 at a temperature (Tmax) of 800K [8]. This Perovskite material has a Seebeck coefficient of -230μV/K with electrical conductivity and thermal conductivity to
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