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# Thermoelectric power generator

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### Thermoelectric power generator

1. 1. Thermoelectric Power generator From Vikram
2. 2. Introduction A thermoelectric power generator is a solid state device that provides direct energy conversion from thermal energy into electrical energy. •Principle of operation is “Seebeck Effect”.
3. 3. Seebeck Effect • Thermoelectric power generation is based on a phenomenon called “Seebeck effect” discovered by Thomas Seebeck in 1821. • When a temperature difference is established between the hot and cold junctions of two dissimilar materials (metals or semiconductors) a voltage is generated, i.e., Seebeck voltage.
4. 4. Q(h)= high temperature heat transfer T(h)=high temperature Q(l)=low temperature heat transfer T(l)=low temperature W(e)= output energy W(e)=Q(h)-Q(l)
5. 5. Specification •Sizes of conventional thermoelectric devices vary from 3 mm2 by 4 mm thick to 75 mm2 by 5 mm thick. •50 mm in length. •Height of modules vary from 1mm to 5mm. •Modules contain 3 to 127 thermocouples. •There are multistage thermoelectric modules of height 20 mm. • Below is a 3 stage module. • Schematic diagram showing components and arrangement of a typical single-stage thermoelectric power generator.
6. 6. Performance of Thermoelectric Power Generator Performance of thermoelectric materials can be expressed as: • Z= a^(2)/kr where, Z is thermoelectric material figure-of-merit a is Seebeck coefficient k is the total thermal conductivity R is the electric resistivity • ZT = a T / kR where, T=T(h)+T(l)/2 • Carnot efficiency n = 1- T(l)/T(h)
7. 7. Conversion efficiency as a function of temperature and module material figure-of-merit. With the increase in the value of T(h) conversion efficiency increases. But with the increase in the value of Z has an opposite effect on the conversion efficiency.
8. 8. Materials Used • Ceramic plates usually made from alumina. • Semiconductor thermoelements usually SiGe. • The hot and cold plates are usually connected using highly conductive material like copper. • Foe Power Generators these are further categorized as : Conventional and Novel
9. 9. Conventional Material • Alloys based on Bismuth (Bi) in combinations with Antimony (An), Tellurium (Te) or Selenium (Se) are referred to as low temperature materials and can be used at temperatures up to around 450K. • The intermediate temperature range - up to around 850K is the regime of materials based on alloys of Lead (Pb)
10. 10. • Thermoelements employed at the highest temperatures are fabricated from SiGe alloys and operate up to 1300K. • Although these materials provide a limited efficiency. • These are a cornerstone in practical and commercial application.
11. 11. New or Novel Materials • Promising candidate to fill the temperature range in the ZT spectrum between those based on Bi2Te3 and PbTe is the semiconductor compound ß-Zn4Sb3. • Possesses an exceptionally low thermal conductivity and exhibits a maximum ZT of 1.3 at a temperature of 670K.
12. 12. • Apart from this a thin thermo electric generator film made from semiconductors are also synthesized. • Their primary focus is not only on figure of merit (Z) but to improve thermal contact.
13. 13. Stirling Engine •A Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work. •Noted for its high efficiency compared to steam engines.
14. 14. Automotive thermoelectric generator • An automotive thermoelectric generator (ATEG) is a device that converts waste heat in an internal combustion engine (IC) into electricity. • The thermoelectric materials are made up of p-type and n-type semiconductors, while the heat exchangers are metal plates with high thermal conductivity.
15. 15. Layout Diagram showing the use of heat to convert it to electricity by Seebeck Effect.
16. 16. Industrial Waste Heat Applications • Most of the recent research activities on applications of thermoelectric power generation have been directed towards utilisation of industrial waste heat. • This can revolutionize the energy crisis as well as the environmental effects.
17. 17. Photograph of a thermoelectric power generator produced power for cathode protection of the well and gas line, which used the temperature difference between hot and cold legs of glycol natural gas dehydrator cycle.
18. 18. THANK YOU