The Design And Properties Of Bi₂Te₃/CoSb₃Thermoelectric Generator With Wide Temperature Range

Thermoelectric generator is a new energy device which can be used to convert thermal energy into electrical energy or vice versa directly. The conversion efficiency of thermoelectric generator mainly depends on the thermoelectric materials. The best properties of a given thermoelectric material can be obtained only in a narrow temperature range. This is the reason that thermoelectric generators have low conversion efficiency. In this thesis, Bi2Te3(room temperature-200℃) and CoSb3(200-500℃) are used as research object, a Bi2Te3/CoSb3thermoelectric generator with wide temperature range has been designed with computer auxiliary design. Based on the principle of maxium power output and conversion efficiency of the new thermoelectric generator, the optimal length ratio of n-type and p-type thermoelectric materials with wide temperature range has been calculated. Three kinds of finite element modules of Bi2Te3, CoSb3and Bi2Te3/CoSb3thermoelectric generators have been developed. The performances of the module with the maximum efficiency in different geometrical structures and different conditions have been discussed. The main results are as follows:The best interface temperature, optimum length ratio, and maximum output power of n-type Bi2Te3/CoSb3thermoelectric materials with wide temperature range were investigated with the intersection method of the ZT curves. The results showed that the optimal interface temperature was550K; the optimal length ratio of o.3to Bao.4Ino.4Co4Sb12was equal to0.4352. The maximum output power was about2083mW/cm2under the load of0.0099Ω, the temperature Tc of cold side of300K, and the temperature Th of hot side of800K.The best interface temperature, optimum length ratio, and maximum output power of p-type Bi2Te3/CoSb3thermoelectric materials with wide temperature range were investigated with the intersection method of the ZT curves. The results showed that the optimal interface temperature was565K; the optimal length ratio of Bi0.48Sb1.52Te3to Ba0.3In0.3FeCo3Sb12was equal to0.4826. The maximum output power was about1053mW/cm2on the condition of the load of0.0232Ω, the temperature Tc of cold side of300K, and the temperature Th of hot side of800K. The performances of Bi2Te3, CoSb3, and Bi2Te3/CoSb3thermoelectric generators under different geometrical structures and different operation conditions have been investigated with finite element method to obtain the maxium conversion efficiency. The results showed that the optimal sizes of n-type and p-type legs of Bi2Te3thermoelectric generator are15x3x2.4mm3and15x3x3mm3respectively, the maximum conversion efficiency of the generator can reach5.7%. The optimal sizes of n-type and p-type legs of CoSb3thermoelectric generator are15x3x1.8mm3and15x3x3mm3respectively, the maximum conversion efficiency can reach5.0%. The optimal size of n-type leg of Bi2Te3/CoSb3thermoelectric generator is15x3x2.1mm3(the length of Bi2Te3is3.75mm, the length of transition layers is0.9mm and the length of CoSb3is10.35mm), and the optimal size of p-type leg of Bi2Te3/CoSb3thermoelectric generator is15x3x3mm3(the length of Bi2Te3is4.5mm, the length of transition layers is0.9mm and the length of CoSb3is9.6mm), the maximum conversion efficiency can reach8.2%. Compared to the Bi2Te3and CoSb3thermoelectric generators, the conversion efficiency of Bi2Te3/CoSb3thermoelectric generator increased by45.33%and by65.35%, respectively.