Investigation On The Performance Characteristics Of Two Types Of The Thermoelectric Hybrid Power Generation Systems

In order to effectively use the waste heat of all kinds of grade and achieve thecascade utilization of energy, two types of models of the thermoelectric hybrid powergeneration systems consisting of the photovoltaic-thermoelectric generator hybridsystem and thermionic generator–thermoelectric generator hybrid system areestablished in the thesis, based on performance characteristics of the thermoelectricgenerator, photovoltaic solar cells, dye–sensitized solar cells, vacuum thermionicgenerator and photon–enhanced thermionic generator. The performancecharacteristics of the hybrid generation systems are investigated. The influences ofthe performance parameters on the optimal performance of the hybrid system areanalyzed. The optimal working region and optimal performance range are given. Theoptimal parameters of the hybrid system are obtained. All the results obtained in thisthesis will provide some theoretical basis for the optimal design and operation ofpractical hybrid energy system. The main research works of my master’s degreethesis included as follows.1． The theoretical model of a typical low concentrated photovoltaic(CPV)–thermoelectric generator(TEG) hybrid system is established. Based onnon–equilibrium thermodynamics and semiconductive theory, the expressions of thepower output and efficiency of the hybrid generation system are derived. Theinfluences of several important factors such as the thermal conductance between theCPV and the TEG, the current of the CPV, the solar irradiation, the concentratingratio and the figure of merit of the TEG on the power output of the hybrid device areanalyzed in detail. The optimum criteria of some important parameters are given. Thematched load electric resistances of the photovoltaic cell and thermoelectric generatorare determined optimally. It can be found that the low concentratedphotovoltaic–thermoelectric hybrid generator system can provide not only moreelectric power but also higher efficiency than a photovoltaic cell or thermoelectricgenerator. 2. A theoretically modeling approach consisting of a variety of irreversible loss ispresented which describes the performance characteristics of a dye–sensitized solarcells–thermoelectric generator hybrid system in steady-state operating conditional toanalyze potential critical problems as well as fundamental design characteristics.Expressions for the power output and efficiency of the hybrid power generator systemare derived by using the theory of non–equilibrium thermodynamics and the voltagecurrent characteristic equation of a dye–sensitized solar cell from an energetic pointof view. The optimally operating conditions of the hybrid system at the maximumoutput power and efficiency are determined. The optimal matched loads of thedye–sensitized solar cell and thermoelectric generator are obtained. The influence ofsome main performance parameters on the performance characteristics of the hybridsystem are discussed in detail. The performance characteristics of corporate andindependent driven load of the dye–sensitized solar cell and thermoelectric generatorare studied comparatively.The results show that the low grade waste heat of theDye–sensitized solar cell module can be effectively used by using the thermoelectricgenerator and the power output and efficiency of the hybrid system can be improved.3. The theoretical models of vacuum thermionic–thermoelectric hybridgenerating system those are powered by constant temperature heat source and solarenergy are established. The general expressions for the power output and efficiencyof two classes of the hybrid generating system are derived. The performancecharacteristics and optimal performance of the hybrid systems are investigated. Thecurves of the fundamental optimum relations of the hybrid systems are obtained. Theoptimal regions of some important parameters of the hybrid systems are determined.The influences of several main performance parameters of the hybrid systems onoptimal performance were discussed in detail. Some new significant conclusions wereobtained.4. The thermodynamic modeling approach of a photon enhancedthermionic–thermoelectric generator hybrid generating system is presented. Thegeneral expressions of the efficiency and power output of the hybrid system arederived. The performance and optimal performance of the hybrid system are studied. The effect of the load of the thermoelectric generator on the performancecharacteristics is analyzed.