Study On The Effect And Inverse Optimization Of Thermoelectric Material Physical Properties On The Generation Device

Because of global warming,how to quickly peak carbon emissions has become the primary task of all countries in the world.At present,China’s industrial energy consumption accounts for a large proportion,but industrial energy efficiency is not high,resulting in a large amount of energy waste.How to effectively use this part of the energy is an urgent problem to be solved.Thermoelectric generators（TEGs）have the advantages of environmentally friendly,safe,noiseless,and long life.It can be used to recover low-quality heat sources.Thus,using TEG to recover industrial waste heat,thereby improving industrial energy efficiency,is a good choice.However,the current low power generation efficiency of TEG hinders its application.Although many thermoelectric（TE）materials with a high figure of merit（ZT）have emerged,the actual device efficiency is still not ideal.This is because TE material with a high ZT cannot guarantee that associated TEG has an optimal performance in practical conditions,so the real effect of TE material properties on device performance is not clear.In addition,when the TE materials are fabricated into TEGs,the interface effect between the materials will also lead to further deterioration of TEG performance.These factors eventually lead to the performance mismatch between materials and devices.Therefore,exploring the influence of TE materials’physical properties and interfacial effects on TEG performance by coupling the material and device to guide the optimization of the TE materials from the practical application of TEG,which is of great guiding significance to promote the rapid development of TEGs.This thesis aims to analyze the influence of critical physical properties of TE materials and interfacial effects on the power generation performance of the TEG from the perspective of the device and the practical application to find the optimization strategy of TE materials for conventional TEGs and micro TEGs.Firstly,considering the effect of the effective temperature gradient of TE leg,contact effect,boundary effect,optimal matching load and the second type of thermal boundary conditions,a mathematical model for calculating the power generation performance of conventional TEGs and micro TEGs through the physical properties of TE materials was established,and the models were also verified.Then,the effects of interface effect and ZT value of TE materials on the generation performance of conventional TEGs and micro TEGs were analyzed by using the above mathematical models.The results have shown that the interfacial effect has little effect on the performance of conventional TEGs,but has a great influence on the performance of micro TEGs.The interfacial effect becomes more and more significant as the height of the TE leg of the micro TEGs decreases.When the height of the TE leg is less than 7.5μm,the interfacial effect will make the performance of the micro TEGs degrade by more than 50%.Among them,the influence of the contact effect on the micro TEGs performance is greater than the boundary effect.When the contact resistance and contact thermal resistance are reduced to 10^-11Ω·m²and 10^-7 K·m²/W,the influence of the contact effect can be ignored.Moreover,the ZT value of the TE material cannot accurately reflect the power generation performance of the device.At present,the improvement of the ZT value of the material to optimize the performance of the device is relatively limited.When the ZT value of TE materials is increased from 1.5 to2.5,that is,an increase of 66.7%,the power generation performance of conventional TEGs and micro TEGs is only increased by 22.5%and 40.5%,respectively.Nest,referring to the local sensitivity analysis model,an inverse optimization mathematical model was proposed to guide the TE material development based on the device performance and used to analyze the importance of the key physical properties,i.e.,Seebeck coefficient,phonon thermal conductivity and electrical conductivity,to the device performance,thus pointing out the optimization direction of TE materials.For TE materials for conventional TEGs,increasing the Seebeck coefficient and reducing the phonon thermal conductivity are the best choices that can effectively improve the devices’performance.For the TE materials for micro TEGs,increasing the Seebeck coefficient has the most significant improvement in device performance.For the current TE materials with ZT of 1.5,optimization of Seebeck coefficient is the most effective measure to improve the power generation performance of the corresponding devices.Operating condition,i.e.,heat absorbed by the TEG,cold side radiator,and the height of the TE leg are also important factors affecting material optimization strategy.Therefore,the actual operating conditions should be considered before deciding on the material optimization method.Finally,a process based on the power generation performance of TEGs to guide the optimization of TE materials is proposed.This thesis points out the current characteristics of interfacial effects and their optimization goals,comprehensively analyzes the influence of TE materials used in conventional TEGs and micro TEGs on the device performance,and summarizes the current optimization strategies for TE materials.The research content has a high reference value and guiding significance for the preparation of TE materials and TEGs with high power generation performance.