Study On The Thermoelectric Coupling Effect In Thermoelectric Energy Capture Structures

At current,the development of new-energy materials is one of the important needs for improving energy-saving technology in construction projects.Thermoelectric capture materials can achieve direct conversion of thermal and electrical energy,and the operation of thermoelectric modules has no noise,no pollution,and no harmful gas emission.The application of thermoelectric modules to engineering materials such as cement based composite can achieve efficient energy conversion,as well as improve the utilization efficiency of solar energy and other thermal energy in municipal and alleviate the urban heat island effect.The energy conversion of thermoelectric structure is one of the key indicators for the application of thermoelectric capture modules in civil engineering.The application of functionally gradient materials is one of the effective ways to improve the efficiency of the thermoelectric capture modules.To study the performance of thermoelectric conversion of new functionally gradient thermoelectric capture structure,a thermoelectric coupling model of thermoelectric components is established.Based on the basic thermoelectric equation,the temperature field control equation is derived.The concept of functionally gradient is introduced into the material parameters,and a variety of methods for solving the field governing equations are proposed according to the parameter characteristics of thermoelectric materials.The accuracy and convergence of the solutions are verified.The main research contents and conclusions are as follows:The analytical method is used to study the thermoelectric coupled field of a flat-plate thermoelectric capture structure.Firstly,when the thermoelectric materials are independent,the power series method is used to solve the linear coupled field equation with variable coefficients.It is verified that this method has high precision,fast convergence and good universality.Secondly,when the thermoelectric materials are temperature dependent,a power series iteration approximation method is proposed to solve the nonlinear equation with variable coefficients,and it has been proved that the engineering accuracy can be achieved after first iteration.Furthermore,by presetting the initial temperature field,the explicit analytical solution of temperature field distribution is derived.Finally,the optimal segment ratio of the thermoelectric legs of the twostage thermoelectric device is calculated.The results of numerical cases show that suitable gradient distribution could effectively improve the thermoelectric performance of the device when the material is functionally graded.The above research methods are extended to the annular thermoelectric energy capture structure.The power series method,the power series iteration approximation method and the explicit analytical method are used to study the temperature field distribution of temperature independent homogeneous device,functionally graded device,and temperature dependent device,individually.To simplify the model,the explicit solution is introduced into the trapezoidal thermoelectric generator.The results show that when the thermoelectric material is temperature independent and functionally graded,the conversion efficiency of the device has different forms even if the figure of merit is the same.Aiming at temperature dependent thermoelectric device,COMSOL software is used to model and analyze the temperature field of the devices,and the obtained temperature field distribution curve is almost exactly coincident with the temperature field distribution curve under first iteration.Based on the explicit analytical solution of the annular thermoelectric generator,the geometric size of the trapezoidal thermoelectric generator is optimized by introducing small parameters,and the three-dimensional finite element modeling of the trapezoidal thermoelectric generator is carried out by using COMSOL software.The simulation results are compared with the analytical results of the annular thermoelectric generator,and the influence of the geometric size on the maximum output power is analyzed.The optimization idea of functionally gradient is introduced to analyze the thermoelectric performance of cement-based composites when the parameters varied with exponential,linear and trigonometric gradients,and the results are compared with the existing research results.The results show that the effective gradient distribution can significantly improve the thermoelectric performance of the device.The above research method and conclusions could provide theoretical basis for the optimal design of thermoelectric energy capture structures based on functionally graded materials or segmented structures.And it has potential application value in the field of green energy capture.