Study On The Design And Thermal-Electrical Field Coupled Modeling Of The Wearable Thermoelectric Generator

With the rapid development of intelligent wearable devices,the demand of the power supplies with long operating time and high power density is increasing.The thermoelectric generators(TEGs)could convert heat into electricity based on Seebeck effect with the advantages of clean,no waste and moving parts.However,at present,the power density of wearable TEGs is still low,which can't meet the driven power requirement of wearable electronics.Thus,a wearable TEG with good flexibility and high power density need to be designed to make these wearable devices self-powered.Besides,the heat transfer and generation performance of the wearable TEG need to be analyzed through modeling.In this dissertation,a novel wearable TEG is designed and fabricated.The effects of shape factor of thermoelectric legs on the nominal power density,and the influence of PDMS encapsulation and curved skin surface on the performance of TEG are investigated by modeling.Then the wearable TEG withheat sink is designed and analyzed by thermal resistance modeling,followed by the experimental research.This work was supported by National Natural Science Foundation of China under Grant 51275466 and Grant 51575485.In Chapter 1,the research background and significance of the dissertation were introduced,and the development trend and current research situations of the design and fabrication,analytical and numerical modeling,and thermal dissipation technology of TEGs were reviewed.Then the research contents of this dissertation were proposed.In Chapter 2,the design requirement of the wearable TEG was proposed.Then the theoretical model of the TEG with non-constant cross sectional thermoelectric legs was developed to find a better geometric structure of the TEG.The effects of the shape factor of the thermoelectric legs on the dimensionless efficiency and NPD(nominal power density)were studied.Finally,the structural design of wearable flexible TEG with PDMS(Polydimethylsiloxane)encapsulation was conducted.The P-type and N-type thermoelectric materials were also selected,and the corresponding material characteristics were measured.In Chapter 3,a numerical model was developed to investigate the performance of the wearable TEG with PDMS encapsulation.The influence of boundary conditions on the temperature and voltage distributions in the wearable TEG were studied,and the effects of the structural parameters on the.output performance were analyzed and validated by experiments.Results showed that the PDMS encapsulation can lead the majority heat transferring into thermoelectric legs.Besides,higher thermoelectric legs and thinner encapsulation are beneficial to the output.In Chapter 4,the numerical modeling of the wearable TEG on curved skin surface was developed.The curvature radius of the curved surface,the thickness and thermal conductivity of the thermal interface layer on the performance of TEG were studied.Results showed that the performance of the TEG can work well on the curved skin,and the thermal conductivity of the thermal interface layer has more significant impact on the performance than the thickness.In Chapter 5,the wearable TEG with heat sink was designed.The FPCB(Flexible printed circuit board)with hollows was utilized as the bottom electrodes.The influences of the plate fin heat sink and copper foam heat sink on the heat transfer and performance of the wearable TEG were investigated by using themal resistance modeling and experimental measurement.Results showed that the heat sink will improve the performance of wearable TEG,and the device with copper foam.heat sink has greater power per weight.In Chapter 6,the fabrication and encapsulation process of the designed wearable TEG was carried out.To reduce the contact thermal and electr cal resistance between thermoelectric legs and electrodes,the SAC305(Sn96.5Ag3Cu0.5)and Sn42Bi58 solders were used for soldering at hot-and cold-sides of the wearabe TEG,respectively.Then the thermoelectric legs were encapsulated by low-viscosity PDMS to improve the efficiency of the encapsulation.Finally,the copper foam heat sinks were assembled at the cold-side of the wearable TEG by using thermal conductive tape.In Chapter 7,the experimental measurement of output performance(voltage,internal resistance,power and power density)of the fabricated wearable TEG were conducted on lab-made setup.Then the accelerometer was driven by the wearable TEG worn on human wrist through the designed DC-DC step-up circuit,which can be used for human motion detection.In Chapter 8,the chief work and innovations of dissertation were summarized,and the further research subjects were proposed.