Performance Optimization Of Flexible Thermoelectric Generator

In recent years,with the rapid progress of intelligent wearable devices in the medical and health industry,frequent battery charging and changing of the devices have become the major challenges encounter by the industry.When the human body is self-regulating the core temperature,the thermal source of human body,an excellent type of renewable energy,can continuously radiate thermal energy from the skin.As a device that converts thermal energy into electric energy,thermoelectric generator(TEG)is environment-friendly and dispensed with moving parts.TEG can obtain energy from the natural temperature difference between human skin and the ambient environment to constantly transmit electrical energy to intelligent wearable devices.However,traditional rigid TEG is over heavy and unable to be bent,thus not fitting the curved surface of the skin well.Therefore,it is urgent to design a wearable flexible TEG with good flexibility and light weight,in order to realize the selfpowered intelligent wearable device.In this paper,by adopting simulation analysis and experimental study,the following work on wearable flexible TEG was implemented:1.Firstly,according to the requirements on the power supply of intelligent wearable device,the parameterized calculation model of wearable TEG was established;through the design of experiments,the accuracy of the model was verified;the TEG with PDMS flexible package was designed;based on the reflow welder technology,the thermoelectric module unit without ceramic substrate was prepared;and the performance testing platform of TEG was set up,and the platform was tested and verified.2.Secondly,based on the simulation model verified by experiments,the effect of load resistance,dynamic internal resistance,exposure effect,packaging materials and structural parameters on the performance of flexible TEG was analyzed;the power generation performance and mechanical structure performance of the device were discussed.The results indicate that when the number of pairs of thermocouples is less,the effect of different packaging materials on the performance of the device is quite different;the more the number of pairs of thermocouples in the device is,the less the effect will be;and in the structure of more than 90 pairs of thermocouples,the effect of packaging materials on the performance of the device equals to the constant value of 7m W/cm2,which is similar to the effect of surrounding air on the performance of thermocouples.Due to the removal of the rigid base,it is necessary to install multiple thermocouples for the flexible TEG to maintain the integrity of the mechanical structure.In this study,127 pairs of thermocouples were designed.Through analysis,in this case,the performance of TEG with flexible packaging material can reach the performance level of air dielectric,which makes the flexible TEG more excellent than similar rigid products.Because the flexible TEG is applicable to be operated in the low temperature difference with the human body as the thermal source,the exposure effect on its performance shall be considered.In this paper,change law under different exposure effects was analyzed in detail.The results indicate that the lower the exposure effect is,the better the output performance of the device is;and the contact effect is mainly linked to the selection and processing technology of packaging materials.With the increase of thermocouple height,the output power of the device increases firstly and then decreases,while the conversion efficiency increases continuously and finally equals to a constant value.When the thermal stress increases rapidly with the increase of thermocouple height,once it reaches a certain point after the peak power,the thermal stress begins to decrease gradually.With the increase of the side length of the thermocouple,the output power of the device begins to decrease gradually,and the conversion efficiency increases firstly and then decreases.However,the side length attaches non-significant effect on the conversion efficiency.The thermal stress increases firstly with the increase of side length,and then decreases rapidly.When the thermal stress reaches the maximum,the output power has not reached the peak value.With the increase of the distance between thermoelectric units,the thermal stress increases and the output power are not affected.3.Finally,through the analysis,the main factors were summarized and value range were proposed;based on the response surface method,the effect of these factors on the output power,conversion efficiency and thermal stress of the TEG was discussed;based on the design of orthogonal test,an orthogonal table with 3 factors and 3 levels was formulated;the output in the orthogonal table was determined as the output power,conversion efficiency and thermal stress;based on the simulation data,the analysis was performed,thereby obtaining the significance of each factor to the performance of the TEG.Based on the results of the above data simulation,the regression equations of output power,conversion efficiency and thermal stress were written;by utilizing the response surface method,optimization analysis was carried out,in order to obtain the optimal parameter combination of maximum output power,maximum conversion efficiency and minimum thermal stress;and through multi-objective optimization,the optimal parameter combination under the integrated effect of multiple factors was concluded.The optimal parameter combination: h is 1.29 mm,w is 1.68 mm,s is 0.65 mm,sunder the condition of the P is 18.59 m W,η is 3.955%.