| As a class of green materials,thermoelectric cement utilizes the temperature difference between the road surface and the ground to achieve the interconversion of heat and electricity.Cement-based materials are characterized by wide sources,low cost and good mechanical properties for large area applications.Since the preparation of large-size thermoelectric cement materials degrades the thermoelectric properties,however,the existing thermoelectric cement-based composites with excellent thermoelectric properties are small in size to the extent that they cannot meet the needs of large-area applications.The conventional casting method of thermo-cement matrix composites is prone to dry shrinkage and cracking,resulting in poor thermoelectric properties.In this paper,a cement matrix composite block is prepared by dry pressing method to assemble a thermoelectric cement conversion module more suitable for road energy harvesting.The microstructure,electrical conductivity,Seebeck coefficient,thermal conductivity,power factor and thermoelectric optimum values of cement matrix composites are systematically studied.The thermoelectric properties of cement matrix composites are studied by adjusting the molding pressure and raw material admixture,and the best process for preparing cement matrix composites with larger size thermoelectric properties is derived,and the mechanism of thermoelectric property enhancement is also revealed.The temperature field variation of the conversion module of cement matrix composites is also simulated and experimentally compared and analyzed as well as tested for other applications.The main findings of the study are as follows.The dry compression molding process was used to prepare cementitious composites,and the reduction of porosity inside the cement matrix helped to build up the conductive network to improve the electrical conductivity of the cementitious composites.The cement matrix composites with 10.0 wt%expanded graphite（abbreviated EG）were more stable in terms of thermoelectric properties,with a maximum conductivity of 0.54 S/cm,a maximum Seebeck coefficient of-11.74μV/K,and an average power factor of 4.64×10-3μWm-1K-2.The electrical conductivity and power factor of the cement matrix composites prepared at 40 MPa molding pressure The highest conductivity and power factor were 0.64 S/cm and 0.0043μWm-1K-2,respectively,for the 10.0 wt%EG cement matrix composites prepared at 40 MPa molding pressure and containing 10.0 wt%EG cement matrix composites with 5.0wt%of metal oxides and zinc oxide（abbreviated ZnO）.composites had the highest conductivity,Seebeck coefficient and power factor of 0.58 S/cm,-20.79μV/K and0.0348μWm-1K-2,respectively.Finite element analysis and field tests of the heat transfer temperature field of the cementitious composite conversion module were performed using COMSOL Multiphysic 5.4 simulation software.The average conductivity of the EG cement matrix composite conversion module is 0.022 S/cm,and the average conductivity of the conversion module with ZnO is 0.013 S/cm.The Seebeck coefficient of the EG cement matrix composite conversion module with ZnO is twice as high as that of the EG cement matrix composite conversion module with ZnO.Seebeck coefficient of the cement matrix composite conversion module with ZnO was twice as high as that of the EG cement matrix composite conversion module.The average power factor of the EG cementitious composite conversion module with ZnO added was6.7×10-4μWm-1K-2and the average power factor of the EG cement matrix composite conversion module was 2.9×10-4μWm-1K-2,an increase of 2.3 times.the output voltage of the EG thermo-cement conversion module reached a maximum of3.38×10-4μV with a power of 0.020μW.adding 5.0 The maximum output voltage of the conversion module of the EG cement matrix composite with 5.0 wt%ZnO is4.65×10-4μV and the power is 0.023μW.The conversion module of the EG cement matrix composite with ZnO has a higher power and therefore takes a relatively shorter time to melt the ice.Converting to a 1 km long and 10 m wide pavement,the application cost is the lowest compared to other thermoelectric energy harvesting systems,although the energy obtained by conversion is limited,but the cement matrix composite can be applied to the whole pavement.Finite element analysis and environmental testing of the heat transfer temperature field of the conversion module of a cement matrix composite and a thermoelectric generator（abbreviated TEG）were performed using COMSOL Multiphysic 5.4 simulation software.As the number of TEGs increases,the area of cooling on the upper surface of the conversion module becomes more pronounced.The addition of TEGs significantly improves the thermoelectric performance of the conversion module.Although the conductivity of the conversion module of cement matrix composite and TEG is only 0.0084 S/cm,the Seebeck coefficient of the conversion module reaches a maximum of-13953.80μV/K,which also results in a increase of the power factor to 153.21μWm-1K-2and a maximum power of 4239μW.The conversion module of cement matrix composite and TEG The module is connected to a boost device to light up a wide range of LEDs.The time required to de-ice the cement matrix composite and TEG conversion module for ice melting experiments is also the shortest. |
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