Experimental Application Studies About The Pavement-solar Energy Utilization System

In summer, the asphalt pavement absorbs solar radiant heat during the daytimeand its maximum temperature can be above60℃, the high temperature makes thebearing capacity of the asphalt concrete decline, so that the severe track occurs onasphalt pavement. In winter, the asphalt pavement temperature is low，thephenomenon of ice freezing and crack on pavement will seriously affecttransportation. If the heat of pavement can be collected and stored in summer, theasphalt pavement temperature will decrease to prevent high temperature deformation.In addition, the heat stored during summer can be released to raise the asphaltpavement temperature for deicing and snow melting in winter.Unlike previous numerical heat transfer simulation, this article built anexperimental platform of the pavement-solar energy utilization system in a clearing ofTianjin, based on protecting the pavement, meanwhile deicing and snow melting forpavement, and verified its heat transfer effect in the actual climate environment. Anasphalt pavement was built in the experimental site, the horizontal heat transfer (totallength of238meters) was laid at the bottom of the asphalt layer, and the pavementheat transfer was connected with the vertical ground heat exchangers through thewater pump, forming a closed circuit of pavement-solar energy utilization. In addition,an automatic data acquisition system was designed to real-time monitor the outdoortemperature, the solar radiation intensity, the pavement temperature, the undergroundsoil temperature and the heat exchange amount of pavement heat transfer for one year.The data was used to analyze the actual heat transfer and application effect of thepavement-solar energy utilization system.The results showed that: In summer, the sustaining solar radiation made theordinary asphalt pavement temperature up to62.3℃. However, the heat collectingoperation of pavement-solar energy utilization system could effectively reduce thepavement temperature, the largest temperature drop was6.8℃, and the averagetemperature drop was2.8℃. Under conditions of natural irradiation, the average heatabsorption efficiency of asphalt pavement was36.8%and the average thermal storageeffectiveness of the system was20.5%in the daytime. In autumn, the pavement-solarenergy utilization system stopped running, the heat of2821kWh stored near theunderground heat transfer in summer spread to the surrounding soil, the monitoring point temperature near the underground heat transfer dropped by4.4℃before thesystem operation in winter,1.6℃higher than the initial underground soil temperature.In winter, the lowest temperature of ordinary asphalt pavement was-12.5℃. Whenthe pavement-solar energy utilization system run, the heat stored in soil was releasedto the asphalt pavement through the water to raise the pavement temperature, thelargest temperature rise was16.4℃, and the average temperature rise was4.1℃.During the operation of104days in winter, the system absorbed heat of4598kWhfrom the underground soil, the days of the experimental pavement surface temperaturebeing below freezing accounted for about twenty-seven percent of the total time,reducing thirty-two percent of freezing time compared with the ordinary asphaltpavement, effectively preventing snow cover and ice on the pavement. In spring, thepavement-solar energy utilization system stopped running, the cooling soil near theunderground heat transfer absorbed heat from the surrounding, the temperature ofunderground monitoring point rose to13.5℃before the next operation in summer.After the cycle of one year, the underground soil temperature dropped by0.2℃,showing the good heat storage capacity of the soil.