Research On Solar Energy Collection Using Asphalt Pavement

The normal fossil energy on earth is limited although the demand of energy for human development is never-ending. Searching for renewable energy and improving utility efficiency of energy are the main approach for the energy and the environmental issue. Asphalt solar collectors are becoming a new way of harnessing solar energy due to its excellent heating-absorption property. Asphalt pavements serving as solar collector has been developed for the heating and cooling of adjacent buildings as well as to keep the pavement ice-free directly. As a result, it can abate the use of fossil fuel in heating buildings and reduce the CO2 emission. Besides the advantages mentioned above, top priority should be given to how to increase the energy potential and the thermal efficiency of asphalt collector. As Asphalt mixture is a typical temperature-sensitive material, consideration should be also given to effects on temperature distribution of asphalt pavement in the process of solar collecting.Based on fundamentals of heat transfer theory and meteorology, this study analyzes principles of pavement solar collection and its thermal process. Such basic concepts as pavement materials with an influence on asphalt solar collection and its structure characteristics as well as different environments and types of climate as are still explained in this paper in order to define key parameters that have effects on asphalt concrete's solar collection performance.Secondly, basing on the predecessors'achievements, the study in the following aspects:gradation design of asphalt mixture extracting thermal energy and the preparation of Thermal Conductive Asphalt Concrete by adding thermal conductive filler; evaluation of the water susceptibility of asphalt mixture through Marshall Remnant Stability (MRS) Test and Tensile Strength Ratio(TSR) Test; assessment of the rut-resistant stability of asphalt mixture at high temperature through Rutting Test; measurement of the thermal parameters of asphalt concrete through transient plant source method. As both water susceptibility and stability of asphalt mixture at high temperature meet code requirements, thermal conductivity of the thermal conductive asphalt concrete is increased by 28.9%.Thirdly, with reference to relative national standards and the actual situation of preparation and formation of asphalt concrete, the design of the laboratory testing system for solar energy collection, including that of the data acquisition and processing unit, the temperature\flow measure and control unit and radiation test and control system are stated in this study. It is proved that factual solar collecting circumstance can be simulated and temperature distribution test of the asphalt concrete slab is practical through heat-extracting test. The accuracy of the test results under the laboratory situation meets the demand of evaluating sample asphalt concrete's solar energy collecting performance.Fourthly, with the aid of equipment, the climatic conditions of pavement are simulated so that the temperature distribution can be measured. It can be concluded through such results as the whole changing process of the pavement temperature, the temperature vertical distributions and the temperature change rate and temperature gradient that thermal conductive asphalt concrete has a great influence on pavement temperature distribution, which helps to deduce that the optimum depth of pipe-laying is 2.5cm-5cm.Lastly, measuring the change process of internal temperature of the collector by inhaled the hydronic; evaluating the effects of various flows on deducing pavement temperature and the effects of initial temperature on the temperature changes during heating. The experiments mentioned above prove that solar energy collecting of asphalt concrete pavement can considerably reduce surface temperature:with the increase in flow, pavement surface temperature witnesses a linearity decrease; the thermal energy gain per unit area rises gradually as the outleting water temperature drops; deducing that the time for starting up and hydronic inlet is when underground temperature of the location of the pipes reaches the heat balance temperature needed by specific heat tranfer fluid and flow.