| With the sustained and rapid development of economy and the improvement of human living standard,the demand for energy around the world is also growing.Limited fossil energy challenges the sustainable development of human society;thus,people have always been committed to the exploration,development and utilization of new energy resources,among which the utilization technologies of solar energy and shallow geothermal energy have become increasingly mature in buildings.In recent years,the pavement as solar collector has attracted more and more attention,however,like the traditional photovoltaic panels,only a small part of the solar energy is converted into electric while the rest is converted into heat,and the photoelectric conversion efficiency is even lower than that of traditional photovoltaic cells.Therefore,based on the photovoltaic-thermal technology,in this paper,a novel photovoltaic-thermal road by combining the pavement photovoltaic technology and pavement heat collection technology was proposed.The structure layers of photovoltaic-thermal road from top to bottomare are transparent surface,photovoltaic cell module,asphalt concrete with pipe network buried in it,and it could meet the traffic demand,generate electricity and harvest heat simultaneously.Due to the limitation of solar energy and shallow geothermal energy when used alone,thus,taking the photovoltaic-thermal road as solar collector,a photovoltaic-thermal road-ground source heat pump system was further proposed for building heating,which could realize energy complementary and improve the energy utilization rate.In this paper,firstly,according to the characteristics heat collection and power generation of the photovoltaic-thermal road,the corresponding mathematical model and its solution method were established,and the calculation program was compiled by Fortran language.In order to verify the correctness of the mathematical model,a photovoltaic-thermal road-thermal energy storage tank system was built in the laboratory,and the artificial solar simulator was used as the light source.The variation of the water temperature in thermal enery storage tank,the temperature inside the photovoltaic-thermal road and the power generation of photovoltaic cell with time were measured during 7-hour operation of the experimental system,and compared with the simulation results to verify the mathematical model.The verified mathematical model was used to simulate the heat collection and power generation performance of photovoltaic-thermal road,and the results were compared with the performance of corresponding photovoltaic road.The results show that the overall efficiency of the former is higher than that of the latter,and it shows that the photovoltaic-thermal road could greatly improves the solar energy utilization rate compared with the photovoltaic road.In addition,the effects of meteorological parameters(solar radiation intensity,ambient temperature and ambient wind speed),structure parameters of photovoltaic-thermal road(transparent surface transmissivity,thermal conductivity of asphalt concrete and packing factor of photovoltaic cell),parameters of thermal-collecting pipe in road(diameter,pitch and burial depth of pipes)and operation parameters(mass flow rate of circulating water and initial water temperature in tank)on performance of photovoltaic-thermal road were further studied.The results show that the increase of solar radiation intensity,ambient temperature,transparent surface transmissivity and packing factor of photovoltaic cell have positive influences on the overall efficiency of the system,while the increase of ambient wind speed,initial water temperature in tank and burial depth of pipes have negative influences on that.The diameter of pipes has little effect on the overall efficiency when the fluid velocity in pipe is kept constant.Considering comprehensively,the recommended thermal conductivity of asphalt concrete is 1.0?1.5W/(m·K),and the recommended pitch of pipes is 0.09?0.15 m.With the increase of the mass flow rate of circulating water,the overall efficiency increases,and the primary energy saving rate of the system reaches the maximum value when the mass flow of the mass flow rate of circulating water is 0.4 kg/s.Taking photovoltaic-thermal road as solar collector,a photovoltaic-thermal road-ground source heat pump system was proposed for building space heating,and the dynamic simulation program was compiled by Fortran language to study the system operation performance of proposed system during non-heating season in Beijing.Next,the effects of operating control temperature difference for the process of heat collection and heat storage and system operation mode(mode 1 and mode 2)on syetm performance during non-heating season were studied,and the operating control temperature difference was optimized by considering the energy output and energy consumption of the system.The results show that the system performance of mode 1 is better than that of mode 2.The optimal combinations of operation control temperature difference for heat collection process and heat storage process under mode 1 are 2?and 10?,and that of mode 2 are 2?and 4?.Finally,taking building heating for a typical expressway service area accommodation building in Beijing as an example,and the effects of the collector area of photovoltaic-thermal road,the length of ground heat exchanger and its arrangement on the heating performance were studied by simulating a 10-year operation period.Moreover,taking the solar fraction of electric energy and the soil thermal imbalance rate as the optimization objectives,the appropriate configuration relationship between the length of ground heat exchanger and the collector area of photovoltaic-thermal road for the accommodation building heating is 18.52 m/m~2. |
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