Study On The Collector And Heat Storage System For Solar Buildings

With the decrease of fossil energy resources,the modern society is facing serious problems.As an important part of exploiting and utilizing renewable energies,solar buildings have immense social and economic benefit.China is rich in solar energy resources which provide favorable conditions to the utilization of solar energy.There exists a vast market of prospects for the use of solar energy in buildings.Concerning with the main problem of the solar buildings,namely collectors and thermal storage systems,we carry out four parts of studies.(1)We design a solar fiat-plate collector/thermal storage system which combines the collector and thermal storage unit together.It can not only store the solar energy effectively,but also reduce the heat loss and increase the thermal efficiency of the collector.By the heat transfer analysis of the collector/thermal storage system and ordinary collector,we could establish the heat transfer network picture and calculate the theoretical thermal efficiency of the two systems,as compared with the latter,the former was far higher.(2)We design and build a rooftop solar heating system,which install solar air collectors on the roof of the cottage.The pipeline and axial flow fan will import hot air which collected by the collectors to the solar building to heating.We also get the heat loss of the solar building and the need for the collector area by the termal calculation.The collectors will be used in the rooftop heating system to verify the actual heating effect for the solar buildings.The results show that in winter of Zhenjiang Jiangsu Province,in a sunny daytime,the temperature of the rooftop experimental solar building could reach 20℃in maximum,the average temperature of the room is approximately 18℃,it's about 6℃higher than the maximum temperature of the contrasted room.The average heat flux(lasted 5 hours)could reach 2276W(134W/m~2),whereas the heat load of the solar building is only 2038W(120W/m~2),it's approximately 10%higher than the later.For an ordinary well insulated building,the heat load is about 30W/m~2.Therefore,if we strengthen the building insulation and increase a heat storage system,the surplus thermal energy which collected during the daylight could meet all the needs of heating at night,so we could achieve an effective heating of the building for 24 hours in winter.(3)Then we design and install a hanging solar building heating system,which hung solar air collectors to the north wall of the solar building.The hot air will get direct into the solar building for heating through the fan which installed on the exit of the collectors.The temperature of the hanging experimental solar building could reach 24℃in maximum,the average temperature of the room is approximately 21℃,it's about 6℃higher than the maximum temperature of the contrasted room and about 11℃higher than the temperature of the environment.The average heat flux(lasted 6 hours)could reach 779W(27W/m~2),whereas the heat load of the solar building is only 493W(17W/m~2),it's approximately 37%higher than the later.Therefore,the hanging solar building heating system could function well for the heating of the solar building in winter,if we increase a heat storage system to store the surplus 37%solar energy during the day,the heating of the solar buildings at night and in a rainy day will be come true.(4)Finally,on the basis of analysis of various thermal storage materials,we choose paraffin for the phase change material(PCM)of the solar buildings.We do a lot of experiment to study the performance of the paraffin in the process of the thermal storage and put forward some corresponding solutions to the problem which emergence from the experiment.Besides,we design two thermal storage systems for the solar buildings and its feasibility remains to be further study.