| This thesis presents a solar heating system which based on greenhouse heating effect and soil heat storage.In summer,the system stores surplus heat from greenhouse to underground soil,and then utilizes the stored energy to heat the greenhouse in winter.This thesis takes the common film plastic greenhouse as its object of study to test and simulate the solar heating system.The main work of this thesis includes the following parts:First,a physical model of the solar heating system has established.It is consisted of solar greenhouse and underground heat collecting system.The greenhouse and underground storage can be regarded as solar collector and energy storage respectively.This thesis studies the whole process of energy conversion of this system.Second,an experimental test platform has been built up to test the operation performance of this system.According to the relevant national standards,the heat collection efficiency of the greenhouseηcan be fitted as:η=0.174-0.249×((T_i-T_a)/G).The operation test results of underground heat collecting system indicate that the soil at the depth of 5 meters,10meters and 15 meters has the best storage efficiency.The heat transfer coefficient between U-type buried tube and soil is 716.3 W/(m~2·K).Last,a simulation model has been built by using TRNSYS.The system performance indicators are presented including the annual collected heat of solar greenhouse,the annual heat storage of system,the annual heating capacity of system and the annual heat loss of greenhouse.The heat releasing efficiency is defined as the ratio between heating capacity in winter and heat storage in summer.In this thesis,the system control strategy has been optimized for heat releasing efficiency,the optimized heat releasing efficiency can reach 64.1%.The optimized annual heat storage of system and annual heating capacity are 1917.9 GJ and 1227.6 GJ respectively.After one year system operation simulation,the soil temperature has decreased by 1.9℃,and after ten year simulation,the soil temperature has decreased by 6.6℃.In contrast,without the heat storage in summer,the soil temperature can increased by3.9℃and 8.8℃respectively,to ensure the probability of the long-term heat-collecting of the heat storage area. |
