| Solar energy is a clean source and renewable energy. In Xinjiang area, the solar energy source is rich, the total sunshine per year is about 2600~3000 hours, it has the unique conditions to take advantage of solar energy. The growth of crops is directly affected by soil temperature, the growth of crops will be seriously inhibited if the soil temperature is lower than the normal that required for the growth of crops. Currently, the greenhouse mainly adopts hot air stoves to heat air directly in Xinjiang area. The effect of this heating method is obvious but it has less influence on the root zone soil temperature. In addition, this method gives rise to a huge amount of fossil energy consumption and serious pollution.Aimed at above problems, this report has designed a solar energy heating system that it could heat the root zone soil directly in the greenhouse. Based on this, the system has been studied experimentally and theoretically in the greenhouse. The main subjects of report could be summarized as followings:(1) The heat transfer in greenhouse has been analyzed, and the energy equations among greenhouse structure, indoor air and soil have been established. The total energy-balanced equations in greenhouse also have been given. The thermal load is calculated about 820.08 MJ.(2) Set up a solar heating system in the greenhouse. The system mainly consists of heat collecting system and inner circulation heating system. It adopts water as the heat transfer medium, using the underground pipe to heat soil for raising the temperature. Through the comparative analysis to determine the flat plate collector as the main composition of heat collecting system, select the booster pump as the inner circulation pump. It also determines parameters of the heat pipes laying.(3) Experimental studied on the application effect of the solar heating system in greenhouse. Three different kinds of inner circulation strategies,full time circulation, night circulation, half night circulation, all improved the root soil temperature. Among them, the effect of full time circulation model is more obvious: the 20 cm, 30 cm depth soil temperature were respectively increased 1.9℃ and 2.9℃, and the enhancement ratio were 12.5% and 19.3%. The average soil temperature will be above 16℃ when inner circulation heating system is adopted in the greenhouse whether the weather is cloudy or sunny.(4) Used the Fluent software to simulate the soil temperature field. It had got some useful conclusions.(5) From the points of energy conservation, economic and environment effectiveness, the advantages of solar energy heating system have been discussed. For this system, it could save the coal consuming about 1620 kg a winter, it could reduce the cost of burning coal about 648 yuan per winter. Besides, it could save 371.52 yuan in winter exclude the electrical consuming. In addition, the emissions of CO2, SO2 and NOx could be reduced about 4244.4kg, 13.8kg and 11.9kg respectively. |
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