Research On Environment Simulation And Design Method Of Solar Greenhouse In Northern Cold Region

Energy-saving Solar Greenhouse(ESG)is the main form of facility agriculture production in China.Solar energy is made full used by ESG,which is regarded as the main energy source.The solar energy is absorbed by front roof lighting,which provides a suitable light temperature environment for Greenhouse crop production.The heat storage cycle through heat preservation and thermal storage envelope structure are realized by ESG.Therefore,it is very important to provide crop winter production with reasonable sunlight transmittance,greenhouse heat preservation capacity and heat storage capacity.The experiments,numerical simulation calculations and software analysis methods are combined to propose the unique production methods of energy-saving solar.The changing of the light and heat environment,the rules of the light,heat environment bases on reasonable greenhouse lighting,insulation,heat storage theory and forms the theoretical method of greenhouse design are explored.Three aspects of problem is mainly studied in the thesis: how to maximize sunlight into the Greenhouse in order to increase the amount of light in the Greenhouse,how to reduce the release of the heat from the Greenhouse to the outside,how to store the energy in the Greenhouse for maintaining indoor temperature at night.This study is mainly based on the principle of thermal balance and the daily cycle which determines the relevant parameters of the Greenhouse according to the rule.The amount of heat absorbed in the Greenhouse is more than or equal to the amount of heat released from the Greenhouse,including span,ridge height,ridge position ratio,back wall height,front slope Plane angle,insulation selection,wall material and thickness,etc.The main research results are shown as follows:(1)Through research and analysis of experimental data,it is clear that solar radiation intensity,temperature,and the envelope structure of the Greenhouse are the key influencing factors of the environment in the Greenhouse.The paper determines the amount of solar radiation during the study period in the Greenhouse.It is clarified that the temperature and heat flux of the front slope,back wall,and soil of the Greenhouse show periodic changes with time.Meanwhile,obtains the temperature of the back wall and soil are gradually decrease with depth.Specifically,the soil temperature changes little at a depth of 0.8 m,which can be determined as a constant temperature layer.Hence,there is a marginal effect on soil temperature at the edge of the Greenhouse.(2)Linear regression and Weighted Markov Chain method are used to classify and predict air temperature,humidity,and soil temperature,etc.In the greenhouse,predict results agree well with the experimental results,which shows the method can predict the relevant environment parameters in the greenhouse in the short term.The non-steady-state thermal analysis method of ANSYS software is used.The simulation of the temperature changing in the wall and soil of the Greenhouse is from the surface to the interior in the Greenhouse.The weighted Markov chain prediction results are used as the boundary condition of the finite element simulation.So the simulation results are well validated.The reasonable thickness of the thermal storage layer and the thermal insulation layer of the wall by using the method is simulated and analyzed,then the optimal thermal storage layer and thermal insulation layer thickness of the greenhouse wall under the given indoor and outdoor temperature changes are obtained,which analyzes the soil temperature change in the greenhouse,and makes soil temperature adjustment more accurate.(3)Develop the Greenhouse design simulation platform based on thermal equilibrium theory.According to the characteristic of northern cold region and in accordance with the theoretical methods of reasonable lighting,heat preservation and heat storage,the heat storage and release balance of Greenhouse are regarded as the goal.Corresponding constraints to meet the greenhouse lighting,heat preservation and heat storage requirements are established.According to the basic parameters of the input greenhouse,the Greenhouse design parameters to meet the Greenhouse lighting requirements are calculated.So,the effect of heat preservation and heat storage are achieved by the wall and envelope structure.It uses the design results to analyze the greenhouse parameters,and makes the design of the greenhouse more reasonable.It can also provide help for the greenhouse designer.The rules of solar radiation,heat flow changes,and temperature changes in energy-saving solar greenhouses in northern cold regions are clarified and identified.The solar radiation intensity,temperature,and walls are the key factors affecting the environment of energy-saving solar greenhouses.A numerical simulation method combining numerical calculation and finite element simulation are established.In order to make the greenhouse design more reasonable,an energy-saving greenhouse design system based on thermal equilibrium theory is developed.