Design And Implementation Of A New Thermal And Humidity Environment Control System Platform Using For Solar Greenhouse

China unveiled its"No.1 central document"for 2023,outlining we should rely on the national conditions and agricultural conditions,reflect Chinese characteristics,strengthen agricultural infrastructure construction,promote the development of agricultural science and technology equipment,and actively develop facility agriculture.Among them,solar greenhouse,as a facility agricultural building with natural light as the main energy supply,plays a crucial role in meeting the demand of urban and rural residents in northern China for off-season vegetable supply.However,practitioners of solar greenhouse often suffer from greenhouse environmental factors.Under the condition of ensuring indoor temperature,excessive relative humidity will threaten crops in the greenhouse,leading to yield reduction or crop failure.Therefore,it is necessary to adjust the heat and humid environment in the greenhouse.This paper analyzes the heat and humid environment required for indoor growth of common crop types in winter solar greenhouses in Northwest China.At the same time,a new type of dynamic control system for thermal and humid environment is proposed for the unique solar light resources in the northwest region,including active and passive phase change wall heat storage and release system,frozen dehumidification system and carbon dioxide concentration control system.Based on these systems,the control logic of the new solar greenhouse thermal and humid environment control system was designed,and the numerical model of the new solar greenhouse thermal and humid environment control system was established.By combining the control system with numerical simulation,a series of studies were carried out by changing the relative humidity threshold range.The main research results are as follows:（1）Based on the control system in the new solar greenhouse,according to the local sunshine time and environmental factors in the region,the thermal and humid environment control system is divided into two periods of day and night,which is divided into six sub-modules.These modules include daytime active heat storage mode,daytime CO₂supplement mode,daytime indoor dehumidification mode,daytime indoor dehumidification mode（with insulation turned off）,nighttime indoor dehumidification mode（with low temperature）and nighttime indoor dehumidification mode（with high temperature）.Through these modules,it is possible to ensure the opening and closing time of heat preservation,and meet the environmental requirements for crop growth in greenhouse.（2）A new type of thermal and humid environment control platform based on the characteristics of solar greenhouse and the control logic of thermal and humid environment control system is proposed,which can realize accurate monitoring and regulation.The visual monitoring and control system is constructed by using MCGS configuration software（Monitor and Control Generated System）,which improves the usability and practicability of the thermal and humid environment control platform,it can meet the actual needs of solar greenhouse practitioners.（3）A new type of solar greenhouse heat and humidity environment control system model was established,and the accuracy of its numerical simulation calculation was verified.By comparing the experimental data,the maximum relative error of temperature was 11.88%,the average relative error was 5.33%,and the average error temperature was 0.22℃.（4）Through the analysis of simulation data,different wind speed and relative humidity thresholds are selected to operate the dehumidification system to achieve the optimal temperature and humidity environment control effect and maintain a short running time and stable indoor temperature and humidity fluctuation state.Considering the above factors,in the cloudy day,when the relative humidity threshold is set at 90%-75%,the wind speed of0.5m/s is selected to run the dehumidifier,and the temperature in the greenhouse can be maintained at 9.07℃-12.95℃,which basically meets the needs of plant growth environment;when the relative humidity threshold is set at 90%-70%and 85%-70%,the average temperature range can be maintained within 10.01℃-10.67℃ when the wind speed of0.75m/s is selected to run the dehumidifier.In the cloudy day and night,for 90%-75%relative humidity threshold range,select 1m/s wind speed to run the dehumidifier;for the relative humidity threshold range of 90%-70%and 85%-70%,0.75m/s wind speed can be selected to run the dehumidifier.The above three working conditions have moderate running time,and the average temperature range in the greenhouse can be maintained at9.42℃-10.15℃,and the relative humidity remains in a stable fluctuation state,meeting the environmental conditions required for plant growth.（5）In sunny days,the dehumidification machine running at a wind speed of 0.75m/s can achieve the optimal effect within the relative humidity threshold range of 90%-75%,and the indoor temperature can be increased by 6.18℃.For different relative humidity threshold ranges,different wind speeds can be selected to run the dehumidifier.In the 90%-70%,90%-65%,and 90%-60%threshold ranges,0.75m/s,0.75m/s,and 1m/s wind speeds can be selected to run the dehumidifier,and the greenhouse air temperature can be increased by8.4℃-9.2℃.On sunny nights,for the four relative humidity threshold conditions of90%-75%,90%-70%,90%-65%,and 90%-60%,the wind speeds of 1m/s,1m/s,0.75m/s,and1m/s can be selected to run the dehumidifier,and the average temperature of the greenhouse air was maintained between 11.99℃ and 12.93℃.For the three relative humidity threshold conditions of 85%-70%,85%-65%and 80%-65%,the average temperature of the greenhouse air is maintained in the range of 12.24℃-12.54℃ by using 1m/s,0.75m/s and 0.75m/s wind speed to run the dehumidifier.When the relative humidity threshold is 85%-60%and80%-60%,0.75m/s and 1m/s wind speed can be selected to run the dehumidifier,and the average temperature of greenhouse air is kept in the range of 12.97℃-13.03℃.