Remote intelligent measurement and control system for granary ventilation based on absolute water potential diagram

Abstract: In this paper, a design of 'intelligent remote monitoring and control system of the granary' based on the absolute water potential theory (AWPT) has been proposed, which is used to improve information and intelligence level of the granary, and reduce the granary administrator's work difficulty. "Granary Ventilation Intelligent Decision System" (GVIDS) is the realization of this design. GVIDS's program development relies on the Android and the 'internet of things' technology. Its hardware framework, software framework, the main function modules and operational processes are the main research contents in this paper. The essence of AWPT is "the management and control method of granary's mechanical ventilation using water potential diagram" proposed by Wu Wenfu et al., which is improved on the basis of the Wu model. In the AWPT, there are three ventilation windows: cooling window, precipitation window and quality adjustment window, and each window corresponds to its appropriate operation mode of ventilation. When using AWPT to guide granary ventilation, the position of the air-temperature-point in the 'absolute water potential diagram' is observed to determine the need for ventilation, which means that the administrator makes proper ventilation operation according to the ventilation window area that the air-temperature-point falls. The client APP (application) consists of five parts, which are "Information Profile" module, "Absolute Humidity Diagram" module, "Absolute Water Potential Diagram" module, "Associated Equipment" module and "Managing Log" module. The "Information Profile" module is mainly responsible for displaying the basic information of different granaries; the theoretical basis of "Absolute Humidity Diagram" module is the WU model. First, the client will obtain the latest temperature and humidity data collected from the database. Then, according to the new grain CAE equation and allowing ventilation condition table, calculate and judge whether the current situation needs ventilation. Finally, draw the balanced absolute humidity diagram and balanced relative humidity diagram on the client. Absolute Water Potential Diagram (AWPD) is mainly composed of four curves and one point: absolute potential line of the air, absolute adsorption water potential line of the grains, absolute desorption water potential line of the grains, saturated humidity line of the air, and saturated humidity point of the air (Q). In the AWPD, the area surrounded by the blue lines is the cooling window, the area surrounded by the red line is the precipitation window, and the area surrounded by the green lines is the quality adjustment window. Because the cooling operation and precipitation operation is sometimes performed at the same time, there will be an overlap of the cooling window and precipitation window. "Associated Equipment" module is used to display the current equipments associated with the state of the work, and the user can remotely control these equipments with the switch buttons. "Managing Log" module is used for displaying all of the granary operation logs. The client App has so many advantages, such as friendly interface, simple operation, wide adaptability and intelligent and remote control, and it would solve the problem of limited working place for the granary administrator. In the simulated granary loading experiment, the performance of this system is very good, and it should be promoted.