Development of a multi-node monitoring system for analyzing plant growth and indoor environment interactions: An empirical study on a plant factory

In plant factories, multi-layered shelves are used to maximize production per unit area by densely growing plants. The large number of plants placed in a spacious area leads to complex interactions between the plants and the growing environment, resulting in a potentially non-uniform growing environment. When the environment is non-uniform, achieving consistent production based on location becomes challenging. This study aims to analyze these interactions through multi-node, multi-factor monitoring in an actual plant factory that engages in hydroponics. To achieve this, we developed a monitoring system tailored for measuring the growth environment in plant factories. Specifically, we created a monitoring device capable of real-time measurement of six key indoor environmental factors, a network system that facilitates multi-node data collection by utilizing both Zigbee and WiFi, and a dashboard for simplified management. The developed monitoring system was implemented in an 'A' plant factory and collected 44,640 data points over a month. It empirically demonstrated that indoor environmental factors vary by location within the growing space, depending on the surrounding environment and the placement and operation of environmental facilities. The temperature of the nutrient solution showed a statistically strong correlation with other indoor environmental factors. This indicates that the operation of environmental facilities in a plant factory should be comprehensively managed in real-time, with a focus on the relationship of the nutrient solution temperature to other indoor environmental factors. Such management is especially crucial when considering the dynamic interrelationships among nutrient solution temperature, other indoor conditions, and the varying demands imposed by plant growth activity. These results offer valuable guidelines for optimizing the growing environment in plant factories and will serve as an important reference for plant factory operators.