Toward a higher yield: a wireless sensor network-based temperature monitoring and fan-circulating system for precision cultivation in plant factories

Currently, global warming is worsening, causing the difficulty of cultivating crops in open fields, and leading to unstable quality of crops. Plant factories provide a well-controlled growth environment for precisely cultivating plants. However, uneven temperature distributions (UTDs) still occur at each cultivation shelf in plant factories, which decreases the yields (fresh weight) of plants. In this study, a wireless sensor network (WSN)-based automatic temperature monitoring and fan-circulating system for precision cultivation in plant factories is proposed, and it is built upon the technologies of WSN, ordinary kriging spatial interpolation, and automation control, to precisely find the UTD areas of cultivation shelves. Once a UTD area occurs, the fan-circulating system can be triggered immediately to automatically trace the area and circulate the air. This action can effectively improve the air flow in the cultivation zone, providing optimal growth conditions for plants. The proposed system has been deployed in two plant factories that grew Boston lettuces, and a series of performance evaluation experiments were conducted. The experimental results indicate that the fresh weight of the harvested lettuces increases by 61-109% when employing the proposed system that efficiently and significantly decreases the variation of the temperature in the cultivation zone.