Analysis of environmental uniformity in a plant factory using computational fluid dynamics (CFD) analysis
Plant factories, essentially an enclosed warehouse with artificial lighting produces crops indoors in multi-layers under fully controlled environmental conditions. Existing commercial systems have been mostly constructed inside a warehouse building with multi-layer production shelves without considering detailed engineering design fundamentals with the multi-tier production system, air distribution and HVAC systems. Due to the limited and uneven air circulation inside each shelf and large production domain, the environment may not be uniform, limiting the production quality, yield and speed. Thus, the resource consumption is increased as the growing period is extended. It is necessary to design production and air-distribution systems in plant factories under sole-source lighting for providing sufficient air-current speed for optimal gas exchanges and transpiration rates, improving uniformity of the environment, and efficient delivery of CO2. In this study, a numerical simulation using computational fluid dynamics (CFD) was performed to analyze five configurations for air-distribution system designs on environmental uniformity in a plant factory system with average air-current speed, average air temperature, and relative standard deviation (RSD) at crop canopy zone. The results showed that a localized air-distribution system can help to improve the climate uniformity in the cultivation beds. A poorly designed system exhibited short-circuiting behavior to cause stagnant zones in the shelves (case 1-2). Compared to using a few air vents supplying ventilation air from roof (case 1-1), air tube with air jets can produce higher average air-current speed at crop canopy zone (case 2-1). For case 2-2 with air tube to provide cool air horizontal to each shelf, the airflow uniformity varied significantly from the plane at air jets to the bottom of cultivation beds. Case 2-2 can be an alternative design for industrial applications in indoor plant factory. A further study for the suitable height or configuration of air tube and shelf is recommended.
Zhang, Y. and Kacira, M. (2018). Analysis of environmental uniformity in a plant factory using computational fluid dynamics (CFD) analysis. Acta Hortic. 1227, 607-614
CFD, indoor plant factory, air uniformity, air flow pattern, vertical farm