Significantly enhanced energy efficiency through reflective materials integration in plant factories with artificial light

Plant factory with artificial light (PFAL) based on vertical farming is a promising technology for resource-efficient plant production, especially in urban areas or arid regions. However, the lighting system of PFAL requires a large amount of energy, which makes the total energy cost much higher than open-field and greenhouse farming. To address this issue, in this work, a cultivation system integrated with highly reflective materials is demonstrated in PFAL, which reduces light energy consumption by more than 36 %. A low-cost reflective film is fabricated with an overall reflectivity of 96.5 % in the entire photosynthetically active radiation spectrum. The effectiveness of this reflective film in reducing energy consumption is further demonstrated with optical simulation analysis and the corresponding computational fluid dynamics simulation based on an experimental cultivation rack. The corresponding field experiments of 3 different types of lettuce, Crunchy, Butterhead and Grand Rapids, under different light intensities are conducted in the cultivation unit. With reflective film properly installed, a 36 % reduction of light energy consumption is demonstrated while the dry weight and fresh weight still increase. An additional benefit is that the light reception area of lettuce becomes larger due to the more uniform lighting with the integration of reflective material. This work presents a simple yet reliable strategy for enhancing the energy efficiency in PFAL systems and can achieve the cost-effective daily production of lettuce with significantly reduced energy input.