Economic design of artificial light plant factories based on the energy conversion efficiency of biomass

Abstract

Since plants with a high biomass conversion efficiency of light energy consume less energy and require shorter cultivation periods, it is expected that plant factories can have more output with less energy. However, there have been few studies on the biomass conversion efficiency of light energy in various cultivated plants, and this agricultural engineering field is still unexplored. If the amount of energy consumed by a plant factory can be obtained from the biomass conversion efficiency of light energy, the plant types that can be grown in a plant factory and the economic efficiency of the plant factory can be clarified. In this study, we determined the amount of light energy required for plant cultivation by measuring the wavelength distribution of sunlight and plant-growing light-emitting diodes. Also, we investigated the light to biomass conversion efficiency from the amount of heat generated by the biomass of cultivated plants. The light to biomass conversion efficiency was also used to analyze the payback period of plant factories so as to estimate the profitability of various cultivated plants. The solar to biomass conversion efficiency of the tested leafy vegetables ranged from 0.03% to 0.62%, while the efficiency of the cultivation LEDs ranged from 1.21% to 20.1%. The conversion efficiency including the energy consumption of air conditioning ranged from 0.13 to 5.7%. By measuring the biomass conversion efficiency of plants, it is possible to analyze the profitability of plant factories with a high degree of accuracy.