Analysis of the Uniformity of Light in a Plant Growth Chamber

Abstract

Plant growth is greatly affected by light. However, the uniformity of light in plant growth chambers has always been a common problem that was not appropriately addressed. As this, the uniformity of light in a plant growth chamber illuminated by light-emitting diodes (LEDs) was investigated in this paper. The orthogonal experimental design method was used to test the influence of various factors on the uniformity of light intensity in a plant growth chamber using the lighting simulation software DIALux. The major factors investigated in this paper include the divergence angle, number and arrangement of LED lamps, as well as the reflectivity of the inner walls of the chamber and the minor factors include the vertical distance from the LED board and the distance from the board edges. The relative importance of influence of each factor on the uniformity of light in the chamber was obtained and finally, an optimized model of the plant growth chamber with a uniformly distributed illumination was obtained.Simulation results showed that reflectivity of the inner walls had the highest influence on the uniformity of light on the working plane, followed by the divergence angle of the LED lamps, and the number of LEDs had the lowest influence. Therefore, the number of LEDs may mainly affect the intensity of light on the working plane but not the uniformity on the plane’s illumination significantly, especially when the distance from the LED board is relatively large. Results also showed that the uniformity of light increases vertically from the LED board and with the edge distance as well. Based on our simulation results, a three-dimensional optimal cultivation area in a plant growth chamber was suggested which achieved the uniformity of 0.93.