Evaluation of Light Intensity and Uniformity of LEDs for Protected Crop Production

Abstract

This study was conducted to evaluate light intensity and uniformity of two SMD (surface-mount device) type LEDs for protected crop production. A lowpower (0.1 W) and a high-power (1 W) LEDs were selected and the intensity and uniformity was evaluated at different vertical (height) and horizontal (distance) intervals. When the horizontal interval of the LED bar was fixed, the light intensity increased and the uniformity decreased as the height decreased. At the 30~40 cm heights, 20~30% of the area showed 200 ±20 μmolm -2 s -1 . As the horizontal distance of the LED bars increased, while the uniformity increased as well, the light intensity decreased. At the distances of 6~10 cm, 17~23% of the area showed 200 ±20 μmolm -2 s -1 . When the LED bars were added to the sides, the light intensity and uniformity were generally improved. Results showed that the light intensity and uniformity depended on the height and interval of the LED bulbs; therefore, optimum arrangement for the crops interested should be determined through experiments.