The 2011 ASHS Annual Conference

In preparation for construction of a plant atrium facility in NASA’s Habitat Demonstration Unit (HDU), commercial, off the Shelf (COTS) 50 watt UFO LED grow lights were evaluated as plant light sources.  Initial comparisons were made between a smaller 15.24 cm unit (50W AIBC Aseeding RB81-630) and a larger 26.7 cm unit (50W AIBC-RB81-630), each with 630 nm reds and 460 nm blues. The smaller unit had 50 LEDs in the ratio of 44 reds to 6 blues.  The larger unit had 48 LEDs with 43 red and 5 blue.   Both units were rated at 50 W, ran on standard 110 VAC, and had no dimming control.  PAR measurements and spectral scans were taken of both UFO units at different heights below the fixture and at distances out from the center to determine uniformity.  Although both units had a 50 W rating, the larger LED array had a 40% greater quantum output than the smaller unit.  Both UFO units showed a similar average decrease in PAR away from the center of the fixture to approximately 70% of full level at 18 cm from center at a height of 30.5 cm, but the larger UFO was more uniform overall.   The larger UFO unit (50W AIBC-RB81-630) was selected for HDU and an additional eleven units were obtained and characterized for uniformity.  These eleven units had a slightly different LED distribution than the initial unit, with 42 red and 6 blue LEDs.  They also had slight differences in the housing.  PAR measurements of the eleven units at 30.5 cm varied from 185 to 207 µmol m^-2s^-1 with the average value 196.9±7.3 µmol m^-2s^-1, indicating PAR output with less than 4% difference between the UFO units.  The voltage and current draw of the eleven fixtures were also uniform.  An additional large 26.7 cm 50 W unit with 660 nm red LEDs instead of 630 nm ((50W AIBC-RB81-660) was also characterized.  This UFO unit had a slightly higher quantum output of 224.9 µmol m^-2s^-1 than the 630 model UFO’s, but the power usage was similar between the two LED configurations.  In summary, the UFO LED light fixtures showed good consistency within a batch but models between batches varied.  The smaller light had lower output than the larger unit even though it had a greater number of LEDs.  The 660 nm unit had a slightly higher PAR output than the 630 nm unit.