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Research Project: Sustainable Production and Pest Management Practices for Nursery, Greenhouse, and Protected Culture Crops

Location: Application Technology Research

Title: Optimization of spatial lighting uniformity using non-planar arrays and photosynthetic photon flux density modulation

item Harbick, Kale
item MATTSON, NEIL - Cornell University - New York

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2021
Publication Date: 3/8/2022
Citation: Harbick, K.J., Mattson, N.S. 2022. Optimization of spatial lighting uniformity using non-planar arrays and photosynthetic photon flux density modulation. Acta Horticulturae. 1337:101-106.

Interpretive Summary: Supplemental lighting is important for many controlled environment agriculture (CEA) facilities, allowing year-round production in greenhouses and plant factories. Most supplemental lighting arrays are comprised of equally spaced luminaires (lighting fixtures) that are all at the same brightness. This always results in a "bullseye" effect, where light levels are much darker at edges and corners of the growing space compared to the interior areas. This problem is most evident in plant factory shelves, growth chambers, smaller greenhouses, or any other environment without very large canopies. Uneven light results in uneven plant growth, which may be an issue for some growing operations. This paper proposes a potential solution to this problem. A computer program was developed that changes how some of the lights are controlled, dimming them in such a way that the light intensity at the canopy is more uniform, resulting in more uniform plant growth. This technology could potentially be integrated into horticultural lighting systems in the future.

Technical Abstract: Planar, regularly spaced arrays of horticultural luminaires exhibit poor spatial uniformity due to a bullseye effect where light intensity is higher at the canopy interior regions, and lower at the edges and corners. This can lead to uneven plant growth especially in sole-source lighting environments. A method is presented to improve spatial uniformity: intensity modulation of individual luminaires in a planar regular array. Luminaires are clustered by an algorithm into functionally similar groups, then an intensity level is found for each group according to a statistical measure of uniformity. Results from two photometric simulation scenarios are presented in which the algorithm significantly improves spatial uniformity.