How intelligently controlled LEDs can be used to more efficiently manage supplemental lighting in greenhouse production systems

In greenhouse production, high pressure sodium (HPS) and light emitting diode (LED) supplemental lighting systems are normally controlled in an on/off manner according to user-programmed photoperiod and ambient light thresholds.
While not practical with HPS, fixture-dimming strategies and automatic control are technically feasible with LEDs.
Dimming could allow supplemental LED intensity to be modified, in real-time, in response to varying levels of natural light.
Further enhancements are possible by combining additional input factors like upper/lower thresholds of photosynthetic photon flux density (PPFD), target daily light integral (DLI; the amount of PPFD received by the crops over 24-h), time-of-day electricity pricing, latitude and historical PPFD data into a predictive algorithm.
These control strategies have the potential to enhance crop productivity by attenuating fluctuations in canopy-level PPFD, while simultaneously minimizing energy cost.
The present study investigated cut gerbera production under threshold-controlled HPS compared with intelligently controlled LED using Heliospectra’s HelioCORE™ DLI-controller to manage their LX602G multichannel intelligent grow lights.
Each treatment had four replications within a common growing area, during the supplemental lighting season in Ontario, Canada.
Both controllers were programmed to target total DLI of 7 mol m^‑2 d^‑1. The overall mean canopy-level DLI were 8.40 and 7.77 mol m^‑2 d^‑1 for HPS and LED treatments, respectively.
There were no treatment effects on number of flowers initiated, harvested, and % marketability.
HPS-grown flowers developed 5% faster but had 7% lower fresh mass and 4% shorter stems versus LED. The DLI-controlled LED treatment had reduced supplemental light usage but similar crop productivity.

XXX International Horticultural Congress IHC2018: III International Symposium on Innovation and New Technologies in Protected Cultivation

D. Llewellyn, J. Lindqvist, Y. Zheng

DLI, HPS, cut gerbera, feedback control

https://doi.org/10.17660/ActaHortic.2020.1271.18