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ISHS Acta Horticulturae 1242: III International Symposium on Horticulture in Europe - SHE2016

Optimal spectrum modeling calculation with light emitting diodes set based on relative quantum efficiency

Authors:   N.U. Niangoran, L. Canale, F. Tian, T.C. Haba, G. Zissis
Keywords:   LED, RQE curve, plant growth, relative efficacy, photosynthesis, optimal spectrum, greenhouse
DOI:   10.17660/ActaHortic.2019.1242.121
Greenhouse lighting is the most important parameter for plant growth because it is at the root of the photosynthesis process. Light-emitting diodes (LED) have many advantages and can allow us to obtain an ideal plant growth's spectrum with enough intensity. This can be reached thanks to a wide range of LED panels with monochromatic and highly saturated colours. Thus, in order to enhance photosynthetic and power efficiency, we combined several LEDs to get optimal spectrum with minimum power consumption. To reach this goal, a combination of Gaussian and Pearson VII functions were simulated between 320 and 780 nm to fit the relative quantum efficiency (RQE) curve. Also, this paper proposes a new approach to evaluate photosynthetic efficiency and relative photosynthetic efficacy of the LEDs' wavelength. Models with Gaussian and Pearson VII functions are compared. Best results are obtained with Pearson VII functions and show that the RQE curve could be fitted with an RMSE error of 3.41%. From these results, we chose a commercial LED set and repeated the simulations with real wavelengths. Results show a spectrum variation of 4.59% with RQE curve. Thus, we calculate the optimal LED quantity to have best results with less LED as possible and results show strong differences between both models. From another way and according to the bandwidth of the photosynthetically active radiation (PAR) sensor, we simulated RQE curve between 400 to 700 nm and selected mathematically 12 LEDs by elimination from a wide basket. We got a 3.46% error with RQE curve in this bandwidth.

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