LED lighting optimization as applied to a vitamin space plant growth facility.

An algorithm of determining optimal LED lighting parameters for leafy crops (Chinese cabbage Brassica chinensis L. was taken as a model) in a vitamin space Plant Growth Facility is proposed. The lighting parameters to optimize were the level of photosynthetic photon flux density (PPFD), red and white LEDs PPFD ratio and pulse repetition period with a fixed pulse length 30 µs. Optimal lighting parameters should allow achieving a high biomass yield per consumed light energy, as well as high vitamin C content in the crop biomass. A quantitative optimality criterion for estimating the lighting parameters quality is suggested. For Chinese cabbage crop the maximum value of this criterion was obtained at the following lighting conditions parameters: PPFD - 500 µmol m-2 s-1, red/white ratio - 1.5, and pulse repetition period - 501 µs.

Optimizing LED lighting for space plant growth unit: Joint effects of photon flux density, red to white ratios and intermittent light pulses.

The aim of this work were to choose a quantitative optimality criterion for estimating the quality of plant LED lighting regimes inside space greenhouses and to construct regression models of crop productivity and the optimality criterion depending on the level of photosynthetic photon flux density (PPFD), the proportion of the red component in the light spectrum and the duration of the duty cycle (Chinese cabbage Brassica сhinensis L. as an example). The properties of the obtained models were described in the context of predicting crop dry weight and the optimality criterion behavior when varying plant lighting parameters. Results of the fractional 3-factor experiment demonstrated the share of the PPFD level participation in the crop dry weight accumulation was 84.4% at almost any combination of other lighting parameters, but when PPFD value increased up to 500µmol m-2s-1 the pulse light and supplemental light from red LEDs could additionally increase crop productivity. Analysis of the optimality criterion response to variation of lighting parameters showed that the maximum coordinates were the following: PPFD = 500µmol m-2s-1, about 70%-proportion of the red component of the light spectrum (PPFDLEDred/PPFDLEDwhite = 1.5) and the duty cycle with a period of 501µs. Thus, LED crop lighting with these parameters was optimal for achieving high crop productivity and for efficient use of energy in the given range of lighting parameter values.

SUBSTANTIATION OF OPTIMAL LIGHTING REGIMES FOR PLANTS IN SPACE GREENHOUSE <>.

A 3-factor experiment with 24-d vegetation of Brassica chinensis L. crops demonstrated the dependence of dry mass yield on lighting regimes provided by a lamp composed of white (color temperature 4000 K) and red (660 nm) LEDs (light-emitting diodes). Experimental data were used to build regressive dependences of plant dry mass and optimal light criterion (product of dry mass and photosynthesis efficiency) on 3 LEDs lamp parameters: photosynthetic photon flux density (PPFD), red and white PPFD ratio, and pulse period. The following LEDs light parameters were found to be optimal for the Chinese cabbage: time-averaged PFD - 500.µmol/(m².s), red and white PPFD ratio - 1.5 and pulse period - 501 ps. Considering the wattage rating for projectible vitamin greenhouse Vitacycle-To, continuous light should have PPFD = 430 pmol/(m²-s), rPPFD/wPPFD ratio - 1.5 and continuous light.