Pulsed LED-Lighting as an Alternative Energy Savings Technique for Vertical Farms and Plant Factories

Ernesto Olvera-Gonzalez,Eric Obeng,Victor Castaño,Deland Myers,Peter Ampim,Daniel Alaniz-Lumbreras,Nivia Escalante-Garcia

doi:10.3390/en14061603

Abstract

Different strategies are reported in the literature for energy saving in Closed Plant Production Systems (CPPS). However, not reliable evidences about energy consumption with the use of pulsed LED light technique in lighting system available in Plant Factory and Vertical Farm. In this work, three key points to determine the effects of pulsed LED light versus continuous LED light are presented: (1) A mathematical model and its practical application for stabilizing the energy equivalence using LED light in continuous and pulsed mode in different light treatments. (2) The quantum efficiency of the photosystem II was used to determine positive and/or negative effects of the light operating mode (continuous or pulsed) on chili pepper plants (Capsicum annuum var. Serrano). (3) Evaluation of energy consumption with both operation modes using ten recipes from the literature to grow plants applied in Closed Plant Production Systems, different Photosynthetic Photon Flux Density at 50, 110, and 180 µmol m−2 s−1, Frequencies at 100, 500, and 1000 Hz, and Duty Cycles of 40, 50, 60, 70, 80, and 90%. The results show no significant statistical differences between the operation modes (continuous and pulsed LED light). For each light recipe analyzed, a pulsed frequency and a duty cycle were obtained, achieving significant energy savings in every light intensity. The results can be useful guide for real-life applications in CPPS.

Highlights

LED lamps have been demonstrated a versatile illumination source to grow plants in controlled environments agriculture systems, as a supplemental lighting for greenhouses [1,2], replacement of sun light in growth chambers, growth rooms, indoor vertical farms [3,4,5,6], for the crop production in space [7] and as plant factories [8,9,10,11,12]
The φPSII parameter evaluated in the statistical analysis for both light operation modes (ANOVA) indicated that there are no significant differences
The data shown in the results section indicated the magnitude of this proposal, as a first step, the positive and/or negative effects on plants were evaluated when exposed to the operation modes of artificial LED light

Summary

Introduction

LED lamps have been demonstrated a versatile illumination source to grow plants in controlled environments agriculture systems, as a supplemental lighting for greenhouses [1,2], replacement of sun light in growth chambers, growth rooms, indoor vertical farms [3,4,5,6], for the crop production in space [7] and as plant factories [8,9,10,11,12]. Energy consumption of artificial light sources in Closed Plant Production Systems (CPPS), such as greenhouses, vertical farms, plant factories, or even for plant growth systems, outer space [10,26,27], contributes to about 30% of the total cost of production [28]. Several light sources have been evaluated for different CPPS, namely, filament lamps and gas discharge lamps with mercury and sodium [30,31]; LED technology improved lamps with a longer lifespan and lower energy consumption [5,32,33]. Important advantages of LED lamps include the application of light in specific bands (λ) of the light spectrum which reduces energy consumption considerably, and the creation of possibilities to match the specific plant light requirements [34,35]

Methods

Results

Discussion

Conclusion