Light emitting diode (LED) Lighting for Greenhouse Crops

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Cleopatra Todd
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1 Light emitting diode (LED) Lighting for Greenhouse Crops A.J. Both Associate Extension Specialist Dept. of Environmental Sciences Electromagnetic radiation spectrum 1

2 Why do plants need light? Photosynthesis (growth and development) Other processes: Photoperiodism (daylength) Photomorphogenesis (light affects shape) Phototropism (sunflower) Photodormancy (seeds) Note: Without the ability of plants to convert light into biomass, many living organisms would not survive on our planet, including us! Relative Quantum Efficiency and Eye Sensitivity R = O = Y = G = B = I = * 435* V = Photosynthetically Active Radiation (PAR) nm *Disputed (CRC Handbook of Fundamental Spectroscopic Correlation Charts. CRC Press, 2005) 2

Light, sensors, and units Light: Visible (380 770 nm) PAR (400 700 nm) 380 Sunlight (280 2,800 2 800 nm) Sensors: Foot candle or Lux meter (visible) Quantum

3 Light, sensors, and units Light: Visible ( nm) PAR ( nm) 380 Sunlight (280 2, nm) Sensors: Foot candle or Lux meter (visible) Quantum sensor (PAR) Visible 400 PAR ft cd = 1 lumen/ft 2 1 lux = lumen/m 2 1 ft cd = lux Pyranometer (sunlight) Units: ft cd or lux µmol/(m 2 *s) or mol/(m 2 *d) (recommended) i.e., instantaneous or integrated (DLI) W/m 2 (note: radiant Watt, not electric Watt) 770 Preferred light sensors (horticultural applications) Quantum sensor ( nm) measures PAR Pyranometer (280 2,800 nm) measures solar radiation 3

Daily light integrals for Newark, NJ 70 1980 1981

Average Daily Total Radiation (mol/m²d) 60 50 40 30

4 Daily light integrals for Newark, NJ Average Daily Total Radiation (mol/m²d) Julian Date Data source: National Renewable Energy Laboratory Average daily light integrals Dr. Jim Faust, Clemson University 4

Supplemental lighting (promote photosynthesis)

Improves croptiming But: Impacts other crop production

: Environmental control Irrigation and fertilization

greenhouse energy use Inverse square law Light

5 Supplemental lighting (promote photosynthesis) Benefits: Improves crop production (quality, duration) Improves croptiming But: Impacts other crop production systems, e.g.: Environmental control Irrigation and fertilization Increases capital investment Increases overall greenhouse energy use Inverse square law Light intensity is inversely proportional to the square of the distance from the source 100% 25% 11% 6% 4% 5

Common supplemental light sources: Incandescent (photoperiod control)

(HID): High Pressure Sodium (HPS), yellowish light Metal Halide (MH),

to HPS: More blue light (plant development) Shorter lamp life (6,000

6 Common supplemental light sources: Incandescent (photoperiod control) Fluorescent (growth and germination rooms) High Intensity Discharge (HID): High Pressure Sodium (HPS), yellowish light Metal Halide (MH), white light Light emitting diode (LED), new technology (R&B) MH compared to HPS: More blue light (plant development) Shorter lamp life (6,000 versus 16,000 hrs) Less efficient (25% versus 30%) Incandescent (photoperiod) lighting 6

7 Photoperiod lighting with LEDs Image courtesy of Philips Lighting, Fluorescent 7

8 LED lighting in a multi tier germination facility Image courtesy of Philips Lighting, High pressure sodium 8

9 Mixed mode: Metal halide and high pressure sodium LED lighting (horizontal arrays 9

10 LED lighting (vertical arrays) Spectroradiometer 7 6 Intensity (µmol/(m² ²s)) Wavelength (nm) 10

Spectral output of various lamps 1.0 0.8 INC 1.0 0.8 MH Photon Flux Normalized P 0.

0 350 400 450 500 550 600 650 700 750 800 Wavelength (nm) 0.

8 HPS 1.0 0.8 Blue LED Red LED Normalized Photon Flux 0.6 0.4 0.

11 Spectral output of various lamps INC MH Photon Flux Normalized P Photon Flux Normalized P Wavelength (nm) Wavelength (nm) HPS Blue LED Red LED Normalized Photon Flux Normalized Photon Flux Wavelength (nm) Wavelength (nm) 11

Integrating sphere (ø 76 or 2m) (Ulbricht sphere) Lamp under test (DUT) Baffle Detector Auxiliary lamp Evaluates self absorption characteristics of DUT Spectral radiant flux Units: W/nm 4π geometry

12 Integrating sphere (ø 76 or 2m) (Ulbricht sphere) Lamp under test (DUT) Baffle Detector Auxiliary lamp Evaluates self absorption characteristics of DUT Spectral radiant flux Units: W/nm 4π geometry Spectroradiometer Inside of the sphere reflects and uniformly diffuses light (the surface is considered Lambertian; coated with a BaSO 4 compound) Test lamp surface area should be <2% of sphere surface area Maximum test lamp characteristics: 51 (1.3 m) long, 5,000 W power Questions regarding horticultural applications: Testing compliant with LM 79, LM 80? Q: PAR instead of visible light measurements? L 70 (TM 21 compliant)? Spectral output ( nm)? PAR distribution (at a specific mounting height)? Conversion efficiency (μmol/j)? Experience from commercial installations? System warranty? Q: Do we need our own Lighting Facts Label? 12

13 Multiple light sources Sunlight (overhead) HPS (overhead) LED (intracanopy) How best to characterize the plant light environment? Image courtesy of Philips Lighting Thank You! Questions? 13

Here is a glossary of terms about Lighting that is great knowledge to understand when growing cannabis, whether indoors our outside in a greenhouse.

Here is a glossary of terms about Lighting that is great knowledge to understand when growing cannabis, whether indoors our outside in a greenhouse. AMPERE (AMP) - The unit used to measure the strength