ARTIFICIAL LIGHTING
here’s no doubt the indoor farming
industry is growing. Each month,
new farms enter the industry, new
technology increases production
efficiency and food quality, and
hundreds of research projects are
conducted around the world. A
hallmark of this industry growth are the
developments in artificial lighting for
indoor farms, namely in LED lighting.
As technology advances rapidly, our
knowledge of how to use it to its
maximum effect is trying hard to keep
up. But let’s start with the basics:
PLANT & LIGHTS: THE BASICS
Light is emitted both as waves and
particles. To be more precise, light is
emitted as waves of photons, which
are essentially bundles of energy. A
specific number of photons can be
measured as a mole: 6.023 x 1,023
particles. The amount of energy
in each photon determines the
length of the wave from crest to
crest. While wavelengths can vary
from nanometers to meters, plant
pigments can only use specific
wavelengths. Most of those useful
wavelengths occur between 400 and
700 nm on the spectrum.
RADIO
MICROWAVE
10 m
10 cm
Growers should strive to match
the needs of their plant as closely
as possible with their light while
considering things like cost and
efficiency (spreadsheets can be
extremely useful to this end). Light
efficiency is the amount of light the
plants can use for every watt or kilowatt
of electricity that is used. PAR, or
photosynthetically active radiation,
is the most useful light to the plant.
Plant pigments absorb light at specific
wavelengths and use the energy in
photosynthesis. The three main
pigments growers deal with are:
1. Chlorophyll a –
2. Chlorophyll b –
Absorption peaks
at wavelengths
around 453
and 642 nm
Light intensity is commonly measured in
three ways: luminosity, PAR and PPFD.
Luminosity (or lumens) is a measure
of how bright a light appears to the
human eye. It is not limited to useful
light. As a measurement for grow light
intensity, luminosity holds little value. If
the wavelength is known, however, it is
possible to convert luminosity to PAR.
.5
Absorption peaks
at wavelengths
around 450
to 454 nm
0.3 mm
LIGHT INTENSITY: USEFUL
MEASUREMENTS OF LIGHT
0
3. Carotenoids –
400
450
500
550
600
650
VISIBLE
780 nm
ULTRAVIOLET
380 nm
10 nm0
X-RAY
GAMMA-RAY
.01 nm
0.000001 nm
“Light efficiency is the amount of light the plants can use
for every watt or kilowatt of electricity that is used.”
140
Maximum Yield USA | June 2016
700
wavelength (nm)
INFRARED
1 mm
The most absorbed wavelengths occur
around 450 and 660 nm.
1.0
Absorption peaks
at wavelengths
around 430
and 662 nm
absorption
T