ARTIFICIAL LIGHTING
“While LEDs do reduce the cost of heat removal, the cost still
exists and increases as growers increase growing density.”
Replacement and disposal costs,
along with fragility and a nonspecific spectrum have limited
the use of fluorescents in larger
indoor operations.
manufacturing, low operating costs
and spectrum specificity tip the scales
in favor of LEDs for indoor growers.
Induction lighting is similar to
Since more and more growers are
choosing LEDs to light their farms,
and more manufacturers are entering
the LED space, a guide to understanding LEDs will benefit growers.
fluorescents. It uses magnetic fields
rather than filaments to produce light.
Induction lights have long lifespans
and moderate efficiency. They have
yet to find significant traction in the
farming industry.
LEDs belong to a rapidly growing
industry with continually decreasing
costs. Benefits such as ruggedness,
efficiency, dropping costs of
A FOCUS ON LEDs
ANATOMY OF AN LED
A light-emitting diode is a device that
emits light as one specific wavelength
when energy passes through it. Two
types of materials, each a different
diode
lens
plastic shell
energy
released
as light
photons
kind of semiconductor, are joined,
creating the diode. Each of the
semiconductors in the diode has a
different charge—one semiconductor
is negative and one is positive. When
energy passes through the combined
semiconductors, the electrons in
the negative semiconductor and the
“holes” (positively charged carriers)
in the positive semiconductor are
activated. The negatively charged
electrons in one semiconductor slam
into the “holes” (which are positively
charged) in the other semiconductor.
Since the positive and negative charges
aren’t perfectly equal, they cannot
perfectly cancel each other out. The
excess energy has no place to go, and
it is emitted as photons of light.
The type of each semiconductor
determines exactly how much excess
energy there is, and as we know,
the amount of energy in a photon
determines wavelength. Therefore,
each light-emitting diode emits one
particular wavelength of light. The
diode is packaged as a chip and
encased in a plastic cap. Diodes are
usually batched with other diodes that
emit the same (or close to the same)
wavelength of light.
CHOOSING AN LED LIGHT
holes
electrons
144
Maximum Yield USA | June 2016
junction
Choosing LED lights can be a
slow and confusing process. There
are many different variations of
fundamentally similar products. To
compare products, you’ll want to
understand efficiency, form factors,
heat outputs and warranties.