June 2019 - 18

DUETS
referenced your engineering perspective of how LED fixtures offer adjustable
spectrum. You helped us understand that manipulating the red-blue ratio
requires one or both of the following features. Either extra red and blue
diodes need to be on board a fixture for occasional use to maintain overall
intensity or diodes of the 'other' color need to be powered down lowering
the fixture's overall efficiency. Both options are wasteful as diodes are either
not in use or powered less than optimally.
Alex: This continues to be an ongoing design challenge for adjustable
spectrum fixtures. Eric Runkle has offered great advice when considering
targeted (red/blue) fixtures versus broad spectrum (white LEDs). For
indoor growing without sunlight spectrum matters for plant health. For
greenhouse growing, spectrum is less compelling because the primary
photosynthetic driver is the sun. In my opinion, this advice applies to the
adjustable spectrum feature. Value of adjusting colors can be derived
indoors, in a greenhouse system it's more difficult to justify given our
current knowledge.
Figure 1. Broad spectrum white LED fixture designed to perform in the
same setting as a traditional HID fixture.
Alex: LED fixtures are exciting. LEDs have created a new technology
platform for designers and researchers, resulting in an expanding range
of options for growers. LED technology is driving important conversations
around spectrum, energy efficiency and advanced control systems;
features that can improve business and crop performance.
LED technology is expensive. In contrast, HID pricing is at an all-time
low. This has created a market where growers are hesitant to transition
to LEDs. They are aware that the performance of LED fixtures is rapidly
increasing while the prices continue to fall. But even with this awareness
growers feel comfortable with the use and cost of HID fixtures.
I do, however, see a change coming. The LED market has traditionally
been dominated by red/blue diode fixtures. We are now seeing companies
move toward designs that contain broad spectrum white diodes. An
advantage of white diodes is that they are more cost effective than
discrete color diodes.
This design transition is an encouraging sign that lighting companies
are working to find a balance between plant specific spectrums and price.
I think of this as an inflection point in how we think about light. When
LED pricing aligns with HID, I'm confident we'll see a full market transition.
I now see a general market consensus where growers acknowledge that
" LEDs are the future, " but the pricing is holding people back.
Peter: An analogy that resonates with me is how quickly I approached
and crossed the inflection point you cite in thinking about my residential
lighting. It took a couple years for me to convert my incandescent bulbs
to compact fluorescent bulbs a decade ago. It was the high cost of the
new bulbs relative to cheap incandescent bulbs that slowed my transition.
A couple years later, I replaced every compact fluorescent bulb, long
before its performance expired, with an LED to complete my upgrade.
Once I crossed my inflection point the second transition occurred in the
blink of an eye, no turning back.
Your point is a crucial one in the debate and speaks directly to LED
technology versatility and application flexibility. In just a few years we've
progressed from being mesmerized by LED potential for tailored spectrum
and variable intensity to understanding its capability to deliver basic,
white light economically (Figure 1).
In an earlier Duets article with Erik Runkle (https://gpnmag.com/article/
supplemental-and-sole-source-led-lighting-fast-and-furious-change/), I
Peter: I sit on a technical advisory board for a medical cannabis
operation and our semi-annual meetings continue to include discussion
about how the growers should be looking at LED technology to
enhance or replace traditional HID use. What are you seeing in the
cannabis industry?
Alex: The price of cannabis is dropping. Growers are feeling the
pressure to lean-out operational costs and deliver unique, high value
product. LEDs can help in a few ways. First, the improving efficiency
of LEDs over HID will allow indoor operations to reduce their lighting
and HVAC electrical demand. Secondly, LED fixtures can give indoor
cannabis growers a new tool kit to promote high value characteristics
from their crops. This will be done through LED spectrum selection and
intensity control. While indoor cultivation will always be a segment of
the cannabis market, I see the majority of future cannabis being grown
in greenhouses or fields. In those production environments, broad
spectrum white will work.
Peter: You're also working with vertical farms. How does that sector's
inflection point compare to cannabis?
Alex: That's an interesting comparison. Pre-legalization, cannabis
cultivation was primarily an indoor activity. Cannabis growers in legal
states can now transition to greenhouse and field operations as ways to
reduce cost. In contrast, the vertical farm sector, by definition, is indoors,
adding to the production costs. The primary justification I see for adding
this expense is food security. During the short time, I've been working
with vertical farms, the U.S. has encountered multiple incidences of e
coli where all of the field grown crops had to be removed from grocery
store shelves. I think the interest and market for indoor grown food will
continue to grow in a way that complements traditional agriculture, but
does not overtake it.
Peter: Thanks for sharing your experience with us Alex, having a
lighting engineer's perspective is valuable, especially one who's made
the effort I've seen you make to understand the horticulture industry.
Growers appreciate hearing that they can avoid the confusion that
spectrum adjustment and intensity control bring to their business
decision. Until those features are fully researched broad spectrum,
basic white LED light offers them an attractive opportunity.
18 JUNE 2019 GPNMAG.COM
https://www.gpnmag.com/article/ http://www.GPNMAG.COM
June 2019

Table of Contents for the Digital Edition of June 2019
