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LEDs: Lighting for Hyperspace Crops or Just Hype?
There has been a lot of buzz surrounding LEDs (Light Emitting Diode) amongst indoor gardeners in recent days. The feedback varies; some people are wowed by this new technology while others are disappointed. So what are some of the reasons for the polar opposite views when it comes to LED lighting for crops?
In this article we will examine some aspects of LED lighting, and perhaps shed a few photons on just what LEDs have in store for the future of indoor gardening. This certainly won’t be this writer’s last article on the subject either, as this emerging technology continues to evolve. As a matter of fact, LED lighting may spur a renaissance for plant production, for some of the reasons that will be explained in further detail through this article.
Firstly, let’s examine the technology itself and then have a look at some practical applications that may change the way people grow under lights forever.
To give a quick glance into the historical background of LEDs, the following has been copied from Wikipedia.org:
The first practical visible-spectrum (red) LED was developed in 1962 by Nick Holonyak Jr., while working at General Electric company. He later moved to the University of Illinois at Urbana-Champaign. [11] Holonyak is seen as the "father of the light-emitting diode." [12] M. George Craford, a former graduate student of Holonyak's, invented the first yellow LED and red and red-orange in 1972 that were 10 times brighter. [13] Until 1968, visible and infrared LEDs were extremely costly, on the order of US $200 per unit, and so had little practical application. [14] The Monsanto Corporation was the first organization to mass-produce visible LEDs, using gallium arsenide phosphide in 1968 to produce red LEDs suitable for indicators. [15] Hewlett Packard (HP) introduced light-emitting diodes in 1968, initially using GaAsP material supplied by Monsanto. The technology proved to have major applications for alphanumeric displays and was integrated into HP’s early handheld calculators.
You may notice that there are some corporate giants that have been involved in the development of this technology, and in the earlier years, at great costs. Regardless of where LED technology originated from, the possibilities continue to grow leaps and bounds. At present day LED lighting technologies are available to home consumers that were once more exclusive to research facilities such as those maintained by NASA.
Now, there has been a lot of work done from using LEDs for numeric displays to bring their luminance levels up and cost levels down to make them practical for horticultural lighting.
Where LEDs differ from conventional lighting sources such as incandescent, fluorescent and HID (high intensity discharge) is that they do not use any filaments, but rather a semi-conductor. The light produced by the individual diodes is extremely efficient in converting energy to light. Conventional lighting actually produces very few photons (light energy) relative to the amount of electricity being consumed. The wasted energy is given off as heat. The fact that conventional grow room lighting typically produces tremendous amounts of heat is indicative of the efficiency of the lighting process.
Whereas, with LED lighting the diodes run extremely cool, although a small amount of heat may be given of the circuitry and driver system.
Have you ever seen a blue HPS (high pressure sodium) lamp? The answer is likely no, and that’s because there are limitations to the spectral outputs of conventional lighting technologies. With LEDs, just about any single wavelength, for example 630 nanometers (red), can be created. The light emitted from the diodes is more vivid, clear and true to specific desired wavelengths versus conventional lighting sources. LEDs use about 1/10th of the power versus conventional lighting sources to achieve optimal results.
The individual diodes can be manufactured to just about any wavelength for output. What’s even better is that instead of trying to make a single diode an “all rounder” for plant growth, you can tailor custom lighting spectrums by blending different diodes that have different spectral outputs.
This is very advantageous, as it allows growers to create custom spectrums for different growth phases and even different strains of plants. One of the areas that LEDs may help to improve is our understanding of just exactly what wavelengths plants need to perform a variety of biological processes and at different phases in their development. Researchers have already been able to determine, using tailored spectrum LEDs, that different species of plants, and even different strains within the species, have different preference in terms of the light wavelengths (i.e. ratios of red to blue, inclusion or exclusion of orange, etc) that are delivered.
The most up-to-date research has been demonstrating the plants need more than just a combination of red to blue diodes to produce stronger flowering and growth responses. Interestingly, it has been held that plants do not use any green light at all.
“These data indicate that GL (green LED light) treated seedlings elongate significantly faster than dark-grown seedlings and are growing three to four times the rate of seedlings receiving high-fluence rate blue light.” 1
What does that mean?
It means that we still have a lot to learn with what plants respond to in terms of lighting, and even more specifically, which wavelengths are preferred by different species for optimum growth and flowering.
This helps make LED lighting technology a vehicle to the better understanding of the crops we grow, and how we can grow them more efficiently.
At present, no single diode will outshine a HID lamp in terms of lumens. However, assessing the relative efficiency of LEDs with lumen measurements is misleading. Lumens measure the relative intensity of visible light, for the human eye, not for the wavelengths plants use in the photosynthetic process. Photosynthesis Photon Flux Density (PPFD) is likely the most accurate way to determine the efficiency of a light source for horticultural applications.
For practical purposes, it would be safe to say the things that growers should love about LEDs is that they are extremely efficient at the conversion of electricity to photons (light for growth), and because they are so efficient, they operate extremely cool compared to HID lighting.
As a grower, could you imagine consuming 1/10th of the power you associate with lighting, while virtually eliminating the need to exhaust or air-condition the growing area? What about replacing the lighting after years instead of months, as with conventional horticultural lighting?
With LED lighting, growers’ dreams can become reality. However, this is where the reader is addressed with caution. The following will provide an outline that makes all of this possible, but with present LED lighting technology featured, it will not produce the heavy yields that HID gardeners are accustomed to. If your expectations are reasonable, and next generation LED lighting is used, you might be very satisfied to produce a small crop to supplement your diet using a minimal amount of power, creating very little heat and doing so relatively quietly and peacefully versus conventional indoor gardening with intensive ventilation or air-conditioning.
The basic model described is capable of providing small crops just about anywhere imaginable. LEDs may allow people to grow where they had not been able to previously. As a matter of fact, the model will consume less than 210 watts of electricity, making it possible to operate on power stored from wind or solar sources.
The enclosure is highly portable, and sets up in minutes. Constructed from highly durable material, this silver lined growing chamber may be moved and re-used with exactly the same set-up, time and time again. The pre-fabricated growing enclosure has a number of great features including:
- sealable passive air intakes
- a multitude of duct ports, adjustable from four to eight inches in diameter, or can be completely shut
- side access ports, as not to disrupt crops
- a durable and light tight wide zippered opening
- waterproof and tear resistant flooring
- a highly reflective specular (textured) covering that helps to diffuse light
- coverings are free of phyto-toxins
The ceiling support members of this chamber are adjustable, allowing you to create the ideal grid for suspension of lighting, sensors, fans and filters. While the improvements allow for a greater weight load, they won’t need to come into play with lightweight and easy to hang LED lighting fixtures.
The structure is ideal, because it helps contain and reflect the light inside. It also prevents light leaks from entering the growing area and interrupting dark cycles, which will delay or impede flowering in some crops.
Best of all, the structure is relatively airtight allowing for efficient supplementation of carbon dioxide (CO2) levels in the growing area. With the slightly less intense, but optimal spectrum light delivered by LEDs, efficiently boosting CO2 levels will help create faster and healthier growth rates.
CO2 supplementation is complicated and expensive, right? Not necessarily. With the amount of air that needs to be exchanged or cooled in conventional HID lit growth chambers, adding CO2 takes some consideration and expense.
However, operating an LED in ambient living conditions does not generate a significant amount of heat, so ventilation and air exchange requirements are greatly reduced. To control the temperature and humidity in the growth chamber, a very small six inch duct booster fan that consumes only 25 watts of electricity can be used. However, the fan does not need to run constant, and can be plugged into a grow room environmental controller that will only activate the fan on rise of temperature or humidity past the grower set point. The fan cycles vary infrequently when the growth chamber is located in normal ambient living temperatures, as very little heat is generated. On average, the inside of the LED growth chamber was not much more than 1.5°F above ambient temperatures.
Because air exchanges are so infrequent, a fermentation process can be used to significantly elevate CO2 levels in the growth chamber without adding any additional heat, with the added benefit of a useable by-product.
In this model, beer was fermented inside of the growth chamber. During the primary fermentation, CO2 levels averaged a whopping 2800 parts per million (ppm) inside of the growth chamber. After the primary fermentation process begins to taper off, levels remained between 900 to 1200 ppm during the secondary fermentation, ideal for most types of crops.
So besides generating beneficial levels of CO2 to boost production levels under the LEDs, a beneficial by-product is also created. In certain situations, the alcohol created through different types of fermentation processes could be refined further and utilized as a fuel source for heating or generating power. As mentioned previously, this growth chamber uses less than 210 watts of electricity, making it possible to run with alternate power sources such as wind or solar. Coupled with the possibility of generating fuel through fermentation, this model has some global sweeping possibilities.
Current research, as cited in this article, has demonstrated that plants and other organisms will do better with a wide band width of available light wavelengths, however, for efficiency, most of the photon energy should be in the blue and red portions of the spectrum. To bring other wavelengths into the growing environment, two to 45 watt compact fluorescents (CFLs) were added to complete the spectrum. One bulb is cool white (blue/white light) and the other is warm white (red/white light). While not added for their intensity, the CFLs are very efficient at rounding the spectrum without adding too much heat and consuming very little electricity. Fluorescents have good lumen per watt conversions.
Some pioneering LED growers have observed that for the reproductive phases in many types of plants, they were able to achieve better results by blending a small portion of fluorescent lighting with the red and blue LEDs. However, the latest high-output LED lighting systems have started to blend a few diodes in the orange and yellow spectrum in their lighting arrays, and prove to be providing better results than just combinations of red and blue alone.
The diodes featured in this article are 0.5 watt diodes, driven to about 0.3 watts of output. Each of the two panels only consumes 45 watts of electricity. Higher output diodes are available, and growers wishing to grow exclusively with LEDs may achieve better results with higher wattage diodes. LED lighting systems are available with one or even three watts of output per diode. These systems are considerably more expensive, but the increase in production capability helps to offset the initial expense. As mentioned, LEDs won’t need replacing for at least 35,000 hours of operation and consume very little electricity relative to the amount of light they can deliver for photosynthesis, helping to recapture the capital outlay over time.
To keep the air stirred in the growing area, a small desk type fan is suspended with an adjustable light hanger, so that it can be set to the ideal height as the crop advances. Vibrations from the fan are minimized because it is suspended by the nylon cord of the light hanger, and the vibrations from the small duct booster fan are minimized by suspension with rubber strapping.
A small carbon filter is installed before the vent/extraction fan to help reduce any airborne contaminates originating from the growing area to enter other areas. Each of the lighting fixtures (two-45 watt CFLs, two-45 watt LEDs) is suspended from adjustable light hangers. The fluorescent and LED fixtures are lightweight, and are extremely easy to position with the adjustable hangers, allowing people with disabilities to easily maintain optimal light levels in the garden by raising or lowering the light fixtures.
Artificial lighting intensity drops relatively quickly with distance traveled, so for the best results in this type of set-up, you will want to cultivate low growing plants with a relatively fast crop turn around time. Radishes, lettuces, herbs and greens would do very well. For higher light plants such as vegetables and fruits, growing dwarf varieties that auto-flower and finish less than 18 inches tall may also be very well suited. Certain varieties of peppers seem to grow very well under LED lights.
As mentioned previously, pioneering growers are finding that different varieties of plants are responding to different balances in lighting wavelengths, so there will be some exciting times ahead for growers as new discoveries are made about your favorite plants.
In closing, here are some of the advantages that this type of LED growth chamber has to offer:
- highly transportable
- requires no frequent replacing of parts such as lamps
- uses less than 210 watts of electricity for a three foot by three foot growing area
- allows for the cultivation of a variety of edible, ornamental and nutraceutical plants
- can be installed quickly, just about anywhere
- sustains good growth rates with elevated CO2 levels and exacting light spectrums
- runs very quiet; no major venting required
- produces alcohol as a by-product of the fermentation process used to elevate CO
- plants consume less water in the LED environment
As LED lighting technologies undergo further development and refinement, their outputs will be increased and with popularity, their purchase price lowered. Some of the most recent developments have LEDs emitting very intense light outputs. However, along with these higher outputs, comes a little more heat, mostly from the driver unit and circuit rather than the diodes
It may be not too far off in the distant future where LEDs that run extremely bright, with customizable wavelengths, using very little electricity and generating virtually no residual heat will be available. At present, LEDs have earned a place in indoor cultivation for propagation, vegetative growth and even for producing flowers and fruits, given the right LED lighting configuration and management.
If these types of growth chambers were produced en masse, bringing their cost down, and supplied with a solar or wind power source, humanity could take a step in the right direction. The combination of technologies has the potential for increasing the quality of life for all the inhabitants of this planet, while reducing our individual carbon footprint on the environment. Look for more to come as this exciting new technology continues to evolve and emerge.
Sources
1 Folta M. Kevin. Green Light Stimulates Early Stem Elongation, Antagonizing Light-Mediated Growth Inhibition. Plant Molecular and Cellular Biology Program and Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611
The Hydroponic Warehouse
Shop 3, 73 Pickering Street, Enoggera
Brisbane QLD Australia
(Opposite Enoggera Bowls Club.)
Phone: +61 (07) 3354 1588 Fax: +61 (07) 3354 3622
E-mail: tonyl@bigpond.net.au
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