From a marketing point of view Induction lamps have taken a back seat to LED lamps when it comes to what the LED lamp manufacturers are doing to promote the use of their lights for area and grow lighting applications. Their spectacular claims as what a particular brand of LED grow lamp can do to increase yields by providing high energy lumen output, at lower wattages, lower temperatures, longer lifespans and PAR specific spectrums that conventional grow lights do not deliver on would appeal to anyone interested in bringing the best light to their plants at the savings being described.
The LED's Dark Secret
The blue light-emitting diode, arguably the greatest optoelectronic advance of the past 25 years, harbors a dark secret: Crank up the current and its efficiencies will plummet. The problem is known as droop, and it's not only puzzling the brightest minds in the field, it's also threatening the future of the electric lighting industry.
Since none of the LED marketing materials ever addresses the cost of buying an LED grow light or for that matter induction grow lights as an alternative let's examine the science instead of the hype.
LED LAMP LIFE: Most LED grow light manufacturers will claim their lamps will last for a 50,000 hour lifespan. We've even seen others that have advertised 100,000 hour lifespans. To that I can only say that Chinese made LED lamps have had a poor track record in meeting the advertised lifespans, when they fail early the warranty claims tend to be denied and blamed on a customer responsible heat management issue and the accuracy of their specification or ‘white' sheets is not always reliable.
So if an LED lamp is going to survive 50,000 hours then this is what it must weigh its claimed life spans against:
For the grower to make an informed decision regarding the lifespans of that particular manufacturers LED lamp, they'll want to identify two things from the white sheets and having been confirmed by independent testing labs;
(L70) What is the Lumen Maintenance Level? This will be expressed as the L70 measurement and will be represented in hours and is the point where the LED lamps are giving off only 70% of their initial lumen output when new. Below this point they are considered 'failed' and should be replaced.
(B50) What is the failure (mortality rate)? This is a statistical measurement of when 50% of the new LED lamps have fallen below the L70 lumen output threshold levels.
As a rule; the harder that you drive a LED the shorter its L70/B50 life will be as the higher temperatures lead to shorter lifespans. This is a hidden cost that one must consider when making a long term capital investment in an LED lighting system that costs around $5 per watt.
When an LED does fail it affects your plants health with lighting downtime. To keep the downtime to a minimum and to get the LED grow lights back on the plants you have options; make the repairs yourself or return it to the manufacturer for the repair.
If you have a replacement LED lamp and are able and willing to replace the failed lamp, which has been soldered onto the fixtures heat sink, then you'll have limited some of your down time while you install the replacement LED lamp.
Otherwise you'll be sending the entire fixture back to the manufacturer and if it's still within the warranty period, would hopefully make the timely repair or replacement without having to ‘regretfully inform you that the fixture is no longer within warranty period' or determine ‘customer responsible failure not covered under warranty'.
Of note: on March 18, 2010 the US AIR FORCE issued a memorandum in which they removed LED lamps as an option for energy retrofit area lighting projects as a result of many of the LED installations having proven themselves to not have delivered sufficient lumen levels and not having met the published L70 and B50 standards within previous installations.
THE IMPORTANCE OF BIN CODES
If you ever have to order LED replacement lamps it's important you have an understanding of LED BIN CODING as this is how the lamps are rated for color, efficiencies, forward voltage, and flux ratings.
This is important because you will pay a more for an LED lamp that operates with 25% efficiency then one that operates at 15% efficiency. Dealing with an understanding of Bin Coding is your only hope that the same lamp you ordered one day will be the same lamp you get upon a reorder.
LOWER OPERATING TEMPERATURES
Another claim we've seen from some of the LED grow light manufacturers is that LED lamps put out no heat. This is simply not true. There is no denying the basic laws of thermodynamics. Very little (20%typically) of the LED lamps energy is utilized for actual light. The rest is trapped as heat within the lamp housing. High Power LED arrays are either air or water cooled and the LED lamps will be mounted on an aluminum heat sink to transfer the heat away from the lamp.
The amount of heat generated by an LED is also directly proportional to the LED power levels. If you want to prove this to yourself try taking a Low Power 5mm LED array, wrap them in a towel and see how will quickly they'll heat up since the heat would have nowhere to go. So while an LED won't run as hot as an HID they do create heat and that heat has got to be evacuated from the LED or they go ten toes up.
LED PAR SPECTRUMS
If you still wish to consider LED lights because the manufacturer claims they make lights which are better tailored for plant growth. They'll claim their LED lights are 20 times better than conventional grow lights. Or that LED will deliver the narrow and exact spectrums for maximum PAR for plant lighting. No wasted spectral energy. Then we really need you to understand about how an LED interacts with your plants both photosynthetically and during photomorphogenisis.
Let's take a look at some of the LED manufacturers claim that the advanced technological advantages of using LED over a traditional HPS for flowering and bud is a result of the LED lamp arrays delivering the narrow maximum PAR absorption spikes for chlorophyll A (430-670 nanometers) and chlorophyll B (450-640 nanometers) that the traditional HPS does not.
If you were to just take the LED manufacturers spectral analysis at face value you would see that the LED lamp they designed for this stage growth does fall within the ranges of the CHLOROPHYLL ABSORPTION CHARTS. So while it is true that LED lamps can provide the specific concentration wavelengths (650-670 nm) of that of a traditional HPS grow light, the manufacturers use of this as evidence that it is this narrow spectrum which the LED emits as critical for plant growth is at best sporadic and tends to be mentioned only when it's in the commercial advantage of the proponent.
But there is a problem with the claimed advantages of narrow spectral emissions during the plants later stages and those of you who have experimented with LED lamps have encountered them. It's actually a result of the narrow LED spectral properties that plants experience photoinhibition which contradicts the specific concentration wavelength advantages of the LED grow lamp.
Studies such as the Emerson Effecthave shown that a wider spectrum lamp for this growth stage, such as an HPS lamp, does emit a broader spectrum and the plants will take full photochemical advantage of the photosynthetic and photomorphogenesis processes from the traditional HPS source that are not available to them under the narrow spectrum LED grow light.
The other problem for the LED manufacturers when only relying solely on the chlorophyll absorption charts are that they are levels set for isolated chlorophyll molecules suspended in a solvent and do not reflect total photosynthetic activity. Even within the Chlorophyll Absorption Charts different solvents will give slightly different numbers.
So what the grower would really want to know would be the NET PHOTOSYNTHESIS or Action Spectra of the plant receptors by the light source. When you refer to LAND PLANT ACTION SPECTRA (Algae Action Spectra charts are different) you'll see the relative results and not absolute absorption values. These values are considered normalized so that the lighting spectrum that is most efficient in photosynthesis is at 100% for that plant species. This does not mean that 100% of that lighting spectrum is used in photosynthesis. It is only 100% compared to other lighting spectrum.
LED manufacturers who rely solely on Chlorophyll Absorption Charts and don't reference Net PhotosyAction Spectra data or accept the Emerson Effect do so because it's not in their best commercial interest to do so.
LED DISTRIBUTION VS INDUCTION
LED lamps are highly directional with vertical beam spreads between15 – 50°. To illustrate the intensity of the LED one need only look directly into an LED or as you see LED sign on the side of a freeway at night, how long did it take you to recover your full vision once you looked away from the LED source?
LED grow lamp plants also suffer from their narrow vertical beam spreads with lack of CANOPY PENETRATION. The angle of light at the plants is an important consideration since the rays of sunlight nearly parallel by the time they reach an outdoor plant due to the distance between earth and sun. This means that a 6 ft plant will be illuminated equally from top to bottom outdoors insuring dense growth and high yields. While not accomplished by nature of the LED design it is normal for an INDA-GRO Induction Grow Lamp to achieve canopy penetration of 30” and more.
PHOTOMETRICS is then how we refer the light distribution levels of any fixture/lamp combination. This is an important relationship because it will determine how much of an area a given fixture will light as it correlates to either visible distribution levels or plant lighting (PPF, YPF, PAR lp/w) values and the efficiency of the light source.
Proper lamp selection itself would be the first thing that determines the quantity of light energy reaching the plant but it's important that the levels being considered have been taken with the selected lamp and the fixture combined for what's referred to the IN SITU levels. In situ is a Latin phrase used in the lighting industry that stands for ‘in place'. In situ measurements are the only way to accurately measure in a surface point by point value how efficient the total lamp/fixture package will be to the customer.
In situ measurements will also depend on such factors as the housing materials and design, color, reflective materials and shape within the fixture, and lens design will all come together to perform in meeting your plants large area coverage needs. It's not unusual for identical lamp/ballast combinations to measure widely different In situ photometric values dependent upon how the manufacturer dealt with the design and materials quality of the fixture they developed.
Now let's look at how much PLANT LIGHTING will be needed and how that measurement is different than how we measure light for human vision.
One of the ways we measure the quantity of light reaching the plant is in the PHOTOSYNTHETIC PHOTON FLUX values. Let's take a look at a 100 watt LED lamp putting out lighting levels of roughly 100 umol/sec (mol is pronounced micro mole and describes the amount of photon packs striking a square meter every second). So just how far will that 100 umol/sec of light get you? Well, to put it into perspective, full sunlight is 2000 umol/meter^2/sec (2000 umol per square meter per second), the photo saturation point for many food crops is around 1000 umol/meter^2/sec and most food crops thrive at 500 umol/meter^2/sec especially in flowering. The answer for the 100 watt LED light at an intensity of 500 umol/meter^2/sec is roughly two square feet. So while the 100 watt LED lamp can definitely grow in a larger area the rate of photosynthesis will proportionally go down.
As the cost of electrical energy costs continue to rise, the commercial grower needs to have considered how the efficiencies of his grow lights when considering photometric In situ values, high power factor, low total harmonic distortion, and daylight harvesting control features can significantly reduce those monthly operational costs. Induction grow lights score well in all of these areas.
And while you might take from all this that we're entirely down on using LED lighting that is not entirely the case. We've found it worked well for clone and vegative stages but for the customer to make a fully informed decision to use LED you need to know the lifetime operational and economic benefits of selecting LED for these processes. However we believe that once you remove the hype surrounding LED grow lights you'll choose our Inda-Gro Induction Grow Lights.