When people talk about indoor cultivation and the lamps they use to light up a growroom, some standard words and phrases come to mind. You have terms such as HPS and MH, referring to high-pressure sodium and metal halide bulbs, respectively. You have units of measurement such as wattage, lumens or lux thrown around to describe a particular lamp’s discharge or intensity. Lately, however, there have been a couple of three-letter words that are used more and more with relatively little understanding. But these words (which are actually acronyms for larger phrases) may play an even greater role in what takes place in growrooms in the very near future… Welcome to Part II of our Advanced Lighting Series.

P.A.R.
PAR is a term usually synonymous with golf. But when you look at it in a different light, it can also mean photosynthetically active radiation – and that is a term usually associated with serious cannabis cultivation. In essence, the PAR value is a rating for the amount of usable light that a bulb can emit.

Researchers and horticulturists have figured out that PAR values are higher at the ends of the visible spectrum – that is to say, in the red and blue frequencies (or wavelengths) of light. The basic PAR zone includes most of this visible spectrum, ranging from about 380 to 750 nanometers (nm) in wavelength. Blue frequencies of the spectrum occur at wavelengths around 450 nm, and red somewhere near 650 nm. These wavelengths directly correspond to the amount of photons being sent to the plants, and this, in turn, affects plant processes such as photosynthesis, plant tropism and even stomatal action on leaves (the opening and closing of leaf stomata for respiration).Big-time growers are always looking for ways to tweak, supercharge and optimize their gardens, because they know this leads to superior marijuana. Advantages in light utilization and increased photosynthesis can obviously help create larger yields and more potent buds. The key to remember is that not all light emitted by your bulbs will be usable by your plants. To that end, growers must figure out what spectrum is best for their particular crop.

L.E.D.
The light-emitting diode, or LED, was invented in Russia in the mid-1920’s. You might be thinking: Who cares where it was invented? But the important fact here is when it was invented – nearly 85 years ago.

The point is that it has taken a very long time for this technology to come into use, and these days the most limiting factor with LED’s is still the cost of developing the technology. Manufacturers are just now hitting the market with LED products that are actually precise enough and strong enough to light indoor gardens on their own. In the next five to 10 years – assuming these new LED lamps work well – you can expect to see a huge increase in market volume for LED’s as the cost of this technology begins to go down. With that said, let’s take a look at the basic advantages of LED lights, moving gradually into the more technical aspects.

To start with, LED lamps use somewhere around one-fifth the power of normal high-intensity discharge (HID) lighting. One of our recent test products – the UFO LED, manufactured by HID Hut (and depicted on our February 2008 cover) – uses 90 watts while still putting out just as many lumens as a 400-watt MH bulb. Obviously, this amounts to a pretty big savings in power consumption and electricity costs.

Additionally, LED’s give off a lot less heat than any conventional HID lamp. Gone are the days of air-cooled lighting systems and the necessity for industrial-strength exhaust fans – not to mention showing up on the thermal-imaging screens of narco-copters flying overhead. The latest LED models, such as the UFO, have built-in fans to cool the tiny bulbs, making standard growroom ventilation and air exchanges more than enough to keep room temperatures at optimal levels. Not too shabby.

So what about the spectrum? Well, here’s where the technology side begins to come into play. It’s worth mentioning that each of these little LED’s can cost the manufacturer upwards of $10 each. When you have 90 LED’s in one lamp, things start to get extremely pricey. The key to keeping this cost down is for the manufacturer to choose LED bulbs that will be more cost-efficient for the consumer. The trick, however, is to not compromise on the best spectral wavelength for your plants. As it stands now, the best LED products in stores (and online) can cost between $550 and $650.

Still, while $600 may seem pretty high for a single-unit lamp, the argument for it is simple: Savings in energy consumption repays the cost after only a year of use. Manufacturers understand, however, that unless the results are overwhelmingly positive, many indoor growers will remain wary. Even so, when you factor in the costs of ballasts, reflectors, bulbs and cooling equipment for conventional HID lamps, the price gap closes quickly.

And so spectrum becomes the trump card. Because LED companies can choose diodes based on the color they emit, they can choose the best spectral frequencies for cannabis plants to thrive in. This is a lot harder for HID-bulb manufacturers, although it should be noted that there are ways for them to do so (and this will be covered in Part III of this series). In creating LED products, a compromise is often reached between optimal color wavelengths and cost; this way, the price tag doesn’t become prohibitive, and the plants will grow as well or better than they would under conventional HID lighting.

The UFO, for example, utilizes two spectral wavelengths; one red and one blue. When the lamp was going though its prototype testing, trials found that with the red diodes at 455 nm and blues at 627 nm, some minor stretching occurred during the flowering stage. To combat this, the company tweaked the lamp, stepping up the number of blue diodes from 10 to 20 out of 90. While the company’s founder acknowledges that he would have preferred to use 660s instead of 627s, the cost of doing so would have made the product five times more expensive, and that just doesn’t work for home or hobbyist growers. It has been these types of adjustments (with more to come) that have helped LED’s become viable options for indoor growrooms.

Looking toward the future, it may soon be possible for LED lamps to hit every possible color in the spectrum that a plant could want, and to supply it in the exact amounts that cannabis plants need. But right now, LED’s like the UFO have produced yields similar to or better than their HID counterparts in initial trials (see results in final section), and have simultaneously saved growers money on electricity while adding better security and growroom atmosphere than do standard HPS and MH bulbs.

Extra Perspective from the HT Blimp
To give some added perspective on the sheer costs of developing the LED to its full potential, High Times got an inside scoop on the future of LED lighting straight from China – the hub of LED research, development and production.

Preliminary reports have stated that a diode measuring two by two inches (which is an extremely large diode compared to conventional LED’s) has been manufactured in China and is currently in the testing phase. Approximately a half-dozen of these diodes were created in a clean room, as microprocessors might be, with only a small percentage of them working for a short period of time. Still, the 200-watt diode, which is a blue, phosphor-coated bulb, reportedly emits 200,000 lumens!

While the cost of materials and actual construction are negligible, the research and developmental costs for this project have been estimated at 60 million yuan, or $8 million – over $1 million per diode. As always, once mass production starts, the cost of these diodes will drop fast… but starting at a million per, it’s going to be at least 10 years before we see anything like that in a growroom.          

Spectral Comparisons by Bulb
All plants absorb light via pigments such as chlorophyll A, chlorophyll B and carotenoids. This light energy, also known as photons, is converted into usable plant energy by the excitation of electrons within the plant cells. This energy becomes the major catalyst in photosynthesis. Without this energy, the plant would be unable to produce food for itself and grow. Without this energy, there would be no buds or resin production of any kind.

The graph shows the absorption rates of two separate pigments (chlorophyll A and B) and breaks down the absorption spectrum by wavelength or color. With this knowledge, it is much easier to see the importance of providing proper spectrum for indoor marijuana gardens. As a guide to better understanding what bulbs can and cannot supply, we have compiled a few graphs to illustrate some of the more prominent bulb types on the market today (see figures 1.2, 1.3 and 1.4).

One important characteristic that isn’t displayed on these charts, however, is the power of the light emitted. Ironically, the bulbs with the best light spectrum are actually the weakest in terms of strength. In fact, a regular incandescent household light bulb actually has a superior spectrum compared to HPS or MH bulbs, but the power just isn’t there. When bulbs lack the strength for their light to penetrate or even reach garden canopies, their value becomes limited.

Bulbs must be able to deliver their light to cannabis gardens with a force as close to the sun’s natural power as possible. Unfortunately, bulbs like fluorescents or incandescents are only strong enough for supplemental lighting, or for use in nursery lamps when baby clones are still rooting. Using lights that aren’t powerful enough for adults will result in spindly, leafy plants as their branches stretch to gather more light.

Another important consideration regarding spectrum involves using supplemental lighting to compensate for the lack of a full spectrum. A well-known experiment conducted in 1950 by Robert Emerson led to the discovery of what we now call the Emerson Enhancement Effect. In principal, the effect states that when shorter wavelengths (i.e., blues or oranges) are supplied along with the longer wavelengths (such as reds at 690 nm and higher), absorption and photosynthesis occur at a faster rate than the sum of both colors acting alone. The reason this happens is because separate photosynthetic processes, called photosystems, occur within the leaves and are related to the specific leaf pigments discussed above.

As research progressed, it turned out that these systems can work together within leaves and that each actually works better when functioning together. Thus, it may be best for indoor growers to mix opposing wavelengths when supplementing gardens rather than use the standard HPS/ MH mix. Looking at the spectral coverage of various bulbs, we notice that fluorescent bulbs are an excellent option for supplemental light. Many people first thought that LED’s would also be a great source of supplemental light, but as developments continue, some are now claiming that they may be the next all-in-one lamp. With prices dropping in LED technology, more manufacturers like HID Hut will be able to produce fuller-spectrum LED lights, making the future even brighter than we might have anticipated.

Inside LED’s
Electroluminescence (EL) is both an optical and electrical phenomenon in which light is emitted by a material in response to an electric current being passed through it. LED’s emit a form of EL using a semiconductor diode, as compared to the light emission resulting from heat or incandescence (such as in a standard household bulb), or from the action of chemicals or chemoluminescence (as in HID bulbs like HPS, MH and mercury vapor).

The specific colors emitted by LED’s depend upon the type of semi-conducting material inside the diode. The colors of light from an LED can be of the visible spectrum, but they can also be infrared or near-ultraviolet as well. As mentioned earlier, LED’s can even be manipulated to give off white light, which is the light created through the combination of all the colors of the visible spectrum. Sometimes bulb manufacturers put various types of coatings on their bulbs to achieve white light, but LED’s can combine different color diodes to produce this same effect. Blue diodes can be added to red and green LED’s to create a fuller spectrum and make a whiter light. Whiter-light-emitting bulbs, such as fluorescents, are obviously a better choice for indoor gardens because of their fuller spectrums. The only question then is whether or not the light source is strong enough to deliver that spectrum to the plants effectively.

An Electro-Illuminant Future?
And that’s the million-dollar question: Are LED’s the wave of the future? Obviously, there are big savings in power usage as well as heat production, and overall security is enormously better. But will they yield bigger? Will they yield super dank? We’ve presented all the facts, but ultimately the answer to that can only be determined by you. In case you’re still having trouble figuring it all out, here’s a few more facts straight from the High Times Cultivation Labs:

In three separate trials, a high-powered LED (prototypes of HID Hut’s UFO) was run in side-by-side experiments – once against a 400-watt MH bulb, once against a 400-watt HPS bulb, and once against a 600-watt HPS bulb. These trials used exactly the same conditions on both sides of the fence. The plants were cuttings taken from a single mother; the medium and grow systems were the same; and the nutrients and atmospheric conditions were kept identical. The only variable was the lamp provided. And, as usual, the results varied.

In Trial A, the clones were placed in a three-by-six-foot box that was divided evenly in half. An ebb-and-flow table on each side shared the same grow medium and reservoir. In the end, the LED lamp yielded 12% more than its counterpart, the 400-watt MH.

In Trial B, similar systems again pitted the UFO against a 400-watt HPS, only this time the LED side took an extra week to finish. Some concern arose over stretching, as the clone grew to touch the UFO. This resulted in a decision to increase the blue diodes in a second prototype, and it may lead to an increase in wavelength for the red diodes, according to the manufacturer. In the end, the LED side yielded 5% less than the HPS side did.

However, it was reported in Trial B that there were markedly different potencies, with the LED plant producing much more resin. Speculation exists that the shortage of wavelengths aided in this process, as abnormal stresses have been known to increase the production of resin glands. Final calculations taking into consideration the extra week of flowering time on the LED side found that in terms of grams yielded per kilowatt hour (KwH) consumed, the HPS yield was one-fourth that of the LED side.

In Trial C, the grower found similarities to both previous trials. While the LED yielded less than its counterpart, this test pushed the limits of the LED by pitting it against a stronger 600-watt HPS bulb. Resin production on this Cali-O strain was up after just four weeks of flowering, but in the end, the yield was around 20% less. However, the grower did note that the amount of money saved in electric costs compared against the costs of the 600-watt HPS was almost enough to offset the profits lost on yield. An interesting side note in this trial was that the plant on the LED side needed considerably less watering than the plant on the HPS side. It is possible that this is due to lower surface temperatures in the soil medium, or because the plant wasn’t driven as hard and thus drank less.

Anyway you slice it, this one’s a real mind-bender. Given the possibilities for vast improvements down the line, the LED revolution could very well be underway already. Will the LED Zeppelin (or the UFO) take off and change the world? For the present, things are certainly looking up.