The artificial light source in an indoor marijuana garden is arguably the single most important piece of equipment in terms of a garden’s overall efficiency. It is the artificial light source that single handedly powers photosynthesis in an indoor garden. In other words, the lighting system(s) used has the most influence over plant growth in the garden and the garden’s overall yield. The lighting system(s) is also the piece of equipment that usually draws the most electricity.
After a grower has harvested a crop, he or she can measure the garden’s efficiency in a ratio of the weight of dried marijuana and the total electrical draw (watts). This efficiency calculation can also help a grower determine their return on total investment. After all, once the initial cost of the equipment has been recouped, the efficiency of a garden’s lighting system is the main determining factor in a grower’s return on investment for each garden cycle. As more and more commercial cannabis operations are established, there will be an even greater importance placed on efficiency. As competition increases, growers who want to stay in the game will have to use the most efficient lighting systems available. The three newest technologies that offer heightened efficiency and performance for growing marijuana are: induction lighting systems, double ended HID systems with square wave technology, and chips on board (COB) LED systems.
Induction lighting or electrode-less lamps are gas discharge lamps in which the power used to generate light is transferred from the outside of the lamp’s envelope to the gas inside the lamp via an electronic magnetic field. This is in contrast to most typical gas discharge lamps which utilize internal electrodes connected to the power supply. There are two significant advantages of induction lighting. The first is extended lamp life due to the absence of internal electrodes (generally the limiting factor in lamp life). The second advantage is the ability to use alternative light generating substances of higher efficiency that would otherwise react with the internal electrodes in typical gas discharge lamps.
Induction fluorescent lighting utilizes microwave or radio frequencies to pass through the sealed bulb and excite the metals and gases sealed within. This allows induction fluorescents to retain a higher CRI (color rendition index) and more consistent PAR (photosynthetically active radiation) output for a longer period of time. The higher a lamp’s CRI rating, the closer the spectrum is to natural sunlight. Marijuana plants love light sources that can emit high levels of CRI while maintaining a consistent PAR output. Their consistency and high CRI rating make induction fluorescents one of the best vegetative lighting systems for marijuana. The initial cost of a horticultural specific induction fluorescent lighting system is high, but a gardener will not have to pay for bulb replacement during the entire life span of the fixture (typically 10-15 years).
Sulfur plasmas are another induction technology that marijuana growers are gravitating toward. This induction technology also utilizes a sealed bulb design. The most promising aspects of sulfur plasmas are that they have the intensity of HID lighting and they emit the ideal light spectrum for plant growth. This is good news for cannabis growers who wish to use an induction lighting system for flowering growth. With CRI ratings of up to 94, sulfur plasma lighting systems have the closest spectral light output to that of the sun than any other artificial horticultural light source. Another advantage of sulfur plasmas is longevity. As with induction fluorescents, sulfur plasma lighting can last up to 10 years and will lose very little PAR or CRI over the course of the fixture’s life span.
Double ended (DE) high intensity discharge (HID) lighting systems, which include high pressure sodiums (HPS) and ceramic metal halides (CMH), have become the lighting system of choice for commercial cannabis growers. This is because they emit an intense light which is capable of penetrating the dense canopies of cannabis gardens. Double ended HID lighting systems are also more efficient at converting electricity into light and have an increased longevity when compared with single ended HID lighting systems.
A typical single ended HID lighting system will have lost 20-30% of its original output after 10,000 hours of operation. However, double ended HID systems do not degrade the bulbs as quickly. In fact, after 10,000 hours of operation, a double ended HID system will have lost only 5-10% of its original output. Double ended HIDs not only have increased longevity for lamps, but they also produce more light per watt of energy consumed. It is not uncommon for a double ended lighting system to produce 10-30% more light per watt of energy consumed when compared with magnetic core ballasts.
DE lighting systems can become even more efficient when they are operated by a square wave ballast. Typical electronic ballasts operate on a sine wave at high frequencies (120,000 Hertz or Hz). Although these ballasts are more efficient than the old-school magnetic core ballasts, they are no match for square wave technology. New square wave ballasts operate at much lower frequencies (50-100 Hz). This low frequency operation is easier on the system’s internal electrical components, which leads to increased longevity for the entire unit. The low frequency operation also helps avoid harmonic distortion that could potentially cause a color shift in the bulb thus changing the light system’s spectral output. In other words, lighting systems which operate on square wave technology are more consistent in spectral output and are much less likely to have any “shifts” in the spectrum throughout life span of the bulb.
Horticultural LEDs are the pinnacle of horticultural lighting efficiency. Their ability to customize spectral output combined with the fact that they are a solid state device makes LEDs the most efficient lighting system available to marijuana growers. Horticultural LEDs have had their fair share of upgrades and have come a long way from the “christmas light” panels and weak track lighting systems of years ago.
The most recent big breakthrough for horticultural LEDs came in the form of COB (chips on board) technology. In a COB LED system, there are multiple light emitting diodes packed into a single module. The groups of LEDs in a COB system are easier to integrate into an effective horticultural light source. In fact, 20-50 individual light emitting diodes can be replaced by a single COB LED. Another advantage of COB LEDs is a larger surface cooling area, which increases longevity and overall efficiency. Perhaps the most impressive feature of COB LEDs is their radiant efficiency. A typical HID (single ended) system has a radiant efficiency of around 30%. This means that roughly 70% of the electricity used by the system is lost as heat and not converted into usable light. A COB LED has a radiant efficiency of 40-50%, which, relatively speaking makes them one of the most efficient artificial light sources for growing plants. All in all, COB LED lighting systems are the most efficient at converting electricity into usable light and are surely a technology that will help shape the future of cannabis cultivation.
It is very important for a marijuana grower to not only examine his or her lighting system’s efficiency, but to also look at all the factors in the growing facility which impacts the garden’s overall efficiency. When calculating how much marijuana per watt of energy consumed was produced by a garden, it is imperative that all watts are considered. For example, if a grower uses 10,000 watts in artificial lighting and 4,000 watts in air conditioners and other equipment, he or she should calculate the efficiency based on 14,000 watts of electrical usage. Certain lighting systems may produce larger yields, but may also require additional cooling equipment which could more than offset the increase in yield. In other words, even though the lighting system(s) is the main contributor, a grower must make sure to consider all input factors when determining a garden’s overall efficiency and his or her return on investment.
New horticultural technologies are being developed all the time. Indoor marijuana growers have been influencing the development of new technologies in the horticultural field for decades. With new state laws, which ease restrictions on cannabis growing, we are sure to see even more innovations developing in the artificial lighting sector. Induction lighting, square wave HID technology, and COB LED lighting systems are all effective and efficient choices for modern marijuana growers. Ultimately, the size of the growing facility, the heating and/or cooling requirements, and the grower’s budget will be the determining factors as to which lighting system will be the best. One thing is for sure, the number of marijuana growers across the globe is constantly climbing. Choosing an efficient lighting system is important for hobbyists who want an efficient garden, but it is imperative for commercial marijuana growers who want to continue to compete in the industry.
Eric Hopper is a Professional Marijuana Grower Senior Editor.