Plasma Grow Lights
Noun. The fear of new things or experiences. (Also known as “Cainotophobia.”)
The persistent fear of anything new. An unwillingness to try new things or break from routine.
Noun. A strong affinity for novelty. Neophiles (also known as “Neophiliacs”) adapt rapidly to changes and loathe tradition, repetition, and routines.
Sunlight is the first order of life – the energy that drives the life systems of our planet, from humans to plankton. So it follows that the ‘heart’ of your indoor garden is the grow light. After all, its purpose is to provide the incident energy required by your plants to grow and bloom: to synthesize the sun. The grow light is the motor of photosynthesis in the indoor garden, driving all other plant processes.
Today, the majority of indoor gardeners in North America use 1000 Watt High Pressure Sodium (HPS) lamps to light their plants and many growers still use magnetic ballasts. It may surprise you to learn that this technology has been around in more or less its current form for over 30 years. In other disciplines, most notably computing, a great deal has changed during this time. Can you imagine buying a personal computer today that even closely resembled that which was available thirty years ago? In 1980 the latest and greatest microcomputer boasted a measly 16kB of RAM (barely enough to store a ringtone these days) and a 5-inch CRT display. If you’re not abreast with the current state of computing technology, then consider this: a megabyte of storage would have set you back over $6,000 in 1980. Today, one hundred times this amount can be purchased for under a dollar. Things have moved on.
So what drove this huge amount of innovation? Essentially, nothing more than a heady mix of human ingenuity and rampant consumerism. That is, we all went crazy about computers and demanded more and more. In just a few decades they went from being arcane university research projects to being suffused into almost every part of our mainstream culture. Will the recent and dramatic rise in the popularity of indoor gardening serve as a similar catalyst for technological development in the field of indoor horticultural lighting? We certainly hope so.
If computers are measured in terms of processor speed and memory capacity, what is the equivalent set of metrics for the performance of a grow light? Okay, okay, obviously a grow light should make things grow. And the plants we want to grow have all evolved over millions of years to best exploit the solar energy generated by the Sun. So we don’t need a Ph.D. in Photobiology to assert that the Sun is the only benchmark we need when it comes to producing artificial light for plants.
That’s a point worth restating. We’re talking about light for plants here, not for humans. It’s very important that we de-personify both our plants and, for that matter, our grow lights. Lumens measure general light intensity for the human eye, not the photo-systems in the leaf. What we perceive as a single color is actually a combination of many different wavelengths of light.
How plants relate to light is more like hearing would be for humans: by frequency. Sunlight contains a ‘full spectrum’ of different frequencies. PAR light, nanometers, and other older references for light can’t be used as a reference for frequency; nanometers and frequencies are inversely related (backwards) to each other. Frequency means it’s more about the energy that plants really need, and nanometers is more about what’s best for people to understand.
The “Plant Sensitivity Curve” shows photosynthetic response to light at various wavelengths. (X axis = WAVELENGTH (nm); Y axis = “SENSITIVITY”) Photo credit: Chameleon Grow Systems.
One of the primary reasons that HPS light was adopted by indoor gardeners is a NASA study produced over 20 years ago that basically stated: “Plants are efficient at using red light.” You have probably seen the spectral distribution charts on some HPS lamp packaging showing the peaks in spectral output. However, plants are efficient at using red light because, of all the colors in the spectrum that shine on the Earth from the Sun, red light has the least amount of energy. Photobiologists refer to this in terms of “electron volts per photon.” You can excite the cells of a solar panel with a violet light that has 3.1 electron volts per photon. But shining red light that has only 1.7 volts per photon on a solar panel is not sufficient to excite the cells. So, just because plants are efficient in using the low amounts of energy in the red parts of sunlight, it doesn’t necessarily mean that the best lighting for plants is high in the red parts of the spectrum. We don’t need to bombard our plants with red light. Plants require all the colors of the light spectrum as they utilize these different parts in different ways.
Another reason HPS light is used by indoor gardeners is to imitate the commercial greenhouse growers who use HPS for daylight supplementation. However, it’s important to note that, in greenhouses, HPS is used in addition to the blue light of natural daylight. It’s clearly a different ballgame to grow indoors using only artificial light, and we should treat it as such.
So what’s an indoor gardener to do? We want to give our gardens lots of light – especially if we are growing light-loving varieties such as tomatoes and capsicums. HPS lamps output a lot of light, but in limited parts of the spectrum. They also produce a LOT of heat in the infrared part of the spectrum. And, as we all know, unless you’re growing indoors in Alaska, excessive heat is the nemesis of the indoor gardener. Surely there has to be a better way to grow indoors? Think of all those kilowatts of energy used to power grow lights, and all the kilowatts of energy used to power air conditioners, chillers and fans to remove the heat they generate! What technology exists to give our plants all the light they need indoors without creating other problems that require energy-intensive solutions? Do we need to improve current technology or go back to the drawing board? Do we need new lamps? New ballasts? New reflectors? New light movers? These are all very important questions.
Before we embark on our preview of alternative grow light technologies, please bear in mind that some of these technologies are further away from being stocked in your local grow store than others. Research and development is happening all the time, and this work is not confined to universities – real growers (albeit super enthusiastic hobbyists) are involved too. Right now, some of these technologies, for a variety of reasons, are less accessible than others. But things will change, if we drive that change. Remember, it was possible to buy a 1GB hard drive in 1980 – it was just the size of a refrigerator, weighed 550 pounds and cost $40,000! Today a hard drive 500 times that size will comfortably slip into your pocket … if there’s room! (It will only set you back $70.)
Plasma Lighting System
Now put yourself in the shoes of an IT enthusiast in the ‘80s. Are we at an equivalent point on the technology/accessibility curve for indoor garden lighting? If so, these are indeed exciting times! Okay, that’s quite enough preamble! Let’s take a look at the contenders …
But first … The human eye is most sensitive to a yellowish green color. But what seems ‘bright’ to us is not what plants respond best to. Photo credit: Chameleon Grow Systems.
In one sense, light can be thought of as electromagnetic radiation, like radio waves, microwaves waves, X rays and gamma radiation. What we refer to as ‘visible light’ is simply the radiation that we can sense with our eyes. The average human eye will respond to wavelengths from about 380 to 750 nanometers. We perceive light as colors, with our maximum sensitivity at around 555 nm, in the green region of the optical spectrum. Light with a wavelength of 380-450 nm is perceived as violet. As the wavelengths become shorter it becomes ultraviolet (UV). At the other end of the visible light scale, wavelengths of 620-750 nm are perceived as red. As the wavelengths become longer (infrared) we perceive this electromagnetic radiation as heat, rather than light.
Light can also be conceived as a stream of light particles, called photons. One method to calculate the intensity of an artificial plant light source is to count the number of photons that hit a leaf per second. The unit for this calculation is “micromoles per second” (µmol/sec). Some growers reference the Photosynthetic Photon Flux (PPF) – just the photons that are between 400 and 700 nm. This is clearly a more relevant way of measuring light intensity for plants than, say, lumens, but it should still only be treated as an indicator. When all has been said and done, we’re trying to establish the quantity of usable light that hits the leaves of our plants.
The distribution of energy in the lamp on the frequency spectrum is called the Spectral Distribution. The Sun has a full, continuous spectrum – and that’s what we’re aiming for too with our grow lights. The ideal grow light efficiently transforms electricity into the maximum amount of usable light energy (for the plants), with as little heat (infrared) as possible. Other factors to consider are lamp life and depreciation, and, of course, cost!
Remember, if you double the distance between a leaf and your artificial light source, the amount of energy that hits the leaf is divided by FOUR. Stated another way, when you double the distance from the light source you lose 75% of the light energy from the light source. So when we talk about how much ‘usable light’ a grow light puts out, we need to consider environmental factors too – namely heat! Experienced indoor growers shoot for a temperature of around 80-82°F around the canopy of their plants in a CO2 enriched environment, slightly less for atmospheric CO2 levels. It’s important that we evaluate the potential of any grow light in the “real world,” and not just the isolated data of manufacturers’ technical specification charts.
Full Spectrum Plasma Grow Light
Plasma International’s Sulfur Plasma grow light. Photo credit: Clive Wing & Boris Lutterbach and Aad Baar.
Plasma International, a British/German company, has developed a grow light based on sulfur plasma technology. The lamp and magnetron unit is an electrode-less lamp that includes an evacuated quartz bulb partly backfilled with argon and with a little sulfur, plus a source of microwave power, a magnetron, for exciting a ball of plasma within the bulb. The lamps themselves are manufactured in Germany and can be powered by any 400W to 1400W Plasma Lighting System. The lamp produces almost no ultraviolet light and just a little infrared. It delivers a full and continuous spectrum (which means there are no troughs or missing/lacking color content). Full spectrum lighting is regarded as crucial for healthy plant development because it’s what plants have evolved for millions of years to exploit.
Wageningen University in the Netherlands has been using Plasma International’s Sulfur Plasma lamp to research simulating daylight in an indoor environment. Researchers had to shine the incredibly powerful light indirectly at cucumber cuttings through mirrors and filters. The tests, conducted in a climate-controlled room, showed that young cucumber plants grew much better then under HPS. Researchers believe this is due to the color of the light and its ability to influence the shape of the plant. At the right light color, the young plant captures light energy far more easily.
The cucumber plants grew more than 60% faster than those grown under HPS, and more than 120% better than those grown under compact fluorescents! There was also a marked increase in branching and larger leaves. The first results (released September 2009) also showed that the specially-created artificial sunlight spectrum made the young cucumber plants 64% heavier than those grown under HPS (SON-T) light, at equal light strength.
Plasma International’s lamp draws 1300W from the mains and delivers 1000W to the bulb. It is dimmable down to between 10-40% depending on which bulb is being used. The moving parts inside the lamp are guaranteed for 100,000 hours of use – this movement, the manufacturers claim, gives greater control over the plasmoid. They also claim that they can quite easily alter the mix of the bulb and adjust the spectral output to specific applications. To date, Plasma International has developed one lamp for vegetative growth and another for flowering. The lamps produce less than half the infrared heat per watt compared to HPS or Metal Halide.
The lamp comes as two boxes. Each box is 9” x 6.6” x 6.6” in size. One box contains the plasma-i-tron and the other is the power supply. The lamp can easily cover the same area as a 1000W HPS but, because of the reduced heat, it could be positioned closer to plants.
More information: www.plasma-i.com
Time to market: 1-2 years.
Cost: Currently only available for research purposes. Expect to pay upwards of $3,500 per unit.
Luxim’s lightweight Light Emitting Plasma Emitter.
Luxim Corporation in California has developed a solid state light emitting plasma – it uses metal halides and argon, not sulfur. It uses no electrodes and draws 266 watts. Their latest model, announced in February 2010, is the LIFI-STA-41-02. Luxim only produces the light unit. It is up to companies further down the ‘technological food chain’ to develop specialized appliances for their specific market, such as TVs, theatrical lighting, healthcare, horticulture, etc. Crucially, the LIFI Plasma light was NOT invented to grow plants. The spectrum is still lacking a lot of red.
LUXIM is researching how to use different metal halides in the plasma cell in order to create a better spectrum for plant growth. Until they, or somebody else, figures this out, various companies in Europe and North America are experimenting with LEDs in an effort to correct the spectrum. However, whether this is actually possible or not remains a bone of considerable contention. One such example is Chameleon™ Grow Systems in Florida. They have developed the Solar Genesis VI (due for release later this year) which houses two LIFI plasma units and banks of high output LEDs. Infrared (IR) radiation from the light is minimal.
The Solar Genesis VI spectral output compared with an HPS, overlaid on plant light sensitivity. Photo credit: Chameleon Grow Systems.
The internal ballast has 91-93% conversion efficiency and the lamp life is rated at an incredible 50,000 hours (11.5 years) with no replacement every 9-12 months necessary.
The Solar Genesis VI supplements two Luxim 266 watt LEP units with four banks of high power LEDs. Photo credit: Chameleon Grow Systems.
Tech Stats: LIFI-STA-41-01
Emitter Length: 72.9 mm
Emitter Diameter: 116 mm
Driver Unit L × W × H: 193 × 85 × 32 mm
Rated Average Life: 30,000 hours
Total Initial Lumens: 15,000 lumens
Typical Turn-on time: 30 seconds
CCT: 5800 K
Dimming Range: 20-100%
Nominal AC Power @ 277v 266 watts
More information: www.luxim.com www.chameleongrowsystems.com
Time to market: 3-6 months
Cost: $7,000 per unit for Solar Genesis VI
Lumatek’s new ballast will enable growers to run highly efficient 400V lamps on 230V power.
Lumatek is in the process of developing a new 400V professional ballast that drives the professional Phillips HPS 400V lamp, but runs on normal 230V. Gavita, a leading European horticultural lighting company, has teamed up with Lumatek to develop and bring their products to the indoor gardening market. Industry insiders concur that this allegiance is great news for growers!
The 400V bulb, which is more efficient, performs more consistently and lasts longer – and it has an enhanced spectrum. Even better: it was built specifically to run on electronic ballasts.
Time to market: 3-6 months
Cost: To be announced
More information: http://tinyurl.com/yjzx2dk (pdf)
SunPulse® bulbs were specifically designed to produce the true photochemical reactions plants need to make the maximum amount of photosynthesis and produce the most chlorophyll. This is a very important point. SunPulse® bulbs were made for plants. They were designed by Gerald Garrison – and if that name sounds familiar, you may remember he was featured on the cover of Urban Garden Magazine 003 in relation to his indoor food production facilities in February 2009.
The original SunPulse® digital bulbs, the first digital bulbs to ever be introduced, are made in four unique Kelvin colors: 3k, 4k, 6.4k and 10k. The lamps’ wattages range from 100 to 1000.
SunPulse Pulse Start Metal Halide Lamps were designed for specifically for plant growth.
Central to their lighting model is a photosynthesis delivery system which houses and rotates multiple lamps (of different Kelvin temperatures) over the plants, to provide full spectrum lighting. A lighting schedule is located on every bulb box which outlines when to use each particular bulb, as well as suggestions for those who aren’t budgeted for four bulbs per fixture.
SunPulse’s 1000w Commercial Grade bulbs were originally designed exclusively for commercial food production facilities, but are now being made available to growers everywhere for the first time. The Commercial Grade bulbs come in three proprietary colors: 2.8k (fruiting/flowering), 5.7k (full spectrum) and 10k (ripening). Commercial greenhouses around the world are already enjoying the benefits of the greater efficiencies and color rendering made possible by this series of bulbs. The Commercial Grade lamps’ high-temperature tolerances, rugged design and top quality components are the perfect choice for full-scale production facilities and now are available for smaller producers as well.
Want to know more about these or any other horticultural lighting technology? Fire your questions at will by posting a comment below!