Lighting and Horticulture

 Simple Basics of Horticultural Light

The basics in Horticulture Lighting is color measured in nm (nanometers) and how much of this growth light reaches the plants measured in μmol (micromols). It's not quite that simple but these two measurements will get you to the diving board. So keep your eye on them as your plunging into the rest of your learning about horticultural lighting. kighting-plant-photosynthesisPlants have a completely different sensitivity to light colors than humans. It stands to reason. We use light to gather information around us with our eyes. Plants use light to grow. Photosynthesis is the basic process that leads to growth of a plant and light is an essential part of this. The energy from photosynthesis is used to form glucose from carbon dioxide gas (CO2) and water, which are taken up by leaves and roots. We need to rethink light when discussing plants.

Color Defined in nm | Nanometers

With regard to plant growth, light is defined in terms of small particles called photons. The energy content of photons varies, depending on the wavelength in the global light color spectrum (also referred to as global radiation spectrum) measured in a unit called nm. A nm is an abbreviation for nanometers. It is a distance measurement. A nanometer is a billionth of a meter, giving us the width of the wave length. The length of the wave produces the color in the global light spectrum. Different wave lengths produce different effects in our eye and in the growth of a plant during photosynthesis.

PAR Region | Growth Light in Micromol (μmol)

Plant have different sensitivities for different colors of light, and that influences different light-sensitive activities as well. The only part of the entire global radiation spectrum which can be used by a plant for its photosynthesis is between 400-700 nm, this is called the PAR-light (Photosynthetically Active Radiation). The shorter wave lengths close to 450nm, are used by the plant for fast growth, while the opposite end of the PAR near 650nm, is needed for strong flowering. Approximately 45% of global radiation is PAR light.  The amount of photons in the PAR region are called growth light (indicated in micromol (μmol)). Providing only the light needed by the plant is a world of difference from simply giving the plant light from the different light mechanisms, such as incandescent, HID's or florescent bulbs. If you are serious to know how much light a plant can use for growth or flowering from any particular type of light bulb, you must know what global radiation length (color) it is producing (indicated in nanometers (nm)) and how much of it the bulb produces (indicated in micromol (μmol)).

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Replace a 660Watt HPS with LED | Example

Replace a 660Watt HPS with LED | Example

Photosynthetic Photon Flux Density (PPFD) Photosynthetic Photon Flux Density(PPFD) goes by various names, Quantum Light or simply Photon Flux. In all cases, it is a unit of measure to express the light quantity relating specifically to photosynthesis in units called micro-moles. The PPFD is expressed in micro-moles of photons per meter squared, per second (μmo/ms/sec). You could say, the PPDF is to PAR as Lux is to lumens. The prior is horticultural specific, while the latter, refers to the capacities of the human eye. A mole is a quantity, an amount, a very large amount. It is a number equal to the number of atoms in 0.012 kg of carbon-12. A micromole is one millionth of a mole. Example Using PPFD Measurements I have to hand it to Build My Led (BML), a company out of the USA. They do a great job of specifying their products. Below is a good example of good information, I found on their web site, offering a LED replacement equivalent to a 660watt HPS bulb. They give the exact wavelengths in nanometer (nm) units and the quantity of photons getting to the plant in PPFD, micromoles/m2/second (μmoles/m2/s). In order to do this you will have to know the distance of the light source to the plant. The distance they placed the fixtures, they ave posted as 10 inches. HPS vs LED | Example This LED complex is made up of five 48″ All-Purpose Red Growth Spectrum fixtures. It is designed to replace a 600W HPS system over a 4’x4′ growing area.  I admire their advertising because they give exact relevant information in an informed professional language. Your going to have to be familiar with that language in order to judge any fixture product intelligently. Unlike many companies using only descriptive adjectives (“the best”) rather than quality and quantities in the PAR range. This system delivers an average PPFD reading of 200 PPFD. The fixture mounting height was 10″ from the measurement plane, and provides increased uniformity over HPS. In addition, it is emitting only the PAR ranges a plant can use. All the while consuming 61% less watts. Light Levels for Some Common Plants  The table below provides a reference to light levels for a sampling of plants and sun conditions House Plants 30 to 200 PPFD Leafy Crop Plants (i.e. Lettuce & Basil) 200 to 600 PPFD Tomatoes & Other Fruit Crops 400 to 1000 PPFD Full Sunlight in Summer @ Noon 2000 PPFD Full Sunlight in Winter @ Noon 1200...

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LED vs HID Lighting In Horticulture

LED vs HID Lighting In Horticulture

A light emitting diode (LED) is a light source from a semiconductor, first observed in 1927 and was made into a practical light source by Nick Holonyak in 1962. LED lighting break threw have been coming in strong, especially in the last few years. There is a lot more to know about a LED now. You would be amazed. LED Compared To HID Lighting LED is 70% Cooler All HID lights contain a mixture of gasses within the glass enclosure. The internal temperature and pressure gets quite extreme. LED lights, on the other hand, does not use  gas, operating under extreme pressures and temperatures. In contrast LED lights contain a solid state lighting element, eliminating several risk factors associated with high pressure gases. Led is 70% cooler than HID lighting. This means you can place LED lights in between, on the sides of as well as on top of plants. This places more light where it is needed, as well as reducing the space requirements. LED Emits 75% More Usable PAR Light HID lights are mostly suboptimal from the perspective of a plant. Plants only respond positively to certain wavelengths within the global color spectrum. Less than 25% of the power consumed by HID lights is Par light devoted to plant growth. By contrast, 100% of light emitted from a properly designed LED is usable by plants. LED is Placed 10 Times Closer to Plants You must also know how close you can apply a particular light bulb. The farther away a bulb is from the plant, the less growth light will reach it.This is important. A HID bulb needs to be almost 3 feet from the plants while a LED can be placed as close as 3 inches away. The reason being heat and UV light radiation. UV will burn a plant just as it burns our skin at the beach. LED has no UV. It also runs much cooler. The Physics Behind LED Lighting When a LED is turned on, electrons are able to recombine with holes within the device, releasing energy in the form of photons. This effect is called electroluminescence. The wavelength of the light  is determined by the energy band gap of the semiconductor. With a LED system you can produce the color of light needed in any plant development stage and no more. Therefor the Watts consumed are in the needed range and no more. This fact makes the LED lighting more efficient than the deseptive “lumens per Watt” numbers. Be sure to read Understanding Watts Lumins, Lux Par. The differences are essential to understand if you would like to be informed about horticultural lighting needs. Header images courtesy of : Research Manager: Dr Titta Kotilainen, of  Valoya...

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Understanding Watts Lumens Lux PAR

Understanding Watts Lumens Lux PAR

Video Credits to Hort Americas Chart by Spectrum Technologies When comparing horticultural light bulbs we should know if we are wanting color spectrums in the PAR range balanced for a vegetative or a flowering growth. Then we should focus on the growth light’s quantity of photons (PPFD) emitted and reaching the plant from the bulb at a certain distance and finally how many of those emitted photon reaches the plant per day (DLI) in the applied photo-period. Confused? Then read on to understand these concepts perfectly. Watts in Horticulture Most of us are accustomed to referring to Watts in regard to the strength of a light bulb, when wattage means nothing in terms of light output . Wattage measures the consumption of electricity. But as we grew up with the incandescent light bulb, we had a relative understanding by knowing the wattage. A 20 watt incandescent gives half the light as a 40 watt, for example. However now, we are exposed to many different bulb types. Besides, plants respond to light differently than our eyes. We are into indoor horticulture and have come to want to compare other classes of lighting fixtures such as florescent, Hid, HPS, MH and LED. So comparing wattage doesn’t work for us anymore. It wont even work comparing LED to a LED. So lets get educated. Lumens in Horticulture Lumens have nothing to do with horticultural growth. A company using this term for horticultural topics… should not be. Regrettably however, the bulb rating many growers are familiar with is “lumen”. A lumen is the total light produced within the range of the human eye right next to the source, i.e. the light bulb. Plants have a completely different sensitivity to light colors than humans. Lumens tells us nothing about the distribution of that light energy over the spectrum. Neither does it tell us how much is useful for plants. Lumens are only interesting if we are talking about home, work, store front or parking light illumination, not horticulture. Lux in Horticulture Similarly, lux tells us very little about a lamp’s plant-growing power.  Unlike lumen, which tells us how much human eye-light is GIVEN off at the bulb, lux tells us how much human eye light is RECEIVED at at any particular location. A bulb giving off 1000 lumins is fine but how much light do you receive from it one meter away or two meters or even one kilometer? What a lux will tell you is how much light is received at any one place.  Again, because lux meters are meant for measuring the amount of light usable by humans, they don’t tell us anything about how plants will respond. So in summary the difference between the units Lumen and Lux is that Lux takes into account the area over which the luminous flux is spread at a fixed distance. Lumens is the amount of light coming from a light source irrespective of the distance to any object. nm in Horticultural Lighting A nm is an abbreviation for nanometers. In lighting it is a distance measurement. A nanometer is a billionth of a meter. It tells us the width of the wave length signifying what color it is in the global light spectrum. Plants require the spectrum in between 400-700 nm. This range is often called growth light, however the term “PAR” is a bit more descriptive and correct. PAR in Horticulture Plants have a completely different sensitivity to light colors than humans. The only part of the global radiation spectrum which can be used by a plant for its photosynthesis is between 400-700...

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Ultraviolet Germicidal Irradiation Lighting

Ultraviolet Germicidal Irradiation Lighting

UVGI is an electromagnetic radiation which sterilizes microbes such as bacteria, viruses and molds. At a wavelength of 2,537 Angstroms (254 nm) UV destroy nucleic acids in microbes disrupting their DNA Ultraviolet Germicidal Irradiation Lighting General Information Ultraviolet Germicidal Irradiation (UVGI) is an electromagnetic radiation disinfection method that uses ultraviolet light (shorter than visible light) to kill microorganisms such as bacteria, pathogens, viruses and molds. Even parasites such as Cryptosporidia or Giardia, which are extremely resistant to chemical disinfectants, are efficiently reduced. It is a purely physical, chemical-free process. UV Germicidal Irradiation  Types UV can be separated into various ranges, with short range UV (UVC) being germicidal-UV. At a wavelength of 2,537 Angstroms (254 nm see image right) It destroys the nucleic acids in these micro organisms disrupting their DNA, leaving them unable to reproduce. It is quick and clean, leaving no taint, chemicals or residues in the water.  UV treatment is quick. Not only that, in terms of primary energy use, it is 20,000 times more efficient than boiling water. The use of UVGI to sanitize has been an accepted practice for the last 65 years or more. A disadvantage of the technique is that water treated by chlorination is resistant to reinfection, where UVGI water must be continually passed threw the UV lamp system. The sterilized microorganisms are not removed from the water after treatment, nor remove dissolved compounds and/or particles in the...

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Artificial Lighting Types in Horticulture

Artificial Lighting Types in Horticulture

There are many options for growing plants indoor with artificial lighting. The “best” solution depends on the plants requirements and then the growers concerns. Plants do not use the entire spectrum of light from the sun nor from many of the types of artificial light available. With the dawn of LED lighting, this fact is brought home. Vegetative growth needs more blue light  while flowering requires a spectrum of light with more red/orange. The blue absorption region is 430-450 nm and that of red is 650-670 nm. The grower is normally concerned about two major factors. These are electrical energy consumption and heat. Lets look at the major types of lighting and briefly describe how they stack up to the plant/grower requirements. Incandescent Lighting We are all familiar with the normal household light bulb first invented and brought to market by Thomas Edison. So we wont elaborate much on this class of bulb. But it is interesting to compare the different types of lighting to incandescent since it is so familiar to us. Basically this bulb produces light with a filament wire heated to a high temperature by an electric current passing through it, until it glows. The hot filament is protected from burning up via a glass bulb that is evacuated of gasses. This type of lighting is the most inefficient, producing roughly 15 lumens per watt. Florescent Lighting A fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor atoms that causes phosphor to glow, producing a somewhat narrow spectrum of visible light. However a fluorescent lamp converts electrical power into useful light much more efficiently than incandescent lamps. The luminous efficacy of a fluorescent light bulb is about (60 lumens per watt) 4 times the efficacy of a incandescent bulb. High Intensity Discharge Lighting- HID High Intensity Discharge lamps is a category of lamps containing two very important and popular types of bulbs used in horticulture, Metal Halide (MH) and High Pressure Sodium (HPS). Both are HID’s, a type of electrical gas-discharge lamp which produces light by means of an electric arc between two tungsten electrodes. Metal Halide Lighting- MH Developed in the 1960s, Metal Halide Lighting produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides. Metal-halide lamps have high luminous efficacy of around 75 – 100 lumens per watt compared to incandescence’s 15 and florescence’s 60lu/w. The spectrum of light produced is in the blue range. Vegetative growth requires more blue lighting than other wave lengths. High Pressure Sodium Lighting- HPS High Pressure Sodium (HPS) is a HID gas-discharge lamp that uses sodium in an excited state to produce light rather than Metal Halides. High pressure sodium lamps are quite efficient—about 100 lm/W.  The higher powered models of 600 W and above have an efficacy of up to 150 lm/W. Plants in a flowering stage of development require more of a red spectrum, of which the HPS produce more of. Magnetic Induction Lighting A Magnetic Induction lamp (also known as Electrode-less Fluorescent Discharge Lamps (EFDL), is a type of fluorescent lamp.  Energy is transmitted into the tube by means of induction. It is induced from the exterior of the tube into the interior without the need of electrodes. There are 2 main types of Induction Lamps, External Inductor and Internal inductor. Both use electromagnets wrapped around a part of the tube (an external inductor lamp), or inserted inside the lamp (an internal inductor lamp). Light is produced by an up-conversion process within the tube where UV light is generated within the lamp by excited mercury atoms The UltraViolet rays...

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LED & HID Combination

LED & HID Combination

Your going to have to stay with the HID’s but a combination of both will keep the amount of HID lighting needed way down. This means less of a heat footprint, lower electric bills and more production per square meter. The shear amount of light HID fixtures provide is staggering. But so is the energy consumption and especially the heat. Due to the directional characteristics of traditional metal halides, the bulb produces mass amounts of wasted light from the top and sides of the lens. Advances in modern LED lighting have created new and exciting opportunities for horticulture. For example a LED light dissipating 60 watts of total power would need to be replaced by a metal halide bulb dissipating 400 watts of total power. The LED fixture produces 18,000 Lumens while consuming a paltry 213W….thats a 54% reduction in operating costs. Besides LED lighting is 70% cooler than HID lighting. LED lights generate significantly less heat when compared to the metal halide bulb. Not only do the LEDs generate less heat, but they also dissipate their thermal energy back into the mounting fixture. All HID bulbs dissipate heat from the front of the bulb and down into the plants. This can make thermal management a challenge, as we all have experienced  ...

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