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  1. #1
    Aquaponics 101 Oliver's Avatar
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    Induction Lighting

    Since my last post on our Micro Farm we have obtained a new grow light that we are testing. It is an Induction Light made by Inda-Gro.

    Induction lights are similar to fluorescents. A fluorescent tube is made of glass and has a little bit of mercury in it. Generally, inside the tube there is an electrical heater/cathode/anode at either end that is activated during light start-up. Once the heaters reach the required temperature, which can be very quick, they boil the mercury in their vicinity creating mercury vapor and then the light changes to a high voltage operating mode, which passes an electrical current from one end of the lamp tube to the other. Once this current starts to flow, the remaining mercury in the tube becomes activated and the light gets brighter. This second part usually takes several minutes.

    The electrons passing through the tube in the mercury vapor create an indigo to ultra violet light, which in turn activates a phosphor coating on the inner surface of the fluorescent tube. This phosphor material can be made up of different substances yielding different colors of light but are usually combined to produce what appears to be white light of varying hues.

    The diameter of the light in millimeters, be it 12, 8 or 5 are used in the labeling of the type of tube, as in T-12, T-8 or T-5, respectively. T-12s put out about 40 lumens of light per Watt of electricity, while T-8s and T-5s put out about 80 lumens of light per Watt. A lumen is a measurement of light intensity at 550 nanometers or yellowish green. The temperature of the light is not how hot it gets but a value related to the overall color of the light. 6500K is in the blue spectrum, 2500K is in the red spectrum and 4500K is more towards the yellow spectrum (soft white), but they all have a white or off-white color to the eye.

    When purchasing fluorescents for growing leafy greens go by the temperature not the lumens output. It is best to select the 6500K, which has a lot of blue in it. By the way, K stands for Kelvin; which is a centigrade scaled temperature where zero is absolute zero unlike centigrade's zero of the freezing point of water.

    Fluorescents degrade starting as soon as you first turn them on and after a few thousand hours won't even turn on. This is due to the metal filament that is used both to start the light and to conduct electricity through the light. It is a type of vacuum tube and those old enough to remember, vacuum tubes have a limited life mainly due to the deterioration of the direct or indirect heated cathode. This cathode emits metal particles and gas and eventually deteriorates to a point where it ceases to function as an emitter of electrons. As this process takes place, electroplated metal can be seen at the ends of the fluorescent tube as black deposits.

    Induction lights use a fluorescent tube as well, but it is formed in a loop, either in a circle or rectangle and there are no metal electrodes in it to deteriorate. The current in the light is induced by way of a magnetic field that is placed on the outside of the light using coils of wire at two opposite points along the closed loop lamp tube. This field is alternated several million times a second producing a fast change of voltage within the light by way of the conductive residual mercury vapor in the tube. Once the current begins to flow in the tube it starts to heat up and the rest of the mercury is activated; and then the fluorescent coating on the inside of the light begins to put out the multitude of colors depending on the mixture of the phosphors in the coating, just like the regular fluorescent tube.

    There are several advantages to induction lighting. First and foremost is that they are about twice as efficient as either T8s or T5s. Second is that they last 5 to 10 times longer. A typical Induction light designed for growing will last for 70,000 hours at nearly 100% brightness and the on to 100,000 hours to 70% brightness.

    Your typical fluorescent's blend of phosphors is not designed to put out the optimum colors for plants. The Inda-Gro Induction light's phosphors have been engineered to emit the optimum colors for all phases of plant growth.

    We have replaced two 8 tube T5 fixtures, each drawing about 400 Watts, with a single Inda-Gro Pro-420-PAR, which draws about 420 Watts from the wall. The T5s had an approximate 2 X 4 foot light pattern and the Inda-Gro has a 4 x 4 foot light pattern when set at the appropriate height. Because the light is higher than the T5s it replaces, we can now grow taller plants. Because of the color spectrum of the Inda-Gro we can now grow a variety of plants including peppers and tomatoes.

    We will be evaluating this light over the next several weeks and give you an update as we test out different plants.

    The down side to all of this is that these lights cost almost $800 each. Two 8 tube T5s cost retail about $500. So the extra $300 for a single Pro-420-PAR at our current electric rate of 31 cents per KWH, we estimate that it will take a little over 4 months to pay back. After that it will show a continued reduced electric bill. Even at 10 cents per KWH it will only take one year to make up for the difference in the cost of the lights.

    The other energy consumption reduction is the cost of cooling the grow room, especially in the summer. Even in the winter our grow room cooler is coming on occasionally.

    If you are planning solar power then the saving there will pay for the lights. In addition, utility companies have rebate programs that will, in some cases, almost pay for the light.

    Here is a picture of the light installed after removing the two T5s:

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    [attachment=0:1ul8pejl]Inda-Gro Lite.jpg[/attachment:1ul8pejl]
    Oliver
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  2. #2
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    Re: Induction Lighting

    Very interesting Oliver. Thanks for sharing and look forward to reading about your results.

  3. #3
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    Oct 2012
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    Re: Induction Lighting

    I too am looking forward to updates on this. Assuming you have your lights on 14 hours a day, that comes to ~5110 hours per year. So if these things are really 100% bright for 70,000 hours, then you'd only have to replace them every 13 years or so. This assumes that you'd ditch them before they get a chance to go down to 70% efficiency. If you'd still keep them for the additional 100K hours, you'd only be replacing your lights once every 33 years!

    Anyone know if Inda-Gro actually guarantees those results? On the 70K hours plan the hardware would cost about 60 bucks/year, and under the 170K hours plan, 24 bucks/year.

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