LED Grow Lights for Indoor Food Production, by J.H.

LED Grow Lights for Indoor Food Production, by J.H.



　

Lighting products based on Light Emitting Diode (LED) technology continues to improve. Not only are lights getting cheaper, but the individual LED components are getting more higher powered and both efficiency and lifetimes/longevity are improving. Over time, LED technology is poised to replace the problematic and often loathed Compact Fluorescent Light (CFL) as the preferred alternative to traditional incandescent light bulbs.

However, this article is not about ordinary lighting applications but rather LED lighting specifically used for indoor growing applications. The benefits of LED lighting for plant growth, particularly as the technology advances, are truly revolutionary and will change the way indoor food production is done in the years ahead.

These advances are useful to know for those interested in self-sufficiency or survivalist technology. Food can be produced with greater efficiency indoors, whether due to the desire for discretion and security or due to seasonal restrictions.

Existing plant growing technology now consists basically of large incandescent lights, either High Pressure Sodium (HPS) or Metal Halide (MH) bulbs. These are basically large, elongated bulbs capable of operating at powers up to 1000 watts each. They cannot be driven with ordinary A/C power but need a special transformer, called a ballast, to drive the individual bulbs. There is some power loss at the ballast, as well, so the power needs for a 1000 watt bulb can be in excess of 1000 watts. The HPS bulbs and the MH bulbs produce slightly different spectra, with the HPS bulbs producing a redder spectrum and the MH bulbs producing a bluer spectrum, to accommodate different growing needs of plants in their life cycles. The HPS and MH technology also require different ballasts to run, although some ballasts today are switchable and can accommodate both technologies. A bulb of this sort typically costs about $70-$100 and can be expected to last for 6,000 – 8,000 hours before needing replacement.

A quick point to be made here is that indoor grows can be either based on ordinary soil (pots of plants) or hydroponic (soilless) technology. I won’t get much into the specifics of either, except to say the hydroponic grows tend to be more efficient, but they add some complexity to your system. According to some viewpoints, hydroponic grows can double the production of plant products for the same energy input into them. However, either technology still needs light to provide energy for the plants, so either will benefit from more efficient light production.

The main advantages of LED grow lights are efficiency of power use, longevity, and ease of powering. (They can be driven with DC sources.) In addition to these main points, LEDs have some secondary advantages as well.

If you’ve read any information on LED grow lights (especially the ads), you will hear them indicating that LEDs provide the same equivalent light for one-third or even one-tenth the power. So, for example, a 100 watt LED light provides the same benefit to the plant as a 1000 watt HPS. I’m not sure I’d believe those claims, but if you had two lights of comparable power, the LEDs would definitely be more advantageous. It’s hard to quantify exactly what the advantage is, but something like 2X or 3X is probably not out of bounds. To date, LEDs still have had limited impact with growers because costs are still high, and, perhaps more importantly, overall wattage is still on the low side. Whereas HPS and MH lights top out at 1000 watts apiece, it’s hard to find an LED light that’s more than 200-300 watts. This is slowly changing, and larger units are becoming available.

The reason for the greater efficiency is twofold. First, the LED lights themselves produce light more efficiently. Second, since LEDs can produce narrow bands of wavelengths of light, by selecting the correct wavelengths that plants respond to the most (the red and blue light bands), one can build a light that only uses energy for the wavelengths that plants like. In general, plants make little use of light in the green area, which is why plants tend to be green, as the green light is reflected back to our eyes. So, a light that avoids those bands not only saves energy but avoids bombarding the plant with light energy it can’t make use of energy. For this reason, LED grow lights tend to produce a reddish-purplish hue. An example of this (May, 2014) is NASA’s Veg-01 growing experiment to grow lettuce on the ISS.

[A brief aside on light wavelengths: Ordinary white light is made up of particles (or photons) each with an individual wavelength. The visible light spectrum consists of light with wavelengths of 400 to 700 nanometers (nm). The visible light colors start with blue or violet at 400 nm up through green, yellow, and orange and ending at red at 700 nm. Outside of our visible range is ultraviolet light at shorter wavelengths (below 400 nm) and infrared light at longer wavelengths (above 700 nm).]

The main energy gatherers in plants are structures known as chlorophyll. These exist in two main varieties– chlorophyll-A and chlorophyll-B. Both have absorption peaks in the blue range, about 450 nm. Chlorophyll-A has another narrow peak in the red range at 660 nm. Chlorophyll-B has another narrow peak in the red range at 630 nm. So any lights you use or buy should have all of these wavelengths covered. Any light that does not specify their wavelengths should be avoided! Some lights have additional bands, which are probably okay, and the ratio of the different colors can vary. Any lights that do not have the 660 nm wavelength should be avoided, as some plants cannot flower, or grow poorly, without the 660 nm light. In terms of ratio, a proportion of 30% blue (450 nm), 50% red (630 nm) and 20% red (660 nm) is not a bad mix. Opinions on this vary.

So, to summarize (and get us back on track), the fact that individual LED elements can produce a narrow bandwidth of light means that grow light systems can be tailored to provide only the light that the plants need, which saves energy as unneeded spectra are not produced. So LEDs are more efficient with energy use compared with broad spectrum light sources, like HPS and MH lights.

LEDs are VERY long lived. Longevity is typically 70,000 – 80,000 hours at nominal current draw. Even then, that is only the timeframe when output has dropped by some specified value; for example, its output may be 30% lower than nominal "new" values, but the LEDs are still operating. LEDs can operate, with reduced performance for 100,000 hours or more. Given 12-hour growing days, this is a lifetime of more than 20 years’ worth of growing days. This compares with a HPS bulb, which has a nominal lifetime of about 8,000 hours, but is typically replaced after 6,000 hours due to lower performance.

This isn’t to say an LED light won’t break. There are other components in the light (electronics, fans, etc.) that could be subject to failure. These would have to be repaired, but as long as the LEDs are not subjected to extreme heat or excessive current, they should be fine and live a long, full life.

The third advantage to LED lights is their ease of power. HPS and MH lights need an A/C power source which feeds a ballast to provide the needed voltages to the lights. There is some power loss in the ballast, and if power is suddenly lost, some lights require a 30 minute cool-down before they can be re-lit.

LEDs, on the other hand, can be powered from DC sources, can be turned on and off at will, and have no ballast requirements. They are a perfect light source for power systems that have either a DC supply, such as solar panels or battery banks. Of course, most LED lights for the market are not DC powered and plug into the wall, but the underlying power driving the LED lights is a direct voltage. This all translates to added efficiency of LED lights when used with a system with DC power sources.

These are the main advantages of LED lights for use in self-sufficient living systems. In addition, there are secondary advantages to LED lighting systems as well. I will touch on them a little bit, in the context of self-sufficient living situations.


LED lights produce heat, but they do not project heat.
If you work with LED lights, they are kind of strange beasts. Unlike an ordinary 60 watt light bulb, which would burn you if you touched it, LED lights project almost no heat. As a result, plants are not subject to burning on LEDs the same way plants under incandescent HPS or MH lights are. Also, evaporation due to heat is reduced in plants grown under LEDs. Finally, plants grown under LEDs do not have to expend energy "fending off" unneeded light and heat sent to them by incandescent lights. This results in faster growing and reduced water use.

This is not to say that LED lights do not produce heat; they do. The heat is just not projected out to the plants. Instead, the light itself heats up. Larger LED lights often have built-in fans, like computer cases, to keep them cool.

This leads to an interesting opportunity for self-sufficient living systems. Wintertime living in northern climates can be challenging, from a fuel perspective, as residences need some form of heating. Many self-sufficient residences opt for baseboard heating, as they have access to some electrical power sources, such as wind turbines and (reduced) solar energy. Instead of dumping that power into heating modules, why not send some of it to grow lights as well? The residence still benefits from the heating, and there is food production, as well.


Plants grow differently under LED lights.
There are enough environmental differences when using LED lights, that the plant themselves grow a bit differently. Mostly, this seems to be in the area of water use, but there may be some other changes as well. The plants benefit from the reduced heat stress. By turning on just the blue lights, you can enhance plant bushiness. By turning on just the red lights, you can get the plants to stretch further. (This requires lights that have selective control on their red and blue spectra, of which many do NOT have.) In general, it’s a somewhat different (but more productive) growing environment that might need a bit of effort to get used to.


Summary
For self-sufficient living, you need food. Ideally, you can just grow it outside, but seasonal and security considerations might make this not feasible all of the time. If the decision is made to grow food indoors, LED grow lights are the clear choice to use for your light source (barring the sun, of course). They offer energy efficiency, longevity, efficient water use, and the ability to work with a DC power system. No other lighting technology should be given serious consideration. Good luck and good growing!


From the Survival Blog