LED Lighting for the Horticulture Market

In May, I wrote a blog on my thoughts about the horticulture lighting market after attending LightFair International. Last week I attended Cultivate – a huge horticulture tradeshow in Columbus, Ohio, and I want to update those thoughts. Let me start off by saying that this tradeshow was by far the most beautiful tradeshow I’ve been to. Instead of staring directly into bright lights for 3 days, I got to see beautiful flowers and trees and the aroma and aesthetics were amazing. That aside, of the lighting companies I visited, almost all exclusively had LED products but a lot still showcased their traditional HPS (high pressure sodium) and fluorescent products. These are some of the main topics/issues that were discussed:

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Key Takeaways from Cultivate16

In May, I wrote a blog on my thoughts about the horticulture lighting market after attending LightFair International. Last week I attended Cultivate – a huge horticulture tradeshow in Columbus, Ohio, and I want to update those thoughts. Let me start off by saying that this tradeshow was by far the most beautiful tradeshow I’ve been to. Instead of staring directly into bright lights for 3 days, I got to see beautiful flowers and trees and the aroma and aesthetics were amazing. That aside, of the lighting companies I visited, almost all exclusively had LED products but a lot still showcased their traditional HPS (high pressure sodium) and fluorescent products. These are some of the main topics/issues that were discussed:

Plant recipes - When talking to these companies compared to the ones at LightFair (only a few were at both shows) it was apparent they have been specializing in this industry and have a more biological perspective. They recognized the importance of understanding plant biology to create a viable light source. There were a lot pink/purple products with the red and blue spectrums only, but many companies were saying they are moving towards a more full-spectrum light. They recognize that all wavelengths of light in the PAR (photosynthetically active radiation) range, 400-700 nm, are useful in driving photosynthesis. To put it another way, plants have been thriving on sunlight since they have been around and its light is not comprised of solely red and blue wavelengths

When asked about light recipes, a few companies at LFI said they are leaving that up to the grower to determine the best mix and then they can make the fixture with any recipe. However, even though most growers are aware that these different spectrums exist and can affect plant growth, they do not know the optimal spectrum and wavelengths they need because they never really had to think about it before.. For example, HPS gives off more light in the red end of the spectrum and some companies use CMH (ceramic metal halide), which gives off more light in the blue end, to balance this or to get different results. But when talking about specific wavelength mixes, more research needs to be done. Another major question that was brought up was whether plants grown solely under LED lights in specific wavelengths needed to be acclimated back to full spectrum when put in a greenhouse, retail store, or outside.

LED light intensity – When discussing lighting for humans, it’s all about the lumens the fixture gives off. When discussing lighting for plants, it’s all about the photons the light gives off and, more importantly, the PPFD (photosynthetic photon flux density) which is the amount of photons that actually reach the plants, measured in micromoles per meters squared per second (μmol/m2/s). Certain plants require different daily light integrals (DLI), which is the amount of PAR received by the plant over a 24-hour period. For indoor growing, where LED is the sole light source, growers can meet the DLI requirements of plants by minimizing the distance between plants and the light source. In commercial greenhouses where the lighting is supplementary to the sun, you have to be more conscientious of the fixtures placement, and therefore the light intensity of most* LEDs is not sufficient to meet the plants DLI in a cost effective manner. One grower at the conference said that in order to get the required PPFD for their greenhouse, they would need more LED lights and need to put them closer to the plants, which would then block the natural sunlight so they would need to run the lights longer to get the required DLI which would negate the cost savings benefit.

*I say most because obviously this does not apply to all LED products out there. There are some reputable companies with products performing the same or better than HPS.

Light degradation – A big selling point of using LEDs is their lifetime. Many warranties are for 50,000 hours or 3 to 5 years. Not having to replace the lights every year can provide huge labor and relamping cost savings. However, this warranty usually only guarantees the fixtures to 70% of initial lumen output (a common standard used when lighting for humans); but since plant growth directly correlates to light output/light intensity, this warranty is not as promising as it should be. We know that as you increase the amount of light the plants receives, you essentially increase the biomass of the plant (until they reach a point where too much light can be harmful and cause tip burn etc.). For HPS, a rule of thumb is that the light degrades 1% every 1,000 hours. Most supplemental HPS fixtures are used for 2,500-5,000 hours per year and replaced every year, only losing 2.5-5% of light output in that time. Therefore an LED fixture that is guaranteed to last for 5 years but has a decreased light output of up to 30% is not ideal for growers who want to maintain a constant annual yield. You can combat this by driving the LEDs harder, for example, but then you shorten their lifetime and we go back to the cost savings benefit issue. There are currently no standards set for horticulture lighting, but that is something being addressed and something that will play a big role in the success of LED lighting.

One thing for certain was the awareness that LEDs are the future of this industry and it is only a matter of when, not if they will dominate. More research needs to be done, more education needs to happen, and a better dialogue between growers and lighting manufactures needs to take place. We are trying to help bridge this gap with our new one-day conference on horticulture lighting in Chicago this October. Please visit our website for more information on this conference and reach out to me if you would like to discuss the conference or the market stephaniep@pennwell.com.

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