The term “dynamic lighting” is becoming more common in the world of precision agriculture. The concept of dynamically controlling artificial light is in its infancy, and as such the definition of exactly what constitutes “dynamic lighting” is not always consistent between sources. Sollum Technologies identifies four fundamental criteria for its lighting technology to be truly dynamic:
In this paper, we will break down these criteria and discuss the invaluable agricultural advantages that they present.
Being able to change a light’s output intensity means altering a fixture’s light both quantitatively and qualitatively. Out of the most common grow light options, LEDs provide significantly more freedom when it comes to managing output. Altering light intensity is most referred to as “dimming”, which provides the ability to reduce intensity down from full power levels.
Dimming is a desirable feature in a greenhouse because it allows the producer to save energy during periods where more solar radiation is available. Experts, however, often advise against dimming when it comes to high pressure sodium (HPS) or metal halide lights because it can limit the available light spectrum (Figure 1).
Alternatively, the output spectra of LED lights is relatively unchanged by dimming mechanisms (Elkins and Iersel, 2020). The reason for the discrepancy between the impacts of dimming HPS and HID lights versus LED has to do with temperature and with the dimming mechanism. With HID and HPS, light and heat production are intrinsically linked such that reducing the temperature of the lights will change the output spectrum – this means that reducing the power to the light fixture to dim the lights also reduces the heat production, which alters the spectrum. LEDs are the most energy efficient light fixtures – converting 47% of input power to light. Alternatively, HPS converts just 34% of input power to light and the rest of the energy is lost to heat. Thanks to the reduced heat production of LEDs, their light spectrum is primarily unchanged even when they are not operating at full power – i.e., are dimmed.
Compared to alternatives, LEDs allow enormous freedom in terms of spectral output with a variety of narrow and broad-spectrum fixtures available. The flexibility of a LED fixture’s output spectrum is due to the nature of diodes – each diode on a fixture can emit a different single wavelength, and with the help of a phosphor coating some diodes can emit a mixture of wavelengths to produce white light. Because LEDs are energy efficient and their cooling load is minimal, many diodes of varying outputs can be included on the same fixture – making broad and full spectrum options available. The output spectrum of HPS and metal halide fixtures is fixed and can only be changed using filters, or as mentioned previously, by changing the temperature of the light – making a dynamic change in the output spectrum unfeasible for these types of light.
Despite the perceived flexibility that LEDs offer, most LED options on the market deliver limited benefits to growers. While LEDs enable the manufacturer to create different light spectrum, the grower has to select a specific one and once delivered, that fixed spectrum cannot be changed. Narrow spectrum LED fixtures are a popular choice that offer growers a mixture of red and blue light – the two wavelengths that are most efficient for plant photosynthesis. However, these lights lack green, yellow, UV and far-red light which can offer plants a variety of other benefits related to plant morphology, disease resistance, photosynthesis, etc. (Johkan et al., 2012; Meyer et al., 2021; Tan et al., 2021). Broad spectrum lights are also available so that plants have access to wavelengths other than red and blue, but the energy efficiency is reduced by the phosphorous coating used on diodes to create a broad-spectrum output.
When acquiring a dynamic lighting solution, the grower shall have a system that can both managed in intensity and spectrum output.
Sollum Technologies is the only LED grow lights provider that offers a truly dynamic output enabling the optimal combination of broad- and narrow-spectrum light recipes that can be used to perfectly recreate sunlight, precisely apply far-red light to control morphology, emphasize red and blue for rapid periods of growth and allow growers the freedom to change their lighting strategy as research evolves.
It is one thing to have the ability to change the output of a lighting system, but it is another to always have complete remote control and monitoring capabilities of the lighting system at all times. For most grow lights, programming capabilities are as basic as using a timer to turn lights “on” and “off” for photoperiod management. A truly dynamic lighting solution is one that allows growers to input commands and light recipes – such as programming lights to transition smoothly from a sunrise spectrum to a sunset spectrum.
The controlled application of different spectrums is what is meant by light recipe. When baking a cake, it is not enough to have a list of ingredients – a recipe must include instructions on when to incorporate the ingredients and in what quantities; a light recipe accomplishes the same thing: it is a program that controls the application timing and intensity of different spectra.
With Sollum’s dynamic lighting solution, growers can implement an unlimited number of recipes and have access to expert consultation on recipe choice informed by the most recent research.
Another novel advancement that truly dynamic lights offer is the ability to program fixtures collectively and spatially. Instead of programming one light at a time, an entire greenhouse lighting layout can be managed. Sollum’s dynamic solution allows greenhouse lighting to be programmed by zone (Figure 2), providing a number of benefits: for instance, a light recipe can follow seedlings as they are transported from a misting room to a different location equipped with driplines, or a greenhouse space can be easily adapted to introduce a new crop native to a different geographical region.
While other lighting providers may offer custom lighting to growers, they do not allow these lights to be re-programmed in the future. A truly dynamic solution adapts to a grower’s strategy as it changes over time with evolving research and consumer demand. Sollum’s smart LED lighting solution allows users to execute an infinite number of light recipes that can be changed and scheduled over time.
Iersel, M. W. van, Gianino, D. (2017). An Adaptive Control Approach for Light-emitting Diode Lights Can Reduce the Energy Costs of Supplemental Lighting in Greenhouses. HortScience, 52(1), 72–77. https://doi.org/10.21273/HORTSCI11385-16
Johkan, M., Shoji, K., Goto, F., Hahida, S., Yoshihara, T. (2012). Effect of green light wavelength and intensity on photomorphogenesis and photosynthesis in Lactuca sativa. Environmental and Experimental Botany, 75,128–133. https://doi.org/10.1016/j.envexpbot.2011.08.010
Meyer, P., Van de Poel, B., De Coninck, B. (2021). UV-B light and its application potential to reduce disease and pest incidence in crops. Horticulture Research, 8(1), 1–20. https://doi.org/10.1038/s41438-021-00629-5
Tan, T., Li, S., Fan, Y., Wang, Z., Ali Raza, M., Shafiq, I., … Yang, W. (2021). Far-red light: A regulator of plant morphology and photosynthetic capacity. The Crop Journal. https://doi.org/10.1016/j.cj.2021.06.007
To Dim or Not to Dim Your Grow Lights: That is the Question. (2016, June 5). Retrieved January 20, 2022, from https://eyehortilux.com/grow-lights-grow/to-dim-or-not-to-dim-your-grow-lights-that-is-the-question/