Dynamic LED lighting – optimal switching for plants, environment and efficiency

In the first article in this series, we covered all aspects of 2-, 3-, 4- (or even more) channel LED installations, a prerequisite for dynamic lighting. In this second article, we delve deeper into the key aspects of dynamic LED switching, focusing on balancing environmental factors, plant physiology, energy efficiency, and production optimization.

Switching to environmental needs: the balance between natural daylight and LED

The foundation for efficient lighting lies in seamless integration with available natural daylight. LED systems must be able to respond to real-time outdoor conditions, particularly the spectrum and intensity of sunlight. Different light colors (spectra) have specific effects on plant growth and development. The ideal approach is to measure the available spectral components outdoors and adjust the LED lighting accordingly. For example:

– Blue light: Once a certain threshold of blue photons (expressed in moles) is reached by sunlight, the blue component present in the LED lighting can be reduced or switched off during the day. This prevents overstimulation of the plant and unnecessary energy consumption, because blue is the least energy-efficient color to produce and should therefore be switched off first when not needed. With a “boost” function (such as in the Hortilux NXTLED fixture), you can, for example, direct the released energy towards more energy-efficient colors like red.

– Green light: When there is sufficient external green light, the green LEDs can be dimmed or switched off. Although green light is less efficient for photosynthesis than red and blue, it plays a role in deeper leaf penetration and plant morphology. It also creates a pleasant visual environment for greenhouse workers. A smart system adjusts this based on external conditions. Here too, the “boost” function is available when green light is not needed.

– Red light: The principle of adapting based on available daylight also applies to the red spectrum. Red light (wavelengths around 660 nm) is the most efficient color for photosynthesis and is therefore essential for plant growth and development. The aforementioned “boost” function allows you to maximize your available energy for growth. Moreover, red light, along with far-red light, is crucial for flowering and fruiting, and for regulating plant shape.

– Far-red light (wavelengths around 730 nm) has a significant influence on plant morphology and the timing of flowering. Plants use a special pigment, phytochrome, to “measure” the ratio of red to far-red light in their environment. This ratio acts as a signal: with a lot of red light, the plant remains compact, while an excess of far-red light indicates that the plant is in shade. The plant will then grow taller and more slender to capture more sunlight. Intelligently managing far-red light is essential for optimizing plant shape and controlling flowering.

Ideally, the total LED light level and intensity should be adjusted to the available natural sunlight. When the sun is dominant, unnecessary colors are switched off (because they are already present in sufficient quantities in the natural light). At those times, you can, for example, only illuminate with extra red to stimulate growth. When the LED lighting is dominant, the colors that are “deficient” in natural sunlight are boosted.

In addition to the spectrum, the total light intensity (expressed in Photosynthetic Photon Flux Density – PPFD) is crucial. LED systems must measure the external intensity and dynamically adjust their own output to ensure an optimal, constant light dose and perfect climatic conditions for the plant, without unnecessary lighting during high solar radiation.

Switching to plant needs: photosynthesis and physiology as a guide

The plant itself is the ultimate indicator of optimal lighting. By monitoring real-time information from the plant, LED lighting can be tailored to its physiological status. This results in more efficient use of light energy and healthier growth.

– Evaporation and water management: A plant with low transpiration can experience stress, for example, due to a lack of water or excessive humidity. In such situations, maintaining a high light intensity is counterproductive, as this can further increase the stress. Dynamic LED systems can dim the light intensity when a plant is experiencing insufficient transpiration, thus relieving the strain on the plant’s water absorption and transport systems.

– Photosynthesis optimization: A plant’s photosynthesis rate is directly related to light, but is also influenced by temperature and CO2 concentration. An advanced system integrates these parameters:

• Integration with climate computers: By linking data from temperature and CO2 sensors to the LED control system, the system can optimize light intensity and spectrum for maximum photosynthesis efficiency. For example, light intensity can be increased under optimal temperature and CO2 conditions, while it can be reduced under suboptimal conditions, saving energy and preventing further damage to the plant.
• Photosynthesis models: Using advanced photosynthesis models, the system can predict the optimal light strategy based on current conditions and specific crop needs.

– Leaf Area Index (LAI) and saturation point: The LAI (leaf area index) provides insight into the amount of leaf mass available for photosynthesis. As a crop grows and the LAI increases, so does the demand for photons, up to a certain saturation point. Smart LED systems, combined with your climate computer and sensors, can:

• Estimate or measure the LAI.
• Gradually increase the intensity (PPFD) as the LAI increases, until the plant is saturated and additional light has little or no added value for photosynthesis. This prevents wasted energy.

Switching to the energy market: cost and efficiency optimization

Energy is one of the largest costs in greenhouse horticulture. Dynamic LED lighting offers the opportunity to optimize energy consumption based on current energy prices and availability.

-Dynamic Cost Optimization Based on Energy Prices: By linking smart LED systems to real-time energy prices (spot market prices), lighting can be dynamically adjusted. The system intensifies the lighting during off-peak hours or periods with low energy prices (such as with Flexible Capacity Contracts – AFFR), while dimming or switching off during peak hours with high prices. This flexibility in switching on and off is essential for minimizing energy costs without compromising plant growth. Rapid switching on and off (within seconds, as is possible with Hortilux NXTLED) is essential.

– Battery combination: By combining LED systems with energy storage systems (batteries), renewable energy (e.g., solar power) or purchased electricity at off-peak rates can be stored. This stored energy can be used when energy prices are high or the external power supply is limited. This significantly increases the independence and efficiency of the energy system.

A 4-channel LED system offers additional possibilities. Instead of using all light channels simultaneously, the grower can adjust the lighting to the specific needs of the crop or the climatic conditions. For example, depending on the situation, they can choose to operate only the red LEDs, which are the most energy-efficient for photosynthesis. This allows the grower to optimally utilize the available stored energy and thus save even more on energy costs.

Switching to production needs: market-driven cultivation

In addition to physiological and energy aspects, the lighting strategy can also be tailored to commercial considerations, in particular the market prices of the product to be grown.

Peak production at high prices: If product prices are known to be high at certain times (e.g., holidays or specific seasons), LED lighting can be temporarily increased to accelerate growth and advance harvest, ensuring produce reaches the market at the most lucrative time. This requires close coordination between the lighting system and market intelligence.

But the question is: what choices will you make now that you have this option? Dynamic lighting allows you to fundamentally change your strategy. Will you choose to maximize growth with the goal of achieving more grams per square meter, or will you focus on quality by steering the plant toward higher Brix, better color, or longer shelf life?

This transforms the use of your dynamic lighting into a strategic tool. You can fine-tune your light recipes based on market demand and desired yield. You’re no longer dependent on fixed growing periods and spectrums, but can align your production with your optimal strategy or market demand.

A healthy work environment: connecting people and biology

A dynamic LED system takes into account not only the plant and its efficiency, but also the needs of the immediate environment, including workers and biological control agents.

-Bumblebees and biological control: Certain light spectra can influence the behavior of bumblebees and biological control agents. Too much blue light, for example, can be disorienting. The system can adjust the spectrum to create an optimal environment for the insects without hindering plant growth. This can involve reducing certain spectral components during specific periods.

-Human well-being and visual inspection: For greenhouse workers, a pleasant and safe lighting environment is essential. Monotonous purple light, which consists only of red and blue, can cause fatigue and discomfort. The addition of green light whitens the spectrum, which feels much more natural. This is not only pleasant for the workers but also crucial for visual inspections of the crops. You can assess the quality and health of the plants much more effectively with natural-looking lighting.

With a 4-channel system with dimming, you can also achieve this zoned approach. You adjust the color temperature and intensity to the areas where your employees are working. This creates a comfortable and safe work environment, while the lighting in the rest of the greenhouse is set for maximum growth and energy savings. You can even use only green light to create work lighting exclusively for areas in the greenhouse where harvesting is taking place and no supplemental lighting is needed. This means that instead of, for example, 1000W, slechts 150W per armatuur verbruikt op die locaties.

Conclusion

The transition to dynamic LED lighting in greenhouse horticulture represents a significant step forward in sustainability and efficiency. By intelligently adjusting lighting based on environmental conditions, plant physiology, energy prices, production needs, and the well-being of both people and plants, growers can not only improve their yield and quality but also significantly reduce their operational costs and minimize their environmental footprint. The future of greenhouse horticulture lies in such adaptive, data-driven systems that harness the power of technology to balance natural daylight and LED lighting.

Are you ready to take the next step in optimizing your cultivation with dynamic LED lighting?

We understand that implementing LED systems is becoming increasingly complex. Contact us for a personalized consultation about the optimal LED solution for your crop.