Dimming to desired amount of light
Willaert also felt it was important to be able to dim the LED lights to a desired light intensity. Signify's GrowWise Control System provides this capability, allowing uniform light levels to be achieved throughout the day (and even throughout an entire growing season). This dimming option also allows growers to slowly awaken the crop by mimicking the rhythm of the sun or use grow lights up to 10% more efficiently. Willaert: "Because you use this system in combination with natural light to deliver a constant amount of light to the plants, you achieve a more uniform production. On a sunny day, for example, this quickly adds up to 1000 Joules/cm2/day of energy or 15 mol/m2 of daylight. If you then turn the lights on full, you end up with as much as about 2000 Joules/cm2/day, 30 mol/m2 in total. A traditional checkerboard distribution of lights would never result in an even light distribution for the crop. However, now that you can dim the lights, it is possible to distribute the light evenly over the crop." That, of course, also reduces power consumption, since the lamps only need to deliver the intensity the plant needs at that moment in time.
Switching to a new lighting system also includes a few challenges, of course. "At the outset, we really had to look at what was best in terms of light dimming," Willaert says. "Now that the days are growing longer, we need to address this again. In that respect, the first year is a matter of trying out many things." The growing process itself has also changed: "You have to create a narrow opening in the screen through which the moisture can escape in time. By lighting with LEDs, you actually create a much more humid climate, and you then need minimal window positions to allow the moisture to escape from below." Because the climate is more humid, it also affects the quality of pollen. Willaert decided to place more bumblebee nests in a future growing season: "The impact of artificial lighting on bumblebee behavior must be looked at more closely anyway," he concludes.