Is a plant able to make optimal use of all the light in the greenhouse? Lighting specialists use "light utilisation efficiency" to measure this. This is an important factor to consider when looking at how efficiently the plant converts photons into growth. Ramón de Vrie from the lighting consultancy Ledgnd explains this, and argues for a dynamic control for LED lighting.
Orchid grower Jan bought a hybrid LED installation with 5% blue and 95% red LEDs with an efficiency of 3.2 micromol/Watt. He gives light to his crop for 16 hours a day as standard. Data showed that the efficiency of photosynthesis decreases after 13 hours. This means that 20% of the energy used is less efficient. Although Jan has chosen a spectrum with a high efficiency of 3.2 micromol/Watt, this is less efficient when you look at the light utilisation efficiency of the crop.
Light utilisation efficiency
Light utilisation efficiency describes how efficiently a plant converts phtons into growing energy, Ramón points out. "This can depend on the crop, the colour of the LEDs but also the climate. You can grasp this by measuring what is optimal for the crop and what gives the best return on your investment. One way for achieving optimal light use is a dynamic control that would allow to individually set the different colours of LED in a fixture."
By applying dynamic control, Ledgnd sees a direct cost increase of 15-20% per luminaire. Ramón: "The dynamic control is programmed based on the specific needs of the crop, in the specific greenhouse of the grower. It is therefore essential that the grower installs the right sensors in their greenhouse. And the grower can then see that information in MyLedgnd."
Dynamic control of supplemental lighting has many advantages for the crop and the wallet. "Save energy and extend the life of the LED," he explains."But it also maximise the use of natural light with total spectral understanding. It allows growers to achieve more consistent crop results, as well as optimise and recognise patterns; for example, more blue light in the morning or red to far-red ratio looking at PSS. A crop-specific light recipe gives your crop what it needs at the right time, and it can also quickly adapt to changing weather conditions."
"By programming the lighting based on the data in the greenhouse, we are setting the next level of sustainable light in greenhouse horticulture. It gives optimal results with the least energy consumption. In studies, we see that dynamic control of LEDs has produced yield increases of 10% and net energy savings of 30%."