"As we all know, plants use light to transform water and carbon dioxide into glycogen. However, not all wavelengths are equally efficient or as important. For instance, we know that red, blue, and far-red are the most efficient wavelengths, but also that they each have their individual response in growth in the different stages of the plant life cycle. Yet, plants can only use a certain amount of light. Meaning that we have to be cautious on desolating energy by supplying too much light to a plant since that could turn into a huge waste," notes Ryan Rosenberg, Chief Technical Officer at LED iBond, a Danish lighting supplier for CEA growers.
Two ways to increase energy efficiency
According to Ryan, there are two dimensions to increasing energy efficiency when choosing LED lighting solutions. The first is on the crop level, mainly determining the optimal spectrum and intensity for your crops in the different plant life stages. Secondly, the engineering part. When knowing which spectra to use, the exact light solution and growth area must be designed to utilize the power that's put into the system in the best way possible.
Besides that, it's given that certain plant characteristics can be stressed based on the light supplemented. This makes it interesting for growers to research some set objectives in the propagation stage and other growth phases. The company designs its spectra according to the following plant phases; the sprouting phase, the vegetative/growth phase, and the pre-harvesting phase. LED iBond is working on spectra that are specifically focusing on the pre-harvesting stage that can emphasize the crop flavor, color, texture, and other quality parameters to maximize the yield value. Having light as a controllable parameter, all the responsibility over a plant's yield is given to the grower now.
Breaking down the components
According to Ryan, there are three rules of thumb. First, choose highly efficient LEDs, combine them to the required spectrum, building them into the growth area as closely as possible to decrease the loss, secure a high uniformity and at the same time, keep the LEDs cool.
"Our design philosophy is to utilize every watt entering the system to support growth. We use only high-effective and high-quality LEDs on the market by ultimately aiming to find the best individual LEDs and combining them with the preferred spectra. We, therefore, strive to choose LEDs with efficiencies of 3.5, 3.6, and even 3.7µmol/s/W," Ryan affirms.
LED iBond combines its LEDs with 2 to 4 diodes of different colors to customize the light emitted as close to the preferred spectrum as possible. Plus, combining that with various LEDs if necessary. To keep the LEDs as efficient as possible, the LEDs are cooled by the design construction, meaning that the efficiency has been improved by 8%, as the company claims.
"Second, we do recommend bringing the light as close to the plant as possible. That's done to use the photons as efficiently as possible for the plant's growth. By bringing the light closer to the plant, it's not just bouncing around from hitting water particles, but it now keeps the light on the growing bed. To maximize yield, the light must be uniformly distributed. Not only in one height at the base of the plant but starting from 2cm and up to the maximum height of the crop," Ryan notes.
"And thirdly, we do not want the light to slip away – but to be reflected for the Chlorophyll in the plant cells. Therefore, we use reflective materials in our design. And we do recommend the use of reflective materials to confine the growth area."
How do you tackle the increasing costs?
- You chose a high-quality/highly efficient LED providing a minimum of 3,3 umol/s/watt.
- Operate them as cold as possible – but do not waste energy on cooling.
- You fit the led with optics/reflectors and lenses to direct the photons in the direction you want them.
- (move the light as close to the crop as possible) reduce loss
- Secure a uniform light level at the entire growth area - this normally means many LEDs.
- Make the growth area reflective – so the plants get more than one chance to catch the photons.
What is the best advice for farmers to save on costs massively?
"Firstly, know the spectra and intensity your plants can absorb throughout their life cycle. Secondly, only use highly efficient LEDs to create the wanted light schedule. Thirdly, design an optimal growing field – to best utilize the energy you put into the system, as 30% cost savings on energy consumption is a good ambition."
"Ultimately, an efficient LED panel design should have a wall-plug power consumption of less than 75 Watt/m2 for a typical intensity of 200 umol/s. The farmer should look for that metric when considering growth light panels."
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Pia Stangerup, CEO