Effectiveness, efficiency and spectra. What is more important for a crop and its investment in technology?

Generally, when you are going to invest in the purchase of LED luminaires, questions arise such as: What coverage in square meters does it have, what is its energy consumption, what spectrum is the most suitable for my crop or crop phase… and, in general, the average user is usually guided by the area coverage rather than by other parameters, but is that correct? The answer is simply no, it will depend on the type of crop, specific phase, type of installation and objective.

Generally, any crop grows with any type of light, but after a few days, you can clearly see if at a morphological level we are giving adequate light and if the crop is gaining biomass, over elongating, correct (and natural) growth of leaves, root system, etc.

Valoya NS12 spectrum for microgreens Credits by: Cantábrica Agricultura Urbana

In general, users tend to want the maximum efficacy measured in micromoles per joule (umol/J) because having more efficacy means having a higher output or photon output per watt of consumption (PPF), but if the spectrum is not adequate, no matter how much output the luminaire has, at the morphological (and organoleptic) level, the desired effects will not be achieved. This is also due to the fact that there is a tendency to think that having more output, more area can be covered with fewer LED luminaires and this concept is erroneous since it will also depend on the aperture of the LED emission angle, the thermal dissipation of the luminaire, the reflectivity of the room, the interface between LED and crop (polycarbonate or glass), whether they have built-in light reflectors or concentric lenses, and the structure of the luminaire.

To achieve maximum efficacy, LED luminaire manufacturers usually put either all LEDs in blue and red colors or with very few white LEDs. This is because having only one color to reproduce, the energy required is usually lower but the photonic values increase (umol/J or watt), therefore they are more efficient than those containing white (warm or cold) which is the opposite, more energy is needed to reproduce the entire PAR range (several colors: RGB). These spectra, which are red and blue (R/B), usually have an efficiency of between 2.8 and 3.4umol/J at present, and are usually complementary spectra to sunlight in greenhouses or specific spectra for specific stages of the plant, e.g. the germination stage.

Red and Blue commun spectrum

When you have more white LEDs, what usually happens is that the energy required to reproduce the colors within the PAR range increases so, by logic, to reproduce more colors in a semiconductor, the energy is divided into more parts so the efficiency plummets if we compare it with a single color. Having white guarantees more wavelengths but it will also depend on the composition of the LED, i.e. whether it is cool, neutral or warm white. Cool whites (5000-6500K) contain more proportion of blue, warm whites (2000-3000K) more proportion of red and neutral whites usually have more reds than blues but in proportion there is not as much disparity as there can be in the other two cases.

General full spectrum

Natural sunlight usually has values between 4000K and 5000K, being 4500K a correct and generalized average. For this reason, most manufacturers of LED luminaires that sell “full spectrum” usually incorporate a mixture of LEDs, mostly white with a lower percentage of specific red or blue LEDs, so that when everything is mixed on the same PCB, it is a full spectrum in the PAR range with peaks of red or blue, since it has been shown that the main photoreceptors involved in photosynthesis are chlorophyll A and B.

Valoya, on the other hand, is a manufacturer that has dedicated itself almost entirely to making unique spectra with more specific LEDs and, not only red and blue, but also mixing UV-A (380-390nm), different blues (410 and 450nm), red (660nm), far red (730-740nm) and, in their self-developed target, emitting up to 820nm which is infrared (heat). Due to this mix of specific colors and extensive whites, Valoya’s efficacy currently stands at 2.6-2.5umol/J as it is ultimately an average of all the LEDs incorporated in the luminaire, so it is somewhat lower than the average LED luminaire manufacturer. This does not mean that its performance is worse than luminaires that emit more umol/J and, neither does it mean that it covers less area than others, it simply means that by having a much more complete spectrum than other luminaires that may only incorporate specific whites and reds, its average performance drops but, by having a more complete spectrum in peaks of the main photoreceptors (Cryptochromes, carotenoids, chlorophylls A/B, phytochromes), the incidence of Valoya’s spectrum will be much higher than having something less complete but more effective at the photonic level.

Valoya Solray385 spectrum

Therefore, we can draw a clear conclusion, and that is that not everything is based on the efficiency of the luminaire to cover more and better a specific area, but rather that color composition is directly involved in the effectiveness, but that won’t mean it’s a worse performance. Here it must be emphasized that not everything goes, it is also necessary to know how to compensate the ratios of B:G (blue, green) and R:FR (red, far red) but that can only be known by conducting continuous studies with different varieties of plants and different ratios to reach conclusions on how the mixture of colors affects the different crops. That is R&D and it usually takes years to reach concrete conclusions and optimal ratios, that is why at Virex, we are committed to Valoya and its continuous R&D in prestigious universities and research centers in different countries. Very few manufacturing companies have the human and capital capacity to carry out these continuous studies over time and this is an added value that we must add in the equation of the choice of one manufacturer or another.

To conclude, what we should really ask ourselves when investing in an LED luminaire would be the spectrum primarily, followed by power consumption, heat dissipation capacity, footprint (coverage), IP protection, ease of installation and operation, and warranty against manufacturing defects.. All of this will directly influence the fixed costs of a facility over time. Better spectrum, better crop yield, higher productivity, higher organoleptic content, higher morphological uniformity, lower maintenance cost and, therefore, less time to amortize the investment.

Valoya DNA-8 luminaires in visitable culture chamber

Ask us about your project to recommend the luminaire with the best spectra to suit your crop and objectives.

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