How to choose grow lights for commercial cultivation?
Sunlight is the basis for the existence of life on Earth, an inexhaustible source that energizes all living things. For green plants, light is essential for the process of photosynthesis. If you do not get distracted by intermediate reactions, then from carbon dioxide CO2 and water H2O, plants synthesize, in the presence of chlorophyll, the simplest organic compound – glucose:
6CO2 + 6H2O → C6H12O6 + 6O2
This is the primary building material. Later, using phosphorus, nitrogen and potassium, the plant produces from this semi-finished product all the compounds it needs for normal development. In the process of photosynthesis, plants absorb carbon dioxide and release oxygen.
Influence of the light spectrum on biochemical processes
Solar white is a mixture of radiation of different colors, with a peak in the region of green and, partially, yellow (480-580 nm). In the same range, the human eye is most sensitive. For photosynthesis, the most important are the blue (430-460 nm) and red (640-670 nm) components of the spectrum. Plants absorb these frequencies, receiving energy, and reflect green light. Actually, this explains the green color of the leaves and stems.
The ratio of blue to red should be different, depending on the stage of development of the plant. So the blue color is especially important during the growing season, when rapid growth occurs and the bush is gaining green and root mass. With its lack, plants stretch out, remaining thin and unstable. By adding blue light at the stage of growth, we get dense, bright green stalwarts, ready, in the allotted time, for intense flowering.
An increase in the proportion of red in the solar spectrum occurs in autumn, along with a decrease in daylight hours. As well as changing the lighting regime, for example from 18/6 to 12/12, this gives the photoperiodic varieties a signal for the beginning of the reproductive period. Red light initiates flowering and stimulates the growth of inflorescences.
Current state of affairs. HPS grow lights
Discharge grow lights are the most common type of grow box lighting. They are simple, relatively inexpensive, and most importantly, familiar. Methods for calculating illumination have been worked out, the grow lights themselves, ballasts or electronic ballasts are available, methods for removing heat have been invented. A working version, which has its poles and minuses. The latter include:
Low efficiency – no more than 30%;
The predominance of yellow in the spectrum – which further reduces efficiency;
The release of a large amount of heat – 70% of the power goes to heating the grow light;
High energy consumption – as a result of the factors listed above.
So, the efficiency of HPS grow lights is 30% … This result can be considered good if they are used to illuminate streets or premises. The design of the grow light is designed in such a way that its emission spectrum is shifted to the yellow (and partially green) part of the spectrum, which is best perceived by our eyes. Thanks to this, the lighting appears brighter, and the outlines of objects are clear and contrasting (a similar effect is given by yellow fog lights). But the blue and red parts of the spectrum are important for the plant!
In order to achieve enough light in the required ranges, the overall illumination level must be increased. This solves the issue of red, which is necessary during the flowering period, but the lack of blue during the growing season remains in this case. Some growers practice, at this time, supplementary lighting with DRI or ESL grow lights, which have a higher color temperature, but this complicates the lighting system and leads to even greater energy consumption.
High energy consumption, apart from higher electricity bills, leads to excessive heating in the grow box. This entails an increase in the power of the fans, the use of more efficient, and therefore more expensive, carbon filters, the use of expensive cooled grow lights.
LED alternative. grow lights
A feature of LEDs is a narrow spectrum of light emission. When creating grow lights for home use, this is a major headache for developers. To create white color, the principle of RGB (Red Green Blue) is used – mixing of red, green and blue colors. Here is the first loophole for saving – we don’t need green! grow lights, specially designed for plant illumination, emit only in the “useful” range required by plants for photosynthesis.
When choosing LED lighting, it should be borne in mind that only specialized LEDs completely fall into the spectrum. The maximum absorption efficiency for chlorophyll a is 430 and 662 nm, and for chlorophyll b – 453 and 642 nm. In the characteristics of the diodes, the ranges are indicated, and one should be guided by them, taking into account, first of all, chlorophyll a – it is more important for photosynthesis. LEDs intended for domestic and technical purposes have different spectra and are not suitable for use in greenhouses.
The advanced luminaires provide for the adjustment of the ratio of red and blue, depending on the stage of plant development. This is done simply by turning off some of the red or blue LEDs. The normal ratio is 4-6 reds to one blue.
So, how do we get more efficiency of commercial LED grow lights , which will allow using lower wattage grow lights?
Pros of commercial LED grow lights
- Highest efficiency compared to all other light sources;
- Precise hit of light within the effective absorption range. Up to 95% of the grow light radiation will be used for photosynthesis;
- Due to the lower temperature, LED lights can be placed closer to the plants, which will also increase the lighting efficiency;
- Easily adjust the ratio of blue to red in lighting, establishing a favorable spectrum for vegetation or flowering;
- The lower power of the luminaires, reduces the requirements for ventilation performance. You can get by with fans of lower power, carbon filters of lower performance. The noise level and power consumption will be lower.
The only significant disadvantage of commercial LED grow lights is their high cost. However, the trends are encouraging. The price of LEDs is steadily decreasing, and their efficiency is steadily increasing. So it is quite possible that we are witnessing the end of the era of discharge grow lights, and the beginning of the era of LEDs.