Introduction
According to a market research report (1) the LED market is expected to grow to over $1,9 trillion by 2020. With increased awareness of its benefits, LED plant grow lighting is expected to witness a phase of great growth in the coming years in applications such as vertical agriculture, commercial greenhouses and indoor urban plantations. In addition, the upward trend of indoor growing, government regulations favoring LED lighting, and the requirement for energy-efficient and durable lighting technology to supplement natural lighting for plant growth, drives market growth. of LED solutions. A grow light or horticultural light is an artificial light source, usually an electric light, designed to stimulate plant growth by emitting an electromagnetic spectrum appropriate for photosynthesis. Grow lights are used in applications where there is no natural light or where supplemental light is required. These Light Emitting Diode (LED) fixtures may be relatively new to the grow light market, but they have become very popular due to their energy efficiency, dimmability, and long life cycle.
Spectrum Specific
Typically LED grow lights combine different colors to achieve a specific wavelength for different types of plants. They can be designed with a specific color to provide optimal growth and yields because they have different wavelengths and plants respond favorably to these wavelengths with respect to the light spectrum. For example, the wavelength of red light is around 630-660nm and is essential for stem growth as well as leaf expansion. As for the wavelength of blue light, although it is only 400-520nm, it increases the chlorophyll content present in the plant and the thickness of the leaf. Since the LED is effectively a diode, its forward current curves and voltage (Vf) characteristics of various colors are different. In the table below we can see these differences. As shown in table 1, with a forward current of 20mA, the Vf for a standard red LED is 1,8V and 3,6V for a blue LED. To achieve a specific wavelength by combining different colored LEDs, the total Vf range is wide and varied. We will need an LED driver that operates in a wide constant current region so that it can be used with different LED grow lights.
Energy efficiency
As we have been indicating, an individual LED could emit a specific color of light. Below is an illustration of the spectral output of a red LED (red curve) and a typical HPS lamp (rainbow curve). We can see how narrow the LED light output is compared to the HPS lamp: LEDs are special in that they produce a very narrow range of colored light on the electromagnetic spectrum, like the red curve shown in figure 2. All the energy used to create light outside the PAR region is wasted to a greater or lesser degree. The PAR (photosynthetically active radiation) region that plants can use in the photosynthesis process is 400 to 700 nanometers.
This is precisely why LEDs are "more efficient" than HIDs. In terms of lumens per watt, double ended HPS lights are quite efficient compared to other types of traditional artificial lighting, producing over 100 lumens per watt. However, when we consider LEDs, the light output exceeds 300 lumens per watt. In other words, the efficacy of LED grow light is about 3 times higher than HPS light. Therefore, we must take into account that in order for the LED luminaire to provide high efficiency, the LED driver must also have efficient voltage conversion capability. Lifespan In all types of fixtures, the amount of light emitted (measured in lumens or PAR photon irradiance) decreases with use. For example, the output of HID lamps can degrade by 10-15% after just one year of operation and in the case of HPS, as they degrade, the spectrum shifts towards the green/yellow range, which is the range of spectrum less used by plants.
For this reason, most professional growers replace their HID bulbs at least once a year. However, grow LEDs are guaranteed to have a lifespan of at least 50.000 hours with less than 10% loss in output and often continue to operate beyond specification with little or no change in spectrum. In a good installation of LED luminaires for horticulture, a reliable and well-qualified LED driver cannot be missing.
dimmed
Theoretically with the LEDs we have more control over the intensity of the light since the LEDs are dimmable. Dimming is important because the amount of light provided is associated with photosynthesis. In facilities with too much light, energy is converted into heat and photosynthetic activity decreases. Each plant is different in this sense, even during the life cycle the behavior of each plant also varies. The dimmable capability of LEDs offers the distinct advantage of creating the best lighting environment tailored to the various needs of plants depending on their growth phase. For certain horticultural crops, luminaires equipped with a dimmable LED driver are much more widely used than those equipped with non-dimmable drivers.
Summary
In general, LED luminaires can offer us an optimal spectral range, high energy efficiency, long useful life and regulation, but all this will depend on the integrated LED driver that composes them. MEAN WELL ELG, HLG and HVG LED driver series, offering up to 5-7 years warranty, wide constant current range, 3-in-1 dimming function, high working temperature and IP67/IP65 anti-humidity permeability , are highly recommended for LED luminaires in horticulture crops. In addition, its efficiency with up to 95% use of LED light ensures greater efficiency compared to HPS-type grow lights.
