How Do LED Grow Lights Work?

27Aug '18

How Do LED Grow Lights Work?

 

What You Should Know About LED Grow Lights

Energy-efficient LED grow lights are the lighting of the future of agriculture. They are not only economic in their use but they produce better plants as well, in comparison to all traditional lighting options. In the texts below you can read how the LED grow lights work, how they affect plant growth and what advantages the LED lights have over the thus far most widely used artifical lighting in agriculture – HPS lamps.

What are LEDs and how do they work?

LEDs (Light Emitting Diode) are small electronic components made of two different types of semiconductor material, one having a negative charge, called electrons, and the other having a positive charge, called holes. When voltage is properly applied over an LED, electric current starts to flow through it making electrons and holes start to collide releasing energy in the form of photons, light quanta, in a process called recombination. The first LEDs had relatively low light output and limited selections of colors while modern LEDs have high brightness and come in varieties of colors in visible, infrared and ultraviolet spectral ranges.

LED Chip Close-Up

 

 

 

 


A typical LED chip.

What are LED grow lights?

As suggested by their name, LED grow lights are luminaires utilizing LED chips in a modern and efficient way to produce light for growing plants. LED grow lights come in many shapes and sizes but as the most essential units of LED grow lights LED chips have most of the effect on the quality of the light, i.e. spectrum (colors) and photon flux (“brightness”) produced. Since LED grow light manufacturers can choose the LEDs they use in their lamps, it is important to understand which kind of LED grow light best fits the specific application. One of the advantages of LED grow lights compared to traditional lighting solutions is the ability to match the light to the needs of plants.

What is the effect of LED grow lights on plants?

Color variations of the LED grow lights are directly connected to the intended purpose – various studies have shown that certain colors influence plant growth, affecting root and flower formation (blue and red light spectra) which practically means that the majority of plant sorts will complete a normal growth cycle if exposed to both blue and red grow lights. Adding other colors to the spectrum, such as green, far-red and deep-blue aids this process by giving plants more information about its environment and overall resulting in higher quality plants (quicker growth, more secondary metabolite accumulation etc). A spectrum that contains all colors is called full spectrum and mostly resembles the sunlight. If it has high proportions of green, the light will appear white to human eyes and while not a crucial factor for plant growth, it does make the work around these lights easier and makes visual inspection of the plants possible. (Read more: Why Is LED Grow Light Purple?)

White LED Grow Lights Full SpectrumPink LED Grow Lights Full Spectrum

 

 

 

 


White and pink LED grow lights (both are full spectrum LED grow lights). Left – Valoya NS1, Right – Valoya AP673L.

How do plants react to different light colors?

Electromagnetic Radiation Visible Light LED Grow Lights

 

 

 

 

 

UV: PROTECTIVE MEASURES to high light conditions and stimulation of insect repelling chemicals. Enhances pigment accumulation in leaves, affects leaf and plant morphology.

 

Blue: Signal for lack of neighbors, no need to compete for light. Stimulates stomatal opening, stem elongation inhibition, thicker leaves, orientation to light and photoperiodic flowering.

 

Green, Yellow, Orange: Signal of neighbors, competition for light. Responses opposite to blue light; stomatal closure, some shade avoidance symptoms, enhanced photosynthesis in deeper cell layers.

 

 

Red: Lack of neighbors signal. Main component needed for photosynthesis, stem elongation inhibition, signal light

 

 

Far-red: signal light; Signal of neighbors, competition for light. elongation, flowering.

 

 

 

Through research we can determine what the optimal light for plant growth is. It is important to consider that different plants react differently to various light treatments (even different strains of the same plant). Additionally, a plant in its flowering phase may require a different light treatment as opposed to when it is in the vegetative stage. When it comes to the light itself, several parameters can be modified:

  • Light spectrum (the combination of colors used to produce the light)
  • Light intensity (typically measured in micromoles, the amount of photons projected onto the plants)
  • Photoperiod (number of hours a plant is exposed to light within a 24 hour period)
  • Light uniformity (the degree to which the light is equally distributed across the canopy)

In other words, LED grow lights users need to exercise a tailor-made approach when raising crops due to the fact that each plant species has different needs. In practical terms this means conducting trials before going to large scale production. (Read more: 8 Tips for Setting Up Successful Plant Trials with LED)

An alternative to that is purchasing the LED grow lights from companies that are dedicated to research and provide this data to their customers.

Discover Revolutionary Advantages of LED Grow Lights

In its early stages, LED technology was perceived as rather impractical and cost-inefficient. With the newest technology advances LED grow lights production has become cost-effective. Additionally, the range of available LED chip types facilitated the development of a more efficient plant cultivation industry. When set side-by-side with the traditional HPS (high-pressure-sodium) systems, LEDs win in terms of energy efficiency, the quality of plants cultivated as well as environmental friendliness.

LEDs are simple but powerful, energy-efficient plant growth lamps in comparison to the predominantly used HPS lights that are gradually being perceived as bulky yet less robust. HPS lamps have a shorter life span  which makes them more expensive in the long run. The heat emitted by HPS lamps is sometimes good and effective in greenhouse settings but makes them practically useless for vertical farms or growth chambers.   LEDs are faster switching, more compact (smaller in size), and are perceived as more beneficial for the environment. In addition, LED grow lights release less incandescent heat which affects the moisture and nutrition requirements of plants. The small amount of heat that is emitted is emitted upwards and away from plants unlike with HPS where the heat goes directly onto them increasing the leaf surface temperature and sometimes burning the plants.

In essence, the revolutionary advantages of LEDs in comparison to the conventional HPS lights are:

·       Economic electricity consumption  –  LED grow lights utilize up 50% of the energy that HPS systems use and some experts anticipate even a higher LEDs efficiency in the near future

·       Longer lifespan / lamp durability – LEDs have a longer life span in comparison to the HPS lights; for the comparison’s sake, the HPS lamps can last for 1 year while the LEDs might  last even up to 8 years (which translates into 50 000 hours of use)

·       Smaller spaces convenience – as the LED grow lamps can be set closer to the plants,  the growing space does not need to be extremely high or wide

·       Energy efficiency – with LED grow lights it is possible to optimize the spectrum by concentrating energy on wavelengths (colors) that are most beneficial for each application and plant. In addition, reduced heat production allows putting LED fixtures closer to plants ensuring less light is lost elsewhere.

·       Fire safety – as LEDs do not become very warm in comparison to the conventional HPS lamps they are safer to use

·       Dimming – while the majority of HPS lamps use the full light intensity, LED grow lights can dim even with a remote control or via an app and therefore are easier to handle, apart from consuming less power

·       Better crops – various trials have shown that LED grow lights produce better crops in terms of plants getting bigger and growing faster, compared to the HPS lights. Additionaly, LEDs can be made with a spectrum aimed at a specific goal such as anthocyanin accumulation, flowering inhibition, enhanced rooting etc.

·       More environment safety – due to the fact that less heat is emitted and that UV light can be added in LED lamps, there is less chance for bacteria and mold formation which subsequently means less pesticides and less environment pollution