What is HPS and LED lights?

Published by Cretivity 2021-08-02

In the past, high-pressure sodium (HPS) lamps have always occupied a major position in plant planting lighting, so that many people still use HPS lamps. However, according to the global growing lighting trend in 2021, LED grow lights are on the rise, and LEDs will outperform HPS in all aspects. Here, we will carefully study their differences and the growers' expectations of each type.


Modern indoor planting methods have changed the way growers grow anything. Indoor greenhouses can fully control the growth medium, light, water, humidity, and temperature. This means that hobby gardeners and botanists can plant all year round without being restricted by seasonal changes.


For indoor planting, plant lighting is one of the most important conditions. As global indoor planting becomes more and more popular, plant lighting is also used by more and more people. How to use artificial lighting to create the same light as the natural spectrum? For the current human technology, it is very simple. The planting lighting industry has developed technologies for various lighting scenarios, including LED plant growth lights that can release different colors and spectrums.


We need to understand them before we can better choose the best plant supplement light for our indoor planting. Different spectrums, different light times, and light intensities have different effects on plants.


What are HPS and LED lights?


What are HPS and LED lights?


HPS is a more effective type of HID lighting than metal halides. The HPS bulb emits light in the yellow/red visible light and all other small parts of the visible light. Since HPS grow lights provide more energy in the red part of the spectrum, they may promote flowering and fruiting. They are used as a supplement to natural lighting in greenhouse lighting and full-spectrum lighting (metal halide), or as independent light sources for indoor/growth rooms.


LED grow lights vary according to usage. It is known from the study of photomorphogenesis that green, red, far-red, and blue light spectra have an effect on root formation, plant growth, and flowering, but there are not enough scientific studies or field tests to test the specific color ratios recommended by LED growth lights. It has been shown that if red and blue light are given, many plants will grow normally. However, many studies have shown that red and blue light only provide the most cost-effective growth method and that plants grow better under light supplementing green.


The white LED grow light provides a full spectrum and is designed to imitate natural light and provide plants with a balanced spectrum of red, blue, and green. The spectrum used varies, but the white LED grow lights are designed to emit similar amounts of red and blue light, and the added green light will appear white. White LED lights are usually used for supplementary lighting in homes and office spaces.


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The effect of the lighting system of the plant growth light


The luminous efficiency of the plant growth lamp can be expressed by a basic formula: output (lumens) divided by the total power consumption unit (watts). Efficient lighting is generally considered to output at least 90 lumens per watt (lm/W), with some bulbs reaching 150 lm/W or higher. Increasingly, growth lights are also rated according to PAR output, in µmol/s (the number of photons falling on 1 square meter of plant material per second) as the unit. The higher the mole value, the more beneficial the plant growth.


Mmol/s is increasingly seen as an advantage of gardening lights because it is an indicator of the available light for plants. Lm/W is an indicator that measures the visibility of the human eye.

Therefore, it is best to understand how to calculate the PAR output measurement value. The energy used by plants is mainly between 400 and 700 nanometers.

The light output in this wavelength range is called photosynthetically active radiation or PAR. The spectral component of solar radiation that is effective for plant photosynthesis is called photosynthetically active radiation (PAR, photosynthetically active radiation), with a wavelength range of 380 to 710 nanometers, which basically coincides with visible light.

The proportion of photosynthetically active radiation in the direct solar radiation increases with the increase of the solar altitude, up to 45%. In scattered radiation, the proportion of photosynthetically active radiation can reach as much as 60 to 70%, so cloudy days increase the proportion of PAR. On average, photosynthetically active radiation accounts for about 50% of the total solar radiation.


The LED grow light is very good in terms of PAR output. This is because, in addition to the PAR range, the LED grow light can also customize UV and IR light radiation. These two kinds of light play a very important role in plant growth.

LED is currently the best choice for plant lighting. It is currently the best competitor in terms of spectrum. It not only provides the best visible light but can also provide special light such as UV and IR.


How plant lighting affects yield


led grow light for indoor plant


Since light is one of the two most basic foods for any plant (water is the other), it naturally has a major impact on the final yield. Annual flowering species follow very strict temperature, day and light hours, and spectral patterns.


LED growth light lighting directly affects all growth cycles of plants, and light is essential at every stage from seedling to flowering and fruiting. The intensity and duration of light can be controlled to control the growth of plants.



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