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How to evaluate the advantages and disadvantages of plant growth lights ?

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Author : Rachel
Update time : 2021-07-26 13:12:05
Usually growers use high-pressure sodium lamps as supplementary photosynthesis lighting, and incandescent lamps and compact fluorescent lamps are used for photoperiod lighting of greenhouse crops. Equipment used for cultivation and breeding usually uses a single electric light source, mainly fluorescent lamps and occasionally assisted by incandescent lamps. Fill light usually requires high light intensity (At least 50–100μmol m-2 s-1), this can improve photosynthesis and promote plant growth. The photoperiod lighting requires low light intensity to adjust the flowering period of crops. With the development of LED lighting technology and cost reduction, LED lights have been widely used in the field of lighting, including the production of horticultural crops.

Visible Light

LED lights have several advantages over traditional lights:
1)LEDs can emit light in a narrow band, which helps to produce a specific (sometimes adjustable) spectrum.
2)LED generates less radiant heat.
3)The LED has a longer working life.
4)A single LED has low power and small size, allowing small power, low-wattage lamps to be placed closer to plants.
5)LED can be reduced its beam angle by design, so that the plant surface can obtain the maximum amount of light and improve the efficiency of light utilization.

characteristics of electrical and visible light

The characteristics of electrical and visible light 
Just like the lamps designed for residential and commercial lighting users, growers are concerned about the voltage, current, and power consumption of the lighting system. Since the illumination provided by horticultural lamps plays an important role in helping observe the subtle color differences caused by plant nutrition, disease, tiny insects, color, and other stresses, lamp visual indicators (lumine output, CRI, and CCT) are useful. Although these indicators do not directly play a role in botany. The highest value of CRI is 100 (daylight), the value of white LED is usually more than 90, the CRI of high pressure sodium lamp is 24, and the light CRI of some lamps will be negative. CCT represents the temperature of the light color, the unit is Kelvin. Light from lamps with a CCT lower than 3200k is considered warm (reddish in color), while light from lamps with a CCT higher than 4000k is considered cold (bluish in color). The relationship between temperature and color is based on Wien's law, that the wavelength producing the maximum amount of radiation is inversely proportional to the surface temperature (degrees Kelvin) of the radiation source. 

LED Light Spectral Band

Spectral Band
The solar radiation band defined by PAR (400~700 nm) is slightly different from the visible solar spectrum (380~780 nm) of the human eye. In addition, ultraviolet (300-399 nm) including UV-B (280-315 nm) and UV-A (315-399 nm) and far-red light (sometimes defined as 700-799 nm) radiation will affect plant growth and development. Infrared thermal radiation (800 nm~1 mm) can also affect plant growth and development. The latter is more difficult to quantify, primarily affecting the plant temperature, and therefore is not included in the identification proposal. It is recommended to make an identification form, which quantifies the correlation between ultraviolet (300-399nm), blue light (400-499 nm), green light (500-599 nm), red light (600-699 nm), far red light (700 -799 nm) and near-infrared (800-900nm) radiation related to the photon flux density of each band. This data is collected from measurements taken at a distance of 2 feet directly below the center of the lamp. If the LED beads of the lamps are uneven, the difference in the measured position results in different results.

Spectral Intensity
The sensitivity of plants to different wavelengths light is significantly different from that of the human eye. The absorption of light by plants is accomplished by a variety of photosynthetic pigments, and a variety of photoreceptor cells promote plant morphological
changes. Therefore, the spectral details of plant growth lamps are very important. The light output depends on the electrical power, and the standardized photon flux density is used to facilitate the comparison between low-wattage lamps and high-wattage lamps.
We recommend that the light intensity data be measured and reported at a wavelength interval of no more than 3nm. 

Comparison diagram of the human eye sensitivity curve and the instantaneous photosynthetic efficiency curve generated by the radiation reaching the plant leaves. The photosynthetic efficiency curve is obtained by short-term measurement of a single leaf, so
it is not suitable for low light and as a definite standard for photosynthesis of the whole plant. There are historical reasons why light in the 400~700nm band is defined as photosynthetically active radiation.


Light Distripution  
For most commercial plant users, plant lights are designed to provide a uniform photon flux density in the planting area. Lamps are usually installed at a fixed height above the crop. Therefore, understanding the light distribution is very important for evaluating uniformity.

The light output of all lamps is affected by the operating temperature.  The potential effect of temperature on the photosynthetically active radiation (PAR) value (400~700 nm) of LED lamps. During the time period, the case temperature increased by 300%, while the PAR value decreased by 5%.

The heat generated by the light source is very important for controlled environment applications. When needed to warm, the heat may be beneficial; when cooling, it is a burden. The PAR conversion efficiency can indirectly reflect the heat generated by the lamp. The PAR conversion efficiency calculation method is: the full band radiation energy output divided by the total power consumption of the lamp. Using the PAR conversion efficiency values, the amount of heat generation can be determined.

CWCE LED Grow Light

The plant light launched by CWCE LIGHTING in 2021 has better heat dissipation, lower temperature and longer life than the common LED plant lights on the market, full spectrum, dimmable, and suitable for all stages of plant growth.
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