About LED Technology

LED lights have been utilized in specialized horticulture since the early nineties. NASA first introduced the idea of using LEDs for plant production in space. LEDs were presented to horticulturists as a promising new technology that could effectively and efficiently replace high intensity discharge (HID) lights. So far LED lights have generally failed to achieve the expectations of growers, often resulting in wispy flower growth instead of the robust density of a healthy, thriving plant expected. This result is not the fault of LED technology, but rather due to poorly designed and manufactured LED lights. A good LED grow light is a combination of light intensity and the correct balance of light spectrum. To understand what makes a good quality LED light product, it is necessary to have a basic understanding of how an LED light works.

An LED (light emitting diod) is essentially a silicon wrapped aluminum chip, which is impregnated with an anode and a cathode.  Electric current is passed through the chip and energy, or electro luminescence, is released.

LED bulbs emit light at a particular wavelength that is specified by a number represented in nanometers (nm). These numbers are found in the photosynthetic active radiation (PAR) zone between 400nm and 700nm (this is the viable light spectrum). LED bulbs are identified by their peak nm intensity although the they may emit light of both higher and lower frequencies – ie: if a LED chip is rated at 660nm, it peaks at that intensity but still covers wavelengths near 640nm and 680nm. LED chips can be used to produce any wavelength of light.

Recent advancements made by LED companies have produced Hi-power LEDs (HPLED) that can be driven at hundreds of milliamps (mA) (vs. tens of mA for other LEDs). Some have been driven at more than one ampere of current, and emit large amounts of light.  The vast majority of LED grow light companies still use relatively old chip technology.  These chips are far less expensive to produce and emit significantly less energy than chips used in high quality grow light panels.

LED Intensity Measurements

Typically the 1000 watt HPS light has 140,000 lumens.  Comparing the number of lumens emitted by an HPS light to the number of lumens emitted by an LED does not make sense.  The lumen is a measure of a light's visible brightness.  The brightest light is emitted in the yellow, green and orange spectrums of light.  This spectrum of light is the least absorbed in the Photosynthetic Active Radiation (PAR) zone.  Therefore the largest portion of those 140,000 lumens from an HID light is wasted energy.  While the lumen measurement of LEDs appears less than a 1000 watt HPS, LEDs actually emit a much brighter light in the plant's usable red and blue spectrum. The light of the LEDs is used more efficiently than the light of the HID light.

Light Spectrum and Absorption

The majority of the market uses the 1000watt HPS light because it is the highest level of intensity available to supply plant's active photosynthetic needs.  However much of that intensity is not used by plants and is thus wasted as electricity and heat.  Below is a chart explaining the spectrum nanometer wavelength needed for plant growth:

200-280nm
UVC ultraviolet range, which is highly toxic and extremely harmful to plants.

280-315nm
Includes harmful UVB ultraviolet light, which causes plant colors to fade.

315-380nm
Range of UVA ultraviolet light that is neither harmful nor beneficial to plant growth.

380-400nm
Start of visible light spectrum.  Process of chlorophyll absorption begins.  UV protected plastics ideally block out any light below this range.

400-520nm
This range includes violet, blue, and green bands.  Peak absorption by chlorophyll occurs, and a strong influence on photosynthesis (promotes vegetative growth.)

520-610nm
This range includes the green, yellow, and orange bands and has less absorption by pigments.

610-720nm
This is the red band.  Large amounts of absorption by chlorophyll occur, and most significant influence on photosynthesis (promotes budding and flowering.)

720-1000nm
There is little absorption by chlorophyll here. Flowering and germination is influenced.  At the high end of the band is infrared, which is heat.

1000+
Totally infrared range.  All energy absorbed at this point is converted to heat

The peak lumen output for a 1000-watt HPS light is between 530-580nm.  While this is an impressive number of lumens, it is ultimately wasted energy.  Using both the PAR values and the relative intensity levels of an HPS in those zones, we can dial in on the ideal ratio of blue, red, deep red and full spectrum light. Blue light is needed for vegetative growth while red light, particularly deep red in the range of 660, is essential for dense plant development.  When you combine the ideal spectrum range with chip intensity, the result is high quality LED grow light!