What I do not like about this KIND LED Flower Bar Light is the wavelengths of the LEDs used. Green an Amber LEDs are by their wavelength the least efficient LEDs made.
What is most important is the number of photons that reach the plant's leaves for the least amount of electricity. Whether the photons come from PCB boards of LEDs or DIY CoBs, it does not matter. For the DIY guy CoBs are often the way to go becasue it beats the cost of manufacturing a small quantity of PBCs.
Spectrum is important and HPS has proven to be very effective for growing cannabis. It seems you are looking for an energy efficient HPS replacement. The HPS spectrum has been proven to be duplicated with white 4000K 70CRI LEDs supplemented with deep red. The white LEDs provide enough blue spectrum. Very few white LEDs provide deep red spectra.
To replace a 1000W HPS with LEDs, according to one well documented source, it took 144 white Cree XP-G3 4000K P/N XPGDWT-01-0000-00LE5 and 48 Cree XP-E Photo Red 660nm P/N XPEPHR-L1-0000-00901 . This required 553 Watts of electricity and to be hung at a height of 59" compared with a Gavita Pro HPS 1000W hung at 39".
Do not take the to mean a grow fixture drawing 550 watts is going to replace an HPS. Watts should not be considered in any aspect of grow lighting. Photosynthetic Active Radiation (PAR) measured in PPFD per Joule is the only meaningful parameter associated with watts.
Sometimes the term PAR watts is used. Sometimes lumens per watts is used. Neither optical watts or lumens are units of measure applicable to photosynthetic actions. To understand this you need to understand measurements of light is expressed in units in the domains of Luminous (lux,cd), Radiometric (watts), and Quantum (moles). There is a conversion from watts to PAR moles which requires the milli-watt value at each PAR wavelength (400-700 nm), and the method of measurement used. Much easier if the manufacturer specifies the PPFD, the height at which it was measured, and the uniformity. Such data would look similar to this:
This term PAR Watts skews the data. Radiometric watts is the measure of the energy contained within the photons. When it comes to photosynthesis plants are only interested in the number (quanta) of photons. Watts being radiometric and photons being quantum, PAR watts would need to be converted to quantum moles to be meaningful. Lumens per watt is possibly only somewhat relevant when comparing LEDs with the same CCT (e.g.4000K) and CRI (e.g. 70). You need the number of photons per second, at a fixed height, and within a fixed area (e.g. m²) for a valid comparison. The only way to get these values is for them to be measured.
In my opinion the uniformity is very important. A smaller fixture is going to have poorer uniformity than one where the LEDs are spread apart. My preference is for a light bars or strips of LEDs for improved uniformity. The benefit of uniformity comes in the significant gains associated with a decreased height and the inverse square law. Height is limited by the hottest spot in the PPFD plot.
The KIND LED Flower Light Bar you linked to is a good format, except the LEDs used are less than optimal. If you could get a few of those light bars with white and deep red with decent thermal management and a reasonable price, that would not be a bad way to go. The green and amber are a very poor choices when selecting an LED for a grow fixture.
Almost all LEDs are either GaN (blue, green) or AlGaP (yellow-red). The specific optimal wavelength for these type of LEDs are usually 450nm and 660nm, respectively. . As the band gap gets wider, the width of the LED band gap changes the wavelength. As the wavelength (band gap width) gets further away from the optimal, the efficiency decreases. The leaves green and amber at the inefficient ends of the spectrum.
White LEDs are florescent, with a deep blue LED pumping a yellow phosphor. The quantum yield of the phosphor is the ratio between the photons absorbed over the photons emitted. This makes white LEDs less efficient than blue or red LEDs. Amber LED made from AlGaP are very close to being as efficient as a phosphor pumped amber. So getting amber from a warm white LED has equal efficiency.
There is more to grow light spectrum than just photosynthesis once the photons are converted to electrons and enter the electron transport chain the wavelength can alter which secondary metabolites are produced with the electrons.
.
