3 Matters on Choosing LED Grow Lights
Along with the flourish of LED grow light nowadays, there are thousands of products selling in the market, but still, no a benchmark has elaborated on how to check a LED grow light. Many growers are confused and risk-taking when making a purchasing decision, though, for the reason of energy saving, cost-saving in the long run, more and more growers took the initiative in trying LED instead of traditional horticulture lights(like HPS, HID,etc.). Some world leaders of horticulture light brands(like Philips) have done many researches proving that LED horticulture light can bring a higher and better quality of yield than traditional one’s do. However, we can’t get benefits but loss if not finding the correct product out. With focusing on the industry for a few years, we would like to share with growers 3 major concerns on checking the product.
1. LQ(Light Quality), the first point, also the most important one.
Light Quality should be judged by light recipe or spectrum, there are two options we usually meet, one is full spectrum, the other is customized/tailored spectrum.
A. Full spectrum: simulated sunlight spectrum, relatively. 400nm~700nm at large.
Pro: almost all the common plants can grow up under full spectrum light.
Con: including many useless light, waste of energy, low cost performance.
B. Customized/tailored spectrum: designed for specific plants, unique. Range from 280nm~800nm.
Pro: productive; high performance on energy saving and better yield.
Con: higher cost due to more R&D investment;
No matter how the data shows perfectly, the only way to find out the right product is to do a growing test. It’s worth especially for commercial growers. Before doing the test, we can filter poor ones out by evaluating the lights at following concerns.
2. LI(Light Intensity)
The way to check a light’s LI includes two factors, light quantity(PPF) and distribution(PPFD).
A. What is PPF?
PPF is photosynthetic photon flux. PPF measures the total amount of PAR that is produced by a lighting system each second.The unit used to express PPF is micromoles per second (μmol/s). It is important to note that PPF does not tell you how much of the measured light actually lands on the plants, but is an important metric if you want to calculate how efficient a lighting system is at creating PAR(photosynthetic active radiation, the wavelengths of light within the visible range of 400 to 700 nm) .
B. What is PPFD?
PPFD is photosynthetic photon flux density. PPFD measures the amount of PAR that actually arrives at the plant. It is measured in micromoles per square meter per second (μmol/m2/s). If you want to find out the true light intensity of a lamp over a designated growing area (e.g. 4’ x 4’), it is important that the average of several PPFD measurements at a defined height are taken. To define whether a light has good or poor light intensity, we should take these two factors at the same time, see the example (Figure 1).
3.Light / Photon Efficacy
Power transfers to energy and heat. What percentage of the power the light can turn to energy defines its efficacy high or not.
So, what does light efficacy define?
Light efficacy refers to how efficient a horticulture lighting system is at converting electrical energy into photons of PAR. As a reminder, the unit for PPF is μmol/s, and the unit to measure watts is Joule per second (J/s), therefore, the seconds in the numerator and denominator cancel out, and the unit becomes µmol/J. The higher this number is, the more efficient a lighting system is at converting electrical energy into photons of PAR. But do NOT get misguided that the higher photon efficacy the light has the better the light is. It is just tell us that the light with high efficacy comes with high efficiency chips or enough chips. According to optics research, blue light has the highest efficacy than another color of lights, then red light, white light followed as the third. So, if a horticulture lighting system comes with lots of blue and red light, of course, that light should have a high performance on efficacy.
A good product should be with the right light recipe to your plant first, then a high light efficacy, if not, even the light efficacy reaches over than 3.0mol/J, you plant might only be able to get 30% energy of that. (Figure 3)
Besides those 3 major concerns above, there are other a few points we need to take them into consideration, such as Cooling system, Life span, Function, and User-friendly.