HPS lamps (High Pressure Sodium) have been the confident leaders in the cannabis lighting system market for decades, and other technologies, while they exist, are unlikely to change their position. In this article, we will take a closer look at the differences between the different types of lamps and try to give an opinion on what to expect from them.
So what is HPS, LED (Light Emitting Diode)?
HPS lamps emit light by passing high-voltage pulses of energy through a sealed quartz tube filled with sodium vapor and a few other elements, such as xenon and mercury. When heated, the gas begins to glow. Sodium emits an intense orange, yellowish light. The spectrum can be altered using xenon and mercury, which emit in the blue range of the visible spectrum, making the light whiter.
Light-emitting diode (LED) lamps are semiconductors that allow the passage of electric current almost unhindered in one direction, but offer a very strong resistance in the other direction (through a "pn junction"). On one side of the junction, the material is processed in such a way that it receives extra electrons, on the other side, on the contrary, the material without enough electrons is processed. By applying a voltage, we force the electrons to move through the junction to fill the "gap" on the other side. This results in luminescence, the color of which depends on the material used. Phosphides and nitrides of gallium, aluminum, zinc and silicon are most commonly used here.
Photoelectric efficiency
The efficiency of a lamp can be expressed with a simple formula: the total amount of light energy of the lamp (lumens) divided by its total energy consumption (watts). The minimum power of DNAT is 90 lm / W, although for some brands this figure reaches 150 lm / W and even higher. More and more grow lights are also rated in PAR (Photosynthetically Active Radiation), which is measured in µmol / s (photons per second per 1m2 of plant mass surface).
µmol/s is an increasingly popular metric for grow lights, as it measures the amount of light reaching the plant, rather than what the human eye sees.
The most efficient HPS lamps to date produce about 150 lumens per square meter. So, for example, a GE Lucalox 600W lamp produces 90,000 initial lumens ("initial lumens" means the radiation intensity in the first 100 hours), while the best 600W Lumatek lamp produces 92,000. Although it wasn't done before, HPS are starting to display and PAR indicators for new models. For example, the Lumatek 600W outputs 1030 µmol/s.
For LED grow lights, lm/W is considered less "talking" than PAR. This is because red and blue lamps generally have much lower lm/W, as they produce the most important frequencies for photosynthesis, and the production of "inefficient" light is minimized.
However, newer LED grow lights use multiple frequencies to create a richer, more efficient and fuller spectrum, which is considered beneficial for plant growth, and often includes discrete white LEDs as well as red and violet. These newer panels sometimes indicate efficiency in lm/W. Reputable manufacturers should indicate at least PAR. For example, the 410W full-spectrum panel (Budmaster II 675 GOD) from the British company Budmaster indicates PAR values at different distances from the lamp (the longer the distance, the lower the PAR, because fewer photons will reach the plant surface). At 31cm, the PAR of this lamp is just over 2000 µmol/s.
Spectrum
Although progress has not spared HPS technology, it is believed that these lamps only give a faint appearance of natural sunlight compared to more modern lighting systems. Without the addition of xenon and mercury, sodium itself emits a red-yellow light. However, new "full-spectrum" lamps have emerged that actually have two arcs, that is, they are a hybrid of DNAT and DRI. So, for example, the Hortilux Super Blue HPS/MH combines 600W HPS and 400W DRI to deliver 110,000 initial lumens and simulates a spectrum as close to nature as possible.
Currently, LED plant lights are probably the best in terms of spectrum, as the most advanced models offer up to 11 frequencies, which are essential for plant development. For example, the Pantech GLMX720 720W LED plant light, equivalent to 1000W HPS, offers 11 frequencies - from UV to infrared.
