featur
understanding different grow lights
HID
“ HIGH-INTENSITY
discharge lights offer the
brightest light of any lights
discussed in this article,
so they offer the added
benefit of allowing crops
to be easily inspected.”
48
feature
High-intensity discharge lights (HID), also known as gas or discharge lights,
are commonly manufactured as metal halide (MH) or sodium vapor lights
(HPS lights are also HID lights, but they are excluded here since they were
discussed above). These work by passing electricity through a gas-filled
tube. High-intensity discharge lights offer the brightest light of any lights
discussed in this article, so they offer the added benefit of allowing crops to
be easily inspected. They were used by growers for many years since they are
about 10 times more efficient than traditional incandescent lights, which are
inefficient, burn hot, and offer little in the way of blue light.
High-intensity discharge lights, while more efficient than incandescent
lights, still emit a lot of heat. Among the HID light choices, HPS lights are
roughly equivalent in terms of energy efficiency compared to MH bulbs, but
they are more efficient in their photosynthetic value. Metal halide bulbs
offer better light on the blue side of the spectrum than HPS do. High-intensity
discharge lights also require large, bulky, and often costly fixtures to operate
them, though the bulbs themselves are relatively inexpensive. They are not
typically the grow light of choice for most hobbyist growers or growers who
operate in relatively small growrooms. The technology, however, is old by
today’s standards and most current research is being directed towards light
emitting diodes (LEDs) and sulfur plasma technologies.