Grow lighting is nothing new; it’s been employed for a great many years by plant growers to enhance and even supersede light from the sun. What is new however is LED grow lighting, which has sparked some pretty sharp arguments about its effectiveness. This article briefly reviews what these new lights bring to the table and why there is much about them.
There are two main reasons why LEDs started being used for grow lights. First, LEDs are the most efficient form of lighting available. They convert most of the energy they consume into light and thus give off very little heat. By comparison, traditional HID (high intensity discharge) grow lights produce considerably more heat than light.
Second, unlike regular incandescent type lights which spread light across a wide band of the spectrum, LEDs can be manufactured to emit light only at defined wavelengths. The advantage being that plants in fact only absorb light from two specific parts of the spectrum. So LED lights don’t waste expensive electricity by generating unwanted heat and unusable light.
These combined attributes – low electricity consumption plus accurate targeting of key parts of the spectrum – account for the great interest in LED lights. The promise of improved light delivery and reduced operating costs was bound to attract attention.
Growers were also not slow to spot that because LED lights run cool it is possible to position them much nearer to the plants without causing damage to foliage. This is turn also exploits the way the inverse square law applies to light, in that every time the distance is reduced by half, the amount of light delivered increases fourfold.
Among other advantages is the ability to seamlessly vary the blue:red light ratio to suit different phases during plant growth. HID lights rely instead on physically switching between sets of metal halide and high pressure sodium lamps. Then there are the much reduced maintenance requirements, since LEDs can remain in constant use for a decade, while HIDs need regular bulb replacements.
So why the controversy? Fundamentally LED lights perform as claimed and can easily outperform HID based systems in terms of power and plant yields, but also crucially in running cost and maintenance overheads. However there have been many sub-standard products sold as LED grow lights that have gotten the whole field a bad name.
To match for example a 400w HID in terms of useful light requires around 90 watts of LED, with each individual LED being at least 1w or higher. A grow light panel with 225 LEDs that consumes 14 watts (to pick a well known example) has no chance of working since each LED is only contributing 0.06w. Unfortunately, once people start to complain about this junk then everything else gets tarred with the same brush.
If you found this interesting then be sure to check out these additional articles to find out much more about LED grow lights and LED grow light technology in general.