One of our experiments using 2 ea. T12's.
From left to right Basil, 3 Bell Peppers, and strawberry. Basil did great, the Peppers all produced Fruit but where small. Strawberry did terrible
Extended Lighting
Expanded Lighting
Incandescent Bulb
The most familiar light bulb that folks are familiar with is of course the incandescent light bulb; this type of light bulb does not have the intensity or the full spectrum necessary to grow plants.
Fluorescent Lighting
Next in line of familiarity is the fluorescent light bulbs, fluorescent light bulbs come in many thicknesses, length and shapes. Not all fluorescent bulbs are good for growing plants, for that you need a fluorescent bulb that is full spectrum.
Full spectrum bulbs come in three thicknesses T12, T8 and T5 the T stand for Tubular, The number following the T is the diameter of the bulb in eights of an inch. T12 = 1 1/2" inches T8 = 1" T5 = 5/8" If you are thinking about using Fluorescent bulbs do not use T12's as they are being phased out. Many people use T5's. I have used T5's and T12's with decent results especially for low light plants. Full Spectrum Fluorescent bulbs are expensive compared to regular fluorescent, a full spectrum fluorescent bulb will run you around 10 dollars ea. depending on length and T size. These bulbs have an average life span somewhere between 12,000 to 20,000 hours. The energy consumption depends on how many bulbs you have in your fixture and bulb size.
I have seen T5 fixture that use as many as 8 bulbs.
High Intensity Discharge (HID)
There are basically two types of HID lamps, MH (Metal Halide) and HPS (High Pressure Sodium).
MH lamps produce a blue light, great for the vegetative state and HPS produces a reddish light great for flowering. Large Hydroponic farms use both depending on what they are growing and switch the lights accordingly.
HID lights for use in hydroponics are composed of three parts the fixture which usually has a 4" or 6" round exhaust hole to attach an exhaust fan, HID bulb (MH or HPS) and Ballast.
Caution: These Lights should not be used in an enclosed environment without proper ventilation.
These lights have a very good PAR, meaning the light is well spread out for good plant coverage and an average life span between 8 to 12 thousand hours. HID's have a very good PPFD they are however expensive to purchase and operate and produce a great deal of heat and not recommended for enclosed areas without good ventilation.
LED (Light Emitting Diode)
LED lights have a good PPFD at center but poor PAR. LED lights come in Red or blue or both and full spectrum, Many Full spectrum LED lights are switchable to red, blue or both, this feature is a great advantage when growing flowering plants.
Led Lights come in various sizes, shapes and connections.
Purchasing LED lights can be confusing for many because the way that lights are being promoted, For example lights that are being sold as 1000 watt lights usually only draw around 180 watts, that’s because they are promoting them as replacements for HID's of the same wattage.
The reality is that the comparison although close does not truly compare as I will show you.
Some recommend 20 to 50 watts per square foot and this figure is probably correct if you use HID's however LED Lights are different.
There are two basic facts about PAR lighting, (Parabolic Aluminized Reflector) Reflection angle is less than 45 deg. like a beam. LED Lights usually have a small PAR or angle of reflection therefore the outer parts of the PAR or angles have a very low photon density. At the center the density of the light is much greater than the outer portion and is the part usually compared to HID's as u can see in the picture below.
Unfortunately many sellers of LED lights do not give you the PAR, intensity value, as well as the PPFD those that do are usually the better light.
In this picture you can clearly see how light from a PAR source is distributed. The dark red is where the highest concentrations of photons are located and therefore the highest PPFD.
The outer edges have low number of photons and therefore low PPFD when compared to the center.
The more photon density the more chlorophyll activity and the greater the Photosynthesis that produce larger fruit.
The second and the most important is the PPFD (Photosynthetic Photon flux density) the greater the PPFD the better the light. The PPFD is basically the amount of photosynthetic photon density that falls on the plants, in other words the more photons of the correct color of light that produces photosynthesis the better. Unfortunately many of the sellers’ don’t put this very important information on their specs. This is why it is difficult to choose a light. There are several manufacturers that do have these figures in their Specs. I highly recommend looking for this information, sometimes shown in PAR graphs similar to the one above.
