Beginner's Guide -- Types of Grow Lights
Table of Contents
There are three main types of grow lights: LED grow lights, fluorescent lights, and HID. Although incandescent lamps have been used for plant lighting in the past, they are not the main choice for plant lighting due to their high heat and lack of the spectrum required by plants.
LED grow lights
LED grow light is an artificial light source that uses LED (Light Emitting Diode) as the illuminant, which provides the light needed by plants for photosynthesis. LED is the third generation of plant grow light.
The lifespan of LED is longer than that of ordinary energy-saving lamps, and far exceeds that of ordinary incandescent lamps. While these lamps are more expensive, they are more efficient because they don't require frequent replacement, while also saving on electricity costs. Compared to other grow lights, LED lights emit less heat, thus you don't need expensive and complex cooling systems. Using other lights requires a cooling system because excessive temperatures can damage plant tissue cells.
Full-spectrum LED grow lights can provide the red and blue light that plants need for photosynthesis. Because of the controllability of the spectrum of LED grow lights, you can customize LED diodes to emit the specific wavelengths of light you want.
Features:
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Fluorescent lights
Fluorescent lights are using the principle of low-pressure mercury vapor to release ultraviolet rays after being energized so that the fluorescent powder emits visible light. Therefore, the emission spectrum of fluorescent lights depends on the fluorescent powder material used. The fluorescent lamp is regarded as the second generation of plant grow light.
Features:
- Low cost
- Putting out very little heat
- High energy efficiency
- Fluorescent tube fixtures have that thin profile that’s great for tight spaces
- Fluorescent lamps contain mercury, and if broken, the mercury inside will cause pollution that has adverse health effects.
Compact fluorescent lamp (CFL)
The lamp tube, ballast, and lamp head of this kind of fluorescent lamp are closely integrated (the ballast is placed in the lamp head), and they cannot be disassembled except for destructive blows, so it is called "compact fluorescent lamp "
Straight Fluorescent Tubes
This type of fluorescent lamp is a double-ended tube. Common nominal powers are 4W, 6W, 8W, 12W, 15W, 20W, 30W, 36W, 40W, 65W, 80W, 85W and 125W. Tube diameters are T5, T8, T10, and T12.
HID
High-intensity discharge light is an electric gas discharge lamp that produces light by sending an electrical discharge between two electrodes and passing through a plasma or ionized gas. HID includes metal halide, high-pressure sodium, and ceramic metal halide.
Features:
- Relatively short average lamp life
- High heat output
- Produce brighter light
- HID has a warm-up period
- Potentially hazardous waste (internal mercury)
Metal halide light(MH)
Like other gas discharge lamps, metal halide lamps use a similar mercury vapor, which uses an electric arc to pass through a mixture of gases to produce lighting. Metal halide lights are mainly composed of a transparent glass casing and a high-temperature resistant quartz glass tube. Nitrogen or other inert gas is filled between the shell and the tube, and the quartz tube is filled with inert gas, mercury vapor, and metal halide. If these metal halides are mixed in different proportions, different light colors can be obtained.
High-pressure sodium(HPS)
High-pressure sodium lights are gas-discharge lamps that utilize high-pressure sodium vapor discharge. The construction of high-pressure sodium lamps is similar to that of high-pressure mercury lights. Because sodium has a strong corrosive effect on metals, its discharge tube is made of translucent polycrystalline alumina ceramics, with tungsten wire electrodes installed at both ends, and the discharge tube is evacuated and filled with xenon and sodium amalgam.
Ceramic Metal Halide(CMH)
Ceramic metal halide is a variation of metal halide lamps. CMH uses ceramic arc tubes instead of the fused silica arc tubes of traditional metal halide lamps, which allow for higher arc tube temperatures.
LED vs. Fluorescent vs. HID
Efficiency
Compared with fluorescent lights, LED lights and HID lights are more efficient. LEDs require less energy to achieve light output comparable to MH and HPS bulbs.
Lifespan
LEDs have a long life of up to 50,000 hours, while the lifespan of CFL grow lights is about 8,000 hours, and T5 fluorescent light can last for 10,000 to 20,000 hours. MH typically lasts around 10,000 hours, and HPS around 18,000 hours.
Heat output
Grow lights generate more or less heat when they operate, LEDs produce the least amount of heat and are more efficient. Heat output generally decreases as price and quality increase. Fluorescent lamps generate more heat than LEDs, but less than HIDs. When using HID grow lights in a grow room, ventilation is often required to reduce heat.
Sort from low to high: LED < fluorescent < HID
Cost
Considering the invest cost, the price of fluorescent light is relatively cheap. The unit price of CFL bulbs is about 5 dollars, and the price of T5 and T8 fluorescent lamps is about 100 dollars. The price of HID is generally cheaper than that of LED, but HID's electricity bill will be much more than LED.
The initial cost of these three grow lights is sorted from low to high: fluorescent lights < HID < LED grow lights.
Spectrum
LED grow lights contain a grid of hundreds or even thousands of individual diodes or chips. Each diode produces a specific color. Mixing different chips can produce broad or partial spectra. It's easily customizing the spectrum of LED lights. Full-spectrum LED lights are usually a good choice, which can meet the light requirements of plants during different periods.
Fluorescent lights also provide the full spectrum, but some have lower wavelength peaks. For example, 6000K T8 fluorescent lights will be cooler, blue side. The 3000K fluorescent light will be biased towards the red light.
Metal halide lamps produce a blue spectrum that is ideal for plant growth stages. A subcategory of MH lights, ceramic metal halide grow lights emit a broad spectrum that replicates natural sunlight better than any other type of grow light. High-pressure sodium lamps have a yellow-orange tint, so they are great for both flowering and vegetative plants.