What are LED Lights?
LED lights are just small light bulbs that can fit easily into an electrical circuit but unlike ordinary incandescent bulbs, they don’t have a filament that burns out, and they don’t get very hot. This means they last a lot longer. They can also be configured to emit light at specific wavelengths thereby making them more efficient for growing plants which require light between 400 to 700 nanometers.
Efficient Means of Producing Light
Thanks to new technology LED grow lights have become the most efficient means of producing artificial light for plant growth. This is because LED grow lights have a high photosynthetic photon flux (area) density for every Watt consumed. What does this mean?
Photosynthetically Active Radiation
According to Wikipedia “Photosynthetically active radiation, often abbreviated PAR, designates the spectral range (wave band) of solar radiation from 400 to 700 nanometers(nms) that photosynthetic organisms are able to use in the process of photosynthesis”1
PPFD stands for the photosynthetic photon flux (area) density which is the Photosynthetically active radiation emitted per square meter per second. In other words it is how much energy suitable for plant growth emitted every second for every square meter of plant. The higher the PPFD the higher the crop yield as the light can cover a larger area.
Plants only require light energy within a narrow frequency of between 400 and 700 nanometers(nm’s) and other frequencies can even be harmful to a plant. A frequency to high can damage the cells and a frequency too low wont penetrate the plant.
Because Hydroponic LED grow lights can be manufactured to emit light at narrow wavelengths specifically suited to plant growth they are more efficient and don’t require as many Watts to run than other grow lights.
How to Measure Efficiency
The efficiency of a LED grow light is determined by PPFD / Watt of energy. The PPFD per Watt will determine how efficient a light source is at producing photosynthetic active radiation per Watt.
The efficiency of an LED grow light can be expressed as the number of grams of crop produced per watt. However this will vary depending on the plant and other environmental factors.
Since the Photosynthetically active radiation range occurs within the visible spectrum it is common for the brightness of the light to be measured in lumens or LUX.
If these lights are left on 24 hours a day and use a high wattage they can still run up your energy costs. You want a powerful LED grow light that produces a high plant yield but efficient enough that it consumes a relatively low wattage. The following post entitled “Buying hydroponic LED grow lights” discusses factors you need to consider before making a purchase.
- Photosynthetically active radiation, Wikipedia [↩]
