To figure out how grow lights compare, you're likely to have come across the terms PPE and PPFD.
Because of this, you might not know what these metrics mean and how to make sense of them so that you can make an informed purchase. To understand PPF and PPFD better, read this article.
PPE
Photon efficiency from photosynthetic processes is referred to as PPE. PPE is a way to figure out how much PAR a lighting system makes every second. This measurement is done with a special tool called an integrating sphere that captures and measures almost all of the photons emitted by a lighting system. mol/s is the unit used to show how many micromoles per second PPF is. A horticulture lighting system is probably the second most important thing to measure, but for some reason, most lighting companies don't list this metric.
PPFD
Photosynthetic photon flux density is the number of photons that pass through a plant in a given amount of time. Plants get the amount of light that they need to grow, or as a scientist would say, "the number of photosynthetically active photons that fall on a given surface every second." PPFD measures this amount of light. If you want to know how much light your plants are getting, you can measure how many micromoles per square metre per second (mol/m2/s) your plants are getting.
To figure out how much light a lamp gives off over a certain area (like 4' x 4'), you need to take the average of several PPFD measurements at a certain height. A lighting company that only shows the PPFD at the center point of a coverage area is grossly overestimating how much light a fixture is giving off. It isn't very important to know how bright the lights are in the middle because they tend to get darker as you move away from where they're pointed.
Use of PPFD and PPE at different times.
PPFD should always come with a distance and a place. Most manufacturers will share their PPFD data with you. Few things to think about before you buy:
- The distance between the light source and the observer.
- Geographical location and whether or not it is averaged over a specified area.
- Without this information, you can't compare PPFD in a meaningful way.
- Multiple lamps can make a single area look brighter.
The Key metrics for measuring LED horticultural lighting systems
Remember that photosynthetically active radiation, also known as PAR, light is the wavelengths of light that plants use in photosynthesis. These are the wavelengths of light from 400 to 700 nanometers (nm). This spectral range is close to the range of light that the human eye can see. Photons with shorter wavelengths tend to be so powerful that they can damage cells and tissues, but the ozone layer mostly blocks them in the stratosphere, where they are mostly blocked. Longer wavelengths of light do not have enough energy to allow photosynthesis to happen.
PAR is not a measurement but the type of light that plants need to grow. To compare LED lights, the three most important things to look at are PPFD (photosynthetic pfd), PPF (photosynthetic photon flux), and PPF Efficacy (photosynthetic photon flux efficacy). PPF is a way to determine how much PAR is emitted from a lighting fixture every second. It is measured in micromoles per second (mol/s).
Light intensity, or PPFD, is a measurement of the amount of PAR that reaches a specific spot on your plant canopy. It's measured in micromoles per square metre per second, which is how much PAR reaches that spot.
Light intensity, or PPFD, can make plants grow faster. What is the best way to figure out how evenly the light spreads across a certain area? The rule of thumb for horticulturalists is that getting more light means getting more yield for most crops. Hemp plants usually follow this simple rule of thumb. However, there is a point where the rate at which they grow slows down.
Grow with Horticultural SSL in LEDs Magazine.
It doesn't tell you very much if you only take one PPFD measurement. Some LED manufacturers say they can get a very high PAR measurement right under the fixture by grouping the LEDs and using a narrow beam angle. When you think about a light's PPFD (or light intensity), you also need to consider how much light it spreads. You can think of it this way: The higher you hang a light over your plant's leaves, the less PPFD the leaves get. The same thing happens if you put a flashlight on a counter and raise it. The beam grows in size but gets darker. Your grow light will follow the same law of physics.
Most LED lighting systems to place the LEDs in a small fixture area. This means that these systems naturally produce very high PPFD levels next to the fixture but lower levels a short distance away. To figure out how much light your lighting system is giving your plants, you need to look at the PPFD levels in your grow room. For example, if you have a 50' x 40' grow room, you need to figure out how much light your lighting system is giving this area. Light uniformity across the growing area is very important. It can vary a lot, so be wary of LED manufacturers who don't show full PAR maps to show that their lights can deliver both high and uniform PPFD values across the entire canopy.
Doing this will make your plants less stressed, have a more even canopy, and make more money in the long run. You can do this by using 120° beam angles. If you have a lot of space, multiple lights with this beam angle will overlap and make your canopy look brighter. For small, enclosed grow areas, we suggest using reflective material on the walls to keep your light in and keep it from going out while giving your plants more even light.
What's a better way to measure?
Growers use a PAR metre to measure the average PPFD. They then multiply the average PPFD value by the area they measure to get the PPF value. After that, the PPE value is found by dividing the PPF value by the amount of power used.
It starts with the PPE value. It's hard to get the value right because of things like diffuse reflections and overlaps, so it can only be done in an integrating sphere to get it right. As a result, the PPE that is found this way is wrong.
PPE only looks at how an LED grow light converts electricity into light. That means that PPE can't tell you how well the light fixture spreads out to a canopy. You don't get a measurement of how much light is spread out over a certain amount of canopy space with PPFD. Instead, it tells you how much light is coming into your canopy area per second. This is what growers care about the most because it shows how the real energy from the sun goes to the plants.
People who grow plants with LED lights should look at their lights' PPFD value because it's more accurate to figure out how well they work. It's also a good idea to look at the PPFD maps of any LEDs that you want to buy. Be careful not to be fooled by only having a high PPE score.
Conclusion
It's easy to measure how much light falls on a surface because PPFD is how much light falls on the surface. Even small, handheld light meters or spectrometers can measure how much PAR falls on a surface. These are usually cheaper and can even be used with phones.
A PPF measures how much PAR a single light source emits in all directions. So, a little more advanced equipment is needed. Usually, a goniosphere or integrating sphere is needed to do this. These devices capture all the light from all directions and then figure out how much total light there is. You need to know the PPE, PPFD, and photon efficiency to buy the right horticulture lighting system for your needs and your business. This isn't the only reason not to use these three metrics as the only things to consider when making a purchase. There are also many other things to think about, like the form factor and the coefficient of utilization (CU), that need to be taken into account.
It's important to think about all of the factors together when you choose the best lighting systems for your plants and your business. PPF, PPFD, and photon efficiency are the three metrics that scientists and the best lighting companies use. It's not right for a company to be selling lighting systems for horticulture if they don't give you the right metrics for measuring how effective their system is. You can't use these metrics to see how effective their system is.