In previous post we briefly explain some of the basic grow lighting terms. In order to make things even clearer when growers are choosing their lighting partner we would like to create a series of blogs to debunk some common misleading claims from vendors.
Since it is one of the important features when choosing a light fixture, numerous manufacturers are trying to gain some points by boosting their data.
- Manufacturers claim LED diode performance instead of system efficiency performance. The LED fixture, which is usually comprised of heatsink, PCB board, optics and driver. Each of these components can further decrease the efficiency of the LED diode.
LED diodes - Each type of LED diode is being tested for efficiency as a standalone unit diode before it is brought to the market. Those test reports are freely available on the LED diode spec sheet. There are different brands, power, colours and sizes of LED diodes, each with different efficiency. Besides, even same type of LEDs might have some differences, even if they are coming from the same production badge. Those with similar properties are grouped in bins, so customer can choose which mix of bins he wants. When LED fixture manufacturer receives the desired LED diodes, he is assembling the whole system.
Driver - The driver, also known as the ballast, is critical part of each LED fixture. The driver is necessary because the LED boards are running on DC power, while the grid is AC. The driver converts AC to DC and powers the LED boards. However, this conversion is not 100% efficient. Some of the most efficient drivers on the market can reach 95% efficiency, which means 5% decrease efficiency of the initial starting point.
Heatsink - The heatsink is important for the long lifespan of the LED fixture. Even though LEDs are much more efficient in converting electricity to light compared to its predecessors, they still generate heat. If that heat is not dissipated by a good heatsink design, the whole system lifespan is reduced, and the initial LED efficiency is further decreased. Based on the heatsink design the loss can be 4-8%
Optics - in order to protect the LED boards from the humid growing environment or manipulate the beam angle most companies are using some kind of optics to cover the PCB boards. Depending on the optics material, density and design, this would further decrease the initial diode efficiency with 8-10%
PCB board - The PCB board is the board onto which the LEDs are printed. While the properties of the board itself are important for other reasons, we are going to look into LED arrays or configuration. Each LED diode has a manufacturer's recommended driving current. Since LED grow lighting system usually consist of 2 or more different types of LED diodes, they have to be grouped in series or parallel in order for the system to work at optimized level. By manipulating the driving current and the number of diodes we can achieve higher or lower system efficiencies. Therefore two fixtures using same LED diodes, but different quantity will have different output.
- Manufacturers claim system efficiency but fail to present proof. Usually LED fixtures are tested in sphere meters which generate specific test reports that show the information we seek.
Picture:Integrated Sphere Meter
Below are common tricks
Another fixture testing report is being presented
Try comparing all the parameters you have in the provided specification sheet of the fixture to the test - spectrum curve, power consumption, voltage, PPE/PPF, if efficiency is not automatically calculated on the report, find the total PPF and divide it into the power consumption. Pay attention that no 2 fixtures are identical and there is usual tolerance of +- 5%.
LED diode testing report is being presented
Compare spectrum curve and power consumption. Usually, the testing reports of LED diodes are with very low power consumption of 1 to 5 watts.
No testing report is being presented or
Testing reports are being presented but in lumens values
Request testing report in mmol/s values. Professional lighting manufacturer posses a sphere meter and the test usually takes 15 minutes.
Manipulated testing reports are being presented
Those are the hardest gimmicks to catch. Try comparing all data from the specification sheet and the test report being presented. If you are still doubting the test report, purchase a sample and test it in third party lab. In general labs that are testing for UL, CE, TUV should be able to help.
Below is a sample of our gen2 vertical farming light test report for reference:
Common sense topic:
If the fixture is using predominantly white LED diodes (those are usually branded as broad-spectrum lights), technically it is very hard to achieve system efficiency above 3.0 mmol/w.
System efficiency above 3.0 (premium vendors are marketing up to 3.5 mmol/w) are all narrow spectrum with predominantly red LED diodes. Those fixtures are useful for greenhouse operations due to the mixture with natural lights, but are not suitable for indoor operations where the Sun is not present.
The most efficient diode on the market is Red 660nm with efficiency 4.3 mmol/w. The most efficient white LED didoe is around 3.2 mmol/w.
For more information please get in touch with: firstname.lastname@example.org