LED VS High Pressure Sodium Lamp Part 2 – The comparison!
After comparing set ups and technical performance values of high pressure sodium lights and Cree LEDs we will now cover some essentials and then show the results of our comprehensive tests.
The spectrum of visible light
The key to evaluating the performance of a plant light is measuring its PPFD-value (Photosynthetically Active Photon Flux Density). Photosynthetically active radiation denotes the spectrum of sunlight which is used by photosynthetically active lifeforms for growth and flower formation. This spectrum encompasses wavelengths from about 400nm (high-energy blue light) to 700nm (lowenergy red light).
Lumen is for human – let’s measure PPFD
PPFD-values are specified in micromole per square meter and second. The PPFD-value states how many photosynthetically active photons hit an area of 1 square meter over the course of 1 second. When evaluating a plant light it is important to measure its PPFD-value on several different spots to determine a sound average. This average PPFD-value can be used to determine how effectively a plant light will stimulate plant growth.
Measurement Set Up and comparing them
For our tests we pitted a classic 400 watt high pressure sodium light against a bundle of two 200 watt DIY-M-KITs. Both DIY-M-KITs run four high-performance Cree CXB 3590 Chips each. They were connected by 640mm angles to ensure optimal illumination. During the test all lights were installed 45cm above the measuring surface. Both set ups, the LED chips and the high pressure sodium light, illuminated an area of exactly one square meter.
Visualizing the measured data clearly shows that the COB-LEDs reach significantly higher PPFD values than the high pressure sodium light. While the sodium light reached an average of 618 μmol/m²s, the LED plant lights surpassed this value with 811μmol/m²s under the same conditions.
While both light set ups operate on the same nominal power, the higher effectiveness of the Cree CBX LED chips leads to an overall significantly higher efficiency factor. As a result the LEDs can be dimmed to achieve the same output while using less energy than the high pressure sodium lights. Wether you need lights for plant propagation, overwintering, growing or flower phases – thanks to its high PPFD-value, LED technology is ideal for all aspects of plant lighting.
Missed part 1? No problem, here you go!