In the realm of water disinfection, UVC LEDs have emerged as a promising solution for effectively eliminating harmful pathogens. In fact, we recently announced that Amway selected Crystal IS’s Klaran UVC LEDs to treat and disinfect water in its new eSpring™ Water Treatment System.
However, even as adoption of UVC LED technology increases, mercury lamps continue to dominate the industry. One of the reasons for that has to do with the wall plug efficiency (WPE) of UVC LEDs compared to legacy disinfection technology. WPE is the ability of a device to convert energy into light, and some industry stakeholders have suggested that UVC LED adoption in germicidal UV (GUV) applications will be limited until the devices can match the performance of existing commercial mercury lamps.
You’ve likely already seen debates on the power and lifetime of UVC LEDs compared to mercury lamps – we actually did our own comparison here – but what many are missing in these debates is the fact that these comparisons are not apples to apples. Especially when it comes to WPE.
Yes, it’s true that the WPE of UVC LEDs is still relatively low — between 3% and 10% – with most of the energy applied to the device converting into heat. However, WPE is not the sole measure of progress for this technology, and UVC LEDs offer inherent benefits around design flexibility and on-demand operation, especially for low-flow water disinfection applications that exceed performance requirements.
Improving UVC LED Efficiency
Even though current WPE within most commercially available UVC LEDs is in the range of 3% to 6% depending on the product, overall efficiency – both internal and external – can be improved at multiple points within a device. Internal efficiencies can be improved by reducing defects and dislocations in the epilayers of the substrate material, and external efficiencies can be improved by redesigning the device for better light extraction.
It’s also worth noting that many UVC LED manufacturers grow structures on bulk sapphire, which while a low-cost, transparent substrate, also has internal efficiency limits due to lattice and thermal expansion mismatch with the nitride layers.
Crystal IS, on the other hand, has developed native Aluminum Nitride (AlN) substrate technology for more powerful and reliable semiconductor devices that emit the germicidal UVC wavelengths. These LED devices have higher efficiencies and longer lifetimes in the 260–270 nm wavelength range than diodes fabricated from other technologies, like sapphire.
As a result, manufacturers that use bulk AIN substrates like Crystal IS gain an inherent internal efficiency advantage – more specifically, the internal quantum efficiency (IQE), which is the percentage of electron-hole recombination that results in a photon as opposed to the heat that is generated when an electron encounters a dislocation defect. Devices grown on AlN have demonstrated more than double the IQE at UVC wavelengths compared to those grown on sapphire substrates, and therefore, improve WPE through improved internal and extraction efficiency.
Growth in UVC LED Adoption
One area where we’ve seen UVC LED technology adoption increase is in point-of-use (POU) water systems that operate at flow rates of up to 5 gallons per minute. Point-of-entry (POE) systems, on the other hand, typically handle flow rates ranging from 5 to 50 gallons per minute (gpm), and we’re witnessing a rise in the use of UVC LEDs in these lower-flow systems.
Both POU and POE systems typically operate at a low duty cycle, whereas higher-flow systems like industrial, wastewater, and municipal treatment systems will have more continuous operation. We bring this up because WPE and duty cycle are closely linked. Therefore, the low duty cycle in POU and POE means that a WPE between 3% and 6% is more than sufficient.
Finally, it’s important to note that when it comes to UVC LED-based product development, most OEMs don’t just swap out light sources from lamps to LEDs. Instead, they often redesign applications to fully capitalize on the benefits of LEDs, such as their smaller size, instant on/off capabilities, and wavelength precision. Plus, the reason OEMs turn to UVC LEDs in the first place is not often initially due to WPE, but instead, the promise of sufficient disinfection. Then, as they design their disinfection products, they can optimize system performance to reduce the significance of the WPE parameter in terms of energy consumption.
We actually have guidance on how to integrate UVC LEDs into your water product design, which you can access here, that will ensure you’re able to take advantage of the full benefit UVC LEDs offer.