If you are researching alternatives for UVC disinfection for an application, there are two options available: LEDs and lamps. One of the important factors to consider when comparing these options is intensity, which is the amount of light that reaches a surface or area. UVC intensity is usually displayed in microwatts or milliwatts per square centimeter.
For various reasons, it can be difficult to compare UVC LEDs and mercury-based UVC lamps. Lamps provide specifications and data based on similar fluorescent lamps, so you are not often able to find the needed specs on light output in the UVC range, degradation, and other key information. UVC LEDs are individual light sources that must be designed into an application to meet the specific requirements. Unfortunately, this means there is rarely comparable information until you have designed and built a UVC LED module and tested it next to a lamp. We can however make some assumptions on actual lamp output and, with some calculations, get an idea of how the two options compare. When doing this type of comparison, one should consider the estimated power output, application requirements and comprehensive costs.
Estimated Power Output
There are a wide range of mercury lamps on the market. When searching for a UVC lamp, it’s common to see that wattage is the only rating shown for power rating. This can be confusing because the wattage rating for lamps is the input power. After taking away the inefficiency of the lamp ballast and losses due to heat, a lamp’s actual output at 254 nm is 10 to 30 percent of the input rating. The higher percentage typically applies to better quality, larger, high power lamps. For a 10 Watt lamp, a good assumption would be 1 Watt or 1000 mW.
A direct comparison at this point with a 60 mW UVC LED with an actual output at 265 nm is that you need 17 LEDs. But that is not the complete picture because we still need to account for the difference in wavelength output. An advantage of LEDs is that the chemistry in the semiconductor material can be adjusted to get a specific light output, and while the 254 nm output of a lamp is in the disinfection range, it is 265 nm that is at the peak efficiency for most disinfection. For most microbes, 265 nm provides 20 to 30 percent better disinfection. With this information, 14 LEDs provide an equivalent comparison for overall power.
Application requirements provide context that make it clear when and how UVC LEDs can be a better solution than existing lamp systems. A typical 10W lamp is about 8” long, but the tube that emits light is only 5” long. One of the benefits of LEDs is that they can be arranged to cover more specific areas. If the application is surface disinfection of a flat 8x11 inch area, then the directional output of an LED makes better use of UVC power. If compared to the cylindrical output of the lamp in our example, then it is possible that the number of required LEDs could be cut by 60 percent. This brings the number of required LEDs to five. In addition, those five LEDs can be arranged in a pattern to provide an even distribution over the treatment area.
Another factor that has a large impact on calculating a direct comparison is how the dose is applied. Lamps typically require a warm-up time until they reach full output power that needs to be considered when calculating overall doses. The lifetime of a lamp is also greatly impacted by the process of turning the lamp on and off. Some lamps state lifetime limits being impacted by cycling more than four times daily. Lamps are often run continuously, even when treatment is not required. These impact the number of LEDs needed, ability to meet lifetime requirements or the overall intensity requirements when applying a direct comparison.
If only equivalent intensity was the comparison, then it’s likely that UVC LEDs would have already replaced lamps in most disinfection applications. While pricing on UVC LEDs has dropped dramatically over the last few years, it is still important to use the strengths of LED design to build the most efficient systems. When designing a system, the overall product costs should be considered (rather than relying solely on lamp versus LED cost), even if that cost is comparable in some cases. The electronics of an LED can be smaller, simpler, cheaper, and more dependable than the ballast needed to power a lamp. With better control of a UVC LED emission pattern there is not always a need for expensive reflective material to make use of a lamp’s emitted UVC pattern.
UVC LEDs can provide equivalent intensity when compared to lamps. Overall, UVC LEDs are already capable of replacing the majority of small to medium-sized applications, and should be considered for larger applications because UVC LED technology advancement could pace with a current product development life cycle. In applications where any type of pulse operation is used or when a product needs to be compact, UVC LEDs are the best solution. As products get larger and more powerful, an equivalent intensity calculation between lamps and LEDs or better LED design solution requires a deeper understanding of all the variables that upgrading to a new technology requires.
Fortunately, Klaran’s Application Engineers have access to light extraction tools, calculators, and a wealth of experience that can help determine how UVC LEDs could best be integrated into your products. If you'd like to learn more about using UVC LEDs for disinfection in your application, contact us today.