The use of ultraviolet (UV-C) light for disinfection has been a well-established practice for many years. In recent years, the development of UV-C LED technology has provided a promising alternative to traditional low pressure mercury lamps. One of the most anticipated parameters of UV-C LED technology is the external quantum or wall plug efficiency. This paper reviews the recent progress and prospects of UV-C LED development, focusing on wall plug efficiency and lifetime at different wavelengths which are suitable for germicidal applications. The robustness of UV-C LED packages is also improving significantly and even tests according to the automotive AEC Q102 specification have been passed successfully. Beyond the pure LED parameters there are further factors and features that affect the system efficiency of UV-C LED based disinfection devices. Examples are demonstrating the big differences in system efficiency between conventional lamp and LED based systems. The big steps in development of UV-C LED during the last years justifies an optimistic outlook to target a replacement of conventional low pressure mercury lamps in the coming years.
UV-C radiation for disinfection applications is used for decades. The major light source in most of these applications is the mercury containing UV-C low-pressure discharge lamp. Compared to this mature technology the UV-C LED is still new and in the introduction phase. LEDs enable new applications which cannot or have not been addressed by conventional lamps before. The radiant power, efficiency and price performance of today’s UV-C LEDs show a significant gap to the conventional lamp and a direct replacement of the current technology seems to be very challenging. In this paper we are trying to estimate the point of time by when UV-C LEDs are able to replace conventional UV-C lamps in different applications by performing a total cost of ownership calculation of the UV-C source at several time points in the future based on roadmaps for different performance parameters and considerations of the respective application efficiencies. A comparison of the applications upper air treatment, secondary air treatment, batten fixture surface treatment and municipal water treatment shows that in some applications a lamp replacement by LED is already realistic today. The significant difference of the application efficiency between LED and lamp-based systems lead to an earlier possible adoption of the LED technology than expected from a direct comparison of the performance parameters of the sources itself.
Light engines used in projection systems often set constraints on the design and system
application of the LED light source. In these advanced optical systems the optical extend of
the LED light source is limited due the etendue of the imager. The etendue is defined as the
product of emitting area and viewing angle. This paper shows how the LED light source is
constrained by the laws of optics and how these limits influence the light source design. To
achieve an efficient system design, the variables that must be optimized include the primary
optics, LED package design and chip technology. The LED light sources which are best
suited for these applications and requirements will also be demonstrated and discussed.
The use of LEDs in advanced optical systems such as LED projectors or automotive
headlamps is usually limited by the optical extend of the light source. The optical extend (or
étendue) is defined as the product of the optical area and the divergence angle of the emission.
In our paper, we discuss the consequences of such limitations on the design and performance
of optical systems. The system optimization involves the chip technology, package design and
the primary optics, producing an optical extend that has to match with the optical extend of the
imager component. It will be shown how these optical laws put constraints on the LED light
source and the design of suitable light engines. The benefits of LED light sources for the above
mentioned applications will also be demonstrated.
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