LED in general lighting ? Not quite yet

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LED in general lighting – an update

 

Biswajit Sengupta

Despite rapid developments in LEDs as an efficient source of light, they have not been able to capture even 5% of the market share in general lighting applications, which are still dominated by conventional light sources. It is true that apart from high-power LED chips, there has been great progress in enhancing the reliability of drivers and heat sinks. At least the chip manufacturers can safely claim that their products are not going to betray the useful life they declare. LEDs do have some unique properties that no other light source can ever have. They are highly efficient, converting almost the entire electrical energy input into light energy and requiring very little power to operate (a green energy ), as it is seen in India, where almost 18% of the power generated is consumed by artificial lighting (the rest of the world, particularly the developed nations, may be even higher). Smaller solar panels can be used to provide power to these lights and thus bring light to rural areas and remote corners on our planet where civilisation has not seen electricity: a tiny source helping in the design of compact luminaires, lighter in weight and easier to handle; very long life, even in comparison to the longevity of a long-life H.I.D. source developed to date. Then what prevents it from entering the general lighting application? One of the main reasons is the optical control of the light emitted by the LED. Unlike the conventional light sources, which emit highly incoherent light, LEDs emit coherent characteristics, and their spectral coherence varies widely over the wavelengths emitted. To add to the woe, an LED produces a highly directional light, which calls for predetermined beam angles to be set by integrating optics with the bare LED chip. That means that for each and every application in general lighting, there is a need for engineered photometric control. This is because output requirements vary by application and are particularly exacting for streetlights. Various optical classes have been designed and developed to achieve the desired emission profile for a particular application. These include refractive (continuous surfaces and microstructured), reflective (continuous and facetted), and diffractive optics. The reflector type used mostly with LED is the Compound Parabolic Concentrator (CPC). A CPC can maximally redirect light output from an input plane. Proper material selection for the microstructured optic is necessary, depending on the extreme environmental conditions that an LED must operate under for general lighting applications. Although typical materials are PMMA or polycarbonate, high-temperature applications call for Zeonor, Topas and Arton. A luminaire for every application has to be designed around the available LED or module, unlike its conventional counterpart, where the shape and size of the source are standardised for each rating and available off-the-shelf for replacement and maintenance. LED still has a long way to go before it reaches this stage. But the amount of research work going on around the world at a frantic pace will definitely see LEDs as a preferred light source in a couple of years. Progress in this direction keeps pouring in almost daily. It is worth mentioning a showcase project on the installation of energy-efficient apron lighting systems at Munich Airport. Out of seven high masts, two masts were converted to high-performance LED floodlights with Cree Lamp of 4500K. Each mast has six floodlights, and the retrofit energy savings for all seven masts is about 54%. The image of the Munich Airport apron below shows the uniformity achieved with white LED luminaires. The yellow light at the far end is from conventional HPS. This image demonstrates that LED technology is progressing towards becoming the primary light source for general lighting applications.

LED FLOODLIGHTS are being tried out at Munich Airport. At the far end, the yellow light reflected from the aircraft is from existing HPS lighting. An encouraging view of LED in general lighting.

2026 Perspective

• Year 2012: At the time of writing this post, the market size captured by LEDs was around 5%. The extensive and frantic pace of research has finally led to the current era of smart, connected lighting. As of today (2026), LED has globally taken over almost the entire market from traditional light sources.
• While this was a showcase project in 2012, LED floodlighting is now the global aviation standard, offering even higher uniformity than the 54% savings initially recorded.

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