"LEDs are much cheaper"
April 08.04.2012th, XNUMX - Five questions for Professor Henning Riechert - In contrast to light-emitting diodes, energy-saving lamps have little future, say experts. LEDs, light-emitting diodes, are semiconductor components that emit light as soon as electricity flows through them. In an interview, Professor Henning Riechert, Director of the Paul Drude Institute for Solid State Electronics in Berlin, explains why LEDs will prevail on the market and what consumers should look out for when buying.
Professor Henning Riechert, Director of the Paul Drude Institute for Solid State Electronics in Berlin
biallo.de: Legislators take inefficient incandescent lamps from the market. Bulbs with 60 watts are no longer available. 2012 comes to the end for the remaining clear bulbs. From 2016, there are no more bulbs that reach only the class C or worse on the efficiency scale. Do light-emitting diodes - LEDs for short - have what it takes to succeed in the home, too?
Henning Riechert: For technical reasons, LEDs are ideal for lighting. While the first white-light LEDs gave off a cold, rather uncomfortable light, color characteristics can now be generated that come very close to those of sunlight. In principle, LED chips can also be produced that allow a wide range of color characteristics - depending on the mood or time of day. In addition, thanks to their design, LEDs offer completely different options for installation in lamps and lighting systems. This can already be seen in the skyrocketing number of new, LED-based luminaires. I think there is still a lot more exciting to do here and we will see completely new designs of light sources. Due to the extremely long service life of the LED of an average of 50.000 hours, which corresponds to five years of continuous operation, it also makes sense to use it in places that are difficult to access.
biallo.de: What makes experts so sure that LED and not classic energy-saving lamps for lighting technology of the 21. Century also develop in apartments and houses?
Riechert: Two factors are decisive here, first of all the efficiency of light generation. In this regard, the energy-saving lamps are already largely exhausted. The currently commercially available LED have about the same efficiency. However, laboratory samples of LEDs already have much higher efficiencies, which will certainly come onto the market in the next few years. I therefore expect that LEDs will soon be superior in energy efficiency to energy saving lamps. This means that LEDs will be used at least wherever artificial light has to be switched on for a long time. The second factor is the cost. These are even higher in LED today than in energy-saving lamps, but the industry is working hard to reduce production costs.
biallo.de: LEDs still have a number of disadvantages for consumers. What are the essentials?
Riechert: These are certainly the perceived as unpleasantly cold light quality of many, especially cheaper LED and the resulting poor color fidelity in the illumination. But that is now fixed. And of course, the question of costs remains. However, I expect that LED will be significantly cheaper.
biallo.de: Due to rising prices for so-called rare earth metals as well as for aluminum, however, no cost reduction for light-emitting diodes is predicted in the medium term. What do consumers really need to be prepared for?
Riechert: Rare earth elements are usually not needed for the semiconductor devices. But they are part of some phosphors, which are then small admixtures. Aluminum is enough in the market. However, there are concerns about the availability of the element indium. This is essential for the production of the so-called active zone of the LED. However, only a few atomic layers have to be installed, so that the required total amounts are not limiting. So, all in all, I think warnings about a shortage of needed base materials are exaggerated.
biallo.de: Judging an LED is not easy. For example, in terms of light quality or service life, there is a considerable bandwidth. What should consumers pay attention to?
Riechert: Color characteristics are decisive for use in room lighting. Because it determines how the room is illuminated. So if viewers feel the light, for example, as warm and comfortable. For specification, the so-called color temperature is given in the unit Kelvin - K for short. We find 5000 K cool, 2800 K warm. When it comes to achieving as color-true lighting as possible, then the light source must offer a spectrum of light that corresponds as closely as possible to the sun. This is the case with light bulbs, but this is not necessarily the case for other bulbs. An extreme example is the sodium vapor lamps with their yellow-orange coloring, some of which are used in street lighting. LEDs are therefore specified for color rendering by the so-called color rendering index Ra, which should be 90 or better for sophisticated lighting. The lifetime is also stated by the manufacturers, it should be at least 20.000 hours.
(biallo by Matthias Kutzscher)
