Date:31 January 2009 Tags:, ,

Audi LED Tech

High performance is what characterises Audi’s striking R8 sports car: already regarded as pretty potent, it’s just been given a course of automotive steroids, upping power to 390 kW via a 5,2-litre 10-cylinder engine. It’s also been launched in customer race form for gentleman racers or one-make series.

But there’s another aspect to the R8 that isn’t readily apparent – not much in daylight, at any rate: this street rocket is a rolling testbed for the German manufacturer’s LED lighting programme. All-LED headlights are available as an option on the R8 – the world’s first. Everything from daytime running lights to turn indicators and low beam as well as high-beam headlights is all LEDs.

According to Audi, Today’s xenon and LED headlights are four times more energy- effi cient than conventional halogen headlights. And by 2018, LED technology should be about eight times more effi cient than halogen light.

Besides efficiency, LEDs have another huge advantage: their service life is practically indefi nite and they react up to ten times quicker than traditional incandescent bulbs. The introduction of LED fog lights on Audi’s Pikes Peak quattro concept at the Detroit show five years ago represented a world first. Soon after, the Audi A8 became the first vehicle with LED daytime running lights.

The tiny light sources present designers with spectacular opportunities, says Stefan Sielaff, Audi’s Head of Design. For example, a number of light-emitting diodes can be combined to create various shapes.

There’s a psychological phenomenon to this, too: bright light created by small, compact light sources is unpleasant for the human eye, says Audi. The combination of headlights and LED daytime running lights enlarges the light source.

The LED’s lower energy cost has a spin-off benefi t: it can also cut fuel consumption. Daytime running lights become mandatory in the European Union in May 2011, but drivers in several European countries – including Italy, Denmark, Finland, Estonia, and Sweden – are already obliged to use their lights during the day. Estimated energy consumption of low-beam headlights, taillights, and licence-plate illumination is 200 watts – which the alternator must generate. Compare that with the 15 watts required for the new Audi A4’s LED daytime running lights. Audi calculates that this equates to a saving of about 0,2 litre/100 km and about 4 grams fewer CO2 emissions per kilometre. Getting to this point has been a hard road, though.

“We first had to experiment a great deal before we could employ the medium of LED to achieve the lighting performance of headlights,” explains Stephan Berlitz, Head of Lighting Technology and Electronics in Ingolstadt. “One day, a supplier called to tell me that white LEDs with 18 lumens per watt would soon be on the market. Suffice to say, that immediately got my attention.”

(An ordinary household light bulb generates about 20 to 25 lumens per watt and modern xenon headlights create some 80 lumens per watt.)

The next generation of white highperformance LEDs will hit the market next year with a whopping 100 lumens per watt, thus surpassing the efficiency of xenon lights for the first time. This can be traced back to dramatic developments.

“Light-emitting diodes are similar to computer chips. Every two years there’s an increase in output of about 30 per cent,” explains Berlitz, “and we’ll soon be able to create so much light with LEDs that entirely new applications will become possible.”

Because LEDs are so small, they hold unique possibilities for designers to exploit. Bundling them tightly in arrays, and controlling them with sophisticated electronics, it’s possible to create complex lighting functions in restricted space, with no moving parts. That’s been particularly useful in cornering lights, for example: they can be “swivelled” electronically by modulating the light output of sections of an array.

Developed from this is “intelligent” lighting. Already in pre-production are high-beam headlights that will allow drivers to navigate roads at night without temporarily blinding oncoming drivers. It’s done by variable light distribution. Electronics continuously calculate the distance to any approaching vehicles to ensure that the road ahead is ideally illuminated at all times – without irritating oncoming drivers.

There’s plenty of scope for new concepts in interior lighting. This could range from enhancing ergonomics and safety to imparting a certain ambience. The customisable lighting of the Audi A8 allows the interior light to be dimmed, and various lightings to be profiled. You could, for example, set the interior lighting to adapt to whether you’re driving through a well-lit city or charging along a dark unlit rural back road.


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