Let There Be Light

LEDs in architecture. The "Seven Screens" obelisk in front of Osram HQ in Munich (top), lighting for an event at the Stone Bridge in Regensburg (mid) and cobblestones in Geneva (bottom)

A truly staggering array of lights more fabulous than anything ever dreamed up in a fairy tale will light up the big cities of the future," predicted art historian and architecture critic Walter Riezler back in 1928. The long and successful history of the light bulb had only just begun at that time. In fact, Osram, with its famous light bulb logo, had been established just nine years earlier, on July 1, 1919. The company’s portfolio eventually included fluorescent lights and halogen and high-pressure discharge lamps.

Still, the "truly staggering array" of lights that will illuminate the magacities is yet to come, says Wolfgang Lex, head of the LED division at Osram Opto Semiconductors (Osram OS). According to Lex, light-emitting diodes (LEDs) and luminescent plastics (organic light-emitting diodes—OLEDs) will once again fundamentally alter lighting as we know it. "However, instead of a revolution, we’ll be witnessing a slow evolution," he says.

For years, nobody paid much attention to LEDs. In fact, it took around 30 years for LEDs to evolve from the red operation mode displays of the 1970s to the white diodes of recent times. Now, however, the mini-lights are set to become the stars of lighting technology. LEDs can stand up to light bulbs, fluorescent tubes, and halogen and xenon lights in every respect. They are extremely long lasting and efficient, take up very little space, emit low levels of heat and can be installed in a very flexible manner.

The efficiency of LEDs, such as the Ostar unit from Osram, now stands at 75 lm/W. By comparison, an incandescent bulb achieves only 12 lm/W and energy-saving lamps manage 50 to 60 lm/W. Moreover, the price of an LED—once the biggest argument against the diodes—will fall dramatically when the units are mass produced. LEDs also recoup their investment quickly, because an LED has a lifespan of 50,000 hours, which is around 50 times longer than that of an incandescent bulb. So, if you bought LEDs that produced the same amount of light as a 60-W incandescent bulb, you’d pay about 60 euros (compared to 40 € for 50 conventional bulbs). But, thanks to the LEDs’ higher efficiency and lifetime, you’d save about 430 € over 50,000 hours.

Designers and engineers are constantly coming up with new applications for LEDs. "The clear trends today are to cut costs and conserve resources," says Ulrich Kastner-Jung, head of Strategic Marketing at Osram OS. "LEDs can also help an aging population feel safer by illuminating sidewalks, subway stations and emergency exits. What’s more, LEDs not only light things up but can also communicate information as displays on interactive walls."

The future has already begun on the road. Originally installed as rear-window brake lights, red LEDs are now being used in more and more cars for the rear brake lights themselves. One reason for this development is LEDs’ ability to light up 150 ms more rapidly than bulbs, which could mean the difference between life and death for a driver behind an abruptly braking vehicle. And inevitably LEDs will eventually be used in headlights as well. In 2005, for example, the Hella company demonstrated a bending light that uses LEDs that turn during curves. Meanwhile, in a pilot project, Osram has installed LEDs as daytime running lights in the new Audi R8’s headlights. Thanks to the economical tiny diodes, daytime running lights can be used with virtually no increase fuel consumption. Siemens has also developed LED headlights for the BR 189 European locomotive

We’ll also be seeing more LEDs on streets, now that local authorities are increasingly installing them in traffic lights. San José, California, is a pioneer in this regard. California’s third-largest city has equipped around 900 traffic lights with LEDs. As a result, annual associated costs have been slashed by nearly $1.7 million to $160,000. Budapest has commissioned Siemens to replace light bulbs in all of its 33,000 traffic lights with LEDs. The financing plan for the project is so smart that the Hungarian capital will not incur any additional costs as a result of the conversion, as the payments required for installation of the new technology are lower than the savings achieved through reduced power consumption and the elimination of maintenance costs.

LED Sidewalks. "It would even be possible to set up an entire traffic guidance system using LEDs, including information displays, illuminated traffic signs and variable lane markings," says Lex. "Initial tests are now under way in the Netherlands to replace white lane markings with LED strips," he says. Pedestrians will also benefit from LED beams placed in cobblestones and illuminated LED strips in sidewalks, both of which could eventually replace streetlights. "One of the big advantages is that you could set it up so that sensors would activate the lights only when someone passes by," says Lex.

LEDs are gradually taking over in architectural designs and artwork for public spaces as well. For example, a fountain that also serves as an interactive image screen has been built in Chicago’s Millennium Park. The glass structure, which is 15 m high, alternately flashes colored backgrounds and photos of Chicago citizens across its cube-shaped surface. Passersby are amazed when water shoots out of the mouth of a giant digital face in the fountain.

New application areas for light-emitting diodes include office lighting systems (top) and lighting units that lend a refined touch to modern kitchens (bottom). A concept car from Opel is also equipped with LEDs

The "Seven Screens" obelisks that Osram built in front of its Munich headquarters are also attracting a lot of attention. The obelisks contain more than 750,000 high-performance LEDs that are controlled by a central computer via fiber optic cables. Each pixel here is capable of depicting 16 million colors. People who look at the first video installation on the Seven Screens say that the shadows of the men and women depicted by this work of art seem to run from obelisk to obelisk.

LEDS are the lighting system of choice for fast-growing cities, as they also allow completely new forms of architecture to be realized. The cities of tomorrow are in fact already on display in Singapore, Shanghai and Mumbai. Whereas Europeans tend to favor white LEDs, skyscrapers in these Asian cities are bathed in the most colorful tones. "Asian cities are pioneers in lighting architecture," says Lex. "Every highrise has its own individual lighting decorations, which are increasingly being implemented with LEDs. A particularly successful example of this trend is the New World Center in Hong Kong, whose colorful light display stretches over 15 floors. The light show was realized using LED strips from Osram. And the Turning Torso in Malmö, Sweden—at 190 meters, Europe’s second tallest residential building—illustrates how LEDs are moving into building interiors. The hallways on every floor in the tower, which is shaped like a strand of DNA, are filled with more than 14,000 white LEDs from Osram. The diodes were chosen because of their longevity and the flexible design of the modules, which were easily accommodated by the curved walls.

Supermarkets are next on the list. In a 2006 pilot project, Osram equipped a Migros supermarket in the Swiss canton of St. Gallen with 16,000 high-performance LEDs. Employees and customers have since reported that they are thrilled by "the invigorating and motivating atmosphere" in the store. The LEDs’ clear light also makes for a better display of merchandise, including fresh produce and meat, as the diodes emit neither infrared nor UV light.

Homeowners are now experimenting with LED modules in kitchens, bathrooms and living rooms. "LEDs can also improve productivity in offices by simulating daylight, thus supporting employees’ biorhythms," says Lex. "During the day you have a type of blue light and toward the evening you move toward red." The tiny spotlights can be installed in furniture, clothing and even in floors. In 2004, for example, Vorwerk Teppiche and Infineon demonstrated a "thinking carpet." Such carpets can be equipped with sensors for alarm and climate control systems—or LEDs that indicate the fastest route to emergency exits in office buildings.

But LEDs aren’t the only game in town. OLEDs—organic light emitting diodes (see LEDs in Pictures of the Future, Fall 2003)—are also likely to have a huge impact. Unlike LEDs, OLEDs light up entire surfaces. They consist of an actively luminescent plastic layer less than 500 nm thick—that’s about a hundredth of the diameter of a human hair. Organic molecules contained in the plastic layer are exposed to an electric current that causes them to light up. OLEDs can already achieve a full range of colors if the right molecules and polymers are used. Developers create white light by stacking red, green, and blue layers on top of one another. OLEDs display good color rendering properties and a high level of true color, and, like LEDs, they are also very efficient.

OLEDs’ principal benefit, however, is that they are thin, flat, transparent and flexible. They can be made in many shapes and sizes and applied to glass panels or flexible foils, thereby opening up completely new application possibilities. They can be used, for example, in illuminated billboards, emergency signs and as courtesy lights on stairs. Osram experts also believe that OLEDs will serve as new decorative lighting elements on walls and windows. They have potential as transparent and colorful room dividers, illuminated wallpaper, and flat luminescent ceiling units that emit the same color spectrum as the sun.

Today, OLEDs are roughly where LEDs were at the beginning of the 1990s. Development is proceeding rapidly, however, thanks to several cooperative projects, including the European Union’s OLLA project and the OPAL 2008 project, which is funded by the German Ministry of Education and Research. Osram OS, BASF, Aixtron, Applied Materials, Philips, other companies, universities and research institutes involved in the project plan to cover the entire OLED value chain, from materials to complete OLED lights. The goal is to rapidly develop the basis for low-cost manufacturing techniques that will lead to marketable products. Germany and Europe hope to become the leaders in OLED lighting systems.

Some 40 experts are working on the development and optimization of OLED light sources and production processes at Osram and Siemens, especially at Osram OS in Regensburg. Although they have already built OLEDs with a lifespan of 6,000 hours, their target is at least 10,000. The efficiency of units produced in the lab is already more than 25 lm/W, a figure the researchers plan to double. They’ve also greatly improved OLED luminance, which is currently 1,000 to 1,500 cd/m², or ten times higher than that of a white piece of paper exposed to typical office lighting. Illuminated signs for emergency exits, for example, require several hundred cd/m², while general lighting requires 1,000 to 2,000 cd/m².

The biggest challenge at the moment is to develop production techniques for wide-area OLED light sources of acceptable quality, reliability and homogeneity. If such low-cost mass production methods can be achieved, however, residents of major cities around the globe may one day be able to enjoy "a truly staggering array of lights more fabulous than anything ever dreamed of."