Lighting accounts for a quarter of energy costs in Europe. Replacing outdated light bulbs with more advanced devices is an efficient way to cut our energy bill. Science and industry have joined forces in a European project to develop cheap and stylish alternatives to modern lighting. Putting a new light on energy efficiency, in this edition of Futuris.
Light is a perennial problem in museums, but Dresden’s City Museum is shining a light on the future: each of more than a thousand fluorescent tubes and halogen spots placed in the historical building are controlled independently through a computer network. Various programmed lighting modes are changed with a press of a button.
Grisbert Portsman, Director of municipal museums of Dresden: “We were looking for a modern lighting system and found one. It was important for us to find a system which could give us required flexibility. We have a range of exhibits each demanding its own lighting to allow us create an adequate atmosphere.”
“Smart lighting” systems are spreading all over the globe: it’s a modern way of maximizing the efficiency of energy spending by fine-tuning each individual lamp’s brightness, adjusting it to constantly changing natural light conditions.
But is this the best we can do?
Students at Gent University in Belgium are participating in a European project that aims to develop a completely different source of light to anything we use today, based on organic light-emitting diodes.
Kristiaan Neyts, Gent University professor: “Current lighting isn’t very efficient. The aim of the European project on which we are working, which is based on organic LEDs, is to reach a type of lighting which is more efficient – about twice as efficient as compact fluorescent lighting and 8 times more efficient than incandescent lighting. So if this comes into effect we would save a large amount of energy. And we work on this project with a number of European partners.”
The properties of organic light-emitting diodes are attracting the attention of many researchers and industrial developers: such devices can shine as brightly as traditional lamps, but require much less power.
Inorganic LEDs, producing tiny bright dots of light, are already used for spot lighting. Organic LEDs are not dots. Instead they produce large glowing surfaces, made of chemical components that are cheap and plentiful.
Stefan Grabowski, OLED100.eu project coordinator: ”The oldest technology is the standard light bulb. It’s a very cheap lamp, but it’s rather inefficient, as known to anybody who’s ever touched one: most of the energy is transformed into heat and not light. A fluorescent tube is much more efficient – it has a different working principle based on gas discharge. But the main drawback is that it’s always confined to a linear shape.
In the future we will have another lighting product called OLEDs – that stands for organic LEDs, that we are working on in a European-funded project OLED100.eu: it’s a very efficient light source, it has very nice properties unheard of with other light sources.”
This technological breakthrough stems from the discovery of electroluminescence in the 1950s: some materials were found to emit light in response to an electric current passed through them.
But it took decades for scientists to apply that knowledge to get a practical result. The experimental technology existing today only allows the production of very small OLEDS – and even small ones are still too expensive to be generally affordable.
Gerd Much, engineer, Philips Research: “We use a vacuum because the materials are organic and they oxidise on contact with air. Glass substrates are put into the vacuum chamber and covered with this organic material, putting on the right amount to get the color we need. You can compare the process with water boiling: small molecules of material evaporate and condense on the glass.”
An OLED itself is an incredibly thin film of organic semiconductors, a thousand times thinner than a human hair, sandwiched between two electrodes in an airtight enclosure.
When current is applied to the electrodes it flows through the organic film, and the film emits light.
Using transparent plastics instead of a glass substrate, one can potentially make a flexible OLED lamp, capable of being rolled-up or wrapped around an object.
Karl Leo, Institute Director of the Fraunhofer IPMS: “Organic LEDs mean a new quality of life: they are potentially flexible, large-area, highly efficient, with very good color rendering, so for many illumination purposes they are the ideal light source.”
The prototypes existing today demonstrate a number of features inherent to this type of device: they are uniquely thin unlike any other light source, fully bright instantly after being turned on, easily dimmable and even – possibly – transparent.
Stefan Grabowski, OLED100.eu project coordinator: ”One of the most striking features of organic LEDs is that you can make them transparent, and that is unheard of with any other light source. That means you can have a light source which you can look through in the “off” state. That is a very interesting feature, because that means you can now integrate OLEDs into windows.”
So in the future our rooms might look like this: thin strips of OLED material are integrated into the furniture, walls and ceilings; windows and mirrors could provide cheap mood-setting lighting. If the performance of such devices improves as expected, in several years the lamps we use today may seem as obsolete as oil lamps or candles.
Unfortunately, any mass production of OLED lighting devices won’t start until all the technological barriers are removed. So far even a tiny dust particle can destroy an OLED before it’s produced, making the fabrication of larger panels increasingly costly and complicated. Another issue is that OLEDs don’t yet maintain their brightness long enough to compete with traditional light sources.
Karl Leo, Institute Director of the Fraunhofer IPMS: ”Organic LEDs need to be significantly improved, so that we would have higher efficiency, longer lifetime and lower production costs. The challenge is that it’s a very interdisciplinary field ranging from chemistry to physics to engineering, and the advantage of this project is that you can easily bring those disciplines together.”
The international project is being coordinated from Aachen in Germany and involves six European countries. On its completion in the summer of 2011 the scientists expect to have OLEDs as large as one square meter, twice as efficient as fluorescent tubes, relatively cheap, and with long lives.
Stefan Grabowski: “OLEDs are part of a revolutionary change in lighting technologies compared to the old, traditional lamps which are based on gas discharge – this is now solid-state lamps, similar to LEDs. In my perfect world of the future there will be only perfect spot sources – LEDs – and perfect area lighting sources, which are OLEDs.”
Lighting applications account for a quarter of total energy spending in Europe. Switching to the more efficient technology might allow to cut that portion of electricity bill in half. One doesn’t need to be a fortune teller to see how bright that future might be.