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SIEMENS

Research & Development
Technology Press and Innovation Communications

Dr. Ulrich Eberl
Herr Dr. Ulrich Eberl
  • Wittelsbacherplatz 2
  • 80333 Munich
  • Germany
Dr. Ulrich Eberl
Herr Florian Martini
  • Wittelsbacherplatz 2
  • 80333 Munich
  • Germany
pictures

While a photovoltaic module first converts sunlight into electric energy, so-called “Sollektors” transport daylight directly. Light is captured by 900 lenses.

While a photovoltaic module first converts sunlight into electric energy, so-called “Sollektors” transport daylight directly. Light is captured by 900 lenses.

While a photovoltaic module first converts sunlight into electric energy, so-called “Sollektors” transport daylight directly. Light is captured by 900 lenses.

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Let the Sun Shine In!

Capturing sunlight and using it where it's needed is an ageold dream. Together with a university in Nuremberg, Osram is developing a lighting system that combines fiber optics with LED technology. The trick is to balance these two sources to dynamically achieve the color and intensity of sunlight.

Image While a photovoltaic module first converts sunlight into electric energy, so-called “Sollektors” transport daylight directly.
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Image Light is captured by 900 lenses.

As legend would have it, the citizens of a town called Schilda — the Schildbürger — always had plenty of bright ideas. But they always blundered when they tried to put their ideas into practice. When they were building a new city hall, for instance, they forgot an important detail: the windows. So to brighten up the interior, they collected daylight in cooking pots and carried it into the building. Unfortunately, it didn’t get any brighter.

The basic idea behind the Schildbürgers’ big blunder has now been seized upon by Professor Hans Poisel, a lighting expert at Georg Simon Ohm University of Applied Sciences in Nuremberg. Over the past four years, along with his students, he has developed a device soon to be installed on rooftops: the Sollektor. A square plate with sides about the length of one’s forearm supports 900 shiny lenses that collect sunlight and feed it into polymer fiber optic cables like the ones used for data transfers. The light travels through these plastic conductors to ceiling-mounted light fixtures where it is emitted. What’s more, only wavelengths that are visible to the eye are conducted. Harmful ultraviolet and infrared components of the spectrum are blocked.

“When we talk about solar energy, we usually think about photovoltaic or solar thermal systems,” says Poisel. “In those methods, light is not even fed into the system but is converted into other forms of energy. What we are striving to do, on the other hand, is to use this original form of energy — sunlight — without converting it and with low transfer losses.” In the process of generating electric power with photovoltaics and then converting it into artificial light, approximately 99 percent of the solar energy is lost. The Sollektor, on the other hand, achieves an efficiency of over 50 percent. “We bring daylight to interiors where nature is normally excluded — into the dark cave of the office where people spend most of their time,” Poisel says.

It’s easy to laugh at the Schildbürgers. No modern architect would forget to include windows when planning a building. But to call our way of lighting a building efficient would be a fallacy. No sooner does the summer sun glare into the windows than the blinds go down and the lights are turned on. This is especially true for regions in the southern hemisphere. We spend 90 percent of our time in enclosed rooms, working and living under artificial light. Consequently, almost one fifth of worldwide power consumption is spent on illuminating interiors — even during the day.

Daylight Plus Color LEDs. Even the savings potential of a single Sollektor gives you an idea of what could be achieved with widespread utilization of daylight. When the sun is shining, the transferred light is sufficient to replace twelve ordinary 60-watt incandescent bulbs. During the 1,700 hours the sun shines annually in Germany, a single Sollektor could save up to 1,200 kilowatt hours of electrical energy.

But even the fiber optic approach has its limits. Once the sun has set, an electric alternative is indispensable. Development engineers in Nuremberg are therefore working with Osram to combine the best of both worlds. Their goal is a solution in which daylight is variably admixed with artificial light depending on available light intensity — as controlled by intelligent sensor technology. The system can be integrated into a single ceiling light.

Osram uses LED technology for this purpose. Luminous semiconductors not only replace natural daylight, they also provide illumination with a changing color temperature — which gives a boost to both comfort and health. In particular, the blue components of natural daylight affect our inner clock, as well as our sleeping and waking rhythms (see Pictures of the Future, Fall 2010, Duplicating Daylight). “To reproduce this effect in the interior of a building, the color spectrum of the light, as well as its intensity, must be constantly adapted dynamically,” explains Henry Feil, Innovation Manager at Osram in Munich. In the morning and evening hours, the blue component of the artificial lighting source must be reduced and red is admixed.

The results of the joint research project between Ohm University and Osram have spawned a combination of energy efficiency and heightened appreciation for the quality of life associated with natural light. As innovation manager, Feil interacts with a network of young development engineers. “We have a research environment that’s driven by competition between ideas,” he says. “You’ve got to be in touch with people. Anyone who contributes good ideas deserves support,” he says.

Osram supports the project’s young researchers by providing know-how as well as the latest LED and sensor system technology. “Open innovation” is what Feil calls it. “It’s as though we were pushing one another forward,” he explains. He is always able to help out when support is needed concerning technical lighting solutions, business plans, or market analyses. What he expects for Osram in return is new momentum that may someday give rise to a marketable product.

Initial interest in the Sollektor is expected to be limited to niche applications in Europe, Poisel believes. For example, it could ensure lifelike color fidelity in art galleries, for fitting rooms in upscale clothing stores, or for the vegetable sections in supermarkets. A key factor will be how fast an investment can be expected to be recovered through energy savings. Two of Poisel’s former students have already established their own company named Bavarian Optics. The Sollektor is expected to make its first market appearance in the course of 2011. By then this combination of fiber optics and advanced LED technology will have to be working flawlessly. Fundamental to the success of this sensitive control system are sophisticated algorithms that perfectly balance the two components of the system.

Automatic Balancing Act. A project at Siemens Building Technology in Zug, Switzerland, illustrates the system’s functional specifications. At first sight the project room appears to be an ordinary office with a black upholstered chair and a desk of light-brown wood with a laptop on it. But this is just an experimental setup. Bright sunlight enters the window. More light comes through a ceilingmounted fiber-optic source resembling a Sollektor — a product from Sweden that was already on the market when the Sollektor project was launched in 2008. Sensors mounted between the rectangular light panels in the ceiling continuously collect a large volume of data, which is used to intelligently control the building’s automation system. If there is too much incident light, for instance, the shades come down just enough to dim the lighting.

The experience that is being gained from this project flows into an EU-supported project called “Clear Up.” The project’s goal is to develop energy-efficient technologies for residential and commercial buildings. “Ambient conditions should not in any way impede anyone in the room. So the quantities of artificial light and daylight that illuminate the room are automatically adjusted to achieve an optimal balance,” says Philipp Kräuchi, who is managing the project. “All functions must be responsive to individual preferences regarding brightness and contrasts. If energy consumption is to be reduced at the same time, intelligent automation is indispensable.”

The next step in the research between Osram and Ohm University will be further development of intelligent sensor and automation technology with a view to optimizing the integration of the Sollektor’s fiber optic components and LEDs. While the research partners busy themselves with this challenge, they know that the sophisticated building systems they have in mind are out of reach for developing economies. Nevertheless, the Sollektor has already created excitement in the southern Indian city of Chennai. Two years ago, Poisel brought a prototype to the Indian Institute of Technology — Nuremberg’s partner university. Negotiations have taken place since then with the Indian Railway Company, which is interested in finding an efficient lighting solution for its production facilities.

While Poisel was sitting in a conference room during his most recent visit, the power suddenly failed — something that happens often in India’s big cities. The overhead projection image vanished from the wall and the air conditioning stopped humming. But in the building next door it didn’t get dark, even though the blinds were closed. The Sollektor on the roof wasn’t affected by the power failure. The Schildbürgers would have turned pale with envy.

Stefan Schweiger