Cutting-edge technology for historic cities

Efficient LED lighting in public spaces

LED technology has the potential to create huge energy savings, which can mean reductions in energy costs, more options for intelligent control systems and a significant improvement in light quality. The results of the “Freiburg LED Master Plan” demonstrate how LED technology can already be implemented in lighting for public spaces. The Steinbeis Transfer Center for Illumination Optics and Lighting Engineering was involved in the project.

With its “Communities in a New Light” contest, the Federal Ministry of Education and Research (BMBF) sponsored ten “Lighthouse Projects” with the aim of demonstrating the vast potential of new LED lighting technology in practice. A transition to cutting-edge LED lighting has put the Freiburg city center in a new light, accentuating the city’s landmarks, such as its minster, the street intersections (typical of such cities founded by the Zähringer nobility), the city gates and the historic city hall square. 

Freiburg’s Parks and Highways Department contracted the Steinbeis Transfer Center for Illumination Optics and Lighting Technology for scientific assistance on the project. As a part of this, light measurements as well as surveys were carried out prior to and after the switch to LED lighting. The planners of the new lighting had to make sure that the conversion would accommodate the masts in the existing city lighting as well as their arrangement – which created limitations for the planning process. These were typical of the challenges that arise in this type of conversion project. Therefore, the finalized lighting solution could be perceived as representative and applicable to other such projects. 

The level of conformity for the LED lights (according to DIN EN 13201 standards) as well as potential improvements or maintenance of lighting levels were established through lighting measurements in precisely defined measurement fields in representative sections of the historic city streets. Streets now emitting a lower level of lighting than they had prior to the conversion had been proven to exhibit excessively high lighting levels. Overall, the new lighting made an improvement on the evenness of the light and, thus, the actual light quality. The new LED lights are particularly energy efficient; energy savings amounted to between 50 and 68 percent. These results exceeded the project expectations and demonstrate LED technology’s potential for large-scale implementation in outdoor lighting. A further positive aspect of the conversion was a reduction in the use of high-pressure mercury bulbs – no longer permitted as of 2015 – in the Freiburg historic city center. 

As the project’s commissioner, the BMBF placed heavy emphasis on allowing the public to evaluate the new lighting and hoped to win public approval by breaking down typical stereotypes of LED lighting as being “too cold”. A survey developed by Steinbeis experts was used to analyze all relevant areas of light perception as well as all subjective opinions of the lighting, both before and after completion of the project. A total of 300 surveys were filled out. The purpose of the survey was also to incorpo­rate the results of the lighting situation before the project into the new LED lighting plan. For example, 52% of participants described the previous lighting using warm white tones as “ok”, while 36% found it “too cold”. Accordingly, planners seriously put a lot of thought into the lighting tones, and a warm white hue was chosen for the newly de­veloped LED lights – especially for the city park. 

The results were resoundingly positive: after the conversion, 76% were satisfied with the light tone; only 15% felt the lighting was “too cold” and 5% “much too cold”. The brightness of the new LED lighting also received positive feedback. While 63% of participants rated the lighting neither too bright nor too dark prior to the conversion, 85% were satisfied with the brightness level afterwards. 56% answered “very good or good” to the question “How is the new lighting?” Only 7% and 5% answered with “neutral” or “bad”, respectively. All in all, it can be concluded that the LED lighting received very positive responses from the survey participants, especially in the areas of security, recognition of people and obstacles, glare, tone and brightness. 

With the Freiburg LED Master Plan, a conclusive and holistic lighting concept was developed that connects modern technology with the city’s historic elements – enhancing the city’s overall image. Despite its many successes, the project still met with technological limitations and problems in the supply chain. In particular, the newly developed lights revealed their technical limits in real-life application: the LED light source modules were put to the test in terms of irreplaceability and interchangeability, and the depth of manufacturer guaranties had to be redefined over and over. In this case, LED manufacturers and lighting companies had to under­go a maturity process to reconcile the worlds of opto-semiconductors and the preparation of high quality light for general lighting use. 

This and many other issues relating to LED technology is the focus of the third International LED Professional Symposium + Expo (LpS 2013) from September 24-26, 2013 in Bregenz (Austria). The symposium is receiving scientific support from the Steinbeis Transfer Center for Illumination Optics and Lighting Engineering. This key convention and trade show has plenty to offer, from expert presentations, workshops, and technical panels to a lighting art project and countless exhibitors. With over a thousand expected visitors, it has established itself as the leading event on LED technology for Europe’s lighting industry.

Share this page