Project: Freiburg shines in LED light

Sustainable lighting solutions

Public lighting systems
switched to LED technology

After upgrading the inner-city lighting to modern LED technology, the historic city centre of Freiburg presents itself in a pleasant atmospheric light: 223 historic and 80 technical luminaires were modernised in cooperation with Hess over the past three years as part of the BMBF competition "Municipalities in a new light". At the same time, the Gothic cathedral, the city gates and the town square have received atmospheric lighting effects from Hess.

LED Master Plan

Prior to the conversions, the city government commissioned the planning office Generation Licht from Hemmenhofen, Germany, to create a LED master plan. This plan should increase the quality of light and should serve as foundation for future energy-saving lighting solutions at the same time.

The LED master plan Freiburg had the task to capture the entire historic city of Freiburg and to coordinate the evening appearance of the cityscape defining elements to each other. It was the stated aim to make the historic structure and the historic city more visible and to increase their awareness to visitors and residents again. The lighting solutions implemented in the inner-city, the city gates, the city garden, the cathedral as well as the town hall square valuably contribute for this purpose.

Wide range of applications of LED technology exploited

Exemplary lighting concepts

Through a wide range of applications in the illumination of squares, street lighting and effect lighting, the jury accounted the transferability of lighting solutions to other districts as exemplary and thus the goal of the competition as reached.
"In detail, 223 historic and 80 technical luminaires were converted. As we wanted to maintain the white light in the inner-city and still had largely mercury vapour lamps installed there, the competition provided the opportunity to quickly update to the latest technology. In addition and in the area of the illumination of historic buildings, the chance was opened to fulfil our long-awaited desire to completely illuminate the cathedral of Freiburg”, summarises Franz Bühler, Head of New construction in the Section of Infrastructure of the Department of Civil Engineering, the urban matters.
The BMBF project encompassed the following subprojects:
•  Modernisation of the historic city luminaires in the inner-city
•  Modernisation of the existing luminaires in the city garden
•  Lighting of the town hall square
•  Illumination of the cathedral
•  Illumination of the ancient city gates
•  Lighting of a test track with LED solar luminaires at the riverside of the Dreisam

Franz Bühler

Head of New construction in the Section of Infrastructure of the Department of Civil Engineering Freiburg

"As part of the project "Municipalities in a new light", already about 50% of the inner-city was converted to LED. We were thereby able to achieve 62 percent of energy savings. Due to the good experience we will also change the remaining luminaires to LED within the next years."

Photometric on-site measurements

Data for the quality of lighting

The technical university of Darmstadt and the Steinbeis transfer centre for illumination optics and lighting took photometric measurements to collect data on the quality of lighting and energy consumption for the old and new lighting before and after the conversions. The results of the preliminary measurements were included into the planning considerations for the new lighting and have contributed significantly to the product selection. Moreover, citizens were interviewed before and after the conversion to capture the acceptance of LED lighting in the population.

Customised lighting concepts

By taking various technical and design requirements into account, about 300 luminaires have been upgraded in Freiburg’s historic city, including 223 historic Schelenz-, Freiburg- and Baden-Baden luminaires as well as 36 catenary-suspended and 44 pole mounted luminaires.
The historic luminaires were equipped with the LED retrofit kit "cLED" by Hess in bulb look, especially developed for this type of luminaire – enabling the luminaire heads to be preserved. The warm colour of light ensures an atmospheric illumination of the environment. With a constant or increased mean illuminance and a higher uniformity of the lighting system, about 50 to 60 percent of energy were saved.
In addition, different Hess luminaires were used, for example the pole top mounted luminaire RESIDENZA in the city garden and Schiffstreet as well as the catenary-suspended luminaire NOVARA with the LED module LEVO, among others, in the Herren-, Schuster- and Merianstreet. With a warm light colour of 2900 Kelvin they provide for a very pleasant lighting and a uniform, glare-free light distribution.
Today, visitors can experience a unique interplay of innovative LED technology and Gothic cathedral architecture at the cathedral square of Freiburg. 55 of the overall 119 built-in LED spotlights have been installed as in-ground luminaires around the cathedral landmark. They effectively illuminate the façade, the figures, the Gothic portal as well as the south portal in Renaissance style.

60 percent energy savings

In the course of the realised retrofitting, the city government has achieved energy savings of 62 percent. As a result, CO2 emissions are reduced by 67 tons per year.

Great approval for new lighting

The evaluation of the extensive public surveys shows a very broad acceptance of the new LED lighting by the population. "In particular, the sense of security has increased significantly among citizens and pedestrians after the conversion. Also the choice of the light colour of 2900 Kelvin contributes significantly to the perception of LED lighting as pleasant light", says Franz Bühler. In addition, the inner-city areas are attributed an increased attractiveness.

Due to the very good experience with the new technology, the city government plans to continue the modernisation of the existing luminaires. "As a Green City Freiburg is open for new technologies that enable energy savings and reduce CO2 values", adds the responsible project manager of the Department of Civil Engineering in Freiburg, Franz Bühler. The conversion of the remaining inner-city luminaires to LED technology is planned for the coming years.