Retrofit existing luminaires:
»We’re in a learning process«
Insight
In conversation with
Anders Hedlund, Lighting engineer at the Traffic Office of the City of Stockholm
Over the past ten years, Stockholm has transitioned much of its conventional street lighting to modern technologies. One of the city’s key objectives was to find sustainable solutions that would allow existing luminaires to be refurbished and continue operating for another 25 years or more. Within this large-scale modernisation programme, Selux supported the City of Stockholm with series retrofits. The project upgraded approximately 500 ›Discera‹ , 700 ›Saturn‹ , and 1,400 ›Park 26‹ luminaires, successfully implemented at city-wide scale.
A lamp lighter with their oil can by Stadshusbron's west side (1790)
»In the beginning,« Anders recalls, »we weren’t sure how to approach it. We wanted to reduce energy consumption, of course, but at the same time the lighting had to create a pleasant atmosphere and maintain good visual comfort.«
Extensive planning went into preparing the renewal project. Ultimately, however, real-world experience proved just as important as technical preparation. As Anders puts it: »We’re in a learning process.«
Balancing atmosphere, comfort and efficiency
Stockholm’s approach has been to strike a careful balance between visual comfort, atmosphere and energy efficiency. By using Selux Tritec technology, the city has been able to retrofit existing luminaires — such as the Park 26 — rather than replacing them entirely. This has helped reduce both energy consumption and light pollution, while preserving the characteristic appearance of Stockholm’s street lighting.
The Park 26, a functionalist design dating back to 1926 and owned by the City of Stockholm, was already technically updated in 2001, while its historic appearance remained unchanged. Retrofitting the luminaires once more allowed the city to preserve their heritage while upgrading them to current lighting standards. People adapt quickly to the new lighting, Anders notes. »LEDs give you more uniformity and reduce highlights. It might feel different at first, but people get used to it very quickly.«
Park 26 by Stockholm’s riverside — a design from 1926, unchanged to this day
Tritec retrofit optics
Tritec is Selux’s modular optic platform for precise light shaping across streets, walkways and urban spaces. Tritec Ambiance brings more vertical light and soft transitions, brightening façades and creating an airy, welcoming atmosphere in lanes and squares. Tritec Sky sets distinct accents that make colours, forms and textures tangible – while protecting the night sky. Available in gold or silver, with up to 96 configurations – ready for retrofit upgrades.
Read more
Smarter lighting with Zhaga
Today, roughly 50,000 luminaires in Stockholm are equipped with the Zhaga interface, a technology standard that enables intelligent lighting control and data exchange.
Zhaga interface
»The Zhaga interface gives us several advantages,« Anders explains. »We can precisely control the luminaires, apply different dimming levels and manage lighting individually in sensitive areas.«
»We’ve been using automatic dimming for around ten years, and no one has ever complained that it’s too dark. And if we needed to, we could always change it.«
Zhaga also supports more efficient maintenance and quality control. When similar-looking luminaires are installed in different configurations across the city, the interface allows the team to verify that the correct models are installed in the right locations. At the same time, standardised communication opens the door to cooperation between cities. »It helps us establish shared standards with other municipalities, such as Malmö, making it easier to develop common solutions and ultimately increasing overall efficiency.«
Planning for a sustainable future
Thanks to careful preparation and close collaboration with Selux, the conversion process has been relatively time-efficient. Selux delivered tailored retrofit solutions for both its own luminaires, such as Discera and Saturn, as well as for third-party products. Referring to the Saturn retrofit with Tritec, Anders notes that it was a good template for the Park 26 model. »Of course,« he adds, »the actual effort depends on the luminaire. The Park 26, for example, was fairly easy to upgrade.« In practice, he estimates that retrofitting and full replacement often require a similar amount of time.
So far, around two-thirds of Stockholm’s street lighting modernisation has been completed. The remaining third is expected to follow the same principles of long-term planning, technical flexibility and sustainability.
»Personally,« Anders adds, »I’d like to see sustainability play a bigger role in lighting design in general. New solutions should be developed with older models in mind, so we don’t have to spend so much time and resources figuring out how to retrofit them. That would not only save money but also reduce waste.«
An upgraded version of a Park 26 luminaire with Tritec Ambiance
Anders Hedlund
Lighting engineer Traffic Office of the City of Stockholm
This text is based on a conversation with Anders Hedlund, who has spent his entire career in the lighting industry. Since 2012, he has been working as a lighting engineer focused on strategic planning at the Traffic Office of the City of Stockholm. In this role, he is responsible for managing contracts with lighting suppliers and overseeing the modernization of Stockholm’s street lighting infrastructure.
