The usage of LED lamps instead of conventional lamps can save a lot of energy. On the Danube Island the transition to LED lamps will refinance within 10 years.
The use of LED lamps for public lighting is seen as an opportunity for increased energy efficiency and energy savings. The efficiency and luminous flux of LEDs have increased substantially in recent years, making it possible to nowadays use them in street lighting. It should be borne in mind, however, that an efficient light source does not in itself create efficient lighting.
LEDs can only fully achieve their enormous potential in conjunction with modern luminaires. A modern LED streetlight consists of the housing, the LED module, the driver (power supply for the LED module) and optical systems for light guidance (e.g. lenses, microreflectors). The LED module generally consists of a number of individual LEDs. The light output of an LED already lies above that of conventional light sources used in street lighting. But the development of LED lighting is not yet complete, since certain challenges especially relevant in outdoor lighting still have to be resolved.
Advantages of LEDs
- A high service life of 30,000 to 50,000 hours (corresponding to around ten years) is guaranteed.
- Lower degeneration compared to conventional luminaires (still 80 per cent of the luminous flux after 30,000 hours of operation).
- In contrast to fluorescent lamps, there is no reduction in the luminous flux at low temperatures.
- Good dimming properties enable them to be readily adapted to the necessary luminous flux.
- The degeneration of the LEDs can be well compensated for by the software in modern drivers.
- Dazzle effects from extremely bright light spots
- Protection of the electronic systems against surges and electrostatic loads (e.g. in the case of storms): Überspannungsfestigkeit von LED-Leuchten (only German)
- Dynamics of further development (maintaining a supply of spare parts, delivery times, interfaces, storage, etc.)
Use in Vienna
Based on the experience of the municipal department “Public Lighting” (MA 33), LED street lighting has great potential for use along secondary roads and paths (footpaths, cycle tracks, car parks, etc.). Therefor MA 33 began to install LED systems in those areas in 2009. In future LED technology will be the sole source of lighting here.
With the exception of some test systems, LED lighting is currently not used in the primary road network, due to a lack of long-term experience. In order to gain experience in this section, MA 33 has been working together with various manufacturers to install LED test systems since July 2011.
LED with solar power supply
In the past, LED lights were also tested with a solar power supply. However, this technology has been shown to be problematic for the following reasons:
- Reduced solar irradiation in the winter months (fewer hours of sunlight, misty weather, shading due to the low position of the sun in the sky)
- Reduced battery capacity due to the cold
- Limited service life of the batteries used
- Reliability and service life of the electronic components (charging technology, solar cells) is not guaranteed
- Higher maintenance costs for battery replacement and cleaning of the solar cells
- Use of ecologically suspect materials (lead, acids, etc.)
This means that assuring the solar lighting of highways, footpaths and public areas in accordance with the standards cannot be guaranteed, especially in winter months. The cost of setting up such a system, per point of light, is similar to that of standard systems, but the operating costs spectacularly exceed the costs of conventional lighting systems. Solar lighting technology is therefore not currently used for the lighting of parks, highways and footpaths in accordance with the standards.
Refitting on Danube Island
The refitting of the globe lights on the Donauinsel (Danube Island) is a good example of how the possibilities of LED technology combined with modern light fittings can be used to optimise energy savings while improving the lighting levels. In addition, as shown by one of the ecological studies undertaken during the process, the refitting achieved to reduce the negative effects of artificial lighting on the insect world by around 80 percent, depending on the insect family.
The refitting of around 1,200 lights on the Donauinsel and along both banks of the Danube was completed in early 2013. Reduction of the electrical output from the 89 watts of the original globe lights to the 17.6-watts LED units results in annual energy savings of around 370,000 kWh. These savings mean that the refitting will pay for itself in just under ten years.
Ing. MMag. Gerald Wötzl, Bakk.
MA 33 – Public Lighting
This post is also available in: German