With the new tunnel luminaire from Siteco, significant energy savings can be achieved thanks to efficient LED technology and lighting controlled according to requirements. A further benefit: the LED tunnel luminaire is almost maintenance free, a factor that is extremely important for reducing costs with tunnel lighting.

In Germany there exist around 300 road tunnels with a total length of over 240 km. How efficiently the underground traffic arteries shorten travel duration and reduce the effects of noise and exhaust fumes is always then seen when their operation is disrupted. If maintenance work needs to be carried out, traffic jams and annoying diversions are often unavoidable. Such nuisances can now be significantly reduced, at least in terms of tunnel lighting. Long-life LED technology achieves the drastic extension of maintenance intervals and also has many additional benefits. With suitable planning it creates improved visual conditions, can be more simply controlled according to needs and operates with greater energy efficiency than conventional lighting solutions.

High-end design of optics for homogeneous, glare-free light

The core of the Siteco tunnel luminaire is an LED array with 56 white high power LEDs. Siteco has developed a custom-designed optical system in order to convert the high luminous flux of the discreet LED light points into suitable light distribution. A lens in front of each LED and a glass diffuser disc as luminaire enclosure achieve symmetric distribution of light, the basis for uniform and glare-free tunnel lighting. If against expectations an individual LED fails, the luminaire still emits homogeneous light. The high uniformity of luminance in the transverse direction (0.6) and longitudinal direction (0.4) ensure excellent visual conditions on the carriageway. A further plus in this respect is the high colour rendering index of Ra > 80.

Effective functionality for efficient thermal management

Effective thermal dissipation from the diodes is indispensable for operation of an LED luminaire. The junction temperature of the semiconductor determines both the luminous flux and the service life of the system. A 2% to 3% lower junction temperature for example extends service life of the LEDs by 7% to 9%. In view of this, the Siteco engineers have placed particular focus on thermal management with the development of the LED tunnel luminaire. The complete rear of the luminaire is covered by a 900 mm x 250 mm heat sink of corrosion-resistant aluminium. This extruded AlMg 2.5 profile with cooling ribs guarantees that the surface temperature of the luminaire remains consistently below 40°C and that the LEDs achieve their maximum service life (with ambient temperatures of a maximum of 25°C). As a supporting measure the cooling ribs are black anodised for improved heat dissipation, and the heat sink and luminaire housing are thermally coupled to achieve a larger surface area for heat dissipation and convection. Siteco also put its expertise to the test with the LEDs: their geometrical arrangement (for improved convection) and the use of special soldering processes and graphite foils (for improved heat dissipation) additionally optimise thermal operating conditions for the luminous semiconductors.

Intelligent electronics for highly flexible lighting control

Advantages such as loss-free dimming and instant start and re-start without time lagging are already part and parcel of LEDs. These technology-based benefits are supported by Siteco with an in-house developed and manufactured driver for the tunnel luminaire. Its electronics ensure careful operation of the LED module and enable efficient control.

The luminaire is suitable for integration in all standard lighting control systems. This means that with larger tunnels, realisation is easy for adaptation of luminance to daylight at the tunnel entrances and transition zones or for control of lighting depending upon traffic volumes. In this respect the luminaire can not only receive control signals but can also report back operation data such as actual values for voltage, electricity consumption and temperature, the exceeding of limit values with diverse parameters, or the DALI status (short-circuits, LED fault, temperature overload). Output of this data is carried out via an OPC interface.

Robust and reliable: a proven housing solution

In terms of the mechanical and construction properties of the new LED tunnel luminaire, Siteco has the benefit of 30 years of in-depth experience. Globally, over 450 kilometres of tunnels and traffic galleries have been equipped with around 260,000 Siteco luminaires. The depth of knowledge and experience gained in this respect has been integrated into the new LED tunnel luminaire. The inner of the luminaire is protected by corrosion-resistant, etched and passivated stainless steel (1.4571/ASI316 Ti). In combination with a high quality sealing system the luminaire complies with insulation class II and achieves IP67 protection. Siteco has classified the tunnel luminaire as a CPP luminaire (Corrosion Premium Protection). This means that it is especially resistant against aggressive environmental factors found in tunnels (acids, salts etc.).

Despite this fact the luminaire can still be opened for maintenance work. The replacement of individual component groups is highly simple thanks to modular construction. All components can be easily separated due to plug and screw connections. This principle also significantly simplifies waste disposal of the luminaire. In this way it even benefits the environment at the end of its service life. Before before such as situation comes about, the tunnel luminaire achieves significant energy savings over a period of many years thanks to efficient LED technology and lighting control according to requirements.

Photos: Siteco