Lighting up the streets

4th July 2014
Nat Bowers


Meeting demand for more efficient street lighting outperforms off-the-shelf. By Pablo Gascue, Field Sales Engineer, Rutronik Spain.

Spanish manufacturer SECOM has developed the Dural LED streetlight for contemporary street lighting.

Within its injected aluminium housing the Dural LED streetlight incorporates 28 Osram Golden Dragon Plus LEDs. Each LED is provided with a PMMA secondary optic (polymethylmethacrylate) from LEDIL, which directs and disperses light with minimal reflection losses. A polycarbonate protective layer protects the light against UV radiation and thus extends the life of the lamp, keeping the same characteristics against the passage of time. The Dural streetlight is available in many variants with different colour temperatures, transmission angles and power values.

One SECOM customer was convinced by the features of the Dural, but they wanted a model which did not exist at the time: It was to deliver a brightness of 8000 lumen with a maximum current consumption of 100W. The existing variants either exceeded or fell short of the specified limits for both values. The challenge was therefore to increase the efficiency of the light. As this was not possible with the existing LEDs, SECOM turned to Rutronik for help.

On the basis of the specified technical characteristics, the distributor came up with a preselection from which SECOM selected the Oslon Square from Osram Opto Semiconductors. The LED is very efficient as its reflective housing allows for optimal dispersion of the light. “Rutronik’s process for providing us with samples was quick and uncomplicated, enabling us to create a prototype to test whether we could achieve our goal with this design,” explained José Antonio Fernández, R&D at SECOM. The tests showed that the light did not generate more than 7000 lumen. This was due to both mechanical factors as well as material factors, such as the intrinsic losses caused by the polycarbonate with UV protection, and its spherical form which minimally dispersed flow by reflection.

Pushing the limits

In order to achieve the benchmark of 8000 lumen, SECOM suggested increasing the number of LEDs. In order to do this, the input current had to be lowered so not to exceed the specified maximum power consumption of 90W. Rutronik proposed semiconductor options that best fit the requirements of the project, like Ostar, Oslon square and Oslon SSL. Another LED had to be selected, as the required number of Golden Dragon Plus LEDs could not be accommodated on the PCB. As a result, cost also played a part because the greater number of LEDs meant that the price for the end product could not be increased exorbitantly. “The support we received from Osram Opto Semiconductors and Rutronik was absolutely crucial. Working together, the partners were able to come up with a solution which fulfilled both our technical requirements and our commercial objectives,” José Antonio Fernández said.

The eventual choice was the Oslon SSL, which with a component size of 3 x 3mm is a lot smaller than the Golden Dragon Plus, which measures 5 x 6mm.This enabled two LEDs to be integrated into one optic, with the result that a total of 56 Oslon SSL could be placed in one streetlight. What really convinced SECOM about the Oslon SSL in particular was its high light output: It achieves a typical light yield of 96 lm/W, making it one of the most efficient 1mm2 chip LEDs on the market and excellent price/lumen ratio.

Moreover, Osram Opto Semiconductors was able to stabilise the luminous flux even with increasing temperatures, so that the light yield remains virtually constant. The curvature, which presents the design of the luminaire, distributes the heat in an adequate way. It dissipates the temperature with the help of the aluminium luminaire acting as a large sink. This simplifies the thermal management.

Custom solution

In the customer-specific version of the Dural LED streetlight, the LEDs function at an operating current of 700mA. “We were very excited to see the results of the tests with the new prototypes,” recalls Fernández. It was clear: The light now generated the required brightness of a minimum of 8000 lumen with a power consumption of 90W.

The customer was extremely pleased with the result. They will use over 10,000 luminaires for lighting an 8-lane vial in each direction in Mexico. Its outstanding characteristics mean that, in the future the model will also become a permanent feature of the Dural range.

“Our collaboration with Rutronik and Osram was extremely professional,” said José María Sandoval, CEO of SECOM. “We believe innovation and quality are key to us remaining competitive. In this respect, both the distributor and the manufacturer have provided us with outstanding support. We are now working with these two partners to develop other LED lights.” For example, the DURIS E3 from Osram Opto Semiconductors is being used in the Eslim LED panel light. With its small lumen packages, it ensures exceptionally uniform illumination and a high degree of visual comfort. The 60 x 60cm Eslim model contains 624 Duris E 3 0.065 W LEDs and the 60 x 120cm version houses 936 of these LEDs. The innovative optic made from PMMA acrylic glass also contributes to the optimum light distribution and high efficiency.

SECOM chose the DURIS E 5 for the LED tube T8, a LED tubular light intended as a replacement for conventional fluorescent lighting. The aluminium body with a large dissipation surface takes care that the semiconductor does not exceed the recommended working temperature at any time, thus increasing efficiency and extending their lifetime. Their external driver with a direct current at low voltage makes it safer by avoiding possible ‘electrocutions’. It also prevents heat input between LEDs and driver. This type of technology makes the LED tube suitable for working under extremely low temperature, such as in cold rooms, and can support up to -20 ºC without attenuating its luminous flux.

SECOM has a lot of new projects in the street lighting area, too. At the moment they are developing streetlight luminaires driven only by solar energy as well as so called Smart Luminaires. They will provide several different control and monitoring solutions due to radio frequency systems.

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