Novel LED Street Lights Help To Save

Researchers at the Karlsruhe Institute of Technology (KIT) have developed a new, more economical LED street lamp. Compared to conventional LEDs, up to 20% of the power consumption could be saved. Scientists could increase the efficiency and lifespan of LEDs by replacing the usual high-performance diodes with a special array of light dots - an arrangement of LEDs.

New switching concept enables many LEDs on a circuit board

It is difficult to connect a large number of LEDs in parallel because the failure of a single diode leads to failure of the entire system or part of it, explains Michael Heidinger from the lighting engineering institute that is carrying out the project. The alternative of connecting the LEDs in series is also disadvantageous, since a high voltage is required as the number of diodes increases. Because the legally permissible contact voltage, which is not considered to be life-threatening, is 120 V, it has so far only been possible to install up to 40 LEDs in a series connection.

Heidinger has devised a circuit that absorbs the aging and failures of individual LEDs. This should make it possible to mount many LEDs on a single board and operate them safely at low cost - in the prototype there were 144 light points. The new switching concept should make it possible to work with much lower voltages. "In this prototype it was 20 volts," says Heidinger.

Small LEDs have pleasant lighting properties

In addition, the construction leads to less undesirable heat development. "With a few LEDs, the power loss is very concentrated and has to be distributed in a complex manner," explains Heidinger. A lack of heat distribution leads to a shortening of the lifespan of the lights. However, distributing or reducing the heat is complex and therefore expensive - costs that can be reduced with Heidinger's LED arrangement.

Heidinger also believes that the lighting properties are more pleasant for the human eye: “Many small LEDs are perceived as surface spotlights from a distance. As a result, they dazzle less than high-performance LEDs, which are perceived as point light sources.”On top of that, low-power LEDs are cheaper than high-performance LEDs, so that the new system can be manufactured and offered at the same price, even though more LEDs are required. After all, the switch to the new lamp technology is straightforward and therefore inexpensive: "The LED module can simply be installed in the existing lights," says Heidinger.

Light and architecture

Artful lighting solution with LEDs for the Elbphilharmonie

The first industrial partners develop luminaires

Cities and municipalities can benefit from the energy-saving properties of the new LED luminaire in the future. The conversion of the old power-guzzling street lighting to LED technology is in full swing in many places. For example, city lighting in a medium-sized city with 300,000 inhabitants such as Karlsruhe comprises almost 60,000 lamps, according to the city administration, whose electricity consumption in 2015 was around 12,000 MWh. Annual electricity and maintenance costs: 3 million euros. In the metropolis of Berlin, the energy costs for electrical public lighting in the same year totaled around 14 million euros. 75,000 MWh of electricity were used.

lighting

Petersplatz shines in new LED light

The first industrial partners are already in product development based on the Karlsruhe technology. "With the technology, we can for the first time design glare-free lights with high efficiency that meet high safety standards," says Klaus Müller, Managing Director of Gratz Luminesance. "This year we want to make our lights available to the first test customers for testing purposes." (Kj)