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Cost-effective solution makes entry in LED solution easy

Because we want tomorrow's best, we prevent the good of today and retain yesterday's bad. This captures the words of former German Minister for the Environment, Klaus Töpfer, in describing the dilemma associated with many policy decisions related to energy. Investments are postponed in the hope of finding better and more efficient technical solutions. Many municipalities also find it difficult to start investing in modern LED technology at this stage, despite the fact that they can save up to 70% of their energy costs as a result. Whether it is worth clinging to energy-guzzling mercury lamps, though, is often less a question of what is technically possible than a matter of simple arithmetic.

Scepticism about LED technology is certainly no longer appropriate, says Prof. Tran Quoc Khanh, Head of Light Technology at the Technical University of Darmstadt: "In terms of service life, luminous efficiency and energy efficiency, LED technology is certainly ready for use as an efficient light source in street lighting." There is no question for the scientist that LED technology belongs in the future. Engineer Fabio Tinagli, whose company Helecta is based in Sittensen in Lower Saxony and specialises in the development of LED solutions for industrial and public areas, also sees great potential in this technology. "In the coming years the efficiency of LEDs will increase further", says Tinagli. The luminous efficiency, which today is in the range of around 100 lumens per watt, will markedly approach the physical limit of viability of 300 lumens per watt. The question is therefore justified: Should we start implementing LED technology now and immediately save costs with the LED products currently available, or should we wait until significantly more efficient products are on offer in three to five years?

LED technology became interesting for the East Frisian municipality of Uplengen (district of Leer), the moment structural engineer Andree Bullerjahn came across some information from Helecta. The company not only offers complete street lights with LED technology, but also so-called retrofit lamps. These LED-based lamps generally have the standard E27 or E40 base used in street lighting, which is suitable for replacing conventional mercury lamps (HQL) without any problem. The conversion merely entails bridging the energy-guzzling ballast and replacing the lamp. This means street lights no longer need to be converted at great cost, or even replaced by entirely new street lights. "That makes LED technology attractive from a cost point of view", Bullerjahn was quick to realise.

After successful testing early this year, Uplengen decided to procure 55 lamps, which were then in May, in the first instance, used to retrofit the street lighting in the cross-town link to state-of-the-art LED technology....then used in May in the first instance to retrofit the lighting... The 27-watt LED lamps have replaced the conventional 125-watt lamps, and this with almost identical light intensity. This investment alone saves more than 9 tons of CO2 annually. Due to energy savings and lower maintenance costs, this switch-over pays off for the 12,000-strong community within a mere 1.5 years, according to own calculations. An investment well worth it, considering the significantly higher service life of the luminaires.

"Of course, the appeal of retrofit lamps lies in the fact that municipalities can exploit the advantages of LED technology without being pinned down to this technology for decades because of major investments", says Helecta's General Manager Fabio Tinagli. Accordingly, his company has already fitted more than a thousand street lights with retrofit lamps this year. He feels that this is a very interesting, cost-effective and sound alternative for a large number of low to medium-output installations, compared to integrated LED luminaires, some of which are still very expensive today.

But there are also limits to the use of retrofit lamps, as Tinagli concedes. As things stand today, they can mainly be used for replacing 80 W mercury lamps, and in exceptional cases and depending on the luminaire type, 125 W mercury lamps at the most. Either way, that suffices for many types of luminaire, however, be it in roadside case luminaires or in mushroom-shaped luminaires in car parks, along paths or in parks.

Higher requirements also place different demands on good thermal management, which is important for the efficiency and service life of lamps. Thermal management in the relatively small retrofit lamps is a great deal more complicated than with an LED luminaire where the entire housing can be used as a heat sink in extreme cases. According to Tinagli, it is also important to consider that use of an integrated LED luminaire of the latest generation generally results in optimal light distribution, which means that compliance with DIN 13201 for street lighting is possible in terms of energy use, with higher efficiency. LED retrofit lamps, on the other hand, continue to use the original reflectors, which are present in existing luminaires. "When installing retrofits, the attainable light intensity and luminance therefore depends on the quality and condition of the existing luminaires", says Tinagli. He adds that particularly with old mushroom-shaped luminaire types, which in most cases do not have reflectors, excellent results have been achieved with LED retrofits.

This also applies to Tinagli's own municipality, Sittensen, where 200 street lights have been equipped with retrofit lamps this year. Thanks to LED technology, energy to the value of 7000 Euro and 33.4 tons of CO2 will in future be saved annually. "The good of today" instantly takes the load off not only the municipal fund, but the environment as well.