In 2004, New York City launched an international design competition to create a new streetlight for the City of New York. The LED streetlight was the award-winning design from the competition and provides a model for the widespread lighting of streets, sidewalks and parks within the City. In 2009, the City of Rome decided for LED street lighting. From 2010, some areas of Rome will be lit with LED light. The goal is 15 thousand new light poles by 2015. The mayor of Rome declared that he starts working on energy saving, emission reduction and public transport, in order to achieve a better city. LEDs have been taking to the streets since the 1990s, when cities throughout the U.S. and Europe began replacing incandescent-based traffic lights with more efficient LED systems. For sure, in the last years we saw a growing interest for LEDs and LED technology improved, since the Eighties, in term of efficiency, life time and luminous intensity. Besides that, LED producers and companies are investing money and time in LED technology research and because of this heavy investment, they are promoting LEDs to public administrations, cities and to private sectors. Companies are more and more involved in the production, distribution and advertising of LED products. The new legislation about the dismiss of incandescent lamps, furthermore, is one more step toward the complete triumph of LEDs. The result of all these implications is that, nowadays, there are many different myths and misunderstandings about LED, and it is difficult to consider and compare LED performances. Not technical magazines and newspapers help creating fake myths and confusion about this subject. It is difficult also to make people thinking to right or not right applications for LED. The result is that you feel “old” and “not updated on new technologies” when you refuse to use them. We believe that LED will improve more and more in the next years and that LED technology is incredible for many applications, like colour light applications, signalling, underwater, museum cases and much more… But we also believe that we need to consider that LED efficiency, sometimes, is not the reason, at the moment, to use LEDs. Nowadays cities are convinced that LED street lighting can improve quality of city life and electricity bills, but there are few products on the market that can be good enough to be really energy saving, comparing LEDs to MH, for example. Besides that, it is important to know that majority of the LED street lighting are in reality for pedestrian areas or not vehicular streets, because the luminous flux or the optic is not adequate to reach a lighting level comparable to other systems or conform to law prescription (UNI 12464). Here we would like to underline some of the basic notions about LED. Basic, but not so diffuse. First of all, the efficiency of LED systems depends on different factor, beginning from the colour of light: if the LED is cool white is more efficient than a warm white LED. This is important to underline, because it is something easy to forget during a project. Speaking about coloured LED, each colour has a different luminous flux. Secondly, the operating temperature can influenced a lot the LED efficiency. This is because higher operating temperature can increase the Tj temperature (junction temperature inside LED chip). On some catalogue you can find, for example, “operating temperature: between -20°/ +35°”. Obviously there are thousands of places in the world where it is easy to reach 35°! Last important point is that we need to check carefully and compare of a same lighting fittings power consumption and luminous intensity. Often you can find LED poles with a power consumption around 150W or 200W… It is a lot compared to a MH pole!!! In conclusion, no doubt that LED technology is innovative and it will be better in the next years. It is the best technology for a lot of applications, as a matter of fact, but be careful to say that it is the most energy efficient lighting technology today, because this is really a false myth.
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