Abstract
As energy efficiency becomes more and more important, light-emitting diodes (LEDs) are a promising alternative to
traditional lighting. Indeed, the energy efficiency of LEDs is still improving as their luminosity is modulated by current.
Moreover, for applications such as exterior lamp posts, their small size, directionality, colors and high frequency
response allow to combine them and provide design possibilities which are impossible with any other light source.
However, as any lamp, LEDs have a lumen depreciation which is a function of both current and temperature. Thus, to
take advantage of the full characteristics of LEDs, LED luminaire longevity strategies must be carefully studied and
planned, especially since the IES and CIE guidelines state clearly that the luminaire must maintain the rated
recommended light level until the end of the system's operating life. The recommended approach for LED luminaire
specification is therefore to use the end-of-life light level when evaluating the luminaire. Different power supply
strategies have been simulated to determine which one maximizes energy saving and lifetime. With these results, it
appears that active control can save at least 25% in energy, but the best strategy cannot be determined because of
uncertainties in luminosity degradation models.
