Lifetime projection of lamps and luminaires based on high power LEDs (2009-)
Due to the banning of incandescent lamps, general lighting are now days based on light emitting diodes (LED). This technology is relatively new, so the lifetime of LED lamps is not well known. Generally, the light output of LED lamps changes rather fast when taken into use and some LED sources are known to even increase their light output during the first 1000 hours. The expected lifetimes are long, tens of thousands of hours. Thus, ageing the lamps throughout their expected lifetimes to predict their behavior is extremely time consuming. Methods to predict lifetime behavior in significantly shorter time frames are needed.
The junction temperature of LEDs is one of the main factors that affects the lifetime of luminaires based on high power LEDs. Due to the high temperature dependence of the lifetime of LEDs, aging of LEDs can be accelerated by increasing the operating temperature of the LEDs. Metrology Research Institute has aged different types of light-emitting diodes and luminaires at different temperatures and stress levels to project their expected lifetime. The aging study includes aging of LED chips, domestic LED lamps, organic LEDs, and smart LED street light luminaires.
As the lifetime of LEDs is one of the main interests in LED based lighting, aging studies have been carried out in several international projects.
Contact persons: Hans Baumgartner, Janne Askola, and Petri Kärhä
 H. Baumgartner, D. Renoux, P. Kärhä, T. Poikonen, T. Pulli, and E. Ikonen, “Natural and accelerated aging of LED lamps,” Lighting Res. Technol. 48, 930-942 (2016).
 A. Vaskuri, P. Kärhä, H. Baumgartner, O. Kantamaa, T. Pulli, T. Poikonen, and E. Ikonen, "Relationships between junction temperature, electroluminescence spectrum, and ageing of light-emitting diodes," Metrologia 55, S86–S95 (2018).