In a Solid State Luminaire (SSL), the lower the operating temperature of the LED, the longer it maintains its high output. A quality LED maintains its output longer at the same temperature. The ability of the LED to do this is verified in LM-80 testing, a standard test method used by every reputable LED manufacturer. Without LM-80 data, there is no way to determine how long the LED will last at any temperature.
Thermal management is a function of load and capacity. The load is the measurable rate at which heat-energy is being introduced, and the capacity is the rate at which it can be exchanged (in our case, with the ambient air). As a result, longevity relies upon a combination of the LED (LM-80 results), the power (watts), and the thermal capacity of the fixture.
In solid state lighting performance, thermal capacity is a function of two things:
- thermal conductivity, or the ability of the fixture to conduct the heat-energy from the LED junction to the outer surface; and
- thermal convection, or the ability of the fixture to exchange the heat-energy with the ambient air.