3.6 Cooling system
Excess heat affects directly short-term and long-term LED light source performance.
- Short-term: color shift and light output reduction
- Long-term: accelerated lumen depreciation and shortened lifetime
Natural (passive) and forced (active) cooling systems are commonly used for heat dissipation (Figure 3.6.1).
The term “passive” implies that energy-consuming mechanical components like pumps, jets, and fans are not used. Heat sinks are the most commonly used for LED luminaires. Generally, heat sink has finned metal encasement that conducts accumulated heat away from the LED light source. Since heat sink does not consume any additional energy, it is the most energy-efficient cooling system. However, LED light source with high power consumption requires large cooling area, i.e. complexly shaped heat sink, which adversely influences luminaire design.
The term “active” implies that cooling system contains energy consuming mechanical components like pumps, jets, and fans. Active cooling system is necessary for high lumen packages within small luminaires since it makes smaller structural shapes possible.
|a) Heat sink||b) Heat sink and fan|
Figure 3.6.1: a) Passive cooling, b) Active cooling.