Traditional LED street light designs focused primarily on lumen output while paying less attention to heat dissipation. In reality, LED lumen output is increasing rapidly; by 2009, mass-produced LEDs had already reached an efficacy of 100 lumens per watt, a figure that continues to rise. The corresponding theoretical framework for heat transfer is well-established, and the available mechanisms-conduction, convection, radiation, and phase-change heat transfer-are clearly defined. Consequently, the measures we can take to address heat transfer or dissipation are both identifiable and finite.
Common heat dissipation methods for LED street lights include the use of thermal conduction plates-typically 5mm-thick copper sheets that function as vapor chambers to distribute heat evenly-and the addition of heat sinks, though the latter often adds excessive weight. Weight is a critical factor in street light systems; given that these lights are often mounted at heights of nine meters, excessive weight increases safety risks, particularly during events like typhoons or earthquakes. Some domestic manufacturers have adopted a pioneering pin-fin heat dissipation technology. Pin-fin heat sinks offer significantly higher efficiency than traditional finned heat sinks, keeping LED junction temperatures more than 15°C lower than standard models; they also provide superior waterproofing compared to conventional extruded aluminum heat sinks, while offering improvements in weight and volume. Additionally, graphite heat sinks developed for high-power LED fixtures offer excellent thermal conductivity and dissipation performance.
Primary heat dissipation methods include natural convection, forced convection (using fans), and the use of heat pipes or loop heat pipes. Forced convection via fans results in complex systems with lower reliability, while heat pipes and loop heat pipes entail high costs. However, street lights benefit from characteristics conducive to natural convection-such as outdoor nighttime operation, heat dissipation surfaces located on the upper side, and relatively few constraints on physical dimensions-making natural convection the recommended choice whenever possible.
