LED luminaires are generally equipped with aluminium heatsinks due to the high thermal conductivity and low weight of the material. However, it is possible to minimise the use of aluminium and achieve improved heat transfer performance in larger luminaires by using plastic heatsinks embedded with an aluminium heat spreader. The used plastic, such as polycarbonate (PC), high density polyethylene (HDPE) or polypropylene copolymer (PPCO), may not be enough to cool the luminaire necessitating the use of a heat spreader under the heat source to increase heat dissipation. The use of injection moulded plastics opens up flexibility in terms of the geometric structure of the heatsinks, which can be easily optimised for convection heat transfer. Plastic is also approximately 40 % lighter than aluminium, which ensures better resistance to shock and vibration, in addition to having no antenna effect resulting in reduction of EMI. The result of these factors is increased heat transfer performance, weight reduction, cost saving and ease of manufacture.

Housing material Heat Spreader Total weight Numerical results, °C

IEC 60598-2-3*, °C Flux

kg TC Driver Housing TC TJ Driver Housing lm

PC Al6061 3.76 123.7 86.6 95.9 113.7 119.6 76.6 85.9 13,900

PC Al6061 2.90 125.5 83.1 97.3 115.5 121.4 73.1 87.3 13,900

HDPE Al6061 2.45 118.9 82.5 102.1 108.9 114.8 72.5 92.1 14,200

PPCO Al6061 2.37 114.9 81.2 102.6 103.9 109.8 71.2 92.6 14,300

Simulation results*10°C shall be deducted from the temperatures measured on the luminary in the test enclosure to allow for the effects of natural air movement which occur in the working environment of luminary.

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Hybrid Streetlight