24 / 07 / 2016
Ambient temperatures in Australia can reach as much as 45°centigrade in the summer months and the effect of the thermal radiation due to direct sunlight on a luminaire could see the luminaire case temperature reach up to 75°C. What effect will this have on LED Street lights?
Consider firstly that the maximum case temperature [TC] of any LED driver should not exceed 85° centigrade and given that the starting point temperature of the luminaire after a day in the Australian sunshine could be close to 85°centigrade, this is far from an ideal situation for LED Street Lights. Whilst the luminaire case temperature will start to reduce as the sun sets, the mass of the luminaire will retain a large amount of heat and once the luminaire is switched on, the LED Junction Temperature and the Driver Case Temperature will start to increase.
Recognising this, BSSLED developed a specific sun shade cover to protect its range of LED Street Lights and LED Flood Lights. Not only does this create a sunshade to prevent direct sunlight contact with the LED Street Light but, due to the shape of the LED Street Light Heat Sink, the sun cover also provides a degree of passive forced air cooling.
After substantial testing comparing the difference between using a sun cover over the luminaire and allowing direct contact with the LED Street Light resulted in a differential of 28°C. Such temperature differences will extend the life of the Luminaire by a substantial amount of time.
The Osram OT165 Dim4 Driver within the LED Street Light has NTC as a standard feature (stands for Negative Temperature Co-efficient) to protect the electronics during severe heat conditions. It acts like a thermal ‘throttle’ by providing a thermal loop where if the temperature on the NTC (and module) exceeds certain values then the current will be reduced. (less current = less power = less heat). Our competitors don’t have this. It also features an astronomic clock and stepped dimming capability to allow the LED Street Light to operate at reduced output levels during the quieter periods of the night and offer further energy savings.
Endeavour Energy has taken the decision to conduct a long-term trial of our street light using the heat shade at their Unanderra and Parramatta sites in NSW replacing fittings that had only been in service for 3 years.