Development of a guideline for designing economical and effective retrofit led street lighting system for Sri Lanka

Abstract

Nowadays most of the conventional type street lights are been converting to LEDs (Light Emitting Diodes). But there are no proper criteria or standardize methods to replace these conventional type street lamps to LEDs. Only energy saving aspect is garnering more attraction by the governments. But quality aspects like glare, uniformity ratios and color rendering should also be addressed. Otherwise it will not meet the safety and visibility needs of the road users which is the utmost objective of street light designing. The objective of this thesis is develop a guideline for designing economical and effective retrofit LED street lighting system for Sri Lanka. According to EN 13201-2:2015 ‘Road lighting - Part 2: Performance requirements standard, lighting classes were defined by a set of photometric requirements aiming at the visual needs of road users by considering the road categories, number of lanes and street light installation patters in Sri Lanka. Then minimum wattage/ lumen output, ideal light distribution type, luminaire mounting height, overhang and slope angle which should be used when replacing conventional type luminaires were decided for all road categories through a computer simulation process. It was noticed that pay-back period is long due to the cost of LED luminaire and arm modification. Also when we are trying to meet the standard luminance and illumination levels to a road which is having very poor lighting conditions, the cost becomes high. The prices of the LED luminaires are gradually decreasing and therefore lower price levels can be expected in the future and it will reduce these long payback periods. Though these projects have somewhat higher pay-back periods, they are still viable due to energy saving and maintenance cost saving compared to conventional type street lights. Hence when implementing these kinds of public projects investment cost should not be the only reason that should be considered. The safety of road users, upgrade the quality of life by promotion of business activities during the night hours should also be addressed.