Analysis on energy efficiency and optimality of LED and photovoltaic based street lighting system

Abstract

This study evaluates the optimality and energy efficiency of Light Emitting Diode (LED) and Photovoltaic based street lighting systems as a part of energy conservation. This evaluation is based on the detailed review carried out through a country wide street lamp survey. Since LEDs are becoming increasingly competitive due to their rapidly increasing efficiencies and decreasing cost, this research assessed the LED fixtures which have the capability of achieving 50% to 70% energy saving potential compared to the existing established technologies based street lamps available in the country. As a case study, illumination levels were examined at two neighbouring traffic junctions in the Capital City, from Bambalapitiya junction to Kollupitiya junction. Two kinds of measurements were taken and average luminance levels were analysed for all measured points in the traffic lanes. It was found that same lighting performance could be achieved by replacing 250W HPS (High Pressure Sodium) by 150W HPS and further it was verified the same results while having 62% energy saving by replacing 250WHPS lamps with 111W LED through a simulation with Lighting RealityTM software. This change would easily meet the minimum recommended level of 7.5 Lux and average luminance of 0.5 cd/m2 as per British Standards. Even though solar powered street lighting systems need high capital outlay, it will be one of the most appropriate energy solutions for a country like Sri Lanka. Incentive program development by the government may further encourage LED street lamp and solar powered system development adoptions. This study also recommends that any such incentive program should include performance standards that consider warranty, efficacy and other important criteria as the next steps.