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.