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 neighboring 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 Reality TM software. This change would easily meet the minimum recommended level of 7.5 Lux and average luminance of 0.5 cd/m 2 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. ENGINEER, Vol. 48, No.01, pp. 11-20, 2015
Highlights
Street lighting is an essential public service that provides a safer environment at night time to motorists as well as pedestrians
Energy consumption for street lighting in year 2009 was 108 GWh as per statistics digest of Ceylon Electricity Board (CEB) and this shows the percentage increase of street lamp installation could be 30% annually [15]
Most probably the newly installed street lamps may be consisting with inefficient technologies; the energy loss will be increased annually and these should be minimized to obtain an energy efficient street lighting system
Summary
Street lighting is an essential public service that provides a safer environment at night time to motorists as well as pedestrians. Proper use of street lighting as an operative tool provides economic and social benefits to the public. The electrical energy consumption of street lighting constitutes an important part of total energy consumption. Saving energy in street lamps is important for total energy savings. Reductions in energy consumption through the installation of modern lighting equipment, control and management practices have a direct impact on the level of greenhouse gas emissions from street lighting. Reductions in greenhouse gas emissions are directly related to reductions in energy consumption; the potential savings are of the same order and vice versa
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