You may have noticed a change in street lighting; replacement of round mercury vapour (1980 vintage) lights with linear T5 fluorescent lights. Why the change?
In 1999, Kevin Poulton of Lightlab International and Geoff Andrews of Genesis Now (then called Genesis Automation) teamed to produce a ground-breaking report into the Energy Saving Opportunities in Street-lighting, for the Sustainable Energy Development Authority (NSW) and Energy Efficiency Victoria.
Some of the key findings were
- the quality of illumination of both minor and major roads is much lower (i.e. it is hard to see) than could be achieved because of:
- the use of orange light instead of blue-white light,
- poor light distribution, and
- low illuminance, and
- energy consumption is high, considering the illumination provided.
There is a basic mismatch between the light colour produced by many street lights and the light colour which the human eye can use under typical street lighting vision conditions.
There is the potential to halve the energy used in street-lighting / public lighting.
The quality of street lighting can be significantly improved, and the energy consumption at least halved by a combination of:
- more efficient lamps (eg. metal halide and compact / T5 tubular fluorescent).
- more efficient lanterns (reflector design, less light loss in diffuser, more accurate light distribution without a refractor
- more efficient ballasts, especially electronic
- more accurate control of lighting times (electronic photo-switch rather than the existing cadmium sulphide cells, to reduce burning time by at least an hour per day (since tested and found to be correct)
- the capital cost premium of energy efficient street lighting is small and is justified by the very high return on the small premium,
- the cost of energy efficient street lighting equipment is very likely to fall as the production volumes increase.
- the cost of upgrading street lighting efficiency is comparatively low now because the majority of NSW and Victorian minor roads street lights are due for replacement now or within five years.
- the higher cost of more accurate, electronic photo-switches is justified by their longer life, with energy savings due to shorter lighting hours being a free benefit.
- mercury vapour is reputed to have low maintenance costs, but this reputation is largely a result of the practice of not replacing lamps even when light output has fallen excessively because of lamp fading.
The research by Genesis Now and LightLab International, along with the subsequent development of high efficiency street-lights (e.g. Pierlite T5 Greenstreet) paved the way for the replacement minor roads 80 watt mercury vapour lanterns with T5 fluorescent 2×14 and 2 x 24 watt lanterns. In 2010, many Victorian Councils started replacing 1980s street-lights with more modern, effective, efficient lanterns, and this process has accelerated with many councils (such as Boroondara) undertaking large scale replacements in 2011 and 2012.
The progress in realising the safety and energy benefits of replacing orange sodium vapour lights with blue-white light metal-halide, fluorescent and LED has been much slower, but this will change as the LEDs which are now producing over 200 lumens /watt in the laboratory find their way into commercial products.
The full report (pdf format): Energy Saving Opportunities in Street-lighting
For further information on energy efficient street-lighting and public lighting, please contact Genesis Now