High Pressure Sodium

• Snapshot of HPS technology
• Australian trials and demonstrations
• International trials and case studies
• Suppliers

High pressure sodium (HPS) lamps provide excellent luminous (light output) efficiency, long life, low maintenance and are relatively inexpensive. They are the most common light used for major road lighting in Australia and are also used extensively world wide.

HPS lamps, particularly low wattage HPS, do have some drawbacks. The main one is the yellow colour of the light produced and the poor colour rendition. The yellow light of the lamp is absorbed and not reflected by green foliage, contributing to a low brightness of the surrounding area. This is exacerbated by the decreased sensitivity of our eyes to yellow light – we see better in bluish-white light, not yellow light.

To deal with the poorer colour rendition, HPS lamps on minor road lighting are now regarded as 25% less bright than they used to be under the Australian Standards (ie de-rated by 0.75 for Categories P4 and P5 under the AS/NZS 1158.3.1:2005). This translates into shorter pole/lantern spacings to increase the minimum light level. The de-rating does not apply to HPS in major road lighting, because the greatly increased light levels involved compensate for the effect of the yellow light on the eye.

Another issue is the ballasts on low wattage HPS lamps (35 to 100 watts) are relatively energy-intensive; iron-core ballasts on low wattage lamps can consume up to 20 per cent of the total wattage applied to the lamp. Lastly, as HPS lamps age, their power requirements increase; when new, a 50W HPS lamp may consume 45 watts, while at the end of its life, it may consume 60 or 65 watts.

“Twin arc” HPS lamps are a relatively new development, and further increase the reliability and life of HPS lamps, which some manufacturers now claim can extend out to 50,000 hours. A twin arc lamp has a second arc path. As only one of the two arc paths operates at any time, the second arc path acts as a backup, taking over as the first arc light output decreases until it’s output decreases and the first arc takes over again.The longer life of twin arc lamps means less frequent batch replacements of lamps.

As the higher wattage HPS is an established technology for major roads, Australian trials have focused on the 50W HPS as a substitute for the 80W mercury vapour on minor roads. Where innovation and trials have occurred for higher wattage HPS is in the use of Active Reactor technology.

Coffs Harbour City Council, New South Wales, 2000-05
Coffs Harbour successfully retrofitted its entire public lighting stock with the Sylvania 50W HPS in 2004.

Project Update (June 2007): Coffs Harbour City Council is now saving around $100,000 on electricity costs per annum, outperforming original estimates which anticipated annual savings of $70,000 over a 10-year period. In addition, the retrofit has cut its energy consumption from public lighting by 30% and reduced its greenhouse emissions by about 650 tonnes each year. For more information, see New South Wales.

NAGA-AGL Sustainable Public Lighting Initiative Demonstration Project, Victoria, 2004–07
The Northern Alliance for Greenhouse Action (NAGA) facilitated a demonstration project in which 116 energy efficient street lamps were installed in place of 80W mercury vapour  (MV) in the Cities of Banyule, Moreland, Darebin, Whittlesea, Hume and Maribyrnong. The project monitored 80 T5 fluorescents, 31 high pressure sodium and 5 compact fluorescents to determine their efficiency in the Victorian context.

Update September 2007: A report on this project has now been released, which recommends that the T5 be used as a standard direct replacement for the 80W MV. For more information see the report prepared by Kevin Poulton and Ray Simms.

City of Ballarat, Victoria, 2004–05
This demonstration project, undertaken as part of the Sustainable Public Lighting Initiative, installed 23 50W HPS lights at the MacArthur Park housing development at Miners Rest.
 
Whittlesea City Council and VicUrban, Victoria, 2004–05
VicUrban installed 63 HPS (50 watt) and 6 CFL (42 watt) to provide street and laneway lighting in the first three stages of the Aurora development in Epping North. This trial was undertaken as part of the Sustainable Public Lighting Initiative.
 
Wyndham City Council and Pioneer Homes Australia, Victoria, 2004–05
This demonstration project, located at The Greens development at Point Cook, involved the installation of 30 HPS (50 watt) on minor roads. The project was undertaken as part of the Sustainable Public Lighting Initiative.

City of Salisbury, South Australia, 2002
26 Sylvania Nostalgia B2001 luminaires and 26 50 watt high pressure sodium lamps were tested. The trial was later accelerated, and involved testing three additional technologies. For more information, see the progress brief published by the City of Salisbury.

Salisbury City Council, South Australia
Salisbury City Council is conducting a 2.5 year trial involving four energy efficient streetlights: 32W compact fluorescent, 35W metal halide, 70 metal halide and 70 watt high pressure sodium. Council will monitor and compare their running costs, efficiency, light output and residents’ satisfaction. The lights will analysed for their ability to replace existing 80W Mercury Vapour lights, or even the 50W high pressure sodiums (which are becoming a less attractive option because of colour and spacing issues).

As of May 2008, no readings had yet been taken, but there had been one resident comment about the CFLs. This trial follows an earlier trial by Council in 2002 (see above) that tested the 50 watt high pressure sodium. The cost of the trial has been minimised for council as the company supplying the technologies is also conducting its own research into the lights. For more information, contact Salisbury City Council Traffic Engineering Officer, Ken Potter, on (08) 8406 8281.

Yogyakarta, Indonesia, 2004
Since the introduction of the Streetlights Management Scheme in 2001, Yogyakarta has implemented actions to calculate power usage, introduced new systems for payment, replaced around 775 mercury vapour bulbs with high pressure sodium, and installed 400 electric sub-meters to measure actual street light energy use. Yojyakarta has since started installing a power meter for every street light pole.

By December 2003, the city estimated that it had achieved a 23% reduction in costs. As of June 2004, it estimated that it had avoided about 2,051 tonnes of eCO2 from the streetlight management scheme alone. For more information, see the detailed case study compiled by ICLEI South East Asia.

Kapiti Coast District Council, New Zealand, 2008
The Council is 65% through a public lighting upgrade from twin 20’s to high pressure sodium which began in 2001. The Council is currently undertaking a review of Category P public lighting with the objective of reducing carbon emissions. The review includes options for lighting technology; control gear; reducing light pollution; energy supply & charges. For more information, contact Jemma Sharman, Climate Change Advisor on +61 (0)4 296 4700.

The main suppliers of (high & low wattage) HPS lamps in Australia are Sylvania, Osram and Phillips. Sylvania supplies the Urban 50W High Pressure Sodium (HPS) luminaire and lamp.