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Light switching controls switch the light on and off. It is estimated that faults with photoelectric (PE) cells currently contribute around 50-130,000 tonnes of CO2e per year and costs of between $3 and $10 million dollars. They are hence one of the most important items to consider for improving street lighting energy efficiency. The main ways greenhouse savings can be achieved in this area are: - Using electronic photoelectric cells (which switch the lights on and off efficiently)
- Dimming (ie reducing) lighting levels during dusk, dawn or periods with low traffic or pedestrian activity
- Switching lights off during the middle of the night (e.g. midnight to 5am)
- For park lighting, installing lights that turn on temporarily when needed
 - A D2 PE cell used in minor road lights (left) and a NEMA PE cell used in major road lights (right).
Photoelectric (PE) cells, also known as photocells, are used throughout Australia to switch the light on and off by sensing the ambient light level. A PE cell is calibrated to turn lights on once the illumination level drops below a certain lux (ie sunset) and to switch off when light levels increase above a certain lux (ie sunrise). It is designed so that if the PE cell fails the light is left on. PE cells are typically replaced every eight years and can be used in both major and minor road lighting.
On almost all council roads and in new developments each light has its own photocell. In some cases, such as on a few arterial roads owned by VicRoads in Victoria, a group of lights may be controlled by a dedicated switch line wired into a PE cell on only one of the lights. Most new lighting schemes for declared main roads and all freeways (controlled and maintained by Vic Roads) are on a metered underground supply with a PE cell installed in the supply pillar. Two sizes of PE cells are used in Australia, each with a different method of connection: - The NEMA PE cell is used on the higher wattage main roads. It has a three curved pin to connect it. The large size of this cell means that it is not used in smaller lanterns. The NEMA cell is used widely throughout the world, including the USA. They can handle a maximum current of 10 amps.
- The D2 PE cell is used on minor (residential) roads. It looks like a fluorescent starter. D2 cells are used predominantly in Japan and Australia.The D2 PE cells are normally rated at 2 amps
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There are two main kinds of PE cells available in both sizes, with markedly differing reliability and performance: - Thermal (or electro-mechanical): This type often incorporates a cadmium sulphide sensor. It can drift by up to 6% per year away from their calibrated set point – and the drift is towards switching on earlier and switching off later. Thermal PE cells may fail before the scheduled eight year group replacement date, and have led to a significant day-burner (ie lights burning during the day) problem in Victoria.
- Electronic PE cells: These have negligible drift, are more reliable and consume lower standby power (current drawn during the daytime). Another advantage is they are capable of inverse (or negative) switching. This is switching on later at night and off earlier in the morning, reducing the time the light burns and saving energy. By contrast, thermal PE cells typically use the opposite, positive switching. Inverse switching is used in England and PE cell manufacturers now recommend it.
In NSW, distributors Country Energy and Integral Energy have switched to electronic D2-sized cells on minor roads. The benefits achieved by this include: - Time savings for crews which fix reported day-burners
- Energy savings from reduction in day burners
- Energy savings from reduced standby current draw
- Energy savings from eliminating drift
In Victoria, all the NEMA size PE cells have been switched over from the thermal type to the more reliable electronic type but this has not yet been done on minor roads.
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Banyule City Council, Victoria, 2005 to present (ongoing)
Banyule City Council and the Northern Alliance for Greenhouse Action developed and installed a photoelectric cell monitoring rig. The project sought to quantify energy and dollar savings from the choice of photoelectric cell technology. The tests were conducted under accredited laboratory conditions and in the field in locations within Banyule City Council. A report on the performance of photoelectric cells is now available.
 - PE cell test rig at Banyule Parks Depot
In most areas of Australia, “all night” lighting is now the norm, but this was not the case historically. In Western Australia street lighting was switched on at dusk and switched off at midnight or 1.15 am. In South Australia all street lighting was controlled by street lighting attendants up to the early 1970’s and in some areas they maintained and manually controlled the operating times at night, with switch off times being 1.00 am. In Victoria, however, street lights were switched on at dusk and off at dawn.
For information on switching off lights for Earth Hour see the Q&A Service.
Dimming lighting levels and switching lights off during certain parts of the night are lighting management strategies that can significantly reduce the amount of energy public lighting consumes. - Dimming is reducing light output during dusk, dawn or low traffic periods and/or pedestrian activity can be achieved using electronic ballasts, such as the Active Reactor or in the T5 flourescent, motion sensors, or specially designed PE cells, which have a built in function whereby they dim after 4 hours and then switch back to full lighting again towards the morning. Dimming can also be used to correct for “over-design” (that is, lamp design intended to compensate for lamp deterioration over time) and extend lamp life, particularly in the case of lamps with high lumen depreciation.
- Switching off lights during the middle of the night (e.g. midnight to 5am) is sometimes used in parks and gardens to discourage nighttime use and reduce vandalism. Switching off is achieved using timers.
- Dynamic dimming involves a lighting system that can operate at three levels of brightness, depending on the amount of traffic and weather conditions.
The capacity to dim high intensity discharge (HID) lamps is dependent on the lamp technology and can be limited to a fairly narrow range of light output:
- High pressure sodium (HPS) lamps can only be dimmed to approximately 80% light output
- Ceramic metal halide lamps will dim to approximately 50% light output
- Most quartz metal halide lamps are not suitable for dimming, although some American companies claim that they will
- Compact fluorescent (CFL) and T5 fluorescent lamps can be dimmed down to 10% and some as low as 1%.
Stepped ballasts can also enable variable control of lighting levels. The most common method is to use iron core wire wound ballast where the winding is tapped to give either full power e.g. 150W or some other fixed reduced output e.g. 100W. Typical arrangements for HPS lamps are 70W or 50W, 150W or 100W, 230W or 150W, 400W or 250W. It is worth noting that the percentage reduction in light output will be more than the percentage reduction in energy use since the under run lamp is generally less efficient.
Most of the work in this area has been done overseas, particularly in Europe (e.g. Norway, Nederlands, England) and Singapore (with reports that light levels can be safely reduced providing the contrast ratios are maintained). The Institution of Lighting Engineers (ILE) in the United Kingdom, released an interim advice note in 2006 suggesting: - Using photo electric cells to control lighting systems: Changing switching settings could reduce operating hours by 5 per cent (or 800 hours over their four-year operating period).
- Switching off or dimming: In rural locations where lighting is provided to enhance amenity rather than to reduce accidents or crime, it may be possible to switch lights off or dim them.
- Review street lighting levels when traffic levels change: When traffic levels change, i.e. when a by-pass is built, it may be possible to reduce or remove the lighting on the by-passed route.
Apart from some trials, these methods are not currently prevalent in Australia because most street lights are now individually controlled by PE cells that automatically operate each street light. It would be easier with a single point of supply and control for a group of lights, as happened in the past.
The current Australian road lighting standards include the provision of “multi level specification of lighting performance for selection according to the degree of activity,” and an example of this is shown in AS1158 Part 1.3 “Vehicular Traffic (Category V) Lighting.” This means it is possible to change lighting levels using dimming and traffic volume and speed sensors.
Before proceeding with either dimming or switching off, it is important to undergo community consultation to determine issues and expectations for light pollution reduction, safety and amenity, discouraging night use of certain areas, and so forth.
Dynamic Control Technologies, Adelaide City Council, South Australia, 2007/08
The Adelaide City Council demonstrated and conducted a performance analysis of retrofitting dynamic control technologies into two existing lighting installations. The aim was to optimise the standard of public lighting in response to changing vehicle, pedestrian and cyclist volumes in accordance with the Australian Standards (AS1158). The two retrofits were:
1. SE Park Lands Walk – pedestrian pathway lighting. Retrofit of existing efficient metal halide pathway lighting with lighting control equipment that allows lighting levels to be step adjusted according to pedestrian and cyclist numbers, which are monitored via sensory activated devices. The energy reductions are being metered and monitored remotely.
 - SE Park Lands Walk – pedestrian pathway lighting
2. North Terrace Boulevard – street and pedestrian lighting. Retrofit of existing efficient metal halide road and pedestrian lighting with lighting control equipment and other technologies that allow the road lighting levels to be dynamically and automatically step adjusted according to changing traffic volumes. The energy reductions will be metered and monitored and the performance of the system also are monitored remotely on Council’s web site.
 - North Terrace Boulevard – street and pedestrian lighting.
The trials were performed under the Australian Government’s Low Emission Technology and Abatement (LETA) initiative. For more information contact Phil Keane, Senior Engineer Lighting, Adelaide City Council. Ph: +61 (0)8 8203 7715 or Email: P.Keane@adelaidecitycouncil.com
 - The pole next to the street duplicates lighting from the road
Banyule City Council, Victoria, 2006
Banyule City Council consulted with local residents about whether they wanted lighting in a small park, with a new installation of playground equipment, walking path, seats and lighting proposed in 2006. Residents indicated they wanted the lights to go off at night after four hours to reduce light pollution into their houses after dark and discourage use of the park late at night.
Council installed a timer to turn the lights off four hours after the lights turned on (by the use of a photo-electric cell) and five poles with twin 14W T5 linear flourescent light fittings. This saved 2.5 tonnes of CO2-e and $188 per year in energy bills. Feedback from residents supported the timer turning off but wanted to see the lights go back on early in the morning so that they could walk their dogs. Future installations wil make use of a 24 hour timer to override the four hour timer at around 5am to turn the lights back on. For more information download the Sustainable Design and Maintenance Guidelines 2008 produced by NAGA.
 - The light has an array of solar cells on to top and 3 small lights at either end to give drivers direction. It is sturdy enough to allow traffic to run over it without damage.
Street light dimming, Italy
The City of Sassari, through the European Greenlight Programme, has installed a centralised dimming system to reduce energy consumption and lighting levels during periods of the night where traffic is lighter. The city signed a contract with the manufacturer and installer, which the equivalent of energy performance contracting, who financed the implementation and then kept a portion of the savings the project generated.
The project claims the following savings: - 1,855,385 kWh/year of electricity
- 30% reduction in electricity use
- €172,551 per year
- 3 year payback
- 33% internal rate of return
For more information on the project see the case study on the the European Greenlight Programme website.
Street light reduction trial on rural roads, Buckinghamshire County Council, UK, 2006-08
In August 2006, Buckinghamshire initiated a pilot project to test whether existing street lights could be replaced by intelligent road studs (solar powered) and electro luminescent signs. The pilot project took place at the Nash Lee Roundabout on the Wendoveer Bypass. The expected benefits included reduced costs, energy savings, decreased light pollution and reduced casualties (based on the theory that a driver is more aware of an oncoming headlight in a completely dark environment than in a lit environment).
Following completion of the pilot project, Buckinghamshire announced a three-year street lighting reduction trial on rural and semi-rural roads. Phase 1 began in April 2007, with 287 lights switched off and improved signage and white lining, luminescent signs, and intelligent road studs installed before the street lights. This saved an estimated £15,000 per year, and 90 tonnes of CO2e. Phase 2 commenced in April 2008 and involves 1,700 lights going out, saving an estimated £100,000 per year. The council says this will translate to a 10% saving on total annual greenhouse gas emissions – around 590 tonnes of carbon dioxide.
For more information about Phase 1 of the scheme, see Reducing the County's carbon footprint or Eco-conscious County plans to trial streetlight switch offs. For preliminary results relating to road safety, see County council defends lights out scheme. For more information about Phase 2 of the scheme, see Street lights: The big switch-off.
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Street lighting management systems, Calderdale Council, UK, 2008
Calderdale Council and other local authorities in the UK are piloting a new street lighting management system, called Vizion, which claims to reduce energy consumption by up to 40% per lighting point.
Switching off neon, Spain, 2006
Madrid's mayor has signed a law ordering that all neon advertising lights must be switched off within a year. The new law will affect between 120,000 and 200,000 neon signs across Madrid. The prohibition will save electricity and make the city more aesthetically pleasant. The move was welcomed by environmentalists, however, small businesses and independent shopkeepers may file a legal challenge against the new law. Businesses flouting the new law would face fines of up to €3000 ($A5130). (Reference: "Mayor gives neon the flick", The Age, Anthony Ham, 26 June 2006.
Switching off in the early hours, City of Dresden, Germany, 2002
The City of Dresden has switched off every second street lamp in areas where it is technically practicable since 2002. In peripheral areas, where the distance between lamps is already significant, no lamps are switched off. About 30% of lamps in Dresden are affected. The lamps are switched off from midnight to 6am in the summer and from 11pm-5am in the winter. Initially, the public was concerned that it would make the city less safe, but as there was no indication that the crime rate had increased, the concerns died down. For more information, contact Landeshauptstadt Dresden,Geschäftsbereich Stadtentwicklung via ++49/351/4884241 or email.
Dynamic Dimming, Lancashire County Council, United Kingdom, 2002
A Yorkshire dimming pilot project replaced lanterns along a section of the M65 in Lancashire with a dimmable lighting system controlled by traffic flow. There were three lighting levels based on traffic flow (>3000 vehicles per hr = 100 per cent lighting, 3000-1500 vehicles per hr = 75 per cent lighting, and <1500 vehicles per hr = 50 per cent lighting). The system incorporated 'soft' switching so that light variation was gradually adjusted to the lower level without sudden changes.
The lighting system's savings of £14,000 per annum were achieved with the traffic flow profile in place, and it is estimated that savings of around 145 tonnes of CO2e per year have been achieved. In addition to reducing energy consumption, greenhouse gas emissions and light pollution, other resources have also been conserved due to longer lamp life. In addition, it is likely that general road safety was improved by reducing ocular stress.
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