LEDs could slash street light energy usage by 97%

There are almost 300 million streetlights installed around the world today and this is expected to grow to over 330 million by 2025. Generally, conventional street lights use technology that is more efficient than for lights we use in our homes, so you’d expect that the switch to LED street lights would not achieve the energy saving results that LED’s will give us in our homes. But this assumption is incorrect, because of the different requirements for illuminating our streets for driving and nighttime safety.

Today, most of the streetlights in Australia use mercury vapour bulbs; these consume about 80 watts and have an efficiency of about 30 lumens per watt. As reported in Reneweconomy recently Warrnambool, in Victoria’s south west, will trial LED street lights in a project funded by the CEFC, while other councils pursue projects to replace their conventional bulbs with soon to be out-dated fluorescent tubes.

With its simple approach to LED street lighting, Warrnambool will achieve energy savings of 50 per cent compared with their existing lights. If, however, they were to use new technology, developed by lighting company CREE and set to be available in 2015, which achieves 150 lumens per watt, Warrnambool would achieve savings of 66 per cent.

Savings like this should be particularly appealing to local councils in NSW, where the state government-owned network operator, Essential Energy, has proposed to hike up the costs of public lighting maintenance starting July 2015, claiming it has been under-recovering for the service in the past.

The proposed changes, submitted to the Australian Energy Regulator last week, would reportedly lead to huge increases in public lighting costs for some NSW cities, such as 102 per cent ($34,303) for Liverpool Plains between this financial year and next, and 65 per cent ($62,202) for Narrabri.

But what is really interesting, in the world of LED streetlights, is if we fast forward to 2020, where much bigger savings will be achieved. In the Argentinian capital of Buenos Aires, for example, the entire city is getting retrofitted with LED lights a world first that will be repeated time and time again until over 95 per cent of street light sales will be LEDs by 2023.

97% reductions in street lighting by 2020

Streetlights will achieve higher efficiency than domestic or commercial lamps, emitting high quality light at 400 lumens per watt, in commercially available units, by the end of the decade. This will occur using a combination of Red, Blue and Green LEDs, whereas the approach for domestic and commercial lights has been to work solely with blue LEDs and make them appear very close to white by adding a layer of phosphorous.

The Red Blue, Green approach is very suited to street lighting as the colour rendering requirements for street lighting (quality of light) are not the same as what we’d expect to live and work under for lighting our houses and commercial spaces. At 400 lumens per watt, a future LED Street light will use one-thirteenth the electricity (6.15W) of a conventional mercury vapour (80W) fixture.

In addition to this intrinsic energy saving future streetlight’s will have inbuilt ambient light sensors which will reduce lighting output in the early evening and early morning as well as when there is a lot of background light such as on clear nights when the moon is out, avoiding over illumination and the costs associated with providing light when it’s not required.

In addition street lights will have predictive forward illumination with auto-dimming which detects when a person or vehicle is present causing multiple lights in front and behind the person/vehicle to come on full power and stay on for a short period after the person or vehicle has passed.

The lights then auto-dim and the fixtures are ready for the next person or vehicle that comes into the coverage area of the lighting array. This “smart lighting” feature saves a further 50% on energy requirements. An entire road system can run at a low level dimmed point (when no one is present) and automatically ramp up to full output several lighting poles in advance of oncoming traffic, lighting up entire roundabouts or intersections as vehicles approach, without any human intervention, quietly dimming back to the low standby ready level after the traffic has moved on.

The combination of the most efficient LED street lights with ambient light sensors and smart lighting will achieve greater than 97% reduction in electricity requirements for new LED streetlighting by 2020. If all the world’s lights were replaced it would be the equivalent of 25,000MW saved (including grid losses and PowerStation internal consumption) or about the same as Australia’s entire overnight electricity demand being completely shut down every night of the year.

LED street lighting already delivers far superior colour rendering compared with traditional street lights and improves safety by making it much easier for drivers to recognise hazards and pedestrians. And although they suffer some degradation, LED lights don’t progressively degrade to the poor performance levels of mercury vapour lights, either.

Furthermore, with LED lighting the public can maintain a sense of security while reducing light pollution, which affects some people’s ability to sleep – not to mention the efforts of stargazers, who are currently hindered in practicing their hobby in and around cities.

Developers in the US are already choosing Solar powered LED street lights (Solar + LiOn Battery + Photovoltaic) because it is cheaper than trenching and cabling up conventional light poles in new developments with underground power.

The future is bright, with more opportunities to light dark spaces brought about by rapid LED research development and commercialisation, giving a higher sense of security as well as lighting the way for those in developing countries who have not yet had the opportunity to experience illuminated roads and streets.

There is a serious opportunity for Australia to play a part in these developments, and a forward looking “bright” government would be fostering research opportunities in our public, private and academic institutions.