Councils upgrading their streetlights to LED face a big opportunity to direct their lighting in a more efficient and environmentally friendly way. Steve Hare from HBW Lighting explains.
It is inevitable that street lighting across most of the world is going to be upgraded to LED over the next 10 years or so. Therefore, as an industry we have a real chance, and also a real responsibility for that matter, to improve this network for the better.
Energy efficiency is of course one of the main drivers for the inevitable overhaul, but we can do better than just reducing energy consumption. We can take this opportunity to address other problems such as sky glow, light intrusion, reliability and aesthetics to name a few.
Here are five ways to get out of the mindset that has been shaped by ‘how we’ve always done it’ and look at the problem afresh.
1. Save the night sky
All luminaires being installed could be ‘dark sky’ friendly. And installing a full cut off luminaire that emits zero light above the horizontal does not mean you have to compromise on efficiency or compliance. It is quite possible to achieve P5 at 75m pole spacings using a full cut off luminaire. There is no need to use a refractive bowl, it only throws excess light into windows and into the atmosphere.
2. Stop spilling light
Be cautious with LED aeroscreen luminaires. Aeroscreen luminaires are traditionally used where spill light into the atmosphere and into properties needs to be restricted. With HID this was relatively effective, but flat glass won’t improve the control of spill light with LEDs. Because the light source is so small, a flat visor does not ensure the photometric centre of the light source is suitably recessed to reduce this spill light.
3. Re-think tilt angles
How about we start deviating from the notion that every single street lighting luminaire must be installed with a 5 degrees tilt angle? This only contributes to the spill of light into the atmosphere and into property boundaries. Some of the standard brackets used even have an inherent 10 degree uplift or more, which doesn’t help. It’s normal to have some upward tilt angle in the bracket so aesthetically the luminaire doesn’t droop, but in doing so either the spigot should be at zero degrees or the luminaire should offer the facility to be installed horizontally on an angled spigot.
By utilising a luminaire with a good optic, there is no need to use a tilt angle to achieve the required pole spacings. This is what we should be striving for, simply because we can.
4. Make luminaires safer to maintain
By steering away from huge outreach arms that hang over the carriageway and opting for short brackets that suspend the luminaire behind the kerb line, we can improve safety for the maintenance and installation teams. This change can also bring down maintenance costs because fewer lanes need to be closed, and it reduces the impact on traffic.
5. Find a better way to measure glare
Excessive glare is the problem I hear most complaints about from those who have installed LED lighting. The current systems in use to measure glare just aren’t as effective with LED as they were for the light sources they were designed for.
Threshold increment was a reasonably good measure of disability glare for large tubular lamps, but with LED it fails to deliver the same results on the road as the calculation may suggest. There is continuing research on this subject, but a more appropriate system for measuring glare is a long way off being recognised here on this continent.
In the absence of a good system for determining the actual glare of an installation, it is essential that the optics of luminaires are scrutinised to assess how glare is minimised, or not, through the design of the optic.
Remember, lighting is there for a purpose and it is the residents who have to live with it and the drivers who have to drive under it.
As an industry we have kicked some energy saving goals, but it’s not cigar time. Until local standards really start to address these issues and really assist the adoption of good quality lighting, it will not materialise on the streets. It’s time we stop doing what we’ve always done and start pushing for good quality outdoor lighting.