Street Lights
Let's talk about the humble street light - what is it? A street light in simple terms is a light mounted on a column that illuminates the street to aid in the safe movement of pedestrians and vehicular traffic.
How do street lights operate?
A typical street light will be powered by either a mains DNO connection or by a private Local Authority connection (learn more about how street lights are connected here).
They are switched on and off by a photocell that monitors light levels - we often see photocells set at 35 lux on and 18 lux off - this varies depending upon the Local Authority and their policies.
So in all a fairly simple operation... now comes the smart bit.
A Smart Street Light?
Instead of the light being controlled via a photocell as mentioned above, a smart street light will have a communication device that allows the user / owner (Authority) to communicate with an individual street light, allowing the operator to switch off, switch on, dim, monitor faults etc all from their desk.
What's the point?
This type of system has many benefits for the end user. A summary of these are listed below:
Monitoring of faults
Energy savings
Dynamic light system
Monitoring of faults - how is this helpful?
It was typical that authorities would scout the highway network at night looking for street lighting faults - this was often time consuming and also costly. You also had the issue that if you only scout an area twice a year, you could potentially have faults on the network for 6 months at a time.
With a smart street light connected to a central management system, the need for these night scouts is eliminated. The light will continually communicate with the central system and flag if there is a fault. These faults can then be batched and tackled in a more strategic approach.
It is also easier to monitor patterns - perhaps a particular street keeps having faults - this could be because the lights are old and their decline is rapidly accelerating. These can be programmed for a bulk lantern replacement, reducing the need to keep visiting the area and saving revenue costs.
Energy Savings?
How can we achieve energy savings with a smart street light?
We can use the control of each individual street light to dim the light at various point through the night. This is useful when we know that traffic during the night will be reduced and the lighting levels therefore can be tailored to suit the traffic flow requirements.
Each street light will monitor its exact usage and times on / off - assisting with the supply of an accurate energy bill. Prior to this, usage is often based on a generic swith on / switch off time depending upon your location the country.
It's also easier to implement or trial part night lighting schemes - lights can be switched off and on at set times when areas have minimal usage.
Dynamic Lighting System
All of the above provides a dynamic lighting system able to adapt and change to the needs of its user.
Operation Principles
Typically a street light head (the lantern) will have a node / antenna in place of the photocell. This antenna will connect with a nearby data collector, this collector then sends data via the web to a piece of software that can be used to control and monitor the lights.
There are other methods for this; however this is widely accepted a the typical method of a central management system.
Are all street lights capable of being 'Smart'?
In short.. no. The lanterns have to have a driver that is capable of relaying data via a common communication protocol, such as DALI. Most modern LED lanterns now come with DALI compatible drivers as standard.
Summary
In the right place and for the right price a smart street light can be extremely useful. It can save money in the long term; however initial capital costs can be high.
If implemented as part of wide scale lantern replacement project, the initial capital costs can be reduced and the long term savings improved.
Thanks for reading this simple look at what a smart street light is.
Peter