Street lighting infrastructure overview
The main elements of a street lighting system
A street lamp is made out of a lamp socket which mechanically supports electrical connections and allows the lamp to be conveniently replaced. The ignitor provides the high-striking voltage needed to ignite a streetlamp. The ballast (or transformer) reduces the voltage and regulates the electric current to produce a steady light output. The capacitor is used to stabilize voltage and power flow.
Compared to traditional lamps, smart street lamps have the capability to be remotely powered on, off or dimmed by means of controllers. These can be integrated inside the lamp from the production stage or mounted on the lamp.
The main purpose of intelligent street lighting is to better light up the roads, pavements and parking spaces to guarantee citizens’ security. To ensure visual safety to drivers and pedestrians, smart lighting needs to meet specific values of luminance, illuminance or dimness, uniformity, and glare according to the road type. HIDs and LEDs are currently the most popular lights used to grant high-quality, efficient lighting.
HID lamps are still commonly used around the world for lighting up vast areas. Even though they have a lower implementation cost and are less costly to replace than LED lights, HIDs are increasingly being replaced by LEDs and for good reason. HID lights have a warm-up period of 20 seconds until reaching full power, can emit up to 70% less visible light after only 10,000 hours of being in use, and about 30% of the energy produced is infrared which is entirely wasted energy. LEDs, on the other hand, have an extremely long lifespan (new LEDs last over 100,000 hours), reduce energy costs by up to 60%, don’t have a warm-up period, and pay for themselves in 6 to 18 months.
For centuries, lighting poles have been used to place street lighting sources and have evolved together with lighting technologies. Later on, they were used to support traffic lights or communication infrastructure. But the recent technology developments promise to bring it to the pole position of Smart City initiatives.
Lighting poles have two characteristics that make them essential to smart city development: they are omnipresent and they are powered. Especially with smart lamp-level control, the street lighting grids are continuously under power (even during the day – a problem with legacy street lighting). Therefore, there is a large number of sensors and IoT devices that can be mounted on and supplied from the street lighting poles, using any available communication and laying the grounds for Smart City synergies.
The traditional method for switching a cluster of streetlights is via a device in a control cabinet triggered on a timer or by a photocell. When modernising existing street lighting infrastructure, control cabinets are an essential element. They must be able to support energy-saving technologies such as LED lights and smart lighting management systems. For example, modern control cabinets should be able to pass the light switching impulses from a modern lighting control center on to the individual street lighting devices, or link the street lighting system to the smart sensors/ actuators, when necessary.