What is a Smart Street Light?

What is a Smart Street Light?

Smart street light refers to a network-connected street light. Each street light is equipped with an outdoor lamp controller, internet of things device, and/ or sensors. A smart street light automatically regulates the light intensity based on sunset/ sunrise times, daily schedule, human presence, traffic, and/ or weather situation. Thereby saving considerable energy and lowering the maintenance costs. Smart street lights also capture and transmit data in near real-time to a central management system, so that street light operator gets:

• Total control over each luminaire,
• Insight into the state of public lighting, and
• Access to a range of lighting applications and services.

How do Smart Street Lights Work?

A smart street light automatically regulates the light intensity of the connected street light based on a smart algorithm and inputs from external sensors. Such inputs include local sunset/ sunrise times, daily light level schedule, pre-programmed light scene, human presence, traffic, and/ or weather situation.

To achieve this, a conventional or LED street light is typically equipped with an outdoor lamp controller (OLC). The main purpose of this controller is to send and receive commands to/ from the connected street light. Such commands include switching, dimming, scheduling, and maintenance messages.

The outdoor lamp controller (OLC) also acts as a bridge between the connected street light and a central management system (web-based software, CMS). The OLC collects and shares luminaire data with the central management system.

Today, street light controllers are usually available in four different forms:

• Nema Controller – These type of OLC are equipped with Nema 5-pin or Nema 7-pin receptacle that are compatible with ANSI C136.41 standard.
• Zhaga Controller – These type of OLC are equipped with a simpler 4-pin Zhaga (book 18) socket, and often compatible with Zhaga D4i standard.
• Luminaire-mount controller – These type of OLC is installed inside the street light luminaire. Here the OLC is often placed together with the LED driver and connected via analog/ DALI dimming wires. Such an approach is specifically suitable when a luminaire is not equipped with a Nema or Zhaga socket.
• Pole-mount controller – These type of OLC is installed on the street pole. Here the dimming wires from the OLC and the LED Driver are connected at the bottom of the luminaire (at the junction box). This approach is often suitable when a luminaire is not equipped with a Nema or Zhaga socket, nor the luminaire has space to house the controller internally. Externally pole mounted controller delivers value-for-money when a street pole has multiple luminaire (say, 2, 3 or 4 luminaires on one pole). These multiple luminaires can be controlled by a single OLC.

Nema and Zhaga based controllers are clearly more popular and widely used by cities. This is because they support easy plug-and-play installation on a street light fixture. Increasing number of new smart lighting projects are adopting Zhaga D4i standard.

What are the most common communication technologies used by a Smart Street Light?

An outdoor street lamp controller (OLC) uses different communication technologies to connect with a central light management platform (CMS)/ a command-and-control center (CCC). Each communication mode has its strengths and weaknesses. A City should choose an appropriate communication technology based on its local situation.

• RF Mesh – Radio Frequency Mesh is one of the most common communication methods – typically suitable for small networks (below 5000 smart street lights). It is a widely used solution for motion sensor-based smart streetlights. RF Mesh uses a Zigbee-type wireless mesh network (2.4 GHz/ 868 MHz). Controllers typically report to a Gateway, which in turn, connects to CMS.
• LoRaWAN – a low-power, wide-area wireless network wherein LoRa Gateway(s) can manage 1000s of connected internet-of-things devices. It is suitable for certain smart city applications such as metering. However, due to security, data limitation, and single-point-of-failure reasons, LoRaWAN is not recommended for the smart street lighting application.
• UNB – similar to LoRaWAN, ultra narrowband based devices connect to centralized UNB Gateway(s). UNB is a proprietary communication technology offered by specific vendors. Lack of international standards, security breaches, and single-point-of-failure remain key concerns for cities that consider using UNB for public critical infrastructure.
• PLC – powerline communication uses existing power cables for data communication between the controller (OLC) and the Gateway (segment controller). It was a popular technology in the early 2000. However, it is an outdated technology often lacking replacement parts and lack improvements in security standards.
• Cellular IoT – Cellular IoT has become the most common solution for large citywide smart street light deployments (more than 5000 smart street lights). Here an outdoor lamp controller (OLC) is equipped with a SIM card/ eSIM. OLC connects directly to the local telecom tower (without a physical Gateway). Supported by the 3GPP mobile broadband global partnership and highest security standard, today billions of devices (including mobile phones, ATMs, and traffic lights) use cellular IoT.

What type of Sensors can be connected to Smart Street Light?

Smart street lights are often equipped with one or more sensors. These sensors form part of the outdoor lamp controller (OLC) or are connected external to OLC. Different types of street light sensors and their functions are listed below:

• Photocell / Ambient light sensor – adjusts street lights illumination (including on and off switching) based on the surrounding environment’s light level. SkySwitch is one such example for Nema and Zhaga based photocells.
• Motion sensor – adapts light intensity based on human presence detection. Brighter lights upon detection and lower light level when no one is around. Thereby combining public safety with excellent savings. CitySense is one of the most widely used street light motion sensors.
• Acoustic sensor – detects noise, such as a loud scream and traffic noise. And can also detect gunshots to alert the police.
• Accelerometer – detects pole tilt or pole hit – to raise alarm.
• Seismic sensor – monitors earthquakes/ ground motions to help emergency personnel estimate the damage and take safety measures well in advance.
• Parking lot sensor – identifies vacant parking spaces.

Benefits of Smart Street Lighting

Smart street lights are a cost-effective, practical, and sustainable way to minimize energy usage and expenses. Smart street lights also improve the quality of life and citizen safety in the community by alerting the lighting operator in time for a prompt repair where necessary.

The notable benefits of smart street lights include:

• 60% to 80% energy savings over-and-above the savings achieved through conversion to LED streetlights. See for example, the savings achieved by Smart City Dortmund (Germany).
• Full control over public lighting infrastructure.
• Turn reactive maintenance to predictive maintenance through smart alarms and advance notifications. Thereby reducing considerable operating costs.
• Significant improvements in public safety by offering high-quality illumination and helping the operator keep the lighting infrastructure up-to-date. Motion sensor street lights further improve public safety perception.
• Cut light pollution, and protect local flora and fauna as well as preserve dark skies – by dimming the street lights during off-peak hours or through motion sensors.
• Help address climate change by cutting energy waste.
• Create a foundation for the Smart City by providing interconnection with different IoT systems. See for example, the implementation at the city of Helmond (the Netherlands).
• All the above-mentioned benefits, yield from day one after the installation.

Considering the benefits of smart street lights, an increasing number of cities around the globe are adopting LED streetlights with smart controllers. The marginal increase in investment for smart controllers guarantees that the city is future-ready when deciding on LED street lights.