A 'smart city' is the integration of communications and physical assets into a cohesive network that provides a safer, more liveable and energy-efficient environment for the people who live there.
In a smart city, real-time information is provided to administrators through sensors and monitors deployed across the city. Depending on the design, the data collected can perform a variety of functions, such as monitoring weather and air quality, adjusting traffic signals to ease congestion, adjusting public transport timetables to meet changing demand, and deploying emergency responders more quickly.
Outdoor LED street lights are used as 'anchors' for the various sensors needed to integrate the data collected. This means that in addition to the right lens and housing design to direct the output light where it is needed, while minimising glare and skylight, the best outdoor LED lighting design also needs to include additional performance features to enable smart cities. Here are some things to consider.
Energy monitoring and metering - Because city administrators need data to assess the overall performance of outdoor lighting systems and to identify ways to improve system efficiency, lighting should include data collection and transmission capabilities. Relevant data including ambient light levels, turn-on times, energy consumption and status (e.g., full on, dimming levels) are transmitted at predetermined intervals to a network hub for collection and analysis.
Dimming and colour mixing - To realise the full energy saving potential of integrating outdoor street lighting into a smart city network, luminaires should be dimmable by scheduling and responding to changing environmental conditions. For example, to minimise energy use, lights may follow a pre-determined schedule.
In an emergency situation, administrators should have the ability to go beyond the schedule and switch the light from warm white (which has less impact on sky light and is usually preferred in residential areas) to cool white, thus providing better visual effect emergency responders' acuity.
Overvoltage protection - outdoor products have a significantly higher risk of overvoltage due to lightning and switching pulses and electrostatic discharge than indoor products. Mitigation can be achieved by including overvoltage protection both externally to the electronics and as part of the driver design.
Reliability - Temperature and temperature fluctuations, humidity, dust and water ingress, UV exposure and vibration are all causes of performance degradation or failure in outdoor luminaires. While the LED packages used in luminaires are most sensitive to high temperatures, system components such as drivers, optics and integrated sensors can be affected by other environmental factors. A comprehensive reliability and quality assurance programme, including robustness testing, can help mitigate these risks.
Maintainability and upgradability - GPS location, luminaire status, sensor status, input voltage and current, and internal temperature are the types of information that Smart City outdoor lighting products can provide to facilitate maintenance or component upgrades and minimise downtime. Designing for maintainability/upgradability that provides for easy part replacement or cleaning is important to the viability of the overall lighting system.
Interoperability - ANSI C137 The Lighting Systems Committee defines interoperability as "the ability of a system or system component to transmit, receive, interpret and/or respond to data and/or power and function in a defined manner". Although these terms are not equivalent, interoperability is often confused with the term 'compatibility'. Compatibility refers to the conformity of a device to a specific standard. Equipment that is compatible with the same standard should be interoperable for the functions defined under that standard. Confirming the interoperability of lighting system components (e.g. luminaires, sensors, and network hardware and software) reduces the risks associated with hardware and software obsolescence.
Security - Last but not least is the consideration of cyber security. This aspect of smart city design appears to be the least defined in terms of the roles and responsibilities of suppliers and buyers, and is therefore the most concerning. While not a luminaire design consideration per se, it is important to remember that any device on the network may be vulnerable to hacking.
There is no doubt that the implementation of smart cities will grow as part of the ongoing conversion of outdoor street lighting to LED technology. Find a smart city network in a town near you and let us know below if you are involved in designing or operating one.
Related led brands：Kingbright、Everlight
