Smart Poles: A Thermal Management Challenge
It seems everyone is talking about smart cities these days, and with good reason. The prospect of an entire city working harmoniously via interconnected technology is truly exciting. From Toyota’s “Woven City”  to Toronto’s Quayside developed by Sidewalk Labs,  we’re now starting to get a glimpse of what the next generation of smart cities will bring. But, while automated cars and delivery by e-Palettes are eye-catching developments, one of the technologies that will underpin smart city infrastructure is perhaps being overlooked: smart poles.
Next time you’re walking around a city, count the number of poles you pass. They’re ubiquitous in our urban landscapes, but most only serve one function, typically lighting. Smart poles are a way of solving this inefficiency, turning single function poles into multi-tasking machines that create smarter and greener cities. They combine intelligent lighting technology with communication services, power and security features such as 4G/5G mobile signal, Wi-Fi, electric vehicle charging, surveillance cameras, IoT sensor data aggregation, mobile edge computing and more (Figure 1a).
Smart poles have the potential to improve parking and traffic management by providing real-time data, leading to a reduction in congestion and emissions. Additionally, they can also monitor air quality and detect street flooding, notifying officials rapidly if any problems occur. Undoubtedly, this technology could be transformative for our cities and urban areas. However, there are thermal challenges that designers and engineers will need to overcome if smart poles are to reach their full potential.
THERMAL MANAGEMENT OF SMART POLES
There’s a long list of technologies and features that can be housed within a smart pole, which will only continue to grow moving forward. And as poles are ever-present in our cities, there’s a need to conceal the active electronics for safety reasons, as well as keeping the environment aesthetically pleasing for citizens. This means that baseband units, power distribution, power rectification and edge computing equipment will all be located inside the pole.
A major consideration when installing equipment within a sealed environment is a cooling system that ensures appropriate operating conditions. The smart pole design may also need to comply with industry standards like GR-487 (electronic equipment cabinets) and IP-55 (ingress protection rating for enclosures)—all while attempting to maintain affordability. 6SigmaET modeling software  has helped companies develop solutions to these numerous thermal challenges.
One solution includes an air-to-air heat exchanger or thermal siphon, which maintains a sealed compartment and avoids the mixing of internal and external air loops. The system also includes a pair of DC powered cooling fans for the external air loop (bottom) and internal air loop (top) that ensure lower power consumption and intelligent fan speed control to reduce acoustic noise (Figure 1b).
The air from the outside is pulled through the inlet vent by the bottom fans, flows through the heat exchanger and exits through the exhaust vent (while extracting heat from the internal air loop) to create the external air loop. The cooled air in the internal air loop enters the front intake of the active electronics, and is drawn by the top fans as heated air from the rear of the active electronics into the heat exchanger.
BUILDING A MODEL
The geometry includes major cooling system components which direct air flow and transfers heat as well as heat dissipating components with assigned heat loads. The heat dissipating components included an MEC unit with a total of 300W, two BBU units with a combined heat load of 320W and a DC Power Supply with a load of 120W. This added up to a total heat load on the system of 740W.
The simulation was performed in 6SigmaET under the worst-case scenarios for temperature and solar loading as detailed in GR-487-CORE. Designs for baffles and vents were also included in the simulation, which show the supply air from the heat exchanger being directed toward the inlet of the active electronics—causing a “cold aisle” to form at the inlet. This allows the inlet temperature of the active components to be under 55°C— compliant with required standards.
Leveraging CAD models allows us to speed up the model build process and ensure that all the relevant geometrical details are accounted for (Figure 2). With advanced simulation tools that offer the ability to handle complex geometry, engineers are able to import the model in a matter of minutes and avoid spending hours attempting to simplify things to a level the software can handle.
BRIGHT FUTURE WITH SMART POLES
As we progress through this new decade, there’s no doubt that smart lighting solutions will play a key role in smart city strategy. Smart pole installations can make up the backbone of infrastructure that will provide services to benefit citizens, businesses and government. In Los Angeles  and Barcelona smart poles are already in use to enable mobile broadband connectivity. They can be used as WiFi hotspots, helping provide opportunities for remote working and communication throughout the city.
But, as the technology evolves and more features are added to service our connected cities, heat management will become increasingly complicated. Only by getting to grips with the thermal implications of having numerous technologies housed in one unit will smart poles be able to reach their maximum potential.
Thermal simulation solutions will be invaluable in this process. CFD modeling software, such as 6SigmaET, is well placed to handle the complex thermal challenges that smart city lighting systems will pose—helping ensure our future stays bright.
PUBLISHED IN CIRCUIT CELLAR MAGAZINE • JUNE 2020 #369 – Get a PDF of the issueSponsor this Article
Tom Gregory is a Product Manager at Future Facilities Ltd. He has been working at the company for five years and is responsible for marketing and supporting customers on the 6SigmaET side of the business. Founded in 2004, Future Facilities Ltd. is a global company that provides thermal simulation software and consultancy for the electronics and data-center industries. Driven by a team of the world’s leading thermal simulation engineers and scientists, Future Facilities launched its tool for the electronics design market, 6SigmaET, in 2009.