Thermal Simulation of a Smart Pole Housing Active Electronics

The past decade saw the development of IoT devices and the rise of smart homes – where all household appliances, gadgets and communication devices are wirelessly controlled, and data is made accessible on the go. With the advent of 5G technology and Edge computing, we have entered the era of smart cities. What many don’t know, however, is that one of the building blocks for setting up this smart city infrastructure is a technology called the Smart Pole.

What is a Smart Pole?

A Smart Pole is typically a street light pole that combines intelligent lighting technology with communication, power and security features, such as 4G/5G cell service, Wi-Fi, electric vehicle charging, surveillance cameras, IoT sensor data aggregation, mobile edge computing (MEC), etc. 

Smart Pole example
Figure 1. A Smart Pole example

Meeting Thermal Requirements

The ever-growing list of features housed within a smart pole, along with the demand for street side aesthetics, results in the need to conceal active electronics—like Baseband units (BBUs), power distribution, power rectification and edge compute equipment—inside the pole. A major consideration when installing equipment within a sealed environment is the cooling system that ensures appropriate operating conditions. In addition to local air temperature control, 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) while maintaining affordability.

Active Electronics inside the Smart Pole
Figure 2. The Active Electronics inside the Smart Pole

SRC-Design Solutions was able to develop a thermal solution using 6SigmaET. The solution includes an air-to-air Heat Exchanger/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. 

Air flow loops with the active electronics housing
Figure 3. Air flow loops with the active electronics housing

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.

Model Build Process

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 MEC unit with a total of 300W, two BBU units with a total heat load of 320W and DC Power Supply with a load of 120W. The total heat load on the system is 740W. The simulation was performed in 6SigmaET under the worst-case scenarios for temperature and solar loading as detailed in GR-487-CORE.

6SigmaET model with temperature plot
Figure 4. 6SigmaET model with temperature plot

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 under 55°C –compliant with required standards. This particular case was simulated with 12 million grid cells.

Thermal Modeling using 6SigmaET

Leveraging CAD models allowed us to speed up the model build process and ensure that all the relevant geometrical details were accounted for. With 6SigmaET’s ability to handle complex geometry, we were able to import the model in a matter of minutes and avoid spending hours simplifying the model. The ability to import complex geometry not only brings in every detail of the CAD model, but also reduces the model build time. 

The future of the modern city infrastructure is already here. With technologies like smart poles and the latest communication equipment being developed and installed, we need novel ideas to tackle design and thermal challenges. 6SigmaET is the tool to handle complex thermal problems of the future providing an easy model build coupled with a fast and accurate solution.

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