# Safe and Sustainable Design of Composite Smart Poles for Wireless Technologies
## 4 Discussion  
### Design Process and Interconnections of Results  
The FEA combined with the experimental campaign resulted in the GFRP wall thickness of 5 mm (load-carrying layers). For a six-meter pole and GFRP's density of 1670 kg/m\({}^{3}\), the mass of the entire pole would be 28.8-29.6 kg (from circular to diamond-shaped cross-section, respectively). For a similar steel pole, the mass would increase 380% (steel pole mass 153 kg). Because 5 GPs are more deformation (sway) critical than strength critical, a steel pole could be made six times thinner in thickness in theory. If a practical minimum wall thickness would be two millimeters to prevent instability, the steel pole continue to be 60% heavier (i.e., GFRP leads to a minimum of 37% weight saving). The significantly lower mass of the GFRP pole directly makes its handling easier and lowers transportation emissions for a global 5 GP usage.  
Because of the bending moment and the following stress concentrations at the root of the 5 GP shaft, the wall thickness could be increased at the pole root. Alternatively, the pole root in turn would be an ideal location for an additional, fully or partly load-carrying structure, i.e., a wide shaft tube. A wide housing at the root would lower the mechanical stresses and embody a neat space for standard power and data connection modules. A root housing could also accommodate devices, e.g., an EV charge station for some urban 5 GP sites. Due to the linearity and strength of composite materials,  
Figure 13: CFD analysis of a 3D printed heat exchanger and the cooling strategy: (**a**) simulated heat exchanger (outside) surface temperature (color range represents \(\Delta T=10\)\({}^{\circ}\)C) when water flows into and out from a 3D printed heat exchanger via embedded rows of channels; (**b**) the highest allowed inlet temperature as a function of mass flow rate to maintain below 65 \({}^{\circ}\)C surface temperatures per cooling strategy.  
there are clearly more options, e.g., large maintenance doors, as was given by the FEA at the cutout corners in this study. At the top of the pole, cutouts are also necessary for radio radomes. Large cutouts for signal windows (covered by a non-reinforced polymer) make the GFRP pole even lighter. Any other than composite/polymer design could be an obstacle for receiving (indoor/outood) devices [26] and to fit the 5 GP for individual customer needs. The attenuation measurements indicated a 90-175% increase of signal attenuation due to a surface treatment on radome materials--this means that as large cutouts and as thin as possible radomes are needed in 5 GPs, even when using GFRP for the pole shaft.  
The CFD analysis of the heat management presented that liquid cooling is an efficient technology for pole-integrated radios. Liquid cooling requires piping between individual radios as well as in and out from the pole. The added pipe lines would require further space inside the pole; the power and data cabling with various connector appliances define the necessary pole diameter in general. Any larger diameter will lead to a heavier pole--again emphasizing the benefits of GFRP.  
The results of this study showed that the interaction between functionality (i.e., large cutouts allowing large radomes and maintenance doors), heat management for integrated devices and mechanical design with a minimum material usage and safe structure prefer a composite design. Due to the higher manufacturing costs of composite structures compared to traditional steels, the markets of 5 GPs will define the amount of device integration in the future.