## 5 Conclusions  
This paper experimentally evaluated electric fields inside a compact car for several realistic wireless communication scenarios and explored the possibility of using these EMFs in energy-harvesting applications. For each scenario, more than 1600 measurements of E-fields in an urban area in two cases (when the car was in an open space without a direct line of sight to a base station antenna, and when the car was in underground parking) were performed. The research results show that, inside the car, the maximum E-field emitted during GSM ongoing voice calls and 5G wireless data transmission was more than 20 V/m. During LTE data transmission, the maximum E-field was about 10 V/m. The obtained mean values in different sub-scenarios varied between 0.27 V/m and 1.39 V/m. Moreover, the electric field that propagated in the car during voice calls or data transmission exhibited slight variations depending on the day of the week. These results prove the hypothesis that the EMFs emitted by wireless devices in a car can be used as a new energy source to power battery-less wearable or IoT devices, and they can be used to design energy-harvesting systems with maximum conversion efficiency. The results from this study provide the following:  
* A comprehensive dataset of more than 1600 measurements of E-fields in different microenvironments and wireless communication scenarios;
* A comparative analysis of the E-field measurements in different wireless communication scenarios (during GSM voice calls, LTE and 5G data transmission, etc. ), providing reliable knowledge on EMFs. The results will be used for future assessments of human exposure;
* Variations in E-fields over time and microenvironments for different communication scenarios, providing useful information for the design process of an RF energy system. A possible future research direction that can properly complete these initial findings regarding the potential use of EMFs inside a vehicle can be a quantitative type of research in the form of a field survey based on a questionnaire designed to assess the perceptions and attitudes of people regarding the willingness to use such RF harvesting technology to power devices inside the vehicle. RF energy harvesting holds immense potential for the future development of the IoT and WSNs. It addresses the power requirements and operational challenges of these devices, enabling sustainable, autonomous and scalable deployments. With RF energy harvesting, the IoT and WSNs can operate efficiently, reduce maintenance costs, and unlock new opportunities for applications in diverse sectors, contributing to the growth and advancement of the IoT ecosystem. Thus, the impact on a global scale can be a very important one, as we are all witnessing right now the proliferation of new models to integrate AI technology and other state-of-the-art machine learning aspects into the everyday use and consumption of products and services. Conceptualization, N.T.A., G.L.A., D.A.G. and I.P.G. ; methodology, N.T.A., G.L.A., D.A.G. and I.P.G. ; software, N.T.A. and G.L.A. ; validation, N.T.A. and G.L.A. ; formal analysis, N.T.A., G.L.A., D.A.G. and I.P.G. ; investigation, N.T.A. and G.L.A. ; resources, N.T.A. and G.L.A. ; data curation, N.T.A., G.L.A., D.A.G. and I.P.G. ; writing--original draft preparation, G.L.A. ; writing--review and editing, N.T.A., D.A.G. and I.P.G. ; visualization, N.T.A., G.L.A., D.A.G. and I.P.G. ; supervision, N.T.A., G.L.A., D.A.G. and I.P.G. ; project administration, G.L.A. ; funding acquisition, G.L.A. and N.T.A. All authors have read and agreed to the published version of the manuscript.