**5. Conclusions**

The current review explores the application of blockchain technology in the rising concept of IoV demand response management, investigating in a systematic way the literature from the beginning of 2017 until the end of and 2021. We satisfied the goals of this review and answered the following research questions: (a) How does blockchain promote the P2P trading among EVs? (b) What is the current status on blockchain-based demand response programs and optimization models and which are the most common techniques for demand response management? and (c) What research work has been conducted regarding EV charging scheduling using blockchain? It is worth mentioning that we extracted knowledge following a systematic methodology based on Kitchenham's approach and present their findings around current perspectives and research efforts on blockchain-enabled IoV DR management. Although we found a vast number of papers using a thorough search procedure, some of them were judged irrelevant. Our findings are categorized in three parts related to: (a) P2P trading and managemen<sup>t</sup> in energy blockchain, (b) blockchain-based demand response programs and optimization models and (c) electric vehicle charging scheduling using blockchain. Finally, the current study concludes by providing the outcomes of the systematic literature review, highlighting our

main observations and opening research challenges. Additionally, we provided an analysis of the similarities and differences between the reviewed articles, showing, at the end, a set of limitations in the literature. This work goes beyond the currently available studies that focus on the blockchain application in the energy domain in general. Rather than that, the novelty of this study lies in the fact that it provides a systematic literature review in the area of DRM in IoV, based on blockchain technology. Therefore, it provides a thorough analysis of specific parts of the energy domain, emphasizing the above-mentioned perspectives and research efforts on blockchain-enabled IoV.

Our key takeaway from this study is that the disruption of blockchain in IoV is increasing at a fast pace. Currently, there are some studies that tackle the identified research challenges, although none tries to solve them holistically, as it should require a real-world scenario. Thus, we plan to extend the current review to propose more detailed solutions to overcome the identified research challenges. In that sense, we plan to further investigate the need of a unified blockchain framework that tackles all the identified challenges in a holistic way, considering secure energy trading, optimal charging scheduling and motivation towards the demand response management. It is also believed that further research is needed in the area of blockchain-enabled IoV to exploit its full potential and understand the limitations when applied in large-scale deployments.

**Author Contributions:** Conceptualization, methodology, validation, formal analysis, investigation, data curation, visualization, E.K.; writing—original draft preparation, E.K.; writing—review and editing, E.K. and M.T.; supervision, M.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by PARITY project funded by the European Union's Horizon 2020 Framework Program for Research and Innovation under gran<sup>t</sup> agreemen<sup>t</sup> no. 864319.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** This work was supported by the Institute for the Future (IFF), University of Nicosia, as part of the corresponding author's (E.K.) Ph.D. studies.

**Conflicts of Interest:** The authors declare no conflict of interest.
