**1. Introduction**

The energy sector is facing a new paradigm shift following the large-scale integration of renewable energy sources (RES) [1]. The significant use of fossil resources is one of the major concerns of today's society. Climate changes, environmental impacts, and the scarcity of resources have led to the need for RES. RES reduce greenhouse gas emission while contributing to an increase in life quality and sustainable development [2]. The inclusion of RES is a highly complex task. The demand and supply need to be balanced due to the unpredictable behavior of RES. This influences not only the electricity system but also heating and cooling systems due to the considerable linkage between subdomains.

In order to solve these problems, multiple stakeholders need to work together and provide solutions. Models of such solutions are essential to explore the interactions between consumption, production, and transportation as well as economic, environmental and technical phenomena. Multi-agent systems (MAS) can contribute to explore and develop such solutions since MAS can simulate how multiple

stakeholders work, interact, and influence each other. The MAS simulations make it possible to simulate systems which consist of agents with different or conflicting objectives.

Agents often collaborate towards a specific goal and need to communicate and share results. Different languages and vocabularies are domain-specific, and often cause problems for the agents in a system. It requires a common language to ensure that messages are interpreted correctly between agents [3]. Therefore, ontology can be applied to establish effective communication between agents. Ontology can specify terms that are used for communication within a specific context and enable agents to make declarations or ask queries that are understood by all other agents in the system [4]. It is an important tool for the development of an intelligent multi-agent energy system, e.g., for the knowledge sharing and knowledge reuse [5].

As more applications of multi-agent systems in the energy domain for advanced functions, the interoperability challenge raises due to an increasing requirement for data and information exchange between systems. Meanwhile, the energy system is strongly connected with other domains. Therefore, the application of ontology in multi-agent systems needs to be emphasized and a systematic approach for the application needs to be developed.

Although some review papers have investigated agent-based modeling and tools for the electricity domain (e.g., [6]), very few studies have investigated the MAS design and the applications of ontology in MAS for the energy domain. Moreover, many studies focus on specific subdomains and how to solve one specific problem. Hence, investigation and analysis of more complex systems and problems, integration of subdomains, including different agents and ontologies, is needed. Meanwhile, it is important to highlight the relevant literature and map the key concepts underpinning the research area [7]. The scoping review can provide the means that identify, characterize, and summarise existing literature regarding the state of research activities. Moreover, the review result can identify gaps in the literature.

This paper conducts a scoping review to investigate the existing studies on the application of ontologies in the MAS for the energy domain. Based on the results of the literature analysis, this paper proposes a recommendation list for the ontology-driven MAS development for the energy domain. This recommendation aims to address certain aspects that are missing in the literature or need more emphasis in future work.

The paper is organized as follows: Section 2 describes the methodology and the research process. Section 3 presents the literature analysis results, and Section 4 discusses the findings followed by Section 5 that concludes. The conclusion section also states the recommendation for future work and the limitations of this study.
