Developing an ontology for co-simulation scenarios of energy systems

The transition to sustainable energy systems requires innovative approaches for the seamless integration of diverse energy technologies, systems, and infrastructures. To meet this challenge, co-simulation has become a crucial tool, allowing for the analysis of complex multi-domain energy systems by combining multiple specialized simulation models. This approach provides a better understanding of how different components interact with each other. By offering greater flexibility than traditional monolithic simulation methods and enabling the reuse of existing models, co-simulation is a key strategy for investigating interconnected energy systems. The lack of standardized frameworks and semantics for defining and managing models and scenarios limits the effective use of co-simulation. In NFDI4Energy, we develop the semantic framework for co-simulations in energy systems in form of a co-simulation scenario ontology. This ontology provides a common base for defining co-simulation scenarios, enabling better interoperability and facilitating the integration of models. It will serve as a foundation for creating standardized scenario definitions that allow researchers to easily compare and reproduce results. It will also be integrated with other services in the NFDI4Energy project, like the Simulation-as-a-Service (SimaaS) hub, the Framework Factsheets, Model Factsheets, and Scenario Bundles on the Open Energy Platform. We use the Linked Open Terms (LOT) approach for the development of the ontology, which involves defining use cases and requirements. After we analyzed existing simulation ontologies and did a literature review we could not identify any existing works that describe co-simulation scenarios, but only ontologies which represent other aspects of simulation and might be partially reused or integrated into the new scenario ontology. Additionally, we considered scenario definitions of the three co-simulation frameworks mosaik, DaceDS, and VILLASframework, which are used as examples in NFDI4Energy. The resulting ontology will focus on general concepts for co-simulation scenarios that can be extended with additional modules for specific frameworks to describe detailed individual concepts and map them to the general concepts. Thus, we aim to make co-simulation frameworks better interoperable but also consider the individual implementations. Additionally, domain-specific aspects such as grid topologies will be integrated. The scenario ontology will be integrated into the Open Energy Ontology (OEO), which was found as most relevant ontology in our state-of-the-art analysis and will also be used and extended within the NFDI4Energy consortium to annotate data and link between different services. After finalizing the requirement specification of the co-simulation scenario ontology, we conceptualized the core classes, properties, and relationships necessary to represent key elements. The definition and integration into the OEO are currently in progress. We aim to demonstrate how the ontology can support the application of co-simulation in energy system analysis and contribute to making co-simulation scenarios more FAIR by applying it in the use cases of NFDI4Energy.