The necessary transformation of energy systems towards net zero greenhouse gas emissions provides a plethora of new research challenges. New interconnections between different energy sectors, such as power, heat and mobility, increase the system's complexity. In this context, the digitalisation towards cyber-physical energy systems (CPES) alleviates change, and equally affects technical, social, and societal topics, as well as the mode of research in the CPES research community. Research efforts towards CPES heavily rely on modelling and (co-)simulation-based approaches. Tracking of models together with all data creates a complex software and data management challenge, which needs to be addressed in each research project. To this end, nfdi4energy covers the whole research and transfer cycle of projects in energy system research ranging from (1) identifying relevant competences for a project; (2) defining relevant scenarios and experimental setup; (3) integrating models and data; coupling tools and laboratories; (4) extracting results, facilitating public consultation; to (5) identifying research challenges for follow-up activities. We define the following key objectives: (1) Establish common research community services for FAIR data, models, and processes in energy system research and motivate its use in the community. (2) Allow traceability, reproducibility, and transparency of results for the scientific community as well as for the society, improving the overall FAIRness. (3) Enable and motivate the involvement of society for the identification and solution of relevant research questions. (4) Promote better collaboration and knowledge transfer between scientific research institutes and business partners via FAIR research data management. (5) Simplify identification, integration, and coordination of simulation-based models. (6) Integrate the provided services for energy system research within the wider NFDI ecosystem to improve cross-domain collaboration. To fulfil these objectives, nfdi4energy concentrates on five key services to provide a non-discriminatory access to digital research objects: (1) Competence to help to navigate the interdisciplinary research field, (2) Best Practices to get information about successful conduct of research including research data management, (3) Registry to find suitable data and software, (4) Simulation to couple existing simulations and, therefore, reuse software artefacts, and (5) Transparency to involve more stakeholders in all research stages. With these services, nfdi4energy aims to develop and provide an open and FAIR research ecosystem in the energy system domain containing a large share of common workflows from data gathering to the inclusion into research software, together with data publications for researchers spanning from single component development (like battery storage systems or other new smart grid equipment) up to system-of-systems research (based on mathematical or analytical models).