The basis for the analyses is the integrated energy system model FINE-NESTOR (National Energy System Model with Sector Coupling) which, with its diverse interactions, depicts the national energy supply system across sectors in a technically-accurate manner. The FINE-NESTOR model was designed and developed at the IEK-3. In order to meet the diverse issues arising in the context of the energy transition, the model is being continually further developed. It is a partial equilibrium model and features an optimization approach by minimizing the monetary expenditure for the conversion of the energy supply (system costs), which makes it possible to identify cost-optimal transformation strategies. A major advantage of the integrated energy system model is that the consistency of the calculated scenarios is always guaranteed. The model is currently based on a myopic concept. This enables transformation paths to be calculated in five-year steps. Due to the great importance of the highly volatile energy supply in the future and the foreseeable storage requirements, the model has an hourly resolution. With further methodological developments, such as procedures for time series aggregation (Link to group Leander), it will be possible to reduce the considerable computation times currently necessary. The model is characterized in particular by a detailed mapping of relevant industrial processes. This also includes a representation of industrial raw material demand (not energetic consumption), as well as many possibilities for the recycling of secondary raw materials.

The thematic fields of application are as follows:

• National greenhouse gas reduction strategies
• Greenhouse gas neutrality
• Importance of hydrogen in the future energy system
• Impact of recycling strategies in the context of greenhouse gas mitigation
• Defossilization strategies for German industry
• Reduction and substitution of energetic raw material demand
• Sectoral energy savings
• Analysis of national wind and PV potentials
• Techno-economic assessment of individual technologies (e.g., storage) in an overall system context

The coupling of the FINE-NESTOR model with other models of the IEK-3 opens up various possibilities for deeper as well as spatially-resolved analyses. For instance, in order to be able to consider interactions with the European electricity market, there is the possibility of integration with the EUROPOWER model. Further coupling possibilities exist with the models GLAES/RESKit, which enable detailed area potential analysis and so site-specific analyses of wind power or PV plants. A special feature is coupling with a global hydrogen distribution model, which can be used to generate quantity/price relations for global hydrogen and PtL imports, which are in turn important input variables for the national NESTOR model. Coupling with the FINE-Crossing model permits a spatially-resolved analysis of the FINE-NESTOR model results. This makes it possible, for example, to perform detailed infrastructure analyses (e.g., hydrogen pipeline routes)