ISAaR – Integrated simulation model for unit dispatch and expansion with regionalization

ISAaR low 2019

The model “ISAaR” is an energy system model, which formulates a mathematic description of the energy system using linear optimization. It includes the sectors electricity, district heating, gas, hydrogen, synthetic fuels and biomass. As well as the generators, storages and consumers relevant for each of these sectors. Additionally, the regional coupling of the electricity sectors is considered by portraying all relevant neighbouring countries within the European transmission network.


Gesamtmodellstruktur en

Figure 1: Elements of the energy system and their coupling


The model can be used to optimize different parameters of the system e.g. the total costs of the system, the emissions or the grid congestion. Within ISAaR the operational planning of plants as well as the planning of expansions for future parts like battery storages can be optimised. Furthermore, scenarios are developed forecasting boundary conditions like the development of the electrical and thermal load or an expansion corridor for renewable energy. These scenarios are the base for calculations forecasting future years to determine the optimized structure and dispatch of e.g. power plants, renewables, flexible consumers or batteries. With this, various strategic questions regarding the energy sector can be answered:

  • How are full load hours of different plant types going to develop in the future?
  • What is the expected price of electricity?
  • What role do batteries and sector coupling play?
  • How are emissions going to develop?
  • To what extent does the network expansion influence the revenue potentials for market participants?
  • How is Germany’s position in the export market changing?


Input Data

To answer these and other questions it is relevant that the quality of the input data comply with the requirements of the model, e.g. a high spatial and temporal resolution. By integrating the FfE regionalized energy system model (FREM[1]) these requirements can be met while a high flexibility regarding the dynamic development of different scenarios, used for the calculations, is ensured.

 Figure 2

Figure 2: FREM: The FREM displaying the FfE model of the extra-high voltage network



Linear programming acts as the mathematical base. Spatial resolution as well as the time frame and the considered region can be adjusted to answer specific research questions. Especially for planning expansions, an annual simulation in an hourly resolution is relevant. In addition, a detailed modeling of the behaviour of plants and storages is conducted. Beyond that, grid simulations (DC-OPF), CO2 emission analysis, simulations of the sector coupling and electricity price calculations can be performed using ISAaR. These boundary conditions require an increased computational effort, which is done by high-performance servers at the FfE.



A GUI “Graphical User Interface” is implemented to summarize calculation runs and to display and evaluate results. Due to the fact that the compilation of input scenarios is done modularly it allows extension by regions, technologies and sectors.

Figure 5

Figure 3: GUI for selecting scenarios in ISAar


The interface for evaluation is applicable to the considered problem and visualizes various parameters of the calculated results interactively. This enables a better understanding of the correlations of the modeled energy system.

Figure 4

Figure 4: Graphical interface for visualizing the calculated results


ISAaR was and will be developed further and applied in projects like MOS, MONA, C/Sells, Dynamis and Extremos. Due to the flexible forming of scenarios daily developments in energy economics can be considered in the model and their influence to the energy system be quantified.

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