Optimal Capacity Adjustments in Electricity Market Models – An Iterative Approach Based on Operational Margins and the Relevant Supply Stack

The modelling of energy systems often has to balance two aspects. High level of detail, e.g. technical constraints on the one hand and analysis of long-term system optimization on the other. When focusing on one of the two aspects, models can be solved in a reasonable time. In order to combine both aspects in one model we use a problem-specific iterative approach. A detailed system model is linked to iterative adjustments of investments. This is based on a subgradient method of optimization. The approach can be described as a detailed dispatch model with adjustments towards an investment model. The results show that the algorithm is quite efficient for a stylized model. For a larger model, performance is not yet sufficient for day-to-day practical use, but several elements for further improvement are identified.