How to model the cycling ability of thermal units in power systems

For thermal units in power systems, the importance of quick load changes increases along with the share of volatile renewable feed-in. An adequate representation of the cycling abilities of thermal units is therefore important in energy system modeling. Five different model techniques used in the literature to describe the cycling ability of thermal generation units are applied in the optimizing energy system model PERSEUS-NET-TS. The model calculates the dispatch of German generation units while restrictions of the transmission grid are considered. Differences in the cumulated dispatch of coal, lignite, and gas combined-cycle units in Germany due to the different modeling techniques are analyzed based on the PERSEUS-NET-TS results as well as the resulting dispatch of two exemplary single generation units. While the cumulated dispatch for Germany does not show any major differences for coal and lignite units, the cumulated dispatch of gas units differs slightly depending on the approach. Moreover, the dispatch of individual generation units may differ significantly. Even though the real commissioning strategies are not publicly known, it could be identified that the mostly applied modeling approaches based on technical restrictions increase computing time unnecessarily and that cost based approaches reduce on/off cycling more.