Coal-fired power plants play a major role in large scale power generation by producing about 41% and 25% of the electricity in the world and in the EU, respectively. In the context of EU's climate and energy policy (EU Reference Scenario 2016) and with a view to decarbonizing the electricity sector, the share of non-programmable renewable energies will soar in future years both in and outside the EU. As result, the role of fossil-fuel plants including coal-fired plants is expected to evolve, leading to a paradigm shift for their design and operation, which will move from constant base-load operation to increasingly variable power production for the integration of intermittent renewable energy sources. In the present work, developed within the EU project sCO_2-Flex, the design and analysis of a coal-fired plant implementing a 100 MWei recompressed sCO_2 power cycle is assessed, with particular focus on the trade-off between system performance and flexibility. The effects of the different design assumptions on the overall components' sizing and system performance are investigated and a methodology to quantify the thermal inertia and the system flexibility based on the calculation of heat exchangers surfaces, volumes and masses (boiler tube walls and convective pass, recuperators and gas cooler heat rejection unit) is then presented. Finally, the cycle optimization is repeated with the aim to find the optimal trade-off between plant efficiency and thermal inertia, eventually providing a number of promising designs for next generation sCO_2 fossil fuel power plants.
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