An advanced thermal storage integration framework for flexibilization of thermal power units: feasibility analysis and multi-objective optimization

Coal-fired power plants (CFPPs) serve as flexible power sources capable of actively regulating renewable energy capacity within the grid, representing a key technology for achieving future low-carbon energy systems. Flexibilization for CFPPs still face the dual challenges of high investment costs and low efficiency. To address these challenges, this paper proposes for the first time the integration of packed bed latent thermal energy storage (PBLTES) system into flexibilization of CFPPs. Combined with high-temperature heat pump thermal storage (HTPTES) system, this approach innovatively constructs a highly efficient and economical transient integrated solution. Based on parametric studies of key parameters and data generated from mechanism-based models, an interpretable multi-objective optimization framework is developed. Results indicate that the integrated CFPPs reduce the power load by 21.42% in terms of adopting a combined multi-heat source approach that integrates the extraction steam with HTPTES. In addition, the nonlinear antagonism exists among thermodynamic, economic, and environmental performance metrics among different parameters. The values of the equivalent round-trip efficiency (ηe), levelized cost of electricity (LCOE), and annual CO2 emission reduction (ACER) of the optimal integrated system, which are determined using the TOPSIS method, are 71.39%, 99.83 $/MWh, and 44,771.27 t, respectively. This work providing valuable insights into the selection and optimization of flexible retrofitting solutions for CFPPs.