Performance optimization and entropy-TOPSIS evaluation of a thermochemical solar thermal power generation system based on packed bed reactor exothermic characteristics

• It revealed the exothermic reaction kinetics of modified diatomaceous earth . • Reactor showed optimal exothermic performance at an operating temperature of 650 K. • Intermediate air channels in packed bed reactor reduced reaction time by 28.57%. • System achieved 56.86% energy and 49.06% exergy efficiency under optimal conditions. • Entropy-TOPSIS revealed economics (31.50%) as primary factor in system assessment. Solar thermal power generation technology has enormous potential in global low-carbon energy transition, but its large-scale development is still constrained by some challenges such as solar intermittency and system stability. This study focuses on diatomite-modified calcium-based materials, revealing that diatomite modification transforms the exothermic reaction mechanism from an A3 model to a D2 model, which significantly reduces activation energy by 8.69 % and increases the pre-exponential factor by 18.19 %. The exothermic process in packed bed reactors was thoroughly investigated, illustrating the evolution patterns of temperature field, reaction extent, and pressure field. An innovative design of incorporating intermediate air pathways was proposed, and it reduced the reaction time by 28.57 %. A novel thermochemical solar thermal power generation (TSTPG) system was established to systematically examine its performance from the perspective of reactor heat release characteristics. Through a comprehensive 4E (energy, exergy, economy, and environment) analysis framework, the mechanism of reactor parameter optimization on system energy efficiency improvement, exergy loss reduction, CO 2 emission reduction, and economic benefits was systematically investigated. A multi-dimensional evaluation methodology based on entropy-TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) was proposed to incorporate the power generation capacity, energy efficiency, exergy efficiency, annual total cost, and carbon emission reduction. Results demonstrate that the newly established system achieved impressive energy and exergy efficiencies of 56.86 % and 49.06 % respectively under optimal conditions such as 650 K, along with power generation of 48.31 MWh and a total annual cost of 4.11 m$/year, showing promising prospects for engineering applications.