Jin, YanYanJinMakhova, EvgeniaEvgeniaMakhovaSpeerforck, ArneArneSpeerforck2026-05-122026-05-122026-04-29Applied Thermal Engineering 300: 131220 (2026)https://hdl.handle.net/11420/63031Packed-bed sensible heat storage (SHS) is important for balancing energy supply and demand over time. To improve the efficiency of a packed-bed SHS system through second law analysis (SLA), we developed multidimensional macroscopic entropy and exergy transport equations for fluid flow and heat transfer in porous media. These equations enable us to identify where and how much exergy is destroyed. Using a packed-bed SHS system developed at the PROMES-CNRS laboratory as a test case, we demonstrated how to apply SLA to optimize an SHS system. Our analysis revealed that, in addition to exit and heat leakage losses at tank surfaces, thermal and solid conduction losses inside the tank significantly contribute to total loss in the studied SHS system. These internal losses occur close to the thermocline. However, their slower transport causes a delay in their emergence. The SLA suggests an optimal tank aspect ratio of 𝐷∕𝐻 = 0.75, at which the total exergy loss coefficient, 𝜁𝑏 𝑡𝑜𝑡, reaches its minimum value when exit loss is not considered. As particle size decreases, 𝜁𝑏 𝑡𝑜𝑡 also decreases due to enhanced heat transfer between the fluid and solid phases. The pressure loss for the studied SHS system is found to be negligible. The SLA favors a truncated cone-shaped tank with a slightly larger upper surface. Through the SLA, 𝜁𝑏 𝑡𝑜𝑡 is reduced by approximately 16.3% from 4.9% for the original design to 4.1% for the optimized design. This study demonstrates that, when used in conjunction with energy analysis, the SLA is an effective tool for optimizing energy storage systems.en1359-43112026Elsevierhttps://creativecommons.org/licenses/by-nc-nd/4.0/Computational fluid dynamicsExergyPorous mediaSecond law analysisSensible heat storageThermal energy storageTechnology::621: Applied PhysicsNatural Sciences and Mathematics::530: PhysicsJournal Articlehttps://doi.org/10.15480/882.1709010.1016/j.applthermaleng.2026.13122010.15480/882.17090