A review of Reduced-Order Modeling of PCM-Based Latent Heat Storage Systems

Phase change material (PCM)-based latent heat storage (LHS) systems help address the mismatch between renewable energy supply and thermal demand. However, their prac-tical implementation is constrained by the strongly nonlinear and multiphysics nature of phase change, which makes high-fidelity simulations and real-time applications computationally expensive. This review examines Reduced-Order Modeling (ROM) as an effec-tive strategy to overcome this limitation by combining physics-based simplifications, projection methods, interpolation techniques, and data-driven models for PCM-based LHS systems. The review covers approaches such as two-temperature non-equilibrium and analytical thermal-resistance models, Proper Orthogonal Decomposition (POD), CFD-derived look-up tables, kriging and ε-NTU grey/black-box metamodels, and ma-chine-learning methods including artificial neural networks and gradient-boosted regressors trained from CFD data. These ROM techniques have been applied to packed beds, PCM-integrated heat exchangers, finned enclosures, triplex-tube systems, and solar ther-mal components, achieving speed-ups from tens to over 80,000 times faster than full CFD simulations while maintaining prediction errors typically below 5% or within sub-Kelvin temperature deviations. A critical comparative analysis exposes the fundamental trade-off between interpretability, data dependence, and computational efficiency, guiding method selection for specific applications. Remaining challenges include accurate representation of phase-change nonlinearity, moving phase boundaries, multi-timescale dynamics, gen-eralizability across geometries, and integration into system-level frameworks, motivating future hybrid physics–machine learning developments and standardization efforts.