Numerical simulation and experimental study on fan-driven forced convection heat storage in a cascaded phase change thermal storage system

Thermal energy storage addresses the intermittency of renewable energy sources. This study presents a novel approach by integrating fan-driven forced convection into a Cascaded Phase Change (CPCS) thermal storage system, aiming to overcome the inherent limitation of low thermal conductivity in PCMs and to coordinate the melting processes across different temperature zones. The work uniquely couples experimental characterization of tank temperature stratification with a synergistic CPCS-forced convection design. Numerical and experimental investigations reveal how forced convection intensity (characterized by N u ) governs melting time, storage efficiency, and inter-regional phase change synergy. Results demonstrate that active forced convection significantly enhances performance, with an optimal fan speed of 80 r/min achieving the best coordination (minimized S tdif of 0.03) and peak system efficiency ( S ttotal of 0.43), thereby improving overall heat storage capacity by 8.1% compared to natural convection. Crucially, the study identifies that excessively low convection intensity fails to yield net energy benefits, providing critical guidance for optimizing active thermal storage systems. • Tank stratifies at 1/3 height (90 min), homogenizes by 240 min. • PCM melts faster with N u ; 80 r/min cuts PCM 30 time 55% to 41 min. • Performance improves with N u but plateaus beyond 2259(PCM 30 ) and 3945 (PCM 28 ). • At 80 r/min, system efficiency peak: S ttotal reaches 0.43, S tdif minimizes to 0.03. • Forced convection speed at 20 r/min, η energy is only 0.48.