Photo-thermal conversion and energy storage characteristics of magnetic phase change composites

The problem of solar intermittency can be effectively addressed by solar-to-thermal energy storage using phase change materials (PCMs). Nevertheless, intricate operating scenarios and the extreme environment of PCMs restrict their uses, and the solar energy selective absorption also impedes the attainment of high photo-thermal conversion. In this study, paraffin wax (PW) was combined with styrene-ethylene-butylene-styrene (SEBS) and magnetic nanoparticles Fe₃O₄ to synthesize a novel kind of magnetic PCMs (PW/SEBS/Fe₃O₄). Experimental verification and simulation analysis were carried out. The results have showed that the PW/SEBS/Fe₃O₄ achieved an overall solar absorptance of 95 %, whose energy storage capacity and photo-thermal conversion were superior to those of pure PW. The PW/SEBS/Fe₃O₄ showed exceptional thermal and cyclic stability, completed phase transition rapidly, and reached a greater equilibrium temperature with the rise in light intensity. Although the PW/SEBS/Fe₃O₄ with 1.2 g Fe₃O₄ has better photo-thermal storage capacity, the PW/SEBS/Fe₃O₄ with 2.4 g Fe₃O₄ has more flexible application when considering the magneto-thermal effect. Furthermore, based on the thermo-physical property, the magneto-thermal effect of the magnetic PCMs was simulated using commercial software. This research offers a new concept for solar-thermal uses of building insulation and magnetic thermal switches.