Thermal performance characteristics of STC system with Phase Change Storage

Storing solar energy heat using Phase Change Materials (PCM) is an effective method. The combination of solar collector and PCM in one unit is being currently studied. The performance characteristics of the proposed Solar Tube Collector (STC) are being analysed analytically and experimentally. Fundamental experiments were performed to simulate a direct contact solar storage system, using two vertical cylindrical concentric tubes with the annular space between them filled Stearic acid (C18H38O2, melting temperature 70 °C). Experimental testing apparatus has been set up to simulated real system conditions, for an assumed initial and boundary conditions, to provide quantitative information concerning the heat transfer and the timewise evolution of the solid-liquid interface and to identify the role and pattern of natural convection and of the movement of the boundary layer in the liquid phase. For the heat charging mode, the experimental results for different types of fin structures have shown that the effect of melting process is strongly effected by the variation of the imposed conditions, in addition to the different trends of the melting profiles along the axial direction due to the effect of natural convection.