Identification and characterization of promising phase change materials for solar cooling applications

Solar cooling technology is an attractive way to use solar thermal energy to produce cooling for buildings. Theemployment of taphase change materials (PCMs) as heat storage medium, to increase the range of utilization ofsolar thermal energy, thus improving the overall system performance, is considered very attractive.Nevertheless, in order to allow the development of latent heat storage prototypes for such an application, itis mandatory to verify the thermo-physical performance as well as the long-term stability of the availablematerials. To this aim, in the present paper, the most attractive commercial PCM as well as neat chemicalcompounds operating in the temperature range between 80 °C and 100 °C, perfectly suitable for nonconcentratingsolar cooling systems, have been identified and completely characterized. In particular, severalcycles have been performed on each material, to verify possible instabilities in their behavior. Most of the neatmaterials have confirmed to be promising for this application, thanks to their really high melting enthalpy, up to255 J/g as showed for Aluminum Ammonium Sulfate Dodecahydrate. Nevertheless, all these materials are stillnot stable, showing high supercooling, allotropic phase transition, incongruent melting and even absence of recrystallization,which makes necessary an intense work to bring them to a reliability level sufficient for realapplication. On the contrary, the commercial PCMs, even if mostly characterized by lower melting enthalpy,ranging between 120 and 150 J/g, confirmed their stability, which makes them ready for practical applications.