Thermal performance of novel form-stable disodium hydrogen phosphate dodecahydrate-based composite phase change materials for building thermal energy storage

Inorganic hydrated salt phase change materials (PCMs) have received great attention due to their capabilities to reduce building energy consumption and improve building thermal comfort. In this work, a modified PCM (DHPD-STP) with a low supercooling degree was first prepared by using disodium hydrogen phosphate dodecahydrate (Na 2 HPO 4 ·12H 2 O, DHPD) as the matrix and sodium thiosulfate pentahydrate (Na 2 S 2 O 3 ·5H 2 O, STP) as a nucleating agent. Then expanded graphite (EG) was added to DHPD-STP to afford a novel form-stable composite phase change material (CPCM). The novel CPCM obtained had a phase transition temperature (34.74 °C) appropriate for building thermal management, an excellent phase change enthalpy (184.39 J/g), and an extremely low supercooling degree (1.1 °C). The addition of EG greatly improved the form stability and cycle stability of the CPCM. Even after 200 cycles, the CPCM prepared still had a high enthalpy of phase changes (164.54 J/g). More importantly, the use of CPCM-loaded roofs effectively mitigated the variation of room temperature and improved indoor thermal comfort. The above results demonstrate the great potential of the CPCM prepared for passive building thermal management. Graphical Abstract