Development of a garlic peel biochar-based shape-stabilized phase change material to reduce energy demand for building cooling

Incorporating Phase change materials (PCMs) into buildings provide notable benefits to passive building thermal management. The PCM absorbs heat during peak solar irradiation and temperature and releases it when temperature falls. Maintaining a lower indoor temperature using PCM reduces the cooling energy demand in energy-efficient buildings. The integration of PCM into buildings can be achieved by developing form-stable PCM, which is impregnated into Garlic Peel Biochar (GPB). The activated GPB obtained by pyrolysis process at different temperature 500 °C, 600 °C, and 700 °C. The biochars and OM35 are combined in different biochar-to-PCM loading ratios by weight 1:3, 1:4, and 1:5. The biochar and PCM are mixed through the process of direct impregnation and vacuum impregnation. The vacuum impregnation is more effective than direct impregnation revealed from PCM leakage tests. The leakage test also discloses that bio-composite of biochar produced at 700 °C, named GPB700 and OM35 in a loading ratio 1:5 has the lowest leakage due to the porous and stacked morphology of the biochar. The GPB700 is alkali activated with KOH at a temperature 800 °C. The activated GPB700 (KOH-AGPB) impregnated with same quantity of OM35. This showed that further reduction in leakage due to its increased porosity and high surface area of 1459.930 m2/g. The Brunauer-Emmett-Teller (BET) analysis also revealed that the KOH-AGBP has pores of average diameter 3.18 nm and mean pore volume between 0.305 cc/g. The X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) curves of the OM35/KOH-AGPB SSPCM confirm that no change in the crystal structure of the PCM after impregnation and purely physical interaction between the PCM and activated biochar without any undesired chemical reaction. Hence proving them chemically compatible. The thermogravimetric analysis (TGA) reveals that encapsulating OM35 in the carbon-rich activated bio char enhances thermal stability to the PCM. The strong physical affinity between KOH-AGPB and OM35 due to high interfacial interactions with OM35 molecules inhibits thermal degradation. The Differential Scanning Calorimetry (DSC) test found that the OM35/KOH-AGPB SSPCM has a mere 22.3 % reduction in latent heat of melting at 121.9 J/g.