Development of a novel form-stable phase change material based on alkali activated date seed biochar to harvest solar thermal energy

The current experimental investigation intends to develop leak-resistant form-stable phase change materials (FSPCM) to promote solar energy storage performance implementing biochar as carrier matrix. Date seed biochar (DB) was produced through pyrolysis in a muffle furnace at 550 °C in inert gas atmosphere. Consequently, these carbonized date seeds was utilized as a precursor to derive chemically activated date seed biochar (ADB). BET (Brunauer-Emmett-Teller) surface area of DB and ADB was measured to be 82 m²/g and 197 m²/g respectively. Raman spectra has been carried out to study the molecular interactions, polymorphy and chemical structure of DB and ADB. Both DB and ADB have been employed as porous framework to enhance the heat transfer rate of the eutectic PCM, PA-PEG6000 which was synthesized from palmitic acid (PA) and polyethylene glycol (PEG6000). The composite ADB/PA-PEG6000 has superior PCM holding capacity analogous to DB/PA-PEG6000 owing to the larger specific surface area. Fourier-transform infrared spectra (FTIR) and X-ray diffractograms authenticated that the integration of ADB/DB and PA-PEG6000 have been executed physically. Surface investigation through FESEM illustrated that the pores of ADB and DB scaffold were thoroughly occupied with PA-PEG6000. The latent heat of melting/melting temperature of DB and ADB based FSPCMs were measured to be 202.43 J.g⁻¹/55.3 °C and 210.51 J.g⁻¹/ 56.4 °C respectively. More importantly, the developed FSPCM possess a good thermal and chemical reliability for tested 500 thermal cycles. These developed materials have potential to be used in various solar water/air heating applications.