Sustainable biochar–bio-oil nanophase change materials for enhanced solar thermal energy storage systems

The phase change materials (PCMs) could be stored and release thermal energy via reversible phase changes, allowing for high-density heat storage at virtually constant temperatures. Thus system integration stabilises temperature swings, improves the performance of thermal management and increases energy efficiencies. The sustainable biochar–bio-oil-based composite PCM with nano-scale porosity for energy storage was developed in this investigation. Hence, biochar made from rice husk and coconut shell may assist bio-oil adsorption and almond shell bio-oil was added at 5, 10, 20, 30 and 40 wt.%. The composite with 40 wt.% bio-oil-loaded PCM had an optimal melting temperature of 62°C, a latent heat capacity of 118.6 J/g and a thermal conductivity of 0.34 W/mK. The composite retained 42.3% char residue at 800°C, improving its specific heat capacity and thermal stability. These findings show that 40 wt.% biochar-based composite PCM with nano-scale porosity has excellent heat storage, thermal transport and structural stability, making it a suitable choice for solar thermal and sustainable energy storage systems.