Development of waste based biochar/lauryl alcohol as new shape-stable composite phase change material and its solar thermo-regulative performance in a building material

The integration of phase change materials (PCMs) with biomass-derived biochar offers a sustainable and energy-efficient approach for developing composites with enhanced thermal functionality. In this study, a leakage-resistant composite was prepared by impregnating olive waste pulp (OWP)-based biochar (BC) with 45 wt% lauryl alcohol (LOH). The OWP-BC/LOH composite was incorporated into concrete by partially replacing sand at 10 %, 15 %, and 20 % to produce advanced materials for building energy conservation. Extensive tests covering morphological, physical, mechanical, thermal stability, thermal energy storage (TES), and solar thermoregulation were conducted. The compressive strengths of TES-integrated concretes were 45.31 MPa, 37.94 MPa, and 28.48 MPa for 10 %, 15 %, and 20 % replacements, respectively. While lower than the control, these values remain acceptable considering the improved thermal regulation. At 20 % replacement, apparent porosity, water absorption, and dry unit weight were measured as 23.3 %, 14.91 %, and 1869.11 kg/m³, respectively. FTIR analysis confirmed strong interactions between OWP-BC and LOH. DSC results revealed a melting point of 20.18 °C with a latent heat capacity of 111.9 J/g, maintaining stability after 600 heating–cooling cycles. TGA analysis indicated that the working temperature range was well below the onset of thermal degradation, ensuring long-term durability. Thermal conductivity decreased by 13 %, reaching 0.93 W/m·K. Furthermore, solar thermoregulation tests showed that 20 % OWP-BC/LOH concrete provided effective daytime cooling and nighttime heating. The use of OWP-BC/LOH composites could potentially reduce annual building energy consumption up to 27 kWh m⁻² y⁻¹ and lower CO₂ emissions by approximately 12 kg. Overall, these findings highlight OWP-BC/PCM-modified concretes as promising TES materials for sustainable and energy-efficient construction.