Study on the Influence of Paraffin-Based Composite Walls on Thermal Performance in Solar Greenhouses

This study developed a paraffin phase-change material (PCM) composite wall for solar greenhouses by incorporating paraffin into the back wall interlayer. Using finite element simulations and comparative experiments with different wall structures (The conventional wall system comprises sintered bricks, extruded polystyrene (XPS) boards, and cement mortar finishing layers), we analyzed the thermal performance of this design (The tests were conducted from May to June 2024 and from November to December 2024 in Daqing, Heilongjiang Province, China). Numerical calculations showed the paraffin composite wall achieved a total thermal resistance of 2.49 (m 2 ·K)/W, representing a 4.8% improvement over conventional walls. Simulation results indicated 0.24-1.09°C higher average daily temperatures in PCM-equipped greenhouses. Experimental data confirmed a 0.61°C increase in average daily temperature under sunny conditions compared to traditional designs. In the economic benefit assessment, the labor cost for the paraffin composite wall solar greenhouse throughout the entire heating season is approximately 2.5 yuan per square meter. The strong agreement among theoretical, simulated, and experimental results validates the thermal enhancement effect of paraffin composite walls. These findings demonstrate the potential of PCM-integrated walls for improving greenhouse thermal performance and provide a theoretical basis for applying phase-change materials in agricultural structures.