SUBAMBIENT PASSIVE RADIATIVE COOLING WITH BARIUM SULFATE REFLECTIVE PAINT

Abstract

As global temperatures continue to rise and energy demands increase, especially in tropical regions like Malaysia, sustainable cooling solutions are becoming increasingly essential. This study explores the potential of barium sulfate (BaSO4)-based reflective paint as a passive, energy-free cooling technology. Paints were formulated with two solvents (DMF and distilled water) at three pigment concentrations (50%, 60%, and 70%), and applied to cardboard substrates for outdoor thermal testing under direct sunlight. Among all combinations, the DMF + 70% BaSO4 formulation delivered the highest cooling performance, achieving surface temperature reductions of up to 5.2 °C compared to uncoated surfaces. When applied to miniature house models, this formulation maintained internal temperatures 2–6 °C cooler than those coated with commercial white paint, particularly during peak solar hours. Extended tests on common roofing materials (zinc, plastic, cement, aluminium, and clay) showed consistent cooling across all surfaces, with plastic and zinc roofs performing best due to their lower thermal conductivity. Scanning Electron Microscopy (SEM) analysis confirmed the presence of irregular, micron-sized BaSO4 particles, which contribute to enhanced solar scattering. Additionally, cooling power analysis using the Stefan–Boltzmann equation revealed that the BaSO4 coating could reject up to 38.29 W/m² of thermal energy, translating into potential electricity savings of over RM 2,000 per year for a 100 m² roof. These findings highlight the viability of BaSO₄-based paint as a scalable and cost-effective passive cooling solution, offering both environmental and economic benefits in regions with high solar exposure.