A potential building heating strategy integrating solar radiation absorption and thermal energy storage

Building heating accounts for a substantial portion of energy consumption, leading to significant carbon emission. This study presents a promising heating strategy that integrates solar radiation absorption with thermal energy storage using phase change materials (PCMs), significantly enhancing indoor thermal comfort while reducing energy consumption. A composite PCM comprised of CaCl₂·6H₂O and expanded graphite was developed to achieve these goals, offering excellent thermal storage properties and a solar absorptance up to 91.4 %, allowing it to efficiently capture solar radiation. The composite PCM was formed into plate structures and incorporated into building walls with the aim of evaluating its thermal performance. Experimental findings show that the composite PCM plate, with a thickness 10 mm and installed on the southern wall of the test chamber, achieved a duration of thermal comfort (DTC) of 4.06 h—414 % longer than the reference chamber, which only achieved 0.79 h. Numerical simulations further optimized the design, revealing that a 25 mm thick PCM plate, paired with a 60° south-by-east building orientation, provided optimal performance. It achieved a DTC of 13.5 h, which is 233 % longer than the 10 mm thick PCM plate. Moreover, this optimized design ensures that the indoor temperature reaches a comfortable level by 10:00 AM. This study highlights the potential of PCM-based solar heating systems to reduce energy consumption and provides a sustainable solution for building heating in cold climates.