Passive application of PCMs for the Trombe wall: a review

Passive sustainable buildings are crucial for mitigating the energy crisis and addressing global warming by effectively reducing greenhouse-gas emissions and maximizing solar-energy utilization. This is particularly significant considering the energy consumption of heating, ventilation, and air-conditioning systems. The Trombe wall system is regarded as one of the most effective passive building technologies owing to its potential ability to store and release thermal energy to reduce temperature fluctuations and improve thermal comfort. More importantly, these effects can be enhanced by employing appropriate storage materials, particularly phase change materials (PCMs), owing to their unique thermal properties: high heat-storage capacity within narrow temperature variations. Therefore, this study reviews the passive application of PCMs to Trombe walls developed over the last 40 years. This study summarizes the PCM thermal-energy storage mechanism, classification, and encapsulation and provides a comprehensive list of different PCMs appropriate for Trombe walls in the laboratory or on the market. This work also provides a comprehensive and updated review of PCM Trombe wall configurations, including passive heating and passive hybrid (cooling and heating) configurations. Based on the review results, the main directions for future studies are established and proposed.