Hybrid solar phase change material systems for low-carbon buildings

Hybrid solar phase-change material systems are increasingly studied to reduce building energy demand, improve solar energy use, and support low-carbon building operation. However, existing studies remain dispersed across passive PCM envelopes, PV/PVT cooling, solar thermal storage, and HVAC-linked applications, making direct system-level comparison difficult. This review critically examines hybrid solar PCM systems for buildings using a common framework that covers system typologies, PCM selection, heat-transfer enhancement, thermal and exergy performance, techno-economic feasibility, lifecycle carbon implications, and deployment barriers. The review shows that reported benefits vary because performance depends not only on latent heat capacity but also on phase-transition temperature matching, charge–discharge completeness, climate suitability, encapsulation durability, heat-transfer pathway, and control strategy. Passive and ventilative PCM systems are more suitable for climates with effective night-time discharge; PV/PVT-PCM systems require reliable heat rejection; solar-thermal PCM systems are useful for heating and hot-water applications; and HVAC-linked PCM systems provide controllable load shifting in commercial buildings. The review identifies low thermal conductivity, incomplete cycling, fire safety, embodied carbon, cost uncertainty, and lack of standardized performance metrics as major barriers. A climate- and application-based decision framework is proposed to support the practical selection and low-carbon deployment of solar PCM systems in buildings.