Climate-Adaptive Dual-Temperature Composite Phase Change Wall Design for Energy-Flexible Buildings in Smart Cities

Abstract

Buildings in cities with pronounced seasonal variations require envelope systems capable of responding to both summer cooling and winter heating demands. This study proposes a climate-adaptive wall incorporating a single layer of composite phase change material (CPCM) with two phase change temperatures (PCTs), thereby avoiding the structural complexity of conventional multilayer phase change material (PCM) walls. A three-dimensional heat transfer model was established and validated to optimize the PCM layer position, thickness, and target PCTs under the climatic conditions of Nanjing. The results indicate that the optimal configuration places a 10 mm CPCM layer at the middle of the wall, with target PCTs of 32 °C for summer and 14.5 °C for winter. Based on these targets, a binary non-eutectic caprylic acid–tetradecanol CPCM with a mass ratio of 3.0:7.0 was prepared, exhibiting two PCTs of 14.67 °C and 36.67 °C and a total latent heat of 143.83 J/g. Compared with an ordinary wall, the CPCM wall reduced indoor surface temperature amplitude by 39.55% in summer and 18.09% in winter. Relative to a single PCM wall, the corresponding reductions were 25.88% and 5.71%. The maximum indoor surface heat flux reductions reached 16.23 W/m² in summer and 3.84 W/m² in winter. In addition, a transferable climate–wall–material design framework was developed for adapting the proposed method to different cities and wall structures. These findings demonstrate that single-layer dual-PCT CPCM walls can enhance seasonal thermal buffering and support energy-flexible building design in smart cities. Received: 27 July 2026 | Revised: 7 September 2026 | Accepted: 28 September 2026



Conflicts of Interest

The authors declare that they have no conflicts of interest to this work.



Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.



Author Contribution Statement

Wei Wu: Conceptualization, Methodology, Resources, Data curation, Writing – review & editing, Supervision, Project administration. Haibin Han: Conceptualization, Methodology, Formal analysis, Investigation, Writing – original draft, Visualization. Wenzheng Li: Software, Formal analysis, Investigation, Writing – original draft, Visualization. Zhengyu Chen: Validation, Formal analysis. Haoyu Li: Investigation, Visualization. Minfen Gu: Resources. Yahui Sun: Funding acquisition. Yunjun Wang: Data curation. Xing Jin: Supervision. Chong Zhai: Conceptualization, Writing – review & editing, Project administration, Funding acquisition.