Mapping thermal energy storage research in buildings (2020–2025): a bibliometric analysis of trends, themes, and global collaboration

• Comprehensive bibliometric mapping of TES research in buildings (2020–2025) • Analysis of 5,352 Scopus publications conducted using VOSviewer software. • Dataset comprised 79.2% articles, 12% conference papers, and 8.8% reviews. • Dual-core structure identified: material innovation and system optimization. • Transition from PCM feasibility toward integrated, intelligent TES systems. • Bio-based and recyclable PCMs emerging as key sustainable TES materials. • China, India, and the United States lead global TES research collaborations. • European nations exhibit dense intra-regional links under EU frameworks. • Keyword evolution indicates a shift to sustainability-driven applications. This study provides an extensive bibliometric analysis of the research landscape surrounding thermal energy storage (TES) applications in buildings. The analysis covers publications from January 2020 to December 2025 and was conducted in October 2025. Given the urgent global need to enhance energy efficiency, TES technologies have emerged as pivotal solutions for managing energy consumption and optimizing building performance. The primary objectives of this research are to systematically map the scholarly literature, identify dominant research themes, reveal collaboration patterns, and assess the contributions of leading countries, institutions, and authors. Specifically, this paper addresses the following research questions: (1) What thematic trends define TES research in the built environment? (2) Which countries and institutions are at the forefront of TES innovation, and how have their collaborations evolved? (3) Who are the most influential authors in the field? Based on 5,352 records retrieved from Scopus using a Boolean search and refined through keyword harmonization, the analysis employed VOSviewer to generate visualizations such as keyword co-occurrence maps, and country and author level co-authorship networks. The dataset, comprising 79.2% research articles, 12% conference papers, and 8.8% review articles, showed a steady global increase in publication output over the study period. China, India, and the United States emerged as the leading contributors, while European countries maintained dense intra-regional collaborations fostered by EU energy-efficiency programs. Emerging participation from Middle Eastern and South Asian nations, along with France’s partnerships with North African countries, illustrates the increasing geographic diversification of the field. Thematic mapping revealed four dominant research clusters: (1) optimization and AI-based TES control, (2) phase change materials and bio-based composites, (3) TES integration within building envelopes and hybrid systems, and (4) heat transfer modeling and nanoscale enhancement. Collectively, these indicate a disciplinary shift from material-centric studies toward integrated, intelligent, and sustainability-driven TES applications. Despite rapid growth, gaps persist in techno-economic assessment, long-term durability testing, and standardization, underscoring the need for stronger cross-disciplinary collaboration. This study provides a data-driven roadmap for guiding future TES innovation, linking material design, system integration, and policy-oriented research within the sustainable built environment.