A detailed review of evacuated tube solar collectors for sustainable energy, current trends and future prospects

Abstract

Evacuated tube solar collectors (ETSCs) are among the most efficient solar thermal technologies, reliably converting solar radiation into usable thermal energy across a wide range of climatic conditions. Recent studies on ETSCs cover a broad spectrum of themes. Opportunities for enhancing performance include the use of thermal energy storage, nanofluids, optical concentrators, and inserts. Additionally, new strategies include computational modelling, AI-based optimization, adaptive tilt mechanisms, and multi-criteria decision frameworks. Researchers have also combined thermodynamic analyses with theoretical models and experimental investigations to evaluate system behaviour in greater depth. In parallel, their integration with other renewable energy technologies has been explored, while sector-specific applications, environmental advantages through CO2 mitigation, and techno-economic aspects with policy relevance have been widely reported. Evidence from experimental tests, simulation studies, and field demonstrations shows notable improvements in system design but also highlights persistent operational challenges and efficiency trade-offs. This article provides a comprehensive overview, assesses the current state of development, and connects recent advances with practical applications, while identifying key challenges and research needs to support the long-term sustainability of ETSCs.