Understanding the damage behaviour of surrounding or host rock under cyclic thermal loading for systems such as compressed air energy storage (CAES), thermal energy storage (TES), and enhanced geothermal systems (EGS) is essential for ensuring operational safety and project longevity. While prior studies have focused on post-cycle damage assessment, the evolution of damage within individual thermal cycles has remained largely unexplored. This study addresses the gap by investigating thermal damage in granite during and after each cycle. A non-destructive experimental strategy was developed, integrating real-time acoustic emission (AE) monitoring with P -wave velocity measurements and microstructural analysis. This approach enables continuous damage tracking without compromising sample integrity, unlike conventional strength testing. The results reveal distinct damage mechanisms during heating and cooling, with cooling-induced damage dominant above 200 °C. A refined thermal damage model was developed and validated, capable of predicting granite damage at any temperature or cycle stage. These findings advance the understanding of rock behaviour under cyclic thermal stress and more accurately predict performance and lifespan for infrastructures exposed to repeated thermal fluctuations, contributing to safer and more efficient design of energy storage and geothermal systems. • Experimental method tracks continuous thermal damage in granite. • Model predicts granite damage at any temperature or cycle stage. • AE reveals stronger tension-driven damage during cooling above 200 °C. • Damage difference between heating and cooling narrows with more cycles.
Yu et al. (Wed,) studied this question.