Transient thermal performance analysis of cascaded latent heat and cold stores for Carnot battery-based combined cooling, heating and power systems

Carnot batteries (CBs) have emerged as a scalable long-duration energy storage solution. Their reliance on thermal energy storage highlights the importance of cascaded latent heat and cold stores (CLHCSs), which can offer flexible thermal management but lack transient operation and performance studies. In this paper, a dynamic model of CLHCSs tailored for CB systems is developed, and the CLHCS operating modes enabling combined cooling, heating and power (CCHP) supply are proposed. Key parameters, including tube number, stage length, stage number, and charging-discharging duration, are investigated. The results show that CLHCSs demonstrate superior thermodynamic performance in pure electricity supply mode, achieving roundtrip efficiency of 99% and 94% respectively. The parameter analysis indicates that a smaller tube number enhances roundtrip and exergy efficiencies, while increasing stage number yields limited benefits. In contrast to moderate overcharging, insufficient charging more severely compromises the thermal energy storage and release performance of CLHCSs. Moreover, the case optimisation results reveal that exergy efficiency serves as a more effective objective function than the roundtrip efficiency for the CLHCSs of CB systems to enhance thermodynamic performance. This study suggests that there are promising reasons to continue to advance CLHCS technology in CB-based CCHP systems.