Experimental and Numerical Modelling of Power-to-Power High Temperature Latent Heat Thermal Energy Storage Systems

Abstract

Energy storage systems play a crucial role in enabling the integration of variable renewable energy technologies into power systems. This PhD thesis aims to explore the development and evaluation, both experimental and numerical, of a novel high-temperature latent heat thermal energy storage (LHTES) systems designed to support long-duration energy storage and improve the reliability of power systems that depend on intermittent renewable energy sources.
A 600 kWh Electrical Thermal Energy Storage (ETES) prototype underwent extensive field testing, primarily based on temperature and power measurements. The prototype utilizes aluminum–silicon (88Al–12Si) alloy as the phase change material (PCM), sodium as the heat transfer fluid, and a hydrogen-powered Stirling engine for electricity generation. The system demonstrated stable power output for over 13 hours, achieving a round-trip efficiency of 23%, with quick responsiveness (~ 2s) to changing load conditions, key features for renewable-integrated and off-grid applications.
To better understand and optimize the system’s operation, a validated 3D computational fluid dynamics (CFD) model, based on enthalpy-porosity method, was developed. The simulations provided insights into the PCM’s melting and solidification behavior and revealed how changes in heat flux distribution and operating conditions can improve system efficiency and performance. The discharge process, in particular, was found to be highly efficient due to the PCM’s excellent thermal conductivity, allowing for simpler system geometry without sacrificing heat transfer.
The considered LHTES system was then compared against two storage systems: a shell-and-tube LHTES and a packed bed system using encapsulated PCM. The comparison showed that the LHTES strikes an effective balance between discharge duration and temperature stability, while also maintaining a competitive material cost of 11.1 USD/kWh, significantly lower than the cost of the encapsulated design.
In summary, this research confirms that the studied LHTES technology as a technically viable and economically promising solution for high-temperature energy storage. The findings provide a solid foundation for future development and help advance the role of LHTES in creating more flexible, resilient, and sustainable energy systems.

Date of Award	2025
Original language	American English
Supervisor	Imran Afgan (Supervisor)