Numerical Modeling and Experimental Validation of a High-Temperature Latent Heat Thermal Energy Storage System Using Metallic Phase Change Materials for Concentrated Solar Power Applications

To ensure reliable performance for the power-block of CSP plants, high power density and near-isothermal discharge must be achieved. A robust means of achieving this is through thermal energy storage (TES). High temperature latent heat storage (LHS) with phase change materials (PCMs) can serve these purposes, however the conventional salts used in PCMs typically suffer from low thermal conductivity that limits power density and increases energy storage charging/discharging times. This manuscript investigates ways to address these limitations using high temperature metallic phase change materials (MPCMs) while also developing a validated numerical framework to aid in their design. To this end, a transient three-dimensional numerical model based on the enthalpy-porosity formulation of the governing equations was developed to solve the coupled momentum and energy equations in both the heat transfer fluid (HTF) and PCM domains; the HTF was treated as turbulent via a RANS-SST closure, while temperature-dependent thermophysical properties were specified via user-defined functions for the HTF and PCM domains. Alongside the simulations, a lab-scale experimental shell-and-tube rig was constructed and fitted with (1Hz sampling) an aluminum-silicon eutectic PCM (Al-12.5wt%Si) around an electrically-heated tube passing a high-temperature HTF; a matrix of charge and partial discharge tests were performed at various inlet temperatures and flow rates. There is good agreement between the numerically predicted and experimental results: local PCM temperature traces at strategic locations track the measured time histories with RMSEs