Optimisation electrified metallic phase change material process in direct steam generation

Cost reduction remains a central objective in the development of concentrated solar power (CSP) technologies. Direct steam generation (DSG) systems coupled with metallic phase change materials (PCMs) have emerged as a promising solution to eliminate intermediate heat transfer fluids, thereby reducing system complexity and cost while improving overall plant efficiency and environmental performance. However, significant thermal gradients and local overheating within the storage unit remain critical challenges that hinder optimal operation. To address these limitations, this study proposes and evaluates an advanced temperature control strategy based on the axial sectorisation and non-uniform electrification of the heating system. The impact of non-uniform (gradient) heating with varying power intensities on a metallic PCM storage tank is numerically investigated to identify optimal band heater configurations. A three-dimensional computational fluid dynamics (CFD) model, developed in ANSYS Fluent, is used to predict the thermal behaviour of the metallic PCM within a vertical shell-and-multitube configuration, accounting for the coupled effects of natural convection and thermal conduction. The model is validated against experimental and numerical data from the literature, showing good agreement. Key performance indicators, including liquid fraction evolution, temperature distribution, and stored energy during the charging process, are analysed. The results demonstrate that non-uniform (gradient) heating significantly enhances thermal homogeneity, mitigates overheating, and promotes a more balanced melting process compared to uniform heating. As a result, charging efficiency is improved while reducing the total power input required. These findings highlight the critical role of tailored electrification strategies in optimising high-temperature latent heat storage systems. The proposed approach provides a practical design framework for the development of controllable, high-performance thermal energy storage solutions based on metallic PCMs, supporting their deployment in industrial decarbonisation and advanced CSP applications.