A numerical study of geopolymer concrete thermal energy storage: Benchmarking TES module design and optimizing thermal performance

Geopolymer (GEO) concrete emerges as a potential high-temperature thermal energy storage (TES) material, offering a remarkable thermal storage capacity, approximately 3.5 times higher than regular Portland cement (OPC) concrete, without compromising its environmentally benign nature. This research dissects the application of GEO concrete as a high-temperature TES material, primarily focusing on its optimization and scalability. The introductory part of the study involves the development and validation of a three-dimensional numerical model using computational fluid dynamics (CFD). The model demonstrated an average accuracy rate of 5 %, as justified by empirical data. Later, a two-tiered investigation to determine the optimal design for GEO concrete TES systems was investigated. Three different geometries plus the impact of crucial parameters such as air velocity, tube diameter, and module size on the thermal storage capacity (Q) studied. It further extends into a parametric examination, exploring a variety of tube sizes, arrangements, and configurations. It is found that air velocity primarily influences Q. A subsequent phase provides an analysis of the thermodynamic effects brought by the inclusion of tubes within TES modules through an equivalent parametric study. It exposes the thermal resistance resulting from tube insertion. The study reinforces the superior thermal performance of tubeless GEO concrete TES configurations, as signified by overall heat transfer rate (Q̇). The study also signals the significant roles of key parameters in determining the temperature (T) and Q within TES unit using Pearson's correlation coefficient equation. As a final observation, this work emphasizes the sustained significance of on-site evaluations to consistently monitor the interplay between TES materials and high-temperature fluids (HTFs) over extended periods for viability analysis purposes.