Browsing by Author "Rojas, Esther"
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Item Feasibility of Storing Latent Heat with Liquid Crystals. Proof of Concept at Lab Scale(2016-05) Bayon, Rocio; Coco, Silverio; Barcenilla, Maria; Espinet, Pablo; Imbuluzqueta, Gorka; Hidalgo, Jokin; Rojas, Esther; SISTEMAS FOTOVOLTAICOS; VALORIZACIÓN DE RESIDUOSIn this work, the first experimental results of thermotropic liquid crystals used as phase change materials for thermal storage are presented. For that purpose, the n = 10 derivative from the family of 4-n-alkoxybiphenyl-4-carboxylic acids has been prepared. Different techniques like polarized-light microscopy, differential scanning calorimetry, thermogravimetric analysis and rheological measurements have been applied for its characterization. Having a mesophase/isotropic transition temperature around 251 degrees C, a clearing enthalpy of 55 kJ/kg, a thermal heat capacity of around 2.4 kJ/kg and a dynamic viscosity lower than 0.6 Pas, this compound fulfills the main requirements for being considered as latent heat storage material. Although further studies on thermal stability are necessary, the results already obtained are both promising and encouraging since they demonstrate de viability of this new application of liquid crystals as thermal storage media.Item A numerical study of geopolymer concrete thermal energy storage: Benchmarking TES module design and optimizing thermal performance(2023-12-25) Rahjoo, Mohammad; Rojas, Esther; Goracci, Guido; Gaitero, Juan J.; Martauz, Pavel; Dolado, Jorge S.; Tecnalia Research & InnovationGeopolymer (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.Item Thermal Energy Storage (TES) Prototype Based on Geopolymer Concrete for High-Temperature Applications(2022-10) Rahjoo, Mohammad; Goracci, Guido; Gaitero, Juan J.; Martauz, Pavel; Rojas, Esther; Dolado, Jorge S.; Tecnalia Research & Innovation; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNThermal energy storage (TES) systems are dependent on materials capable of operating at elevated temperatures for their performance and for prevailing as an integral part of industries. High-temperature TES assists in increasing the dispatchability of present power plants as well as increasing the efficiency in heat industry applications. Ordinary Portland cement (OPC)-based concretes are widely used as a sensible TES material in different applications. However, their performance is limited to operation temperatures below 400 °C due to the thermal degradation processes in its structure. In the present work, the performance and heat storage capacity of geopolymer-based concrete (GEO) have been studied experimentally and a comparison was carried out with OPC-based materials. Two thermal scenarios were examined, and results indicate that GEO withstand high running temperatures, higher than 500 °C, revealing higher thermal storage capacity than OPC-based materials. The high thermal energy storage, along with the high thermal diffusion coefficient at high temperatures, makes GEO a potential material that has good competitive properties compared with OPC-based TES. Experiments show the ability of geopolymer-based concrete for thermal energy storage applications, especially in industries that require feasible material for operation at high temperatures.