Browsing by Author "Goracci, Guido"
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Item Cement Based Materials with PCM and Reduced Graphene Oxide for Thermal Insulation for Buildings(Springer Science and Business Media B.V., 2023) Erkizia, Edurne; Strunz, Christina; Dauvergne, Jean Luc; Goracci, Guido; Peralta, Ignacio; Serrano, Ángel; Ortega, Amaya; Alonso, Beatriz; Zanoni, Francesca; Düngfelder, Michael; Dolado, Jorge S.; Gaitero, Juan Jose; Mankel, Christoph; Koenders, Eduardus; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓN; Tecnalia Research & InnovationEnergy demand for heating and cooling represents a large part of building´s (residential and non-residential) energy consumption around the world. Development of thermal insulating construction elements with thermal energy storage and release capacity could be one way of reducing this consumption while maintaining thermal comfort inside the buildings. Using phase change materials (PCMs) as thermal storage/release materials for “porous” cement-based construction elements is a possible solution. However, the relatively low thermal conductivity of the cement matrix could impair the efficient transfer of the heat to the PCM reducing its effectivity. Addition of thermal and electrically conductive nanoparticles such as graphene-based particles could improve enough the thermal and electrical conductivity but maintain a good energy storage capacity. In this study the production of cement pastes with different dosage of PCMs (20% and 40% in volume) and reduced graphene oxide will be described. Furthermore, the characterization of their thermal and electrical conductivity, latent heat and thermal diffusivity will also be shown and discussed.Item Electrical Conductive Properties of 3D-PrintedConcrete Composite with Carbon Nanofibers(2022-11) Goracci, Guido; Salgado, David M.; Gaitero, Juan J.; Dolado, Jorge S.; Tecnalia Research & Innovation; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNElectrical conductive properties in cement-based materials have received attention in recent years due to their key role in many innovative application (i.e., energy harvesting, deicing systems, electromagnetic shielding, and self-health monitoring). In this work, we explore the use 3D printing as an alternative method for the preparation of electrical conductive concretes. With this aim, the conductive performance of cement composites with carbon nanofibers (0, 1, 2.5, and 4 wt%) was explored by means of a combination of thermogravimetric analysis (TGA) and dielectric spectroscopy (DS) and compared with that of specimens prepared with the traditional mold method. The combination of TGA and DS gave us a unique insight into the electrical conductive properties, measuring the specimens’ performance while monitoring the amount in water confined in the porous network. Experimental evidence of an additional contribution to the electrical conductivity due to sample preparation is provided. In particular, in this work, a strong correlation between water molecules in interconnected pores and the (Formula presented.) values is shown, originating, mainly, from the use of the 3D printing technique.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.