Browsing by Author "Fuentealba, Edward"

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    Compatibility of alumina forming alloys with LiNO3-containing molten salts for solar thermal plants
    (2022) Fernandez, Angel G.; Pineda, Fabiola; Fuentealba, Edward; Jullian, Domingo; Mallco, Abdiel; Walczak, Magdalena
    The next generation of solar thermal plants will increase the operating temperatures; thus, new structural materials with better performance than the currently used should be required. Alumina forming alloys (AFA) are an alternative since they have been reported as highly resistant to corrosive environments, including molten salts. In this study, two AFA (OC4 and HR224) were exposed to a ternary lithium-containing nitrate molten salt mixture (57 wt.% KNO3-30 wt.% LiNO3-13 wt.% NaNO3) at 550 degrees C for 1000 h to determine their corrosion compatibility through gravimetric and complementary techniques. The mass gain results revealed a good performance of both alloys, allowing them to be recommended for use in solar thermal plants. However, HR224 showed lower weight change attributed to a thin layer of non-porous and continuous corrosion products composed of nickel oxide and aluminum-nickel spinel, which act as protective compounds. On the contrary, OC4 showed a thick multi-layer structure of highly porous, rough, and irregular corrosion products composed mainly of iron oxides and spinels.
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    High Performance of Mn2O3 Electrodes for Hydrogen Evolution Using Natural Bischofite Salt from Atacama Desert: A Novel Application for Solar Saline Water Splitting
    (2024) Galleguillos-Madrid, Felipe M.; Salazar-Avalos, Sebastian; Fuentealba, Edward; Leiva-Guajardo, Susana; Caceres, Luis; Portillo, Carlos; Sepulveda, Felipe; Brito, Ivan; Cobos-Murcia, Jose Angel; Rojas-Moreno, Omar F.; Jimenez-Arevalo, Victor; Schott, Eduardo; Soliz, Alvaro
    Solar saline water splitting is a promising approach to sustainable hydrogen production, harnessing abundant solar energy and the availability of brine resources, especially in the Atacama Desert. Bischofite salt (MgCl26H2O) has garnered significant attention due to its wide range of industrial applications. Efficient hydrogen production in arid or hyper arid locations using bischofite solutions is a novel and revolutionary idea. This work studied the electrochemical performance of Mn2O3 electrodes using a superposition model based on mixed potential theory and evaluated the superficial performance of this electrode in contact with a 0.5 M bischofite salt solution focusing on the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) that occur during saline water splitting. The application of the non-linear superposition model provides valuable electrochemical kinetic parameters that complement the understanding of Mn2O3, this being one of the novelties of this work.
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    Long-Term Evaluation of a Ternary Mixture of Molten Salts in Solar Thermal Storage Systems: Impact on Thermophysical Properties and Corrosion
    (2024) Henriquez, Mauro; Reinoso-Burrows, Juan Carlos; Pasten, Raul; Soto, Carlos; Duran, Carlos; Olivares, Douglas; Guerreiro, Luis; Cardemil, Jose Miguel; Madrid, Felipe M. Galleguillos; Fuentealba, Edward
    Solar thermal plants typically undergo trough operational cycles spanning between 20 and 25 years, highlighting the critical need for accurate assessments of long-term component evolution. Among these components, the heat storage media (molten salt) is crucial in plant design, as it significantly influences both the thermophysical properties of the working fluid and the corrosion of the steel components in thermal storage systems. Our research focused on evaluating the long-term effects of operating a low-melting-point ternary mixture consisting of 30 wt% LiNO3, 57 wt% KNO3, and 13 wt% NaNO3. The ternary mixture exhibited a melting point of 129 degrees C and thermal stability above 550 degrees C. Over 15,000 h, the heat capacity decreased from 1.794 to 1.409 J/g degrees C. Additionally, saline components such as CaCO3 and MgCO3, as well as lithium oxides (LiO and LiO2), were detected due to the separation of the ternary mixture. A 30,000 h exposure resulted in the formation of Fe2O3 and the presence of Cl, indicating prolonged interaction with the marine environment. This investigation highlights the necessity of analyzing properties under actual operating conditions to accurately predict the lifespan and select the appropriate materials for molten salt-based thermal storage systems.