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Fernandez A.G.,Complutense University of Madrid | Fernandez A.G.,University of Antofagasta | Fernandez A.G.,Solar Energy Research Center Chile | Galleguillos H.,Solar Energy Research Center Chile | Perez F.J.,Complutense University of Madrid
Oxidation of Metals | Year: 2014

The enhancements in the storage systems developed by thermo solar centrals have provided to renewable energy a considerable increase in efficiency. This improvement also fosters the design of innovative storage fluids with lower melting point and thermal stability as new molten salts mixtures. In this research, the corrosive effects of a molten nitrate mixture composed by Ca(NO3)2–NaNO3–KNO3–LiNO3 were assessed at 390 °C on a carbon steel (A516) and on low-Cr alloy steels (T11 and T22). The corrosion rates were determined by gravimetric tests, measuring the weight gain during 2,000 h, identifying the corrosion products via scanning electron microscopy and X-ray diffraction. Study of T22 steel revealed a better behavior under corrosive environment, identifying the formation of MgCr2O4 protective spinels mainly. Fe2O3 and Fe3O4 were the others important products found on the tests performed at 390 °C, being observed also the formation of some stable compounds with the impurities of the salt, as carbonates and sulphates. © 2014, Springer Science+Business Media New York. Source

Fernandez A.G.,Complutense University of Madrid | Fernandez A.G.,University of Antofagasta | Fernandez A.G.,Solar Energy Research Center Chile | Galleguillos H.,Solar Energy Research Center Chile | Perez F.J.,Complutense University of Madrid
Solar Energy | Year: 2014

Chile's Atacama Desert is one of the world's premier locations for the study and application of solar power. The typical impurities present in Chilean nitrates are Mg, SO4 - and Cl-, among others. Developing a heat treatment to eliminate impurities and optimise the quality of the salts from the solar flats of the Atacama Desert is one of the most important goals of the inorganic chemistry industry in northern Chile.In this study, a full characterisation of the binary solar salt 60% NaNO3+40% KNO3 was performed by studying the influence of the most important impurities on the thermal processes and corrosiveness at the storage temperatures of the most important solar thermal plants.Moisture is another parameter that is important for this technology. The corrosion test results improve after heat treatment.The corrosion characteristics were determined using gravimetric tests, measuring the weight gain of three alloy steels with low Cr contents at 390. °C over 2000. h and identifying the corrosion products using scanning electron microscopy (SEM) and X-ray diffraction (XRD).Fe2O3 and Fe3O4 were the most important corrosion products. Additionally, some stable compounds were formed from the impurities in the salt, such as magnesium ferrite (MgFe2O4). © 2014 Elsevier Ltd. Source

Parrado C.,University of Antofagasta | Girard A.,Adolfo Ibanez University | Simon F.,University of Granada | Fuentealba E.,University of Antofagasta | Fuentealba E.,Solar Energy Research Center Chile
Energy | Year: 2016

This study calculates the LCOE (Levelized Cost of Energy) on the PSDA (Atacama Solar Platform) for a solar-solar energy mix with the objective of evaluate new options for continuous energy delivery. LCOE was calculated for three 50 MW (megawatt) power plants: A PV (photovoltaic), a CSP (concentrated solar power) plant with 15 h TES (thermal energy storage) and a hybrid PV-CSP plant constituted with 20 MWp of PV and 30 MW of CSP with 15 h TES. Calculations present two scenario projections (Blue Map and Roadmap) until 2050 for each type of plant. Due to the huge solar resource available in northern Chile, the PV-CSP hybrid plant results to be a feasible option for electricity generation, as well as being effectively able to meet electricity demand profile of the mining industry present in the area. This type of energy could mitigate long-term energy costs for the heavy mining activity, as well as the country CO2 emissions. Findings point out that PV-CSP plants are a feasible option able to contribute to the continuous delivery of sustainable electricity in northern Chile. Moreover, this option can also contribute towards electricity price stabilization, thus benefiting the mining industry, as well as reducing Chile's carbon footprint. © 2015 Elsevier Ltd. Source

Fernandez A.G.,Complutense University of Madrid | Fernandez A.G.,Solar Energy Research Center Chile | Ushak S.,University of Antofagasta | Ushak S.,Solar Energy Research Center Chile | And 3 more authors.
Applied Energy | Year: 2014

In this study, the effect of the addition of LiNO3 and/or Ca(NO3)2 to the solar salt NaNO3/KNO3, which is used as a storage material in CSP plants, on the physicochemical properties thereof was studied. Thermal analyses were performed by differential scanning calorimetry (DSC), modulated differential scanning calorimetry (MDSC) and thermogravimetric analysis (TGA), obtaining the phase transitions, melting points, heat capacities and thermal stability of the materials studied. In addition, viscosity measurements were carried out at different temperatures close to the melting point of the salt mixtures to determine their flowability.The study of these low-melting-point mixtures was executed through the synergistic effect exerted by a 30% LiNO3+60% KNO3+10% Ca(NO3)2 mixture, and it was observed that the addition of LiNO3 increases the thermal stability of the tested salts, whereas the addition of Ca(NO3)2 reduces the melting points and improves the economic cost of these mixturesThese mixtures were designed such that the melting point of the molten nitrates would be reduced, allowing for the mixtures' direct use as storage materials in parabolic-trough solar power plants, therefore replacing the synthetic oil currently used as a heat transfer fluid (HTF) and heat exchanger oil. The use of these mixtures is intended to reduce the economic costs and improve the thermal storage of current solar technology. © 2014 Elsevier Ltd. Source

Ushak S.,University of Antofagasta | Ushak S.,Solar Energy Research Center Chile | Judith Cruz M.,University of Antofagasta | Cabeza L.F.,University of Lleida | And 2 more authors.
Materials | Year: 2016

The literature shows that inorganic phase change materials (PCM) have been very seldom microencapsulated, so this study aims to contribute to filling this research gap. Bischofite, a by-product from the non-metallic industry identified as having good potential to be used as inorganic PCM, was microencapsulated by means of a fluidized bed method with acrylic as polymer and chloroform as solvent, after compatibility studies of both several solvents and several polymers. The formation of bischofite and pure MgCl2·6H2O microcapsules was investigated and analyzed. Results showed an efficiency in microencapsulation of 95% could be achieved when using 2 min of fluidization time and 2 kg/h of atomization flow. The final microcapsules had excellent melting temperatures and enthalpy compared to the original PCM, 104.6°C and 95 J/g for bischofite, and 95.3 and 118.3 for MgCl2·6H2O. © 2015 by the authors. Source

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