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The encapsulation of phase change materials (PCMs) into additive manufactured porous supports is attracting great interest for developing thermal energy storage (TES) materials with improved energy performance. Here, highly porous (86 %) self-supported 3D activated carbon/alumina supports are fabricated by direct ink writing (DIW) and, then, infiltrated with solar salt, a highly corrosive PCM with a melting temperature around 220 °C commonly employed in concentrated solar power plants. This novel, robust, chemically compatible, and lightweight infiltrated 3DTES exhibits good thermal energy storage efficiency (70 %) and thermal stability, high energy storage density (381 J g−1), and avoids the liquid leakage of the molten salt. Besides, the 3D activated carbon/alumina support promotes a better ability to absorb solar energy (79 %) and enhances the thermal conductivity of the solar salt (up to 64 %). These results validate the use of DIW for manufacturing innovative TES with an enhanced energy storage behaviour.

Molten salt-based nanofluid is a thermal storage and heat transfer medium for concentrated solar thermal power plants formed by adding nanoparticles to molten salt, which can enhance the thermal performance of molten salt. However, the nanoparticles tend to aggregate in nanofluids, causing changes in thermal properties. In this work, molecular dynamics simulations were used to study the effect of morphological characteristics of aggregates on the thermal conductivity and specific heat capacity of molten salt-based nanofluids. The results show that the aggregated nanoparticles cause a greater increase in thermal conductivity and specific heat capacity than dispersed nanoparticles. Additionally, the increase in fractal dimension leads to thermal conductivity reduction, while there is no clear correlation between the fractal dimension and specific heat capacity. New insights into the thermal properties of aggregated nanofluids are provided by analyzing the contribution of material components, heat flux fluctuation modes, and energy compositions. It is found that the thermal conductivity of aggregated nanofluids is mainly dominated by the base liquid and collision term. However, the specific heat is not related to the variation in the contribution of different energy compositions. Moreover, compared to the dispersed nanofluid, the increased specific heat capacity of aggregated nanofluids is attributed to the thicker semi-solid layer. This study provides guidance for the design and control of the thermal properties of molten salt-based nanofluids. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) systems use solar energy despite its irregular availability and day-night temperature difference. Current work reports the thermal characterizations of solar salt-based phase change composites in the presence of graphene nanoplatelets (GNP). Solar salt (60:40 of NaNO3:KNO3) possessing phase transition temperature and melting enthalpy of 221.01°C and 134.58 kJ/kg is proposed as a phase change material (PCM) for high-temperature solar-based energy storage applications. Thermal conductivity must be improved to make them suitable for widespread applications and to close the gap between the system needs where they are employed. GNP is added at weight concentrations of 0.1%, 0.3%, and 0.5% with solar salt using the ball milling method to boost its thermal conductivity. Morphological studies indicated the formation of a uniform surface of GNP on solar salt. FTIR spectrum peaks identified the physical interaction between salt and GNP. Thermal characterization of the composites, such as thermal conductivity, DSC and TGA was carried out for the samples earlier and later 300 thermal cycles. 0.5% of GNP has improved the thermal conductivity of salt by 129.67% and after thermal cycling, the enhancement reduced to 125.21% indicating that thermal cycling has a minor impact on thermal conductivity. Phase change temperature decreased by around 2.32% in the presence of 0.5% GNP and the latent heat reduced by 4.34% after thermal cycling. TGA thermograms depicted the composites initiated the weight loss at around 550°C after which it was rapid. After thermal cycling, the weight loss initiated at ∼40°C lower compared to pure salt, which was found to be a minor change. Thermal characterization of solar salt and GNP-based solar salt composites revealed that the composites can be used for enhanced heat transfer in high-temperature solar-based heat transfer and energy storage applications. [ABSTRACT FROM AUTHOR]

Molten salt-based nanofluid is a thermal storage and heat transfer medium for concentrated solar thermal power plants formed by adding nanoparticles to molten salt, which can enhance the thermal performance of molten salt. However, the nanoparticles tend to aggregate in nanofluids, causing changes in thermal properties. In this work, molecular dynamics simulations were used to study the effect of morphological characteristics of aggregates on the thermal conductivity and specific heat capacity of molten salt-based nanofluids. The results show that the aggregated nanoparticles cause a greater increase in thermal conductivity and specific heat capacity than dispersed nanoparticles. Additionally, the increase in fractal dimension leads to thermal conductivity reduction, while there is no clear correlation between the fractal dimension and specific heat capacity. New insights into the thermal properties of aggregated nanofluids are provided by analyzing the contribution of material components, heat flux fluctuation modes, and energy compositions. It is found that the thermal conductivity of aggregated nanofluids is mainly dominated by the base liquid and collision term. However, the specific heat is not related to the variation in the contribution of different energy compositions. Moreover, compared to the dispersed nanofluid, the increased specific heat capacity of aggregated nanofluids is attributed to the thicker semi-solid layer. This study provides guidance for the design and control of the thermal properties of molten salt-based nanofluids.

The early modern history of the Dutch Caribbean island of Bonaire has to a large extent been influenced by its most valuable resource: solar salt. Through a multidisciplinary approach combining a landscape study, underwater and terrestrial archaeological surveys, and documentary research, the maritime cultural landscape of Bonaire's southernmost saltpan is analyzed holistically, revealing new aspects of the lives of the people who lived and toiled there. [ABSTRACT FROM AUTHOR]

Salt is an essential ingredient in the kimchi fermentation process. Solar salt has antioxidant, anti-cancer, and anti-obesity properties. The aim of this study was to determine the antioxidant and anti-inflammatory effects of solar salt brined kimchi. Purified salt (PS), dehydrated solar salt (DSS), 1-year aged solar salt (SS1), and 3-years aged solar salt (SS3) were investigated. Anti-inflammatory effects were determined by analyzing cytotoxicity, nitric oxide (NO) production, and inflammation-related gene expression in lipopolysaccharide-treated RAW264.7 cells. Antioxidant activities of DSS, SS1, and SS3 were higher than that of PS. Solar salt significantly inhibited NO production with low cytotoxicity and decreased inflammation-related gene expression. Kimchi containing solar salt (DSSK, SS1K, and SS3K) showed higher antioxidant activity than PSK. Additionally, DSSK, SS1K, and SS3K significantly inhibited NO production and decreased the expression of inflammation-related genes. Owing to the antioxidant and anti-inflammatory effects, using solar salt in kimchi preparation could have potential health benefits. [ABSTRACT FROM AUTHOR]

The protective behaviour of ZrO2-3%molY2O3 sol–gel coatings, deposited with an immersion coating technique on 9Cr-1Mo P91 steel, was evaluated with corrosion monitoring sensors using the electrochemical impedance spectroscopy technique. The tests were carried out in contact with solar salt at 500 °C for a maximum of 2000 h. The results showed the highly protective behaviour of the coating, with the corrosion process in the coated system being controlled by the diffusion of charged particles through the protective layer. The coating acts by limiting the transport of ions and slowing down the corrosive process. The system allowed a reduction in the corrosion rate of uncoated P91 steel. The estimated corrosion rate of 22.62 μm·year−1 is lower than that accepted for in-service operations. The proposed ZrO2-3%molY2O3 sol–gel coatings are an option to mitigate the corrosion processes caused by the molten salts in concentrated solar power plants. [ABSTRACT FROM AUTHOR]

Molten salts have been widely studied as the most common heat storage medium for concentrated solar power (CSP) plants. However, most studies have focused on the corrosiveness of molten salts, while this study innovatively reveals the role of stainless steel in promoting the decomposition of molten salts and the mechanism by which the halogen ions accelerate this process. Considering commercial Solar Salt as an example, the thermal stability, composition, and thermophysical properties of Solar Salt adding Cl−, Br−, and I− after contacting different stainless steel were analyzed. The results showed that Cr was the main reason for the decomposition of the molten salt, and Cl−, Br−, and I−, all accelerated the decomposition. Meanwhile, different halogen ions promoted the decomposition of molten salts through different mechanisms: oxide layer destruction and chain oxidation. [ABSTRACT FROM AUTHOR]

The incorporation of conductive nanoparticles into thermal energy storage media is one of the strategies to increase their thermal conductivity. This work unravels the impact of the addition of CuO nanoparticles on the thermal properties of solar salt, a high-temperature thermal energy storage material. The resultant CuO enhanced solar salt (CuOeSS) exhibited a maximum thermal conductivity improvement of 14.4 % at 40 °C when the concentration of CuO nanoparticles was 1 wt%. The prevalence of CuO nanoparticles as isolated aggregates resulted in a moderate thermal conductivity enhancement. The CuO nanoparticles greatly influenced α-KNO3 to β-KNO3 transition and reduced the expected positive influence on thermal conductivity at temperatures above 120 °C. The solid-phase specific heat was enhanced by 22.7 % for 2 wt% CuOeSS. Our results demonstrate the interplay between the different roles played by CuO nanoparticles, namely the thermal conductivity enhancement at lower temperatures and influencing the α-KNO3 to β-KNO3 transition at higher temperatures. The CuOeSS with 0.5 wt% CuO, which showed enhancement in both thermal conductivity and energy storage capacity, is a suitable energy storage material for applications in the temperature range of 100–245 °C. [ABSTRACT FROM AUTHOR]

The taste of kimchi is greatly affected by the salt type used during fermentation. Here, we investigated the effects of salts with different mineral contents on the microbial community and metabolite profiles of fermented kimchi using multivariate statistical analysis. We evaluated different types of salt used to prepare kimchi, namely, solar salt aged for 1 year, solar salt aged for 3 years, dehydrated solar salt, and purified salt. The main microorganisms detected in kimchi were Weissella koreensis, Leuconostoc mesenteroides, and Latilactobacillus sakei. Leuconostoc and Weissella were mainly present in kimchi supplemented with solar salt. However, a high proportion of L. sakei was present in kimchi supplemented with purified salt and dehydrated salt. Additionally, using GC-MS-based metabolite analysis, we revealed that the content of free sugars, organic acids, and amino acids differed in kimchi fermented with different salt types. Therefore, we demonstrated that salt type had a pronounced effect on the resultant microbial community and the type and concentration of metabolites present in fermented kimchi.

Two novel halophilic archaeal strains, CBA1133T and CBA1134, were isolated from solar salt in South Korea. The 16S rRNA gene sequences of the isolates were identical to each other and were closely related to the genera Natronomonas (92.3–93.5%), Salinirubellus (92.2%), Halomarina (91.3–92.0%), and Haloglomus (91.4%). The isolated strains were coccoid, Gram-stain-negative, aerobic, oxidase-positive, and catalase-negative. Growth occurred under temperatures of 25–50°C (optimum, 45°C), NaCl levels of 10–30% (optimum, 15%), pH levels of 6.0–8.5 (optimum, 7.0), and MgCl2 concentrations of 0–500 mM (optimum, 100 mM). Digital DNA-DNA hybridization values between the strains and related genera ranged from 18.3% to 22.7%. The major polar lipids of the strains were phosphatidyl glycerol, phosphatidyl glycerol phosphate methyl ester, and phosphatidyl glycerol sulfate. Genomic, phenotypic, physiological, and biochemical analyses of the isolates revealed that they represent a novel genus and species in the family Halobacteriaceae. The type strain is CBA1133T (= KACC 22148T = JCM 34265T), for which the name Sala cibi gen. nov., sp. nov. is proposed. [ABSTRACT FROM AUTHOR]

This study reports the behavior of the Ni20Cr alloy in molten nitrate salts. Its behavior was evaluated in the eutectic mixture called Solar Salt (binary salt) and in a ternary mixture (90% Solar Salt and 10% lanthanum nitrate). The addition of lanthanum nitrate was performed to determine if the presence of the La3+ cation could act as a corrosion inhibitor. Through mass loss and potentiodynamic polarization studies, the effects of both electrolytes on the corrosion resistance of the alloy at 300, 400, and 500 °C and at exposure times of 250, 500, 750, and 1000 h were determined. The results showed an increase in the corrosivity of the ternary salt, due to a decrease in its melting point and an increase in the concentration of nitrate ions. However, it was observed that the La3+ cations formed a protective layer (La2O3) on the alloy surface. In both corrosive media, the Ni20Cr alloy showed excellent corrosion resistance, due to its ability to form protective layers of Cr2O3, NiO, and NiCr2O4, in addition to the presence of a layer of La2O3 in the case of the ternary salt. [ABSTRACT FROM AUTHOR]

The corrosion resistance of structural materials, particularly in molten salt environments, is of central importance to design concentrated solar power (CSP) plants. In this perspective, the high-temperature electrochemical behavior of passive film on 316SS in solar salt composition (60 pct. NaNO3: 40 pct. KNO3 by wt. pct.) was evaluated using linear resistance polarization, Tafel polarization, and electrochemical impedance spectroscopy techniques in the application range of 400 to 550 °C. An increase in corrosion rate with temperature and severe oxidation at 550 °C was recorded. However, the corrosion potential (Ecorr) does not vary significantly. The critical analysis of the impedance bode phase diagram reveals two well-separated maxima at 400 °C, indicating the role of the passive layer during the corrosion process. At 500 °C, the observed phase angle is close to 45°, attributed to processes controlled by mass transfer limitations. While analyzing the influence of mass transfer, an equivalent circuit model has been proposed to analyze the corrosion of the 316SS, a material used for piping and containment of CSP plants in molten solar salt. [ABSTRACT FROM AUTHOR]

Enhancement of thermophysical properties of molten salt-based nanofluids is essential to reduce the geometric size and increase the energetic-exergetic efficiency of the thermal energy storage system. Moreover, the thermophysical properties of nanoparticles dispersed molten salt remain unclear, especially the anomalous enhancement of specific heat capacity (Cp). In the present study, the different concentrations (0.5, 1.0 and 2.0 wt%) of silicon carbide nanoparticles (SiC-NPs) dispersed solar salt (i.e., SiC nanosalt) were prepared using the wet chemical method, and their thermophysical properties were evaluated using various differential techniques. The crystalline structure of the SiC-NPs was analysed and confirmed using an X-ray diffractometer (XRD). Further, the size (diameter = 30.61 nm) and shape were identified in the transmission electron microscope (TEM). The differential scanning calorimetry (DSC) analysis was carried out for the prepared SiC nanosalt and found the average specific heat capacity enhancement for 1.0 wt% SiC nanosalt is 14.4 % and 8.1 % in solid (50 °C–200 °C), and liquid (250 °C–350 °C) phases, which is 8.7 % and 3.3 % higher than 0.5 wt% and 2.0 wt%. Further, the scanning electron microscope (SEM) technique was conducted for different wt% of SiC and found random dispersion (for 0.5 wt%), better dispersion (for 1.0 wt%), and agglomeration (for 2.0 wt%). From the combined result of DSC and SEM, the optimal weight loading of SiC-NPs was identified as 1.0 wt%. The thermal conductivity was measured for the prepared sample, and it was found that a thermal conductivity of 2.0 wt% is 8.85 % higher than solar salt. Finally, the thermal stability of the nanosalt was tested in thermogravimetric analysis (TGA), and it found that the maximum weight presence for the maximum wt% of SiC is 92.8 %, which resulted in the weight loss of the SiC nanosalt is similar to solar salt. • SiC nanosalt is prepared by a two-step wet chemical method. • 14.9 % and 8.2 % Cp enhancement for 1 wt% in both solid and liquid phases. • Better dispersibility was found for 1 wt% proportional to the Cp enhancement. • Thermal stability of SiC nanosalt is similar to that of solar salt up to 650 °C. [ABSTRACT FROM AUTHOR]

The objective of this paper is to study and optimise thermal energy storage systems of structured thermocline type. The system consists of a solid filler material made from waste ceramic products and a set of channels through which the heat transfer fluid flows. A well-verified and validated unsteady and one-dimensional computational model was developed for this study. The investigation is carried out considering three main output values: outlet temperature, thermocline thickness and discharged exergy. The behaviour of several parameters, such as the flow velocity and cut-off temperature difference, the height and the diameter of the tank, together with the void fraction and the diameter of the channels, were studied. The results suggest that increasing the cut-off temperature, tank diameter and height, and/or void fraction reduces the thermocline thickness. Similarly, decreasing the flow velocity and/or channel diameter leads to a reduction in thermocline thickness. In order to increase the discharged exergy, it is necessary to reduce the cut-off temperature, flow velocity, or channel diameter while increasing the void fraction, as well as the diameter and height of the unit. This work outlines design guidelines aimed at optimising operational and geometrical parameters to achieve improved efficiency for structured thermocline systems. • Parametric study for optimising structured thermal energy storage systems. • Study of waste ceramics as solid filler, enhancing sustainability. • Validated unsteady, 1D model to evaluate thermocline performance. • Studied flow velocity, tank diameter, height, void fraction and channel diameter. • Evaluated discharged exergy, thermocline thickness and outlet temperature. [ABSTRACT FROM AUTHOR]

Adding an appropriate amount of chloride or sulfate salts to molten nitrates is an effective way to improve the thermal stability temperature and energy density of solar salts. However, the corrosivity of the mixed solar salts is enhanced significantly. In this paper, the effect of chlorides and sulfates on the corrosion of SS347 and GH3539 in molten solar salt is investigated. The high oxygen pressure and basic environment in molten nitrates causes the formation of an external Fe oxides layer and inner FeCr 2 O 4 layer for SS347. Unlike SS347, the corroded GH3539 presents an exclusive film of NiO and many core-shell structured nodules with Ni as core and NiO as shell, followed by a region of internal oxidation involving Ni, W and Cr. The additives chlorides produce an oxidation-chlorination environment, causing spallation of oxide scale from SS347, but without significant effect on GH3539 due to lower thermodynamic stabilities of Ni and W chlorides than Fe and Cr chlorides. The addition of sulfates to solar salt also harms the adhesion of the scale on SS347 to a certain extent. While the additives sulfides accelerate the corrosion of GH3539, forming a thick porous NiO layer and a serious internal sulfidation zone. • The corrosion of SS347 and GH3539 at 600 ℃ in molten solar salt without and with chlorides and sulfates is studied. • The high oxygen partial pressure and the highly basic property are the main reasons for high corrosivity of molten nitrates. • The addition ofchlorides to solar salt produces an oxidation-chlorination environment, causing separation and spallation of the oxide scale from SS347. • Apart from the outer NiO layer, a region of internal oxidation involving Ni, W and Cr are also formed for GH3539. • The additives sulfates accelerate greatly the corrosion of GH3539, but without significant effect on SS347. [ABSTRACT FROM AUTHOR]

A 1000-year-old marine solar saltern in Hainan Island, South China, is in the continuation of traditional skills involving mud soak and solarization for three days to accumulate salt, which is a unique process contributing to the selection of highly halophilic microbes related to salt quality and flavor. Herein, the successions of physicochemical properties and bacterial and fungal communities of muds from the saltern were investigated during the processing of mud solarization. The results showed that Na+, Cl−, Mg2+ and total nitrogen were the main factors in explaining the fluctuation of the fungal community, whereas the bacterial community was predominantly determined by Ca2+, total kalium and total phosphorus. During three days of mud solarization, the soil bacterial alpha diversity in the saltern was significantly lower than that of the surroundings, whereas the fungal alpha diversity showed an opposite trend. The bacterial functional groups with the same survival and adaptation strategies remained relatively stable, while the dominant functional type in fungi changed from monotropic to complex trophic mode. Additionally, some unidentified fungi species were increasingly found in mud. The abundances of Saitozyma , Solicoccozyma and Wallemia (Basidiomycota) increased and may contribute to the salt flavor through decomposing cellulose molecules into glucose due to their higher β-glucosidase activity, while the harmful fungal genera including Inocybe and Paraconiothyrium decreased obviously due to the stresses of salinity and solar exposure. These results showed that the traditional salt-making skills associated with mud solarization have selected a high abundance of beneficial halophilic microbes to increase the salt quality and flavor. Our findings not only reveal the underlying mechanisms for the long-history salt-making skills of this 1000-year-old unusual cultural heritage but also are highly valuable for bioprospecting to develop novel halophilic bacteria and fungi for modern chemistry industries. [Display omitted] • Mud-solarization is a critical skill for the selection of highly halophilic microbes. • Successions of bacterial and fungal communities are revealed during the mud-solarization. • Bacterial functional groups with the same survival and adaptation strategies remain stable. • The dominant functional type in fungi changes from monotropic to complex trophic mode. [ABSTRACT FROM AUTHOR]

• MWCNTs and graphite doped solar salt were prepared using the wet method. • The increment/decrement of Cp was analysed systemically. • BET and FESEM analyses were used to study the impact of C p. • Thermal conductivity enhancement was identified using the MTPS method. • Thermal stability was studied using TGA up to 700 °C. A molten salt energy storage has proven to be a promising candidate for medium and high-temperature thermal energy storage (TES) applications. Improving the thermophysical properties, such as specific heat capacity (C p) and thermal conductivity (k) is crucial to deciding the charging/discharging characteristics of the energy storage system. In this study, 1 wt% of two variant carbon allotropes, such as multi-walled carbon nanotubes (MWCNTs) and graphite nanoflakes (GNFs), were dispersed in solar salt (i.e., MWCNTs nanosalt and GNFs nanosalt) using wet preparation method. Thermophysical properties of the prepared nanosalts were evaluated using different analytical techniques and compared with pristine solar salt. The specific heat capacity was measured from 50 °C to 350 °C, and the maximum specific heat capacity enhancement in 1 wt% of MWCNTs dispersed solar salt was 18 %. The enhancement in 1 wt% of GNFs dispersed solar salt was 12.5 % at 200 °C (in solid phase). Similarly, in the liquid phase (at 350 °C), MWCNTs dispersed solar salt improves C p by 6.2 %, while GNFs dispersed solar salt exhibits negligible improvement in C p. Further, a modified transient plane source (MTPS) technique was used to measure the thermal conductivity of both carbon nanosalts in the solid phase (30–100 °C). The maximum thermal conductivity enhancement observed for MWCNTs dispersed solar salt and GNFs dispersed solar salt was 5.8 % and 11.7 %. Finally, thermogravimetric analysis was conducted to evaluate the thermal stability of the MWCNTs nanosalt and GNFs nanosalt at a maximum temperature of 700 °C, and found that the MWCNTs nanosalt show better thermal stability than the GNFs nanosalt. [ABSTRACT FROM AUTHOR]

The protective behaviour of ZrO2-3%molY2O3 sol–gel coatings, deposited with an immersion coating technique on 9Cr-1Mo P91 steel, was evaluated with corrosion monitoring sensors using the electrochemical impedance spectroscopy technique. The tests were carried out in contact with solar salt at 500 °C for a maximum of 2000 h. The results showed the highly protective behaviour of the coating, with the corrosion process in the coated system being controlled by the diffusion of charged particles through the protective layer. The coating acts by limiting the transport of ions and slowing down the corrosive process. The system allowed a reduction in the corrosion rate of uncoated P91 steel. The estimated corrosion rate of 22.62 μm·year−1 is lower than that accepted for in-service operations. The proposed ZrO2-3%molY2O3 sol–gel coatings are an option to mitigate the corrosion processes caused by the molten salts in concentrated solar power plants.

In this study, nanocomposites containing a pre-defined mass ratio of solar salt (NaNO3-KNO3: 60-40 wt.%) dispersed with magnesium oxide (MgO) nanoparticles with nominal sizes of 100 nm were prepared in solid and liquid states. The proposed amounts of sodium nitrate and potassium nitrate were added to certain amounts of ultrapure deionized (DI) water comprising a 5 wt.% concentration of MgO nanoparticles. Afterward, the prepared mixture was placed in a dry oven to mix in a liquid state to obtain well-dispersed nanocomposites. Scanning electronic microscopy (SEM) was conducted to evaluate the uniformity of synthesized, molten salt–based magnesium oxide–nanoparticles, revealing a uniform dispersion. Enthalpy and melting point measurements were performed using differential scanning calorimetry. The experimental results of solar salt–based MgO indicated decreases in melting point and enthalpy by 7% and 12.4%, respectively. The reduction of enthalpy indicated that, with the addition of magnesium oxide to solar salt, the final nanocomposite tends to have more exothermic reactions and enhanced thermal conductivity performance at the melting point. Lower melting points constitute one of the major concerns regarding molten salt–based nanofluids. MgO nanoparticles with a concentration of 5 wt.% have a melting point decreased by 7%. Mass loss and thermal stability measurements were conducted using thermogravimetric analysis (TGA). The experimentally acquired results revealed an increment of decomposition temperature from 734.29°C to 750.73°C, demonstrating the enhancement of thermal stability at high temperatures.

This study reports the behavior of the Ni20Cr alloy in molten nitrate salts. Its behavior was evaluated in the eutectic mixture called Solar Salt (binary salt) and in a ternary mixture (90% Solar Salt and 10% lanthanum nitrate). The addition of lanthanum nitrate was performed to determine if the presence of the La3+ cation could act as a corrosion inhibitor. Through mass loss and potentiodynamic polarization studies, the effects of both electrolytes on the corrosion resistance of the alloy at 300, 400, and 500 °C and at exposure times of 250, 500, 750, and 1000 h were determined. The results showed an increase in the corrosivity of the ternary salt, due to a decrease in its melting point and an increase in the concentration of nitrate ions. However, it was observed that the La3+ cations formed a protective layer (La2O3) on the alloy surface. In both corrosive media, the Ni20Cr alloy showed excellent corrosion resistance, due to its ability to form protective layers of Cr2O3, NiO, and NiCr2O4, in addition to the presence of a layer of La2O3 in the case of the ternary salt.

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Solar salt (60 wt% NaNO3 + 40 wt% KNO3) is widely used in the storage system of concentrated solar power plant. However, the chloride within the molten solar salt can affect the corrosion kinetics of stainless steels and hence affect the overall structural integrity. In this work, the corrosion behavior of 304 and 316L stainless steel (SS) in molten solar salt mixtures with different chloride impurities were investigated by immersion tests at 565 °C. Results show that as the content of chloride in the solar salt increases (up to 1.4 wt%), both 304 and 316L SS keep parabolic corrosion kinetics, and the rate constants increase. In comparison with 304 SS, the better corrosion resistance of 316L SS is ascribed to the higher thickness ratio of FeCr2O4 spinel to oxide scale. In addition, to quantitatively describe the effect of chloride impurity on corrosion kinetics of stainless steels, a novel theoretical model based on Fick's first law is proposed and validated by the experiments. [ABSTRACT FROM AUTHOR]

This study investigates the impact of stabilizing molten salt chemistry on the corrosion behavior of four steel types at temperatures ranging from 570 °C to 620 °C. The research explores the influence of temperature and gas atmosphere on corrosion mechanisms through detailed analysis of molten salt, corrosion rates, and microstructures. Findings reveal that systematic changes in salt chemistry can modify mass transport mechanisms, enabling the development of corrosion mitigation strategies even at extreme temperatures. This discovery marks a significant breakthrough in the advancement of Solar Salt-based storage systems for high-temperature applications, facilitating the utilization of renewable energy sources. • Comparison of state-of-the-art (570 °C) vs. enhanced temperatures of 620 °C in Solar Salt. • Impact of Gas phase composition on Salt Stability and Corrosion. • Analysis of both attacking medium (molten salt) and metal specimens. • Corrosion Analysis by Mass Gain, Descaling, Surface- and Cross-section analysis. • Derivation of corrosion mechanisms for decomposed vs. stabilized Solar Salts. [ABSTRACT FROM AUTHOR]

• Coaxial cylindrical viscometry theory, emphasizing calibration for real system deviations. • High temperature samples require thermal expansion correction from calibration. • Thermal expansion has significant bias on viscosity measurements. • Solid materials with high expansion and highly viscous fluids are most affected. Modern industrial applications often require accurate measurements of high temperature fluids such as molten salts. However, the commonly used coaxial cylindrical viscosity measurement method has an intrinsic bias when the calibration fluid and test fluid are run at significantly different temperatures due to the thermal expansion of solid container materials. In this study, we take a novel approach by deriving and quantifying the thermal expansion bias, β , for various common container materials using fluid dynamics arguments, thermal expansion data, and empirical methods. To the best knowledge of the authors, this work represents the first quantification of the thermal expansion bias and fills a significant gap in the current understanding. To validate our findings, we conducted an experiment on solar salt and applied the derived thermal expansion correction to the results, comparing them to independent studies. The results highlight the importance of the thermal expansion correction, which increases with rising temperature, particularly in high thermal expansion materials such as stainless steel, which has a bias of ∼6 % at 1000 °C. Our contribution provides valuable insights into the accurate measurement of high temperature fluids and offers a substantial advancement in addressing the thermal expansion bias, setting a new standard for future research in this field. [ABSTRACT FROM AUTHOR]

• This paper systematically explored the influence of Cl− impurity on the thermophysical properties of Solar Salt, including liquidus temperature, density, viscosity and thermal stability. • Cl− has almost no effect on the density, viscosity and thermal stability of the mixed molten salt system at 400 °C, but at 565 °C, Cl− will promote the volatilization of components. • Studies have shown that the upper limit of Cl− for maintaining good thermal performance of Solar Salt is preferably less than 0.1 wt%. Molten nitrate salts are widely used as heat transfer and energy storage medium in Concentrated Solar Power (CSP) systems. Solar Salt (60 wt% NaNO 3 -40 wt% KNO 3) is the commercial binary molten nitrate salt, which is the preferred energy storage material with high density, high specific heat, low melting point, high thermal stability, and low vapor pressure. This paper explored the effects of impurity Cl− on the thermophysical properties of Solar Salt, including liquidus temperature, density, viscosity, and thermal stability. The results showed that Cl− can significantly reduce the liquidus temperature, and when Cl− was less than 0.5 wt%, the liquidus temperature of molten salt system decreased within 1 °C. On the other hand, Cl− had little effect on the density, viscosity and thermal stability of the mixed molten salt system at 400 °C, but at high temperature Cl− will promote the volatilization of components. By analyzing the thermostatic stability at 565 °C, it was found that the total mass loss changes less than 0.3% when Cl− was less than 0.01 wt%. After comprehensive analysis, the conclusion is that the upper limit of Cl− is preferably less than 0.1 wt% for keeping good thermal performances of Solar Salt. [ABSTRACT FROM AUTHOR]

Extremely halophilic archaea (haloarchaea) belonging to the phylum Euryarchaeota have been found in high-salinity environments. In this study, Halarchaeum sp. CBA1220, Halorubrum sp. CBA1229, and Halolamina sp. CBA1230, which are facultatively oligotrophic haloarchaea, were isolated from solar salt by culture under oligotrophic culture conditions. The complete genomes of strains CBA1220, CBA1229, and CBA1230 were sequenced and were found to contain 3,175,875, 3,582,278, and 3,465,332 bp, with a G + C content of 68.25, 67.66, and 66.75 mol %, respectively. In total, 60, 36, and 33 carbohydrate-active enzyme genes were determined in the respective strains. The strains harbored various genes encoding stress-tolerance proteins, including universal stress proteins, cold-shock proteins, and rubrerythrin and rubrerythrin-related proteins. The genome data produced in this study will facilitate further research to improve our understanding of other halophilic strains and promote their industrial application. [ABSTRACT FROM AUTHOR]

• A first of its kind 1 MW concentrating solar power plant in a desert environment. • Experimental demo of the solar salt tech in parabolic trough collectors up to 550 °C. • Testing operation procedures and methods in a stand-alone plant with molten salts. • Analysis of heat losses, overall solar field performances and management issues. • Interplay between a gas-fired back-up heater and the concentrating solar field. The use of molten salt as Heat Transfer Fluid (HTF) in linear concentrators to reach temperatures >500 °C has received increasing interest in the CSP sector. So far, some experiences have been carried out on small test loops, while results obtained on larger (pre-commercial) plants have not been thoroughly published in the open literature, yet. This paper reports results obtained and lessons learned during the experimental operation of a CSP plant using Molten Salts (MS) as HTF in linear Parabolic Trough (PT) collectors. This demonstration has been carried out in the framework of the EU project MATS and refers to a stand-alone and fully-integrated 1 MWe CSP plant built in a typical desert environment in Egypt. With about 10,000 m2 mirrors' surface, the MS-PT solar field of MATS plant is the first of its kind and size. The solar field was in operation for more than 2500 h with solar salt circulation under different conditions, including start-up, draining, night circulation and solar tracking tests. The technical issues dealing with the management of a MS-PT solar field (and, in general, in linear concentrators) are discussed. Results demonstrated the reliability of the MS-PT technology for future exploitation on commercial scale plants. [ABSTRACT FROM AUTHOR]

• Purge flow with nitrous gases stabilizes the molten salt up to 620 °C. • Experiments demonstrate reaction equilibria with oxide ions. • Evaluation of reaction equations emphasizes the effect of N 2 formation. Thermal energy storage systems are integrated in concentrating solar power plants to improve the flexibility of the electricity generation. Commonly, the liquid storage material Solar Salt, a nitrate salt mixture, is applied to transport and store solar thermal energy. The lifetime and the temperature range of Solar Salt in the storage units are restricted by decomposition reactions of the material. Oxide ion formation is one of the fundamental issues. So far, it has not been proven if oxide ion formation can be prevented by addition of gaseous reaction products to the gas atmosphere. Also, a reliable reaction equation for the oxide ion formation is missing. In the presented experiments, molten salt at 600 and 620 °C is purged with a gas mixture of nitrogen, oxygen, and nitrous gases. Post-analysis of salt samples reveals stabilizing effects, depending on the purge gas compositions. Chemical equilibrium of the oxide ion forming reaction is demonstrated. It is proven that oxide ion formation can be controlled and suppressed. Reaction equations are evaluated and selected in order to quantify the reaction thermodynamics. The results contribute to recommendations for operating conditions and gas handling in storage systems of solar thermal power plants, which finally ensure reliable and constant material properties for extended lifetime and high temperatures. [ABSTRACT FROM AUTHOR]

Food fraud, including adulteration, addition, tampering, and misrepresentation of food ingredients and packaging for improper economic profit, has been global concerns affecting public health and safety. In South Korea, counterfeit expression of solar salt has been a problem causing improper economic profit, especially for those products produced from China, but labeled as 'domestics'. In this study, we were tried to discriminate geographical origins of solar salt between South Korea and China through various analytical techniques, the determination of moisture and sodium chloride contents, multi-elemental analysis, and isotope analysis. With the application of a statistical analysis, more than 93.3% of discrimination capability of positive classification was achieved in this study. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) is an efficient solution for improving the dispatchability of Concentrated Solar Power (CSP) plants. A system, consisting of two tanks with Solar Salt (NaNO 3 60% wt. and KNO 3 40% wt.) is commonly used. However, the investment cost of this technology is very high, due to the huge amount of salts required (thousands of tons). A pronounced interest is evident for improving the thermophysical properties of molten salts by adding small amounts of nanoparticles in order to reduce the mass of molten salts at CSP. At the moment, the effect of nanoparticle addition on corrosion of container materials is poorly explored. In particular, there are no works regarding the dynamic effect of nanoparticles on the corrosivity of molten salts. In this work we present first ever dynamic corrosion tests for Solar salt doped with alumina nanoparticles (1% wt.). Carbon Steel A516 and SS347, used in double-tank system, were tested. Corrosion rates were 94.8 μm yr−1 and negligible respectively (1000 h, 385 °C). Detailed examination of construction materials revealed incorporation of nanoparticles into the corrosion layer and considerably lower corrosion rate as compared to the previously reported work on the nanoparticles-free Solar salt. • A 1000 h Dynamic Corrosion Test of A516 and SS347 in Solar Salt was done. • Dynamic corrosion rate for A516 kept constant at 94.8 μm year−1 at 386 °C. • A516 Corrosion rate was lower than expected in dynamic conditions. • Al 2 O 3 nanoparticles may have a protective influence on corrosion. • Dynamic corrosion rate for SS347 was found to be negligible at 386 °C. [ABSTRACT FROM AUTHOR]

The main aim of the present research was to investigate the effects of a ternary nitrate salt (NaNO3–KNO3–LiNO3) on high-temperature corrosion behaviour of stainless steel 321 (SS 321) in a parabolic trough collector in a concentrating solar power system. The corrosion behaviour of SS − 321 was examined in a ternary salt (LiNO3 (25 wt-%)-NaNO3 (25 wt-%)-KNO3 (50 wt-%)) at 400°C and 550°C for 250 h, 500 h and 1000 h, and the obtained findings were then compared with the results of a solar salt ((NaNO3 (60 wt-%)-KNO3 (40 wt-%)). In order to determine the quantitative corrosion behaviour of SS − 321, the results of immersion tests and microstructural investigations obtained through scanning electron microscopy and energy-dispersive X-ray microanalysis were also considered. It was found that the addition of lithium nitrate (LiNO3) to solar salt formed resistant oxide layers on the surface of SS 321 and subsequently, increased its corrosion resistance ability. [ABSTRACT FROM AUTHOR]

• Thermal decomposition of nitrate salts in CSP TES systems is investigated. • Impurities of solar salts are considered. • The impurity Mg(NO 3) 2 is the main source of NOx emissions in solar salts at medium temperature. • NOx emissions mainly happen during the commissioning of the plant due. • This NOx production can be handled by vents and abatement systems if it is needed. Nowadays, the most matured thermal energy storage (TES) technology for Concentrated Solar Power (CSP) plants is the use of molten solar salts (60 wt% NaNO 3 – 40 wt% KNO 3), but the thermal decomposition of nitrate salts can result in changes in the composition of molten salts or potential risks of NOx emissions. Up to now, all studies on the decomposition of nitrates in TES systems focus on the effect of the effect of sodium and potassium nitrates in contact with the container material and the NOx emissions formation, but none investigate the effect or contribution of impurities in it. Moreover, although the chemistry of the nitrates decomposition is well known, there is a big uncertainty in commercial solar plants on the production rate of NOx. The only cation in nitrates from mining origin is magnesium, and since it occurs as nitrate, it does contribute to NOx formation. This paper studies the effect of such impurity in the thermal decomposition of the solar salt. The results show that the impurity Mg(NO 3) 2 is the main source of NOx emissions in solar salts during the commissioning of the plant due to its thermal decomposition during the melting process. But as described this NOx production can be handled by vents and abatement systems if it is needed. [ABSTRACT FROM AUTHOR]

In this study, nanocomposites containing a pre-defined mass ratio of solar salt (NaNO3-KNO3: 60-40 wt.%) dispersed with magnesium oxide (MgO) nanoparticles with nominal sizes of 100 nm were prepared in solid and liquid states. The proposed amounts of sodium nitrate and potassium nitrate were added to certain amounts of ultrapure deionized (DI) water comprising a 5 wt.% concentration of MgO nanoparticles. Afterward, the prepared mixture was placed in a dry oven to mix in a liquid state to obtain well-dispersed nanocomposites. Scanning electronic microscopy (SEM) was conducted to evaluate the uniformity of synthesized, molten salt-based magnesium oxide-nanoparticles, revealing a uniform dispersion. Enthalpy and melting point measurements were performed using differential scanning calorimetry. The experimental results of solar salt-based MgO indicated decreases in melting point and enthalpy by 7% and 12.4%, respectively. The reduction of enthalpy indicated that, with the addition of magnesium oxide to solar salt, the final nanocomposite tends to have more exothermic reactions and enhanced thermal conductivity performance at the melting point. Lower melting points constitute one of the major concerns regarding molten salt-based nanofluids. MgO nanoparticles with a concentration of 5 wt.% have a melting point decreased by 7%. Mass loss and thermal stability measurements were conducted using thermogravimetric analysis (TGA). The experimentally acquired results revealed an increment of decomposition temperature from 734.29°C to 750.73°C, demonstrating the enhancement of thermal stability at high temperatures. [ABSTRACT FROM AUTHOR]

Composites comprising MgO nanoparticles as the dispersed phase and solid phase solar salt as the matrix have been prepared through solid-state mixing. The inclusion of MgO nanoparticles had very little influence on the solid-liquid phase change temperature and the latent heat of solar salt. However, the solid phase thermal conductivity of MgO-solar salt was elevated by 17.5% with the dispersion of 0.25 wt% MgO nanoparticles. The clustered nature of MgO nanoparticles and their presence at the interface between solar salt particles with reduced resistance might have contributed to the solid phase thermal conductivity enhancement for this composition of the composite. The maximum enhancement in specific heat of MgO-solar salt composite (14%) was observed at another composition (1 wt%), revealing the requirement of different composition for optimum thermal conductivity and optimum specific heat. The solidification time for 0.25 wt% composite was 30% lower than that of the solar salt. Also, the rate of discharge from 0.25 wt% composite was 42.4% higher than that of solar salt. The corresponding data for the composite containing 2 wt% MgO are 13.8% and 33.8% respectively. These composites can be used in latent heat thermal energy storage systems. • MgO-solar salt composite phase change material prepared and characterized. • 0.25 wt% composite showed needle-like structures at the MgO-solar salt interface. • Different optimum MgO concentrations for maximum 'k' and 'c p ' enhancement. • Maximum thermal conductivity enhancement of 17.5% for composite with 0.25 wt% MgO. • 30% reduction in solidification time for 0.25 wt% MgO-solar salt composite. [ABSTRACT FROM AUTHOR]

Molten salt is an important medium for thermal storage, which is widely used in concentrating solar power plants. The addition of nanomaterials becomes an effective way to overcome the unsatisfactory thermo-physical properties of pure molten salt. In the present study, molecular dynamics simulations are performed to investigate the influence of SiO 2 nanoparticle on the thermo-physical properties of solar salt. Two kinds of models of solar salt nanofluids, i.e., different sizes of boxes with the same size of nanoparticles and the same size of boxes with different sizes of nanoparticles, at the mass fractions of nanoparticles of 1%, 2%, 3%, 4%, 5%, and 6% are built to analyze the size effects on the simulation results. The effects of SiO 2 nanoparticles on the specific heat capacity, viscosity and thermal conductivity of the composited thermal energy storage (CTES) materials are studied extensively. The microscopic mechanism of the thermo-physical properties variation is revealed by calculating the mean square displacement (MSD), diffusion coefficient, Radial distribution function (RDF) and energy of systems. It is proved that the calculations of shear viscosity, specific heat capacity and MSD do not have size effect. An enhancement as large as 2.05% in the specific heat capacity of the CTES materials has been found with 2 wt% addition of nanoparticles. The presence of the compressed layer on the surface of the nanoparticles might be responsible for the enhancement of the specific heat capacity according to the calculation of RDF. It is also found that with the increase of mass fraction of nanoparticles, the viscosity of the CTES materials increases due to the enhancement of interaction between ions in the base fluid. Therefore, in order to avoid the negative effects caused by excessive viscosity of solar salt in thermal energy storage system, it is suggested to consider the appropriate amount of nanoparticles. The addition of SiO 2 nanoparticles enhances the thermal conductivity of the CTES materials with the increase of mass fraction of nanoparticles. It is demonstrated that the enhancement of ion collision frequency in the base fluid is the main factor for the enhancement of thermal conductivity by the addition of SiO 2 nanoparticles. • Thermo-physical properties of molten salt with nanoparticles are investigated with molecular dynamics simulations. • Viscosity of nanocomposite increases due to strengthening of the interaction between cation and anion in base fluid. • Specific heat capacity enhancement is attributed to the compressed layer with more K+ ions on surfaces of nanoparticles. • Strengthening of ion collisions are demonstrated for enhancement of thermal conductivity. [ABSTRACT FROM AUTHOR]

Abstract This study assessed the behaviour of a constructive material in CSP plants, namely ferritic-martensitic steel, with molten NaNO 3 /KNO 3 (60/40 wt%), also known as Solar Salt. To this end, EIS is presented as a suitable technique to evaluate and monitor the resistance of this material to Solar Salt at 580 °C. Tests were performed up to 1000 h and results were also supported by gravimetric and microstructural characterisation of the samples and chemical analysis of the salt. According to the EIS results, a diffusion-controlled reaction occurred during contact, which indicates that the corrosion process follows a porous layer mechanism. The results also indicated variations in corrosion layer thickness and instability of the salt during the whole test. The EIS results were also used for determining the corrosion rate, this being estimated at ~300 µm year−1. Results obtained by EIS were in line with the behaviour of P91 steel as measured by gravimetric, morphological and chemical analysis. Thus, the results confirm the suitability of EIS for monitoring corrosion processes in real-time of constructive materials in CSP plants. Highlights • EIS was used to monitor the corrosion resistance of a constructive material in CSP. • The behaviour of P91 in Solar Salt at 580 °C was evaluated and monitored for 1000 h. • EIS results indicated that the corrosion process follows a porous layer mechanism. • The EIS results estimated a corrosion rate of P91 at ~300 µm year−1. • Results obtained by EIS were in line with the ones obtained by other techniques. [ABSTRACT FROM AUTHOR]

Thermal Energy Storage (TES) based on molten salts is thought to play a major role for the transition from fossil fuels to renewable energy carriers in the future. Solar Salt, a mixture of NaNO 3 –KNO 3 is currently the state-of-the-art heat transfer and storage material in Concentrating Solar Power (CSP) plants which produce electricity from a Rankine cycle with steam temperatures up to 550 °C. To allow a technology transfer and adapt Solar Salt based TES systems to modern, high temperature Rankine cycles (e.g. T steam > 600 °C), the thermal stability of Solar Salt needs to be increased well above 615 °C. At these temperatures, the formation of nitrites, which depends on the oxygen partial pressure above the melt, needs to be suppressed effectively to prevent further decomposition into corrosive oxide ions. In this work, the thermodynamics of the nitrite-forming reaction at different oxygen partial pressure are explored in a temperature range up to 650 °C from isothermal experiments in the 100 g-scale and limitations of the ideal description are revealed. The measured apparent oxide ion formation rates at 100 g-scale were below previous findings. The activation energy found was 60 ± 15 k J / m o l and the preexponential factor 1 * 10 − 5 ± 0.00005 s − 1 . The effect of closing the storage system in terms of gas and salt phase at 645 °C are also explored to understand if and how pressure formation and oxygen release correlate. The results of this work finally contribute to an understanding of the decomposition reactions of Solar Salt at previously untouched temperatures. • Equilibrium data (salt composition) for Solar Salt from 500 to 650 °C is presented. • Thermophysical data is given and previous literature studies are critically reviewed. • Kinetic data for the formation of corrosive species are extracted and implications are discussed. • A simple strategy to prevent pressure built up in a closed molten salt system at 650 °C is introduced with experimental data. [ABSTRACT FROM AUTHOR]

Coastal areas in Minami-soma City, Fukushima, Japan, were seriously damaged by radioactive contamination from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident that caused multiple pollution by tsunami and radionuclide exposure, after the Great East Japan Earthquake, on 11 March 2011. Some areas will remain no-go zones because radiation levels remain high. In Minami-soma, only 26 percent of decontamination work had been finished by the end of July in 2015. Here, we report the characterization of microbial mats and salt found on flooded paddy fields at Karasuzaki, Minami-soma City, Fukushima Prefecture, Japan which have been heavily contaminated by radionuclides, especially by Cs (134Cs, 137Cs), 40K, Sr (89Sr, 90Sr), and 91 or 95Zr even though it is more than 30 km north of the FDNPP. We document the mineralogy, the chemistry, and the micro-morphology, using a combination of micro techniques. The microbial mats were found to consist of diatoms with mineralized halite and gypsum by using X-ray diffraction (XRD). Particular elements concentrated in microbial mats were detected using scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS) and X-ray fluorescence (XRF). The objective of this contribution is to illustrate the ability of various diatoms associated with minerals and microorganisms which are capable of absorbing both radionuclides and stable isotopes from polluted paddy soils in extreme conditions. Ge semiconductor analysis of the microbial mats detected 134Cs, 137Cs, and 40K without 131I in 2012 and in 2013. Quantitative analysis associated with the elemental content maps by SEM-EDS indicated the possibility of absorption of radionuclide and stable isotope elements from polluted paddy soils in Fukushima Prefecture. In addition, radionuclides were detected in solar salts made of contaminated sea water collected from the Karasuzaki ocean bath, Minami-soma, Fukushima in 2015, showing high Zr content associated with 137Cs and 40K without 131I. The results obtained here provide evidence of the ability of microorganisms to grow in this salty contaminated environment and to immobilize radionuclides. It is possible that the capability of radioactive immobilization can be used to counteract the disastrous effects of radionuclide-polluted paddy soils.

This paper is focused on the characterisation and demonstration of Newtonian behaviour of salt at both high and low shear rate for sodium and potassium nitrate eutectic mixture (60/40) ranging from 250 °C to 500 °C. Analysis of published and experimental data was carried out to correlate all the numbers into one meaningful 4th order polynomial equation. Addition of a low amount of copper oxide nanoparticles to the mixture increased viscosity of 5.0%–18.0% compared to the latter equation.