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For future concentrating solar power (CSP) plants, a levelised cost of electricity (LCOE) of $0.06/kWhe is targeted, with their greatest value being their low-cost storage. However, low-cost storage is not the only factor that should be considered when selecting storage systems as this choice can significantly impact other parts of the CSP plant, potentially leading to a higher LCOE. Therefore, the current study aims to economically investigate the integration of various storage system designs into a sodium/sCO2 CSP plant. Using component cost targets coupled with storage cost estimates, the impact of storage design conditions could be evaluated. From this analysis it was found that while a molten chloride two-tank system had the lowest storage cost, integration led to a higher or comparable LCOE to other studied designs. Therefore, it is important that future storage designs and studies account for the complete CSP system when system configurations and technologies are proposed. Refereed/Peer-reviewed

The eutectic Na2CO3-Li2CO3 salt is widely used as an electrolyte in the Molten Carbonate Fuel Cell because of its high both ionic conductivity and operating temperature. The major objective of this study was to investigate the thermal stability of the binary salt as a phase change material for thermal energy storage through thermal decomposition analysis in different environments and thermal cycling. The composition of the binary salt was determined using FactSage software 6.4 and its thermophysical properties were experimentally investigated using a Simultaneous Thermal Analyzer and X-Ray Diffraction. The results show that the eutectic Na2CO3-Li2CO3 salt has a melting/solidification point of 498.3 ± 0.1 °C/483.9 ± 0.1 °C, with a heat of fusion of 330.8 ± 0.6 J/g and heat of solidification of 329.2 ± 0.3 J/g. The thermal decomposition analysis indicates that the eutectic molten salt has good thermal stability in a CO2 environment without weight loss at temperatures up to 600 °C. However, 0.8% weight loss is observed at 500 °C in a N2 atmosphere, which is associated with the thermal decomposition of the eutectic salt to produce corresponding metal oxides and CO2. The CO2 environment could inhibit the thermal decomposition, thus resulting in higher thermal stability of the binary salt in CO2 than when in N2. Hence, an operating environment has a large effect on the thermal stability of the eutectic Na2CO3-Li2CO3 salt. The eutectic salt exhibits high thermal stability in CO2 after 500 thermal cycles with little change in its thermal properties compared with the initial sample. Refereed/Peer-reviewed

In the current study two phase change materials have been initially characterised as potential high temperature phase change materials (PCM) for thermal energy storage. Thermophysical properties such as melting/freezing point, latent heat, and specific heat capacity were determined using differential scanning calorimetry (DSC). Results from the uncycled PCMs show a melting point of 541.98 ± 0.15 °C and a latent heat of 164.96 ± 3.83 J/g for the lower temperature PCM (BaCl2-KCl-NaCl), and 706.92 ± 0.34 °C and 133.14 ± 3.55 J/g for the higher temperature PCM (K2CO3-Na2CO3). This largely compares well with the melting points and latent heats provided in literature. Theoretical predictions of other properties such as solid and liquid density, liquid thermal conductivity, and viscosity were also estimated. Lastly, samples of the PCM were also cycled up to 200 times with the melting point and latent heat measured. From the cycling results, the melting point and latent heat of samples cycled 200 times show almost no change. The measured melting point and latent heat after 200 cycles was found to be 541.30 ± 0.16 °C and 161.64 ± 2.60 J/g, respectively, for the low temperature PCM.Similarly, the higher temperature PCM showed good cycling stability after 200 cycles with a melting point and latent heat of 704.62 ± 0.29 °C and 135.42 ± 3.59 J/g, respectively. Overall, it was found that the PCMs investigated in the current study show promising results to be considered as high temperature energy storage materials. Refereed/Peer-reviewed

In this work, the eutectic Na2CO3-NaCl molten salt was investigated as a new high temperature phase change material for solar thermal energy storage. The composition of the eutectic binary salt was determined with the aid of FactSage software and its thermophysical properties were investigated using a Simultaneous Thermal Analyzer (STA) and X-Ray Diffraction (XRD). Inductively coupled plasma analysis has shown that the composition of the as-prepared sample is consistent with the nominal one. The STA results exhibit that the melting point of the eutectic salt is 637.0 °C and its heat of fusion is 283.3 J/g whereas its specific heat is a function of temperature, which all are in agreement with the theoretical values determined by the FactSage software. The thermal stability analysis indicates that the eutectic molten salt has good thermal stability without weight loss in a CO2 environment at temperatures below 700 °C, compared with 0.51% weight loss in a N2 atmosphere. The weight loss observed in the latter, is most likely to be due to the salt's decomposition at high temperature. The thermophysical properties of the salt such as melting temperature, latent heat of fusion and solidification, varied marginally after 50 and 100 thermal cycle tests. This demonstrates that the eutectic Na2CO3-NaCl salt is a promising high temperature phase change material when used in a CO2 environment or encapsulation. Refereed/Peer-reviewed

The eutectic Na2CO3-NaCl molten salt was investigated as a new high temperature phase change material for solar thermal energy storage. The composition of the eutectic binary salt was determined with the aid of FactSage software and its thermophysical properties were investigated using a Simultaneous Thermal Analyzer, X-Ray Diffraction and a Scanning Electron Microscope. Eutectic Na2CO3-NaCl salt shows higher measurement values in a CO2 atmosphere than these in a N2 atmosphere in terms of heats of both fusion and solidification. Thermal stability analysis indicates that the eutectic molten salt has higher thermal stability in a CO2 environment without weight loss at temperatures below 700 °C compared with 0.51% weight loss at the melting point around 640 °C in a N2 atmosphere. The weight loss observed in the latter, is most likely to be due to the salt's decomposition at high temperature. The thermophysical properties of the salt such as melting temperature, heats of both fusion and solidification, as well as the phase identification and phase morphology varied slightly after 100:200 and 300 thermal cycle tests. Therefore, the eutectic Na2CO3-NaCl salt has a good thermal and phase stability. It therefore is a promising high temperature phase change material when used in a CO2 environment. Refereed/Peer-reviewed

The use of paraffin, salts and salt hydrates as phase change materials (PCMs) have been researched extensively and used in a number of commercial applications. However, metals and metal alloys, which possess a high storage density on a volume basis as well as a substantially higher thermal conductivity, has received much less attention. This paper discusses the considerations for the use of metal and metal alloys as phase change materials for high temperature thermal storage applications, as well as summarises the literature on the limited research in this area. Although some pure metals and metal alloys present interesting thermal properties to be used as PCMs in thermal storage systems, there is a lack of understanding on the implications of the metallurgical aspects related to the melting and solidification of these materials under thermal cycling at high temperatures. The main issues to be considered include vapour pressure, undercooling, corrosion, segregation, changes in composition and microstructure, changes in thermal properties and undesired reactions. Further research is needed before these materials can be used as PCMs in thermal energy storage systems in industry. The research leading to these results has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under grant agreement n° PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union's Horizon 2020 Research and Innovation Program under grant agreement No 657466 (INPATH-TES). The authors would like to thank the Catalan Government for the quality accreditation given to their research groups GREA (2014 SGR 123) and DIOPMA (2014 SGR 1543), and also the Spanish Government for the projects ENE2015-64117-C5-1-R and ENE2015-64117-C5-2-R (MINECO/FEDER, UE). Dr. Camila Barreneche would like to thank Ministerio de Economia y Competitividad de España for Grant Juan de la Cierva, FJCI-2014-22886. This paper was produced with support from the “Premier’s Research Industry Fund - International Research Grant Program” (IRGP 33) funded by the Government of South Australia.

Considerable effort has been devoted to the characterization of thermal properties of the different types of materials that can be used as thermal energy storage (TES) media, but scarce literature exists concerning the materials to manufacture the tanks that can be used to contain these storage media. One of the main concerns when selecting the most suitable material for these tanks is its resistance to corrosion due to molten salts that constitute the TES system. Dynamic gravimetric analysis is a newly proposed method for the study of corrosion on metals, which optimizes the standard procedure described by ASTM G1–03. The new technique avoids the direct handling of samples, so more accurate values can be obtained. In this work, the resistance to corrosion of AISI 316 stainless steel samples in contact with commercial grade molten salts of the Li2CO3-Na2CO3-K2CO3 system, at 600 °C for different exposure times, has been determined by using this new methodology. The results show that the initial corrosion rate is lower at higher amounts of lithium carbonate present in the molten salts mixture. Refereed/Peer-reviewed