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A thermal conductivity probe for high temperature (HT-TCP) has been built and tested. Its design and construction procedure are adapted from the ambient temperature thermal conductivity probe (AT-TCP) due to the good performances of this last device. The construction procedure and the preliminary tests are accurately described. The probe contains a Pt wire as heater and a type K thermocouple (TC) as temperature sensor, and its size are so small (diameter 0.6 mm and length 60 mm) to guarantee a length to diameter ratio of about 100. Calibration tests with glycerol for temperatures between 0°C and 60°C have shown a good agreement with literature data, within 3%. First tests on a ternary salt (18% in mass of NaNO3, 52% KNO3, and 30% LiNO3) at 120°C and 150°C, have given good results: an agreement was found with the thermal conductivity of the standard solar salt (60% NaNO3, 40% KNO3), even if the data for this last have been extrapolated, being it solid at those temperatures. Unfortunately, at the higher temperature tested (200°C), the viscosity of the salt highly decreases, and free convection starts, making the measurements unreliable.

The objective of this work is to improve the quality of performances and procedures regarding laboratory studies, and to summarize and make available the presented or investigated data about the main characteristics of each feasible HTF (heat thermal fluid)/HSM (heat storage material) for CSP (concentrating solas power) applications. The first necessary step for this work development is to collect and classify, according to shared evaluation criteria, the currently available fluids feasible to be used as HTF and/or HSM. The following materials are taken into account Alkaline/alkaline earth metals nitrate/nitrite mixtures Thermal oils Solid Media Storage Technology (as HSM) PCM (phase change materials) (as HSM) Gas/steam (as HTF, pressurized liquid water also proposed for buffer storage systems) Liquid metals Nanoparticles materials (nanoparticles additivate to HTF/HSM) Thermochemical heat storage The following characteristics have been considered for the rating Environmental safety Risk for human health Freezing temperature Upper thermal stability point Thermo-physical properties (density, viscosity, heat capacity, thermal conductivity) Construction materials compatibility Material cost Cost of handling equipment and system Efficiency of the power block associated (for HSM) The obtained results are reported and discussed.

Concentrated solar power (CSP) technologies are among the most interesting routes for the production of electrical energy from renewable sources. The main problem related to a large diffusion of these systems is the discontinuity of the solar irradiation. In order to overcome this issue, storage thermal energy systems have been proposed and developed. In this way the levelised energy cost (LCOE) of the electricity generation can be decreased and a better integration of CSP plants in the electrical distribution grid can be obtained. The present report is concerned with fluids for thermal energy storage, as materials for sensible heat thermal storage have already discussed in other reports, the task has been focused on latent heat storage (LHTES), which requires the use of phase change materials (PCM). The report also deals with innovative thermal fluids, and, in particular, storage materials charged with nanoparticles. For these reasons, this report is divided into two main section: a general description of PCMs for latent heat storage and a state of the art review about the employment of nanoparticles.

The objective of this work is to improve the quality of performances andprocedures regarding laboratory studies, and to summarize and make available the presented orinvestigated data about the main characteristics of each feasible HTF (heat thermal fluid)/HSM (heat storage material) for CSP (concentrating solas power) applications.The first necessary step for this work development is to collect and classify, according to sharedevaluation criteria, the currently available fluids feasible to be used as HTF and/or HSM. The following materials are taken into account Alkaline/alkaline earth metals nitrate/nitrite mixtures Thermal oils Solid Media Storage Technology (as HSM) PCM (phase change materials) (as HSM) Gas/steam (as HTF, pressurized liquid water also proposed for buffer storage systems) Liquid metals Nanoparticles materials (nanoparticles additivate to HTF/HSM) Thermochemical heat storage The following characteristics have been considered for the rating Environmental safety Risk for human health Freezing temperature Upper thermal stability point Thermo-physical properties (density, viscosity, heat capacity, thermal conductivity) Construction materials compatibility Material cost Cost of handling equipment and system Efficiency of the power block associated (for HSM) The obtained results are reported and discussed.

The present report summarizes the available data in literature about the main characteristics of each feasible HTF (heat transfer fluid) and HSM (heat storage media) for CSP (concentrating solar power) applications. The report is divided into three sections: A state of the art about NO3-/NO2- mixtures containing Na/K/Li/Ca availability of multicomponent phase diagrams thermal stability of nitrates/nitrites mixtures addition of different anions, especially considering halides

A thermal conductivity probe for high temperature (HT-TCP) has been builtand tested. Its design and construction procedure are adapted from the ambient temperature thermalconductivity probe (AT-TCP) due to the good performances of this last device. The construction procedureand the preliminary tests are accurately described. The probe contains a Pt wire as heater and a type K thermocouple (TC) as temperature sensor, and its size are so small (diameter 0.6 mm and length 60 mm) toguarantee a length to diameter ratio of about 100. Calibration tests with glycerol for temperaturesbetween 0°C and 60°C have shown a good agreement with literature data, within 3%. First tests on a ternary salt (18% in mass of NaNO3, 52% KNO3, and 30% LiNO3) at 120°C and 150°C,have given good results: an agreement was found with the thermal conductivity of the standard solar salt(60% NaNO3, 40% KNO3), even if the data for this last have been extrapolated, being it solid at thosetemperatures. Unfortunately, at the higher temperature tested (200°C), the viscosity of the salt highlydecreases, and free convection starts, making the measurements unreliable.

The present report summarizesthe available data in literature about the main characteristics of each feasible HTF (heat transfer fluid) and HSM (heat storage media) for CSP (concentrating solar power) applications.The report is divided into three sections: A state of the art about NO3-/NO2- mixtures containing Na/K/Li/Ca availability of multicomponentphase diagrams thermal stability of nitrates/nitrites mixtures addition of different anions, especially considering halides

Concentrated solar power (CSP) technologies are among the most interesting routes for the production of electrical energy from renewable sources. The main problem related to a large diffusion of these systems is the discontinuity of the solar irradiation. In order to overcome this issue, storage thermal energy systems have been proposed and developed. In this way the levelised energy cost (LCOE) of the electricity generation can be decreased and a better integration of CSP plants in the electrical distribution grid can be obtained. The present report is concerned with fluids for thermal energy storage, as materials for sensible heat thermal storage have already discussed in other reports, the task has been focused on latent heat storage (LHTES), which requires the use of phase change materials (PCM). The report also deals with innovative thermal fluids, and, in particular, storage materials charged with nanoparticles. For these reasons, this report is divided into two main section: a general description of PCMs for latent heat storage and a state of the art review about the employment of nanoparticles.