100,438 research outputs found
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Predictive model for the phase diagrams of ternary mixtures composed of calcium, lithium and sodium/potassium nitrates
No full textThe study and development of multi-component alkaline nitrates systems is of utmost interest to investigate low melting and low cost HTFs and HSMs, to be used in CSP plants. At this aim, several binary and ternary mixtures have been proposed as feasible and promising materials in the scientific literature. In order to evaluate the most feasible HTF and HSM, the simulation campaign proposed in this work was focused on economical and readily available compounds, ruling out rare and costly species. A semi-predictive model, based on the regular solution theory, was employed to draw the ternary phase diagrams of LiNO3/NaNO3/Ca(NO3)2 and LiNO3/KNO3/Ca(NO3)2, from which it was possible to select the lower melting zones and the compositions. The binary sub-systems were the starting point for the employed approach. The results showed a good agreement with literature experimental data, and new low melting compositions were simulated and experimentally validated. It is noteworthy that it was possible to identify in great detail the zones of the two ternaries presenting the lowest freezing points and this can allow the design of interesting and cost-effective low melting mixtures
Thermo-physical investigation of low melting HFT and HSM containing calcium nitrate
No full textDespite its large interesting as component for low melting HTF and HSM, very few thermodynamics information is available regarding calcium nitrate and its mixtures. In this paper the binaries between Ca(NO3)2 and both NaNO3 and KNO3 are experimentally investigate by DSC and Neutron scattering. The results show that the solid phase of the binaries is composed by a solid solution of single nitrates. The DSC pattern and the eutectic point were modeled by the regular solution theory and the fitting parameters are reported. © 2019 Author(s)
Assessment and perspectives of heat transfer fluids for csp applications
No full textDifferent fluid compositions have been considered as heat transfer fluids (HTF) for concentrating solar power (CSP) applications. In linear focusing CSP systems synthetic oils are prevalently employed; more recently, the use of molten salt mixtures in linear focusing CSP systems has been proposed too. This paper presents a comparative assessment of thermal oils and five four nitrate/nitrite mixtures, among the ones mostly employed or proposed so far for CSP applications. The typical medium-size CSP plant (50 MWe) operating with synthetic oil as HTF and the “solar salt” as TES was considered as a benchmark. In the first part of the paper, physical properties and operation ranges of different HTFs are reviewed; corrosion and environmental issues are highlighted too. Besides an extensive review of HTFs based on data available from the open literature, the authors report their own obtained experimental data needed to thoroughly compare different solutions. In the second part of the paper, the impact of the different HTF options on the design and operation of CSP plants are analyzed from techno-economic perspectives
Performance of an indirect packed bed reactor for chemical energy storage
No full textChemical systems for thermal energy storage are promising routes to overcome the issue of solar irradiation discontinuity, helping to improve the cost-effectiveness and dispatchability of this technology. The present work is concerned with the simulation of a configuration based on an indirect-packed bed heat exchanger, for which few experimental and modelling data are available about practical applications. Since air shows advantages both as a reactant and heat transfer fluid, the modelling was performed considering a redox oxide based system, and, for this purpose, it was considered a pelletized aluminum/manganese spinel. A symmetrical configuration was selected and the calculation was carried out considering a heat duty of 125 MWth and a storage period of 8 h. Firstly, the heat exchanger was sized considering the mass and energy balances for the discharging step, and, subsequently, air inlet temperature and mass flow were determined for the charging step. The system performances were then modelled as a function of the heat exchanger length and the charging and discharging time, by solving the relative 1D Navier-Stokes equations. Despite limitations in the global heat exchange efficiency, resulting in an oversize of the storage system, the results showed a good storage efficiency of about 0.7
Chemical CSP storage system based on a manganese aluminium spinel.
No full textChemical storage systems are a promising innovative route to overcome the issue of the solar irradiation storage, resulting as cost effective and with high energy density. A main problem with these kinds of materials is to design a synthesis method for preparing stable reactive structures, presenting at the same time a high volumetric charging/discharging enthalpy. At this purpose, a size controlled spinel was produced, characterized and investigated regarding its thermophysical and kinetics properties. The obtained powder presents an average diameter between 100 and 200 μm and an energy density of 133 J/g and an experimental test was carried out to verify the spinel morphology stability under thermal cycles. The specific heat is similar to other structured chemical storage system and makes the spinel feasible to be used also as sensible accumulation medium. Despite the relatively high particles size, and the expected small exposed reactive area, the charging, and especially discharging reaction rates resulted particularly favourable and comparable with the reported behaviour of micrometric powders. The particularly simple preparation method plus the cost effectiveness of the precursors leads to a quite convenient expected cost for the storage material, absolutely similar to commercially available accumulation systems
Thermophysical, environmental, and compatibility properties of nitrate and nitrite containing molten salts for medium temperature CSP applications: A critical review
No full textThe production of electric energy from solar radiation is nowadays one of the most investigated and developed “carbon free” technology. A throughout investigation of the ceramics most commonly used as heat transfer fluids and/or heat storage materials for concentrating solar power systems (i.e. alkaline and heart alkaline nitrate/nitrite mixtures) is here reported. The study stems by the need to base materials selection on an accurate and critical knowledge of all their characteristics, including their thermophysical, environmental compatibility, and economic features. At this purpose, a rating criterion have been established, to readily show the advantages and disadvantages of each material, and to highlight which characteristics of the examined materials need to be further investigated and improved. Nitrate/nitrite mixtures have also been compared with other ceramics used for thermal storage, such as solid fillers, liquid metals, other salt mixtures, or phase change materials
Thermophysical, environmental, and compatibility properties of nitrate and nitrite containing molten salts for medium temperature CSP applications: A critical review
No full textThe production of electric energy from solar radiation is nowadays one of the most investigated and developed “carbon free” technology. A throughout investigation of the ceramics most commonly used as heat transfer fluids and/or heat storage materials for concentrating solar power systems (i.e. alkaline and heart alkaline nitrate/nitrite mixtures) is here reported. The study stems by the need to base materials selection on an accurate and critical knowledge of all their characteristics, including their thermophysical, environmental compatibility, and economic features. At this purpose, a rating criterion have been established, to readily show the advantages and disadvantages of each material, and to highlight which characteristics of the examined materials need to be further investigated and improved. Nitrate/nitrite mixtures have also been compared with other ceramics used for thermal storage, such as solid fillers, liquid metals, other salt mixtures, or phase change materials. © 2018 Elsevier Lt
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