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The use of concentrated solar energy for the reduction of CuO in H2
摘要： The reduction of copper (II) oxide was carried out under concentrated solar radiation in a stream of gaseous mixture 5/95 v/v H2/N2 in a 1.5 kW thermal power vertical axis parabolic concentrator at the PROMES-CNRS solar facility (Odeillo-Font Romeu, France). Experiments were performed using a commercial oxide in two different forms, powdered and compacted specimens. The reduction of CuO to elemental Cu was more effective for compacted specimen yielding a dendrite microstructured metallic copper with an electrochemical behavior similar to that exhibited by the commercial metal. In the case of powdered specimen, a composite metal/oxide (Cu/Cu2O) block was obtained as a macroporous material. The reduction process of CuO under concentrated solar energy tracks through the formation of Cu2O as the only intermediate phase, which was evidenced by X-ray diffraction and scanning electron microscopy.
关键词： Copper,Concentrated solar energy,Hydrogen,Copper oxide reduction
更新于2025-09-19 17:15:36
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Environmental evaluation of Waste to Energy plant coupled with concentrated solar energy
摘要： Life Cycle Assessment (LCA) was applied to evaluate the environmental impact of a hybrid energy system based on the integration of a Waste to Energy plant with concentrated solar energy plant. In the Waste to Energy (WtE) section only saturated steam is produced, while the superheating takes place in an external superheater fed by the concentrated solar energy or, when this is not enough, by a natural gas backup boiler. Different couples of pressure and temperature, for the superheated steam (51 bar, 440 °C; 60 bar, 480 °C; 70 bar, 520 °C), different values for the solar multiple (1.5, 2.0 and 2.5) and different values for the thermal storage capacity (6 h, 10 h and 14 h) were considered, leading to 27 possible cases. Construction, operation and end-of-life phases were included in the LCA system boundary. Calculated global warming indicator, in kg of equivalent CO2 per MJ of produced electricity, slightly decreases for increasing steam parameter cases and for increasing storage hour cases, while a more relevant reduction was observed for increasing solar multiple values. The main contribution to global warming derives from the operation phase of the WtE part (67-86% of the operation), while the remaining part (14-33%) is given by the solar section, for which, in turn, the main contribution is the impact deriving from the natural gas combustion in the backup boiler.
关键词： WtE plant,life cycle assessment,global warming,concentrated solar energy
更新于2025-09-12 10:27:22
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Model of the solar-driven reduction of cobalt oxide in a particle suspension reactor
摘要： We develop a model to investigate the impact of volume fraction and extent of mixing on the thermal efficiency with which a cavity-based particle suspension solar reactor reduces Co3O4 into CoO and O2. Thermal efficiency is defined as the fraction of solar energy used to drive the endothermic reduction. In the model, particles move continuously through the reactor in either mixed or plug flow—mixing conditions that give rise to isothermal and nonisothermal suspensions, respectively—and reduce at a rate governed by shrinking core kinetics, the parameters of which are determined using thermogravimetric data. Radiation is simulated using the Monte Carlo Ray Tracing technique. The model is applied to a reactor heated by 4 kW of point-focused solar radiation with a mean concentration ratio of 1400 suns containing monodisperse suspensions of 40 m diameter particles with volume fractions between 1×10?5 and 1×10?2. Thermal efficiency is insensitive to mixing for the two conditions considered. The maximum thermal efficiency obtained for mixed flow with an isothermal suspension is 34.1% at 102 g min?1 and a volume fraction of 2.3×10?4. At the same volume fraction, the maximum thermal efficiency for nonisothermal plug flow is 33.2% at 94 g min?1. Thermal efficiency is more sensitive to the volume fraction, but only below a threshold value of 2×10?4. Thus, from the perspective of coupling heat transfer to the chemical reaction, design and operational efforts of particle suspension reactors for the reduction of cobalt oxide should focus on generating suspensions of at least this threshold value rather than on mixing the particles within the suspension.
关键词： Cobalt oxide,Thermochemical energy storage,Participating media,Concentrated solar energy
更新于2025-09-04 15:30:14
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High-temperature tungsten trioxides obtained by concentrated solar energy: physicochemical and electrochemical characterization
摘要： High-crystalline tungsten trioxides (WO3) have been synthesized by an environmentally friendly method using concentrated solar energy. The obtained tungsten trioxides (WO3) at three different temperatures and two oxygen mole fractions used for the highest synthesis temperature were characterized by XRD, SEM, and XPS. Higher crystallinity and concentration of W5+ was observed in tungsten trioxides as the synthesis temperature increased. Nevertheless, despite of the different synthetic conditions used, a mixture of two different crystalline structures was observed in all solar-prepared tungsten trioxides: monoclinic and triclinic. Comparing oxides obtained at 1000 °C, higher concentration of W5+ and more defects were found when using lower oxygen molar fraction (WO3-1000-2). Their electrochemical performance was evaluated using cyclic voltammetry (CV) in a conventional three-electrode cell in the following three aqueous electrolytes: acidic, alkaline, and neutral media. In the acidic medium, all the tungsten trioxides showed a capacitive behavior, which was enhanced for oxides obtained at 1000 °C due to a mixed valence of W. On the other hand, in the alkaline medium, a catalytic behavior was detected with higher activity towards hydrogen evolution reaction for the oxide with more defects, higher crystallinity, and monoclinic phase, obtained at 1000 °C and a lower oxygen molar fraction in the synthesis. Finally, in the neutral medium, the oxides synthesized at 1000 °C presented a capacitive behavior whereas the oxides prepared at the lowest temperatures (600 and 800 °C) presented electrochemical processes related to a catalytic behavior for water reduction, which must correspond to their minor concentration of defects, as confirmed by XPS.
关键词： High-temperature synthesis,Concentrated solar energy,Green synthesis,WO3,Tungsten trioxides
更新于2025-09-04 15:30:14