This paper investigated CO2 utilization into energy density chemical using NiFe2O4@Alumina support porous-medium filled reactor heated by high-flux solar simulator. A combination of numerical and ...experimental studies is developed to investigate the synthesis and characterization of the redox materials, thermal characteristics, redox reaction kinetics, and redox performance of NiFe2O4@Alumina support porous oxide material. Moreover, thermal and chemical energy conversion efficiency of NiFe2O4@Alumina support was analyzed. Considering the difficulty related to designing and manufacturing porous-medium filled solar thermal receiver, this study could provide tremendous innovation values and pattern impacts in the field of solar thermochemical (STC) energy conversion into fuels and chemicals.
•NiFe2O4@Alumina exhibits higher thermal-chemical conversion performance.•Thermal reduction of NiFe2O4@Alumina transits into hercynite class materials.•Formation of Ni, Fe, NiO, FeO resulted in the weight loss of NiFe2O4@Alumina.•Decrease in carbon deposit improves syngas yield.•Increasing H2 yield results in high-density chemical energy flux.
•Composite phase change material (CPCM) was prepared and characterized.•The thermal diffusivity of CPCM increased with increasing temperature.•CPCM thermal conductivity can be enhanced ≥48% by doping ...with Al2O3 nanoparticles.•Al2O3 nanoparticles was the optimal additive to improve thermal properties.•CPCMs showed excellent thermal stability over a broad working temperature range.
Chloride salts are widely used as thermal energy storage (TES) media for high-temperature solar TES systems. Their thermal properties are crucial for the performance of TES systems. In this study, we prepared and characterized chloride salts/nanoparticles composite phase change materials (CPCMs) for high-temperature thermal energy storage. The ternary chloride salts (MgCl2:KCl:NaCl with 51:22:27 molar ratio) were used as base salt and Al2O3, CuO, and ZnO nanoparticles were dispersed into the base salt at 0.7 wt% to form various composite phase change materials (CPCMs). The thermal properties of the base salt and CPCMs were measured. The results showed that the melting temperature of the CPCMs was very close to that of the base salt. The phase change latent heat of the CPCMs was slightly lower than that of the base salt while the addition of dopant nanoparticles clearly enhanced the thermal diffusivity and thermal conductivity of the CPCMs. In particular, the thermal conductivity of the CPCM doped with Al2O3 nanoparticles showed the most obvious enhancement, which increased by more than 48%, compared to that of the base salt. Al2O3 nanoparticles could be considered as an optimal additive to improve the thermal conductivity of chloride salts. Moreover, the CPCM with Al2O3 also exhibited excellent thermal stability. These good thermal characteristics of CPCM with Al2O3 nanoparticles endow it promising applications for high-temperature TES system.
Limited energy resources of sensor nodes in Wireless Sensor Networks (WSNs) make energy consumption the most significant problem in practice. This paper proposes a novel, dynamic, self-organizing ...Hesitant Fuzzy Entropy-based Opportunistic Clustering and data fusion Scheme (HFECS) in order to overcome the energy consumption and network lifetime bottlenecks. The asynchronous working-sleeping cycle of sensor nodes could be exploited to make an opportunistic connection between sensor nodes in heterogeneous clustering. HFECS incorporates two levels of hierarchy in the network and energy heterogeneity is characterized using three levels of energy in sensor nodes. HFECS gathers local sensory data from sensor nodes and utilizes multi-attribute decision modeling and the entropy weight coefficient method for cluster formation and the cluster head election procedure. After cluster formation, HFECS uses the same techniques for performing data fusion at the first hierarchical level to reduce the redundant information flow from the first-second hierarchical levels, which can lead to an improvement in energy consumption, better utilization of bandwidth and extension of network lifetime. Our simulation results reveal that HFECS outperforms the existing benchmark schemes of heterogeneous clustering for larger network sizes in terms of half-life period, stability period, average residual energy, network lifetime, and packet delivery ratio.
•Increasing heat transfer coefficient altered surface temperature and heat flux.•Increasing the mass flow rate resulted in significant thermal losses.•Emissivity of glass cover and cavity wall ...affected the reactor thermal performances.•Higher radiation losses resulted in a considerable drop in temperature.•Optimum pore size and higher porosity enhanced heat transfer in a porous medium.
In this paper, heat transfer and fluid flow of porous media solar thermochemical receiver with quartz glass cover were investigated. The Surface-to-surface radiation model and Rosseland approximation for radiation heat transfer were adopted for the transport of diffused solar irradiance and radiative transfer in the fluid phase and porous medium. An experimental test was conducted on a laboratory-scale solar thermochemical reactor. The effects of structural parameters in term of diffused irradiance intensity, the mass flow rate, heat transfer coefficient, quartz glass and inner cavity wall surface emissivity, the porosity and extinction coefficient that could affect heat transfer and fluid flow performance of the proposed solar cavity receiver were sufficiently investigated. It was found that the substantial drops in temperature were mainly attributed to the thermal losses by radiative, convective and conductive heat transfer. The numerical results are compared with the experimental data for the model validation. The thermal loss at the solar flux inlet of the receiver was obviously inevitable due to the stronger effect of heat transfer coefficient that altered the over increasing temperature and heat flux at the surface of diffuse irradiance. However, the use of optimum pore size and higher porosity material could significantly enhance the thermal performance of porous media solar thermochemical reactor.
•The transient heat transfer process is developed using 2D MCRT-FEM coupled model.•The time required for the particles to reach high temperatures is not insignificant.•Heat loss due to radiation and ...convection decreases with the increase in heat flux.•Particles with diameter of 0.2–0.4 mm have better overall thermal performance.
Obtaining the detailed transient heat transfer process between particles is one of the most important key factors to comprehensively understand the thermal conversion performance of the solar particle receiver. To present a clear understanding of heat transfer, a detailed two-dimensional transient numerical simulation of the solar particle receiver integrated with the Monte Carlo Ray Tracing method and the Finite Element Method is presented in this paper. The solar radiation flux distribution throughout the free-falling solar particle receiver is simulated by considering Monte Carlo Ray Tracing and the transient heat transfer in the circular particle process in the receiver is calculated using the Finite Element Method. Moreover, based on the coupling model, considering the transient heat transfer process inside the particles, the effects of different particle sizes, radiation fluxes, void ratio, and particle residence time on the temperature distribution and thermal performance of the solar particle receiver are also studied. The results show that the transient heat transfer process inside the single particles slightly affected the average outlet temperature of the receiver and the solar thermal energy conversion efficiency. A better outlet temperature and thermal conversion efficiency can be obtained when solid particles with a diameter of 0.2 ~ 0.4 mm in the experiment are used. This study provides basic theoretical insights and support for further research on the thermal performance, structural design, and optimization of the solar particle receiver.
Electrochemical CO2 conversion into useful products using renewable electricity is a promising route to mitigate the potential challenges regarding large CO2 emissions into the environment. However, ...there are limitations in accomplishing its practical utilization. Recently, many efforts have been made into increasing electrochemical CO2 reduction (ERC) performance using Pd-based catalysts. The Pd-based materials have exhibited unique electrocatalytic characteristics for ECR since they can convert CO2 to HCOOH and CO with high selectivity at equilibrium potential and certain negative potential range, respectively. This review provides useful insights into the recent progress made on Pd-based electrocatalysts. Different factors of Pd-based catalysts influencing ERC performance, such as the effect of size, alloy, morphology, load, and core–shell have been discussed in detail. In the end, future prospects of Pd-based catalysts have been included to briefly highlight the important future considerations of this rapidly growing technology.
•The porous skeleton of SiC and Si3N4 synthesized by the foam impregnation method has a good strength and porosities are 35.29 % and 54.39 %, respectively.•In the solar thermochemical system ...experiment, the highest instantaneous CO was 410 μmol/gNiFe2O4@SiC.•The average CO2 conversion rate of direct CO2-to-CO through NiFe2O4@SiC over seven cycles was 11.2% in the solar thermochemical system experiment.•The CO yield of NiFe2O4-supported SiC is twice that of SiC skeleton, based on photothermal synergy of support and catalyst.
The solar-driven thermochemical CO2-to-CO conversion is an effective way to achieve the mission of carbon peaking and carbon neutrality. However, synthesizing porous reacting materials with excellent thermal stability, hardness and long-term cyclic stability, oxygen exchange capacity, and higher CO2-to-CO conversion are the most important challenges associated with the thermochemical CO2-splitting approach and technological upscaling to large-scale applications. This study presented the development of NiFe2O4 oxygen carriers, the synthesis method of SiC and Si3N4 supports, and solar-to-fuel processing of the newly prepared materials through CO2-splitting under a highly concentrated solar radiative heat flux. The newly synthesized NiFe2O4@SiC porous redox material resulted in higher solar energy absorption and CO2 conversion capability with an instantaneous CO production of 410 μmol/g and direct CO2-to-CO conversion rate of 18.1 % at 1073–1273 K reaction temperature. The media composite of NiFe2O4@SiC exhibited high-temperature thermal changes, good thermochemical reaction stability, and a higher CO production rate through six redox cycles compared to NiFe2O4@Si3N4 porous reacting material. The high oxidation potential and remarkably solar radiative heat flux absorption and thermochemical CO2-splitting capacities of the newly developed materials were demonstrated through experimental analysis. The synergistic effect of the oxygen carriers (NiFe2O4) and substrate materials including SiC and Si3N4 skeletons for CO2-splitting is highlighted. This study provided comprehensive and novel experimental insights that can be used as guidance for theoretical research and application in CO2 conversion into high-value-added energy products.
The splitting of carbon dioxide through the two-step solar thermochemical cycle presents enormous potential, for it holds the dual functionalities of solar fuel production and carbon-based energy ...recovery. However, the industrialization of this technology is impeded by two critical factors: The absence of fully developed oxygen carriers and advanced reaction devices that deliver exceptional performance. In order to identify a potentially effective oxygen carrier, 50 wt% NiO-modified CoFe
2
O
4
is selected as the active component and characterized by means of thermogravimetry, scanning electron microscopy, and energy dispersive spectroscopy, so as to clarify its oxygen exchange capacity, micromorphology and elemental composition in high-temperature thermochemical cycles. Further, nanoparticle-coated foam-structured materials are prepared in combination with SiC ceramic foam for experimental testing in a high-flux solar reactor. The results indicate that a peak CO yield of 1.96 mL min
−1
g
−1
can be gained in a 1500–1250 K preliminary test, demonstrating the application potential of the material. In contrast to conventional redox materials, the CO
2
activity of the materials synthesized in this study exhibits an enhancement with rising oxidation temperature. It means that isothermal cycles can potentially achieve higher conversion and fuel yield than non-isothermal cycles, while simultaneously reducing the amount of irreversible heat loss during high-temperature cycling. Although the estimated steady-state thermal efficiency of the solar reactor can reach up to 42%, further optimization of the reactor design is necessary to enhance energy conversion efficiency, as it is partially limited by the dimensions of the reaction chamber.
Due to the utilization of concentrated solar energy, a more complex high-temperature thermal environment will be formed inside the solar thermochemical reactor, thereby resulting in complicated ...behaviors of chemical reactions. This paper numerically investigates the carbon deposition behaviors inside a Ni/Al2O3-based catalyst porous-filled solar thermochemical reactor for the dry reforming of methane (DRM) process under various operational conditions. The reaction kinetics for DRM including four side reactions are programmed via UDFs. The simulation results indicate that the optimal structural parameters of porous media for high-value syngas products with less carbon deposition are ϕ = 0.8 and d p = 2 mm, while the optimal feed ratio is CH4/CO2 = 1. Besides, the operating condition at v in = 100 mL/min and P lamp = 0.7 kW has the advantage of obtaining higher conversion rate while reducing the carbon deposition rate to some extent.
Converting solar energy efficiently into hydrogen is a promising way for renewable fuels technology. However, high-temperature heat transfer enhancement of solar thermochemical process is still a ...pertinent challenge for solar energy conversion into fuels. In this paper, high-temperature heat transfer enhancement accounting for radiation, conduction, and convection heat transfer in porous-medium reactor filled with application in hydrogen generation has been investigated. NiFe-Aluminate porous media is synthesized and used as solar radiant absorber and redox material. Experiments combined with numerical models are performed for analyzing thermal characteristics and chemical changes in solar receiver. The reacting medium is most heated by radiation heat transfer and higher temperature distribution is observed in the region exposed to high radiation heat flux. Heat distribution, O2 and H2 yield in the reacting medium are facilitated by convective reactive gas moving through the medium's pores. The temperature gradient caused by thermal transition at fluid-solid interface could be more decreased as much as the reaction chamber can store the transferred high-temperature heat flux. However, thermal losses due to radiation flux lost at the quartz glass are obviously inevitable.
•Region exposed to high radiation flux exhibits higher temperature distribution.•Thermal loss due to radiation loss at the quartz glass is obviously inevitable.•Efficient thermal reduction of NiFe-Aluminate RPCs results in higher O2 and H2 yield.•NiFe-Aluminate RPCs exhibits excellent thermal stability and durability.
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