Solar Reactor Research Articles

Bionic leaf-inspired catalyst bed structure for solar membrane reactor aiming at efficient hydrogen production and separation

Membrane reactor technology permits efficient solar thermochemical conversion at low temperatures, but the performance is often limited by concentration polarization. To cope with the hydrogen (H2) concentration polarization in solar membrane reactors, this study proposes a bionic solar membrane reactor (BSMR) inspired by the excellent production-transport management ability of leaves. Designing the structural parameters of the bionic catalyst bed obtains the efficient BSMR, and mechanistically analyzes its reaction and separation performance enhancement. The results show that the BSMR achieves a synergistic reinforcement pattern of ordered H2 separation driving reaction and reaction providing H2 separation pressure at >90° pore block tilt angle, while large porosity differences and small pore block lengths can further amplify this synergy. Currently, the BSMR with pore blocks of 140° tilt angle, 20 mm length and 0.3 low porosity has the optimal performance, which improves methane conversion and hydrogen recovery by 13.4–99.0% and 13.7–99.0%, respectively, relative to the conventional solar membrane reactor under different operating conditions. Also, it is shown that optimal performance enhancement is achieved at high steam-to-methane ratios, low inlet temperatures and high inlet flow rates. In general, the design referring to leaves makes BSMR well inherit the consistently superior performance of leaves, providing new ideas for efficient hydrogen production and separation.

Biomimetic Solar Photocatalytic Reactor for Selective Oxidation of Aromatic Alcohols with Enhanced Solar‐Energy Utilization

AbstractLow utilization of solar energy remains a challenge that limits photocatalytic efficiency. To address this issue, this work proposes a bionic solar photocatalytic reactor (BSPR) for efficient selective oxidation of aromatic alcohols. A biomimetic phototropic hydrogel is prepared by coupling chlorine‐doped polypyrrole (Cl‐PPy) and poly(N‐isopropyl acrylamide) (PNIPAm) to maximize light‐harvesting efficiency automatically, allowing the BSPR to maintain high catalytic levels throughout the day. Molecular dynamics simulations are used to unveil the understanding of the fast photoresponsive behavior of Cl‐PPy/PNIPAm from a molecular level, while COMSOL simulations are conducted to follow the macroscopically phototropic mechanism of BSPR. Attributing to the existence of PdS/S vacancies riched ZnIn2S4 nanocomposite in the top flower‐shaped hydrogel, the BSPR displays a special function for efficiently photocatalytic oxidation of aromatic alcohols under solar illumination (yield of 4‐methoxybenzaldehyde: 479.5 µmol g−1 h−1; selectivity: 68.8%). Two possible reaction pathways are identified as follows: photogenerated holes can attract aromatic alcohols directly and generate aromatic aldehydes; photoexcited electrons oxidize O2 to ·O2− can also react with the adsorbed aromatic alcohol. This study presents a promising paradigm that explores opportunities for enhanced utilization of light energy, offering a novel approach to maximize its efficiency in practical applications.

Experimental study of a high-temperature porous-medium filled solar thermochemical reactor for CO production

Solar thermochemistry via a two-step cycle has been considered as a promising technology as it is feasible to convert solar energy into fuels directly. The improvement of solar-to-fuel energy efficiency is strongly dependent on the heat recovery during the temperature swing between the reduction and oxidation steps. The present article describes the experimental results of a solar thermochemical reactor with gas-gas heat recovery. The reactor's inlet and outlet gases are exchanged through the heat exchanger, thereby improving the energy utilization efficiency, and a series of experiments are carried out to further demonstrate the feasibility of this technology. The influence of the pressure of the endothermic reduction step and the influence of the concentration of reactants in the exothermal oxidation step on the experimental results are analyzed. The experimental results show that vacuuming condition further promoted the reduction kinetics compared with Ar purging, and the yield of CO increases from 1.13 mL/gCeO2 to 1.32 mL/gCeO2 within 60 min. Therefore, the following experiments are completed under vacuuming condition for the endothermic reduction reaction. The yield of CO is favored at higher CO2 partial pressure, and the yield of CO increases from 44.65 mL to 279.42 mL as the volume flow rate of CO2 increase from 0.5 L/min to 4 L/min. This research provides useful information on the industrial implementation of the thermochemical technology.

Solar thermal reactor model for pyrolysis of waste plastic

ABSTRACT The ability to convert waste plastic into combustible liquids and gases using solar energy could help transform the problem of disposal of non-recyclable plastic into a valuable and environmentally responsible source of fuel. The purpose of this study is to propose a practical model for a compound parabolic trough solar thermal reactor for pyrolysis of waste plastic. The model integrates predictions of energy available from solar radiation (at a given location, time of day and time of year) with parabolic trough collector orientation and efficiency, a transient energy balance for an evacuated tube reactor and pyrolysis kinetics of waste plastic. The experimental setup used to test the model includes a pyranometer, a commercial solar collector consisting of a 60 cm long evacuated tube with a compound parabolic reflector and multi-channel data loggers to collect temperature, humidity and radiation data. The solar radiation sub-model was found to be in excellent agreement with clear-sky irradiance data collected using the pyranometer. Predictions of reactor temperature and reaction rate were found to be sensitive to the concentrator aperture area, solar irradiance, type of plastic (Arrhenius kinetics) and radiation properties of the evacuated tube reactor but relatively insensitive to humidity, wind velocity and terrestrial irradiance. The model shows that even on a small scale, favourable conditions for pyrolysis of waste plastic can be achieved within a solar reactor.

Multi-field coupling and collaborative optimization design of the solar thermochemical cycle process based on ceria

Most solar reactors commonly encounter challenges such as high-temperature gradients, suboptimal photo-thermal efficiency, and limited catalyst utilization. This lack of coordination in the design of solar reactors stems from the inadequate integration of the photothermal-chemical coupling synergistic relationship within the reactor. We developed a comprehensive multi-physics coupling mathematical model that incorporates optics, heat transfer, and chemical reactions to facilitate the cooperative optimization design of solar reactors. This study unveils the multi-field coordination mechanism within solar reactors. The optimization design of the secondary concentrator, reactor structure, fluid flow layout, and porous media catalyst structure was systematically carried out. A two-step thermochemical cycle of methane reducing cerium oxide decomposing water vapor to produce hydrogen was used as the reaction system to analyze the performance of the prototype reactor. The influences of ray power, reaction flow rate, and oxygen carrier mass on the solar-to-chemical efficiency were analyzed. The optimization results demonstrate that, by considering factors such as light power, mass transfer flow, and oxygen carrier mass within the optimization framework, the solar chemical energy conversion efficiency can reach a maximum of 38.75%.

Monitoring and Data Acquisition System for a 3kW Grid-Connected Photovoltaic System

This research aimed to design and implement a wireless monitoring and data acquisition system using LabVIEW for a 3 kW Solar Fuel Cell Reactor. The system incorporated advanced technologies like Raspberry Pi 3B+, Arduino Nano, PT100 temperature sensors, voltage divider, ACS758, and calibrated cells for precise irradiance sensing. It adhered to the IEC-61724-2017 standard and utilized a 3D-printed housing with a DIN rail fastener for durability and convenience. During a 5-day test period, the study examined the impact of temperature on the photovoltaic module, revealing variations of up to 3 °C among cells, leading to parameter dispersion and performance losses. Temperature also showed an inverse relationship with voltage, with higher temperatures resulting in decreased efficiency and a maximum surface temperature of 52.31 °C. The research also explored the effect of irradiance, finding a direct correlation between irradiance and generated current. Notably, extreme solar irradiance events occurred, with the highest value reaching 1245.90 W/m2 for 6 s at 11:39:13 on June 10, 2023, and the longest event lasting 176 s at 1219.77 W/m2, occurring at 11:34:17. The collected indicators provided reliable information on energy generation by the SFCR under specific environmental conditions.

Rapid prediction, optimization and design of solar membrane reactor by data-driven surrogate model

Membrane reactor is a process intensification technology that enhances traditional reactions. This study investigates the optimal operating conditions and structural designs of an insert-enhanced solar methane-to-hydrogen Pd-based membrane reactor (SMMR) for more efficient conversion-reaction and separation-purification. Applying response surface methodology, a data-driven surrogate model is fitted to SMMR for rapid performance prediction, which can combine algorithms to optimize operating conditions and structures. The results indicate that operating conditions center around matching reaction kinetics to strengthen reaction, while structural parameters focus on weakening concentration polarization to enhance separation. Methane feed flow and steam-to-methane ratio are almost always the dominant factors, especially in balancing methane conversion and fuel efficiency. Moreover, SMMR under high-pressure more relies on optimized inserts’ transport enhancement to improve overall reaction-separation performance. The optimized results by single- and multi-objective optimization are similar, where the 4-helical insert delivers a comprehensive excellent methane conversion of 0.95, fuel efficiency of 0.86 and hydrogen recovery of 0.95 at 400 °C inlet temperature and 8 bar pressure. Overall, the optimization of SMMR surrogate model consumes less than 0.2 % of the single simulation CPU time and the average error of the results is about 3 %, showing high efficiency and prediction accuracy.

Optimized operational strategy of a solar reactor for thermochemical hydrogen generation

Optimized operational strategy of a solar reactor for thermochemical hydrogen generation

Back propagation neural network based proportional-integral hybrid control strategy for a solar methane reforming reactor

To handle the impact of solar radiation fluctuations on the solar reactor, a new proportional-integral (PI) hybrid control strategy based on back propagation neural network (BPNN) is designed in this study to achieve stable operation. Firstly, the BPNN model optimized by genetic algorithm is trained using reactor model simulation data. Then, the BPNN model is combined with PI feedback control to obtain a BPNN-based PI feedforward-feedback hybrid control strategy for regulating the inlet flow rate. Finally, the effectiveness of the control strategy during transient operation under different disturbances is tested. The results show that during actual solar radiation disturbance, the integral square errors (ISE) of outlet hydrogen fraction and methane conversion for BPNN-based PI hybrid control are 7.03 × 10−6 and 1.05 × 10−4, respectively. Compared to traditional PI feedback control, the new hybrid control strategy represents a reduction of 94% and 91% in ISE, indicating that the strategy can significantly improve production stability.

Design of solar cement plant for supplying thermal energy in cement production

This work describes the implementation of concentrated solar energy for the calcination process in cement production. Approach used for providing solar energy includes the utilisation of a solar tower system with a solar reactor atop the solar tower or preheater tower in a conventional cement plant. Analysis considered thermal energy substitution ranging from 100% to 50%. Solar power output of the reactor was 793 MW after considering the 45% heat loss in the reactor. The number of heliostats required for generating 793 MW solar reactor power was 15066 with a total required land surface of 1130 ha. Depending on the thermal losses i.e., 15%, 30%, and 45%, the net conversion efficiency was 44, 56, and 69, respectively. Implementing concentrated solar thermal (CST) in the calcination process of the selected conventional cement plant could save 419 thousand tons of CO2 annually. Economic analysis suggests that approach is useful when there is minimum thermal loss in the solar reactor. Payback time (PBT) and internal rate of return (IRR) for design model were 10.4 years and 5.4% when there were 45% thermal losses in solar reactor. Major challenges are regarding the conversion of laboratory equipment to industrial size, working in high-temperature environments, raw material transportation systems, and thermal storage systems.

Synthesis and Characterization of ZnO-Nanostructured Particles Produced by Solar Ablation.

Nowadays, nanotechnology offers opportunities to create new features and functions of emerging materials. Correlation studies of nanostructured materials' development processes with morphology, structure, and properties represent one of the most important topics today due to potential applications in all fields: chemistry, mechanics, electronics, optics, medicine, food, or defense. Our research was motivated by the fact that in the nanometric domain, the crystalline structure and morphology are determined by the elaboration mechanism. The objective of this paper is to provide an introduction to the fundamentals of nanotechnology and nanopowder production using the sun's energy. Solar energy, as part of renewable energy sources, is one of the sources that remain to be exploited in the future. The basic principle involved in the production of nanopowders consists of the use of a solar energy reactor concentrated on sintered targets made of commercial micropowders. As part of our study, for the first time, we report the solar ablation synthesis and characterization of Ni-doped ZnO performed in the CNRS-PROMES laboratory, UPR 8521, a member of the CNRS (French National Centre for Scientific Research). Also, we study the effect of the elaboration method on structural and morphological characteristics of pure and doped ZnO nanoparticles determined by XRD, SEM, and UV-Vis.

Application of CoFe2O4-NiO nanoparticle-coated foam-structured material in a high-flux solar thermochemical reactor

Application of CoFe2O4-NiO nanoparticle-coated foam-structured material in a high-flux solar thermochemical reactor

Photo-Induced Super-Hydrophilicity of Nano-Calcite @ Polyester Fabric: Enhanced Solar Photocatalytic Activity against Imidacloprid.

The present study is pertinent to photo-induced, hydrophilic, nano-calcite grown onto the mercerized surface of polyester fabric (PF), treated with UV (10-50 min) and visible light (1-5 h) in addition to its photocatalytic application. The wicking method has been employed to select the most hydrophilic sample of fabric upon irradiation. The micrographs obtained by scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy indicated the erosions occurring at the surface of nano-calcite after UV light irradiation, maintaining the crystallinity of the photocatalyst. The surface charge has been measured for as-fabricated and irradiated nano-calcite @ PF for the development of high negative zeta potential after UV light irradiation (-24.6 mV). The irradiated nano-calcite @ PF exhibited a significant change in its contact angle, and the wetting property was enhanced to a considerable extent on UV (55.32°) and visible light irradiation (79.00°) in comparison to as-fabricated nano-calcite @ PF (137.54°). The irradiated samples of nano-calcite @ PF delineated the redshift in harvesting of solar spectrum, as revealed by diffuse reflectance spectroscopy comparative spectra. Additionally, the band gap of untreated nano-calcite was found to be 3.5 eV, while UV- and visible light-irradiated PF showed a reduction in band gap up to 2.95 and 3.15 eV upon UV and visible light irradiation. The photocatalytic efficiency of mesoporous nano-calcite was evaluated by photocatalytic degradation of imidacloprid as the probe pollutant. Higher solar photocatalytic degradation of imidacloprid (94.15%) was attained by UV light-irradiated nano-calcite @ PF. The time-resolved photoluminescence study has verified the high photocatalytic activity of UV light-irradiated nano-calcite @ PF for the generation of high concentration of hydroxyl radicals. The highly efficient reusability of a nano-calcite-based solar photocatalytic reactor has been observed for 10 cycles of treatment of imidacloprid bearing wastewater. The enhanced photocatalytic activity of UV light-exposed (20 min), superhydrophilic, nano-calcite @ PF for mineralization of pollutants suggests it to be an efficient solar photocatalyst for environmental applications.

Potential of solar thermal calciner technology for cement production in India and consequent carbon mitigation

This study describes the potential of solar thermal calciner technology and consequent carbon mitigation for Indian cement industries. Approach used to provide solar energy involves the installation of a solar tower system with a solar reactor atop the solar tower or preheater tower in a conventional cement plant. For potential estimation, locations of the clusters of cement plants with their actual annual cement production have been identified. Based on the annual actual cement production, the yearly process heating demand for the calcination process for each cement plant is estimated. Solar irradiation of each location of the cement plant is identified, and the plants with direct normal irradiation (DNI) > 1700 kWh/m2 /annum are considered. Total thermal energy saved is estimated as 133.36 PJ/annum and CO2 mitigation is estimated as 7413.73 thousand tonnes.

Investigating the impact of modeling assumptions and closure models on the steady-state prediction of solar-driven methane steam reforming in a porous reactor

In this work, the effect of different modeling assumptions and closure models — frequently considered in the literature of solar thermochemical reactors and closely-related areas — is investigated. The application of different modeling assumptions and closure models may strongly affect the results accuracy and compromise a meaningful comparison across literature works. The following is herein investigated: (i) the role of upstream and downstream fluid regions to the two-phase reactor region; (ii) relevance of species and gas-phase thermal diffusion mechanisms; (iii) reaction heat accounted for in gas- or solid-phase energy balance equations; (iv) local thermal equilibrium (LTE) vs. local thermal non-equilibrium (LTNE) models; (v) model dimension (one-dimensional vs. two-dimensional axisymmetric models); (vi) local volumetric convection heat transfer correlations; and (vii) effective solid thermal conductivity correlations. The relevance of this work extends well beyond the current application (methane steam reforming in a volumetric solar reactor), since similar models and assumptions have also been widely applied for predicting the performance of volumetric solar absorbers and dry reforming solar reactors. The results show that an upstream fluid region should be considered while applying inlet first-type boundary conditions and diffusion transport in the corresponding governing equations to ensure full-conservation and simultaneously to account for developing profiles upstream the reactor inlet section. For the operating conditions considered, species diffusion and gas-phase heat conduction are particularly relevant at the reactor centerline but with a negligible integral effect. A significant difference in the reactor performance is observed while accounting for the reaction heat from surface reactions in the solid- or gas-phase energy balances — for the lowest inlet gas velocity herein considered, the thermochemical efficiency (methane conversion) is approximately equal to 70.8% (76.3%) and 77.3% (84.7%) assigning the reaction heat to the gas- and solid-phase energy balances, respectively. LTE model results are strikingly different from the results obtained with the LTNE model considering the reaction heat accounted for in the gas-phase energy balance but not significantly different from the results computed with the LTNE model with the reaction heat assigned to the solid-phase energy balance. One-dimensional reactor modeling provided with an average concentrated solar heat flux value results in a similar average performance as that given by a two-dimensional model but fails to predict the high temperatures observed at reactor centerline — for the lowest inlet gas velocity, the difference between the maximum solid temperatures predicted by one- and two-dimensional models is about 340K.

Simultaneous degradation of contaminants of emerging concern and disinfection by solar photoelectro-Fenton process at circumneutral pH in a solar electrochemical raceway pond reactor

Simultaneous contaminants of emerging concern (CECs) removal and wild microorganisms’ inactivation was evaluated by applying solar photoelectro-Fenton (SPEF) process in actual secondary effluent collected from a real municipal wastewater treatment plant (MWWTP). 20 L of a mixture of four CECs was used as model pollutants (200 μg/L of acetaminophen, caffeine, sulfamethazine, and sulfamethoxazole each one). The SPEF process was carried out on fully sunny days, at circumneutral pH using the complex Fe3+-EDDS, in a solar electrochemical – raceway pond reactor (SEC-RPR). Initially, the optimal conditions for CECs degradation were determined using a response surface model based on current density, iron complex concentration and Fe3+-EDDS addition time (to allow previous accumulation of H2O2) as model inputs. A current density of 24.6 mA/cm2, a Fe3+-EDDS complex concentration of 0.089 mM and 3.8 min of previous H2O2 accumulation were the resulting optimum conditions that were afterwards applied for the simultaneous degradation of the CECs synthetic mixture and wild microorganisms inactivation in actual secondary effluent. About 85% CECs removal and complete E. coli inactivation were achieved in 30 min, approximately, while E. faecalis and total coliforms could be inactivated under detection limit in 60 min and 75 min, respectively.

Retraction Note: A systematic study on simulation and modeling of a solar biogas reactor.

Retraction Note: A systematic study on simulation and modeling of a solar biogas reactor.

Topology optimization of catalyst bed structure for a solar steam methane reforming reactor aiming at improved conversion efficiency and hydrogen yield

This study optimized the distribution of catalysts porosity for solar steam methane reforming (SMR) reactor using the topology optimization with different objective functions. The optimized structures were similar, wherein dense catalysts were filled in the high-temperature region at the front of the reactor which increased the contact area between reactants and catalysts, and sparse metal foam catalysts were filled at the rear, which was conducive to reducing the flow resistance and facilitating the collection of products. To facilitate the filling in the actual production process, the optimized structure was simplified, and the simplification structure improved the hydrogen production by 6.84%–22.33% and the methane conversion by 6.54%–11.49% under different working conditions compared with the uniform distribution structure. By adjusting the porosity distribution of the catalysts, the temperature field of optimized reactor conformed to the principle of minimum Gibbs free energy (Gmin) and provided guidance for improving the solar SMR reactor performance.

A novel Corchorus olitorius-derived biochar/Bi12O17Cl2 photocatalyst for decontamination of antibiotic wastewater containing tetracycline under natural visible light

Herein, a novel composite of Corchorus olitorius-derived biochar and Bi12O17Cl2 was fabricated and utilized for the degradation of tetracycline (TC) in a solar photo-oxidation reactor. The morphology, chemical composition, and interaction between the composite components were studied using various analyses. The biochar showed a TC removal of 52.7% and COD mineralization of 59.6% using 150 mg/L of the biochar at a pH of 4.7 ± 0.5, initial TC concentration of 163 mg/L, and initial COD of 1244 mg/L. The degradation efficiency of TC increased to 63% and the mineralization ratio to 64.7% using 150 mg/L of bare Bi12O17Cl2 at a pH of 4.7 ± 0.5, initial TC concentration of 178 mg/L, and COD of 1034 mg/L. In the case of biochar/Bi12O17Cl2 composite, the degradation efficiency of TC and COD mineralization ratio improved to 85.8% and 77.7% due to the potential of biochar to accept electrons which retarded the recombination of electrons and holes. The synthesized composite exhibited high stability over four succeeding cycles. According to the generated intermediates, TC could be degraded to caprylic acid and pentanedioic acid via the frequent attack by the reactive species. The prepared composite is a promising photocatalyst and can be applied in large-scale systems due to its high degradation and mineralization performance in a short time besides its low cost and stability.

Solar‐Driven Redox Splitting of CO2 Using 3D‐Printed Hierarchically Channeled Ceria Structures

AbstractFuel produced from CO2 and H2O using solar energy can contribute to making aviation more sustainable. Particularly attractive is the thermochemical production pathway via a ceria‐based redox cycle, which uses the entire solar spectrum as the source of high‐temperature process heat to directly produce a syngas mixture suitable for synthetizing kerosene. However, its solar‐to‐fuel energy efficiency is hindered by the inadequate isotropic topology of the ceria porous structure, which fails to absorb the incident concentrated solar radiation within its entire volume. This study presents the design and 3D‐print of hierarchically channeled structures of pure ceria by direct ink writing (DIW) to enable volumetric radiative absorption while maintaining high effective densities required for maximizing the fuel yield. The complex interplay between radiative heat transfer and thermochemical reaction is investigated in a solar thermogravimetric analyzer with samples exposed to high‐flux irradiation, mimicking realistic operation of solar reactors. Channeled structures with a stepwise optical thickness achieve a higher and more uniform temperature profile compared to that of state‐of‐art isotropic structures, doubling the volume‐specific fuel yield for the same solar flux input. Thermomechanical stability of the ceria graded structures, DIW‐printed using a novel ink formulation with optimal rheological behavior, is validated by performing 100 consecutive redox cycles.