Solar Thermochemical Conversion Research Articles

Green iron and syngas production via continuous solar-driven agricultural waste biomass gasification combined with iron(III) oxide reduction

The production of renewable synthetic fuels and chemicals from solar energy and agricultural waste biomass is considered. Solar thermochemical conversion processes offer a promising pathway to a sustainable fuel economy and green chemical industry. This study investigates the continuous solar-driven gasification of agricultural biomass (betel nut waste) combined with iron oxide (Fe2O3) reduction to produce carbon-neutral syngas and green metallic iron in a single process. A thermodynamic analysis of the system was initially conducted to predict the distribution of equilibrium products. Then, on-sun continuous processing was experimentally carried out under different operating conditions, including betel/Fe2O3 molar ratios (0.56-1.5) and temperatures (900-1200°C) to evaluate the process feasibility and reliability. As a result, solar gasification of betel nut waste combined with Fe2O3 reduction performed exceptionally well with continuous reactant particles feeding, demonstrating a feasible pathway for producing green iron and high-quality syngas. The maximum syngas yield reached 63.3 mmol/gdry_betel, approaching its theoretical value, and high-purity Fe was simultaneously produced. The process demonstrated high efficiency, with maximum carbon conversion approaching 98%, energy upgrade factor up to 1.26, and solar-to-fuel energy conversion efficiency up to 14.4%, highlighting remarkable conversion performance of biomass and solar energy to chemicals.

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.

Deciphering high-efficiency solar-thermochemical energy conversion process of heat pipe reactor for steam methane reforming

• Solar-thermochemical conversion mechanism for the reactor was revealed. • The maximum solar-thermochemical conversion efficiency is 41% • The heat conduction is the prime heat transfer mode in the reactor cavity. The high temperature heat pipe reactor (HTPR) driven by solar energy via steam methane reforming opens up a new avenue to produce hydrogen as aviation fuel with low carbon emission. Herein, the energy conversion and transfer process of steam methane reforming in the HTPR was disclosed by experiments and simulations. Firstly, the solar to thermal conversion and the heat transfer process in the start-up stage of the HTPR were investigated. The solar thermal response was immediate, and the reactor temperature difference was merely about 30 °C from top to bottom, providing a uniform thermal boundary for the steam methane reforming reaction. Then, the thermochemical conversion performance of the HTPR was unveiled. Despite the uneven energy flux on the HTPR outwall, it still provided a uniform thermal boundary with a temperature of up to 750 °C because of its high thermal conductivity. Furthermore, the solar-thermochemical efficiency of the HTPR was about 41.0% after optimizing the operating parameters, surpassing that of the state-of-the-art solar thermochemical reactor. Finally, the heat loss of the HTPR and the heat transfer mode in the reactor cavity were analyzed. The radiation of the reactor outwall accounted for 44.5% of the total heat loss, and the thermal conduction was the major heat transfer mode in the cavity. This work deepens our understanding of the thermochemical conversion mechanism of the HTPR, paving the way for improving hydrogen yields.

Inverse Design of Local Solar Flux Distribution for a Solar Methanol Reforming Reactor Based on Shape Optimization

In this work, an inverse design method that couples the multi-physics model for a solar trough thermochemical reactor (SPTR) and shape optimization model is proposed to find out optimal solar flux distribution for maximizing overall reactor performance. The gradient-based segmentation method is applied to convert the continuous solar flux into step-like flux to guide the concentrator system design. Performance comparisons among uniform flux, linear decreasing flux, and the optimized non-linear flux are also conducted to discuss the reliability of SPTR performance improvement. The results show that the optimized non-linear solar flux can improve the methanol conversion, solar thermochemical conversion, and hydrogen yield of SPTR by 2.5, 3.3, and 2.4%, respectively, compared with the uniform flux. This is attributed to the fact that the optimized non-uniform flux distribution enhances the synergy between temperature and reaction fields, and achieves a better match between spatial solar flux supply and local energy demand by reactions. Also, it is shown that the optimized step-like flux, achieved by regressing the optimized non-linear flux, can perfectly maintain SPTR performance and is effective in boosting SPTR performance under different operating conditions.

Thermodynamic performance of solar-driven methanol steam reforming system for carbon capture and high-purity hydrogen production

• A solar MSR system via HPM reactor for high-purity hydrogen generation is proposed. • The conversion rate of methanol could exceed 99.9% between 150 and 250 °C. • The solar-to-fuel efficiency can reach 55.22% with 94.1% hydrogen separation. • Thermodynamic efficiencies of the system around a year is stable. • Standard coal saving rate is as high as 0.63 t/m 2 annually in this reactor. Solar energy storage via a thermochemical approach is a promising method to realize the efficient utilization of discontinuous sunlight. Traditional solar thermochemical conversion with the assistant of hydrocarbon requires the purification process of products, and a relatively high reaction temperature limits its thermodynamic efficiency. In this work, a thermodynamic study on solar-driven methanol steam reforming reaction in a Pd-Ag membrane reactor has been conducted. The partial pressure, conversion rate, and thermodynamic efficiency are studied and analyzed under different reaction temperatures (150–250 ˚C) and permeate pressures (10 −3 -1 bar). Via the membrane reactor, the equilibrium of reaction shifts forward and the conversion rate of methanol can reach as high as above 99.9% in 150–250 ˚C, and purified hydrogen and carbon dioxide can be collected separately. Under the optimized reaction temperature and pressure, the solar-to-fuel efficiency and exergy efficiency can reach as high as 55.2% and 74.79%, respectively. Due to the utilization of solar energy and membrane reactor, the annual coal saving rate and carbon dioxide reduction rate are predicted to be 0.63 t/m 2 and 1.53 t/m 2 , respectively. This thermodynamic research provides an efficient approach for solar energy conversion and storage without CO 2 emission.

Hydrogen production by solar fluidized bed reactor using ceria: Euler-Lagrange modelling of gas-solid flow to optimize the internally circulating fluidized bed

To perform solar thermochemical conversion, by utilizing high-temperature solar heat as an energy source and redox metal oxide particles as a chemical source, fluidized bed reactor has been developed to produce clean fuels. In this study, an Euler-Lagrange model has been developed for the simulation of particulate and gas flows in fluidized bed reactor for hydrogen production, by two-step water splitting cycles, using solar beam down concentrating system. The solid phase is modelled by Discrete Element Method (DEM) using soft-sphere approach and the gas phase is modelled as continuum by Navier-Stokes equations. The flow behavior of newly developed fine ceria particles has been analyzed for various conditions using the 30 kWth fluidized bed reactor prototype. The effect of particle size on the flow-dynamics at the spout, fountain periphery and annulus of the internally circulating fluidized bed has been examined. The results indicate that the particle size distribution should be minimized as much as possible to avoid the segregation behavior of different size particles.

Application of Porous Materials for CO2 Reutilization: A Review

CO2 reutilization processes contribute to the mitigation of CO2 as a potent greenhouse gas (GHG) through reusing and converting it into economically valuable chemical products including methanol, dimethyl ether, and methane. Solar thermochemical conversion and photochemical and electrochemical CO2 reduction processes are emerging technologies in which solar energy is utilized to provide the energy required for the endothermic dissociation of CO2. Owing to the surface-dependent nature of these technologies, their performance is significantly reliant on the solid reactant/catalyst accessible surface area. Solid porous structures either entirely made from the catalyst or used as a support for coating the catalyst/solid reactants can increase the number of active reaction sites and, thus, the kinetics of CO2 reutilization reactions. This paper reviews the principles and application of porous materials for CO2 reutilization pathways in solar thermochemical, photochemical, and electrochemical reduction technologies. Then, the state of the development of each technology is critically reviewed and evaluated with the focus on the use of porous materials. Finally, the research needs and challenges are presented to further advance the implementation of porous materials in the CO2 reutilization processes and the commercialization of the aforementioned technologies.

Analysis of biomimetic hierarchical porous structure regulating radiation field to improve solar thermochemical performance based on minimum Gibbs free energy

Solar energy is the source of energy required for the dry methane reforming (DMR). In the high temperature field induced by concentrated solar energy, the spatial distribution of radiation intensity has a significant impact on the solar thermochemical performance. Based on principle of minimum Gibbs free energy (Gmin), the idea of regulating radiation field to match solar thermochemical energy conversion on-demand is proposed. To improve solar thermochemical conversion efficiency, biomimetic hierarchical porous structure is introduced as solar thermochemical reactor, which can optimize both the radiation field and temperature field. The analysis model of solar driven DRM is established, combined with user-defined functions (UDFs). The effects of pore diameter combinations along the direction of L and R on the reforming properties are studied. The results show that by designing biomimetic hierarchical porous structure, the temperature of solar thermochemical reactor can approach the thermodynamic temperature (1050 K), and finally the methane conversion is improved by up to 7%.

A mid/low-temperature solar-driven integrated membrane reactor for the dehydrogenation of propane – A thermodynamic assessment

Solar thermochemical conversion is an effective method for solar energy storage, and propane dehydrogenation is one popular technology to generate propylene and hydrogen, while the high temperature required in the reaction limits its efficiency and utilization. In this research, a solar–driven hydrogen permeation membrane reactor system for propane dehydrogenation is proposed for efficiently generating pure hydrogen and propylene in a mild temperature range, which can decrease the heat loss and increase the conversion rate, thereby converting low–grade solar thermal energy into high–grade chemical energy. Using the method of numerical simulation, the thermodynamic, kinetic, and environmental performances of the system are analyzed at different temperatures (250–500 °C) and H2 permeate pressures (10–5–10–2 bar). The C3H8 conversion rate, C3H6 selectivity, and C3H6 yield can achieve 99.2%, 99.1%, and 98.3% at 400 °C, 10–5 bar with the assistance of hydrogen separation. The first–law thermodynamic efficiency, solar–to–fuel efficiency, and exergy efficiency of the system are calculated to be 93.1%, 33.6%, and 73.4% (400 °C, 10–4 bar), respectively. The annual standard coal savings and carbon dioxide reduction rates are calculated to be 279.8 kg/(m2·year) and 685.5 kg/(m2·year) (400 °C, 10–5 bar). This study demonstrates the feasibility of a solar collector integrated with a membrane reactor for efficient solar energy storage via C3H8 dehydrogenation and provides guidance for further experimental research.

A distributed energy system integrating SOFC-MGT with mid-and-low temperature solar thermochemical hydrogen fuel production

Solar thermochemical hydrogen production with energy level upgraded from solar thermal to chemical energy shows great potential. By integrating mid-and-low temperature solar thermochemistry and solid oxide fuel cells, in this paper, a new distributed energy system combining power, cooling, and heating is proposed and analyzed from thermodynamic, energy and exergy viewpoints. Different from the high temperature solar thermochemistry (above 1073.15 K), the mid-and-low temperature solar thermochemistry utilizes concentrated solar thermal (473.15–573.15 K) to drive methanol decomposition reaction, reducing irreversible heat collection loss. The produced hydrogen-rich fuel is converted into power through solid oxide fuel cells and micro gas turbines successively, realizing the cascaded utilization of fuel and solar energy. Numerical simulation is conducted to investigate the system thermodynamic performances under design and off-design conditions. Promising results reveal that solar-to-hydrogen and net solar-to-electricity efficiencies reach 66.26% and 40.93%, respectively. With the solar thermochemical conversion and hydrogen-rich fuel cascade utilization, the system exergy and overall energy efficiencies reach 59.76% and 80.74%, respectively. This research may provide a pathway for efficient hydrogen-rich fuel production and power generation.

Solar Thermochemical Green Fuels Production: A Review of Biomass Pyro-Gasification, Solar Reactor Concepts and Modelling Methods

This paper addresses the solar thermochemical conversion of biomass or waste feedstocks based on pyro-gasification for the clean production of high-value and energy-intensive fuels. The utilization of solar energy for supplying the required process heat is attractive to lower the dependence of gasification processes on conventional energy resources and to reduce emissions of CO2 and other pollutants for the production of high-value chemical synthetic fuels (syngas). Using concentrated solar energy to drive the endothermal reactions further allows producing more syngas with a higher gas quality, since it has not been contaminated by combustion products, while saving biomass resources. The solar-driven process is thus a sustainable and promising alternative route, enabling syngas yield enhancement and CO2 mitigation, thereby potentially outperforming the performance of conventional processes for syngas production. This review presents relevant research studies in the field and provides the scientific/technical knowledge and background necessary to address the different aspects of the solar gasification process. An overview of the available solar concentrating technologies and their performance metrics is first introduced. The solar gasifier concepts and designs that were studied from lab to industrial scale are presented, along with their main benefits and limitations. The different management strategies proposed to deal with solar energy variations are also outlined, as well as the major pilot-scale applications and large-scale system level simulations. A specific emphasis is provided on the spouted bed technology that appears promising for the gasification process. Finally, the main modeling approaches of pyro-gasification and kinetics for simulation of gasifiers are described. This study thus provides a detailed overview of the efforts made to enhance the thermochemical performance of solar-assisted biomass gasification for synthetic fuel production.

Solar-Driven Chemical Looping Methane Reforming Using ZnO Oxygen Carrier for Syngas and Zn Production in a Cavity-Type Solar Reactor

Converting sunlight into chemical fuels and metal commodities, via solar thermochemical conversion processes, is an attractive prospect for the long-term storage of renewable energy. In this study, the combined methane reforming and ZnO reduction in a single reaction for co-production of hydrogen-rich syngas and metallic Zn was demonstrated in a flexible solar thermochemical reactor prototype, driven by highly concentrated sunlight. Using solar energy as the process heat source in chemical-looping methane reforming with the ZnO/Zn oxygen carrier is a means to reduce the dependence on conventional energy resources and to reduce emissions of CO2 and other pollutants, while upgrading the calorific value of the feedstock for the production of energy-intensive and high-value chemical fuels and materials. On-sun experiments were carried out with different operating parameters including operating temperatures (800–1000 °C), inlet methane flow-rates (0.1–0.4 NL/min), and inlet ZnO feeding-rates (0.5–1.0 g/min) both in batch and continuous modes under reduced (0.15 and 0.45 bar) and atmospheric pressures (0.90 bar), thereby demonstrating solar reactor flexibility and reliability. As a result, increasing the temperature promoted net ZnO conversion at the expense of favored methane cracking reaction, which can be lowered by decreasing pressure to vacuum conditions. Diminishing total pressure improved the net ZnO conversion but favored CO2 yield due to insufficient gas residence time. Rising ZnO feeding rate under a constant over-stoichiometric CH4/ZnO molar ratio of 1.5 enhanced ZnO and methane consumption rates, which promoted Zn and syngas yields. However, an excessively high ZnO feeding rate may be detrimental, as ZnO could accumulate when the ZnO feeding rate is higher than the ZnO consumption rate. In comparison, continuous operation demonstrated greater performance regarding higher ZnO conversion (XZnO) and lower methane cracking than batch operation. High-purity metallic Zn with a well-crystallized structure and of micrometric size was produced from both batch and continuous tests under vacuum and atmospheric pressures, demonstrating suitable reactor performance for the solar thermochemical methane-driven ZnO reduction process. The produced Zn metal can be further re-oxidized with H2O or CO2 in an exothermic reaction to produce pure H2 or CO by chemical-looping.

Combined ZnO reduction and methane reforming for co-production of pure Zn and syngas in a prototype solar thermochemical reactor

Solar thermochemical conversion processes offer a promising avenue for storing intermittent solar energy into high value chemical products. A directly-irradiated packed-bed reactor was developed to experimentally investigate the solar thermochemical methane reforming combined with ZnO reduction for co-production of Zn and syngas in a single process. On-sun experiments were conducted to demonstrate reliable process operation and to identify optimal operating conditions, considering the impact of reduced and atmospheric pressures, temperatures, and inlet methane flow-rates. A pressure decrease enhanced net ZnO conversion at the expense of lowered syngas selectivity attributed to the CO2 increase because of insufficient gas residence time. Increasing temperature promoted syngas production rate, yield, ZnO and methane conversion at the expense of favored methane cracking which can be alleviated by lowering pressure. The maximum H2 and CO yields of 28.4 and 4.6 mmol/gZnO, and the maximum net ZnO conversion and methane conversion (67.3% and 57.6%) were achieved from non-isothermal tests. The calorific value of chemical products was upgraded by solar energy (U up to 1.31), and ηsolar-to-chemical = 3.9% was achieved. Pure and highly reactive metallic Zn was produced with well crystallized structure in micrometric size, demonstrating the feasibility of combined solar methane reforming and ZnO reduction for synthetic fuel production and sustainable Zn metallurgy.

Solar thermochemical conversion of CO 2 into fuels u sing gadolinium sesquioxide: A thermodynamic efficiency analysis

Solar thermochemical conversion of <scp> CO ₂ </scp> into fuels u <scp>sing gadolinium</scp> sesquioxide: A thermodynamic efficiency analysis

Mathematical modelling of the solar-driven steam reforming of methanol for a solar thermochemical micro-fluidized bed reformer: thermal performance and thermochemical conversion

A solar thermochemical reformer/receiver which combines a ST-μFB reformer and a catalytic bed of micro-sized particles offers a novel approach for the solar-driven catalytic steam reforming of methanol (SDCSR-MeOH) method. Heat transfer, mass transfer and solar thermochemical conversion performance have a great significance on the SDCSR-MeOH method due to high interfacial absorption surface of micro-sized particles. The solar radiation has been coupled to the ST-μFB reformer as a novel driving energy for conducting the endothermic reactions of methanol (CH3OH) inside ST-μFB reformer to produce solar H2. Solar H2 had won an important role as renewable feedstocks for different chemical processes and particularly in fuel cells applications. A non-isothermal mathematical model was described by a set of partial differential equations (PDEs) that couples to a complex kinetic model of the SDCSR-MeOH employing the Cu/ZnO/Al2O3 catalyst. The system of novel PDEs has been transformed into simpler system of ordinary differential equations using the coupled integral equation approach. Validation results demonstrate that the two validated cases for the reaction temperature against the simulated results by authors had reached a good fit as well as the solar thermochemical conversion of CH3OH. The temperature profiles of the gas phase, solid phase and ST-μFB reformer wall were simulated at three different positions from ST-μFB reformer. The reactant and product distributions inside ST-μFB reformer were analysed at two different reaction temperatures. The effect of the reaction temperature was studied on the conversion of CH3OH and yield of H2. In addition, the action of the weight hourly space velocity has been analysed on the conversion of CH3OH.

Solar Redox Cycling of Ceria Structures Based on Fiber Boards, Foams, and Biomimetic Cork-Derived Ecoceramics for Two-Step Thermochemical H2O and CO2 Splitting

Solar thermochemical conversion of H2O and captured CO2 is considered for the production of high-value solar fuels and CO2 valorization, using non-stoichiometric oxygen-exchange redox materials. Th...

Co-precipitation synthesized nanostructured Ce0.9Ln0.05Ag0.05O2\u2212\u03b4 materials for solar thermochemical conversion of CO2 into fuels

Synthesis, characterization, and application of Ce0.9Ln0.05Ag0.05O2−δ materials (where, Ln = La, Pr, Nd, Sm, Gd, Tb, Dy, Er) for the thermochemical conversion of CO2 reported in this paper. The Ce0.9Ln0.05Ag0.05O2−δ materials were synthesized by using an ammonium hydroxide-driven co-precipitation method. The derived Ce0.9Ln0.05Ag0.05O2−δ materials were characterized via powder X-ray diffraction, scanning electron microscope, and electron diffraction spectroscopy. The characterization results indicate the formation of spherically shaped Ce0.9Ln0.05Ag0.05O2−δ nanostructured particles. As-prepared Ce0.9Ln0.05Ag0.05O2−δ materials were further tested toward multiple CO2 splitting cycles by utilizing a thermogravimetric analyzer. The results obtained indicate that all the Ce0.9Ln0.05Ag0.05O2−δ materials produced higher quantities of O2 and CO than the previously studied pure CeO2 and lanthanide-doped ceria materials. Overall, the Ce0.911La0.053Ag0.047O1.925 showed the maximum redox reactivity in terms of O2 release (72.2 μmol/g cycle) and CO production (136.6 μmol/g cycle).

Solar thermochemical conversion of CO2 via erbium oxide based redox cycle

AbstractInvestigation of the viability of the erbium oxide‐based solar thermochemical CO2 splitting cycle is reported. This study aimed to explore the effect of partial thermal reduction (TR) of Er2O3 on the thermodynamic process parameters desirable to design a solar reactor system for the erbium oxide‐based CO2 splitting (ErO‐CS) cycle. First, the percentage TR of Er2O3 is estimated as a function of the TR temperature (). Acquired results indicated that to achieve a percentage TR of Er2O3 in the range of 5–100%; the solar reactor has to be functioned in the temperature range of = 2327–2677 K. The solar energy required to drive the ErO‐CS cycle () was observed to be on the higher side due to the obligation of the elevated values of . This rise in the as a function of percentage TR of Er2O3 reflected in a decrease in the solar‐to‐fuel energy conversion efficiency (). The maximum = 4.04% is achieved for a percentage TR of Er2O3 = 25% ( = 2432 K). By employing 100% heat recuperation, the (for percentage TR of Er2O3 = 25%) increased up to 5.79%. © 2020 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

Enhanced solar radiation absorption by carbon dioxide in thermodynamic nonequilibrium: A computational study

The conversion of carbon dioxide (CO2) into higher value products using solar energy can help fulfill the increasing need for fuels and chemicals while mitigating environmental emissions. Solar thermochemical conversion approaches rely on the absorption of radiative energy by a solid catalytic medium. The direct absorption of solar energy by CO2 before reaching the catalyst could lead to more efficient conversion. Greater solar photon absorption can be achieved through the use of an electrical discharge to drive CO2 to a low-temperature plasma state in which free electrons and heavy-species are in a state of Non-Local Thermodynamic-Equilibrium (NLTE). The absorption of solar energy by a plasma-enhanced solar reactor for atmospheric pressure CO2 conversion is analyzed via zero- and one-dimensional models. The models are comprised by the spectral radiative transfer equation (RTE) and energy conservation equations for electrons and heavy-species. Radiative properties are computed by a line-by-line radiative code and transport properties using kinetic theory. Simulation results for a representative 10 cm long solar-plasma reactor show up to 48% and 90% net-absorption of solar radiation by CO2 in NLTE at electron temperatures of 1 and 2 eV, respectively, and heavy-species temperatures of ~2000 K, common in solar thermochemical processes. In contrast, less than 0.2% of solar radiation is absorbed by CO2 in LTE under similar conditions. The results suggest that solar-plasma direct-receiver reactors, due to increased direct solar energy absorption, have the potential for greater efficiency CO2 decomposition processes.

Solar thermochemical conversion of carbonaceous materials into syngas by Co-Gasification

Transitioning from fossil fuel based energy sources to more viable and alternative renewable energy sources requires intermediary methods that bridge the gap between existing technology and newer innovative renewable technologies. The objective here is to provide for a more reliable power source that can extend its reach to even the remotest rural areas.This paper provides a numerical method that tests the possibility of coupling a solar energy heat source with a co-gasification process dependent on biomass and coal for producing syngas throughout all hours of the day. A hybrid reactor that is modeled by the Monte Carlo ray tracing method for its geometric and maximum temperature is obtained in the cavity. Numerous factors were accounted for that determined the performance of the reaction in the indirectly irradiated fluidized bed solar reactor. The co-gasification modeling calculation utilized 50% lignite coal and 50% olive pomace with oxygen and steam to estimate the gasification performance parameters.The co-gasification process, using solar energy as the heat source, had in fact shown to produce clean syngas. Oxygen and steam were mixed to ensure the continuous production of syngas, as oxygen was critical in enabling some of the feedstock to be combusted during the low/absence of solar energy. The stoichiometric equilibrium model was also used to estimate the gasification performance and the effect of the gasifying agent ratios. The results also indicate that the effect of variation of O2: C ratio is an important factor that affects both the bed temperature and the carbon conversion, whilst the negative impact of combustion was apparent on the H2:CO, cold gas ratio, solar-fuel efficiency, and CO2 production. Changing H2O:C ratio was less apparent but still significant in the co-gasification process.