Solar CO2 splitting via a two-step thermochemical cycle (TSTC) has emerged as a promising technology for solar fuel production. However, the extreme reduction temperature (Tred) required to achieve optimal CO yields poses challenges in reactor design, operation, and solar-to-fuel energy efficiency. In this study, a two-step electrothermochemical cycle (TSEC) for CO2 splitting into CO using a solid oxide electrochemical cell (SOEC) is presented with the objective of reducing Tred and improving solar-to-fuel energy efficiency. The investigations reveal that TSEC exhibits the capability to decrease Tred from 1500 degrees C to 1000 degrees C, while simultaneously maintaining a substantial CO yield of 550 mu mol/g. Moreover, the efficiency analysis demonstrates that TSEC achieves a superior solar-to-fuel energy efficiency of 20.4 %, outperforming 4.1 % of conventional TSTC. In sum, this study demonstrates a novel approach to solar fuel production, enabling high and stable CO2-to-CO conversion at moderate temperatures while maintaining high energy efficiency.

This study aims to conduct a comprehensive comparison of three technologies for producing renewable natural gas (RNG) from biomass, evaluating their technical, economic, and environmental perspectives: (i) Catalytic hydrothermal gasification (CHG) technology; (ii) Gasification and methanation (G&M) technology; (iii) Anaerobic digestion (AD) technology. Energy analysis reveals that the CHG system achieves the highest energy efficiency (81.30 %), attributed to its superior energy recovery and utilization capabilities. The AD system exhibits 50.17 % lower energy efficiency compared to the CHG system, primarily due to incomplete biomass conversion into biogas. Exergy analysis indicates that the CHG system demonstrates the highest exergy efficiency (63.38 %). The reaction unit constitutes the primary source of exergy losses across the three RNG production systems. Energy utilization diagram (EUD) analysis of the RNG production reaction in the CHG and G&M systems reveals that the CHG system experiences lower exergy losses, owing to its single-step conversion and milder reaction conditions. Economic evaluation highlights that the CHG system offers the most favorable economic performance, driven by its moderate investment cost (24.50 M), high RNG and steam production, and a competitive RNG break-even cost of 0.41 /Nm3. Raw material costs and by-product steam prices are critical factors influencing the economic viability of the process. Life cycle assessment reveals that the CHG and G&M systems exhibit superior environmental performance, whereas the AD system performs poorly due to the significant volume of digestate requiring treatment.

Refrigerant flash spray cooling, which offers high heat flux dissipation at low temperatures, holds significant potential for thermal management of high-power electronic devices. While surface structure design can further amplify heat transfer performance, the lack of systematic methodologies to address the complexities of spray cooling has hindered progress. This study establishes a multi-physics computational framework that couples twophase flash spray dynamics, liquid film heat transfer, and solid heat conduction to systematically optimize macro-structured surfaces. After validating the model against experimental data, the effects of surface geometry (flat, square, straight and pyramid fins) and dimensional parameters on cooling performance were analyzed. The pyramid structure demonstrated superior performance, achieving a 9 K reduction in surface temperature and a 70 % increase in effective heat transfer coefficient compared to the flat surface. Quantitative analysis revealed that optimal macro-structured design hinges on maximizing effective heat transfer area while ensuring uniform liquid film distribution via controlled droplet dynamics. Further parametric studies on nine pyramid geometries identified a base length of 1 mm and height-to-edge ratio of 0.7 as the optimal configuration, balancing heat transfer enhancement and manufacturing costs through a newly proposed Composite Heat Transfer Factor (CHTF). This work provides a mechanistic framework for designing enhanced surfaces in spray cooling systems, bridging critical gaps in both theoretical understanding and engineering application.

Proton ceramic electrolysis cell (PCEC) can efficiently convert electrical energy into fuels like hydrogen by utilizing renewable energy at lower temperatures compared to solid oxide electrolysis cell (SOEC). Nonetheless, the advancement of PCEC is currently hindered by their low Faradaic efficiency (FE). The prevailing models for calculating FE are often based on defect flux or lack a clear elucidation. In contrast, we present a method for calculating FE based on the change in gas flow rate between the inlet and outlet. This is achieved by establishing accurate electric field boundary conditions, with particular emphasis on the leakage current at the electrode-electrolyte interface. The accuracy of the electric field boundary conditions is verified by comparing the calculated FE with experiments, showing a maximum relative error of less than 13.1 % at high current densities. The effects of various operating parameters on cell performance, especially on FE, are systematically studied. The results reveal that as the steam molar fraction rises from 0.1 to 0.9, FE experiences a substantial increase from 76.5 % to 95.3 %. It is also found that the FE has an optimal peak relative to the current density due to the influence of temperature, for instance, reaching 78.1 % at 600 degrees C and a current density of -0.8 A cm- 2. In conclusion, a multi-physics model incorporating detailed electric field boundary conditions is established to enable the direct calculation of FE. This advancement not only improves the model's accuracy but also offers valuable guidance for the design and operation of PCEC.

Developing energy storage system based on lithium-ion batteries has become a promising route to mitigate the intermittency of renewable energies and improve their utilization efficiency. In this context, thermal management is needed to maintain battery temperature and thermal uniformity without consuming significant power. However, conventional cooling plates are usually built via trial-and-error methods, which suffer from trade-off problem between thermal performance and flow resistance. In this study, a multi-physics model incorporating electrochemical, hydrodynamic, and thermal fields is proposed for a battery pack. Meanwhile, a multi-objective topology optimization is introduced to freely evolve the distribution of fluid domain embedded into cold plate under specified constraint conditions. The multi-objective function is formulated using normalized additive weighting approach. Based on this, the mapping relations between design parameters (i.e., Reynold number and weighting coefficients) and performance of cold plate can be established via response surface method, and it is further optimized with a non-dominated sorting genetic algorithm. Results show that topological channel structure performs lower average temperature rise than traditional straight, serpentine, and hexagonal cold plates. When the mass flow rate ranges from 1 x 10-3 to 15 x 10-3 kg s- 1, Nusselt number difference are varied from 1.33 to 5.90 compared to straight cold plate, which are improved by 15.6 to 42.2 %, respectively. This indicates that optimized cold plate achieves better heat exchange ability under the same inlet conditions. Besides, optimal design allows for excellent thermal uniformity without excessive pressure drop compared to serpentine cold plate.

Battery energy storage systems become increasingly important to address the intermittency of renewable energies, but their widespread adoption is still hindered by thermal concerns. However, a single thermal management strategy cannot ensure the overall performance of energy storage battery systems. In this study, a hybrid strategy combining topological fin structure, phase change material, and active liquid cooling is established for 280 Ah lithium-ion battery pack. A fluidic-thermal-phase change coupled model is built and verified experimentally. Meanwhile, a novel comprehensive evaluation parameter is defined to feature the overall performance of thermal management system. Based on this, comparative investigations are conducted to assess the efficiency of three cooling strategies. Despite additional weight caused by hybrid design, topological fin structure not only constructs the thermal conduction in phase change material but also dissipates the accumulated heat by connecting cold plate. Additionally, the impacts of fin fraction, thickness of phase change material, and inlet velocity are systematically explored using single-factor analysis. Furthermore, a surrogate-based model is utilized to reveal the interactions between design parameters and system performance, while accomplishing a global optimization. In contrast to original design, comprehensive evaluation parameter is reduced by 0.218, 0.273, 0.256, and 0.2 for discharge rates of 0.25, 0.5, 0.75, and 1C, respectively.

Protonic semiconductor oxide fuel cells based on semiconductor oxide proton conductors are emerging as very promising next-generation solid oxide fuel cell (SOFC) technology for low-temperature operation. Currently, Ni0.8Co0.15Al0.05LiO2 (NCAL) has been widely employed as a symmetric electrode for these novel SOFCs due to its good catalytic activities to both hydrogen oxidization and oxygen reduction reactions, achieving excellent performance at 550 degrees C. However, the interface between electrode and electrolyte needs to be modified to further reduce electrode polarization. In this study, perovskite-related Sm2Ba1.33Ce0.67Cu3O9 (SBCC) was introduced as an interlayer electrode between a layered NCAL electrode and fluorite CeO2 electrolyte to form a heterojunction regulating the charge transfer at the electrode/electrolyte interface. A symmetric NCAL|SBCC bilayer electrode dropped the polarization resistance of a single cell by 41% compared to the NCAL electrode, from 0.24 to 0.14 Omegacm2 at 550 degrees C. The peak power density was enhanced by 25% from 744 to 933 mWcm-2. Such better performance of bilayer heterojunction electrodes originates from energy band matching at cathode side and Schottky junction effect at anode side, improving charge separation.

Solar-driven high temperature H2O electrolysis provides a promising path for green H2 production. In this work, a novel integrated solar-driven high temperature H2O electrolysis reactor was proposed, and its thermal and energy conversion performance was evaluated based on an optical-thermal-chemical coupling model. The results demonstrated that the temperature difference on the tubular SOEC under highly uneven solar radiation can be lowered by the novel multi-layer structure. A solar-to-fuel (STF) efficiency of 23.0 %, which is higher than those from references, was predicted due to close integration/coupling of the various processes in the reactor, and it may still be improved by increasing the direct normal irradiance (DNI) and operation voltage. The results also emphasize the importance of reaction kinetics to the efficiency of the system. Contrary to the thermodynami estimation based on equilibrium, the efficiency in exothermic mode is shown to be higher than that in endothermic mode owing to way better kinetics of the former. The reactor provides a simple but effective strategy for addressing the temperature gradient caused by the uneven solar radiation and efficient heat exchange/recovery between the heating and electrolysis processes. Its modular design facilitates scaling, optimization and maintenance. The insights shown can be of guiding significance for designing and practical realization of the integrated reactor concept.

Supercritical water oxidation (SCWO) reactor is crucial for hydrogen production through autothermal gasification, where hydrogen oxidation provides heat for supercritical water gasification. However, the dynamic behavior and control strategies of industrial-scale SCWO reactors remain insufficiently explored. A computationally efficient reactor network model was developed to address this. Cold start and open-loop dynamic simulations were conducted to investigate the effects of variations in inlet gasification product mass flow rates, gasification product temperature, and oxygen mass flow rate. Results indicate that the fluid temperature stabilizes within 2 min, while the wall temperature takes approximately 1.1 h. Under slow disturbances, the outlet temperature exhibits quasi-static characteristics. The oxygen mass flow rate significantly influences reactor performance, and a dynamic matrix control (DMC) scheme using it as the control variable is designed to regulate the outlet temperature. The oxygen mass flow rate changes from 450.54 kg/h to 392.25 kg/h and 509.59 kg/h with outlet temperatures set at 850 degrees C and 950 degrees C, respectively, within 180 s. A comparison of disturbance rejection performance between DMC and PID controllers reveals that DMC responds faster and reduces overshoot, demonstrating superior performance. This study provides insights into the dynamic behavior and operational flexibility of SCWO reactors in engineering applications.

Solar-driven H2O/CO2 splitting via two-step thermochemical cycle is a promising path for renewable fuel production. However, the energy losses caused by the high solar thermal temperature and the significant technical challenges in oxygen carrier heat recovery have long hindered its efficiency improvement. In this work, the twostep cycle was proposed to couple with a thermal power generation process to recover the process heat, and the electricity generated was proposed to be used in the reduction step, for which the solar heating and reduction processes can be decoupled. Thermodynamic evaluation shows that an efficiency advantage over the traditional cycling mode can be expected even when the solar thermal temperature is 50 K lower. It is 16.1 % at Tred = 1773 K and Tsolar= 1723 K, significantly higher than that of the traditional cycle working at Tred = 1773 K with 95 % gas heat and 40 % solid heat recovered (13.6 %). The novel cycling mode not only provides a practical heat recovery strategy, but also creates a completely new space for further lowering the solar thermal temperature and brings about obvious engineering advantages. It is supposed to be of important implications in promoting the practical application of the technology.

The supercritical water diluted flamelet generated manifolds (SCWD-FGM) model was newly developed for three-stream hydrothermal combustion systems. It was comprehensively compared with the partially stirred reactor (PaSR) model by modeling a wall-cooled reactor. The results showed that the SCWD-FGM model can predict the mixing of fuel, oxidizer, and cooling water similar to the PaSR model by introducing the dilution variable. The peak temperature along the central axis predicted by the SCWD-FGM model is slightly lower than the PaSR model under adiabatic conditions due to different treatments of turbulent effects and the limited resolution of the SCWD-FGM table. The temperature profiles at 3 mm and 4 mm from the central axis predicted by the two combustion models under non-adiabatic conditions agree with the experiment data. The SCWD-FGM model can predict most species concentrations similarly to the PaSR model except for HO2 and H2O2 radicals. The effect of radiation modeling is similar for the two combustion models since they only affect the radiative source term through the calculated local temperatures. The computational cost for the SCWD-FGM model is 11.2 % of that required for the PaSR model under adiabatic conditions and 14.9 % under non-adiabatic conditions.

Hydrogen is emerging as a clean and renewable energy source indispensable to the realization of a carbon neutral society. Inspired by the prospect of sustainable and carbon-free energy supplies, hydrogen has been widely utilized in various combustion engines. This review article highlights recent progress in understanding hydrogen combustion chemistry in the gas phase. At first, the explosion limits of hydrogen-oxygen mixtures are discussed to demonstrate the intrinsically nonmonotonic kinetic behavior. Fundamental experiments of hydrogen combustion in terms of ignition delay times, laminar flame speeds and speciation are systematically summarized, and the value of the reported data is discussed. Furthermore, effective strategies towards more accurate experimental diagnostics are outlined. The current status of detailed and simplified kinetic model development is then appraised, followed by a critical discussion on the rate constants of important elementary reactions that are still in dispute. The essential importance of the comprehensiveness of chemical fidelity for mechanisms at the detailed and reduced levels is emphasized. Subsequently, the knowledge of ozone-assisted oxidation of hydrogen is overviewed. The effects of ozone addition on the characteristics of hydrogen oxidation are analyzed, including ignition temperature, flame burning velocity and flame structure. The ozone sub-mechanism and associated reaction rates are also carefully assessed. Finally, concluding comments and an outlook towards future research on gas-phase hydrogen combustion chemistry are presented.

Solid oxide fuel cell(SOFC)is a promising energy con-version device because of its high efficiency and fuel/oxidant flexibility,enabling the direct conversion of chemical energy to electrical power.By using N2O as an oxidant instead of air,we develop a dual-phase catalyst La0.6Sr0.4Co0.2Fe0.8O3-δ-Gd0.1Ce0.9O2-δ(LSCF-GDC),which exhibits efficient bi-functionality as a cathode for SOFC,synergistically pro-moting simultaneous N2O decomposition and oxygen reduction kinetics.

With the escalating energy density of lithium-ion batteries, thermal-driven issues including capacity fade and thermal inconsistency have become critical challenges. This study develops a novel and cost-effective battery thermal management system (BTMS) integrating heat pipes with two-phase immersion cooling to address these limitations. Five heat pipe-based thermal management strategies are systematically compared: air cooling, liquid cooling, enhanced counterflow liquid cooling, phase change material cooling, and two-phase immersion cooling. The proposed system demonstrates superior performance, achieving optimal temperature control with the maximum temperature (Tmax) rise below 5.1 degrees C and maximum temperature difference (Delta Tmax) under 1.8 degrees C even at 9C discharge. Long-term cycling tests reveal the system's outstanding durability, maintaining temperature rise below 0.3 degrees C (Tmax) and 0.2 degrees C (Delta Tmax) after 1200 cycles while remaining 85.5% state-of-health, outperforming conventional designs. Parametric studies identify an optimal configuration comprising five heat pipes with immersion depth >= 80%, which maintains temperatures below 34.9 degrees C even under extreme 9C operating conditions. These findings provide critical design guidelines for next-generation BTMS, highlighting the synergistic benefits of heat pipe conduction and two-phase immersion boiling for battery applications.

There are currently no reports about clusters in the supercritical water circulating fluidized bed (SCWCFB). Simulations were conducted to investigate the numbers, diameters, aspect ratios, circularity, and orientation angles of cluster in the riser of SCWCFB via two-fluid model across different flow velocities, solid circulation rates, pressures, and temperatures. The results show that cluster numbers are mainly between 10 and 80 per m(2). Clusters are more at the bottom but less at the top, and more near the wall but less at the center. Cluster diameters are mainly between 0.2 and 0.5 times the bed diameter. Clusters are large at the bottom but small at the top, and large at the center but small near the wall. Cluster aspect ratios are mainly between 0 and 1, indicating that most clusters have shorter width than their heights. Stream-like clusters are more likely to appear near the walls, and clusters at the center of the riser are more likely to be arch-shaped. Cluster circularity is mainly between 0.2 and 0.4, suggesting that the shapes of clusters are far from the roundness. The absolute values of cluster orientation angles are mainly between 75 degrees and 90 degrees, indicating that most clusters move in the vertical attitudes. High fluid velocities may facilitate cluster coalescence. (c) 2024 Published by Elsevier B.V. on behalf of Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.

The hydrodynamics of binary particle mixing in a gas-solid fluidized bed were measured by using the capacitance probe method. A novel output voltage signal processing method based on a double threshold was proposed. Originally employed for voidage measurement in monodisperse systems, the capacitance probe method has been successfully extended to assess bubble and mixing characteristics in binary systems by establishing bubble and emulsion phase search algorithms. Through direct comparison with digital image analysis (DIA), quantiles of 0.15 and 0.45 were determined as thresholds for identifying emulsion and bubble phase, respectively. Experimental results demonstrated that under steady-state conditions, the volume ratio of jetsam decreased with increasing bed height, while higher gas velocities enhanced longitudinal and transverse mixing. Average bubble size and rising velocity increased with both the probe height and gas velocity. An improved empirical correlation for bubble diameter was proposed based on variations in local bed mixing degree, yielding a relative error below 20%. The average bubble rising velocity exhibited a direct relationship with the bubble diameter. Relative errors of measured velocities obtained through the capacitance probe method, DIA method, and empirical relation all remained below 15% across each operating condition.

This work is devoted to the development of a novel polydisperse drag model based on particle type for bubbling fluidized beds. Traditional homogeneous drag models do not take into account the heterogeneous mesoscale structures, while this model is a mesoscale-structure-dependent drag model. The model combined with Energy Minimum Multiscale (EMMS) theory has been successfully applied to the simulation of polydisperse particle segregation. Four particle size distribution (PSD) systems (including a binary system with different sizes, a binary system with different sizes and densities, a normal PSD and a lognormal PSD) were selected to validate the model under various superficial gas velocities. The PSD was decomposed into several types of solids, each governed by its own set of hydrodynamic equations. The solution algorithm was able to find the heterogeneous index for each solid, which was dependent on both slip velocity and solid concentration. Experiments were subsequently conducted under identical conditions to compare the experimental data with the simulated data. The average relative error between the simulation data and the experimental data about the mean particle size distribution was less than 5%. These results indicated that the proposed model outperformed other drag models in accurately predicting particle segregation behavior.

Ammonia emerges a highly promising carbon-free hydrogen source, presenting a potential solution to the inherent challenges of hydrogen storage and transportation. Currently, the application of thermocatalytic ammonia decomposition for hydrogen production has become a focal point of scientific inquiry. Although several noble metal catalysts and membrane reactors have demonstrated commendable thermocatalytic performance, significant challenges such as high costs and substantial energy consumption persist. This paper first summarizes the current research status of various conventional thermocatalysts for ammonia decomposition, with a particular emphasis on the investigation of active components and supports. Recent findings indicate that state-of-the-art ruthenium-based catalysts can achieve over 90% conversion at temperatures below 400°C, with nearly 100% conversion at 450°C. Additionally, it reviews current research status of a novel self-heating catalyst. Furthermore, this paper collates findings in the domain of ammonia decomposition equipment and systems, emphasizing advancements in pertinent materials, reactor, and system. Subsequently, a brief evaluation of the economic viability of current thermocatalytic ammonia decomposition reveals that ammonia feedstock constitutes over 50% of the overall hydrogen production cost. Finally, we highlight that to firmly establish ammonia as a carbon-free hydrogen source, it is imperative to develop efficient non-noble metal catalysts and highly effective ammonia decomposition reaction systems capable of utilizing renewable energy sources. We believe that this approach represents an inevitable path forward in realizing ammonia’s vast potential as a sustainable and environmentally friendly hydrogen source.

Solar photocatalytic water splitting for hydrogen production represents an ideal approach to address the current energy and environmental challenges, while also achieving “carbon peak and carbon neutrality” goals. The incorporation of photothermal effect into photocatalysis enables dual utilization of both light and heat energies, resulting in improved solar-to-hydrogen efficiency. In this review, we first discussed the behavior of energy flow and mass flow, and the characteristics of photogenerated carrier throughout the photocatalytic water splitting process, with particular focus on the behaviors induced by photothermal effect. Subsequently, we elaborate on strategies for designing high-efficiency photothermal catalytic systems and novel photothermal–photocatalytic integrated systems based upon concentrating-photothermal coupling effects. We then illustrate the development and large-scale demonstrations that utilize concentrated solar irradiation. Finally, we outline the challenges and highlight the future research directions of photothermal catalysis toward hydrogen production from water. This review aims to provide fundamental references and principal strategies for efficient utilization of solar energy in photothermal catalytic processes.

Deep space exploration expands our understanding about the evolution history of solar system, while the future development heavily relies on the construction of energy systems and utilization of resources on the planet. This paper systematically reviewed the progress in the environmental control and construction technologies of space bases, extraterrestrial in situ resource utilization technology, energy systems, key technologies for planetary transportation platforms, and geological explorations. The current status, pros and cons of these technologies and systems are introduced and discussed. As an important artificial microenvironment in the space base, the environmental control and life support system (ECLSS) provides necessary resources for human. Sintering and additive manufacturing technologies demonstrate the potential to construct a space base with lunar regolith or simulants. The extraction and in situ utilization of resources on the Moon, including water ice, oxygen, and helium-3, are crucial to maintain life support for lunar exploration. Typical energy systems that can be used on the Moon include photovoltaic cell, Stirling power generation technology, closed Brayton cycle (CBC) system, Rankine cycle system, heat storage system, and integrated energy system. The CBC system has the highest thermal efficiency (39%) among them, making it suitable for late-period energy supply. The performance of various planetary rovers, the most important transportation platforms, are summarized. Through geological explorations, the resource distribution, content, and occurrence can be obtained. Perspectives on the future, promotions of environment adaptation, resource recovery, energy efficiency, and intelligence of the existing technologies are still needed to move forward on space explorations.