Cong Chen

Geological reservoirs have been widely applied in CO2 geological storage, strategic CH4 reserves, and emerging H2 subsurface energy storage systems. Among these applications, CO2 geological storage has become increasingly significant with the advancement of carbon-emission reduction goals. To enhance CO2 injectable mass in subsurface formations, this study investigates injection-strategy optimization in a complex thinly interbedded saline aquifer of the Zhujiang Formation in the Pearl River Mouth Basin. A three-dimensional flat-layered numerical model consisting of multiple reservoir and caprock layers was constructed, and multiphase, multicomponent numerical simulations were conducted to evaluate CO2 plume migration, bottomhole-pressure response, and storage-capacity evolution under different injection strategies and rate increments. Because direct trial-and-error optimization of variable-rate injection requires repeated full-physics simulations and is computationally expensive, an incremental injectivity index, H(t), was established from preliminary rate-increment tests to quantify the dynamic relationship between injection-rate variation and pressure response. By using H(t), the allowable injection-rate increment at a given stage can be estimated from the current pressure margin, thereby providing a computationally efficient basis for stage-wise rate adjustment. This rate–pressure relationship was further incorporated into a low-to-high stage-wise variable-rate optimization framework, which determines pressure-constrained injection rates under the coupled constraints of maximum allowable bottomhole pressure and CO2 upward migration. The results show that an excessively high initial injection rate can markedly increase the peak bottomhole pressure and exceed the maximum allowable bottomhole pressure. In contrast, the proposed H(t)-guided stage-wise variable-rate strategy mitigates early pressure buildup while improving the total injectable CO2 mass. The optimized strategy achieves a maximum injectable CO2 mass of 29.56 Mt, which is 19.56 Mt higher than that achieved by the constant 0.5 Mt/year injection-rate strategy, 1.28 Mt higher than that achieved by the annual-adjustment strategy, and 0.30 Mt higher than that achieved by the 0.25-year adjustment strategy. The proposed framework provides a practical and computationally efficient approach for injection-strategy design and single-well storage-capacity optimization in complex saline aquifers.

Long-duration energy storage (ES) has aroused widespread concern by virtue of its potential in renewable energy consumption and the achievement of carbon neutrality goals. Compressed Carbon Dioxide Energy Storage (CCES) works as one of the most attractive technologies for long-duration ES. However, efficient and economical CCES systems are still lacking. In the present study, two novel CCES systems have been proposed, namely Closed-CCES and Semi-open-CCES. Under typical design conditions, the Closed-CCES system achieves a cycle efficiency of 62.25%, whereas the Semi-open-CCES system, featuring simultaneous cooling, heating, and power outputs, attains a superior energy storage density (ESD) of 7.38 × 10⁷ J·m⁻³. Compared with comparable energy storage systems, the two proposed systems exhibit distinct advantages in cycle efficiency and energy storage density, respectively. As noted by exergy analysis, the key loss source of Closed-CCES is the heat exchanger HE2, while the loss of Semi-open-CCES is mainly concentrated in the thermal storage device HFT1. Sensitivity analysis shows that ambient temperature and thermal storage pressure slightly affect the performance of both systems, while heat exchanger efficiency impacts the performance of Closed-CCES more significantly. Economic assessments reveal that both systems outperform conventional technologies in levelized cost of electricity (LCOE). The Closed-CCES system demonstrates superior economic viability with a lower LCOE of 0.0808 $/kW·h versus 0.0985 $/kW·h for the Semi-open system, with the advantage persisting in various operational scenarios. Research results provide a basis for the practical engineering implementation of CCES technology, contributing to the broader pursuit of long-duration energy storage solutions for carbon neutrality.

In transcritical CO2 refrigeration systems, replacing the throttle valve with a two-phase ejector markedly enhances energy recovery during the expansion process. This study comprehensively reviews the application of supersonic flow visualization techniques in two-phase ejectors. The first section elucidates the internal flow states of the two-phase ejector and summarizes key indicators of interest in visualization experiments. The second section details various visualization methods applied to two-phase ejectors and synthesizes the main findings from previous experiments. The third section critically evaluates the advantages and limitations of each visualization approach. Finally, the conclusion outlines insights regarding the future integration of visualization techniques in CO2 refrigeration systems employing two-phase ejectors and emphasizes opportunities for further improvement and innovation.

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease in clinical practice. This study examined the effects of mulberry leaf aqueous extract (MLQE) on lipid metabolism and gut microbiota in mice with high-fat diet-induced NAFLD. Using network pharmacology, we identified key targets of mulberry leaf and stem’s constituents for NAFLD regulation and validated their ameliorative effects through animal experiments. Our results demonstrated that interventions with orlistat (HFO), swimming exercise (HFS), and MLQE (HFM) significantly reduced weight gain, lipid accumulation, and oxidative stress in mace compared to the high-fat control (HFC) group. Histopathological analysis revealed improvements in liver steatosis, hepatocyte arrangement, inflammation, and adipocyte deformation. Molecular analyses indicated decreased mRNA levels of lipid synthesis genes (sterol regulatory element-binding protein 1 (SREBP1), bile salt export pump (BSEP), small heterodimer partner (SHP), and stearoyl-CoA desaturase-1 (SCD1)) and increased protein levels of farnesoid X receptor (FXR) and SHP in the intervention groups, consistent with RNA-seq findings. Additionally, RNA-seq analysis showed upregulation of fibroblast growth factor 21 (FGF21) and suppressor of cytokine signaling 2 (SOCS2), aligning with protein level observations. The interventions also modulated gut microbiota composition, reducing the Firmicutes-to-Bacteroidetes (F/B) ratio and adjusting the abundance of Acetatifactor, Roseburia, and Parasutterella. These findings suggest MLQE as a promising therapeutic approach for NAFLD, with lipid-lowering, antioxidative, and gut microbiota-regulating effects. FGF21 and SOCS2 may be key targets in NAFLD treatment.

With the continuous growth of global energy demand, greenhouse gas emissions are also rising, leading to serious challenges posed by climate change. Carbon Capture, Utilization, and Storage (CCUS) technology is considered one of the key pathways to mitigate climate change. Among the CCUS technologies, CO₂ storage in offshore saline aquifers has gained significant attention in recent years. This paper conducts an in-depth analysis of the Sleipner and Snøhvit projects in Norway and the Tomakomai project in Japan, exploring key issues related to the application, geological characteristics, injection strategies, monitoring systems, and simulation methods of CO₂ storage in offshore saline aquifers. This study finds that CO₂ storage in offshore saline aquifers has high safety and storage potential but faces several challenges in practical applications, such as geological reservoir characteristics, technological innovation, operational costs, and social acceptance. Therefore, it is necessary to further strengthen technological innovation and policy support to promote the development and application of CO₂ storage in offshore saline aquifers. This study provides valuable experiences and insights for similar projects worldwide, contributing to the sustainable development of CO₂ storage in offshore saline aquifers and making a greater contribution to achieving global net-zero emission targets.