Abstract The large-scale deployment of CO2 geological storage imposes stringent requirements on injectivity, subsurface space utilization, and long-term safety, making reservoir-scale heterogeneity a critical constraint on engineering feasibility and storage reliability. However, existing studies have primarily focused on individual heterogeneity elements, localized storage processes, or specific spatial scales, while systematic understanding of the coupling among multiple structural types, cross-scale transfer, and their impacts throughout the storage lifecycle remains limited. Therefore, this study synthesizes experimental, modeling, field, and ML studies, distinguishing their evidence sources and validation limits, to summarize the origins, types, characterization methods, and quantitative indicators of heterogeneity and to compare approaches for geological modeling, probabilistic prediction, and engineering regulation. The reviewed literature indicates the influence of geological architecture and connectivity on preferential migration and plume distribution. Quantitative effects on pressure, capacity, and trapping remain dependent on site conditions and model assumptions. Based on the identified limitations, recommendations are proposed in eight areas: evaluation standards, multisource data integration, structural fidelity, scale correction, probabilistic prediction, dynamic updating, zonal injection, and intelligent regulation. These recommendations are aligned with the major challenges identified in this review, covering standardized evaluation, structural representation, uncertainty-aware prediction, adaptive management, and engineering regulation throughout the storage lifecycle. This study reveals the differentiated roles and dual effects of heterogeneous structures and provides a basis for reservoir screening, capacity and risk assessment, injection optimization, and long-term management.
Abstract Coal/NH3 co-firing is one of the feasible technological pathways for the low-carbon transition of coal-fired plants, and reducing NOx emissions is key to promoting its application due to the extremely high nitrogen content in NH3 fuel. During co-firing, the gas-phase interaction between coal volatiles and NH3, which mainly involves the C–N cross-reactions between N-containing intermediates and hydrocarbon components, critically regulates NO formation and is strongly dependent on the local oxygen environment. The low-O2 dilution environment achieved in MILD (moderate or intense low-oxygen dilution) combustion favors this interaction and enhances its inhibitory effect on NO formation. However, the underlying mechanism of this influence remains unclear. This study combines experiments with chemical kinetics to elucidate how C–N cross-reactions suppress NO under low-oxygen dilution, in terms of free radical regulation, key reaction enhancement, and dominant pathway competition. Results indicate that C–N cross-reactions significantly inhibit the formation of the free radical pool, and their inhibitory effect is enhanced as the NH3 blending ratio increases. Besides, C–N cross-reactions inhibit the conversion of NH2 → HNO and NH → NO by weakening R95 (NH2 + O = HNO + H) and R112 (NH + O = NO + H), while promoting the conversions of NO → N2 and NNH → N2 by enhancing reactions R107 (NH2 + NO = N2 + H2O) and R121 (NNH = N2 + H). Furthermore, a two-step ROP analysis method was further developed to quantify the probability of occurrence for different fuel-N conversion pathways at the moment of maximum NO production rate, thereby evaluating changes in the contribution of main pathways to NO formation. The removal of C–N cross-reactions increases the probabilities of path a (NH3 → NH2 → HNO → NO) and path c (NH3 → NH2 → NH → NO) from 24.2 and 7.2% to 38.4 and 18.0%, respectively. The decoupling of C–N cross-reactions indicates that NH2 hydrogen abstraction (G1 subset) and N2Hx/CH3 interaction (G5 subset) play a key role in inhibiting NO formation.
Abstract Phase behavior of hydrocarbons in nanosized porous media is important for understanding fluid behavior in confined environments, yet direct experimental validation under elevated-pressure conditions remains limited. In this work, elevated-pressure differential scanning calorimetry (DSC) was used to measure boiling points of n-heptane and toluene confined in well-defined mesoporous silica materials (SBA-15 and SBA-16) at pressures up to 1300 kPa. The experimentally derived vapor pressure curves show a systematic suppression relative to bulk fluids across all pressures. Kelvin equation predictions and Gibbs Ensemble Monte Carlo (GEMC) simulations provide thermodynamic and qualitative molecular-level support for the observed confinement-induced phase behavior. In contrast, shale samples with low pore volumes and broader, more heterogeneous pore structures did not show a distinct confinement peak under the present experimental conditions. These findings provide elevated-pressure experimental data for confinement-induced phase behavior in well-defined mesoporous model systems and offer a benchmark for comparison with thermodynamic models and molecular simulations.
Abstract Thermal runaway (TR) can be triggered in lithium-ion batteries under abuse conditions, leading to significant safety concerns for electric vehicles and energy storage systems. Emergency discharge has been considered as an effective strategy to mitigate TR by reducing the state of charge (SOC), whereas substantial ambiguities remain due to the wide discharge range beyond normal operation and the complex coupling between electrochemistry and TR. In this work, TR experiments are conducted in an Accelerating Rate Calorimeter (ARC) for commercial 18650 LiFePO4 cells, in a range of high discharge temperatures beyond exothermicity (90–110 °C) and discharge C-rates (0.05–18.75 C). Based on the experimental data, a regime diagram is established to isolate TR and No-TR regimes. As discharge temperature increases, the No-TR regime progressively narrows, indicating increasing TR risk. Meanwhile, for a given discharge temperature, increasing discharge C-rate leads to a nonmonotonic system response for TR occurrence, with TR occurrence in the low and high end of discharge rates, yet no-TR in between. Furthermore, the remaining SOC after discharge is nonmonotonic as discharge rate increases, with intermediate C rates achieving the lowest remaining SOC. Based on energy analysis, cells with similar remaining SOC exhibit nearly identical global kinetics regardless of discharge conditions. Statistical analysis reveals that the voltage-drop temperature collected from all the TR tests follows an approximately normal distribution, providing a risk-driven criterion for defining acceptable discharge windows. Measurement using a Simultaneous Thermal Analyzer (STA) has further demonstrated high consistency between the thermal stability of separator meltdown and the voltage drop temperature. These findings not only establish the regime diagram for TR under discharge, but also provide practical guidance for developing effective emergency discharge strategies for TR mitigation.
Abstract The U.S. biofuels sector is increasingly central to national energy security, both by diversifying the liquid fuel supply and by adding new energy sources. Yet growth remains rapid but uneven, driven by a complex mix of policies, constrained feedstock markets, and emerging conversion technologies. To provide a clearer basis for tracking biofuel growth and identifying practical opportunities for improvement and expansion, this study develops an integrated framework that links facility-level biofuel production data with feedstock use, conversion pathways, regulatory frameworks, and regional expansion analyses. Together with input from industry stakeholders, we compiled a comprehensive facility-level database for biodiesel, renewable diesel, ethanol, sustainable aviation fuel, and renewable natural gas by synthesizing industry and government data. We then evaluated the value of national and state incentive programs by pathway and feedstock and developed an Expansion Opportunity Index to identify promising regions for future growth based on four dimensions: resource headroom, infrastructure readiness, policy strength, and supply chain maturity. Results show that first-generation and waste-based feedstocks dominate current and announced biofuel production, while cellulosic biomass remains substantially underutilized despite its large technical potential. Stakeholder input identifies limited commercialization pathways, underdeveloped supply chains, financing risk, and cost competitiveness as major barriers to cellulosic biofuel scale-up. Results further show that existing incentive structures can improve the economic attractiveness of several biofuel pathways, particularly those based on cellulosic feedstocks. Overall, the results identify region-specific opportunities where scaling cellulosic biofuel pathways could expand domestic fuel supply while highlighting the practical constraints that must be addressed for broader industry growth.
