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Underground gas storage (UGS) is efficient in large-scale natural gas storage and peak regulation. However, UGS operation based on gas-condensate reservoirs are challenging due to complicated phase behavior and multi-phase flow considering trapped condensate. This paper presents a method for full-cycle enhancing condensate oil recovery (EOR)-UGS by integrating cyclic gas flooding and storage from gas-condensate reservoirs. Full-cycle EOR-UGS is defined by four stages, including primary depletion, cyclic gas flooding, collaborative gas production and UGS operation. The EOR mechanisms of each stage are analyzed by experiments and simulation. Cyclic gas flooding can reduce drop out of condensate. The reasonable volume of cyclic gas flooding is 0.5 HCPV, enhancing condensate recovery factor by 42.8%. During the collaborative stage, gas injection can effectively evaporate and drive the condensate towards production wells. After five collaborative cycles, the condensate recovery factor is further enhanced by 21.8% and gas storage capacity can be increased more than 30%. Finally, optimal full-cycle EOR-UGS schemes can enhance condensate recovery factor by 69.92%. Compared with gas flooding to 1.5 HCPV followed by constructing UGS, the full-cycle EOR-UGS integration can improve condensate recovery factor by 7.37%. This work provides a new idea for UGS construction and operation based on gas-condensate reservoirs. • A method of Full-cycle EOR-UGS by integrating cyclic gas flooding and storage is established. • Experiments are conducted to estimate the conversion time at different stages of Full-cycle EOR-UGS integration. • The EOR mechanisms and phase behavior of Full-cycle EOR-UGS is analyzed. • Optimal schemes can enhance condensate recovery by 68.7% and improve gas storage capacity by more than 30%. [ABSTRACT FROM AUTHOR]

The applicability of packed bed latent thermal energy storage devices is restricted by the limited thermal conductivity of phase change materials (PCMs). As a cheap and simple heat transfer-enhanced construction, the hollow channel allows the heat transfer fluid to go through the capsule center directly where the melting rate of PCM would be enhanced. In this study, an experiment was conducted to explore the promotion effect of hollow channels. The influence of the hollow channels on the charging duration and outlet temperature characteristics at different inlet flow rates, inlet temperatures, and placement angles was investigated. The results showed that the charging rate was improved with a reduction in charging duration of about 16.6%. The improvement was consistent in scenarios with variable inlet temperatures and flow rates, with a difference of less than 1%. Furthermore, adding hollow channels resulted in a lower average outlet temperature. Finally, there is no significant influence of horizontal and vertical placements of the hollow channels on the performance of PBLTES. Therefore, random angle placement is advised to reduce costs in engineering. However, the addition of hollow channels drops the PCM filling rate by 3.7%, reducing latent thermal energy storage but increasing sensible thermal energy storage. • The PBLTES employing capsules with simple and low-cost hollow channels is studied. • The hollow channel can decrease the charging completion time and outlet temperature. • The effect of inlet temperature, inlet flow rate and angle are investigated experimentally. • The flow field distribution in PBLTES may affect the effectiveness of the hollow channel. [ABSTRACT FROM AUTHOR]

Oil and gold are considered as the most vigor influencer for any economy. In this research volatility spillover networking among the oil (energy), gold, and Asian leading emerging stock markets are constructed by the coalescence of two approaches BEKK-GARCH and complex networking. The data consists of the daily return of sixteen Asian countries' stock markets, an index of the Asia Pacific, and future prices of oil and gold contracts for the period of 01–01-2010 to 31-05-2020. It covers all the recent shocks of the current decade to study the impact of these crises. The data is further divided into four sub-periods as well for this research. The results of our total period detect that commodities of oil and gold receive more volatility spillover than transfer it to stock indices of Asia Pacific countries. Moreover, it is also observed that, as compared to oil, gold had more strong significant spillover linkages. Among all Asian economies, the Chinese stock markets had more influence on the price movement of oil and gold. Whereas, India had more significant correlations with other neighboring stock indices. The results of this research not only provide the facts about the interconnection of oil, gold, and Asian Pacific countries in the current scenarios but also give very useful directions for future researchers, investors, and hedgers, as well as for policymakers interested in the Asian region. • highlights spillover networking among oil, gold, and Asian stock markets. • applies the coalescence of two approaches BEKK-GARCH and complex networking. • employs the daily returns of sixteen stock markets and future prices. • shows the oil and gold receive more volatility spillover than transfer to stock. • illustrates that compared to oil, gold had more strong spillover linkages. [ABSTRACT FROM AUTHOR]

LiFePO 4 batteries are widely used in electric vehicles (EVs) and battery energy storage systems (BESSs). However, the consistencies in capacity, internal resistance, and open circuit voltage (OCV) limit the battery pack performance, which makes it difficult to evaluate the state information of the cells effectively without disassembling the pack. Therefore, this paper proposes a battery capacity and initial discharge electric quantity (DEQ) estimation method for series-connected battery packs based on partial reconstruction of the OCV curve. The aging characteristics of each cell are extracted based on incremental capacity analysis (ICA), which is taken as the transformation law for the OCV curve considering aging. And then the multipopulation genetic algorithm (MPGA) is utilized to optimize the transformation coefficients and obtain the reconstructed OCV curve of each cell in the pack. Finally, the actual capacity and initial DEQ of batteries at a low current rate are estimated according to the reconstructed complete OCV curve and optimized OCV curve transformation coefficients. The experimental results show that the estimation error of capacity is less than 5%, and the maximum estimation error of the initial DEQ is 5.56%. • An open circuit voltage reconstruction method is proposed. • The feature points in incremental capacity curve is utilized for reconstruction. • The multipopulation genetic algorithm is utilized for curve optimization. • The capacity of batteries in series-connected pack can be estimated. • The initial discharge electric quantity of batteries in pack can be estimated. [ABSTRACT FROM AUTHOR]

Adaptability evaluation of reservoirs needs to be performed before natural gas flooding. However, the current evaluation methods consider the reservoir pressure and minimum miscible pressure (MMP) as separate parameters to evaluate the miscibility, which ignores the correlation between reservoir pressure and MMP. Also, the effect of reservoir pressure on injectivity is also neglected, while higher pressure than MMP may not improve the miscibility but increase the difficulty of gas injection. Furthermore, evaluation range of each index is inconsistent. Therefore, this paper proposes an improved evaluation system by introducing the miscible ability and optimizing the evaluation criteria to better evaluate the adaptability of natural gas flooding in enhancing oil recovery. The miscible ability is newly defined to evaluate the impact of reservoir pressure on miscibility, and multi-level evaluation model is further developed which includes 12 indexes based on reservoir/fluid/rock properties. The evaluation criteria are established by optimizing parameter intervals. The adaptability of BQ Oil field is assessed using Analytic Hierarchy Process (AHP) and fuzzy evaluation. Field application validates the reliability of the proposed evaluation system. It can be used to quickly evaluate the adaptability of natural gas flooding, which could improve success rate of natural gas flooding and reduce the costs. • An improved system for adaptability evaluation of natural gas flooding is proposed. • Miscible ability is defined to evaluate the impact of pressure on miscibility. • Multi-level evaluation model composed of 12 indexes is developed. • Improved evaluation system can identify reservoirs suitable for natural gas flooding. [ABSTRACT FROM AUTHOR]

This paper investigates the multidimensional risk spillovers among crude oil, the US and Chinese stock markets during the COVID-19 epidemic through a GARCHSK-Mixed Copula-CoVaR-Network method. Firstly, we find that during the COVID-19 period, the oil-stock risk spillovers are obviously stronger than those during the normal period. And there are significant risk spillovers from the US and Chinese stock markets to the oil markets. It is also discovered that the oil markets are greatly influenced by the second board stock markets, also known as the growth enterprise markets, especially during the COVID-19 outbreak. Furthermore, the bidirectional China-oil risk spillovers during the COVID-19 pandemic have rapidly increased. Besides, it is reported that the relationships across oil futures, main board and second board stock markets in the US and China are stable under different TSI levels and extreme events. Finally, the GARCHSK-Mixed Copula-CoVaR-Network outperforms the control groups in terms of marginal distribution and dependence structure. Our study not only offers new method and insight into the oil-stock relationship, but also has economic implications for investors and policymakers. • The multidimensional oil-stock risk spillovers during the COVID-19 pandemic are investigated. • There are significant risk spillovers from the stock markets to the oil markets. • Oil markets receive high risk spillovers from second board markets. • The bidirectional risk spillovers between Chinese stocks and oil have rapidly increased. • The relationships across oil and stocks are stable under most situations. [ABSTRACT FROM AUTHOR]

Underground gas storage (UGS) plays an important role in large-scale energy (natural gas) storage, while salt deposition may affect the storage and production capacity of UGS. However, salt precipitation mechanism of UGS under movable water conditions is not clear. This work aims at understanding salt precipitation on rock properties of an UGS in porous media under movable water conditions. Firstly, core flooding experiments are performed to establish the relationship between dynamic petrophysical properties and the amount of salt crystals. The dynamic process of salt precipitation at the pore-scale is further captured by microscopic visualization experiments, and the location and morphology of salt crystals at micro-scale are also observed using scan electron microscope (SEM). Results indicate that formation-water evaporation and salt precipitation improve the formation properties when the amount of deposited salt is less than 39 mg/g. After the amount of deposited salt is more than 48 mg/g, formation porosity and permeability can be reduced. The size of salt crystals under movable water (>40 μm) is much larger than that under irreducible water conditions (1 μm–5 μm). This work offers a methodology for analyzing the effect of salt precipitation on the UGS in porous media under movable water conditions. • Salt precipitation in porous media under movable water conditions are investigated in the UGS. • Macro/micro experiments are performed to simulate multi-cycle gas injection and production of the UGS. • Relationship between dynamic formation properties and the amount of salt crystals is determined. • The location and morphology of salt crystals at micro-scale are analyzed. [ABSTRACT FROM AUTHOR]

A bubble-derived concept for contour regeneration of flow channel is developed to address the issues of carbon dioxide (CO 2) management and reactant homogeneity in a direct methanol fuel cell (DMFC). The bubble contour is extracted from the visualization experiment based on the conventional sinusoidal flow channel (SFCH), which is used as a model to design and fabricate the bubble-derived flow channel (BDFCH). The simulation results indicate that this renewed channel shows a lower momentum loss and uniform reactant distribution. Because of the optimized amplitude (A) and period (W) of BDFCH, the regenerated flow channel displays superior cell performances under various testing conditions. The cell based on the renewed design produces a peak power density of 37.07 mW cm−2 at a flow rate of 1 mL min−1 and a methanol concentration of 6 M. The maximum performance improvement of the BDFCH is 30.8% higher than the SFCH with the combination of A = 0.15 and W = 5. The BDFCH based on the SFCH (A = 0.1 and W = 5) shows a higher cell performance than the SFCH at 6 M, demonstrating the scalability of BDFCHs. This new concept for precision design and construction of flow channels provides an efficient solution for practical flow field optimization of fuel cells. • A bubble-derived concept for contour regeneration of flow channel is developed. • Two-phase flow mechanism of CO 2 bubbles in the flow channel is revealed. • The effects of BDFCH for CO 2 bubble management and reactant homogeneity in DMFC are analyzed. • A DMFC based on an optimized BDFCH with excellent electrochemical performance is provided. [ABSTRACT FROM AUTHOR]