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Detecting hydrogen leaks remains a pivotal challenge demanding robust solutions. Among diverse detection techniques, the fiber-optic method distinguishes itself through unique benefits, such as its distributed measurement properties. The adoption of hydrogen-sensitive materials coated on fibers has gained significant traction in research circles, credited to its operational simplicity and exceptional adaptability across varied conditions. This manuscript offers an exhaustive investigation into hydrogen-sensitive materials and their incorporation into fiber-optic hydrogen sensors. The research profoundly analyzes the sensor architectures, performance indicators, and the spectrum of sensing materials. A detailed understanding of these sensors' potentials and constraints emerges through rigorous examination, juxtaposition, and holistic discourse. Furthermore, this analysis judiciously assesses the inherent challenges tied to these systems, simultaneously highlighting potential pathways for future innovation. By spotlighting the hurdles and opportunities, this paper furnishes a view on hydrogen sensing technology, particularly related to optical fiber-based applications. [ABSTRACT FROM AUTHOR]

• A normal behavior model of slurry circulating pump is established. • K-means algorithm is used to realize the operational condition recognition. • Memory matrix adaptive to varying operating condition are constructed. • The condition monitoring method can realize the early fault warning of the slurry circulating pump. The slurry circulating pump, a crucial component of wet flue gas desulfurization (WFGD) systems, often encounters faults such as impeller and bearing box damage due to limestone slurry's intense abrasion, corrosion, and cavitation. The various operating conditions, including frequent switching and rapid frequency variations of the slurry circulating pump will make the working environment worse undoubtedly. To ensure the process safety and operation efficiency of the WFGD system, this study proposed a condition monitoring (CM) method based on a novel multivariate state estimation technique (MSET), which can realize the fault early warning of the slurry circulating pump. To improve the accuracy of the conventional MSET, a memory matrix (MM) construction method based on K-means algorithm is proposed, which can provide a MM that varies with the operating condition of real-time observed vectors. In typical cases of predicting the pump's B-phase current under normal conditions, the root mean square error (RMSE) of our method is 0.25 A, much smaller than that of the conventional MSET method (2.08 A). On the other hand, the computation time of our method remains short (about 20 s) compared to other models (e.g., MEST aided with K-nearest neighbour model needs about 19,000 s) adaptive to varying conditions for over 3000 samples. Also, the proposed CM method can effectively provide early fault warning for impeller damage and bearing box damage of the slurry circulating pump, with 8 days and 1 day in advance, respectively. This can win enough time to inspection & maintenance before troubleshooting. [ABSTRACT FROM AUTHOR]

Equilibrium capacity expansion is an effective tool to help regulators predict the generation evolution of power systems by analyzing the decision-making of generation companies (Gencos). With the development of carbon markets (CMs) and electricity markets (EMs), Gencos' decisions in these two markets (encompassing investment and bidding decisions related to carbon emission allowances and electricity) are deeply intertwined through market clearing results. However, existing studies mainly focus on equilibrium capacity expansion with fixed carbon prices and usually ignore the realistic clearing process of CMs, which cannot simulate Gencos' coupled decision-making and accurately predict generation evolution under the CMs and EMs. This paper proposes a two-level equilibrium capacity expansion model for power systems which considers the coupled decisions of Gencos between CMs and EMs. At the upper level, multiple Gencos' coupled decision models are proposed based on their interaction with market clearing results. At the lower levels, CMs and EMs are respectively cleared to determine the varying carbon and electricity prices. Furthermore, the developed equilibrium capacity expansion model is reformulated as an equilibrium problem with equilibrium constraints (EPEC), which is solved by a diagonalization-based solution procedure. Finally, a provincial power system of southeast China is used to validate the performance of the proposed framework. The results illustrate that under CMs and EMs, non-fossil energy would account for 81.3% of total capacity and 73.88% of total generation in 2050. Compared to the existing model using fixed carbon prices, the consideration of realistic carbon market clearing will promote the installation of renewable energies and improve social welfare. The proposed model can provide beneficial references for regulators to perceive the evolution of power systems in CMs and EMs. • A two-level equilibrium capacity expansion model for power systems is proposed. • A novel coupled decision model for Gencos in CMs and EMs is developed. • The proposed model is solved by a diagonalization based solution procedure. • The results can guide the transition of power systems under the CMs and EMs. [ABSTRACT FROM AUTHOR]

Developing efficient water splitting electrocatalysts plays a critical role in lowering the energy cost for hydrogen production, which requires accurate evaluation of the catalytic performance especially under industrially relevant conditions. In this work, we design a two-chamber electrolyzer testing system simulating practical water electrolyzer system to enable catalytic performance evaluation under industrially relevant conditions. A one-step electrodeposition method is used to synthesize binary and ternary Ni alloy HER catalysts and the catalytic electrodes are screened and optimized with the two-chamber electrolyzer testing system. A voltage of 1.64 V without iR compensation at a current density of 200 mA/cm2 is obtained with continuous operation for 70 h. Different HER activity trend is observed from conventional three-electrode experiments with low-concentration alkaline electrolytes at room temperature and the two-chamber electrolyzer measurements, further supporting the importance of catalytic performance evaluation under industrially relevant conditions. The electrodeposition synthesis method is further used to prepare large-area catalytic electrodes over 400 cm2 with good uniformity. • Ni-alloy HER catalysts are characterized under industrially relevant conditions with a home-build electrolyzer system. • Electrolyzer with an electrodeposited NiMo HER catalyst exhibits a remarkably low voltage of 1.64 V at 200 mA/cm2. • Different activity trends of HER catalysts are observed under industrially relevant conditions and three-electrode tests. • Ni-alloy catalysts with an active area over 400 cm2 are successfully synthesized with excellent performance uniformity. [ABSTRACT FROM AUTHOR]

• The SO 2 absorption into a droplet falling freely is investigated numerically. • The deformation and internal circulation occur during droplet falling and facilitate the mass transfer of gas-droplet. • A modified mass transfer coefficient of gas phase is proposed. The SO 2 absorption into a droplet falling freely is investigated numerically based on a detailed three-dimensional mode in this work. Gas-liquid multiphase flow simulations coupled with interphase mass transfer are performed using the coupled Level-set and Volume of Fluid method (CLSVOF) to trace the gas-droplet interface. The results of simulation reveal that droplet would deform and deviate from the standard sphere during falling, with an approximately 5.6 % increase in surface area under the discussed working conditions. The evolution mechanism of the internal circulation in the droplet is clarified: the increase in the relative velocity of gas-droplet facilitates the formation and intensification of the internal circulation in the droplet. As the internal circulation develops into the stable stage, the convective mass transport would dominate the mass transfer process and promote the mass transfer. The distribution laws of the local mass transfer rate and coefficient over the droplet surface are found analogous to the typical case of heat transfer around a sphere. Finally, considering the effects of both droplet deformation and internal circulation on mass transfer concurrently, the variation of Sh as a function of Reynolds number is obtained, which appears the same trend but yields slightly higher values compared to the results of empirical correlations. [Display omitted] [ABSTRACT FROM AUTHOR]