Search Results (9,671)

In today’s energy landscape, defined by the growing demand for sustainable energy generation technologies and the parallel need to advance internal combustion engine (ICE) architectures toward cleaner and more efficient solutions, the adoption of Free-Piston Linear Generator (FPLG) engines emerges as a highly promising approach. This innovative system enables the direct conversion of combustion-induced piston motion into electrical energy, eliminating the need for traditional crankshaft and connecting rod mechanisms. The FPLG concept facilitates efficient utilization of a broad spectrum of fuels—including methane, ethanol, LPG, gasoline, biodiesel, and hydrogen—by supporting variable compression ratio operation. This feature enhances operational flexibility and fuel adaptability, positioning the technology as a viable candidate for future energy transition scenarios. The absence of rotating mechanical components significantly reduces frictional losses, contributing to an overall increase in system efficiency. To accurately characterize and optimize engine performance, an extensive series of one-dimensional (1D) numerical simulations was performed under both free and controlled operating conditions. The resulting data enabled the development of semi-empirical models capable of predicting the dynamic behavior of the engine across a wide range of working scenarios. Finally, through a detailed parametric analysis, the optimal operating conditions were identified to maximize both net electric efficiency and electrical power output. These findings provide a solid ground for the design and implementation of FPLG engine systems in advanced power generation applications. Full article

The significant heat generated during the refueling of hydrogen pressure tanks may exceed the permissible 85 °C temperature limit for type IV tanks. Common countermeasures such as hydrogen pre-cooling or long filling times are energy- and time-consuming; hence, in this paper, passive means through thermally better-suited materials are examined. State-of-the-art and alternative materials are first characterized and finally compared using a transient heat model. Different material combinations are compared in terms of the maximum temperature and weight in a typical filling scenario. As alternative liner materials, thermoplastics filled with short carbon fibers, minerals, and graphite were selected to improve thermal properties. For the composite overwrap, copper-coated carbon fibers were chosen. The findings show that the liner is the bottleneck while transferring heat from the inner to the outer tank surface. Using graphite-filled thermoplastics as the liner material shows the greatest potential regarding thermal optimization with only a slight weight increase. Using copper-coated carbon fibers additionally further reduces the maximum temperature but results in a significant weight increase. Full article

Hydrogen refueling stations (HRSs) are a critical enabling infrastructure for fuel cell electric vehicles (FCEVs), yet their deployment in dense metropolitan areas often faces a dual challenge: limited travel-time accessibility for users and low public acceptance driven by perceived safety risks. This study develops an integrated, city-scale framework to quantify HRS accessibility and resident acceptance and to identify expansion priorities for Seoul, South Korea. We combine (i) an online perception survey of 1000 adult residents (October 2024) capturing environmental awareness, perceived safety, siting preferences, and willingness-to-travel distance; (ii) spatial demand data on FCEV registrations by administrative dong (n = 2443 vehicles, 2022); and (iii) network-based travel-time analysis using the Seoul road network and the current HRS supply (n = 10, 2024). Accessibility is evaluated under three travel-time thresholds (10, 15, and 20 min), with service-area delineation and demand-weighted underserved-area diagnosis. Candidate expansion sites are generated and screened using operational and regulatory constraints (e.g., site area and proximity to protected facilities), followed by a p-median location-allocation optimization to select five additional sites that minimize demand-weighted travel impedance. Results indicate that, under the 20 min threshold (7.7 km at an average operating speed of 23.1 km/h), 50 of 425 dongs (11.8%) and 244 of 2443 FCEVs (10.0%) are outside the baseline service coverage. After adding five sites (total n = 15), underserved dongs decrease to 5 (1.2%) and underserved FCEVs to 26 (1.1%) for the 20 min threshold, with consistent improvements across shorter thresholds. Survey responses further reveal that only 12.5% of respondents perceive HRSs as safe, while 46.5% report a maximum willingness-to-travel distance of up to 5 km, underscoring the need for both accessibility enhancement and risk-aware communication. The proposed workflow offers a transparent, reproducible approach to support equitable and risk-informed HRS planning by jointly considering network accessibility, demand distribution, and social acceptance, thereby contributing to sustainable urban mobility, low-carbon transport transition, and socially acceptable hydrogen infrastructure deployment. Beyond local accessibility improvement, the study is framed in the broader context of sustainability, as equitable and socially acceptable hydrogen refueling infrastructure can support low-carbon urban transport transitions and more resilient metropolitan energy-mobility systems. Full article

Chronic kidney disease (CKD) is a progressive global health challenge. While empagliflozin, a selective SGLT2 inhibitor, is known to attenuate CKD progression through mechanisms beyond glycemic control, the precise molecular pathways remain incompletely characterized and warrant further investigation. This study employed an integrated network pharmacology and molecular docking approach to elucidate the multi-target mechanisms of empagliflozin in CKD. Initial evaluation demonstrated that empagliflozin exhibits favorable physicochemical properties, drug-likeness, and ADMET profiles, supporting its potential as an effective orally administered therapeutic option for CKD management. Network analysis identified 221 shared molecular targets between empagliflozin and CKD-associated genes. Topological analysis of the protein–protein interaction (PPI) network revealed ten critical hub proteins—GAPDH, IL6, EGFR, HSP90AA1, NFKB1, HSP90AB1, MTOR, MAPK3, IL2, and PIK3CA—which serve as key regulators in CKD pathophysiology. Gene Ontology and KEGG pathway enrichment analyses indicated that these shared targets are significantly involved in phosphorylation, signal transduction, and central signaling cascades associated with CKD progression, including the PI3K-Akt, FoxO, HIF-1, and AGE-RAGE pathways. Molecular docking simulations corroborated empagliflozin’s multi-target affinity, demonstrating particularly strong binding energies toward HSP90AB1 (−10.85 kcal/mol), MAPK3 (−9.46 kcal/mol), and EGFR (−9.38 kcal/mol). Empagliflozin maintained stable hydrogen bonding throughout the 200-ns molecular dynamics simulation, primarily with GLN18, GLU42, SER45, ASN46, ASN101, GLY130, and TYR134, underscoring its persistent and well-anchored interaction with HSP90AB1. Collectively, these findings provide crucial mechanistic insights, suggesting that empagliflozin might exerts therapeutic effects by modulating interconnected pathways regulating inflammation, oxidative stress, and metabolic homeostasis, thereby reinforcing its role as a comprehensive, multi-target therapeutic strategy for CKD management. Nonetheless, validation through in vitro experiments remains necessary. Full article

Hydrogen is a key energy carrier for the transition to renewable energy, but its storage remains a major challenge, mainly due to the energy requirements for its production and to its low volumetric energy density under ambient conditions. Clathrate hydrates have recently emerged as a promising medium for gas storage, yet their potential for hydrogen storage is still underexplored. This study presents a comprehensive bibliometric analysis of hydrogen storage research, focusing on clathrate hydrates. The analysis, based on publications indexed in Scopus over the past decades, reveals that research on gas hydrates is mature and interdisciplinary, encompassing hydrate formation, thermodynamics, and production from natural reservoirs. In contrast, hydrogen hydrates remain a marginal and emerging research area, characterized by limited scientific output and weak connections to dominant storage strategies such as metal hydrides, metal–organic frameworks, and adsorptive materials. The results highlight key research gaps, including a limited understanding of formation kinetics, thermodynamic stability under practical conditions, and challenges related to scalability and system integration. These findings suggest that targeted research efforts addressing these bottlenecks could support the development of hydrate-based systems as complementary solutions within the broader hydrogen storage landscape. Full article

Per- and polyfluoroalkyl substances (PFAS) have found wide application in proton exchange membrane fuel cells (PEMFCs) and water electrolysers (PEMELs), thanks to their exceptional chemical and thermal stability. However, their environmental persistence and growing regulatory pressure—particularly from the European Union—have made the transition to PFAS-free components a priority. This work reviews current advancements in alternative materials that can guarantee the same performance or maybe improve it. Although several non-fluorinated materials have demonstrated initial performance close to PFAS-based benchmarks, significant challenges remain. These include limited long-term stability, difficulties for new materials to fit into existing stack architectures, and the lack of standardized testing protocols. Nevertheless, recent efforts have successfully demonstrated a PFAS-free PEM electrolyser stack at TRL 4, validating the technical feasibility of full PFAS substitution. Achieving commercial readiness will require parallel progress in materials development and industrial scalability. This review highlights the possibility that hydrogen technologies, such as fuel cells and electrolysers, which are called upon to support the energy transition towards a more sustainable future, are themselves truly environmentally friendly, thus making their use as green as possible. Full article

This study addresses the optimal scheduling of a proton exchange membrane fuel cell (PEMFC)-based building combined cooling, heating, and power (CCHP) system, aiming to improve operational efficiency and flexibility under coupled electricity–thermal–cooling demands and load uncertainty. A physics-informed scheduling environment was developed using component models and multi-energy balance constraints, including a PEMFC with waste-heat recovery, a lithium bromide absorption chiller, a reversible heat pump with condenser heat recovery to thermal storage, a battery energy storage system, and a hot-water thermal storage tank. The dispatch problem was formulated as a Markov decision process and solved using deep reinforcement learning with TD3; performance was evaluated on typical summer and winter days, and robustness was tested by generating 100 scenarios with 30% demand perturbations. The results show that TD3 learns coordinated multi-energy dispatch patterns consistent with seasonal operation and reduces hydrogen consumption relative to a rule-based strategy under uncertainty while requiring millisecond-level inference time. Dynamic programming achieved slightly lower hydrogen consumption but incurred orders-of-magnitude higher computation time. Overall, TD3 provides a practical trade-off between near-optimal performance, robustness, and real-time applicability for PEMFC-based building CCHP scheduling. Full article

Stationary energy storage (SES) is increasingly needed to integrate variable renewable generation and improve consumer self-consumption, but technology choices involve associated trade-offs between cost, efficiency, and life-cycle impacts. This study evaluates the role of second-life lithium-ion (Li-ion) batteries repurposed from electric vehicles for stationary applications, compared to lead-acid (Pb-acid) batteries and power-to-hydrogen-to-power (PtH₂P) systems. We develop an optimization-based sizing and dispatch framework using measured PV–load profiles and hourly market electricity prices, and evaluate performance per 1 MWh delivered to the load over a 10-year life cycle. Economic performance is quantified through discounted cash flows equal to levelized cost of storage (LCOS), while environmental performance is assessed through life-cycle metrics with explicit representation of recycling and second-life credits. In addition to global warming potential (GWP), the analysis considers additional resource and impact metrics, as well as key operational efficiency metrics, including bidirectional consumption efficiency, autonomy, and share of self-consumption/export of photovoltaic systems. Scenario and sensitivity analyses examine the impact of policy and financial parameters, in particular feed-in tariff remuneration and discount rate, on the comparative ranking of technologies. The results highlight how circular economy pathways, especially second-life distribution for Li-ion batteries and high end-of-life recovery for lead-acid batteries, have a significant impact on the life-cycle burden for delivered energy, while market-driven conditions for dispatching and export activities shape economic outcomes. Overall, the proposed workflow provides a transparent, circularity-aware basis for selecting stationary storage technologies associated with photovoltaic systems, under realistic operational constraints. Full article

We report a curious numerical observation: If atomic nuclei are modelled as connect-sums of threefoil knots with alternating chirality, the ropelength of the composite knot—a purely geometric quantity requiring no quantum mechanics—tracks the experimental binding-energy curve from hydrogen to uranium. A two-parameter fit to 50 nuclei gives $R^2=0.9998$ (coefficient of determination; 1 = perfect fit) and $\mathrm{RMS}=6.9\mathrm{MeV}$ (root-mean-square deviation between model and experiment), comparable to the five-parameter Bethe–Weizsäcker formula ($\mathrm{RMS}=8.3\mathrm{MeV}$) at less than half the parameter count. Out-of-sample predictions for ${}^{244}\mathrm{Pu}$ and ${}^{252}\mathrm{Cf}$, not used in the fit, are accurate to $0.4\mathrm{MeV}$ and $8.4\mathrm{MeV}$, respectively. What makes the observation worth reporting is not the fit itself, but the range of nuclear phenomenology that emerges uninstructed from the topology: saturation, surface energy, isospin pairing, odd-even staggering, and geometric analogues of nuclear isomers all appear as consequences of the connect-sum construction, without additional assumptions. We catalogue these correspondences, assess which are structural and which may be coincidental, and identify concrete numerical tests that would distinguish the two possibilities. Full article

The hydrogen fuel cell electric vehicles (FCEVs) are becoming a worldwide recognized eco-friendly choice which produces no tailpipe emissions while providing better energy efficiency than traditional internal combustion engine vehicles. The review delivers an in-depth evaluation of FCEVs through their assessment which focuses on their transportation and power generation functions. The research investigates hydrogen production methods together with storage and distribution systems and vehicle integration practices and performance enhancement techniques. The paper highlights major technical challenges such as high production costs, limited refueling infrastructure, storage inefficiencies, and fuel cell durability. The research uses battery electric and hybrid vehicle comparisons to assess FCEV market competitiveness. The life-cycle environmental impact assessment proves that using clean hydrogen sources and sustainable end-of-life strategies is essential for achieving FCEV operational capabilities. The review examines new electrochemistry materials science and hybridization solutions which have become essential methods for creating better efficiency and durability while decreasing costs. The study shows how policy regulations and collaborative programs fast-track hydrogen adoption through their impact on future hydrogen grid integration and renewable hydrogen production and circular economy methods. The review shows how experts from different fields reached their achievements while still facing challenges to improve FCEVs as fundamental components of environmentally friendly transportation systems and clean energy networks. Full article

The use of renewable energy sources instead of conventional ones, together with the development of efficient electricity storage solutions, represents a central objective of the transition to sustainable and resilient energy systems. In this context, two main development directions are the integration of hydrogen in the energy chain (Power-to-Gas) and the use of batteries, each with specific advantages and disadvantages, compared to internal combustion engines. The purpose of this work was to evaluate the dynamic response time of a hydrogen fuel cell model powered by green hydrogen, under conditions of sudden and instantaneous power demand, for its integration into wind-based renewable energy systems. Experimental research was carried out on an autonomous installation designed to operate continuously for an unlimited duration, simulating the integration of hydrogen produced from wind sources. The novelty consists of the application of an instrumental method for automatic measurement of the response time of a proton exchange membrane hydrogen fuel cell, based on the automatic acquisition and processing of measured electrical signals. The response time of the fuel cell was compared with that of an internal combustion engine based on the classic Carnot cycle, using a dedicated oscilloscope. The load connection time, the current and voltage variation as a function of time were recorded simultaneously. The results show that the response time of the fuel cell is relatively short (approximately 0.3 ms), much lower than that of the internal combustion engine (0.7 s), being of the order of about 2333 times smaller. In conclusion, the hydrogen fuel cell can be effectively integrated into renewable energy systems for the role of an uninterruptible power supply, with an exceptionally fast dynamic response, suitable for applications in regulating and supporting wind-powered networks. Full article

Achieving Great Britain’s 2050 net-zero target requires strategic integration of hydrogen into the national energy system. This study evaluates the system-wide impacts of hydrogen blending (0–100%) using a bi-level optimisation framework that combines long-term cooperative investment planning with short-term operational Optimal Power and Gas Flow (OPGF) simulation. The strategic layer models infrastructure investment decisions under a cooperative game-theoretic structure, where system value is allocated among electricity, hydrogen production, and storage technologies using the Shapley-value payoff mechanism. Contrary to traditional centralised cost-minimisation models, our findings demonstrate that a cooperative planning structure identifies superior transition pathways. Comparative results reveal that at 100% hydrogen penetration, the cooperative framework reduces total system CO${}_2$ emissions by 31%, lowers operational costs by 26%, and decreases total electricity supply requirements by 8% relative to centralised planning. Furthermore, the cooperative approach significantly enhances economic resilience, yielding a more robust Net Present Value (NPV) across all blending levels compared to centralised planning, while ensuring project profitability at lower blending thresholds (20%) where traditional models remain loss-making. Simulation results indicate that hydrogen blending up to 20% maintains operational stability with manageable increases in operational cost. Full hydrogen conversion (100%) increases peak electricity supply requirements by approximately 30% relative to low-blending scenarios due to electrolysis-driven load expansion and conversion losses. The findings demonstrate that hydrogen blending represents a viable transitional pathway when supported by integrated infrastructure development and cooperative stakeholder coordination, enabling a more efficient and economically sustainable phased progression towards Great Britain’s 2050 net-zero target. Full article

Hydrogen is a clean energy carrier with broad application potential. This study focuses on improving hydrogen production efficiency in a proton exchange membrane (PEM) electrolyzer system that integrates a photovoltaic (PV) array, a battery energy storage system, and the electrolyzer. The PV array is interfaced with the electrolyzer through a buck converter using a maximum power point tracking (MPPT) algorithm to ensure maximum energy harvesting. A key contribution of this work is the integration of a battery system through a dual-active-bridge (DAB) converter. The DAB converter employs a multilayer perceptron (MLP) model to dynamically regulate the electrolyzer current and maintain optimal operating efficiency. An adaptive energy management strategy is further proposed to address solar irradiance fluctuations and enhance long-term operational stability. The MLP model is developed in Python and embedded into a PLECS simulation environment. The simulation results verify the effectiveness of the proposed control approach and efficiency optimization scheme. Throughout the simulation period, the PEM electrolyzer sustains an optimal efficiency of 69.9% under maximum PV power output. A limitation of this study is that the efficiency model is derived from the literature and does not yet consider all operational factors, indicating the need for refinement in future work. Full article

This paper investigates the transient stability characteristics of a DC-coupled off-grid photovoltaic hydrogen production system. A nonlinear state-space model of the system is established by integrating the photovoltaic generation unit, the energy storage unit, and the electrolyzer unit. To enhance system dynamic performance, a virtual DC machine (VDCM) control strategy is introduced for the energy storage converter. Based on the nonlinear system model, a Takagi–Sugeno (TS) fuzzy model is constructed to approximate the system dynamics, and the largest estimated domain of attraction (LEDA) is derived using Lyapunov stability theory. Simulation studies are conducted to evaluate system stability under sudden photovoltaic power fluctuations caused by environmental disturbances, and the obtained LEDA is compared with the simulated attraction domain and the power boundary derived from the Lyapunov eigenvalue method. The results show that the LEDA obtained from the TS fuzzy model can effectively estimate the stability boundary of the system, although it remains slightly conservative. Furthermore, the impacts of VDCM control parameters and electrolyzer operating states on system stability are analyzed. Simulation results demonstrate that appropriate adjustment of system parameters can enlarge the LEDA and significantly improve the transient stability of the off-grid photovoltaic hydrogen production system. Full article

Electrolysis of water is a promising emission-free approach of hydrogen production, making water electrolyzers important for many renewable energy systems. Electrochemical electrodes enriched with nanocatalysts can significantly advance such technologies, but the use of nanomaterials, deployed as packed powders or painted films, is generally limited by durability and reusability challenges. To overcome these deficiencies, we have fabricated hierarchical hybrid electrode (HHE) monoliths comprising carpet-like arrays of multiwalled carbon nanotubes covalently bonded to porous reticulated carbon foams that are further functionalized with strongly attached nanocatalysts. This paper presents our investigation of HHE materials with CNT carpets and palladium nanoparticle (PdNP) catalysts in two key electrolysis reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Their performances in different electrolytes have been evaluated using cyclic voltammetry, linear sweep voltammetry and Tafel analysis. This architecture provided multi-faceted advantages, and the contribution of each nanocomponent in the monolith has been analyzed. The presence of Pd-NP in the HHE also improved the electrode’s tolerance to Cl⁻ ions, which is very promising for saline water electrolysis. These studies indicate that the HHE architecture of electrochemical electrodes can be a versatile and tunable option for future electrochemical systems relevant to renewable energy applications. Full article