Search Results (229)

The development of anode-free sodium metal batteries (AFSMBs) offers a promising pathway to achieve ultrahigh energy density and cost efficiency inherent to conventional sodium ion/metal batteries. However, irreversible Na plating/stripping and dendritic growth remain critical barriers. Herein, we demonstrate that separator engineering is a pivotal strategy for stabilizing AFSMBs. Through systematic evaluation of four separators—2500 separator (PP), 2325 separator (PP/PE/PP), glass fiber (GF), and an Al₂O₃-coated PE membrane, we reveal that the Al₂O₃-coated separator uniquely enables exceptional interfacial kinetics and morphological control. Na||Na symmetric cells with Al₂O₃ coated separator exhibit ultralow polarization (4.5 mV) and the highest exchange current density (1.77 × 10⁻² mA cm⁻²), while the anode-free AlC-NFPP full cells retain 91.6% capacity after 150 cycles at 2C. Specifically, the Al₂O₃ coating homogenizes Na⁺ flux, promotes dense and planar Na deposition, and facilitates near-complete stripping with minimal “dead Na”. This work establishes ceramic-functionalized separators as essential enablers of practical high-energy AFSMBs. Full article

In this work, graphite anodes and lithium iron phosphate (LFP) cathodes are used to examine the effects of sodium hexafluorophosphate (NaPF₆) and potassium hexafluorophosphate (KPF₆) electrolyte additives on the formation of the solid electrolyte interphase and the performance of lithium-ion batteries in both half-cell and full-cell designs. The objective is to assess whether these additives may increase cycle performance, decrease irreversible capacity loss, and improve interfacial stability. Compared to the control electrolyte (1.22 M Lithium hexafluorophosphate (LiPF₆)), cells with NaPF₆ and KPF₆ additives produced less SEI products, which decreased irreversible capacity loss and enhanced initial coulombic efficiency. Following the formation of the solid electrolyte interphase, the specific capacity of the control cell was 607 mA·h/g, with 177 mA·h/g irreversible capacity loss. In contrast, irreversible capacity loss was reduced by 38.98% and 37.85% in cells containing KPF₆ and NaPF₆ additives, respectively. In full cell cycling, a considerable improvement in capacity retention was achieved by adding NaPF₆ and KPF₆. The electrolyte, including NaPF₆, maintained 67.39% greater capacity than the LiPF₆ baseline after 20 cycles, whereas the electrolyte with KPF₆ demonstrated a 30.43% improvement, indicating the positive impacts of these additions. X-ray photoelectron spectroscopy verified that sodium (Na⁺) and potassium (K⁺) ions were present in the SEI of samples containing NaPF₆ and KPF₆. While K⁺ did not intercalate in LFP, cyclic voltammetry confirmed that Na⁺ intercalated into LFP with negligible impact on the energy storage of full cells. These findings demonstrate that NaPF₆ and KPF₆ are suitable additions for enhancing lithium-ion battery performance in the popular artificial graphite/LFP system. Full article

Bird-dropping fouling and hotspot anomalies remain the most prevalent and detrimental defects in utility-scale photovoltaic (PV) plants; their co-occurrence on a single module markedly curbs energy yield and accelerates irreversible cell degradation. However, markedly disparate visual–thermal signatures of the two phenomena impede high-fidelity concurrent detection in existing robotic inspection systems, while stringent onboard compute budgets also preclude the adoption of bulky detectors. To resolve this accuracy–efficiency trade-off for dual-defect detection, we present YOLOv8-SG, a lightweight yet powerful framework engineered for mobile PV inspectors. First, a rigorously curated multi-modal dataset—RGB for stains and long-wave infrared for hotspots—is assembled to enforce robust cross-domain representation learning. Second, the HSV color space is leveraged to disentangle chromatic and luminance cues, thereby stabilizing appearance variations across sensors. Third, a single-head self-attention (SHSA) block is embedded in the backbone to harvest long-range dependencies at negligible parameter cost, while a global context (GC) module is grafted onto the detection head to amplify fine-grained semantic cues. Finally, an auxiliary bounding box refinement term is appended to the loss to hasten convergence and tighten localization. Extensive field experiments demonstrate that YOLOv8-SG attains 86.8% mAP@0.5, surpassing the vanilla YOLOv8 by 2.7 pp while trimming 12.6% of parameters (18.8 MB). Grad-CAM saliency maps corroborate that the model’s attention consistently coincides with defect regions, underscoring its interpretability. The proposed method, therefore, furnishes PV operators with a practical low-latency solution for concurrent bird-dropping and hotspot surveillance. Full article

Rail transit as a high-energy consumption field urgently requires the adoption of clean energy innovations to reduce energy consumption and accelerate the transition to new energy applications. As an energy-saving fluid machinery, the ejector exhibits significant application potential and academic value within this field. This paper reviewed the recent advances, technical challenges, research hotspots, and future development directions of ejector applications in rail transit, aiming to address gaps in existing reviews. (1) In waste heat recovery, exhaust heat is utilized for propulsion in vehicle ejector refrigeration air conditioning systems, resulting in energy consumption being reduced by 12~17%. (2) In vehicle pneumatic pressure reduction systems, the throttle valve is replaced with an ejector, leading to an output power increase of more than 13% and providing support for zero-emission new energy vehicle applications. (3) In hydrogen supply systems, hydrogen recirculation efficiency exceeding 68.5% is achieved in fuel cells using multi-nozzle ejector technology. (4) Ejector-based active flow control enables precise ± 20 N dynamic pantograph lift adjustment at 300 km/h. However, current research still faces challenges including the tendency toward subcritical mode in fixed geometry ejectors under variable operating conditions, scarcity of application data for global warming potential refrigerants, insufficient stability of hydrogen recycling under wide power output ranges, and thermodynamic irreversibility causing turbulence loss. To address these issues, future efforts should focus on developing dynamic intelligent control technology based on machine learning, designing adjustable nozzles and other structural innovations, optimizing multi-system efficiency through hybrid architectures, and investigating global warming potential refrigerants. These strategies will facilitate the evolution of ejector technology toward greater intelligence and efficiency, thereby supporting the green transformation and energy conservation objectives of rail transit. Full article

Fast charging accelerates lithium-ion battery operation but increases the risk of lithium (Li) plating—a process that undermines efficiency, longevity, and safety. Here, we introduce a predictive modeling framework that captures the onset and severity of Li plating under practical fast-charging conditions. By integrating an empirically parameterized SOC threshold model with time-dependent kinetic simulations and Arrhenius based thermal analysis, we delineate operating regimes prone to irreversible Li accumulation. The framework distinguishes reversible and irreversible plating fractions, quantifies energy losses, and identifies a critical activation energy (0.25 eV) associated with surface-limited deposition. Visualizations in the form of severity maps and voltage-zone risk classifications enable direct application to battery management systems. This approach bridges electrochemical degradation modeling with real-time charge protocol design, offering a practical tool for safe, high-performance battery operation. Full article

Driven by stringent emission regulations, advanced combustion modes utilizing turbulent jet ignition technology are pivotal for enhancing the performance of marine low-speed natural gas dual-fuel engines. This review focuses on three novel combustion modes, yielding key conclusions: (1) Compared to the conventional DJCDC mode, the TJCDC mode exhibits a significantly higher swirl ratio and turbulence kinetic energy in the main chamber during initial combustion. This promotes natural gas jet development and combustion acceleration, leading to shorter ignition delay, reduced combustion duration, and a combustion center (CA50) positioned closer to the Top Dead Center (TDC), alongside higher peak cylinder pressure and a faster early heat release rate. Energetically, while TJCDC incurs higher heat transfer losses, it benefits from lower exhaust energy and irreversible exergy loss, indicating greater potential for useful work extraction, albeit with slightly higher indicated specific NOx emissions. (2) In the high-compression ratio TJCPC mode, the Liquid Pressurized Natural Gas (LPNG) injection parameters critically impact performance. Delaying the start of injection (SOI) or extending the injection duration degrades premixing uniformity and increases unburned methane (CH₄) slip, with the duration effects showing a load dependency. Optimizing both the injection timing and duration is, therefore, essential for emission control. (3) Increasing the excess air ratio delays the combustion phasing in TJCPC (longer ignition delay, extended combustion duration, and retarded CA50). However, this shift positions the heat release more optimally relative to the TDC, resulting in significantly improved indicated thermal efficiency. This work provides a theoretical foundation for optimizing high-efficiency, low-emission combustion strategies in marine dual-fuel engines. Full article

Variable-speed reciprocating compressors (VSRCs) have been increasingly used in domestic refrigeration due to their ability to modulate cooling capacity and reduce energy consumption. A detailed understanding of performance-limiting factors such as volumetric and exergetic inefficiencies is essential for optimizing their operation. An experimentally validated simulation model was developed using GT-SUITE to analyze a VSRC operating with R-600a across speeds from 1800 to 6300 rpm. Volumetric inefficiencies were quantified using a stratification methodology, while an exergy-based approach was adopted to assess the main sources of thermodynamic inefficiency in the compressor. Unlike traditional energy analysis, exergy analysis reveals where and why irreversibilities occur, linking them directly to power consumption and providing a framework for optimizing design. Results reveal that neither volumetric nor exergy efficiency varies monotonically with compressor speed. At low speeds, exergetic losses are dominated by the electrical motor (up to 19% of input power) and heat transfer (up to 13.5%). Conversely, at high speeds, irreversibilities from fluid dynamics become critical, with losses from discharge valve throttling reaching 5.8% and bearing friction increasing to 6.5%. Additionally, key volumetric inefficiencies arise from piston–cylinder leakage, which causes up to a 4.5% loss at low speeds, and discharge valve backflow, causing over a 5% loss at certain resonant speeds. The results reveal complex speed-dependent interactions between dynamic and thermodynamic loss mechanisms in VSRCs. The integrated modeling approach offers a robust framework for diagnosing inefficiencies and supports the development of more energy-efficient compressor designs. Full article

Creole avocado is the second most widely produced and consumed variety of avocado globally. Due to its commercialization, limited studies have explored its potential for sustainable applications in biorefinery, particularly focusing on reusing the significant amount of waste generated during its consumption. This research evaluates thermodynamic energy losses of a Creole avocado extractive-based biorefinery, which are of critical importance during the fruit valorization process to determine the efficiency and possibilities of optimization, as well as sustainability impacts, through an exergy balance using computer-aided process engineering. The proposed method utilizes the whole fruit to produce three primary bioproducts, with a focus on implementation in the Montes de María region of Colombia. Following the extended mass and energy balance, an in-depth exergetic analysis was conducted, revealing that all process stages exhibited an exergetic efficiency exceeding 50%. The irreversibilities of the process were calculated as 7763.74 MJ/h, the total waste exergy was 2924.42 MJ/h, and the exergy from industrial waste amounted to 7800.42 MJ/h. These findings highlight the potential for optimizing the sustainability of avocado-based production systems through computer-aided analysis as an effective method. This approach accurately identifies exergy losses at each stage, providing precise numerical data and graphical representations. Additionally, it underscores not only the environmental benefits but also the contribution of these systems to enhancing energy efficiency in agro-industrial applications. Full article

This paper presents an exergy analysis of a 500 MW unit based on actual measurement data. The mathematical model of the system was built in the Aspen HYSYS 2.4 software. The analysis was carried out for two operating states of the unit, at nominal load and at minimum technical load, based on data from two measurement campaigns carried out specifically for this study. The use of measurement data allows an accurate representation of the unit’s current operating conditions, which is crucial for the accuracy of the analysis and the practical implementation of the results obtained. The results show that the dominant sources of exergy losses are the irreversibilities associated with combustion and boiler heat transfer, which account for more than 60% of total exergy losses. The article makes an important contribution to sustainability by identifying opportunities to increase the operating efficiency of the power unit and reduce CO₂ emissions. Proposed technical modifications, such as the modernisation of air heaters, the use of inverters in ventilation systems, or the optimisation of heat exchangers in the turbine system, can significantly improve energy efficiency and reduce the unit’s environmental impact. The analysis provides a valuable resource for the development of energy technologies that promote efficiency and sustainable resource use. Full article

The thermally driven ejector refrigeration system is generally used to recover industrial waste heat to improve the energy efficiency of industrial processes. However, for conventional single-stage ejector refrigeration systems (ERSs), the higher-pressure steam derived from high-temperature waste heat elevates the primary fluid pressure, resulting in significant pressure mismatch with the secondary fluid, which consequently leads to large irreversible losses and substantial degradation in system performance. To address this issue, a novel hybrid ejector refrigeration system (NHERS) is proposed and analyzed under design and off-design conditions using thermodynamics. The results indicate that under design conditions, compared to the conventional single-stage ejector refrigeration system, the proposed hybrid ejector refrigeration system can achieve increases of about 20.6% in the entrainment ratio, around 15.2% in the coefficient of performance (COP), and about 21.4% in exergetic efficiency. Analyzing its performance under off-design conditions to provide technical solutions for the flexible operation of the hybrid ejector refrigeration system proposed in this paper can broaden its application scenarios. Consequently, the proposed NHERS demonstrates remarkable superiority in energy conversion and transfer processes, showing certain application prospects in the field of medium- to high-temperature industrial waste heat recovery. Full article

More efficient energy conversion systems operating with clean energy sources or utilizing waste heat are crucial to minimizing the negative environmental impact associated with conventional systems. This study presents the energy and exergy analysis of a modified heat pump capable of producing cooling and desalinated water using heat dissipated in the condenser. Six refrigerants were analyzed in the theoretical evaluation of the proposed system. These were selected based on their use in vapor compression systems and their thermodynamic properties. A parametric study considering operating temperatures and relative humidities determined that refrigerant R-123 achieved the greatest benefits in terms of the EER, the GOR, and ${\mathsf{\eta }}_{\mathrm{E}\mathrm{x}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y}}$. In contrast, the highest benefits in water desalination were obtained with refrigerant R-410a. For operating conditions of T_E = 0 °C, T_C = 34 °C, and T_CA = 14 °C, the system using refrigerant R-123 achieved an EER, GOR, ${\mathsf{\eta }}_{\mathrm{E}\mathrm{x}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y}}$, D_W, and I_T of 0.82, 2.51, 0.35, 3.46 L/h, and 0.55 kW, respectively. Additionally, the dehumidifier and the evaporator were the components contributing the highest irreversibilities, accounting for approximately 24% and 19.3%, respectively. Full article

Fossil fuels remain essential to the world’s energy supply, but the decline in the quality of the oil extracted has increased the relevance of processes such as hydrocracking. Despite its potential, this process involves high energy consumption. In order to assess its efficiency, an exergy analysis of a conventional hydrocracking unit was carried out using Computer Aided Process Engineering (CAPE) tools. After simulations, the physical and chemical exergies of the input and output streams were calculated, which showed a remarkable energy efficiency of 98.76%, attributable to the high exergy content of the products obtained (171,243,917.70 MJ/h) compared to the residues generated (1,065,290.8 MJ/h). The most significant irreversibilities were found in the Recycle Gas Sweetening stage, while the lowest exergy efficiency, 87.16%, was observed in the Residual Gas Sweetening phase. By valorizing the waste, the overall efficiency of the process increased to 99.26%, which allowed for a 40% reduction in the total irreversibilities. Optimization of the stages with the highest unavoidable losses and better energy integration of the process are suggested to maximize its performance. Full article

Modern power generation aims to maximize the extraction of thermal energy from fossil fuels to produce electricity. Combined cycle power plants, leaders in efficiency, sometimes require an additional steam generator to compensate for insufficient exhaust gas energy in the heat recovery steam generator (HRSG), leading to hybrid combined cycles. This study presents a comprehensive thermodynamic analysis of the hybrid combined cycle power plant located in the Valley of Mexico, operating under both full-load and partial-load conditions. The investigation begins with an energy analysis evaluating key performance parameters under real operating conditions, including the power generation, heat flow supply, thermal efficiency, fuel consumption rates, steam flow, and specific fuel consumption. Subsequently, the analysis examines the performance of the steam cycle using the β factor, which quantifies the relationship between heat flows in the steam generator and the HRSG, to maintain a constant steam flow. This evaluation aims to determine the potential utilization of exhaust gas residual energy for partial steam flow generation in the steam turbine. The study concludes with an exergy analysis to quantify the internal irreversibility flows within the system components and determine the overall exergy efficiency of the power plant. The results demonstrate that, under 100% load conditions, the enhanced utilization of exhaust gases from the HRSG leads to fuel savings of 33,903.36 tons annually and increases the exergy efficiency of the hybrid combined cycle power plant to 54.08%. Full article

Accurate flow measurement is crucial for energy efficiency in industrial applications. This study investigates entropy generation in measuring orifice plates under high-pressure conditions (80 bar, 400 °C) using computational fluid dynamics (CFD) in OpenFOAM. Two turbulence models, k-ω SST and Spalart–Allmaras, are employed to analyze compressible steam flow and identify local entropy sources. Building on recent findings, this research explores the hypothesis that the discharge coefficient reflects entropy generation. The orifice plate’s abrupt flow contraction and expansion contribute to significant energy dissipation, affecting exergy efficiency. By quantifying entropy sources through numerical simulations, this study provides insights into optimizing flow metering techniques and reducing irreversibilities. The results show a strong correlation between entropy generation and the discharge coefficient, offering a new approach to improving measurement accuracy. This research supports the advancement of energy-efficient flow measurement methods, aligning with sustainable engineering practices. Full article

Cracks in reinforced concrete structures compromise strength and durability, particularly in high-performance centrifugal concrete (HPC) piles, where degradation can become irreversible. Despite their high density and low permeability, HPC piles remain vulnerable to cracking, sulfate attack, and chloride penetration, necessitating innovative durability solutions. While self-healing concrete has been widely studied, its application in HPC piles remains unexplored, representing a critical research gap. This study investigates the synergistic use of Bacillus sphaericus bacteria and flax fibers to enhance crack healing, permeability reduction, and mechanical performance in HPC piles. In this research, HPC specimens were fabricated using a specialized centrifugal device and casting process. During the mixing phase, bacteria and flax fibers were incorporated into the concrete. The fresh mix was then spun to form the final specimens. To evaluate bacterial self-healing performance of specimens, controlled random cracks were induced using a compression testing machine. Thereafter, a series of compressive strength tests, 30 min water absorption tests (BS 1881), scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS), and EDS mapping (MAP) were conducted to evaluate self-healing efficiency. Results demonstrated that bacterial activation upon cracking led to calcium carbonate precipitation, effectively sealing cracks, reducing permeability, and enhancing compressive strength. Optimizing bacterial and fiber content further influenced water absorption and mechanical properties in both cubic and centrifugally cast specimens. This study bridges a critical gap by introducing biomaterial-based self-healing in HPC piles, offering a sustainable, cost-effective, and long-term strategy for enhancing the durability of deep foundation systems in aggressive environments. Full article