Energies

18 pages, 33451 KiB

Open AccessArticle

A Parametric Study of an Indirect Evaporative Cooler Using a Spray Dryer Model

by Torsten Berning, Tianbao Gu and Chungen Yin

Energies 2025, 18(16), 4345; https://doi.org/10.3390/en18164345 - 14 Aug 2025

Indirect evaporative coolers (IECs) are becoming a viable alternative to the more energy-intensive traditional HVAC systems for space cooling, especially in arid regions. In this work, a recently developed computational model of an IEC was used to conduct a parametric study. The model [...] Read more.

Indirect evaporative coolers (IECs) are becoming a viable alternative to the more energy-intensive traditional HVAC systems for space cooling, especially in arid regions. In this work, a recently developed computational model of an IEC was used to conduct a parametric study. The model employs a spray dryer model to track the flow path and evaporation rate of droplets. The key parameters investigated were the temperature of the droplets, a bypass effect where the amount of exhaust air and water was reduced to as low as 10%, and the length of the heat exchanger. The results suggest that the wet bulb efficiency could be increased from the previously observed 35% to 72.5% if the water temperature is decreased to 16 °C. In order to drastically increase the performance, the heat exchanger length should be increased from 50 cm to 100 cm, which could still end up in a more compact design overall as fewer plates are required. The bypass study resulted in peak performance when 40% of the secondary air flow was used as working air in conjunction with a proportional reduction in water usage. Overall, the computational model has been employed in an attempt to reduce the bulkiness, increase the efficiency and reduce the water consumption of such a system. Full article

28 pages, 968 KiB

Open AccessArticle

Using Hydro-Pneumatic Energy Storage for Improving Offshore Wind-Driven Green Hydrogen Production—A Preliminary Feasibility Study in the Central Mediterranean Sea

by Oleksii Pirotti, Diane Scicluna, Robert N. Farrugia, Tonio Sant and Daniel Buhagiar

Energies 2025, 18(16), 4344; https://doi.org/10.3390/en18164344 - 14 Aug 2025

Abstract

This paper presents a preliminary feasibility study for integrating hydro-pneumatic energy storage (HPES) with off-grid offshore wind turbines and green hydrogen production facilities—a concept termed HydroGenEration (HGE). This study compares the performance of this innovative concept system with an off-grid direct wind-to-hydrogen plant [...] Read more.

This paper presents a preliminary feasibility study for integrating hydro-pneumatic energy storage (HPES) with off-grid offshore wind turbines and green hydrogen production facilities—a concept termed HydroGenEration (HGE). This study compares the performance of this innovative concept system with an off-grid direct wind-to-hydrogen plant concept without energy storage, both under central Mediterranean wind conditions. Numerical simulations were conducted at high temporal resolution, capturing 10-min fluctuations of open field measured wind speeds at an equivalent offshore wind turbine (WT) hub height over a full 1-year, seasonal cycle. Key findings demonstrate that the HPES system of choice, namely the Floating Liquid Piston Accumulator with Sea Water under Compression (FLASC) system, significantly reduces Proton Exchange Membrane (PEM) electrolyser (PEMEL) On/Off cycling (with a 66% reduction in On/Off events), while maintaining hydrogen production levels, despite the integration of the energy storage system, which has a projected round-trip efficiency of 75%. The FLASC-integrated HGE solution also marginally reduces renewable energy curtailment by approximately 0.3% during the 12-month timeframe. Economic analysis reveals that while the FLASC HPES system does introduce an additional capital cost into the energy chain, it still yields substantial operational savings exceeding EUR 3 million annually through extended PEM electrolyser lifetime and improved operational efficiency. The Levelized Cost of Hydrogen (LCOH) for the FLASC-integrated HGE system, which is estimated to be EUR 18.83/kg, proves more economical than a direct wind-to-hydrogen approach with a levelized cost of EUR 21.09/kg of H₂ produced. This result was achieved through more efficient utilisation of wind energy interfaced with energy storage as it mitigated the natural intermittency of the wind and increased the lifecycle of the equipment, especially that of the PEM electrolysers. Three scenario models were created to project future costs. As electrolyser technologies advance, cost reductions would be expected, and this was one of the scenarios envisaged for the future. These scenarios reinforce the technical and economic viability of the HGE concept for offshore green hydrogen production, particularly in the Mediterranean, and in regions having similar moderate wind resources and deeper seas for offshore hybrid sustainable energy systems. Full article

(This article belongs to the Special Issue Advanced Methods for Hydrogen Production, Storage and Utilization, 2nd Edition)

15 pages, 1461 KiB

Open AccessArticle

Modification of Short-Channel Structures Towards Heat Transfer Intensification: CFD Modeling

by Mateusz Korpyś, Marzena Iwaniszyn, Katarzyna Sindera, Mikołaj Suwak, Andrzej Kołodziej and Anna Gancarczyk

Energies 2025, 18(16), 4343; https://doi.org/10.3390/en18164343 - 14 Aug 2025

Abstract

In this paper, we present the results of heat transfer studies on short-channel structured packing in chemical reactors. Heat transfer coefficients, streamlines, and fluid temperatures were determined using CFD (Computational Fluid Dynamics). CFD simulations were performed for three modified short-channel structures, in which [...] Read more.

In this paper, we present the results of heat transfer studies on short-channel structured packing in chemical reactors. Heat transfer coefficients, streamlines, and fluid temperatures were determined using CFD (Computational Fluid Dynamics). CFD simulations were performed for three modified short-channel structures, in which the front of the walls was rounded to eliminate inlet vortices and the outlet was modified (in three versions) to minimize outlet vortices that disturb the fluid flow. CFD simulations for a classic short-channel structure with straight walls were also performed. The results proved that modified structures experienced significantly more intensive heat transport compared to classic structures. Among the tested modifications, the most promising was Modification 1, for which the Nusselt number increased from 65% to 15% depending on the structure length and the Reynolds number. Additionally, for all modifications considered, there was no inlet vortex, which significantly reduced the transport intensity in the classic structure. Further down the channel, the transport intensity was similar for all structures, including the classic structure. The smoothest flow at the outlet of the structure was observed for Modification 1. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics (CFD) for Heat Transfer Modeling)

17 pages, 2002 KiB

Open AccessArticle

Identification of Critical Transmission Sections Considering N-K Contingencies Under Extreme Events

by Xiongguang Zhao, Xu Ling, Mingyu Yan, Yi Dong, Mingtao He and Yirui Zhao

Energies 2025, 18(16), 4342; https://doi.org/10.3390/en18164342 - 14 Aug 2025

Abstract

Monitoring critical transmission sections is essential for ensuring the operational security of power grids. This paper proposes a systematic method to identify critical transmission sections using the maximum flow–minimum cut theorem. The approach begins by representing the power grid as an undirected graph [...] Read more.

Monitoring critical transmission sections is essential for ensuring the operational security of power grids. This paper proposes a systematic method to identify critical transmission sections using the maximum flow–minimum cut theorem. The approach begins by representing the power grid as an undirected graph and identifying its hanging nodes. The network is then partitioned into several undirected subgraphs based on identified cut points. Each subgraph is transformed into a flow network according to actual power flow data. An efficient minimum cut set search algorithm is developed to locate potential transmission sections. To assess the risk under extreme conditions, a mixed-integer optimization model is formulated to select sections that are vulnerable to overload-induced tripping during N-K line outages caused by natural disasters. Simulation results on the IEEE RTS 24-bus and IEEE 39-bus systems validate the effectiveness and applicability of the proposed method. Full article

(This article belongs to the Special Issue Safe and Stable Operation of Power-Electronics-Dominated Power Systems)

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24 pages, 914 KiB

Open AccessArticle

The Relationship Between the Energy Market, Economic Growth, and Stock Market Performance: A Case Study of COMESA

by Chukwuemelie Chukwubuikem Okpezune, Mehdi Seraj and Hüseyin Özdeşer

Energies 2025, 18(16), 4341; https://doi.org/10.3390/en18164341 - 14 Aug 2025

Abstract

This study examines the relationship between energy use, economic growth, and stock market performance in the COMESA region. It utilizes yearly data from 1990 to 2022, sourced from the World Bank. It applies the Method of Moments Quantile Regression (MMQR), a statistical technique [...] Read more.

This study examines the relationship between energy use, economic growth, and stock market performance in the COMESA region. It utilizes yearly data from 1990 to 2022, sourced from the World Bank. It applies the Method of Moments Quantile Regression (MMQR), a statistical technique that captures how relationships vary across different levels of stock market development. The analysis examines how fossil fuels, renewable energy, and energy imports impact stock market size (market capitalization) at varying levels of performance. The results indicate that both the use of fossil fuels and renewable energy have a significant impact on stock markets, although the effects vary. Renewable energy has the most important positive effect in countries with smaller or weaker markets, suggesting it can help strengthen financial systems in developing economies. However, its impact becomes weaker in stronger markets, possibly due to the costs and challenges of switching to clean energy. On the other hand, economic growth does not always lead to stock market growth, likely due to structural problems in the region that prevent economic progress from boosting financial markets. This study shows how energy policy, economic growth, and market performance are closely linked. It calls for targeted policies to support the shift to renewable energy, manage short-term challenges, and build strong infrastructure to support long-term growth and financial stability. This research helps explain how energy and economic factors shape stock market outcomes in COMESA, offering helpful guidance for investors, researchers, and policymakers aiming for sustainable development. Full article

(This article belongs to the Section A: Sustainable Energy)

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16 pages, 2773 KiB

Open AccessArticle

Enhancing Fuel Cell Hybrid Electric Vehicle Energy Management with Real-Time LSTM Speed Prediction

by Matthieu Matignon, Mehdi Mcharek, Toufik Azib and Ahmed Chaibet

Energies 2025, 18(16), 4340; https://doi.org/10.3390/en18164340 - 14 Aug 2025

Abstract

This paper presents an innovative approach to optimize real-time energy management in fuel cell electric vehicles (FCEVs) through an integrated EMS (iEMS) framework based on a nested concept. Central to our method are two LSTM-based speed prediction models, trained and validated on open-source [...] Read more.

This paper presents an innovative approach to optimize real-time energy management in fuel cell electric vehicles (FCEVs) through an integrated EMS (iEMS) framework based on a nested concept. Central to our method are two LSTM-based speed prediction models, trained and validated on open-source datasets to enhance adaptability and efficiency. The first model, trained on a 27 h real-time database, is embedded within the iEMS for dynamic real-time operation. The second model assesses the impact of incorporating external traffic data on the prediction accuracy, offering a systematic approach to refining speed prediction models. The results demonstrate significant improvements in fuel efficiency and overall performance compared to existing models. This study highlights the promise of data-driven AI models in next-generation FCEV energy management, contributing to smarter and more sustainable mobility solutions. Full article

(This article belongs to the Special Issue Future of Transport: Hybrid Electrification and Hydrogen Integration in Vehicles and Infrastructure)

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15 pages, 1500 KiB

Open AccessArticle

Simultaneous Reductions in NO_x Emissions, Combustion Instability, and Efficiency Loss in a Lean-Burn CHP Engine via Hydrogen-Enriched Natural Gas

by Johannes Fichtner, Jan Ninow and Joerg Kapischke

Energies 2025, 18(16), 4339; https://doi.org/10.3390/en18164339 - 14 Aug 2025

Abstract

This study demonstrates that hydrogen enrichment in lean-burn spark-ignition engines can simultaneously improve three key performance metrics, thermal efficiency, combustion stability, and nitrogen oxide emissions, without requiring modifications to the engine hardware or ignition timing. This finding offers a novel control approach to [...] Read more.

This study demonstrates that hydrogen enrichment in lean-burn spark-ignition engines can simultaneously improve three key performance metrics, thermal efficiency, combustion stability, and nitrogen oxide emissions, without requiring modifications to the engine hardware or ignition timing. This finding offers a novel control approach to a well-documented trade-off in existing research, where typically only two of these factors are improved at the expense of the third. Unlike previous studies, the present work achieves simultaneous improvement of all three metrics without hardware modification or ignition timing adjustment, relying solely on the optimization of the air–fuel equivalence ratio

λ

. Experiments were conducted on a six-cylinder engine for combined heat and power application, fueled with hydrogen–natural gas blends containing up to 30% hydrogen by volume. By optimizing only the air–fuel equivalence ratio, it was possible to extend the lean-burn limit from

λ \approx 1.6

to

λ > 1.9

, reduce nitrogen oxide emissions by up to 70%, enhance thermal efficiency by up to 2.2 percentage points, and significantly improve combustion stability, reducing cycle-by-cycle variationsfrom 2.1% to 0.7%. A defined

λ

window was identified in which all three key performance indicators simultaneously meet or exceed the natural gas baseline. Within this window, balanced improvements in nitrogen oxide emissions, efficiency, and stability are achievable, although the individual maxima occur at different operating points. Cylinder pressure analysis confirmed that combustion dynamics can be realigned with original equipment manufacturer characteristics via mixture leaning alone, mitigating hydrogen-induced pressure increases to just 11% above the natural gas baseline. These results position hydrogen as a performance booster for natural gas engines in stationary applications, enabling cleaner, more efficient, and smoother operation without added system complexity. The key result is the identification of a

λ

window that enables simultaneous optimization of nitrogen oxide emissions, efficiency, and combustion stability using only mixture control. Full article

(This article belongs to the Special Issue Advances in Hydrogen Energy and Fuel Cell Technologies)

27 pages, 3473 KiB

Open AccessReview

Mechanism, Modeling and Challenges of Geological Storage of Supercritical Carbon Dioxide

by Shun Wang, Kan Jin, Wei Zhao, Luojia Ding, Jingning Zhang and Di Xu

Energies 2025, 18(16), 4338; https://doi.org/10.3390/en18164338 - 14 Aug 2025

Abstract

CO₂ geological storage (CGS) is critical for mitigating emissions in hard-to-abate industries under carbon neutrality. However, its implementation faces significant challenges. This paper examines CO₂-trapping mechanisms and proposes key safety measures: the continuous monitoring of in situ CO₂ migration [...] Read more.

CO₂ geological storage (CGS) is critical for mitigating emissions in hard-to-abate industries under carbon neutrality. However, its implementation faces significant challenges. This paper examines CO₂-trapping mechanisms and proposes key safety measures: the continuous monitoring of in situ CO₂ migration and formation pressure dynamics to prevent remobilization, and pre-injection lithological analysis to assess mineral trapping potential. CO₂ injection alters reservoir stresses, inducing surface deformation; understanding long-term rock mechanics (creep, damage) is paramount. Thermomechanical effects from supercritical CO₂ injection pose risks to caprock integrity and fault reactivation, necessitating comprehensive, multi-scale, real-time monitoring for leakage detection. Geostatistical analysis of well log and seismic data enables realistic subsurface characterization, improving numerical model accuracy for risk assessment. This review synthesizes current CGS knowledge, analyzes technical challenges, and aims to inform future site selection, operations, and monitoring strategies. Full article

(This article belongs to the Section B: Energy and Environment)

17 pages, 354 KiB

Open AccessArticle

Research on Environmental Evaluation Index of Carbon-Based Power Generation Formats Under the “Dual Carbon Goals”

by Chaojie Li, Xiankui Wen, Ying Zhang, Ruyue Guo and Siran Peng

Energies 2025, 18(16), 4337; https://doi.org/10.3390/en18164337 - 14 Aug 2025

Abstract

As a major source of carbon emissions, the carbon-based power generation industry requires a scientifically robust environmental performance evaluation system to facilitate its green transition and sustainable development. Focusing on unique transition dynamics across four carbon-based power generation formats, this study compares environmental [...] Read more.

As a major source of carbon emissions, the carbon-based power generation industry requires a scientifically robust environmental performance evaluation system to facilitate its green transition and sustainable development. Focusing on unique transition dynamics across four carbon-based power generation formats, this study compares environmental dimension indicators across typical ESG evaluation frameworks and proposes an innovative evaluation index model of environmental performance based on common metrics, with a particular emphasis on their contribution potential to the “Dual Carbon Goals”. The framework’s core innovation lies in its Dual Carbon-focused indicator system, which evaluates three critical indicators overlooked by mainstream ESG methodologies. It extends to include upstream/downstream processes, addressing gaps in current evaluation systems. The findings reveal that core environmental issues, such as climate change, pollution emissions, and resource utilization, exhibit broad commonality in ESG evaluations. Among the assessed indicators, carbon emission intensity carries the highest weight, underscoring its centrality in each power generation sector’s efforts to align with the Dual Carbon Goals. Furthermore, the analysis demonstrates that underground coal gasification combined cycle power generation has a relatively favorable environmental performance, ranking slightly below natural gas combined cycle but above shale gas combined cycle power generation. In contrast, traditional coal-fired power generation exhibits significantly poorer environmental outcomes, highlighting both the efficacy of technological upgrades in reducing emissions and the urgent need for transitioning away from conventional coal-based power. Full article

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25 pages, 625 KiB

Open AccessReview

Evolution of Shipboard Motor Failure Monitoring Technology: Multi-Physics Field Mechanism Modeling and Intelligent Operation and Maintenance System Integration

by Jun Sun, Pan Sun, Boyu Lin and Weibo Li

Energies 2025, 18(16), 4336; https://doi.org/10.3390/en18164336 - 14 Aug 2025

Abstract

As a core component of both the ship propulsion system and mission-critical equipment, shipboard motors are undergoing a technological transition from traditional fault diagnosis to multi-physical-field collaborative modeling and integrated intelligent maintenance systems. This paper provides a systematic review of recent advances in [...] Read more.

As a core component of both the ship propulsion system and mission-critical equipment, shipboard motors are undergoing a technological transition from traditional fault diagnosis to multi-physical-field collaborative modeling and integrated intelligent maintenance systems. This paper provides a systematic review of recent advances in shipboard motor fault monitoring, with a focus on key technical challenges under complex service environments, and offers several innovative insights and analyses in the following aspects. First, regarding the fault evolution under electromagnetic–thermal–mechanical coupling, this study summarizes the typical fault mechanisms, such as bearing electrical erosion, rotor eccentricity, permanent magnet demagnetization, and insulation aging, and analyzes their modeling approaches and multi-physics coupling evolution paths. Second, in response to the problem of multi-source signal fusion, the applicability and limitations of feature extraction methods—including current analysis, vibration demodulation, infrared thermography, and Dempster–Shafer (D-S) evidence theory—are evaluated, providing a basis for designing subsequent signal fusion strategies. With respect to intelligent diagnostic models, this paper compares model-driven and data-driven approaches in terms of their suitability for different scenarios, highlighting their complementarity and integration potential in the complex operating conditions of shipboard motors. Finally, considering practical deployment needs, the key aspects of monitoring platform implementation under shipborne edge computing environments are discussed. The study also identifies current research gaps and proposes future directions, such as digital twin-driven intelligent maintenance, fleet-level PHM collaborative management, and standardized health data transmission. In summary, this paper offers a comprehensive analysis in the areas of fault mechanism modeling, feature extraction method evaluation, and system deployment frameworks, aiming to provide a theoretical reference and engineering insights for the advancement of shipboard motor health management technologies. Full article

29 pages, 2110 KiB

Open AccessArticle

Advancing Power Supply Resilience: Optimized Transmission Line Retrofitting Through Deep Q-Learning Algorithm

by Lin Liu, Tianjian Wang, Xiuchao Zhu and Chenming Liu

Energies 2025, 18(16), 4335; https://doi.org/10.3390/en18164335 - 14 Aug 2025

Abstract

This study explores practical approaches to improving the reliability of power supply systems through the expansion and optimization of substation power lines. As electricity demand steadily increases, ensuring a stable and efficient power delivery network has become essential to support industrial growth and [...] Read more.

This study explores practical approaches to improving the reliability of power supply systems through the expansion and optimization of substation power lines. As electricity demand steadily increases, ensuring a stable and efficient power delivery network has become essential to support industrial growth and socio-economic development. This study focuses on challenges such as vulnerability to single-line faults, limited transmission capacity, and complex coordination in system operation. To address these issues, the proposed strategy includes building redundant transmission lines, improving network configuration, and applying modern transmission technologies to enhance operational flexibility. Notably, a Deep Q-Learning algorithm is introduced during the planning and optimization process. Its ability to accelerate convergence and streamline decision making significantly reduces computation time while maintaining solution accuracy, thereby increasing overall efficiency in evaluating large-scale network configurations. Simulation results and case studies confirm that such improvements lead to shorter outage durations, enhanced fault tolerance, and better adaptability to future load demands. The findings highlight strong practical value for industrial applications, offering a scalable and cost-conscious solution for strengthening the reliability of modern power systems. Full article

(This article belongs to the Special Issue Flow Control and Optimization in Power Systems)

24 pages, 6991 KiB

Open AccessArticle

Non-Parametric Loop-Shaping Algorithm for High-Order Servo Systems Based on Preset Frequency Domain Specifications

by Pengcheng Lan, Ming Yang and Chaoyi Shang

Energies 2025, 18(16), 4334; https://doi.org/10.3390/en18164334 - 14 Aug 2025

Abstract

Loop shaping the controller for high-order systems, especially in the presence of flexible transmission components such as elastic shafts, gearboxes, and belts commonly found in servo systems, poses significant challenges. Therefore, developing a non-parametric, versatile tuning algorithm that adapts to multi-order systems is [...] Read more.

Loop shaping the controller for high-order systems, especially in the presence of flexible transmission components such as elastic shafts, gearboxes, and belts commonly found in servo systems, poses significant challenges. Therefore, developing a non-parametric, versatile tuning algorithm that adapts to multi-order systems is essential for general control applications. This article first obtains the frequency characteristics of plants through a frequency sweep. Then, based on preset frequency domain specifications, the boundaries representing disturbance rejection and stability constraints are defined in the complex plane with explicit mathematical and graphical expressions. Subsequently, a system of equations is developed based on the tangency between the open-loop curve of the system and the boundaries in the complex plane. On this basis, a versatile tuning algorithm is designed to calculate parameters of a PI controller cascaded with a low-pass filter that ensures the system meets the preset constraints. The proposed approach does not rely on parametric modeling, and the zeros and poles of the controller can be flexibly placed. Experimental validation is carried out on mechanical platforms. Full article

(This article belongs to the Topic Advanced Electrical Machines and Drives Technologies, 2nd Edition)

22 pages, 10294 KiB

Open AccessArticle

Parameter Optimization Design of Adaptive Flaps for Vertical Axis Wind Turbines

by Zhenxu Ran, Weipao Miao, Yongqing Lai, Yurun Pan, Huahao Ou and Ruize Zhang

Energies 2025, 18(16), 4333; https://doi.org/10.3390/en18164333 - 14 Aug 2025

Abstract

To enhance the aerodynamic performance of vertical axis wind turbines (VAWTs) under complex gust conditions, the design parameters of the flap were optimized using the computational fluid dynamics (CFD) method combined with orthogonal experimental design and the SHERPA algorithm, and two gust models [...] Read more.

To enhance the aerodynamic performance of vertical axis wind turbines (VAWTs) under complex gust conditions, the design parameters of the flap were optimized using the computational fluid dynamics (CFD) method combined with orthogonal experimental design and the SHERPA algorithm, and two gust models with mainly high and low wind speeds were generated by a self-compiling program to investigate the effects of three combinations of the chordwise mounting position of the flap, the moment of inertia, and the maximum deflection angle on the aerodynamic performance of the vertical axis wind turbine. The results demonstrated that adaptive flaps reduced the flow separation region and suppressed the formation and development of separation vortices, thereby enhancing aerodynamic performance. The adaptive flap was found to be more effective in high-speed gust environments than in low-speed ones. The optimal configuration—chordwise position at 0.4C, moment of inertia at 6.12 × 10⁻⁵ kg·m², and a maximum deflection angle of 40°—led to a 57.24% improvement relative to the original airfoil. Full article

(This article belongs to the Special Issue Latest Challenges in Wind Turbine Maintenance, Operation, and Safety)

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35 pages, 5873 KiB

Open AccessArticle

Analysis of Vertical Vibrations of a Child Seat Using the ISOFIX System in the Context of Obtaining Electricity to Power a SMART Child Seat

by Damian Frej

Energies 2025, 18(16), 4332; https://doi.org/10.3390/en18164332 - 14 Aug 2025

Abstract

This article presents the results of an experimental study focused on evaluating the potential to harvest electrical energy from vertical vibrations affecting a child car seat installed on an ISOFIX base with a support leg during real driving conditions. The objective was to [...] Read more.

This article presents the results of an experimental study focused on evaluating the potential to harvest electrical energy from vertical vibrations affecting a child car seat installed on an ISOFIX base with a support leg during real driving conditions. The objective was to measure vibration levels in the seat structure and assess the feasibility of converting this mechanical energy into electrical power. The study involved two child seat models, each tested under loads of 9 kg and 15 kg, while driving over smooth asphalt, damaged asphalt, and speed bumps. Acceleration data were collected at three key structural locations: the seat surface, the ISOFIX base, and the support leg. These measurements served as the basis for estimating the mechanical energy available and the resulting electrical output. Findings show that in poor road conditions, the system can generate enough energy to power a 10 µW sensor for more than 42 days. The results confirm the feasibility of using vibration energy harvesting to supply smart safety features such as presence detection, temperature monitoring, or posture sensing in child seats, without the need for batteries or a connection to the vehicle’s electrical system. Full article

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26 pages, 675 KiB

Open AccessArticle

Energy Efficiency Starts in the Mind: How Green Values and Awareness Drive Citizens’ Energy Transformation

by Marcin Awdziej, Dariusz Dudek, Bożena Gajdzik, Magdalena Jaciow, Ilona Lipowska, Marcin Lipowski, Jolanta Tkaczyk, Radosław Wolniak and Robert Wolny

Energies 2025, 18(16), 4331; https://doi.org/10.3390/en18164331 - 14 Aug 2025

Abstract

Background: Understanding the psychological drivers of the energy transition is essential for accelerating the shift to low-carbon societies. The aim of this study is to examine how green consumer values (GCV), energy-saving knowledge (KES) and consumer energy awareness (CEA) jointly shape pro-environmental energy [...] Read more.

Background: Understanding the psychological drivers of the energy transition is essential for accelerating the shift to low-carbon societies. The aim of this study is to examine how green consumer values (GCV), energy-saving knowledge (KES) and consumer energy awareness (CEA) jointly shape pro-environmental energy behaviors (EEB), while accounting for citizens’ perceived cost barriers (PESC). Methods: We conducted a nationally representative Computer-Assisted Web Interviewing (CAWI) survey of 1405 Polish households and employed structural-equation modeling to test an integrated framework linking values, awareness, knowledge, perceived costs and two behavioral domains: high-commitment efficiency investments and low-cost curtailment actions. Results: The structural-equation model confirms that green consumer value significantly enhance both knowledge of energy-saving (β = 0.434) and consumer energy awareness (β = 0.185), thereby driving two distinct pro-environmental pathways: high-commitment efficiency investments (energy efficiency behavior) (β = 0.488) and curtailment behaviors (β = 0.355). Green consumer value also reduces perception of energy-saving costs (β = −0.344), yet these costs themselves exert strong inhibitory effects on both energy efficiency behavior (β = −0.213) and curtailment behaviors (β = −0.302). Conclusions: Our findings validate an integrated value–awareness–behavior framework, demonstrating that fostering green values and improving informational access are critical to enhancing energy-saving practices, while cost-reduction measures remain indispensable. Policymakers should combine value-based education, transparent feedback tools and targeted financial incentives to unlock citizens’ full potential in driving the energy transition. Full article

(This article belongs to the Special Issue Energy Transformation from the Perspectives of the Individual Citizen and the Market)

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28 pages, 13096 KiB

Open AccessArticle

Study on Failure Mechanism and Synergistic Support–Unloading Control Approach in Goaf-Side Roadways in Deep Thick Coal Seams

by Chong Zhang, Yue Sun, Yan Zhang, Yubing Huang, Huayu Yang, Zhenqing Zhang, Chen Chen and Hongdi Tian

Energies 2025, 18(16), 4330; https://doi.org/10.3390/en18164330 - 14 Aug 2025

Abstract

With coal mines’ mining depth increasing, the stress environment in deep mining (including key factors such as high ground stress, strong disturbance, and complex geological structures, as well as stress redistribution after deformation of surrounding roadway rock) is complex, which leads to increasingly [...] Read more.

With coal mines’ mining depth increasing, the stress environment in deep mining (including key factors such as high ground stress, strong disturbance, and complex geological structures, as well as stress redistribution after deformation of surrounding roadway rock) is complex, which leads to increasingly prominent deformation and failure problems for goaf-side roadways in thick coal seams. Surrounding rock deformation is difficult to control, and mine pressure behavior is violent, making traditional support technologies no longer able to meet the mining safety requirements of roadways in deep thick coal seams. Taking the 6311 working face of Tangkou Coal Mine as the engineering research background, this paper systematically summarizes the deformation and failure characteristics of goaf-side roadways in deep thick coal seams through field monitoring, borehole peeping, and other means, and conducts in-depth analysis of their failure mechanisms and influencing factors. Aiming at these problems, a synergistic support–unloading control method for goaf-side roadways is proposed, which integrates roof blasting pressure relief, coal pillar grouting reinforcement, and constant-resistance energy-absorbing anchor cable support. The effects of the unsupported scheme, original support scheme, and synergistic support–unloading control scheme are compared and analyzed through FLAC^3D numerical simulation. Further verification through field application shows that it has remarkable effects in controlling roadway convergence deformation, roof separation, and bolt (cable) stress. Specifically, compared with the original support schemes, the horizontal displacement on the coal pillar side is reduced by 89.5% compared with the original support scheme, and the horizontal displacement on the solid coal side is reduced by 79.3%; the vertical displacement on the coal pillar side is reduced by 45.8% and the vertical displacement on the solid coal side is reduced by 42.4%. Compared with the original support scheme, the maximum deformation of the roadway’s solid coal rib, roof, and coal pillar rib is reduced by 76%, 83%, and 88%, respectively, while the separation between the shallow and deep roof remains at a low level. The coal stress continues fluctuating stably during the monitoring period; the force on the bolts (cables) does not exceed the designed anchoring force, with sufficient bearing reserve space (47% remaining), and no breakage occurs, which fully proves the feasibility and effectiveness of the synergistic support–unloading control technology scheme. This technology realizes the effective control of on-site roadways and provides technical reference for the support engineering of coal mine goaf-side roadways under similar conditions. Full article

(This article belongs to the Topic Support Theory and Technology of Geotechnical Engineering, 2nd Edition)

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19 pages, 6060 KiB

Open AccessArticle

Gramian Angular Field–Gramian Adversial Network–ResNet34: High-Accuracy Fault Diagnosis for Transformer Windings with Limited Samples

by Hongwen Liu, Kun Yang, Guochao Qian, Jin Hu, Weiju Dai, Liang Zhu, Tao Guo, Jun Shi and Dongyang Wang

Energies 2025, 18(16), 4329; https://doi.org/10.3390/en18164329 - 14 Aug 2025

Abstract

Transformers are critical equipment in power transmission and distribution systems, and the condition of their windings significantly impacts their reliable operation. Therefore, the fault diagnosis of transformer windings is of great importance. Addressing the challenge of limited fault samples in traditional diagnostic methods, [...] Read more.

Transformers are critical equipment in power transmission and distribution systems, and the condition of their windings significantly impacts their reliable operation. Therefore, the fault diagnosis of transformer windings is of great importance. Addressing the challenge of limited fault samples in traditional diagnostic methods, this study proposes a small-sample fault diagnosis method for transformer windings. This method combines data augmentation using the Gramian angular field (GAF) and generative adversarial networks (GAN) with a deep residual network (ResNet). First, by establishing a transformer winding fault simulation experiment platform, frequency response curves for three types of faults—axial displacement, bulging and warping, and cake-to-cake short circuits—and different fault regions were obtained using the frequency response analysis method (FRA). Second, a frequency response curve image conversion technique based on the Gramian angular field was proposed, converting the frequency response curves into Gramian angular summation field (GASF) and Gramian angular difference field (GADF) images using the Gramian angular field. Next, we introduce several improved GANs to augment the frequency response data and evaluate the quality of the generated samples. We compared and analysed the diagnostic accuracy of ResNet34 networks trained using different GAF–GAN combination datasets for winding fault types, and we proposed a transformer winding small-sample fault diagnosis method based on GAF-GAN-ResNet34, which can achieve a fault identification accuracy rate of 96.88% even when using only 28 real samples. Finally, we applied the proposed fault diagnosis method to on-site transformers to verify its classification performance under small-sample conditions. The results show that, even with insufficient fault samples, the proposed method can achieve high diagnostic accuracy. Full article

(This article belongs to the Special Issue Advances in Diagnostic Analysis, Strategic Management, and Proactive Maintenance of Electrical Equipment)

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19 pages, 1883 KiB

Open AccessArticle

Evaluation of Maintenance and Modernization of Road Lighting Systems Using Energy Performance Indicators

by Roman Sikora, Przemysław Markiewicz and Ewa Korzeniewska

Energies 2025, 18(16), 4328; https://doi.org/10.3390/en18164328 - 14 Aug 2025

Abstract

This paper presents an assessment of the impact of maintenance of a road lighting luminaire with a high-pressure sodium lamp and an LED luminaire on the lighting parameters on the road and the energy efficiency of the entire road lighting installation. Improper maintenance [...] Read more.

This paper presents an assessment of the impact of maintenance of a road lighting luminaire with a high-pressure sodium lamp and an LED luminaire on the lighting parameters on the road and the energy efficiency of the entire road lighting installation. Improper maintenance of road lighting installations, especially of luminaires, can significantly worsen road traffic safety. In addition, after performing maintenance activities, e.g., after replacing a lamp in the luminaire, the energy consumption of the road lighting installation can increase. Both active and reactive energy can increase. Using the examples of a road luminaire with a high-pressure sodium lamp and an LED luminaire, it was shown that such a phenomenon can occur. An assessment of maintenance in terms of energy performance indicators was performed for the luminaire using the indicators described in the lightning standard and those proposed by the authors of this paper. This approach allows for a comprehensive assessment of maintenance on energy performance indicators—energy efficiency. Full article

(This article belongs to the Special Issue Forecasting and Optimization in Transport Energy Management Systems)

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28 pages, 4927 KiB

Open AccessReview

A Review on Perovskite/Silicon Tandem Solar Cells: Current Status and Future Challenges

by Jingyu Huang and Lin Mao

Energies 2025, 18(16), 4327; https://doi.org/10.3390/en18164327 - 14 Aug 2025

Abstract

Perovskite/Si tandem solar cells (PSTSCs) have emerged as a leading candidate for surpassing the Shockley–Queisser (SQ) efficiency limit inherent to single-junction silicon solar cells. Following their inaugural demonstration in 2015, perovskite/Si tandem solar cells have experienced remarkable technological progression, reaching a certified power [...] Read more.

Perovskite/Si tandem solar cells (PSTSCs) have emerged as a leading candidate for surpassing the Shockley–Queisser (SQ) efficiency limit inherent to single-junction silicon solar cells. Following their inaugural demonstration in 2015, perovskite/Si tandem solar cells have experienced remarkable technological progression, reaching a certified power conversion efficiency of 34.9% by 2025. To elucidate pathways for realizing the full potential of perovskite/Si tandem solar cells, this review commences with an examination of fundamental operational mechanisms in multi-junction photovoltaic architectures. Subsequent sections systematically analyze technological breakthroughs across three critical PSTSC components organized by an optical path sequence: (1) innovations in perovskite photoactive layers through component engineering, additive optimization, and interfacial modification strategies; (2) developments in charge transport and recombination management via advanced interconnecting layers; and (3) silicon subcell architectures. The review concludes with a critical analysis of persistent challenges in device stability, scalability, structural optimization and fabrication method, proposing strategic research directions to accelerate the transition from laboratory-scale achievements to commercially viable photovoltaic solutions. Full article

(This article belongs to the Section A2: Solar Energy and Photovoltaic Systems)

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12 pages, 1565 KiB

Open AccessArticle

Impact of High-Efficiency Filter Pressure Drop on the Energy Performance of Residential Energy Recovery Ventilators

by Suh-hyun Kwon, Beungyong Park and Byoungchull Oh

Energies 2025, 18(16), 4326; https://doi.org/10.3390/en18164326 - 14 Aug 2025

Abstract

As the importance of both indoor air quality (IAQ) and energy efficiency grows in residential buildings, the application of air filters in energy recovery ventilators has become essential. However, high-efficiency filters such as MERV 12 inevitably increase the pressure drop, adversely affecting the [...] Read more.

As the importance of both indoor air quality (IAQ) and energy efficiency grows in residential buildings, the application of air filters in energy recovery ventilators has become essential. However, high-efficiency filters such as MERV 12 inevitably increase the pressure drop, adversely affecting the airflow, fan energy use, and heat exchange balance. This study quantitatively investigates how different levels of filter resistance—from clean conditions to 200% dust loading—affect system airflow, static pressure, exhaust air transfer, and power consumption. A standardized dust loading procedure was adopted to simulate long-term use conditions. The results show a 37% reduction in net supply airflow under heavily clogged filters, while the unit exhaust air transfer ratio increased from 7.2% to 17.7%, exceeding compliance limits. Surprisingly, electrical energy consumption decreased as the fan load dropped with the airflow. Despite an increase in the apparent heat exchange efficiency, this gain was driven by return air recirculation rather than true thermal effectiveness. These findings highlight the need for filter performance-based ERV certification and operational strategies that balance IAQ, energy use, and system compliance. Full article

(This article belongs to the Section B: Energy and Environment)

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15 pages, 3587 KiB

Open AccessArticle

The Role of the Aogula Fault in the Migration of Hydrocarbon Along the Sartu, Putaohua, and Gaotaizi Reservoirs and Its Relationship with Accumulation in the Songliao Basin

by Xiaomei Li, Liang Yang, Lidong Sun, Jiajun Liu, Guozheng Li, Zhuang Cai, Bo Hu, Ying Du, Bowei Zhang, Fei Jiang, Jiao Zhang and Qicai Wu

Energies 2025, 18(16), 4325; https://doi.org/10.3390/en18164325 - 14 Aug 2025

Abstract

To elucidate hydrocarbon enrichment characteristics within the Sartu (S), Putaohua (P), and Gaotaizi (G) reservoirs near the Aogula Fault in the northern Songliao Basin, this study systematically analyzes the fault’s influence on hydrocarbon migration and accumulation, based on an investigation of migration pathways [...] Read more.

To elucidate hydrocarbon enrichment characteristics within the Sartu (S), Putaohua (P), and Gaotaizi (G) reservoirs near the Aogula Fault in the northern Songliao Basin, this study systematically analyzes the fault’s influence on hydrocarbon migration and accumulation, based on an investigation of migration pathways along fault zones and sandstone bodies. The results demonstrate that, except at its northern terminus, the Aogula Fault terminates hydrocarbon migration within the S reservoir sandstones, thereby promoting hydrocarbon accumulation near the fault zone. This is a primary reason for the prevalence of productive drilling targets in this region. Six vertical diversion zones are identified along the fault trace, uniformly spaced from southwest to northeast. These zones facilitate vertical migration of hydrocarbons from the G and P reservoirs into the overlying S reservoir, accounting for the significantly greater hydrocarbon enrichment observed in the S reservoir compared to the underlying formations. Furthermore, excluding the eastern and western extremities, lateral diversion zones characterize the remainder of the fault. These zones enhance lateral hydrocarbon migration from the southwestern segment towards the northeastern segment, resulting in significantly higher accumulation in the northeastern section relative to the southwestern section. Full article

(This article belongs to the Special Issue Petroleum Exploration, Development and Transportation)

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23 pages, 9501 KiB

Open AccessArticle

Experimental Verification of Blocking a Water-Bearing Zone Using CO₂ Reactive Grout for Methane Hydrate Development

by Rongchang Zhang, Takatoshi Ito, Shungo Abe and Takashi Uchiumi

Energies 2025, 18(16), 4324; https://doi.org/10.3390/en18164324 - 14 Aug 2025

Abstract

Tests during methane hydrate (MH) production in Japan have shown that excessive water production is a primary challenge in MH development. It can lead to sand production, inhibit effective reservoir depressurization, and hinder gas production. This study investigated the ability of a reactive [...] Read more.

Tests during methane hydrate (MH) production in Japan have shown that excessive water production is a primary challenge in MH development. It can lead to sand production, inhibit effective reservoir depressurization, and hinder gas production. This study investigated the ability of a reactive grout, produced by the in situ reaction of CO₂ with sodium silicate (SS), to inhibit water generation from unconsolidated sand layers by forming a water-blocking gel barrier. The performance of this grout was evaluated through laboratory experiments using silica sand as a porous medium. Under controlled conditions, diluted SS and CO₂ were sequentially injected. The injection and gelation processes were monitored in real time using CT scanning, and SEM was employed to analyze the microstructure of the reaction products. The results indicated that SS exhibited piston-like flow, with elevated concentrations increasing viscosity and promoting more uniform injection. CO₂ injection resulted in successful in situ gel formation. A homogeneous gel distribution decreased permeability by ~98% when the SS concentration was 25 wt%. However, at 50 wt%, rapid localized gelation caused preferential flow paths and reduced sealing efficiency. These findings highlight the potential of CO₂ reactive grouting for water management in MH exploitation and the importance of optimizing injection parameters. Full article

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39 pages, 854 KiB

Open AccessArticle

A Hybrid MCDM Approach to Optimize Molten Salt Selection for Off-Grid CSP Systems

by Ghazi M. Magableh, Mahmoud Z. Mistarihi and Saba Abu Dalu

Energies 2025, 18(16), 4323; https://doi.org/10.3390/en18164323 - 14 Aug 2025

Abstract

Transitioning to sustainable energy systems demands the creation of innovative methods that deliver dependable and effective renewable energy technologies. CSP systems that integrate parabolic trough designs with thermal energy storage (TES) systems provide essential solutions to overcome energy intermittency challenges. Molten salts serve [...] Read more.

Transitioning to sustainable energy systems demands the creation of innovative methods that deliver dependable and effective renewable energy technologies. CSP systems that integrate parabolic trough designs with thermal energy storage (TES) systems provide essential solutions to overcome energy intermittency challenges. Molten salts serve dual functions as heat transfer fluids (HTFs) and thermal energy storage (TES) media, making them critical to CSP system performance improvements. The study introduces a hybrid MCDM framework that combines the CRITIC method for objective weighting with the SWARA approach for expert-adjusted weighting and utilizes an enhanced Lexicographic Goal Programming to evaluate molten salt options for off-grid parabolic trough systems. The evaluation process considered melting point alongside thermal stability while also assessing cost-effectiveness, recyclability, and safety requirements. The use of Pareto front analysis helped identify non-dominated salts, which then underwent a tiered optimization process emphasizing safety, performance, and sustainability features. Results confirm that the ternary nitrate composition Ca(NO₃)₂:NaNO₃:KNO₃ offers the best overall performance across all tested policy scenarios, driven by its superior thermophysical properties. Solar Salt (NaNO₃-KNO₃) consistently ranks as a robust second choice, excelling in economic and sustainability metrics. The proposed approach provides a flexible, policy-sensitive framework for material selection tailored to enhance the efficiency and sustainability of off-grid CSP systems and support the renewable energy objectives. Full article

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23 pages, 1227 KiB

Open AccessReview

Comparative Assessment of LEED, BREEAM, and WELL: Advancing Sustainable Built Environments

by Elias Tsirovasilis, Martha Katafygiotou and Chrystala Psathiti

Energies 2025, 18(16), 4322; https://doi.org/10.3390/en18164322 - 14 Aug 2025

Abstract

This study compares the LEED, BREEAM, and WELL certification systems using the Triple Bottom Line (TBL) framework to assess their performance across environmental, social, and economic dimensions and their alignment with sustainable development goals. A structured secondary analysis was conducted on over 50 [...] Read more.

This study compares the LEED, BREEAM, and WELL certification systems using the Triple Bottom Line (TBL) framework to assess their performance across environmental, social, and economic dimensions and their alignment with sustainable development goals. A structured secondary analysis was conducted on over 50 peer-reviewed articles, case studies, and official certification manuals. Inclusion criteria required documented design targets and post-occupancy outcomes for certified buildings (2014–2024). A two-phase analytical model was applied: first, evaluating each system’s structure and priorities; then benchmarking them using the TBL framework to assess how holistically each addresses sustainability. Results show that LEED leads to energy optimization, BREEAM to lifecycle integration, and WELL to occupant health and indoor environmental quality. However, all systems exhibit post-occupancy performance gaps: LEED and BREEAM underperform by 15–30% in energy use, while WELL-certified projects may exceed 30% due to stringent indoor comfort demands. These findings highlight the need to integrate real-time post-occupancy evaluation into certification protocols. To improve overall effectiveness, the study proposes enhancements such as adaptive performance tracking, occupant feedback loops, and dynamic benchmarking aligned with actual building use. By identifying both the comparative strengths and systemic limitations of the three frameworks, this research contributes to the refinement of green building assessment tools. Practical implications include (1) integrating post-occupancy evaluation into certification renewal cycles, (2) adopting hybrid certification strategies to improve sustainability coverage, and (3) designing benchmarking tools that reflect real-world operational data. Full article

(This article belongs to the Special Issue Advanced Technologies for Energy-Efficient Buildings)

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14 pages, 372 KiB

Open AccessCommunication

Multi-Level Coordination-Level Evaluation Study of Source-Grid-Load-Storage Based on AHP-Entropy Weighting

by Benhong Wang, Ligui Wu, Peng Zhang, Fangqing Zhang and Jiang Guo

Energies 2025, 18(16), 4321; https://doi.org/10.3390/en18164321 - 14 Aug 2025

Abstract

With the development of the power system, the ability to present a comprehensive and reasonable evaluation of its coordination level has become important for the collaborative optimization of source-grid-load-storage. By identifying uncertain risk factors fully, the present work develops a multi-level coordination-level evaluation [...] Read more.

With the development of the power system, the ability to present a comprehensive and reasonable evaluation of its coordination level has become important for the collaborative optimization of source-grid-load-storage. By identifying uncertain risk factors fully, the present work develops a multi-level coordination-level evaluation of source-grid-load-storage based on AHP-entropy weighting. Building on previous studies, the present work reflects interactive characteristics of the collaborative optimization of source-grid-load-storage. Meanwhile, to determine the indicator weighting more reasonably, AHP-entropy weighting is adopted; this method combines the advantages of subjective AHP weighting and objective entropy weighting. Firstly, the multi-level coordination-level evaluation of source-grid-load-storage is introduced and includes both direct factors and indirect factors. Next, based on AHP-entropy weighting, the indicator weighting of the multi-level coordination-level evaluation is determined. Lastly, a case study is conducted that involves evaluating the coordination levels of the power systems of three regions. Additionally, the effectiveness of the multi-level coordination-level evaluation of source-grid-load-storage is validated. Full article

(This article belongs to the Special Issue Advanced Application for Renewable Energy Sources: Modelling, Management Control, Data Monitoring, Health Management, Design and Improvement)

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21 pages, 3882 KiB

Open AccessArticle

Cost Implications for Collaborative Microgrids: A Case Study of Lean—Heijunka Microgrid Operations Mitigating Renewable Energy Volatility

by Hanaa Feleafel, Michel Leseure and Jovana Radulovic

Energies 2025, 18(16), 4320; https://doi.org/10.3390/en18164320 - 14 Aug 2025

Abstract

The volatility of renewable energy outputs is a well-known obstacle that has hindered the integration of more renewables in the UK’s energy mix, as the current network was not designed to handle such swings. Microgrids (MGs) may function as an effective means of [...] Read more.

The volatility of renewable energy outputs is a well-known obstacle that has hindered the integration of more renewables in the UK’s energy mix, as the current network was not designed to handle such swings. Microgrids (MGs) may function as an effective means of integrating more renewables, particularly if they can effectively control the volatility of renewables at a smaller scale (the MG level) through a collaborative operational strategy. This paper focuses on the management of renewable energy fluctuations in MGs, proposing a pre-contract order update (COU) strategy based on the lean balancing (Heijunka) concept. The study compares the performance of collaborative and selfish MGs in terms of levelized cost of electricity (LCOE), order volatility, and carbon emissions. Two simulations models for the collaborative and selfish MGs were implemented, while considering two distinct backup generation scenarios within the MG system. The findings indicate a two-dimensional trade-off between the collaborative MG models, which are 61% more sustainable and reduce order volatility to the utility grid by 55%, and the selfish MGs, which incur lower energy consumption costs reduced by only 19%. These findings highlight the potential of collaborative MGs in enhancing grid stability and supporting broader renewable energy integration goals. Full article

(This article belongs to the Special Issue Intelligent Operation and Management of Microgrids, 2nd Edition)

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17 pages, 2285 KiB

Open AccessArticle

Simulation of Biomass Gasification and Syngas Methanation for Methane Production with H₂/CO Ratio Adjustment in Aspen Plus

by Suaad Al Zakwani, Miloud Ouadi, Kazeem Mohammed and Robert Steinberger-Wilckens

Energies 2025, 18(16), 4319; https://doi.org/10.3390/en18164319 - 14 Aug 2025

Abstract

In the context of advancing sustainable energy solutions, this paper provides a detailed modelling study of the process integration of biomass gasification to produce syngas and subsequent methanation for methane production. The process is assumed to take place in a circulating fluidised bed [...] Read more.

In the context of advancing sustainable energy solutions, this paper provides a detailed modelling study of the process integration of biomass gasification to produce syngas and subsequent methanation for methane production. The process is assumed to take place in a circulating fluidised bed and three adiabatic fixed-bed reactors. To address the low H₂/CO ratio of syngas produced from biomass gasification using air, three pre-methanation scenarios were evaluated: water gas shift reaction (scenario 1), H₂ addition through Power-to-Gas (scenario 2), and splitting syngas into pure H₂ and CO and then recombining them in a 3:1 ratio (scenario 3). The findings reveal that each scenario presents a unique balance of efficiency, decarbonisation potential, and technological integration. Scenario 2 achieves the highest overall efficiency at 62%, highlighting the importance of integrating renewable electricity into the methane industry. Scenario 1, which incorporates WGS and CO₂ capture, offers an environmentally friendly solution with an overall efficiency of 59%. In contrast, Scenario 3, involving H₂/CO separation and recombination, achieves only 44.4% efficiency due to energy losses during separation, despite its operational simplicity. Methane yields were highest in Scenario 1, while Scenario 2 offers the most significant potential for integration with decarbonised power systems. The model was validated using published data and feedstock characteristics from experimental work and industrial projects. The results showed good agreement and supported the accuracy of the simulation in reflecting realistic biomass processing for methane production. Full article

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28 pages, 724 KiB

Open AccessArticle

The Impact of the Renewable Energy Transition on Economic Growth in BRICS Nations

by Nyiko Worship Hlongwane and Hlalefang Khobai

Energies 2025, 18(16), 4318; https://doi.org/10.3390/en18164318 - 14 Aug 2025

Abstract

The BRICS countries have been increasingly prioritizing electricity transition as a crucial step towards achieving sustainable growth, energy security, and mitigating climate change. As major emerging economies, the BRICS nations will play a significant role in the global energy landscape since their transition [...] Read more.

The BRICS countries have been increasingly prioritizing electricity transition as a crucial step towards achieving sustainable growth, energy security, and mitigating climate change. As major emerging economies, the BRICS nations will play a significant role in the global energy landscape since their transition to renewable energy sources holds a significant implication for global energy markets and environmental sustainability. This study investigates the impact of the renewable energy transition on economic growth in BRICS nations from 1990 to 2023, employing a panel NARDL, DOLS, and FMOLS models. This study investigates the relationship between disaggregated renewable energy sources and economic growth. The findings show that renewable energy’s impact on economic growth varies across countries and depends on the type of renewable energy source. Specifically, hydropower, and wind power are found to have significant positive impacts on economic growth in some BRICS countries, while other renewables and trade openness have insignificant impacts. To foster economic growth and the expansion of renewable energy, it is essential for policymakers to focus on investments in hydropower and wind energy. Furthermore, they should encourage trade liberalization, as well as nuclear power development, and enhance regional collaboration. This study offers significant contributions to the current body of literature on the renewable energy–economic growth nexus, supplying crucial insights for both policymakers and researchers. Full article

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20 pages, 7881 KiB

Open AccessArticle

Numerical Investigation of Clocking Effects on the Hydraulic Performance of Pump–Turbine in Pump Mode

by Lisheng Zhang, Yongbo Li, Ming Ma, Lijun Kong, Zhenghai Huang, Lintao Xu and Bofu Wang

Energies 2025, 18(16), 4317; https://doi.org/10.3390/en18164317 - 14 Aug 2025

Abstract

This study numerically investigates clocking effects on pump–turbine hydraulic performance in pump mode. Analyzing the influence of clock position on pressure loss characteristics under three flow conditions and its correlation with internal flow. By integrating local hydraulic loss theory and vortex evolution analysis, [...] Read more.

This study numerically investigates clocking effects on pump–turbine hydraulic performance in pump mode. Analyzing the influence of clock position on pressure loss characteristics under three flow conditions and its correlation with internal flow. By integrating local hydraulic loss theory and vortex evolution analysis, the operational mechanism is elucidated. Key results show that the stay vane clock position significantly impacts off-design conditions, causing maximum efficiency differences of 0.855% at 0.8Q_d and 0.805% at 1.2Q_d. At the design condition, guide vane clocking position has a more pronounced effect, yielding a maximum inter-scheme efficiency difference of 0.330%. The optimal scheme positions the tongue at the guide vane trailing edge and 1/4 of the stay vane flow path, minimizing time-averaged losses and enhancing flow stability. The clocking effect alters the scale and intensity of volute dual-vortex structures, significantly increasing energy loss at vortex interfaces, with volute loss identified as the primary factor in performance variation. This work provides a theoretical foundation for applying clocking effects in pump–turbine engineering. Full article

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23 pages, 2768 KiB

Open AccessArticle

Nonlinear Algebraic Parameter Estimation of Doubly Fed Induction Machine Based on Rotor Current Falling Curves

by Alexander Glazyrin, Dmitriy Bunkov, Evgeniy Bolovin, Yusup Isaev, Vladimir Kopyrin, Sergey Kladiev, Alexander Filipas, Sergey Langraf, Rustam Khamitov, Vladimir Kovalev, Evgeny Popov, Semen Popov and Marina Deneko

Energies 2025, 18(16), 4316; https://doi.org/10.3390/en18164316 - 14 Aug 2025

Abstract

Currently, wind turbines utilize doubly fed induction machines that incorporate a frequency converter in the rotor circuit to manage slip energy. This setup ensures a stable voltage amplitude and frequency that align with the alternating current. It is crucial to accurately determine the [...] Read more.

Currently, wind turbines utilize doubly fed induction machines that incorporate a frequency converter in the rotor circuit to manage slip energy. This setup ensures a stable voltage amplitude and frequency that align with the alternating current. It is crucial to accurately determine the parameters of the equivalent circuit from the rotor side of the vector control system of the frequency converter. The objective of this study is to develop a method for the preliminary identification of the doubly fed induction machines parameters by analyzing the rotor current decay curves using Newton’s method. The numerical estimates of the equivalent circuit parameters a doubly fed induction machines with a fixed short-circuited rotor are obtained during the validation of the results on a real plant. It is along with the integral errors of deviation between the experimental rotor current decay curve and the response of the adaptive regression model. The integral errors do not exceed 4% in nearly all sections of the curves. It is considered acceptable in engineering practice. The developed algorithm for the preliminary identification for the parameters of the doubly fed induction machines substitution scheme can be applied with the configuring machines control systems, including a vector control system. Full article

(This article belongs to the Special Issue Advanced Control Strategies for Multiphase Induction Generators: Design, Optimization, and Application 2024)

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Energies, Volume 18, Issue 16 (August-2 2025) – 136 articles

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