Energies

34 pages, 3428 KB

Open AccessReview

A Literature Review on Energy Management Systems and Their Application on Harbour Activities

by Dimitrios Apostolou

Energies 2025, 18(18), 4887; https://doi.org/10.3390/en18184887 (registering DOI) - 14 Sep 2025

The growing global concern for sustainability and energy conservation has led to the adoption of energy management systems to minimise the impacts of energy intensive processes. This study reviews the evolution, the applications, and implementation techniques of energy management systems with an emphasis [...] Read more.

The growing global concern for sustainability and energy conservation has led to the adoption of energy management systems to minimise the impacts of energy intensive processes. This study reviews the evolution, the applications, and implementation techniques of energy management systems with an emphasis on harbour operations. Through the mapping of the research on energy management systems post-1973, the literature review demonstrated a substantial transformation of the systems from basic monitoring in the building sector to complex artificial intelligence analyses in smart and microgrids, industries, renewable energy sources integration, transportation, and harbours. Initial broad search (1973–2025) identified 22,003 EMS-related records; targeted port–EMS queries yielded 214 records, of which 139 unique records remained after de-duplication and 78 full texts were assessed. Finally, 27 studies were included in the quantitative synthesis. A meta-analysis in conjunction with an article review, and a weighted sum model coupled with sensitivity analyses revealed promising results for harbour energy management system implementation in terms of peak/load shifting, on-shore power supply, and real-time energy monitoring. The findings showed that energy management system efficacy is linked to maturity levels and strategic deployment of the measures/policies in each stage. Full article

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26 pages, 526 KB

Open AccessArticle

Assessment of Sustainable Energy Development in European Union—Correspondence Analysis

by Janina Jędrzejczak-Gas, Joanna Wyrwa and Anetta Barska

Energies 2025, 18(18), 4886; https://doi.org/10.3390/en18184886 (registering DOI) - 14 Sep 2025

Abstract

The energy transition has now been recognised by European Union (EU) member states as a necessary condition for their long-term development. The process of energy transformation is predicated on the simultaneous implementation of the Sustainable Development Goals, which present a considerable challenge for [...] Read more.

The energy transition has now been recognised by European Union (EU) member states as a necessary condition for their long-term development. The process of energy transformation is predicated on the simultaneous implementation of the Sustainable Development Goals, which present a considerable challenge for modern economies and impose significant restrictions on their functioning. The objective of this article is to evaluate the transformation of EU member states in the field of sustainable energy development and to categorise them based on their alignment with Sustainable Development Goal No. 7 of the United Nations Agenda 2030, concerning affordable and clean energy, in 2015 and 2023. The monitoring of the progress of the energy transition, as well as the examination of its temporal trends and spatial characteristics, can provide a fundamental analysis framework for the strategic development of energy policy in the EU at national and regional levels. An important approach for this endeavour is the indicator-based assessment of trends. The correspondence analysis proposed in this study and the hierarchical classification, which was intended to help link categories in a two-dimensional space, have the potential to facilitate a more comprehensive assessment of the degree to which EU member states are developing sustainable energy. The study results confirmed significant heterogeneity among the EU-27 countries in terms of energy sustainability. In both 2015 and 2023, the groups of EU countries that achieved a certain level of energy sustainability were identified. However, it should be noted that the composition of each group changed in 2023 compared to 2015. Moreover, no group of EU countries was without its own particular strengths and weaknesses. The results provide opportunities for their interpretation, both in terms of analysing changes in individual indicators and in terms of the global assessment of sustainable development in individual countries. The adoption of an original research approach, divergent from previous studies, for the new timeframe contributes to the resolution of the research gap in empirical studies concerning the classification of EU member states in terms of SDG7 implementation. Full article

(This article belongs to the Special Issue Green Innovation and Sustainable Energy Transition: Opportunities and Challenges)

25 pages, 5425 KB

Open AccessArticle

A Novel Nonlinear Droop Function for Flexible Operation of Grid-Forming Inverters

by Salman Harasis

Energies 2025, 18(18), 4885; https://doi.org/10.3390/en18184885 (registering DOI) - 14 Sep 2025

Abstract

This paper introduces the Exponent Droop Function (EDF), a nonlinear grid-forming (GFM) control paradigm that enhances the flexibility and performance of droop-based control in microgrids. Unlike conventional droop mechanisms, the EDF establishes a generalized framework that unifies multiple nonlinear droop relations, enabling adaptive [...] Read more.

This paper introduces the Exponent Droop Function (EDF), a nonlinear grid-forming (GFM) control paradigm that enhances the flexibility and performance of droop-based control in microgrids. Unlike conventional droop mechanisms, the EDF establishes a generalized framework that unifies multiple nonlinear droop relations, enabling adaptive shaping of droop characteristics through the adjustment of a single tuning parameter. This capability effectively mitigates the inherent limitations of traditional droop, particularly frequency degradation, while ensuring flexible power-sharing and improved dynamic performance. The proposed approach is rigorously validated through (i) detailed system modeling and small-signal stability analysis of EDF-controlled microgrids under variable load and droop conditions, (ii) dynamic assessments of distributed generators (DGs) supported by frequency-domain analysis, and (iii) extensive time-domain simulations encompassing seven representative operating scenarios. Comparative studies against state-of-the-art GFM controllers demonstrate that EDF achieves superior transient and steady-state performance with minimal control complexity, highlighting its potential as a practical and efficient next-generation GFM control strategy for microgrids. Full article

(This article belongs to the Topic Advanced Operation, Control, and Planning of Intelligent Energy Systems)

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19 pages, 1341 KB

Open AccessArticle

Model Predictive Control of a Parallel Transformerless Static Synchronous Series Compensator for Power Flow Control and Circulating Current Mitigation

by Wei Zuo, Xuejiao Pan and Li Zhang

Energies 2025, 18(18), 4884; https://doi.org/10.3390/en18184884 (registering DOI) - 14 Sep 2025

Abstract

The paper proposes a parallel transformerless (TL) static synchronous series compensator (SSSC) for the control of power flow along the power distribution lines under balanced or unbalanced voltages. This new SSSC configuration offers the advantages of a fast dynamic response, light weight, and [...] Read more.

The paper proposes a parallel transformerless (TL) static synchronous series compensator (SSSC) for the control of power flow along the power distribution lines under balanced or unbalanced voltages. This new SSSC configuration offers the advantages of a fast dynamic response, light weight, and high efficiency. By connecting multiple SSSCs in parallel, the current rating is increased, which improves the grid power transfer capabilities and flexibility. However, there may be circulating current flowing between the parallel-connected inverters, hence causing losses. A modified model predictive control scheme is thus developed, which ensures that the proposed SSSC accurately tracks the reference currents while effectively mitigating the circulating current. The model and cost function of the controller are derived and analyzed in the paper. A real-time simulation of a power line with the parallel TL SSSC controlled by a hardware-in-loop (HIL) DSP is developed to validate the performance of this device under both balanced and unbalanced line voltages. Full article

(This article belongs to the Special Issue Advanced Inverter Technologies: Enhancing Efficiency in Power Conversion Systems)

21 pages, 2320 KB

Open AccessArticle

Residential Electricity Consumption Behaviors in Eastern Romania: A Non-Invasive Survey-Based Assessment of Consumer Patterns

by Codrin Donciu, Elena Serea and Marinel Costel Temneanu

Energies 2025, 18(18), 4883; https://doi.org/10.3390/en18184883 (registering DOI) - 14 Sep 2025

Abstract

This study investigates residential electricity consumption behaviors in the Moldova region of Romania, with a focus on identifying consumption patterns through a non-invasive, survey-based approach. Unlike intrusive monitoring or smart metering methods, the survey collected detailed self-reported data on appliance use, time-of-use awareness, [...] Read more.

This study investigates residential electricity consumption behaviors in the Moldova region of Romania, with a focus on identifying consumption patterns through a non-invasive, survey-based approach. Unlike intrusive monitoring or smart metering methods, the survey collected detailed self-reported data on appliance use, time-of-use awareness, and household characteristics across 55 residential units. The analysis introduced an error-based metric comparing calculated and billed consumption, modeled under a normal distribution to assess estimation accuracy. Results reveal a stable dominance of mid-range consumption bands, alongside emerging stratification, with an increasing share of households transitioning to higher consumption levels. Appliance-level analyses highlight systematic underestimation of high-load devices, such as washing machines and HVAC systems, reflecting perceptual gaps in consumer awareness. Furthermore, demographic profiling indicates that in many households, high-duration and high-load consumers differ, with women more frequently assuming dual roles in energy-intensive tasks within the traditional Eastern European context. The findings demonstrate the potential of non-invasive survey methods to capture behavioral dimensions of energy use that remain underexplored in the absence of smart metering infrastructure, offering new insights into demand-side heterogeneity in peripheral EU regions. Full article

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24 pages, 1062 KB

Open AccessArticle

Optimized Dispatch of a Photovoltaic-Inclusive Virtual Power Plant Based on a Weighted Solar Irradiance Probability Model

by Jiyun Yu, Xinsong Zhang, Xiangyu He, Chaoyue Wang, Jun Lan and Jiejie Huang

Energies 2025, 18(18), 4882; https://doi.org/10.3390/en18184882 (registering DOI) - 14 Sep 2025

Abstract

Under China’s dual-carbon strategic objectives, virtual power plants (VPPs) actively participate in the coupled electricity–carbon market through the optimized scheduling of distributed energy resources, simultaneously stabilizing grid operations and reducing carbon emissions. Photovoltaic (PV) generation, a cornerstone resource within VPP systems, introduces significant [...] Read more.

Under China’s dual-carbon strategic objectives, virtual power plants (VPPs) actively participate in the coupled electricity–carbon market through the optimized scheduling of distributed energy resources, simultaneously stabilizing grid operations and reducing carbon emissions. Photovoltaic (PV) generation, a cornerstone resource within VPP systems, introduces significant challenges in scheduling due to its inherent output variability. To increase the accuracy in the characterization of the PV output uncertainty, a weighted probability distribution of solar irradiance, based on historical irradiance data, is newly proposed. The leveraging rejection sampling technique is applied to generate solar irradiance scenarios that are consistent with the proposed weighted solar irradiance probability model. Further, a confidence interval-based filtering mechanism is applied to eliminate extreme scenarios, ensuring statistical credibility and enhancing practicability in actual dispatch scenarios. Based on the filtered scenarios, a novel dispatch strategy for the VPP operation in the electricity–carbon market is proposed. Numerical case studies verify that scenarios generated by the weighted solar irradiance probability model are capable of closely replicating historical PV characteristics, and the confidence interval filter effectively excludes improbable extreme scenarios. Compared to conventional normal distribution-based methods, the proposed approach yields dispatch solutions that are more closely aligned with the optimal dispatch of the historical irradiance data, demonstrating the improved accuracy in the probabilistic modelling of the PV output uncertainty. Consequently, the obtained dispatch strategy shows the improved capability to ensure the market revenue of the VPP considering the fluctuations of the PV output. Full article

(This article belongs to the Special Issue New Power System Planning and Scheduling)

17 pages, 2319 KB

Open AccessArticle

Theoretical and Kinetic Study of Hydrogen Abstraction Reactions of Xylene Isomers with Hydrogen and Hydroxy Radicals

by Cheng Li, Shoulong Lin and Yuqiang Li

Energies 2025, 18(18), 4881; https://doi.org/10.3390/en18184881 (registering DOI) - 14 Sep 2025

Abstract

Xylenes are important components of gasoline fuels, and their hydrogen abstraction reactions are crucial in the consumption pathways of combustion processes. In existing models, rate constants for these reactions are commonly derived by estimation, which can introduce large uncertainties into models and lead [...] Read more.

Xylenes are important components of gasoline fuels, and their hydrogen abstraction reactions are crucial in the consumption pathways of combustion processes. In existing models, rate constants for these reactions are commonly derived by estimation, which can introduce large uncertainties into models and lead to prediction deviations. In this study, the hydrogen abstraction reactions of three xylene isomers (p-xylene, m-xylene, and o-xylene) with hydrogen and hydroxyl radicals were investigated using quantum chemical methods. The high-precision CBS-QB3 method was used to perform a series of calculations, including structure optimization, frequency analysis, and energy calculations. Rate constants for all reactions were obtained using transition state theory with tunneling corrections and fitted to the three-parameter Arrhenius expression. The kinetic parameters of these reactions were updated in existing models of xylene. The integration of the updated rate constants into combustion models generally improves predictive accuracy, particularly for ignition delay times, CO₂ formation, and laminar flame speeds, although discrepancies remain for some species such as CO. Full article

(This article belongs to the Special Issue Alternative Fuel and Clean Combustion)

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18 pages, 5127 KB

Open AccessArticle

Design of Two-Degree-of-Freedom PID Controllers Optimized by Bee Algorithm for Frequency Control in Renewable Energy Systems

by Sarawoot Boonkirdram, Sitthisak Audomsi, Worawat Sa-Ngiamvibool and Wassana Kasemsin

Energies 2025, 18(18), 4880; https://doi.org/10.3390/en18184880 (registering DOI) - 13 Sep 2025

Abstract

The increasing incorporation of renewable energy sources, such as photovoltaic and wind power, results in considerable variability and uncertainty within modern power systems, thereby complicating load frequency control. Conventional controllers, including PI and PID, often fail to provide sufficient performance in dynamic conditions. [...] Read more.

The increasing incorporation of renewable energy sources, such as photovoltaic and wind power, results in considerable variability and uncertainty within modern power systems, thereby complicating load frequency control. Conventional controllers, including PI and PID, often fail to provide sufficient performance in dynamic conditions. This study introduces a Two-Degree-of-Freedom PID (2DOF-PID) controller optimized through the Bee Algorithm (BA) for Load Frequency Control (LFC) in a two-area interconnected power system that includes renewable energy sources. The BA is employed to enhance controller parameters according to two objective functions: the Integral of Time-weighted Absolute Error (ITAE) and the Integral of Time-weighted Squared Error (ITSE). Simulation studies utilizing MATLAB/Simulink are conducted to evaluate the comparative effectiveness of PI, PID, and 2DOF-PID controllers. The results demonstrate that the 2DOF-PID controller consistently outperforms conventional PI and PID controllers in terms of frequency stability. The ITAE optimization of the 2DOF-PID results in a reduction in the ITAE index by more than 95% compared to PI and PID controllers, a decrease in settling time by approximately 40–60%, and a near elimination of overshoot and undershoot. Through ITSE optimization, the 2DOF-PID achieves an error reduction exceeding 90% and ensures smooth convergence with minimal oscillations. The PID controller has slightly improved effectiveness in minimizing tie-line power deviation, whereas the 2DOF-PID demonstrates greater resilience and damping capability in frequency regulation across both regions. The findings confirm that the Bee Algorithm-tuned 2DOF-PID controller serves as a robust and effective approach for frequency management in systems primarily reliant on renewable energy sources. Future research should incorporate multi-objective optimization algorithms that concurrently address frequency and tie-line power variations, thereby providing a more equitable control framework for practical Automatic Generation Control (AGC) operations. Full article

(This article belongs to the Special Issue Modeling, Simulation and Optimization of Power Systems: 2nd Edition)

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42 pages, 11496 KB

Open AccessArticle

Research on Energy Management Strategy for Marine Methanol–Electric Hybrid Propulsion System Based on DP-ANFIS Algorithm

by Zhao Li, Wuqiang Long, Wenliang Lu and Hua Tian

Energies 2025, 18(18), 4879; https://doi.org/10.3390/en18184879 (registering DOI) - 13 Sep 2025

Abstract

To address the challenges of high fuel consumption and emissions in traditional diesel-powered inland law enforcement vessels, this study proposes a methanol–electric hybrid propulsion system retrofitted with a novel energy management strategy (EMS) based on the integration of Dynamic Programming (DP) and Adaptive [...] Read more.

To address the challenges of high fuel consumption and emissions in traditional diesel-powered inland law enforcement vessels, this study proposes a methanol–electric hybrid propulsion system retrofitted with a novel energy management strategy (EMS) based on the integration of Dynamic Programming (DP) and Adaptive Neuro-Fuzzy Inference System (ANFIS). The DP-ANFIS algorithm combines the global optimization capability of DP with the real-time adaptability of ANFIS to achieve efficient power distribution. A high-fidelity simulation model of the hybrid system was developed using methanol engine bench test data and integrated with models of other powertrain components. The DP algorithm was used offline to generate an optimal control sequence, which was then learned online by ANFIS to enable real-time energy allocation. Simulation results demonstrate that the DP-ANFIS strategy reduces total energy consumption by 78.53%, increases battery state of charge (SOC) by 3.24%, decreases methanol consumption by 64.95%, and significantly reduces emissions of CO, HC, NOx, and CO₂ compared to a rule-based strategy. Hardware-in-the-loop tests confirm the practical feasibility of the proposed approach, offering a promising solution for intelligent energy management in marine hybrid propulsion systems. Full article

(This article belongs to the Topic Intelligent and Flexible Energy Management Strategies (EMSs) and Technologies)

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13 pages, 1543 KB

Open AccessArticle

Research on Hydrogen Production by Electrochemical Decomposition of HI_x Solution

by Yuhang An, Xiaofei Li, Jingxin Zeng, Xue Sun, Yuanyuan Duan and Qiang Song

Energies 2025, 18(18), 4878; https://doi.org/10.3390/en18184878 (registering DOI) - 13 Sep 2025

Abstract

The electrochemical decomposition of HI_x solution presents a promising alternative to overcome the challenges associated with HI thermal decomposition in the sulfur–iodine (S-I) cycle. In this study, constant current electrolysis and LSV tests were carried out for HI_x solution using an [...] Read more.

The electrochemical decomposition of HI_x solution presents a promising alternative to overcome the challenges associated with HI thermal decomposition in the sulfur–iodine (S-I) cycle. In this study, constant current electrolysis and LSV tests were carried out for HI_x solution using an H-type electrolyzer at different current densities and anode solution compositions. The results showed that during the process of HI electrolysis, the dominant factor of voltage variation gradually changed from electrochemical polarization to ohmic polarization as the current density increased. When the I₂ concentration in the HI solution approached saturation, a voltage step occurred in the constant current electrolysis, reaching a maximum amplitude of 127.69%. The analysis indicated that the voltage step was related to the I₂ deposition on the electrode and PEM, which led to the simultaneous increase in activation polarization and ohmic polarization overpotential. The increase in I₂ concentration decreased the limiting diffusion current density; I₂ supersaturation led to the formation of an insoluble iodine film on the electrode surface, ultimately terminating the electrochemical reaction. This study provides guidance for the development of HI_x solution electrolysis technology for hydrogen production. Full article

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25 pages, 29369 KB

Open AccessArticle

Assessment of a Cost-Effective Multi-Fidelity Conjugate Heat Transfer Approach for Metal Temperature Prediction of DLN Gas Turbine Combustor Liners

by Gianmarco Lemmi, Stefano Gori, Giovanni Riccio and Antonio Andreini

Energies 2025, 18(18), 4877; https://doi.org/10.3390/en18184877 (registering DOI) - 13 Sep 2025

Abstract

Over the last decades, Computational Fluid Dynamics (CFD) has become a fundamental tool for the design of gas turbine combustors, partly making up for the costs and duration issues related to the experimental tests involving high-pressure reactive processes. Nevertheless, high-fidelity simulations of reactive [...] Read more.

Over the last decades, Computational Fluid Dynamics (CFD) has become a fundamental tool for the design of gas turbine combustors, partly making up for the costs and duration issues related to the experimental tests involving high-pressure reactive processes. Nevertheless, high-fidelity simulations of reactive flows remain computationally expensive, particularly for conjugate heat transfer (CHT) analyses aimed at predicting liner metal temperatures and characterising wall heat losses. This work investigates the robustness of a cost-effective numerical setup for CHT simulations, focusing on the prediction of cold-side thermal loads in industrial combustor liners under realistic operating conditions. The proposed approach is tested using both Reynolds-Averaged Navier–Stokes (RANS) and unsteady Stress-Blended Eddy Simulation (SBES) turbulence models for the combustor flame tube, coupled via a time desynchronisation strategy with transient heat conduction in the solid domain. Cold-side heat transfer is modelled using a 1D correlation-based tool, runtime coupled with the CHT simulation to account for cooling-induced thermal loads without explicitly resolving complex cooling passages. The methodology is applied to a single periodic sector of the NovaLT^TM16 annular combustor, developed by Baker Hughes and operating under high-pressure conditions with natural gas. Validation against experimental data demonstrates the methodology’s ability to predict liner metal temperatures accurately, account for modifications in cooling geometries, and support design-phase evaluations efficiently. Overall, the proposed approach offers a robust trade-off between computational cost and predictive accuracy, making it suitable for practical engineering applications. Full article

(This article belongs to the Special Issue Recent Advances in Fluid Machinery, Energy Systems and Power Generation)

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19 pages, 1287 KB

Open AccessArticle

The Assessment of Anaerobic Digestion Performance and Efficiency in Terms of Waste Collection

by Przemysław Seruga, Marta Wilk, Edmund Cibis, Agnieszka Urbanowska and Łukasz Niedźwiecki

Energies 2025, 18(18), 4876; https://doi.org/10.3390/en18184876 (registering DOI) - 13 Sep 2025

Abstract

Municipal solid waste (MSW) management is identified as a significant sustainability concern. Source segregation (SS) is the most effective method of managing MSW, and anaerobic digestion (AD) is the most efficient treatment method. The aim of this study was to analyze the impact [...] Read more.

Municipal solid waste (MSW) management is identified as a significant sustainability concern. Source segregation (SS) is the most effective method of managing MSW, and anaerobic digestion (AD) is the most efficient treatment method. The aim of this study was to analyze the impact of waste collection rules on the efficiency and performance of AD. The potential biomethane yields for SS-kitchen waste and SS-biowaste were calculated, determined in laboratory tests, and verified full-scale. The content of the organic fraction in SS-biowaste reached about 81 to 86%; however, regarding SS-kitchen waste, it reached almost 92%. The primary contaminants were plastics. The obtained biogas yield was slightly higher for SS-kitchen waste (136.2 m³/ton), compared to SS-biowaste (116.6 m³/ton). The pH values, acidity, and alkalinity indicated no risk of exploitation using both feedstocks. However, in the case of SS-kitchen waste, the acetic acid content was about 2.5 times higher than that of SS-biowaste. Furthermore, the acetic acid was noted in the outlet section (about 140–160 mg/kg), indicating no complete organic matter decomposition. Regarding SS-kitchen waste, the calculated methane yield reached 137.1 m³_CH4/ton and laboratory tests showed a methanogenic potential of 129.7 m³_CH4/ton, while at full-scale, it reached about 82.2 m³_CH₄/ton. The research confirmed that the SS of biowaste positively impacts MSW management by improving waste composition and increasing recycling possibilities. AD is an effective biowaste treatment process, allowing energy recovery from waste. Full article

(This article belongs to the Special Issue Biomass and Waste Valorization for Biofuel and Bioproducts Production)

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17 pages, 3096 KB

Open AccessArticle

Impedance-Based Criterion Design for Grid-Following/Grid-Forming Switching Control of Wind Generation System

by Sijia Huang, Zhenbin Zhang, Zhihao Chen, Huimin Huang and Zhen Li

Energies 2025, 18(18), 4875; https://doi.org/10.3390/en18184875 (registering DOI) - 13 Sep 2025

Abstract

As wind farms connect with power grids via long-distance transmission lines and multiple transformers, the resulting networks exhibit inherently weak and fluctuating grid strength—subject to dynamic variations from external disturbances like generation tripping; thus, ensuring stable operation presents a critical challenge. To address [...] Read more.

As wind farms connect with power grids via long-distance transmission lines and multiple transformers, the resulting networks exhibit inherently weak and fluctuating grid strength—subject to dynamic variations from external disturbances like generation tripping; thus, ensuring stable operation presents a critical challenge. To address this issue, grid-following/grid-forming mode switching has emerged as a strategic approach, where wind turbine generators strategically switch between grid-following control in strong grids and grid-forming control in weak grids. This paper proposes an impedance-based switching criteria design methodology, ensuring system stability under dynamic grid strength variations. Leveraging sequence impedance analysis in frequency domain, we establish a stability boundary for mode transitions. Simulation results demonstrate that the proposed criteria maintain stable operation, enhancing robustness against grid strength fluctuations. Full article

(This article belongs to the Special Issue Advances in Wind Turbine Optimization and Control)

20 pages, 1394 KB

Open AccessArticle

A Bidding Strategy for Virtual Power Plants in the Day-Ahead Market

by Yueping Kong, Yuqin Chen, Jiao Du, Yongbiao Yang and Qingshan Xu

Energies 2025, 18(18), 4874; https://doi.org/10.3390/en18184874 (registering DOI) - 13 Sep 2025

Abstract

Under the context of rapid distributed energy development and ongoing electricity market reforms, this paper investigates bidding strategies for virtual power plants (VPPs) formed by aggregated distributed renewable energy (DRE) in China’s evolving day-ahead electricity market. To address privacy concerns of DRE participants [...] Read more.

Under the context of rapid distributed energy development and ongoing electricity market reforms, this paper investigates bidding strategies for virtual power plants (VPPs) formed by aggregated distributed renewable energy (DRE) in China’s evolving day-ahead electricity market. To address privacy concerns of DRE participants and VPP aggregators during dynamic aggregation, an enhanced Benders decomposition framework is proposed. The methodology first characterizes market uncertainties (e.g., electricity prices and renewable generation output) by clustering them into representative scenarios using K-medoids clustering. A privacy-preserving decentralized optimization model is then formulated: the VPP aggregator solves a master problem to determine bidding decisions, while DRE units independently address subproblems via privacy-protected mathematical constraints that avoid revealing explicit operational details. The framework ensures secure information exchange and computational efficiency. Case studies demonstrate that the proposed model effectively balances privacy protection and bidding performance, outperforming traditional centralized optimization approaches in terms of solution quality and scalability. Full article

(This article belongs to the Special Issue Operation and Control of Distributed Power Resources Under Market Environment)

27 pages, 3428 KB

Open AccessArticle

Synthesis of an Electric Arc Furnace Electrode Movement Control System Based on Feedback Linearization with PI or PI^μ Controllers

by Andriy Lozynskyy, Jacek Kozyra, Andriy Kutsyk, Zbigniew Łukasik, Aldona Kuśmińska-Fijałkowska and Lidiia Kasha

Energies 2025, 18(18), 4873; https://doi.org/10.3390/en18184873 (registering DOI) - 13 Sep 2025

Abstract

An approach is proposed for the synthesis of the control system for the electrode movement of an arc steelmaking furnace based on a combination of the feedback linearization method and a traditional PI controller. The application of fractional PI^μ controllers in such [...] Read more.

An approach is proposed for the synthesis of the control system for the electrode movement of an arc steelmaking furnace based on a combination of the feedback linearization method and a traditional PI controller. The application of fractional PI^μ controllers in such a control system using the Caputo–Fabrizio representation for their description is analyzed. The use of such controllers provides transient characteristics ranging from those of a modal control system to the characteristics of a system with a classical PI controller that was developed using feedback linearization. The comparison between proposed controllers is conducted by the ISE and ITAE indexes. The effectiveness of the synthesized control systems is demonstrated by research results using both single-phase and three-phase models of the electrode movement system in an arc steelmaking furnace. Full article

14 pages, 1301 KB

Open AccessArticle

Study of Long-Distance Belt Conveying for Underground Copper Mines

by Natalia Suchorab-Matuszewska, Witold Kawalec and Robert Król

Energies 2025, 18(18), 4872; https://doi.org/10.3390/en18184872 (registering DOI) - 13 Sep 2025

Abstract

Efficient material handling is critical for mining productivity, safety energy and cost control. This paper analyzes the energy efficiency of five alternative designs for a 3 km inclined underground conveyor system for copper ore transport, considering route geometry, belt specifications, drive configurations, and [...] Read more.

Efficient material handling is critical for mining productivity, safety energy and cost control. This paper analyzes the energy efficiency of five alternative designs for a 3 km inclined underground conveyor system for copper ore transport, considering route geometry, belt specifications, drive configurations, and operational parameters. Two main design approaches were examined: a single long conveyor and two shorter conveyors. Variants differed in belt tensile strength, the use of intermediate drives, and system layout. Calculations results achieved by using dedicated QNK-TT software (version 4.45.21.08.10.18.11) show differences in the specific energy consumption index between variants for both average and peak capacities and highlight that high-capacity performance requires non-standard solutions: either higher belt strength or an intermediate drive system. The study shows that conveyor energy efficiency depends strongly on load level, with near-maximum throughput yielding the best performance. The authors conclude that conveyor system component selection should be based on a multi-criteria evaluation—including the capacity margin, operational safety and maintenance complexity—rather than energy efficiency alone. Full article

(This article belongs to the Special Issue Energy Consumption at Production Stages in Mining, 2nd Edition)

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22 pages, 3352 KB

Open AccessArticle

Empirical Assessment of Passive Thermal Resilience in Buildings with Varying Heat Storage Capacity During Heatwaves and Power Outages

by Marta Gortych, Anna Staszczuk and Tadeusz Kuczyński

Energies 2025, 18(18), 4871; https://doi.org/10.3390/en18184871 (registering DOI) - 13 Sep 2025

Abstract

This study evaluates the passive thermal resilience of two full-scale residential buildings during natural summer heatwaves and blackout-like conditions in a temperate European climate. The buildings share identical geometry and ventilation but differ in envelope mass and ground coupling. Building B1 is a [...] Read more.

This study evaluates the passive thermal resilience of two full-scale residential buildings during natural summer heatwaves and blackout-like conditions in a temperate European climate. The buildings share identical geometry and ventilation but differ in envelope mass and ground coupling. Building B1 is a masonry structure with a slab-on-ground floor, while B2 is a lightweight timber-frame house. In 2019, B1 underwent a retrofit in which floor insulation was removed to enable direct subsoil heat exchange. Three complementary frameworks were applied: model IOD, AWD, OEF, the indicators AF and αIOD, and the health-based scenario rating HE, HIHH, and WBGT. Across all metrics, B1 demonstrated superior resilience, with overheating fully eliminated after ground coupling was introduced. B2, in contrast, remained vulnerable under both moderate and extreme events. The findings highlight the critical role of thermal mass and soil buffering in maintaining safe indoor conditions without active systems. Under certain circumstances, omitting under-slab insulation can improve summer resilience without significantly compromising winter performance. A companion life-cycle analysis confirms lower cumulative carbon emissions for B1 under all SSP scenarios to 2100. Passive ground coupling thus emerges as a low-cost, maintenance-free adaptation strategy with co-benefits for mitigation and occupant safety. Full article

15 pages, 1775 KB

Open AccessArticle

Design of a Hybrid Wind and Micro-Hydro System for Sustainable Water Treatment

by Hesamaddin Emamipour, Mohammad Javad Eshghi and Ashraf Ali Khan

Energies 2025, 18(18), 4870; https://doi.org/10.3390/en18184870 (registering DOI) - 13 Sep 2025

Abstract

Newfoundland and Labrador have strong wind and water resources, making hybrid renewable energy systems an important option for the region. This paper presents the design and simulation of a system that combines wind turbines and micro-hydro power to deliver clean electricity for water [...] Read more.

Newfoundland and Labrador have strong wind and water resources, making hybrid renewable energy systems an important option for the region. This paper presents the design and simulation of a system that combines wind turbines and micro-hydro power to deliver clean electricity for water treatment in remote communities. Many isolated areas still rely on diesel and other conventional sources, which create environmental concerns. Using HOMER Pro 3.17.1 software, the system was modeled based on local climate and resource conditions. Results show that it can produce over 35,000 kWh per year, enough to power a standard water treatment unit serving more than 240 people. By integrating wind and hydro with battery storage, the system ensures stable operation and reduces dependence on fossil fuels. The environmental analysis confirms that it avoids over 9 tons of CO₂ emissions annually. The novelty of this work is its site-specific approach, showing how renewable energy can improve both energy security and water quality in remote Canadian communities while providing a model for sustainable rural development. Full article

(This article belongs to the Special Issue Development and Efficient Utilization of Renewable and Clean Energy)

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12 pages, 923 KB

Open AccessArticle

Industrial-Scale Development of Biogas Purification and Compression System

by Tarsisius Kristyadi, Meilinda Nurbanasari, Dani Rusirawan, Jono Suhartono, Lisa Kristiana, Pramuda Nugraha and Alfan Ekajati

Energies 2025, 18(18), 4869; https://doi.org/10.3390/en18184869 (registering DOI) - 13 Sep 2025

Abstract

The use of biogas in Indonesia, derived from livestock manure, palm oil waste, and organic waste, remains limited to household-scale applications due to its inefficiency in transportation and storage. This limitation arises from the presence of CO₂ and H₂O in [...] Read more.

The use of biogas in Indonesia, derived from livestock manure, palm oil waste, and organic waste, remains limited to household-scale applications due to its inefficiency in transportation and storage. This limitation arises from the presence of CO₂ and H₂O in raw biogas, which results in a lower methane content compared to natural gas. Furthermore, raw biogas is not suitable for storage in cylinders or long-distance distribution without purification. This research aims to address these challenges by developing biogas into Bio-Compressed Natural Gas (Bio-CNG), a high-methane-content fuel suitable for industrial applications and power generation. Bio-CNG is produced through biogas purification, primarily using the water scrubbing method, to achieve methane concentrations exceeding 92%, followed by compression to 120 Bar for compact storage and ease of transport. The study focuses on designing and testing an industrial-scale effective water scrubber system for biogas purification, thereby enabling the broader utilization of renewable biogas energy beyond local reactor sites. The development of the biogas purification and compression system begins with the system modeling and the detailed design, which are then followed by the hardware fabrication in industrial-scale scenarios. The purification and compression of biogas consist of two main components: the purification system and the biogas compression system. The core of the purification system is a scrubber, designed as a vertical column measuring 6 m in height and 0.5 m in diameter. The designed and fabricated system for industrial-scale biogas purification and compression was then tested. The results showed a linear correlation between scrubber operating pressure and methane and CO₂ content. Based on the results of the pressure and water flow rate variation tests, an operating pressure of 2 bar is recommended for the water scrubber, as this condition yielded the lowest specific energy consumption of 0.3 kWh/Nm³. Meanwhile, in the biogas compression system, the energy required is exponentially proportional to the pressure between 75 and 105 bar. Full article

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

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