Energies

19 pages, 2852 KiB

Open AccessArticle

Immunological AI Optimizer Deployment in a 330 MW Lignite-Fired Unit for NO_x Abatement

by Konrad Świrski, Łukasz Śladewski, Konrad Wojdan and Xianyong Peng

Energies 2025, 18(12), 3032; https://doi.org/10.3390/en18123032 (registering DOI) - 7 Jun 2025

This study presents an advanced NO_x reduction strategy for a 330 MW lignite-fired boiler using an immunological AI system: the SILO (Stochastic Immune Layer Optimizer) combustion optimizer inspired by artificial immune systems. The immunological AI optimizer adaptively models multi-variable interactions and fireball [...] Read more.

This study presents an advanced NO_x reduction strategy for a 330 MW lignite-fired boiler using an immunological AI system: the SILO (Stochastic Immune Layer Optimizer) combustion optimizer inspired by artificial immune systems. The immunological AI optimizer adaptively models multi-variable interactions and fireball shape in real time, optimizing fuel–air mixing to reduce NO_x formation at the source. Unlike reactive secondary methods, the combustion optimizer reshapes the combustion process to reduce emissions while improving efficiency. Real-time temperature data from the AGAM acoustic system inform the combustion optimizer’s fireball modeling, ensuring combustion uniformity. A urea-based SNCR system serves as a secondary layer, controlled based on local furnace conditions to target thermal zones. Field results confirmed that SILO reduced NO_x emissions below 200 mg/Nm³, decreased urea consumption by up to 34%, and improved boiler efficiency by 0.29%. The architecture offers a scalable, DCS-integrated solution for aligning fossil-fueled operations with tightening emission standards. Full article

(This article belongs to the Special Issue Advanced Clean Coal Technology)

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22 pages, 3041 KiB

Open AccessArticle

Development of Recurrent Neural Networks for Thermal/Electrical Analysis of Non-Residential Buildings Based on Energy Consumptions Data

by Elisa Belloni, Flavia Forconi, Gabriele Maria Lozito, Martina Palermo, Michele Quercio and Francesco Riganti Fulginei

Energies 2025, 18(12), 3031; https://doi.org/10.3390/en18123031 (registering DOI) - 7 Jun 2025

Abstract

Extensive research has focused on optimizing energy consumption in residential buildings based on indoor thermal conditions. However, modeling the energy and thermal behavior of non-residential buildings presents greater challenges due to their complex geometries and the high computational cost of detailed simulations. Simplifying [...] Read more.

Extensive research has focused on optimizing energy consumption in residential buildings based on indoor thermal conditions. However, modeling the energy and thermal behavior of non-residential buildings presents greater challenges due to their complex geometries and the high computational cost of detailed simulations. Simplifying input variables can enhance the applicability of artificial intelligence techniques in predicting energy and thermal performance. This study proposes a neural network-based approach to characterize the thermal–energy relationship in commercial buildings, aiming to provide an efficient and scalable solution for performance prediction. Consumptions trends for a building are generated using the EnergyPlus™ dynamic simulation software over a timespan of a year in different locations, and the data are then used to train neural network models. Uncertainty analyses are carried out to evaluate the behavior effectiveness of the artificial neural networks (ANNs) in different weather conditions, and the root mean square error (RMSE) is calculated in terms of mean air temperatures. The results show that this approach can reproduce the functional relationship between input and output data. Three different ANNs are trained for the northern, central, and southern climatic zones of Italy. The southern region’s models achieved the highest accuracy, with an RMSE below 0.5 °C; whereas the model for the northern cities was less accurate, since no specific trend in plant management was present, but it still achieved an acceptable accuracy of 1.0 °C. This approach is computationally lightweight; inference time is below 5 ms, and can be easily embedded in optimization algorithms for load dispatch or in microcontroller applications for building automation systems. Full article

(This article belongs to the Special Issue Environmental Sustainability and Energy Economy)

24 pages, 4942 KiB

Open AccessArticle

Two-Stage Robust Optimization Model for Flexible Response of Micro-Energy Grid Clusters to Host Utility Grid

by Hongkai Zhang, Outing Zhang, Peng Li, Xianyu Yue and Zhongfu Tan

Energies 2025, 18(12), 3030; https://doi.org/10.3390/en18123030 (registering DOI) - 7 Jun 2025

Abstract

As a decentralized energy management paradigm, micro-energy grid (MEG) clusters enable synergistic operation of heterogeneous distributed energy assets, particularly through multi-energy vector coupling mechanisms that enhance distributed energy resource (DER) utilization efficiency in next-generation power networks. While individual MEGs demonstrate limited capability in [...] Read more.

As a decentralized energy management paradigm, micro-energy grid (MEG) clusters enable synergistic operation of heterogeneous distributed energy assets, particularly through multi-energy vector coupling mechanisms that enhance distributed energy resource (DER) utilization efficiency in next-generation power networks. While individual MEGs demonstrate limited capability in responding to upper-grid demands using surplus energy after fulfilling local supply/demand balance, coordinated cluster operation significantly enhances system-wide flexibility. This paper proposes a two-stage robust optimization model that systematically addresses both the synergistic complementarity of multi-MEG systems and renewable energy uncertainty. First, the basic operation structure of MEG, including distributed generation, cogeneration units, and other devices, is established, and the operation mode of the MEG cluster responding to host utility grid flexibly is proposed. Then, aiming to reduce operation expenses, an optimal self-scheduling plan is generated by establishing a MEG scheduling optimization model; on this basis, the flexibility response capability of the MEG is measured. Finally, to tackle the uncertainty issue of wind and photovoltaic power generation, the two-stage robust theory is employed, and the scheduling optimization model of MEG cluster flexibility response to the host utility grid is constructed. A southern MEG cluster is chosen for simulation to test the model and method’s effectiveness. Results indicate that the MEG cluster’s flexible response mechanism can utilize individual MEGs’ excess power generation to meet the host utility grid’s dispatching needs, thereby significantly lowering the host utility grid’s dispatching costs. Full article

(This article belongs to the Topic Intelligent, Flexible, and Effective Operation of Smart Grids with Novel Energy Technologies and Equipment)

23 pages, 4810 KiB

Open AccessArticle

Construction of Microclimatic Zone Based on Convection–Radiation System for Local Cooling in Deep Mines

by Xiangru Chen, Xiaodong Wang and Hui Wang

Energies 2025, 18(12), 3029; https://doi.org/10.3390/en18123029 (registering DOI) - 7 Jun 2025

Abstract

As global mineral resources at shallow depths continue to deplete, thermal hazards have emerged as a critical challenge in deep mining operations. Conventional localized cooling systems suffer from a fundamental inefficiency where their cooling capacity is rapidly dissipated by the main ventilation airstream. [...] Read more.

As global mineral resources at shallow depths continue to deplete, thermal hazards have emerged as a critical challenge in deep mining operations. Conventional localized cooling systems suffer from a fundamental inefficiency where their cooling capacity is rapidly dissipated by the main ventilation airstream. This study introduces the innovative concept of a “microclimatic circulation zone” implemented through a convection–radiation cooling system. The design incorporates a synergistic arrangement of dual fans and flow-guiding baffles that creates a semi-enclosed air circulation field surrounding the modular convection–radiation cooling apparatus, effectively preventing cooling capacity loss to the primary ventilation flow. The research develops comprehensive theoretical models characterizing both internal and external heat transfer mechanisms of the modular convection–radiation cooling system. Using Fluent computational fluid dynamics software, we constructed an integrated heat–moisture–flow coupled numerical model that identified optimal operating parameters: refrigerant velocity of 0.2 m/s, inlet airflow velocity of 0.45 m/s, and outlet aperture height of 70 mm. Performance evaluation conducted at a mining operation in Yunnan Province utilized the Wet Bulb Globe Temperature (WBGT) index as the assessment criterion. Results demonstrate that the enhanced microclimatic circulation system exhibits superior cooling retention capabilities, with a 19.83% increase in refrigeration power and merely 3% cooling capacity dissipation at a 7 m distance, compared to 19.23% in the conventional system. Thermal field analysis confirms that the improved configuration successfully establishes a stable microclimatic circulation zone with significantly more concentrated low-temperature regions. This effectively addresses the principal limitation of conventional systems where conditioned air is readily dispersed by the main ventilation current. The approach presented offers a novel technological pathway for localized thermal environment management in deep mining operations affected by heat stress conditions. Full article

(This article belongs to the Special Issue Application of Renewable Energy Sources (Solar, Geothermal, Wind, Biomass and Hydro Energies) in Buildings, 2nd Edition)

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16 pages, 2298 KiB

Open AccessArticle

Combustion Characteristics of Municipal Solid Waste in a Grate-Fired Solid-Fuel Hot Water Boiler

by Dias Raybekovich Umyshev, Andrey Anatoliyevich Kibarin, Aiganym Bulatkyzy Seidaliyeva, Dilshat Ozatuly Iskakov, Yeldos Lesbekovich Zhekenov, Ilyas Kermyly Jambayev and Madina Maratovna Umysheva

Energies 2025, 18(12), 3028; https://doi.org/10.3390/en18123028 (registering DOI) - 7 Jun 2025

Abstract

Currently, ecological energy production is one of the most pressing issues in power engineering. In addition, environmental pollution caused by various emissions and the challenge of waste disposal remain significant global concerns. One potential solution to these problems is the conversion of waste [...] Read more.

Currently, ecological energy production is one of the most pressing issues in power engineering. In addition, environmental pollution caused by various emissions and the challenge of waste disposal remain significant global concerns. One potential solution to these problems is the conversion of waste into useful energy through combustion. In this study, experimental investigations were carried out on the combustion of municipal solid waste (MSW) in a grate furnace of a 400 kW hot water boiler. The experiments included the combustion of both MSW and traditional brown coal. Data were collected on the concentrations of various substances in the exhaust gases, and thermal imaging was performed to assess heat losses from the boiler surface. When burning waste compared to coal, SO₂ concentrations were significantly lower, ranging from 3.43 to 4.3 ppm, whereas for coal they reached up to 122 ppm. NO_X concentrations during MSW combustion peaked at 106 ppm, while for coal combustion they reached 67.5 ppm. A notable increase in CO concentration was observed during the initial phase of coal combustion, with levels reaching up to 2510 ppm. The thermal efficiency of the boiler plant reached 84.4% when burning waste and 87% when burning brown coal. Full article

(This article belongs to the Special Issue Clean Use of Fuels: Future Trends and Challenges)

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23 pages, 1497 KiB

Open AccessArticle

Thermodynamic-Based Perceived Predictive Power Control for Renewable Energy Penetrated Resident Microgrids

by Wenhui Shi, Lifei Ma, Wenxin Li, Yankai Zhu, Dongliang Nan and Yinzhang Peng

Energies 2025, 18(12), 3027; https://doi.org/10.3390/en18123027 - 6 Jun 2025

Abstract

Heating, ventilation, and air conditioning (HVAC) systems and microgrids have garnered significant attention in recent research, with temperature control and renewable energy integration emerging as key focus areas in urban distribution power systems. This paper proposes a robust predictive temperature control (RPTC) method [...] Read more.

Heating, ventilation, and air conditioning (HVAC) systems and microgrids have garnered significant attention in recent research, with temperature control and renewable energy integration emerging as key focus areas in urban distribution power systems. This paper proposes a robust predictive temperature control (RPTC) method and a microgrid control strategy incorporating asymmetrical challenges, including uneven power load distribution and uncertainties in renewable outputs. The proposed method leverages a thermodynamics-based R-C model to achieve precise indoor temperature regulation under external disturbances, while a multisource disturbance compensation mechanism enhances system robustness. Additionally, an HVAC load control model is developed to enable real-time dynamic regulation of airflow, facilitating second-level load response and improved renewable energy accommodation. A symmetrical power tracking and voltage support secondary controller is also designed to accurately capture and manage the fluctuating power demands of HVAC systems for supporting operations of distribution power systems. The effectiveness of the proposed method is validated through power electronics simulations in the Matlab/Simulink/SimPowerSystems environment, demonstrating its practical applicability and superior performance. Full article

(This article belongs to the Special Issue Digital Modeling, Operation and Control of Sustainable Energy Systems)

27 pages, 1763 KiB

Open AccessArticle

The Concept of an Infrastructure Location to Supply Buses with Hydrogen: A Case Study of the West Pomeranian Voivodeship in Poland

by Ludmiła Filina-Dawidowicz, Dawid Miłek and Dalia Baziukė

Energies 2025, 18(12), 3026; https://doi.org/10.3390/en18123026 - 6 Jun 2025

Abstract

The growing energy crisis and increasing threat of climate change are driving the need to take action regarding the use of alternative fuels in transport, including public transport. Hydrogen is undoubtedly a fuel which is environmentally friendly and constitutes an alternative to fossil [...] Read more.

The growing energy crisis and increasing threat of climate change are driving the need to take action regarding the use of alternative fuels in transport, including public transport. Hydrogen is undoubtedly a fuel which is environmentally friendly and constitutes an alternative to fossil fuels. The wider deployment of hydrogen-powered vehicles involves the need to adapt infrastructure to support the operation of these vehicles. Such infrastructure includes refuelling stations for hydrogen-powered vehicles. The widespread use of hydrogen-powered vehicles is dependent on the development of a network of hydrogen refuelling stations. The aim of this article is to propose the conceptual location of infrastructure for fuelling public transport vehicles with hydrogen in selected cities of the West Pomeranian Voivodeship, in particular the cities of Szczecin and Koszalin. The methodology used to determine the number of refuelling stations is described, and the concept of the location for the refuelling stations has been proposed. Based on a set assumptions, it was stated that two stations may be located in the Voivodeship in 2025 and seven stations in 2040. The research results will be of interest to infrastructure developers, public transport companies, and municipalities involved in making decisions related to the purchase and operation of hydrogen-powered buses. Full article

(This article belongs to the Special Issue Life Cycle and Costs Assessment for a New Generation Low-Impact Transport Sector)

25 pages, 1584 KiB

Open AccessArticle

Research on Energy-Saving Optimization Control Strategy for Distributed Hub Motor-Driven Vehicles

by Bin Huang, Jinyu Wei, Minrui Ma and Xu Yang

Energies 2025, 18(12), 3025; https://doi.org/10.3390/en18123025 - 6 Jun 2025

Abstract

Aiming at the problems of energy utilization efficiency and braking stability in electric vehicles, a high-efficiency and energy-saving control strategy that takes both driving and braking into account is proposed with the distributed hub motor-driven vehicle as the research object. Under regular driving [...] Read more.

Aiming at the problems of energy utilization efficiency and braking stability in electric vehicles, a high-efficiency and energy-saving control strategy that takes both driving and braking into account is proposed with the distributed hub motor-driven vehicle as the research object. Under regular driving and braking conditions, the front and rear axle torque distribution coefficients are optimized by an adaptive particle swarm algorithm based on simulated annealing and a multi-objective co-optimization strategy based on variable weight coefficients, respectively. During emergency braking, the anti-lock braking strategy (ABS) based on sliding mode control realizes the independent distribution of torque among four wheels. The joint simulation verification based on MATLAB R2023a/Simulink-Carsim 2020.0 shows that under World Light Vehicle Test Cycle (WLTC) conditions, the optimization strategy reduces the driving energy consumption by 3.20% and 2.00%, respectively, compared with the average allocation and the traditional strategy. The braking recovery energy increases by 4.07% compared with the fixed proportion allocation, improving the energy utilization rate of the entire vehicle. The wheel slip rate can be quickly stabilized near the optimal value during emergency braking under different adhesion coefficients, which ensures the braking stability of the vehicle. The effectiveness of the strategy is verified. Full article

(This article belongs to the Special Issue Research on Intelligent Operation and Maintenance and Key Technology of New Energy Vehicles)

27 pages, 3963 KiB

Open AccessArticle

Quantitative Estimation of Type Selection of Underground Lined Rock Caverns for Compressed Air Energy Storage Based on Numerical Simulations

by Hong Ke, Yingchuan Ma, Yue Xiang, Xinjin Wang, Yutao Hu, Zhuo Ma and Guohua Zhang

Energies 2025, 18(12), 3024; https://doi.org/10.3390/en18123024 - 6 Jun 2025

Abstract

Selecting the type of lined rock cavern (LRC) is a critical aspect in the construction of compressed air energy storage (CAES) plants. Present research on CAES has mainly focused on site selection, sealing performance, and stability of underground LRCs. Insufficient attention has been [...] Read more.

Selecting the type of lined rock cavern (LRC) is a critical aspect in the construction of compressed air energy storage (CAES) plants. Present research on CAES has mainly focused on site selection, sealing performance, and stability of underground LRCs. Insufficient attention has been given to the selection of LRC type, which is a prerequisite for further detailed analyses of LRCs. To overcome this limitation, based on reliable numerical simulation, in this study, we simulate the mechanical responses of two popular types of LRCs: tunnel-type and silo-type LRCs. Parameter sensitivity analysis is then conducted based on the mechanical response, including parameters such as the deformation modulus of the surrounding rock mass, Poisson’s ratio, cohesion, friction angle, crustal stress, and lateral stress coefficient. Based on the simulated results, the analytical hierarchy process (AHP) method is used to propose scoring systems for the two types of LRCs. This scoring system can be used for quantitative estimation of an appropriate LRC in CAES systems. Full article

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21 pages, 1545 KiB

Open AccessArticle

The Impact of Terminal-Voltage Control on the Equilibrium Points and Small-Signal Stability of GFL-VSC Systems

by Shun Li, Xing Yao, Cong Fu, Meng Zhan and Bo Bao

Energies 2025, 18(12), 3023; https://doi.org/10.3390/en18123023 - 6 Jun 2025

Abstract

Weak grid stability is crucial for grid-following voltage source converter (GFL-VSC) systems. Current studies primarily focus on the interaction analyses between active-power loops, whereas the influence of reactive-power loops remains unclear. To address this problem, this study focuses on terminal-voltage control (TVC) and [...] Read more.

Weak grid stability is crucial for grid-following voltage source converter (GFL-VSC) systems. Current studies primarily focus on the interaction analyses between active-power loops, whereas the influence of reactive-power loops remains unclear. To address this problem, this study focuses on terminal-voltage control (TVC) and analyzes its impact on equilibrium points (EPs) and small-signal stability by varying the TVC response speed, including three different cases: considering TVC dynamics, considering TVC rapid responses, and considering TVC slow responses. Firstly, the models of the GFL-VSC system under different scenarios are established and compared. In the EP analysis, for both TVC dynamics and TVC rapid responses, the EP of an active current remains constant and it becomes unstable in a weak grid, whereas for TVC slow responses, the EP undergoes trans-critical bifurcation; specifically, the other EP becomes stable after this bifurcation. Further, in the small-signal stability analysis, three equivalent Heffron–Phillips models based on the phase-locked loop synchronization dynamics with additional synchronization and damping coefficients are constructed and studied. By these systematical studies, the impacts of different TVC response speeds are clarified and summarized, and these analytical results are well supported by MATLAB/Simulink simulations and hardware-in-the-loop experiments. Full article

20 pages, 2998 KiB

Open AccessArticle

Operational Environment Effects on Energy Consumption and Reliability in Mine Truck Haulage

by Przemysław Bodziony, Zbigniew Krysa and Michał Patyk

Energies 2025, 18(12), 3022; https://doi.org/10.3390/en18123022 - 6 Jun 2025

Abstract

This study investigates the factors influencing the energy consumption and reliability of haul trucks in open-pit mines and quarries, where fuel costs and the environmental impact are significant. Traditional analysis of haulage systems often overlooks crucial aspects such as energy efficiency in the [...] Read more.

This study investigates the factors influencing the energy consumption and reliability of haul trucks in open-pit mines and quarries, where fuel costs and the environmental impact are significant. Traditional analysis of haulage systems often overlooks crucial aspects such as energy efficiency in the specific mining environment and the effect of road configurations on truck performance. As sustainability becomes increasingly important, reducing fuel consumption not only reduces costs but also reduces greenhouse gas emissions. A key focus of the study is the link between haul truck reliability and overall efficiency. Frequent breakdowns increase maintenance costs, lead to unplanned downtime, and increase fuel consumption, all of which have an impact on the environment. Reliable transport systems, on the other hand, improve efficiency, reduce costs, and support sustainability goals. The authors analyze the energy consumption of trucks in relation to vehicle performance parameters and transport route characteristics. Discrete modeling of the transport system showed the impact of the operating environment on the variability of energy consumption and vehicle reliability. The study highlights the importance of understanding specific energy consumption in order to optimize the choice of transport system, as transport costs are a major cost of resource extraction. By analyzing the effect of road quality on vehicle performance, the authors suggest that improvements to the road surface can more easily improve vehicle reliability and energy intensity than changes to other road design elements. The study presents a quantitative analysis of the impact of haul road conditions on the operational efficiency of haul trucks in mining environments. Through discrete simulation models, two scenarios were analyzed. Total operational time decreased by 11.2% when road quality improved, demonstrating the critical role of surface maintenance. Additionally, breakdown times were reduced by 44%, maintenance by 15%, and empty travel by 9% in the optimized scenario. These findings underscore the necessity of maintaining optimal road conditions to prevent substantial efficiency losses and increased maintenance costs. Full article

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

15 pages, 977 KiB

Open AccessReview

Heat Exchanger Networks: Applications for Industrial Integrations

by Bahar Saeb Gilani and Tatiana Morosuk

Energies 2025, 18(12), 3021; https://doi.org/10.3390/en18123021 - 6 Jun 2025

Abstract

Heat integration is a crucial concept in process engineering and energy management. It refers to using heat exchangers and process modifications to maximize energy efficiency, lowering cost and/or carbon emissions within industrial processes through minimizing the external heating and cooling requirements (utility savings). [...] Read more.

Heat integration is a crucial concept in process engineering and energy management. It refers to using heat exchangers and process modifications to maximize energy efficiency, lowering cost and/or carbon emissions within industrial processes through minimizing the external heating and cooling requirements (utility savings). There are two key aspects of heat integration. “Heat Exchanger Network” is an approach to designing efficient connections among the heat exchangers to transfer heat between several hot and cold streams. “Pinch Analysis” is a systematic methodology that determines the optimal energy recovery by identifying the “pinch point” to maximize heat recovery. The paper aims to review the actual status of research in the field of application of heat exchanger networks for industrial integrations and highlight the perspectives. Full article

(This article belongs to the Section J: Thermal Management)

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1 pages, 111 KiB

Open AccessCorrection

Correction: Haiyun et al. Accurate Location Method for Abnormal Line Losses in Distribution Network Considering Topology Matching and Parameter Estimation in Grid. Energies 2025, 18, 2324

by Haiyun An, Qian Zhou, Qiuwei Wu, Yufang Liu, Cheng Huang and Jiaxun Li

Energies 2025, 18(12), 3020; https://doi.org/10.3390/en18123020 - 6 Jun 2025

Abstract

In the published publication [...] Full article

16 pages, 1538 KiB

Open AccessReview

Energy-Saving Solutions Applied in Belt Conveyors: A Literature Review

by Martyna Konieczna-Fuławka

Energies 2025, 18(12), 3019; https://doi.org/10.3390/en18123019 - 6 Jun 2025

Abstract

Belt conveyors are essential systems for the continuous transport of various materials across many industries, particularly in bulk material handling for mining. While they are often the most economical solution, they still consume a significant amount of energy. This article discusses the latest [...] Read more.

Belt conveyors are essential systems for the continuous transport of various materials across many industries, particularly in bulk material handling for mining. While they are often the most economical solution, they still consume a significant amount of energy. This article discusses the latest advancements and the current state of energy-saving solutions for belt conveyors. Key solutions include low-friction belts, variable-frequency drives (VFDs), monitoring systems, automation, and regenerative belt conveyors. It is important to note that selecting the right construction parameters, performing preventive maintenance, and using appropriate materials are crucial for reducing energy consumption. By combining these energy-saving technologies with well-chosen construction parameters, it is possible to develop sustainable belt conveyors. Full article

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13 pages, 3256 KiB

Open AccessArticle

Temperature Dependence of the New Calibration Infrastructure for Impedance Metrology

by Marian Kampik, Krzysztof Musioł, Ryszard Rybski, Janusz Kaczmarek, Mirosław Kozioł, Maciej Koszarny, Adam Ziółek, Jolanta Jursza and Paweł Zawadzki

Energies 2025, 18(12), 3018; https://doi.org/10.3390/en18123018 - 6 Jun 2025

Abstract

This paper addresses issues relating to the temperature stability of impedance infrastructure used for the realization of impedance units and the calibration of measuring instruments. A description of the new infrastructure for impedance metrology recently developed in Poland is provided. We present the [...] Read more.

This paper addresses issues relating to the temperature stability of impedance infrastructure used for the realization of impedance units and the calibration of measuring instruments. A description of the new infrastructure for impedance metrology recently developed in Poland is provided. We present the results of measurements of temperature coefficients for four-port resistance standards and two-port capacitors used in the permuting capacitor device. We also report the results of stability tests of the recently developed temperature-controlled capacitance set. The results demonstrate excellent temperature stability for the impedance components and serve as an important source of information for selecting environmental conditions during comparisons and routine calibration. Full article

(This article belongs to the Special Issue Renewable Energy Microgrids for the Future of Electrical Grid—2nd Edition)

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28 pages, 4124 KiB

Open AccessReview

Thermal-Hydrologic-Mechanical Processes and Effects on Heat Transfer in Enhanced/Engineered Geothermal Systems

by Yu-Shu Wu and Philip H. Winterfeld

Energies 2025, 18(12), 3017; https://doi.org/10.3390/en18123017 - 6 Jun 2025

Abstract

Enhanced or engineered geothermal systems (EGSs), or non-hydrothermal resources, are highly notable among sustainable energy resources because of their abundance and cleanness. The EGS concept has received worldwide attention and undergone intensive studies in the last decade in the US and around the [...] Read more.

Enhanced or engineered geothermal systems (EGSs), or non-hydrothermal resources, are highly notable among sustainable energy resources because of their abundance and cleanness. The EGS concept has received worldwide attention and undergone intensive studies in the last decade in the US and around the world. In comparison, hydrothermal reservoir resources, the ‘low-hanging fruit’ of geothermal energy, are very limited in amount or availability, while EGSs are extensive and have great potential to supply the entire world with the needed energy almost permanently. The EGS, in essence, is an engineered subsurface heat mining concept, where water or another suitable heat exchange fluid is injected into hot formations to extract heat from the hot dry rock (HDR). Specifically, the EGS relies on the principle that injected water, or another working fluid, penetrates deep into reservoirs through fractures or high-permeability channels to absorb large quantities of thermal energy by contact with the host hot rock. Finally, the heated fluid is produced through production wells for electricity generation or other usages. Heat mining from fractured EGS reservoirs is subject to complex interactions within the reservoir rock, involving high-temperature heat exchange, multi-phase flow, rock deformation, and chemical reactions under thermal-hydrological-mechanical (THM) processes or thermal-hydrological-mechanical-chemical (THMC) interactions. In this paper, we will present a THM model and reservoir simulator and its application for simulation of hydrothermal geothermal systems and EGS reservoirs as well as a methodology of coupling thermal, hydrological, and mechanical processes. A numerical approach, based on discretizing the thermo-poro-elastic Navier equation using an integral finite difference method, is discussed. This method provides a rigorous, accurate, and efficient fully coupled methodology for the three (THM) strongly interacted processes. Several programs based on this methodology are demonstrated in the simulation cases of geothermal reservoirs, including fracture aperture enhancement, thermal stress impact, and tracer transport in a field-scale reservoir. Results are displayed to show geomechanics’ impact on fluid and heat flow in geothermal reservoirs. Full article

(This article belongs to the Section H2: Geothermal)

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22 pages, 5025 KiB

Open AccessReview

Recent Progress in Seawater Splitting Hydrogen Production Assisted by Value-Added Electrooxidation Reactions

by Yuanping Guo, Chenghao Yang, Jianli Yang, Xin Xiao, Maofei Ran and Jing Li

Energies 2025, 18(12), 3016; https://doi.org/10.3390/en18123016 - 6 Jun 2025

Abstract

Electrolysis of abundant seawater resources is a promising approach for hydrogen production. However, the high-concentration chloride ion in seawater readily induces the chlorine evolution reaction (CER), resulting in catalyst degradation and decreased electrolysis efficiency. In recent years, the electrooxidation of small organic molecules [...] Read more.

Electrolysis of abundant seawater resources is a promising approach for hydrogen production. However, the high-concentration chloride ion in seawater readily induces the chlorine evolution reaction (CER), resulting in catalyst degradation and decreased electrolysis efficiency. In recent years, the electrooxidation of small organic molecules (e.g., methanol), biomass-derived compounds (e.g., 5-hydroxymethylfurfural), and plastic monomers (e.g., ethylene glycol) has been seen to occur at lower potentials to substitute for the traditional oxygen evolution reaction (OER) and CER. This alternative approach not only significantly reduces energy consumption for hydrogen production but also generates value-added products at the anode. This review provides a comprehensive summary of research advancements in value-added electrooxidation reaction-assisted seawater hydrogen production technologies and emphasizes the underlying principles of various reactions and catalyst design methodologies. Finally, the current challenges in this field and potential future research directions are systematically discussed. Full article

(This article belongs to the Special Issue Advances in Electrocatalysis, Electrosynthesis, and Electrochemical Applications)

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21 pages, 921 KiB

Open AccessArticle

Energy and Environmental Benefits of In-Motion Charging Trolleybuses: A Case Study of Vilnius

by Olga Orynycz, Gabriel Santos Rodrigues, João Gilberto Mendes dos Reis, Ewa Kulesza, Jonas Matijošius and Sivanilza Teixeira Machado

Energies 2025, 18(12), 3015; https://doi.org/10.3390/en18123015 - 6 Jun 2025

Abstract

Reducing greenhouse gas (GHG) emissions depends mostly on urban transport electrification. However, the role of trolleybus systems in this process is still under discussion. The objective of this study was to analyze the viability of trolleybus buses in relation to diesel buses regarding [...] Read more.

Reducing greenhouse gas (GHG) emissions depends mostly on urban transport electrification. However, the role of trolleybus systems in this process is still under discussion. The objective of this study was to analyze the viability of trolleybus buses in relation to diesel buses regarding environmental and economic aspects. The research was conducted in Vilnius, Lithuania using an extended CO₂ emission methodology incorporating physicochemical fuel properties and real-world operational data that allowed us to estimate CO₂ emissions and economic impacts. The findings indicate that the Vilnius trolleybus system prevents 84,996.32 kg of CO₂ emissions monthly compared to diesel buses (gross avoided emissions). After accounting for emissions from electricity generation (based on Lithuania’s 2023 grid mix), the net avoided emissions are approximately 61,569 kg of CO₂ per month, equivalent to EUR 4284 in carbon credits. The system also significantly reduces local air pollutants. Moreover, the new In-Motion Charging (IMC) technology improves system flexibility by decreasing dependence on overhead wires and maintaining low emission levels. IMC trolleybuses represent a cost-efficient option compared to battery-electric buses (BEBs) and hydrogen fuel cell buses (FCEBs). Our findings support the European Union’s decarbonization goals and provide essential insights for policymakers considering public transportation electrification efforts. Full article

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

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16 pages, 3453 KiB

Open AccessArticle

Optimization and Analysis of Sensitive Areas for Look-Ahead Electromagnetic Logging-While-Drilling Based on Geometric Factors

by Guoyu Li, Zhenguan Wu, Xiaoqiao Liao, Xizhou Yue, Xiang Zhang, Tianlin Liu and Yunxin Zeng

Energies 2025, 18(12), 3014; https://doi.org/10.3390/en18123014 - 6 Jun 2025

Abstract

Look-ahead electromagnetic (EM) logging-while-drilling (LWD) plays an indispensable role in the prediction of deep and ultra-deep reservoirs. Traditional electromagnetic logging-while-drilling (EMLWD) and ultra-deep EMLWD technologies exhibit certain limitations in the real-time detection of ahead-of-bit formations, making it challenging to meet precision drilling requirements [...] Read more.

Look-ahead electromagnetic (EM) logging-while-drilling (LWD) plays an indispensable role in the prediction of deep and ultra-deep reservoirs. Traditional electromagnetic logging-while-drilling (EMLWD) and ultra-deep EMLWD technologies exhibit certain limitations in the real-time detection of ahead-of-bit formations, making it challenging to meet precision drilling requirements under complex well conditions, with the development of petroleum and gas geology and exploration progress I n the direction of deep, ultra-deep, and complex reservoirs. As a new LWD technology, look-ahead EMLWD enables real-time identification of formation structures, fluid distributions, and interface positions ahead of the drill bit during the drilling process by leveraging the propagation characteristics of EM. This capability provides critical decision-making support for wellbore trajectory optimization, drilling risk assessment, and reservoir evaluation. Therefore, this paper conducts research on theoretical methodologies for look-ahead EMLWD. Leveraging the Born geometric factor theory, we derive the expression for the 3D geometric factor spatial signal and analyze the sensitivity of each component related to look-ahead. Building on this foundation, we establish the sensitivity expression for look-ahead operations and investigate the impact of various antenna configurations on its signal. The results indicate that the coaxial component (gzz) and coplanar components (gxx and gyy) are the primary contributors to look-ahead EMLWD. As frequency decreases and spacing increases, the sensitive region for look-ahead expands. Moreover, look-ahead detection sensitivity becomes increasingly concentrated in front of the drill bit, while the signal at the opposite end is attenuated by incorporating additional coils. Under identical formation conditions, compared with a single-transmitter single-receiver system, a single-transmitter double-receiver coil system exhibits a significantly stronger signal amplitude and more pronounced changes at the formation boundary. Additionally, this configuration enhances sensitivity and extends the sensitive distance in response to variations in formation resistivity. Full article

(This article belongs to the Special Issue Advancements in Electromagnetic Technology for Electrical Engineering)

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