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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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16 pages, 3950 KiB  
Article
Characteristics of High-Pressure Hydrogen Jet Dispersion Along a Horizontal Plate
by Zhonglong He, Qingxin Ba, Jiaxin Zhang, Chenyi Yao, Yujie Wang and Xuefang Li
Energies 2025, 18(9), 2242; https://doi.org/10.3390/en18092242 - 28 Apr 2025
Viewed by 283
Abstract
Creating and updating safety regulations and standards for industrial processes and end-uses related to hydrogen demand a solid scientific foundation, which requires extensive research on unignited hydrogen releases from high-pressure systems across different situations. This study focuses on high-pressure hydrogen releases along a [...] Read more.
Creating and updating safety regulations and standards for industrial processes and end-uses related to hydrogen demand a solid scientific foundation, which requires extensive research on unignited hydrogen releases from high-pressure systems across different situations. This study focuses on high-pressure hydrogen releases along a horizontal plate to investigate the surface effects on hydrogen dispersion. Hydrogen releases from high-pressure sources up to 30 MPa were modeled using a computational fluid dynamics (CFD) method, with the CFD models validated by experimental data. The hydrogen dispersion characteristics along the plate were studied for various source pressures and leak nozzle diameters. The results show that the maximum flammable extent along the plate increases linearly with both the source pressure and nozzle diameter, while the combustible mass increases to the power of 1.5 with the increase in leakage flow rate. The locations where the jet centerline attach to the plate are identical (about 0.41 m away from the nozzle exit in the axial direction) for different source pressures (10~30 MPa) and nozzle diameters (0.5~1.5 mm). The flow region was divided into pre-attachment and attachment zones by the attachment point, and the self-similarity characteristics of both zones were analyzed. Finally, correlations for the centerline and lateral concentration distributions were developed for both the pre- and post-attachment zones. The results can help users quickly assess safety distance when hydrogen leaks along the plate. Full article
(This article belongs to the Special Issue Sustainable Development of Fuel Cells and Hydrogen Technologies)
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17 pages, 3297 KiB  
Article
Energy Recovery from Municipal Biodegradable Waste in a Circular Economy
by Anna Marciniuk-Kluska and Mariusz Kluska
Energies 2025, 18(9), 2210; https://doi.org/10.3390/en18092210 - 26 Apr 2025
Cited by 1 | Viewed by 377
Abstract
Faced with the challenges of the energy crisis and the need to reduce greenhouse gas emissions, Poland needs to increase the share of renewable energy sources in the energy mix. Development trends in the waste-to-energy market reflect the global energy transition. Poland generates [...] Read more.
Faced with the challenges of the energy crisis and the need to reduce greenhouse gas emissions, Poland needs to increase the share of renewable energy sources in the energy mix. Development trends in the waste-to-energy market reflect the global energy transition. Poland generates about 13 million tonnes of municipal waste annually, a significant percentage of which is biodegradable waste that should be converted into biogas or used in thermal processes to produce electricity and heat. Despite the benefits of recovering energy from waste, there are technological, economic, and regulatory barriers that limit the development of this sector in Poland. Creating an efficient waste management system is one of the most important challenges today in terms of energy, the environment, and the economy. The circular economy is a fundamental element of the European Union’s environmental policy, including the European Green Deal, the main objective of which is to combat the carbon footprint. The amount of energy produced is decisively influenced by the structure of the deposited waste and the share of the calorific fraction in the total mass of municipal waste. This study aimed to develop forecasts for biodegradable municipal waste, using the simulation and optimisation of the exponential Brownian smoothing constant, and to estimate the value of recovered energy. The forecasts were based on data on selective waste collection from different provinces of Poland. The study reveals that the forecast for biodegradable municipal waste in the coming years shows an increasing trend, amounting to 2,696,500 tonnes in 2030, which will allow for a significant increase in energy recovery. Full article
(This article belongs to the Special Issue Energy Markets and Energy Economy)
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20 pages, 2505 KiB  
Article
Anaerobic Co-Digestion of Common Reed and Plant-Based Biowaste from Households
by Robert Czubaszek and Agnieszka Wysocka-Czubaszek
Energies 2025, 18(9), 2178; https://doi.org/10.3390/en18092178 - 24 Apr 2025
Viewed by 319
Abstract
Organic wastes from households, private gardens, the maintenance of urban greenery, and active nature conservation measures are often difficult to manage. This lignocellulosic biomass may be suitable for anaerobic digestion (AD). However, the mono-digestion of plant material, such as waste from active conservation [...] Read more.
Organic wastes from households, private gardens, the maintenance of urban greenery, and active nature conservation measures are often difficult to manage. This lignocellulosic biomass may be suitable for anaerobic digestion (AD). However, the mono-digestion of plant material, such as waste from active conservation measures for wetlands, results in a low methane (CH4) yield. The aim of this study was to assess the feasibility of using common reed silage for co-digestion with plant-based biowaste from households. The specific methane yield (SMY) was determined in biochemical methane potential (BMP) tests performed on biowaste, reed silage, and combinations of reed silage with 10%, 30%, 50%, 70%, and 90% of biowaste on a fresh weight basis. The lowest SMY was observed for the mono-digestion of reed silage (160.40 ± 4.09 NL kgVS−1), while biowaste had the highest CH4 yield (284.03 ± 7.03 NL kgVS−1). The subsequent addition of biowaste enhanced CH4 production from 158.57 ± 7.88 NL kgVS−1 (10% of biowaste) to 233.28 ± 11.91 NL kgVS−1 (90% of biowaste). A key advantage of biogas production is its role in reducing CO2 emissions into the atmosphere, which result from the use of conventional fuels for energy generation. The avoided CO2 emissions generated in electricity and heat production range between 378.62 kgCO2 tTS−1 and 676.36 kgCO2 tTS−1 depending on the reed silage-to-biowaste ratio used for biogas production. This study reveals that reed silage is not an optimal feedstock for biogas production, and its share in co-digestion with biowaste should not exceed 10% of the total input to the biogas plant. Full article
(This article belongs to the Special Issue Sustainable Energy Development in Liquid Waste and Biomass: 2nd Edition)
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13 pages, 1759 KiB  
Review
Load Mismatch Compensation of Load-Modulated Power Amplifiers: A Comprehensive Review
by Yufeng Zang, Weimin Shi, Jinting Liu, Tian Qi and Mingyu Li
Energies 2025, 18(9), 2157; https://doi.org/10.3390/en18092157 - 23 Apr 2025
Viewed by 327
Abstract
With the diversification, acceleration, and arraying of wireless communication systems, power amplifiers (PAs) face stricter demands in terms of RF operation bandwidth, high-efficiency power range, and load mismatch compensation. After years of development, load-modulated PAs (LMPAs) can maintain high efficiency over a wide [...] Read more.
With the diversification, acceleration, and arraying of wireless communication systems, power amplifiers (PAs) face stricter demands in terms of RF operation bandwidth, high-efficiency power range, and load mismatch compensation. After years of development, load-modulated PAs (LMPAs) can maintain high efficiency over a wide bandwidth and a larger output back-off (OBO) range. However, there is obvious performance degradation when the load impedance of the current LMPAs is mismatched. To ensure the perfect application of power amplifiers in wireless communication systems, load mismatch compensation methods should be developed for LMPAs. Therefore, this paper gives a comprehensive review on the load mismatch compensation techniques of LMPAs, including the Doherty power amplifier and load-modulated balanced amplifier. Full article
(This article belongs to the Special Issue Renewable Energy Management System and Power Electronic Converters)
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35 pages, 3598 KiB  
Review
Green Synthesis of Core/Shell Phase Change Materials: Applications in Industry and Energy Sectors
by Aikaterini Feizatidou, Vassilios Binas and Ioannis A. Kartsonakis
Energies 2025, 18(8), 2127; https://doi.org/10.3390/en18082127 - 21 Apr 2025
Viewed by 963
Abstract
Engineered substances that demonstrate superior properties compared with conventional materials are called advanced materials. Thermal energy storage systems based on phase change materials (PCMs) offer an eco-friendly solution to reduce fuel and electricity consumption. PCMs are compounds that can store thermal energy in [...] Read more.
Engineered substances that demonstrate superior properties compared with conventional materials are called advanced materials. Thermal energy storage systems based on phase change materials (PCMs) offer an eco-friendly solution to reduce fuel and electricity consumption. PCMs are compounds that can store thermal energy in the form of latent heat during phase transitions. Green synthesis of core/shell composite PCMs is an environmentally friendly method for producing these materials, focusing on reducing energy consumption, minimizing the use of harmful chemicals, and utilizing biodegradable or sustainable materials. Green synthesis methods typically involve natural materials, solvent-free techniques, green solvents, biomimetic approaches, and energy-efficient processes. This review explores green synthesis methods like solvent-free techniques for core/shell PCMs production, highlighting their role in thermal regulation for energy-efficient buildings. Special attention is given to materials derived from biomass that can be used as precursors for PCM synthesis. Moreover, the principles of latent heat thermal energy storage systems with PCMs, in accordance with physical chemistry guidance, are also presented. Furthermore, materials that can be used as PCMs, along with the most effective methods for improving their thermal performance, as well as various passive applications in the building sector, are highlighted. Finally, the focus on the combination of environmentally friendly processes and the performance benefits of composite PCMs that offer a sustainable solution for thermal energy storage and management is also discussed. It was found that PCMs that are synthesized in a green way can reduce emissions and waste during production and disposal. Moreover, waste recycling and its use for another type of synthesis is also a potential green solution. Full article
(This article belongs to the Special Issue Biomass and Bio-Energy—2nd Edition)
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18 pages, 241 KiB  
Article
A Qualitative Analysis of Factors Leading to the Adoption of Residential Photovoltaics
by Evangelia Karasmanaki, Konstantinos Ioannou, Georgios Siakas, Spyros Galatsidas and Georgios Tsantopoulos
Energies 2025, 18(8), 2071; https://doi.org/10.3390/en18082071 - 17 Apr 2025
Cited by 1 | Viewed by 1049
Abstract
Although previous quantitative studies have examined various elements involved in the adoption of residential photovoltaic systems, there has been weaker emphasis on qualitative research despite its ability to understand the complexities behind adoption decisions. This article analyzes data from in-depth interviews with adopters [...] Read more.
Although previous quantitative studies have examined various elements involved in the adoption of residential photovoltaic systems, there has been weaker emphasis on qualitative research despite its ability to understand the complexities behind adoption decisions. This article analyzes data from in-depth interviews with adopters and identifies emerging themes about the factors leading householders to adopt residential photovoltaic systems. Thematic analysis identified five key themes related to the economic, environmental, social and technological motives and barriers to adopting residential photovoltaics. Adopters’ main motive was to acquire an additional regular income, which, inter alia, would enable them to cover anticipated expenses such as costs linked to having children at university. Many adopters also combined the adoption with life events such as house renovations. The adoption of photovoltaics was also seen as providing a safe way to invest savings. Moreover, most adopters identified themselves as technology enthusiasts indicating the positive effect of technophilia on residential photovoltaic adoption. Despite having installed photovoltaics, participants recognized that adoption can be inhibited by high capital cost, investment taxation and limited grid capacity. The similarities and variety in the decision-making patterns identified in this study can be used to develop or improve strategies aiming at increasing residential photovoltaic adoption. Full article
(This article belongs to the Special Issue Advancements in Sustainable Energy Technologies: Innovations, Integration, and Impact)
19 pages, 1900 KiB  
Article
An Analysis of the Synergistic Effects of Air Pollutant Reduction and Carbon Mitigation in Major Emission Reduction Policies in China’s Transportation Sector
by Jingan Zhu, Ping Jiang and Yuanxiang Chen
Energies 2025, 18(8), 1980; https://doi.org/10.3390/en18081980 - 12 Apr 2025
Viewed by 294
Abstract
As of 2023, China’s transportation energy carbon emissions account for over 10%, which has a significant impact on achieving “dual carbon” goals. China has successively issued various policies to address pollution emissions in the transportation industry. This study mainly analyzes the synergistic effects [...] Read more.
As of 2023, China’s transportation energy carbon emissions account for over 10%, which has a significant impact on achieving “dual carbon” goals. China has successively issued various policies to address pollution emissions in the transportation industry. This study mainly analyzes the synergistic effects of pollution reduction and carbon reduction measures implemented in this industry. We selected 2023 as the base year, focused on promoting new energy vehicles (NEVs), advocating bus transit (ABT), and advancing rail transit (ART) as the three major emission reduction policies, and analyzed their synergistic effects on air pollutant control and greenhouse gas emission reduction. Based on national scale data on driving conditions, energy consumption, and emission factors, the synergistic emission reductions in greenhouse gases and air pollutants brought about by the three policies were first calculated. Then, using the coordinate system of synergistic control effects, cross elasticity analysis of pollutants, and normalization evaluation methods, the multi pollutant synergistic control capabilities of each policy were quantified. Quantitative results revealed that the NEV substitution policy achieved a CO2 reduction of 100.966 million tons in 2023, alongside reductions of 1.0196 million tons (CO), 59,506 tons (NOx), 103,500 tons (NMHC), 6266 tons (PM10), and 3071 tons (SO2). Based on the APeq ranking, its comprehensive benefits (APeq = 166,734.52) significantly outperform ART (APeq = 97,414.89) and ABT (APeq = 19,796.80). The main research conclusion shows that replacing private gasoline cars with new energy vehicles can have a synergistic emission reduction effect on all five types of air pollutants and greenhouse gases involved in this study, with a positive synergistic effect. Moreover, the policy development priority is relatively better based on the synergistic emission reduction equivalent. Both buses and rail transit have not brought about SO2 emission reduction, nor have they had a positive synergistic effect on SO2 and CO2 emission reduction. On this basis, buses also contribute to NOx emissions. For other air pollutants, both rail transit and buses can have a synergistic effect of reducing pollution and carbon emissions. Full article
(This article belongs to the Section B: Energy and Environment)
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17 pages, 1486 KiB  
Article
Effect of Lignite Composition on Mercury Removal from Flue Gas in Sulfide Forced Wet Flue Gas Desulfurization (WFGD) Installations—Full-Scale Experiments
by Dariusz Łuszkiewicz, Maria Jędrusik, Arkadiusz Świerczok, Mariola Kobylańska-Pawlisz, Karel Borovec and Lukas Pilar
Energies 2025, 18(8), 1982; https://doi.org/10.3390/en18081982 - 12 Apr 2025
Viewed by 182
Abstract
In this article, the results of full-scale experiments on the addition of a sodium sulfide to the CaCO3 slurry circuit in a wet flue gas desulfurization (WFGD) plant are presented. Tests are performed on two comparable WFGD installations (spray tower, 4 spraying [...] Read more.
In this article, the results of full-scale experiments on the addition of a sodium sulfide to the CaCO3 slurry circuit in a wet flue gas desulfurization (WFGD) plant are presented. Tests are performed on two comparable WFGD installations (spray tower, 4 spraying levels and two stage gypsum de-watering by hydrocyclones and vacuum belt filter) which allows the investigation of the influence of lignite composition (lignite mined in Poland and the Czech Republic are compared) on the reduction in mercury emission. Additionally, the efficiency of precipitation of metals from the slurry (Hg, Zn, Pb, Cd, Cr, Cu, Ni, Fe, Se, and Mn) is investigated as the result of sulfide addition. For both objects, mercury re-emission from absorber occurs (the concentration of mercury in the chimney is higher than that before the WFGD absorber) and the sulfide addition to WFGD slurry stops this phenomenon. The addition of sulfide works effectively (mercury removal efficiency from flue gas reaches up to 88% for Polish tests and up to 87% for Czech Republic tests). For the tests in the Poland power plant, all of measured metals are precipitated from the slurry (precipitation of metals efficiency varied from 2% for zinc to 88% for mercury), but in the case of the test in the power plant in the Czech Republic, there is no effect on manganese, iron, and lead (precipitation of metals efficiency varied from 6.5% for copper to 86% for mercury). The addition of sulfide works effectively for lignite mined in Polish and Czech power plants under the conditions of similar WFGD installations. Full article
(This article belongs to the Section B: Energy and Environment)
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54 pages, 1932 KiB  
Article
Fokker–Planck Model-Based Central Moment Lattice Boltzmann Method for Effective Simulations of Thermal Convective Flows
by William Schupbach and Kannan Premnath
Energies 2025, 18(8), 1890; https://doi.org/10.3390/en18081890 - 8 Apr 2025
Viewed by 278
Abstract
The Fokker–Planck (FP) equation represents the drift and diffusive processes in kinetic models. It can also be regarded as a model for the collision integral of the Boltzmann-type equation to represent thermo-hydrodynamic processes in fluids. The lattice Boltzmann method (LBM) is a drastically [...] Read more.
The Fokker–Planck (FP) equation represents the drift and diffusive processes in kinetic models. It can also be regarded as a model for the collision integral of the Boltzmann-type equation to represent thermo-hydrodynamic processes in fluids. The lattice Boltzmann method (LBM) is a drastically simplified discretization of the Boltzmann equation for simulating complex fluid motions and beyond. We construct new two FP-based LBMs, one for recovering the Navier–Stokes equations for fluid dynamics and the other for simulating the energy equation, where, in each case, the effect of collisions is represented as relaxations of different central moments to their respective attractors. Such attractors are obtained by matching the changes in various discrete central moments due to collision with the continuous central moments prescribed by the FP model. As such, the resulting central moment attractors depend on the lower-order moments and the diffusion tensor parameters, and significantly differ from those based on the Maxwell distribution. The diffusion tensor parameters for evolving higher moments in simulating fluid motions at relatively low viscosities are chosen based on a renormalization principle. Moreover, since the number of collision invariants of the FP-based LBMs for fluid motions and energy transport are different, the forms of the respective attractors are quite distinct. The use of such central moment formulations in modeling the collision step offers significant improvements in numerical stability, especially for simulations of thermal convective flows under a wide range of variations in the transport coefficients of the fluid. We develop new FP central moment LBMs for thermo-hydrodynamics in both two and three dimensions, and demonstrate the ability of our approach to simulate various cases involving thermal convective buoyancy-driven flows especially at high Rayleigh numbers with good quantitative accuracy. Moreover, we show significant improvements in the numerical stability of our FP central moment LBMs when compared to other existing central moment LBMs using the Maxwell distribution in achieving high Peclet numbers for mixed convection flows involving shear effects. Full article
(This article belongs to the Special Issue Numerical Heat Transfer and Fluid Flow 2024)
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18 pages, 7325 KiB  
Article
Prediction of Breakdown Voltage of Long Air Gaps Under Switching Impulse Voltage Based on the ISSA-XGBoost Model
by Zisheng Zeng, Bin Song, Shaocheng Wu, Yongwen Li, Deyu Nie and Linong Wang
Energies 2025, 18(7), 1800; https://doi.org/10.3390/en18071800 - 3 Apr 2025
Viewed by 321
Abstract
In transmission lines, the discharge characteristics of long air gaps significantly influence the design of external insulation. Existing machine learning models for predicting breakdown voltage are typically limited to single gaps and do not account for the combined effects of complex factors. To [...] Read more.
In transmission lines, the discharge characteristics of long air gaps significantly influence the design of external insulation. Existing machine learning models for predicting breakdown voltage are typically limited to single gaps and do not account for the combined effects of complex factors. To address this issue, this paper proposes a novel prediction model based on the Improved Sparrow Search Algorithm-optimized XGBoost (ISSA-XGBoost). Initially, a comprehensive dataset of 46-dimensional electric field eigenvalues was extracted for each gap using finite element simulation software and MATLAB. Subsequently, the model incorporated a comprehensive set of input variables, including electric field eigenvalues, gap distance, waveform and polarity of the switching impulse voltage, temperature, relative humidity, and atmospheric pressure. After training, the ISSA-XGBoost model achieved a Mean Absolute Percentage Error (MAPE) of 7.85%, a Root Mean Squared Error (RMSE) of 56.92, and a Coefficient of Determination (R2) of 0.9938, indicating high prediction accuracy. In addition, the ISSA-XGBoost model was compared with traditional machine learning models and other optimization algorithms. These comparisons further substantiated the efficacy and superiority of the ISSA-XGBoost model. Notably, the model demonstrated exceptional performance in terms of predictive accuracy under extreme atmospheric conditions. Full article
(This article belongs to the Special Issue Advances in Design, Operation and Maintenance Technology for Electric Power Equipment)
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15 pages, 2795 KiB  
Article
Estimating Snow Coverage Percentage on Solar Panels Using Drone Imagery and Machine Learning for Enhanced Energy Efficiency
by Ashraf Saleem, Ali Awad, Amna Mazen, Zoe Mazurkiewicz and Ana Dyreson
Energies 2025, 18(7), 1729; https://doi.org/10.3390/en18071729 - 31 Mar 2025
Viewed by 509
Abstract
Snow accumulation on solar panels presents a significant challenge to energy generation in snowy regions, reducing the efficiency of solar photovoltaic (PV) systems and impacting economic viability. While prior studies have explored snow detection using fixed-camera setups, these methods suffer from scalability limitations, [...] Read more.
Snow accumulation on solar panels presents a significant challenge to energy generation in snowy regions, reducing the efficiency of solar photovoltaic (PV) systems and impacting economic viability. While prior studies have explored snow detection using fixed-camera setups, these methods suffer from scalability limitations, stationary viewpoints, and the need for reference images. This study introduces an automated deep-learning framework that leverages drone-captured imagery to detect and quantify snow coverage on solar panels, aiming to enhance power forecasting and optimize snow removal strategies in winter conditions. We developed and evaluated two approaches using YOLO-based models: Approach 1, a high-precision method utilizing a two-class detection model, and Approach 2, a real-time single-class detection model optimized for fast inference. While Approach 1 demonstrated superior accuracy, achieving an overall precision of 89% and recall of 82%, it is computationally expensive, making it more suitable for strategic decision making. Approach 2, with a precision of 93% and a recall of 75%, provides a lightweight and efficient alternative for real-time monitoring but is sensitive to lighting variations. The proposed framework calculates snow coverage percentages (SCP) to support snow removal planning, minimize downtime, and optimize power generation. Compared to fixed-camera-based snow detection models, our approach leverages drone imagery to improve detection precision while offering greater scalability to be adopted for large solar farms. Qualitative and quantitative analysis of both approaches is presented in this paper, highlighting their strengths and weaknesses in different environmental conditions. Full article
(This article belongs to the Special Issue Application of Machine Learning Tools for Energy System)
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40 pages, 1969 KiB  
Review
Reinforcement Learning for Optimizing Renewable Energy Utilization in Buildings: A Review on Applications and Innovations
by Panagiotis Michailidis, Iakovos Michailidis and Elias Kosmatopoulos
Energies 2025, 18(7), 1724; https://doi.org/10.3390/en18071724 - 30 Mar 2025
Cited by 1 | Viewed by 2343
Abstract
The integration of renewable energy systems into modern buildings is essential for enhancing energy efficiency, reducing carbon footprints, and advancing intelligent energy management. However, optimizing RES operations within building energy management systems introduces significant complexity, requiring advanced control strategies. One significant branch of [...] Read more.
The integration of renewable energy systems into modern buildings is essential for enhancing energy efficiency, reducing carbon footprints, and advancing intelligent energy management. However, optimizing RES operations within building energy management systems introduces significant complexity, requiring advanced control strategies. One significant branch of modern control algorithms concerns reinforcement learning, a data-driven strategy capable of dynamically managing renewable energy sources and other energy subsystems under uncertainty and real-time constraints. The current review systematically examines RL-based control strategies applied in BEMS frameworks integrating RES technologies between 2015 and 2025, classifying them by algorithmic approach and evaluating the role of multi-agent and hybrid methods in improving real-time adaptability and occupant comfort. Following a thorough explanation of a rigorous selection process—which targeted the most impactful peer-reviewed publications from the last decade, the paper presents the mathematical concepts of RL and multi-agent RL, along with detailed summaries and summary tables of the integrated works to facilitate quick reference to key findings. For evaluation, the paper examines and outlines the different attributes in the field considering the following: methodologies of RL; agent types; value-action networks; reward functions; baseline control approaches; RES types; BEMS types; and building typologies. Grounded on the findings presented in the evaluation section, the paper offers a structured synthesis of emerging research trends and future directions, identifying the strengths and limitations of RL in energy management. Full article
(This article belongs to the Special Issue New Insights into Hybrid Renewable Energy Systems in Buildings)
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17 pages, 15459 KiB  
Article
Integrated CFD and Experimental Analysis on Slinger Ring Condensate Discharge Mechanism for Energy-Efficient Window Air Conditioners
by Chin Hyuk Chang, Adarsh Rajasekharan Nair, Man Yeong Ha, Hyun Sik Yoon and Seok Beom Hong
Energies 2025, 18(7), 1622; https://doi.org/10.3390/en18071622 - 24 Mar 2025
Cited by 1 | Viewed by 232
Abstract
As global demand for energy-efficient cooling technologies grows, optimizing window air conditioners (WACs) is crucial. This study integrates computational fluid dynamics (CFD) and experimental fluid dynamics (EFD) to analyze condensate transport induced by the slinger ring in a WAC system. To investigate condensate [...] Read more.
As global demand for energy-efficient cooling technologies grows, optimizing window air conditioners (WACs) is crucial. This study integrates computational fluid dynamics (CFD) and experimental fluid dynamics (EFD) to analyze condensate transport induced by the slinger ring in a WAC system. To investigate condensate behavior, the WAC domain is divided into six regions based on the slinger ring’s rotational direction and impact. In the initial impact zone, large liquid structures adhere to the slinger ring before breaking into ligaments. In the upward transport region, condensate films rise along the wall due to centrifugal forces, forming short ligaments. In the rebound region, condensate impacts the top surface and transitions into droplets. In the accumulation zone, droplet coalescence occurs in a confined space, leading to localized mass buildup. In the dispersion region, condensate spreads widely due to increased rotational speed. In the splash zone, splashing and wave-like structures form near the reservoir surface. A newly identified mechanism of condensate mass discharge shows that mass ejection is concentrated in four key regions near the condenser coils. These findings offer insights into optimizing a slinger ring design for improved condensate dispersion. Future research should explore airflow variations and alternative slinger ring configurations to enhance WAC performance. Full article
(This article belongs to the Section G: Energy and Buildings)
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23 pages, 8035 KiB  
Article
Reverse Oil Flow Characterization in Transformer Windings: A Fluid-Thermal Network Approach
by Lujia Wang, Jianghao Qi, Yifan Chen, Lebin Zhang and Jianwen Zhang
Energies 2025, 18(7), 1593; https://doi.org/10.3390/en18071593 - 22 Mar 2025
Viewed by 295
Abstract
When the inlet flow velocity in the disc-type winding region of an oil-immersed transformer operates within a high Reynolds number range, it leads to an uneven distribution of oil flow. This phenomenon results in the abnormal occurrence of reverse oil flow in the [...] Read more.
When the inlet flow velocity in the disc-type winding region of an oil-immersed transformer operates within a high Reynolds number range, it leads to an uneven distribution of oil flow. This phenomenon results in the abnormal occurrence of reverse oil flow in the bottom oil ducts, causing the hotspot temperature to rise instead of decrease. To address this issue, a three-node flow resistance module was introduced at the intersection of T-shaped oil ducts based on the flow paths of oil in the main and branch ducts within the disc-type winding region. A flow network model for the transformer winding region was subsequently constructed. The accuracy of the model was validated through CFD simulations and experiments conducted on a transformer winding region test platform, with a maximum relative error of 4.02%. The model successfully predicted the flow distribution of the cooling oil within the winding region. Furthermore, by considering the structural characteristics of the winding region and the principles of heat transfer, particular attention was given to variations in local Nusselt number correlations. This led to the development of a thermal network model tailored to the winding region experiencing reverse oil flow. Comparative analysis of the model’s calculation results yielded a maximum relative error of only 1.12%, demonstrating its ability to rapidly and accurately elucidate the reverse oil flow effect. This study provides a theoretical foundation for the identification and mitigation of reverse oil flow in future applications. Full article
(This article belongs to the Special Issue Advances in Design, Operation and Maintenance Technology for Electric Power Equipment)
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19 pages, 4414 KiB  
Article
Photovoltaic Power System with Electrochemical and Hydrogen Storage for Energy Independence in Student Dormitories
by Tomasz Trawiński and Janusz Kotowicz
Energies 2025, 18(7), 1570; https://doi.org/10.3390/en18071570 - 21 Mar 2025
Viewed by 287
Abstract
This article analyzes the path towards achieving electric energy independence for dormitories. It examines electricity consumption in dormitories to determine the necessary volume for daily electrochemical energy storage systems, seasonal hydrogen storage system capacity, and photovoltaic (PV) system power. Electricity consumption data from [...] Read more.
This article analyzes the path towards achieving electric energy independence for dormitories. It examines electricity consumption in dormitories to determine the necessary volume for daily electrochemical energy storage systems, seasonal hydrogen storage system capacity, and photovoltaic (PV) system power. Electricity consumption data from dormitories between 2021 and 2024 were analyzed, showing hourly, daily, and monthly trends. The study developed a mathematical model of hourly electric energy usage and production in Matlab/Simulink to optimize the photovoltaic (PV) system, increase self-consumption potential, and enhance surplus energy storage. This enabled the selection of capacities for daily and seasonal storage, along with PV system power to meet dormitory energy needs, particularly in autumn and winter. The software accommodates monthly energy consumption profiles and PV system characteristics, allowing for the estimation of electric energy surplus after usage by inhabitants for hydrogen production and storage. The study offers a comprehensive framework for sustainable electric energy management in student housing. Full article
(This article belongs to the Section B: Energy and Environment)
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33 pages, 2848 KiB  
Review
A Review on Phase-Change Materials (PCMs) in Solar-Powered Refrigeration Systems
by Yali Guo, Chufan Liang, Hui Liu, Luyuan Gong, Minle Bao and Shengqiang Shen
Energies 2025, 18(6), 1547; https://doi.org/10.3390/en18061547 - 20 Mar 2025
Cited by 1 | Viewed by 758
Abstract
Over the past few years, the combination of solar power with refrigeration technology has matured, providing a promising solution for sustainable cooling. However, a key challenge remains, namely the inherent intermittency of solar energy. Due to its uneven temporal distribution, it is difficult [...] Read more.
Over the past few years, the combination of solar power with refrigeration technology has matured, providing a promising solution for sustainable cooling. However, a key challenge remains, namely the inherent intermittency of solar energy. Due to its uneven temporal distribution, it is difficult to ensure continuous 24 h operation when relying solely on solar energy. To address this issue, thermal energy storage technology has emerged as a viable solution. This paper presents a comprehensive systematic review of phase-change material (PCM) applications in solar refrigeration systems. It systematically categorizes solar energy conversion methodologies and refrigeration system configurations while elucidating the fundamental operational principles of each solar refrigeration system. A detailed examination of system components is provided, encompassing photovoltaic panels, condensers, evaporators, solar collectors, absorbers, and generators. The analysis further investigates PCM integration strategies with these components, evaluating integration effectiveness and criteria for PCM selection. The critical physical parameters of PCMs are comparatively analyzed, including phase transition temperature, latent heat capacity, specific heat, density, and thermal conductivity. Through conducting a critical analysis of existing studies, this review comprehensively evaluates current research progress within PCM integration techniques, methodological classification frameworks, performance enhancement approaches, and system-level implementation within solar refrigeration systems. The investigation concludes by presenting strategic recommendations for future research priorities based on a comprehensive systematic evaluation of technological challenges and knowledge gaps within the domain. Full article
(This article belongs to the Special Issue Advanced Technology for Solar Thermal Cooling, Heating, and Energy Storage)
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12 pages, 3213 KiB  
Article
Three-Dimensionally Printed Metal-Coated Flow-Field Plate for Lightweight Polymer Electrolyte Membrane Fuel Cells
by Dasol Kim, Geonhwi Kim, Juho Na, Hyeok Kim, Jaeyeon Kim, Guyoung Cho and Taehyun Park
Energies 2025, 18(6), 1533; https://doi.org/10.3390/en18061533 - 20 Mar 2025
Viewed by 415
Abstract
This study investigates the potential for affordable and lightweight polymer electrolyte membrane fuel cells (PEMFCs) using lightweight flow-field plates, also referred to as bipolar plates. A comparative analysis was conducted on the performance of metal-coated and uncoated three-dimensional (3D)-printed flow-field plates, as well [...] Read more.
This study investigates the potential for affordable and lightweight polymer electrolyte membrane fuel cells (PEMFCs) using lightweight flow-field plates, also referred to as bipolar plates. A comparative analysis was conducted on the performance of metal-coated and uncoated three-dimensional (3D)-printed flow-field plates, as well as that of a conventional graphite flow-field plate. The fabrication of these lightweight flow-field plates involved the application of sputtering and 3D printing technologies. The polarization curves and corresponding electrochemical impedance spectra of PEMFCs with metal-coated 3D-printed, uncoated 3D-printed, and graphite flow-field plates were measured. The results demonstrate that the metal-coated 3D-printed flow-field plate exhibits a gravimetric power density of 5.21 mW/g, while the graphite flow-field plate registers a value of 2.78 mW/g, representing an 87.4% improvement in gravimetric power density for the metal-coated 3D-printed flow-field plate compared to the graphite flow-field plate. These findings suggest the feasibility of reducing the weight of PEMFCs using metal-coated 3D-printed flow-field plates. Full article
(This article belongs to the Special Issue Sustainable Development of Fuel Cells and Hydrogen Technologies)
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17 pages, 5157 KiB  
Article
Performance Improvement of Proton Exchange Membrane Fuel Cells with a TiO2 Sputtered Gas Diffusion Layer Under Low-Humidity Conditions
by Byung Gyu Kang, Ye Rim Kwon, Ki Won Hong, Sun Ki Kwon, Hyeon Min Lee, Dong Kun Song, Ji Woong Jeon, Do Young Jung, Dohyun Go and Gu Young Cho
Energies 2025, 18(6), 1525; https://doi.org/10.3390/en18061525 - 19 Mar 2025
Viewed by 481
Abstract
Proton exchange membrane fuel cells (PEMFCs) are pivotal to advancing sustainable hydrogen energy systems. However, their performance decreases under low-humidity conditions (relative humidity, RH 50%) due to inadequate membrane hydration. This study addresses this challenge by utilizing a sputtering process to deposit titanium [...] Read more.
Proton exchange membrane fuel cells (PEMFCs) are pivotal to advancing sustainable hydrogen energy systems. However, their performance decreases under low-humidity conditions (relative humidity, RH 50%) due to inadequate membrane hydration. This study addresses this challenge by utilizing a sputtering process to deposit titanium dioxide (TiO2) onto microporous layers (MPLs), enhancing their hydrophilicity and water management capabilities. TiO2 intrinsic hydrophilic properties and oxygen vacancies improve water adsorption and distribution, leading to more stable PEMFC performance under reduced humidity. Electrochemical evaluations revealed that while initial resistance slightly increased, long-term stability improved significantly. The TiO2-coated MPL exhibited a lower performance degradation rate, with a 12.33% reduction in current density compared to 25.3% for the pristine MPL after 10 h of operation. These findings demonstrate that TiO2 deposition effectively mitigates performance losses under low-humidity conditions, reducing the reliance on external humidification systems. This work contributes to the development of more efficient and sustainable fuel cell technologies for applications such as hydrogen-powered vehicles and distributed energy systems. Full article
(This article belongs to the Special Issue Sustainable Development of Fuel Cells and Hydrogen Technologies)
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25 pages, 2723 KiB  
Article
A Cost-Optimizing Analysis of Energy Storage Technologies and Transmission Lines for Decarbonizing the UK Power System by 2035
by Liliana E. Calderon Jerez and Mutasim Nour
Energies 2025, 18(6), 1489; https://doi.org/10.3390/en18061489 - 18 Mar 2025
Cited by 1 | Viewed by 427
Abstract
The UK net zero strategy aims to fully decarbonize the power system by 2035, anticipating a 40–60% increase in demand due to the growing electrification of the transport and heating sectors over the next thirteen years. This paper provides a detailed technical and [...] Read more.
The UK net zero strategy aims to fully decarbonize the power system by 2035, anticipating a 40–60% increase in demand due to the growing electrification of the transport and heating sectors over the next thirteen years. This paper provides a detailed technical and economic analysis of the role of energy storage technologies and transmission lines in balancing the power system amidst large shares of intermittent renewable energy generation. The analysis is conducted using the cost-optimizing energy system modelling framework REMix, developed by the German Aerospace Center (DLR). The obtained results of multiple optimization scenarios indicate that achieving the lowest system cost, with a 73% share of electricity generated by renewable energy sources, is feasible only if planning rules in England and Wales are flexible enough to allow the construction of 53 GW of onshore wind capacity. This flexibility would enable the UK to become a net electricity exporter, assuming an electricity trading market with neighbouring countries. Depending on the scenario, 2.4–11.8 TWh of energy storage supplies an average of 11% of the electricity feed-in, with underground hydrogen storage representing more than 80% of that total capacity. In terms of storage converter capacity, the optimal mix ranges from 32 to 34 GW of lithium-ion batteries, 13 to 22 GW of adiabatic compressed air energy storage, 4 to 24 GW of underground hydrogen storage, and 6 GW of pumped hydro. Decarbonizing the UK power system by 2035 is estimated to cost $37–56 billion USD, with energy storage accounting for 38% of the total system cost. Transmission lines supply 10–17% of the total electricity feed-in, demonstrating that, when coupled with energy storage, it is possible to reduce the installed capacity of conventional power plants by increasing the utilization of remote renewable generation assets and avoiding curtailment during peak generation times. Full article
(This article belongs to the Special Issue Renewable Energy System Technologies: 2nd Edition)
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18 pages, 8906 KiB  
Article
Optimization of Energy Recovery Processes from Sunflower Stalks Using Expired Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)
by Valentina Zubkova, Andrzej Strojwas and Stanislaw Baran
Energies 2025, 18(6), 1509; https://doi.org/10.3390/en18061509 - 18 Mar 2025
Viewed by 317
Abstract
The influence of the addition of expired paracetamol, naproxen, ibuprofen, and their blend on the course of pyrolysis of sunflower stalks was studied using the gravimetric technique as well as the techniques of IR and UV, XRD, and SEM and EDX spectroscopies. It [...] Read more.
The influence of the addition of expired paracetamol, naproxen, ibuprofen, and their blend on the course of pyrolysis of sunflower stalks was studied using the gravimetric technique as well as the techniques of IR and UV, XRD, and SEM and EDX spectroscopies. It was ascertained that ibuprofen has the highest effect in reduction of hydrocarbons in the composition of volatile pyrolysis products, which lowers the contribution of bands: saturated and unsaturated hydrocarbons by about 2.36 times; compounds with carbonyl groups by almost by three times; and the contribution of alcohols, phenols, and esters by 2.5 times in the FT-IR spectra. The reasons for a greater effectiveness of ibuprofen in reducing hydrocarbons in volatiles can be its lower temperature of decomposition and distinct composition of formed volatile pyrolysis products. Up to the temperature of 450 °C, paracetamol inhibits the migration of AAEMs from the pyrolyzed sample, the blend of pharmaceuticals accelerates the migration of all AAEMs except inorganics with Mg atoms. In the sediment of char of ibuprofen additive, there is a higher amount of Ca, Mg, and Cl atoms than in other chars, which can explain a greater influence of ibuprofen on the reduction of hydrocarbons in the composition of volatiles. Full article
(This article belongs to the Special Issue Biomass and Bio-Energy—2nd Edition)
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41 pages, 6321 KiB  
Review
The Catalytic Valorization of Lignin from Biomass for the Production of Liquid Fuels
by Chenchen Gui, Lida Wang, Guoshun Liu, Ajibola T. Ogunbiyi and Wenzhi Li
Energies 2025, 18(6), 1478; https://doi.org/10.3390/en18061478 - 17 Mar 2025
Cited by 1 | Viewed by 614
Abstract
With the overuse of fossil fuels, people are looking for alternatives. This is an area where biofuels have received a lot of attention. Studies have also shown that a large variety of liquid fuels of commercial interest can be obtained via lignin valorization. [...] Read more.
With the overuse of fossil fuels, people are looking for alternatives. This is an area where biofuels have received a lot of attention. Studies have also shown that a large variety of liquid fuels of commercial interest can be obtained via lignin valorization. Lignin is rich in aromatic ring structures and can be used as a sustainable raw material to produce high-value energy. Therefore, progress in the preparation of liquid fuels from lignin by pyrolysis, hydro-processing, and oxidation is analyzed in this review. Nevertheless, due to the three-dimension network structure of lignin, there are many barriers that need to be surmounted before utilizing it, such as its complex connection with cellulose and hemicellulose, which makes its separation difficult. In this paper, different pretreatment methods are summarized for separating lignin from other two components. Finally, the challenges in future trends of lignin valorization are summarized and outlined. It is clear that the construction of efficient separation and catalytic systems will be the focus of future research in this field. Full article
(This article belongs to the Special Issue Biomass to Liquid Fuels)
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30 pages, 3767 KiB  
Article
Uniqueness of Optimal Power Management Strategies for Energy Storage Dynamic Models
by Tom Goldstein-Tweg, Elinor Ginzburg-Ganz, Juri Belikov and Yoash Levron
Energies 2025, 18(6), 1483; https://doi.org/10.3390/en18061483 - 17 Mar 2025
Viewed by 236
Abstract
This paper contributes to the field of analytic and semi-analytic solutions for optimal power flow problems involving storage systems. Its primary contribution is a rigorous proof establishing the uniqueness of the “shortest path” optimal solution, a key element in this class of algorithms, [...] Read more.
This paper contributes to the field of analytic and semi-analytic solutions for optimal power flow problems involving storage systems. Its primary contribution is a rigorous proof establishing the uniqueness of the “shortest path” optimal solution, a key element in this class of algorithms, building upon a graphical design procedure previously introduced. The proof is constructed through five consequential lemmas, each defining a distinct characteristic of the optimal solution. These characteristics are then synthesized to demonstrate the uniqueness of the optimal solution, which corresponds to the shortest path of generated energy within defined bounds. This proof not only provides a solid theoretical foundation for this algorithm class but also paves the way for developing analytic solutions to more complex optimal control problems incorporating storage. Furthermore, the efficacy of this unique solution is validated through two comparative tests. The first one uses synthetic data to benchmark the proposed solution in comparison to recent reinforcement learning algorithms, including actor–critic, PPO, and TD3. The second one compares the proposed solution to the optimal solutions derived from other numerical methods based on real-world data from an electrical vehicle storage device. Full article
(This article belongs to the Section D: Energy Storage and Application)
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27 pages, 4067 KiB  
Article
The Estimation of the Possibility of Bioethanol Production from Hemp Cellulose Using the HWE Method
by Kamil Roman
Energies 2025, 18(6), 1441; https://doi.org/10.3390/en18061441 - 14 Mar 2025
Cited by 1 | Viewed by 506
Abstract
This study investigates the effect of hot water extraction (HWE). The research investigates how different biomass fractions (0–4 mm, 4–8 mm, and 8–16 mm) respond to hydrothermal treatment, with cellulose content analyzed using the Kürschner–Hoffer method. Results indicate that cellulose loss varies across [...] Read more.
This study investigates the effect of hot water extraction (HWE). The research investigates how different biomass fractions (0–4 mm, 4–8 mm, and 8–16 mm) respond to hydrothermal treatment, with cellulose content analyzed using the Kürschner–Hoffer method. Results indicate that cellulose loss varies across fractions, with the highest degradation observed in the 8–16 mm fraction and the lowest in stalks thinner than 4 mm. The HWE process removes both hemicellulose and lignin selectively, which helps improve enzyme accessibility and maximize bioethanol yields. The absence of fermentation inhibitors suggests that HWE is an effective alternative to acid-based pretreatment. Based on these findings, optimizing process parameters for sustainable bioethanol production from hemp biomass may be possible. Optimal HWE conditions and alternate pretreatment methods should be evaluated in future research to maximize efficiency and industrial feasibility. Full article
(This article belongs to the Special Issue Biomass and Waste-to-Energy for Sustainable Energy Production)
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17 pages, 4453 KiB  
Article
Remote Monitoring, Simulation and Diagnosis of Electronically Controlled Marine Engines
by Ozren Bukovac, Vladimir Pelić, Tomislav Mrakovčić, Maro Jelić, Gojmir Radica, Tino Vidović, Nikola Račić, Branko Lalić and Karlo Bratić
Energies 2025, 18(6), 1399; https://doi.org/10.3390/en18061399 - 12 Mar 2025
Cited by 1 | Viewed by 522
Abstract
The implementation of a system for the acquisition, transferring and processing of data essential for marine engine diagnostics is the basis of condition maintenance. Determining the most influential operating parameters, and conducting monitoring, analysis and taking action based on expert knowledge prevents downtime [...] Read more.
The implementation of a system for the acquisition, transferring and processing of data essential for marine engine diagnostics is the basis of condition maintenance. Determining the most influential operating parameters, and conducting monitoring, analysis and taking action based on expert knowledge prevents downtime due to possible malfunctions. Timely corrections and replacements of worn parts based on condition diagnostics enable maintenance planning, which reduces the frequency of maintenance and the accumulation of unnecessary spare parts in warehouses. For research purposes, a system for remote data collection from electronically controlled marine engines was developed and applied. The system was installed on a four-stroke high-speed propulsion engine from a ferry, and the operating parameters of the engine were monitored during regular sailing in order to detect irregularities and possible failures at an early stage. The measurement system monitored the parameters obtained through the electronic engine control module via the J1939 protocol, and in this paper, the following relevant engine parameters were analyzed: engine speed, boost pressure, fuel consumption and engine load at the current speed. The analysis included the creation of trend diagrams to present the distribution of the minimum, median and maximum values of each parameter of all the measurements performed. This study also examined the simulation of the faults of the high-speed four-stroke marine engine model. By utilizing sensor data from critical system components, this research investigated different scenarios. The analysis aimed to elucidate the impact of these faults on engine performance. Based on the analyses of the relevant operating parameters of the engine, diagnostics were carried out. Full article
(This article belongs to the Special Issue Internal Combustion Engine Performance 2024)
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15 pages, 2070 KiB  
Article
Performance and Emissions of Spark-Ignition Internal Combustion Engine Operating with Bioethanol–Gasoline Blends at High Altitudes Under Low- and High-Speed Conditions
by Alexander García Mariaca, Jorge Villalba, Rodrigo Morillo Castaño and Manuel Bailera
Energies 2025, 18(6), 1401; https://doi.org/10.3390/en18061401 - 12 Mar 2025
Viewed by 608
Abstract
Several countries have cities located at elevations above 2000 m. Consequently, the internal combustion engines (ICEs) that operate there do not achieve the desired performance and emissions under these atmospheric conditions. One approach to mitigate these effects and, at the same time, address [...] Read more.
Several countries have cities located at elevations above 2000 m. Consequently, the internal combustion engines (ICEs) that operate there do not achieve the desired performance and emissions under these atmospheric conditions. One approach to mitigate these effects and, at the same time, address climate change is the use of biofuel–fossil fuel blends. However, ICEs must operate under a wide range of rpm to meet varying workload demands, raising concerns that these fuel blends may not be fully effective in achieving the desired performance and emission outcomes under such conditions. To address this issue, a series of experimental tests were conducted at low and high rpm of a spark-ignition (SI) ICE fuelled with bioethanol–gasoline blends in the ratios of E10, E15, E20, E40, E60, E85, and E100. The tests were conducted at 2600 m above sea level (masl) under various engine loads. The E20 and E40 blends showed outstanding performance at 2700 rpm, achieving high brake power and low emissions of CO2 and HCs. At 4300 rpm, the E40 blend exhibited great performance because the engine produced high brake power and low emissions of CO and NOx. Based on these results, it can be concluded that bioethanol concentrations of between 20 and 40% in the blend effectively compensate for the reduced atmospheric oxygen at high altitudes, enhancing the combustion process in SI-ICEs. Full article
(This article belongs to the Special Issue Renewable Fuels: A Key Step Towards Global Sustainability)
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26 pages, 2558 KiB  
Article
Biogenic CO2 Emissions in the EU Biofuel and Bioenergy Sector: Mapping Sources, Regional Trends, and Pathways for Capture and Utilisation
by Diogenis Christianides, Dimitra Antonia Bagaki, Rudolphus Antonius Timmers, Maja Berden Zrimec, Anastasia Theodoropoulou, Irini Angelidaki, Panagiotis Kougias, Guido Zampieri, Najla Kamergi, Alfredo Napoli, Dimitris Malamis, Sofia Mai and Elli Maria Barampouti
Energies 2025, 18(6), 1345; https://doi.org/10.3390/en18061345 - 10 Mar 2025
Cited by 2 | Viewed by 1438
Abstract
The European biofuel and bioenergy industry faces increasing challenges in achieving sustainable energy production while meeting carbon neutrality targets. This study provides a detailed analysis of biogenic emissions from biofuel and bioenergy production, with a focus on key sectors such as biogas, biomethane, [...] Read more.
The European biofuel and bioenergy industry faces increasing challenges in achieving sustainable energy production while meeting carbon neutrality targets. This study provides a detailed analysis of biogenic emissions from biofuel and bioenergy production, with a focus on key sectors such as biogas, biomethane, bioethanol, syngas, biomass combustion, and biomass pyrolysis. Over 18,000 facilities were examined, including their feedstocks, production processes, and associated greenhouse gas emissions. The results highlight forestry residues as the predominant feedstock and expose significant disparities in infrastructure and technology adoption across EU Member States. While countries like Sweden and Germany lead in emissions management and carbon capture through bioenergy production with carbon capture and storage systems (BECCS), other regions face deficiencies in bioenergy infrastructure. The findings underscore the potential of BECCS and similar carbon management technologies to achieve negative emissions and support the European Green Deal’s climate neutrality goals. This work serves as a resource for policymakers, industry leaders, and researchers, fostering informed strategies for the sustainable advancement of the biofuels sector. Full article
(This article belongs to the Special Issue Carbon Capture Technologies for Sustainable Energy Production)
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16 pages, 18543 KiB  
Review
A Review on Thermal Management and Heat Dissipation Strategies for 5G and 6G Base Stations: Challenges and Solutions
by Talib Dbouk and Oumar Mourad
Energies 2025, 18(6), 1355; https://doi.org/10.3390/en18061355 - 10 Mar 2025
Cited by 1 | Viewed by 1288
Abstract
A literature review is presented on energy consumption and heat transfer in recent fifth-generation (5G) antennas in network base stations. The review emphasizes on the role of computational science in addressing emerging design challenges for the coming 6G technology, such as reducing energy [...] Read more.
A literature review is presented on energy consumption and heat transfer in recent fifth-generation (5G) antennas in network base stations. The review emphasizes on the role of computational science in addressing emerging design challenges for the coming 6G technology, such as reducing energy consumption and enhancing equipment thermal management in more compact designs. It examines the contributions of (i) advanced modeling and simulation sciences, including antenna modeling and design, the use of (ii) computational fluid dynamics (CFD) and heat transfer, and (iii) the application of artificial intelligence (AI) in these settings. The scientific interactions and collaborations between these scientific multidisciplinary approaches are vital in the effort to develop innovative 6G thermal equipment designs. This is essential if we are to overcome the current scientific barriers and challenges faced by this evolving technology, where the rapid transition from 5G to 6G will shape the expanding fields of deploying smaller satellites into lower orbits in outer space. Full article
(This article belongs to the Special Issue Heat Transfer Principles and Applications)
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21 pages, 1279 KiB  
Article
Stakeholder and Techno-Economic Assessment of Iceland’s Green Hydrogen Economy
by Nargessadat Emami, Reza Fazeli, Til Seth Tzschockel, Kevin Joseph Dillman and Jukka Heinonen
Energies 2025, 18(6), 1325; https://doi.org/10.3390/en18061325 - 7 Mar 2025
Viewed by 715
Abstract
Green hydrogen is a promising energy carrier for the decarbonization of hard-to-abate sectors and supporting renewable energy integration, aligning with carbon neutrality goals like the European Green Deal. Iceland’s abundant renewable energy and decarbonized electricity system position it as a strong candidate for [...] Read more.
Green hydrogen is a promising energy carrier for the decarbonization of hard-to-abate sectors and supporting renewable energy integration, aligning with carbon neutrality goals like the European Green Deal. Iceland’s abundant renewable energy and decarbonized electricity system position it as a strong candidate for green hydrogen production. Despite early initiatives, its hydrogen economy has yet to significantly expand. This study evaluated Iceland’s hydrogen development through stakeholder interviews and a techno-economic analysis of alkaline and PEM electrolyzers. Stakeholders were driven by decarbonization goals, economic opportunities, and energy security but faced technological, economic, and governance challenges. Recommendations include building stakeholder confidence, financial incentives, and creating hydrogen-based chemicals to boost demand. Currently, alkaline electrolyzers are more cost-effective (EUR 1.5–2.8/kg) than PEMs (EUR 2.1–3.6/kg), though the future costs for both could drop below EUR 1.5/kg. Iceland’s low electricity costs and high electrolyzer capacity provide a competitive edge. However, this advantage may shrink as solar and wind costs decline globally, particularly in regions like Australia. This work’s findings emphasize the need for strategic planning to sustain competitiveness and offer transferable insights for other regions introducing hydrogen into ecosystems lacking infrastructure. Full article
(This article belongs to the Special Issue Green Hydrogen Energy Production)
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21 pages, 11659 KiB  
Article
Machine Learning-Based Evaluation of Solar Photovoltaic Panel Exergy and Efficiency Under Real Climate Conditions
by Gökhan Şahin and Wilfried G. J. H. M. van Sark
Energies 2025, 18(6), 1318; https://doi.org/10.3390/en18061318 - 7 Mar 2025
Cited by 2 | Viewed by 688
Abstract
The purpose of this study article is to provide a detailed examination of the performance of exergy electric panels, exergy efficiency panels and exergy solar panels under the climatic circumstances of the Utrecht region in the Netherlands. The study explores the performance of [...] Read more.
The purpose of this study article is to provide a detailed examination of the performance of exergy electric panels, exergy efficiency panels and exergy solar panels under the climatic circumstances of the Utrecht region in the Netherlands. The study explores the performance of these solar panels in terms of both their energy efficiency and their exergy efficiency. Additionally, the study investigates critical factors such as solar radiation, module internal temperature, air temperature, maximum power, and solar energy efficiency. Environmental factors have a considerable impact on panel performance; temperature has a negative impact on efficiency, whereas an increase in solar radiation leads to an increase in energy and exergy output. These findings offer significant insights that can be used to increase the utilization of solar energy in locations that have a temperate oceanic climate, particularly in the context of the climatic conditions of the Utrecht region. The usefulness of the linear regression model in machine learning was validated by performance measures such as R2, RMSE, MAE, and MAPE. Furthermore, an R2 value of 0.94889 was found for the parameters that were utilized. Policy makers, researchers, and industry stakeholders who seek to successfully utilize solar energy in the face of changing climatic conditions may find this research to be an important reference. Full article
(This article belongs to the Topic Sustainable Energy: Efficient Technological Solutions Combining Environmental, Economic, Political and Social Aspects, 2nd Edition)
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17 pages, 954 KiB  
Article
Leveraging Explainable Artificial Intelligence in Solar Photovoltaic Mappings: Model Explanations and Feature Selection
by Eduardo Gomes, Augusto Esteves, Hugo Morais and Lucas Pereira
Energies 2025, 18(5), 1282; https://doi.org/10.3390/en18051282 - 5 Mar 2025
Cited by 1 | Viewed by 672
Abstract
This work explores the effectiveness of explainable artificial intelligence in mapping solar photovoltaic power outputs based on weather data, focusing on short-term mappings. We analyzed the impact values provided by the Shapley additive explanation method when applied to two algorithms designed for tabular [...] Read more.
This work explores the effectiveness of explainable artificial intelligence in mapping solar photovoltaic power outputs based on weather data, focusing on short-term mappings. We analyzed the impact values provided by the Shapley additive explanation method when applied to two algorithms designed for tabular data—XGBoost and TabNet—and conducted a comprehensive evaluation of the overall model and across seasons. Our findings revealed that the impact of selected features remained relatively consistent throughout the year, underscoring their uniformity across seasons. Additionally, we propose a feature selection methodology utilizing the explanation values to produce more efficient models, by reducing data requirements while maintaining performance within a threshold of the original model. The effectiveness of the proposed methodology was demonstrated through its application to a residential dataset in Madeira, Portugal, augmented with weather data sourced from SolCast. Full article
(This article belongs to the Topic Smart Energy Systems, 2nd Edition)
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23 pages, 7146 KiB  
Review
Photothermal Mineral-Based Composite Phase Change Materials for Direct Solar Energy Utilization: A State-of-the-Art Review
by Yunan Mu, Libing Liao and Xiaobin Gu
Energies 2025, 18(5), 1257; https://doi.org/10.3390/en18051257 - 4 Mar 2025
Viewed by 833
Abstract
Solar energy, the most promising renewable energy, suffers from intermittency and discontinuity. Phase change material (PCM)-based energy storage technology can mitigate this issue and substantially improve the utilization efficiency of solar energy. However, most PCMs have a low photothermal conversion capacity and are [...] Read more.
Solar energy, the most promising renewable energy, suffers from intermittency and discontinuity. Phase change material (PCM)-based energy storage technology can mitigate this issue and substantially improve the utilization efficiency of solar energy. However, most PCMs have a low photothermal conversion capacity and are prone to leaks. To address these two key issues of PCMs, fine modification and mineral encapsulation have been employed and demonstrated to be effective methods. This review summarizes the structure of mineral materials and discusses the corresponding encapsulation techniques and preparation methods for mineral-based composite PCMs. Based on this, we focus on reviewing methods for enhancing the photothermal conversion performance of mineral-based PCMs and explore their underlying mechanisms. Furthermore, we present practical application cases of photothermal mineral-based composite PCMs, analyzing their potential in photothermal applications. Finally, we discuss the challenges encountered during the synthesis, modification, and application processes of photothermal mineral-based composite PCMs, providing insights into future directions for the efficient utilization of solar energy. Full article
(This article belongs to the Section A: Sustainable Energy)
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30 pages, 30213 KiB  
Review
Development of Ammonia Combustion Technology for NOx Reduction
by Hossein Ali Yousefi Rizi and Donghoon Shin
Energies 2025, 18(5), 1248; https://doi.org/10.3390/en18051248 - 4 Mar 2025
Cited by 1 | Viewed by 1195
Abstract
This study comprehensively reviewed the engineering theories and technologies required for using ammonia as a fuel. The slow reaction rate and high NOx emissions of ammonia remain challenging issues with existing combustion technologies. Accordingly, the causes of these problems with ammonia were analyzed [...] Read more.
This study comprehensively reviewed the engineering theories and technologies required for using ammonia as a fuel. The slow reaction rate and high NOx emissions of ammonia remain challenging issues with existing combustion technologies. Accordingly, the causes of these problems with ammonia were analyzed and the results of research aimed at solving these issues and commercializing ammonia combustion were examined to explore future directions for the development of ammonia combustion technology. The equivalence ratio (ER) emerged as the most important factor, closely related to operational stability and NOx emissions. Various combustion technologies, such as staged combustion and flameless combustion, have been attempted, but NOx emissions remain high at overall ER < 1, necessitating post-treatment processes. The internal recirculation of combustion gases is a key technology that enhances the stability of ammonia combustion, and its extreme case, flameless combustion technology, is predicted to form stable ammonia combustion. This is related to supplying the radicals that are lacking in the pure ammonia combustion process through the recirculation of combustion gases. By utilizing this, if the stability of ammonia combustion is secured and staged ER control technology is established, it is believed that the commercialization of pure ammonia combustion technology will be possible in the future. Full article
(This article belongs to the Collection Feature Papers in Energy, Environment and Well-Being)
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18 pages, 7897 KiB  
Article
The Dynamic Process of CO2 Leakage Along Wellbores Under Different Sequestration Conditions
by Baolei Zhu, Tianfu Xu, Xi Zhang, Chenglong Zhang and Guanhong Feng
Energies 2025, 18(5), 1237; https://doi.org/10.3390/en18051237 - 3 Mar 2025
Viewed by 568
Abstract
Abandoned production and monitoring wells in depleted oil and gas fields can readily serve as primary leakage pathways for stored CO2. The temperature, pressure conditions around the wellbore bottom, and CO2 concentration influence the phase behavior of CO2 during [...] Read more.
Abandoned production and monitoring wells in depleted oil and gas fields can readily serve as primary leakage pathways for stored CO2. The temperature, pressure conditions around the wellbore bottom, and CO2 concentration influence the phase behavior of CO2 during leakage. This study establishes a 3D wellbore–reservoir coupled model using CO2 injection data from 1 December 2009, in the DAS area, eastern Cranfield oilfield, Mississippi, USA, to analyze the dynamic evolution of CO2 leakage along wellbores. Simulations are conducted using the collaboration of ECO2M and ECO2N v2.0 modules. The study examines leakage regimes under varying distances from the injection well and different reservoir temperatures. The results indicate that CO2 phase changes occur primarily in wells near the injection point or under high-pressure and high CO2 saturation conditions, usually with a short leakage period due to ice formation at the wellhead. In areas with low CO2 saturation, prolonged leakage periods lead to significant pressure drops at the bottom, as well as the temperature as a result of the Joule–Thomson effect. Lower reservoir temperatures facilitate smoother and more gradual leakage. These findings provide a theoretical foundation for ensuring the safe implementation of CCUS projects and offer insights into the mechanical explanation of CO2 geyser phenomena. Full article
(This article belongs to the Section B3: Carbon Emission and Utilization)
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27 pages, 2865 KiB  
Review
Review of Selected PCMs and Their Applications in the Industry and Energy Sector
by Łukasz Mika, Ewelina Radomska, Karol Sztekler, Andrzej Gołdasz and Wiesław Zima
Energies 2025, 18(5), 1233; https://doi.org/10.3390/en18051233 - 3 Mar 2025
Cited by 1 | Viewed by 1165
Abstract
The growing global energy demand, coupled with environmental concerns, necessitates the development of efficient energy storage technologies. Phase Change Materials (PCMs) have emerged as a promising solution for thermal energy storage (TES) due to their ability to store and release latent heat during [...] Read more.
The growing global energy demand, coupled with environmental concerns, necessitates the development of efficient energy storage technologies. Phase Change Materials (PCMs) have emerged as a promising solution for thermal energy storage (TES) due to their ability to store and release latent heat during phase transitions. This review provides a comprehensive analysis of PCMs, exploring their classifications based on phase transition types, chemical compositions, and thermophysical properties. Additionally, the review highlights advancements in developing organic, inorganic, and metallic PCMs and evaluates their potential applications in sectors such as solar energy, construction, and automotive industries. Methodologies include a detailed examination of the strengths, limitations, and solutions to challenges such as low thermal conductivity, phase separation, and supercooling. The results summarize the diverse applications of PCMs, emphasizing their critical role in enhancing energy efficiency and sustainability. The review concludes with recommendations for overcoming current limitations and future directions for PCM research and technology integration across various industries. Full article
(This article belongs to the Special Issue Thermal Energy Storage Systems Modeling and Experimentation)
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18 pages, 842 KiB  
Article
Customizable Life Cycle Cost Methodology for Ammonia Fuel Storage: Enhancing Adoptability Across Diverse Onboard Arrangements
by Evanthia Kostidi and Dimitrios Lyridis
Energies 2025, 18(5), 1228; https://doi.org/10.3390/en18051228 - 3 Mar 2025
Viewed by 657
Abstract
While ammonia offers several benefits as an alternative fuel, its adoption poses significant technical and economic challenges, particularly with respect to onboard storage and handling. To facilitate the large-scale deployment of ammonia in marine applications, there is a critical need to develop a [...] Read more.
While ammonia offers several benefits as an alternative fuel, its adoption poses significant technical and economic challenges, particularly with respect to onboard storage and handling. To facilitate the large-scale deployment of ammonia in marine applications, there is a critical need to develop a robust methodology for assessing the life cycle costs of ammonia storage systems on vessels, either new-build and retrofit installations. With a robust life cycle cost analysis (LCCA) methodology, the maritime industry can better evaluate the feasibility of onboard ammonia storage systems, paving the way for their large-scale adoption and supporting global efforts to reduce carbon emissions. Given that ammonia is a relatively new marine fuel, this work addresses the current gap in knowledge by offering a structured approach to evaluating the costs across the entire life cycle of an onboard ammonia storage system, including design, construction, operation, maintenance, and end-of-life decommissioning. This methodology was developed with a high degree of flexibility to accommodate uncertainties in both technological alternatives and cost estimation. This work offers significant contributions to both academia and industry by establishing a replicable and adaptable LCCA framework for assessing storage solutions. Full article
(This article belongs to the Special Issue Green Hydrogen and Fuel Cells: Heading Toward a Sustainable Energy Future)
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29 pages, 8593 KiB  
Review
Functionalization Strategies of MXene Architectures for Electrochemical Energy Storage Applications
by Shude Liu, Huilin Zhang, Jieming Chen, Xue Peng, Yafei Chai, Xian Shao, Yi He, Xiaoqiang Wang and Bin Ding
Energies 2025, 18(5), 1223; https://doi.org/10.3390/en18051223 - 2 Mar 2025
Cited by 1 | Viewed by 1833
Abstract
MXene, an emerging class of two-dimensional materials, has garnered significant attention in electrochemical energy storage applications due to its high specific surface area, tunable surface functional groups, excellent electrical conductivity, and mechanical stability. However, their practical application in energy storage devices remains challenged [...] Read more.
MXene, an emerging class of two-dimensional materials, has garnered significant attention in electrochemical energy storage applications due to its high specific surface area, tunable surface functional groups, excellent electrical conductivity, and mechanical stability. However, their practical application in energy storage devices remains challenged by issues such as the stacking of their layered structure, surface degradation, and limited ion diffusion properties. Functionalization has emerged as a key strategy to enhance the performance of MXene materials. By modulating surface functional groups, doping with various elements, and integrating with other materials, researchers have significantly improved the electrical conductivity, chemical stability, ion transport properties, and mechanical strength of MXenes. This review provides a comprehensive overview of MXene materials, categorizing them and highlighting their advantages in electrochemical energy storage applications. It also examines recent advancements in MXene preparation and optimized synthesis strategies. In-depth discussions are presented on the functionalization of MXenes and their applications in energy storage devices, including supercapacitors, lithium-ion batteries, and sodium-ion batteries. Finally, the review concludes with a summary of the practical applications of MXenes and explores future research directions, aiming to guide further developments in the energy storage field. Full article
(This article belongs to the Section D: Energy Storage and Application)
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35 pages, 2572 KiB  
Review
A Review of Condition Monitoring of Permanent Magnet Synchronous Machines: Techniques, Challenges and Future Directions
by Alexandros Sergakis, Marios Salinas, Nikolaos Gkiolekas and Konstantinos N. Gyftakis
Energies 2025, 18(5), 1177; https://doi.org/10.3390/en18051177 - 27 Feb 2025
Cited by 3 | Viewed by 1360
Abstract
This paper focuses on the latest advancements in diagnosing faults in Permanent Magnet Synchronous Machines (PMSMs), with particular attention paid to demagnetization, inter-turn short circuits (ITSCs), and eccentricity faults. As PMSMs play an important role in electric vehicles, renewable energy systems and aerospace [...] Read more.
This paper focuses on the latest advancements in diagnosing faults in Permanent Magnet Synchronous Machines (PMSMs), with particular attention paid to demagnetization, inter-turn short circuits (ITSCs), and eccentricity faults. As PMSMs play an important role in electric vehicles, renewable energy systems and aerospace applications, ensuring their reliability is more important than ever. This work examines widely applied methods like Motor Current Signature Analysis (MCSA) and flux monitoring, alongside more recent approaches such as time-frequency analysis, observer-based techniques and machine learning strategies. These methods are discussed in terms of strengths/weaknesses, challenges and suitability for different operating conditions. The review also highlights the importance of experimental validations to connect theoretical research with real-world applications. By exploring potential synergies between these diagnostic methods, the paper outlines ways to improve fault detection accuracy and machine reliability. It concludes by identifying future research directions, such as developing real-time diagnostics, enhancing predictive maintenance and refining sensor and computational technologies, aiming to make PMSMs more robust and fault-tolerant in demanding environments. In addition, the discussion highlights how partial demagnetization or ITSC faults may propagate if not diagnosed promptly, necessitating scalable and efficient multi-physics approaches. Finally, emphasis is placed on bridging theoretical advancements with industrial-scale implementations to ensure seamless integration into existing machine drive systems. Full article
(This article belongs to the Section A: Sustainable Energy)
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31 pages, 1595 KiB  
Article
Assessment of Hydrogen Storage and Pipelines for Hydrogen Farm
by Esmaeil Alssalehin, Paul Holborn and Pericles Pilidis
Energies 2025, 18(5), 1167; https://doi.org/10.3390/en18051167 - 27 Feb 2025
Cited by 1 | Viewed by 865
Abstract
This paper presents a thorough initial evaluation of hydrogen gaseous storage and pipeline infrastructure, emphasizing health and safety protocols as well as capacity considerations pertinent to industrial applications. As hydrogen increasingly establishes itself as a vital energy vector within the transition towards low-carbon [...] Read more.
This paper presents a thorough initial evaluation of hydrogen gaseous storage and pipeline infrastructure, emphasizing health and safety protocols as well as capacity considerations pertinent to industrial applications. As hydrogen increasingly establishes itself as a vital energy vector within the transition towards low-carbon energy systems, the formulation of effective storage and transportation solutions becomes imperative. The investigation delves into the applications and technologies associated with hydrogen storage, specifically concentrating on compressed hydrogen gas storage, elucidating the principles underlying hydrogen compression and the diverse categories of hydrogen storage tanks, including pressure vessels specifically designed for gaseous hydrogen containment. Critical factors concerning hydrogen gas pipelines are scrutinized, accompanied by a review of appropriate compression apparatus, types of compressors, and particular pipeline specifications necessary for the transport of both hydrogen and oxygen generated by electrolysers. The significance of health and safety in hydrogen systems is underscored due to the flammable nature and high diffusivity of hydrogen. This paper defines the recommended health and safety protocols for hydrogen storage and pipeline operations, alongside exemplary practices for the effective implementation of these protocols across various storage and pipeline configurations. Moreover, it investigates the function of oxygen transport pipelines and the applications of oxygen produced from electrolysers, considering the interconnected safety standards governing hydrogen and oxygen infrastructure. The conclusions drawn from this study facilitate the advancement of secure and efficient hydrogen storage and pipeline systems, thereby furthering the overarching aim of scalable hydrogen energy deployment within both energy and industrial sectors. Full article
(This article belongs to the Special Issue Hydrogen Economy in the Global Energy Transition)
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17 pages, 3615 KiB  
Article
Improvement in Energy Self-Sufficiency in Residential Buildings Using Photovoltaic Thermal Plants, Heat Pumps, and Electrical and Thermal Storage
by Antonio Gagliano, Giuseppe Marco Tina and Stefano Aneli
Energies 2025, 18(5), 1159; https://doi.org/10.3390/en18051159 - 27 Feb 2025
Cited by 1 | Viewed by 635
Abstract
Promoting complete decarbonization by entrusting the energy supply through renewable sources (wind, photovoltaic, solar thermal, etc.) is one of the key strategies in the building sector. However, renewable energy’s intermittent and space–time mismatch characteristics pose challenges to its compatibility with the power grid. [...] Read more.
Promoting complete decarbonization by entrusting the energy supply through renewable sources (wind, photovoltaic, solar thermal, etc.) is one of the key strategies in the building sector. However, renewable energy’s intermittent and space–time mismatch characteristics pose challenges to its compatibility with the power grid. Challenges can be mitigated by introducing thermal and electrical storage to increase the self-consumption of renewable energy in the buildings. This work proposes a comparison between different energy systems equipped with a heat pump, solar plant (photovoltaic or photovoltaic thermal), and thermal and electrical storage. All year-round performances of the different energy system configurations have been simulated using the TRNSYS 17.2 software. The energy analyses revealed that the energy system equipped with a photovoltaic plant, when incorporating the two storages, improves self-consumption (Rsc) from 34.1% to 69.4 and self-sufficiency (Dss) from 27.9% to 59.9%, respectively. Additionally, the energy system equipped with photovoltaic thermal collectors and both storages further improve the system performance; an Rsc of 96.2% and Dss of 86.9% are attained. These results demonstrate that the previous energy system configuration can facilitate the near attainment of net-zero energy buildings. Furthermore, the proposed energy system is characterized by a minimal energy imbalance between the building’s energy demand and the energy produced, thereby reducing the need for energy exchange with the electrical grid. Full article
(This article belongs to the Special Issue Research on Energy Efficiency and Energy Conservation: Current State and toward a Sustainable Future)
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24 pages, 1170 KiB  
Review
A Review on Biohydrogen Production Through Dark Fermentation, Process Parameters and Simulation
by Babak Mokhtarani, Jafar Zanganeh and Behdad Moghtaderi
Energies 2025, 18(5), 1092; https://doi.org/10.3390/en18051092 - 24 Feb 2025
Viewed by 1827
Abstract
This study explores biohydrogen production through dark fermentation, an alternative supporting sustainable hydrogen generation. Dark fermentation uses organic waste under anaerobic conditions to produce hydrogen in the absence of light. Key process parameters affecting hydrogen yield, including substrate type, microorganism selection, and fermentation [...] Read more.
This study explores biohydrogen production through dark fermentation, an alternative supporting sustainable hydrogen generation. Dark fermentation uses organic waste under anaerobic conditions to produce hydrogen in the absence of light. Key process parameters affecting hydrogen yield, including substrate type, microorganism selection, and fermentation conditions, were examined. Various substrates, such as organic wastes and carbohydrates, were tested, and the role of anaerobic and facultative anaerobic microorganisms in optimizing the process was analyzed. The research also focused on factors such as pH, temperature, and hydraulic retention time to enhance yields and scalability. Additionally, the study modelled the process using ASPEN Plus software 14. This simulation identifies the bottle necks of this process. Due to the lack of available data, modelling and simulation of the described processes in ASPEN Plus required certain approximations. The simulation provides insight into the key challenges that need to be addressed for hydrogen production. Future research should indeed explore current limitations, such as substrate efficiency, process scalability, and cost-effectiveness, as well as potential advancements like the genetic engineering of microbial strains and improved bioreactor designs. Full article
(This article belongs to the Special Issue Sustainable Development of Fuel Cells and Hydrogen Technologies)
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28 pages, 3491 KiB  
Article
Renewable Energy, Resilience, Digitalization, and Industrial Policies in Seaborne Transport
by Elisa Barbieri and Luigi Capoani
Energies 2025, 18(5), 1089; https://doi.org/10.3390/en18051089 - 24 Feb 2025
Cited by 1 | Viewed by 919
Abstract
This paper delves into sustainability and energy policies influencing the governance and dynamics of global maritime trade. Resilience and sustainability are also discussed, along with the obstacles encountered and strategies to overcome them. The analysis underscores the importance of developing long-term strategies and [...] Read more.
This paper delves into sustainability and energy policies influencing the governance and dynamics of global maritime trade. Resilience and sustainability are also discussed, along with the obstacles encountered and strategies to overcome them. The analysis underscores the importance of developing long-term strategies and participatory processes, focusing on government involvement in promoting structural changes towards a more sustainable seaborne transport system. Part of our research is also dedicated to outlining the different factors influencing this industry among different continents, highlighting the need for increasingly unified governance frameworks internationally. By incorporating resilience theory and new technologies, with a high potential in terms of GHG emission reduction, governments and firms can better engage stakeholders, ensure business resilience, and address climate change risks. This study concludes that ports have significant power in driving structural change, and modernization across various areas—such as digitalization, energy policies, safety, green fuels, environmental sustainability, and effective coordination—is essential for their continued development. Full article
(This article belongs to the Special Issue The Interplay Between Technologies and Energy Policies for Reducing the Environmental Impact of Transportation: Scenarios and Case Studies)
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15 pages, 6486 KiB  
Article
Optimal Vehicle-to-Grid Charge Scheduling for Electric Vehicles Based on Dynamic Programming
by Heeyun Lee, Hyunjoong Kim, Hyewon Kim and Hyunsup Kim
Energies 2025, 18(5), 1109; https://doi.org/10.3390/en18051109 - 24 Feb 2025
Cited by 1 | Viewed by 567
Abstract
Recently, as the market share of electric vehicles (EVs) has increased, how to handle the increased electricity demand for EV charging in the power grid and how to use EV batteries from a grid-operating aspect have become more important. Also, from the perspective [...] Read more.
Recently, as the market share of electric vehicles (EVs) has increased, how to handle the increased electricity demand for EV charging in the power grid and how to use EV batteries from a grid-operating aspect have become more important. Also, from the perspective of individual EVs, Vehicle-to-Grid (V2G) technologies that reduce the cost for each vehicle’s charging in conjunction with the power grid are significant. In this paper, the V2G control problem at the individual vehicle level is studied using a Dynamic Programming (DP) algorithm that considers EVs’ charging efficiency. The DP algorithm is developed to generate an optimized charging/discharging power profile that minimizes electricity costs, while satisfying the constraints of the initial and final battery states of charge, for given a time-of-use electricity price. To show the effectiveness of the proposed algorithm, simulation is conducted for three different charging scenarios (unidirectional charging, bidirectional charging, and unidirectional charging with cost variations based on electricity usage), and the results showed that DP can achieve significant cost savings of about 30% compared to the normal charging method. Also, the result of DP is compared with that of Linear Programming, demonstrating that DP outperforms Linear Programming in cost savings for the V2G control problem. Full article
(This article belongs to the Special Issue Electric Waves to Future Mobility)
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33 pages, 6125 KiB  
Review
DC Microgrid Deployments and Challenges: A Comprehensive Review of Academic and Corporate Implementations
by Adewale W. Adegboyega, Saeed Sepasi, Harun Or Rashid Howlader, Brian Griswold, Marc Matsuura and Leon R. Roose
Energies 2025, 18(5), 1064; https://doi.org/10.3390/en18051064 - 22 Feb 2025
Cited by 2 | Viewed by 2002
Abstract
DC microgrids are revolutionizing energy systems by offering efficient, reliable, and sustainable solutions to modern power grid challenges. By directly integrating renewable energy sources and eliminating the inefficiencies of AC-DC conversion, these systems simplify energy distribution and enhance performance in critical applications such [...] Read more.
DC microgrids are revolutionizing energy systems by offering efficient, reliable, and sustainable solutions to modern power grid challenges. By directly integrating renewable energy sources and eliminating the inefficiencies of AC-DC conversion, these systems simplify energy distribution and enhance performance in critical applications such as data centers, electric vehicle charging, and telecommunications. This review paper comprehensively examines the design, implementation, and performance of DC microgrids in real-world settings. Key components, including distributed energy resources (DERs), energy storage systems (ESSs), and control strategies, are analyzed to highlight their roles in ensuring reliability and operational efficiency. This review also explores the challenges facing DC microgrids, such as stability issues, protection mechanisms, and high initial costs, while offering insights into advanced control strategies and modular designs to overcome these obstacles. Through an evaluation of global case studies, this article bridges the gap between theoretical research and practical deployment and also demonstrates how DC microgrids can enhance energy efficiency, support sustainable power generation, and provide resilience in various applications. The findings highlight the potential of DC microgrids as a cornerstone of future energy systems, enabling clean, reliable, and decentralized energy solutions. Full article
(This article belongs to the Special Issue Advances in Power Distribution Systems)
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42 pages, 4280 KiB  
Review
Power Transformers Cooling Design: A Comprehensive Review
by Sandra Sorte, André Ferreira Monteiro, Diogo Ventura, Alexandre Salgado, Mónica S. A. Oliveira and Nelson Martins
Energies 2025, 18(5), 1051; https://doi.org/10.3390/en18051051 - 21 Feb 2025
Cited by 1 | Viewed by 1113
Abstract
Efficient cooling technologies for power transformers are critical to modern power systems, ensuring reliability, performance, and AN extended lifespan. This review systematically analyses advancements, challenges, and opportunities in cooling systems for power transformers. Oil-immersed transformers, widely used due to their superior insulation and [...] Read more.
Efficient cooling technologies for power transformers are critical to modern power systems, ensuring reliability, performance, and AN extended lifespan. This review systematically analyses advancements, challenges, and opportunities in cooling systems for power transformers. Oil-immersed transformers, widely used due to their superior insulation and effective cooling, require efficient thermal management to prevent overheating and ensure operational stability. This review evaluates key cooling strategies across oil-natural air-natural (ONAN), oil-natural air-forced (ONAF), oil-directed air-forced (ODAF), and oil-forced air-forced (OFAF) systems. It highlights innovations in radiator design, such as top-mounted radiators and chimney caps, and explores sustainable alternatives, including biodegradable esters, nanofluids, and hybrid ventilation methods. Advanced computational tools like Computational Fluid Dynamics (CFD) and artificial intelligence (AI), particularly neural networks, are identified as transformative for optimising cooling performance, predicting thermal behaviour, and enabling real-time monitoring. Despite progresses, challenges persist in radiator optimisation, airflow dynamics, and scalability of innovative cooling methods. By offering a comprehensive review and identifying critical areas for improvement, this study provides a foundation for developing cost-effective, reliable, and environmentally sustainable cooling systems, aligning with the growing demand for efficient energy infrastructure. Full article
(This article belongs to the Special Issue Energy, Electrical and Power Engineering: 3rd Edition)
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35 pages, 11124 KiB  
Review
Numerical and Experimental Study of Fluid Flow and Heat Transfer in Porous Media: A Review Article
by Ramin Ranjbarzadeh and Giuseppe Sappa
Energies 2025, 18(4), 976; https://doi.org/10.3390/en18040976 - 18 Feb 2025
Cited by 3 | Viewed by 1478
Abstract
Fluid flow and heat transfer in porous media have been extensively studied due to their importance in numerous industrial and environmental applications. This review provides a comprehensive analysis of numerical and experimental approaches, presenting a multiscale perspective that bridges molecular, pore, and macroscopic [...] Read more.
Fluid flow and heat transfer in porous media have been extensively studied due to their importance in numerous industrial and environmental applications. This review provides a comprehensive analysis of numerical and experimental approaches, presenting a multiscale perspective that bridges molecular, pore, and macroscopic levels. This study emphasizes the importance of understanding the underlying principles governing these processes, as this knowledge is essential for optimizing and innovating applications ranging from energy systems to environmental engineering. The review synthesizes key theoretical frameworks, including Darcy’s law, the Brinkman equation, and volume-averaging methods, offering a robust foundation for interpreting complex interactions in porous media. A novel aspect of this work is the integration of experimental and numerical insights to address challenges such as heterogeneity, anisotropy, and scale effects, demonstrating their complementary roles in advancing this field. Additionally, the review highlights emerging methodologies, including advanced pore-scale modeling, the lattice Boltzmann method, and machine learning, as transformative tools for overcoming existing limitations and exploring future directions. By identifying critical knowledge gaps and proposing innovative solutions, this article serves as a vital resource for researchers and practitioners, fostering interdisciplinary approaches and paving the way for cutting-edge advancements in the study of fluid flow and heat transfer in porous media. Full article
(This article belongs to the Collection Advances in Heat Transfer Enhancement)
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22 pages, 1768 KiB  
Article
A Novel Integrated Biorefinery for the Valorization of Residual Cardoon Biomass: Overview of Technologies and Process Simulation
by Vittoria Fatta, Aristide Giuliano, Maria Teresa Petrone, Francesco Nanna, Antonio Villone, Donatella Barisano, Roberto Albergo, Federico Liuzzi, Diego Barletta and Isabella De Bari
Energies 2025, 18(4), 973; https://doi.org/10.3390/en18040973 - 18 Feb 2025
Viewed by 557
Abstract
Lignocellulosic biomass is currently widely used in many biorefining processes. The full exploitation of biomass from uncultivated or even marginal lands for the production of biobased chemicals has deserved huge attention in the last few years. Among the sustainable biomass-based value chains, cardoon [...] Read more.
Lignocellulosic biomass is currently widely used in many biorefining processes. The full exploitation of biomass from uncultivated or even marginal lands for the production of biobased chemicals has deserved huge attention in the last few years. Among the sustainable biomass-based value chains, cardoon crops could be a feedstock for biorefineries as they can grow on marginal lands and be used as raw material for multipurpose exploitation, including seeds, roots, and epigeous lignocellulosic solid residue. This work focused on the technical analysis of a novel integrated flowsheet for the exploitation of the lignocellulosic fraction through the assessment of thermochemical, biochemical, and extractive technologies and processes. In particular, high-yield thermochemical processes (gasification), innovative biotechnological processes (syngas fermentation to ethanol), and extractive/catalyzed processes for the valorization of cardoon roots to FDCA and residual solid biomass were modeled and simulated. Inulin conversion to 2,5-Furandicarboxylic acid was the main conversion route taken into consideration. Finally, the novel process flowsheet, treating 130,000 t/y of residual biomass and integrating all proposed technologies, was modeled and assessed using process simulation tools to achieve overall mass and energy balances for comparison with alternative options. The results indicated that cardoon biorefining through the proposed flowsheet can produce, per 1000 tons of input dry biomass, 211 kg of 2,5-Furandicarboxylic acid and 140 kg of ethanol through biomass gasification followed by syngas fermentation. Furthermore, a pre-feasibility analysis was conducted, revealing significant and potentially disruptive results in terms of environmental impact (with 40 ktCO2eq saved) and economic feasibility (with an annual gross profit of EUR 30 M/y). Full article
(This article belongs to the Section A4: Bio-Energy)
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17 pages, 1677 KiB  
Article
Assessing the Energy Footprint of Desalination Technologies and Minimal/Zero Liquid Discharge (MLD/ZLD) Systems for Sustainable Water Protection via Renewable Energy Integration
by Argyris Panagopoulos
Energies 2025, 18(4), 962; https://doi.org/10.3390/en18040962 - 17 Feb 2025
Cited by 1 | Viewed by 1142
Abstract
Water scarcity necessitates desalination technologies, yet their high energy demands and brine disposal challenges hinder sustainability. This research study evaluates the energy footprint and carbon emissions of thermal- and membrane-based desalination technologies, alongside Minimal/Zero Liquid Discharge (MLD/ZLD) frameworks, with a focus on renewable [...] Read more.
Water scarcity necessitates desalination technologies, yet their high energy demands and brine disposal challenges hinder sustainability. This research study evaluates the energy footprint and carbon emissions of thermal- and membrane-based desalination technologies, alongside Minimal/Zero Liquid Discharge (MLD/ZLD) frameworks, with a focus on renewable energy source (RES) integration. Data revealed stark contrasts: thermal-based technologies like osmotic evaporation (OE) and brine crystallizers (BCr) exhibit energy intensities of 80–100 kWh/m3 and 52–70 kWh/m3, respectively, with coal-powered carbon footprints reaching 72–100 kg CO2/m3. Membrane-based technologies, such as reverse osmosis (RO) (2–6 kWh/m3) and forward osmosis (FO) (0.8–13 kWh/m3), demonstrate lower emissions (1.8–11.7 kg CO2/m3 under coal). Transitioning to RES reduces emissions by 90–95%, exemplified by renewable energy-powered RO (0.1–0.3 kg CO2/m3). However, scalability barriers persist, including high capital costs, RES intermittency, and technological immaturity in emerging systems like osmotically assisted RO (OARO) and membrane distillation (MD). This research highlights RES-driven MLD/ZLD systems as pivotal for aligning desalination with global climate targets, urging innovations in energy storage, material robustness, and circular economy models to secure water resource resilience. Full article
(This article belongs to the Special Issue The Use of Renewable Energy in the Protection and Restoration of Surface Waters and Wetlands)
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23 pages, 600 KiB  
Review
Economic and Technological Challenges in Zero-Emission Strategies for Energy Companies
by Piotr F. Borowski
Energies 2025, 18(4), 898; https://doi.org/10.3390/en18040898 - 13 Feb 2025
Cited by 1 | Viewed by 699
Abstract
The energy transition requires substantial financial investments and the adoption of innovative technological solutions. The aim of this paper is to analyze the economic and technological aspects of implementing zero-emission strategies as a key component of the transition toward a carbon-neutral economy. The [...] Read more.
The energy transition requires substantial financial investments and the adoption of innovative technological solutions. The aim of this paper is to analyze the economic and technological aspects of implementing zero-emission strategies as a key component of the transition toward a carbon-neutral economy. The study assesses the costs, benefits, and challenges of these strategies, with a particular focus on wind farms and nuclear power, including small modular reactors (SMRs). The paper presents an in-depth examination of key examples, including onshore and offshore wind farms, as well as nuclear energy from both large-scale and small modular reactors. It highlights their construction and operating costs, associated benefits, and challenges. The investment required to generate 1 MW of energy varies significantly depending on the technology: onshore wind farms range from $1,300,000 to $2,100,000, offshore wind farms from $3,000,000 to $5,500,000, traditional nuclear power plants from $3,000,000 to $5,000,000, while small modular reactors (SMRs) require between $5,000,000 and $10,000,000 per MW. The discussion underscores the critical role of wind farms in diversifying renewable energy sources while addressing the high capital requirements and technical complexities of nuclear power, including both traditional large-scale reactors and emerging SMRs. By evaluating these energy solutions, the article contributes to a broader understanding of the economic and technological challenges essential for advancing a sustainable energy future. Full article
(This article belongs to the Special Issue Economic, Financial, and Social Aspects of Green Energy Transformation)
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23 pages, 2153 KiB  
Article
Is the Digital Divide Inhibiting Urban Energy Transitions?—Evidence from China
by Zhilun Jiao and Zixuan Xia
Energies 2025, 18(4), 905; https://doi.org/10.3390/en18040905 - 13 Feb 2025
Cited by 1 | Viewed by 635
Abstract
The swift advancement of information technology has significantly impacted the energy transition. Being the largest energy consumer globally, China’s acceleration of the urban energy transition will promote sustainable development and pave the way for future development. This study examines the impact of the [...] Read more.
The swift advancement of information technology has significantly impacted the energy transition. Being the largest energy consumer globally, China’s acceleration of the urban energy transition will promote sustainable development and pave the way for future development. This study examines the impact of the digital divide between cities regarding the energy transition by using panel data for 271 Chinese cities from 2006 to 2021. We found the following results. (1) The digital divide has an inhibitory effect on the energy transition of cities, hindering their development towards green and low-carbon development. (2) Further analyses found that the negative impact of the digital divide on energy transition can be effectively mitigated by strengthening urban infrastructure construction, promoting emerging technological innovation, and cultivating and attracting talent in the digital industry. (3) The results of the subsample analyses show that the inhibitory effect of the digital divide on energy transition is more significant in densely populated cities, economically and technologically developed cities, and non-resource-based cities. The above findings hold significant practical implications for overcoming the digital divide and the stagnation of energy transition, and for the scientific implementation of China’s “Carbon Neutrality” initiative. Full article
(This article belongs to the Special Issue Advances in Energy Transition to Achieve Carbon Neutrality)
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33 pages, 7876 KiB  
Article
Methods for the Investigation and Mitigation of Conducted Differential-Mode Electromagnetic Interference in Commercial Electrical Vehicles
by Per Widek and Mats Alaküla
Energies 2025, 18(4), 859; https://doi.org/10.3390/en18040859 - 12 Feb 2025
Viewed by 744
Abstract
One of the main challenges as the market for fully commercial electrified vehicles quickly expands is predicting the electromagnetic interference (EMI) in traction voltage systems (TVSs) in differential mode (DM) and common mode (CM). The number of subsystems connected to vehicle TVSs is [...] Read more.
One of the main challenges as the market for fully commercial electrified vehicles quickly expands is predicting the electromagnetic interference (EMI) in traction voltage systems (TVSs) in differential mode (DM) and common mode (CM). The number of subsystems connected to vehicle TVSs is increasing, and thus, so are the electromagnetic compatibility (EMC) requirements. These requirements should make sure that neither the function nor lifetime of any source or load is affected by another, but experience shows that they are often insufficient. The purpose of this article is to show how circuit simulations can complement these requirements and that a generalized artificial network/line impedance stabilization network (LISN) is insufficient to correctly predict the EMI situation of a real vehicle. This article presents a method for complexity reduction in TVS DM simulations and a comparison with the usage of LISN to predict the EMI between subsystems; the article also addresses how to mitigate the EMI with DM filters for the subsystems. The proposed method creates a foundation for a faster and safer development process. The simulation model’s development includes a traction battery and TVS subsystems. It is found that a standardized LISN does not reflect the behavior of a commercial TVS and cannot be used solely to judge if a subsystem will operate as intended within a TVS without creating EMI. A change in switching frequency in the DUT can cause severe resonance between TVS subsystems, but this is not seen with a LISN. The conclusion of the article is that LISN can provide a false sense of security and that calibrated simulation models of a complete TVS are necessary to predict the behavior in that TVS; this study also highlights the importance of using DM filters to ensure protection against resonance frequencies. Full article
(This article belongs to the Special Issue Novel Applications of Power Converters for Energy Storage and Grid Integration)
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