Energies

16 pages, 8471 KiB

Open AccessArticle

Study on Purge Strategy of Hydrogen Supply System with Dual Ejectors for Fuel Cells

by Yueming Liang and Changqing Du

Energies 2025, 18(9), 2168; https://doi.org/10.3390/en18092168 - 23 Apr 2025

The exhaust purge on the anode side is a critical step in the operation of fuel cell systems, and optimizing the exhaust interval time is essential for enhancing stack efficiency and hydrogen utilization. This paper proposed a method to determine the purge strategy [...] Read more.

The exhaust purge on the anode side is a critical step in the operation of fuel cell systems, and optimizing the exhaust interval time is essential for enhancing stack efficiency and hydrogen utilization. This paper proposed a method to determine the purge strategy of hydrogen supply system based on theoretical and simulation analysis. To investigate the impact of anode purge strategy on the performance of automotive fuel cells, a model of a 100 kW fuel cell stack and a dual-ejector hydrogen supply system was developed in MATLAB/Simulink(R2022b) using principles of fluid dynamics, simulation, and experimental data. This model effectively captures the accumulation and exhaust of hydrogen, nitrogen, and vapor within the anode. Simulations were conducted under seven different exhaust interval times at varying current densities to study the effect of exhaust interval on the performance of the fuel cell. The results indicate that for a 100 kW fuel cell, the exhaust interval time should be controlled within 25 s and should decrease as the current density increases. At low current density, increasing the exhaust interval has a more significant effect on improving hydrogen utilization. At high current density, reducing the exhaust interval helps maintain a stable hydrogen excess ratio and shortens the time required for the output voltage to reach a stable state. Full article

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

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19 pages, 5281 KiB

Open AccessArticle

Bidirectional Energy Transfer Between Electric Vehicle, Home, and Critical Load

by Ștefan-Andrei Lupu and Dan Floricău

Energies 2025, 18(9), 2167; https://doi.org/10.3390/en18092167 - 23 Apr 2025

Abstract

In the transition to a sustainable energy system, the integration of electric vehicles into residential energy systems is an innovative solution for increasing energy resilience and optimizing electricity consumption. This article presents a bidirectional AC/DC converter capable of charging the electric vehicle battery [...] Read more.

In the transition to a sustainable energy system, the integration of electric vehicles into residential energy systems is an innovative solution for increasing energy resilience and optimizing electricity consumption. This article presents a bidirectional AC/DC converter capable of charging the electric vehicle battery under normal conditions, while providing power to a critical consumer in the event of a power grid outage. The simulations performed show us the functionality of this converter, demonstrating its efficiency in ensuring the continuity of supply. Full article

(This article belongs to the Special Issue Novel Applications of Power Converters for Energy Storage and Grid Integration)

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13 pages, 2333 KiB

Open AccessArticle

Optimization of Hydrogen Internal Combustion Engines Equipped with Turbocompound Technology for Enhanced Performance and Efficiency

by Pier Paolo Brancaleoni, Enrico Corti, Federico Di Prospero, Davide Di Battista, Roberto Cipollone and Vittorio Ravaglioli

Energies 2025, 18(9), 2166; https://doi.org/10.3390/en18092166 - 23 Apr 2025

Abstract

Hydrogen Internal Combustion Engines (H₂ICEs) offer significant potential in reducing the CO₂ emissions of the heavy-duty transport sector in the pursuit of the European Green Deal targets. However, the challenges associated with hydrogen energy density require advanced technologies for fuel [...] Read more.

Hydrogen Internal Combustion Engines (H₂ICEs) offer significant potential in reducing the CO₂ emissions of the heavy-duty transport sector in the pursuit of the European Green Deal targets. However, the challenges associated with hydrogen energy density require advanced technologies for fuel efficiency enhancement. Hybrid powertrains, equipped with innovative energy recovery systems, allow optimizing the engine working point while recovering otherwise wasted energy. In particular, Turbocompound (TCo) systems allow recovering the energy content in the exhaust gases, improving the overall efficiency of the powertrain. Optimizing both engine operation and TCo recovery presents a significant challenge, as it requires balancing the dynamic interaction between the engine’s combustion process and TCo (which increases backpressure). This paper presents a novel approach aimed at optimizing the performance of a hybrid hydrogen-fueled internal combustion engine by integrating a TCo system. The TCo allows extracting a 9 kW extra power peak with respect to the baseline configuration. The performance assessment of the optimized working point for series hybrid powertrains underscores the capability of the strategy to reduce hydrogen consumption up to 6.8%. Full article

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

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22 pages, 1693 KiB

Open AccessArticle

Comparative Studies of Three-Dimensional Complex Flow Field Designs in a Proton Exchange Membrane Hydrogen Fuel Cell

by Dilyan Gavrailov and Silviya Boycheva

Energies 2025, 18(9), 2165; https://doi.org/10.3390/en18092165 - 23 Apr 2025

Abstract

The performance and durability of proton-exchange membrane fuel cells (PEMFCs) are dependent on fuel flow, humidifying water, and outgoing water management. Unlike conventional flow fields with linear channels, the complex 3D flow field—featuring repeating baffles along the channel, known as the baffle design—induces [...] Read more.

The performance and durability of proton-exchange membrane fuel cells (PEMFCs) are dependent on fuel flow, humidifying water, and outgoing water management. Unlike conventional flow fields with linear channels, the complex 3D flow field—featuring repeating baffles along the channel, known as the baffle design—induces a micro-scale interface flux between the gas diffusion layer (GDL) and the flow fields. Thus, an intensive oxygen flow is created that removes excess water from the GDL, thereby improving the fuel cell efficiency. Another approach for channel design is the Turing flow field, which resembles the organization of fluid flows in natural objects such as leaves, lungs, and the blood system. This design enhances the distribution of inlet flow significantly compared with traditional designs. The present study aims to combine the advantages of both Turing and baffle flow field designs and to provide model investigations on the influence of the mixed flow field design on the efficiency of PEMFCs. It was established that the mixed design achieves the highest electrode current density of 1.2 A/cm², outperforming the other designs. Specifically, it achieves 20% improvement over the Turing design, reaching 1.0 A/cm² and generating three times more current than the baffle design, which delivers 0.4 A/cm². In contrast, the conventional serpentine designs exhibit the lowest current density. The mixed flow field design provides better oxygen utilization in the electrochemical reaction, offers optimal membrane hydration, and contributes to superior electrode current density performance. These data illustrate how flow field structure directly impacts fuel cell efficiency through enhancement of current density. Full article

(This article belongs to the Special Issue Renewable Fuels and Chemicals)

23 pages, 1932 KiB

Open AccessArticle

Tuning of ILADRC for CFB Boiler Combustion System Based on LF-DCSSA Algorithm

by Qi Wang, Chi Zhang, Aoqi Xiao, Xinchun Jia, Shikui Chen and Rongsen Fan

Energies 2025, 18(9), 2164; https://doi.org/10.3390/en18092164 - 23 Apr 2025

Abstract

Aiming at the problem that it is difficult to adjust the parameters of the controller in the circulating fluidized bed (CFB) boiler combustion system due to its multivariable and strong coupling, an improved linear active disturbance rejection controller (ILADRC) parameter tuning strategy based [...] Read more.

Aiming at the problem that it is difficult to adjust the parameters of the controller in the circulating fluidized bed (CFB) boiler combustion system due to its multivariable and strong coupling, an improved linear active disturbance rejection controller (ILADRC) parameter tuning strategy based on the Lévy flight double chaotic sparrow search algorithm (LF-DCSSA) is proposed. The LF-DCSSA algorithm is used to tune the parameters of the ILADRC controller in the multivariable coupled combustion control system of the CFB boiler built by Simulink, so that its control effect can reach the best state. The step response simulation and perturbation simulation are carried out with the theoretically tuned PID and ILADRC. The simulation results show that LF-DCSSA-ILADRC has obvious advantages in the three indexes of time–domain response, such as adjustment time, overshoot, and ITAE, which is more efficient and accurate than that of the theoretical setting, providing a new strategy for the control of the CFB boiler combustion system. Full article

(This article belongs to the Section L: Energy Sources)

25 pages, 6656 KiB

Open AccessArticle

Energy Efficiency Improvement of Hydraulic Indirect Elevator

by Łukasz Stawiński, Andrzej Kosucki, Justyna Skowrońska and Piotr Malenta

Energies 2025, 18(9), 2163; https://doi.org/10.3390/en18092163 - 23 Apr 2025

Abstract

This article addresses the current issue of energy consumption in the hydraulic drive systems of working machines, with particular emphasis on elevators. This paper describes the results of experimental comparative research and estimation of energy and time consumption for two drive systems of [...] Read more.

This article addresses the current issue of energy consumption in the hydraulic drive systems of working machines, with particular emphasis on elevators. This paper describes the results of experimental comparative research and estimation of energy and time consumption for two drive systems of a hydraulic indirect elevator. The purpose of this article is to compare the energy consumption of a typical multi-valve system (MV) system with that of an innovative new electro-hydraulic drive (EHD) system with a variable speed pump. The EHD system uses a frequency converter with an energy recovery module to control the speed of the car in both directions and the return of potential energy during the lowering cycle. The comparison of these drive systems was performed under the same conditions, realizing the same elevator work cycles. This paper proposes methods for estimating the energy consumption of an MV system based on measurement data collected during an experiment. The results indicate that the EHD system was less energy-intensive, even at below 60%. The smaller the load mass, the shorter the operating time of the EHD system compared to the MV system. The introduced coefficients defining the energy consumption per unit of mass and payload displacement showed more than twice the decrease in energy demand during lifting and energy recovery possibility during lowering. The EHD system provides the same coefficient values regardless of the distance traveled, which makes it a predictable system, in contrast to the MV system, especially during lowering cycles. The benefits of the EHD also include a less complex hydraulic system (elimination of most valves). Full article

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

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13 pages, 3476 KiB

Open AccessArticle

Preparation of Highly Efficient and Stable All-Inorganic Perovskite Solar Cells in Atmosphere Environment

by Yufan Jiang, Dongdong Deng and Jingjing Dong

Energies 2025, 18(9), 2162; https://doi.org/10.3390/en18092162 - 23 Apr 2025

Abstract

All-inorganic CsPbX₃ perovskites have significant potential for applications in the photovoltaic field. However, during their preparation, the slow evaporation rate of the precursor solution limits the extent of solution supersaturation, leading to porous perovskite films that substantially impair device performance. Anti-solvent engineering, [...] Read more.

All-inorganic CsPbX₃ perovskites have significant potential for applications in the photovoltaic field. However, during their preparation, the slow evaporation rate of the precursor solution limits the extent of solution supersaturation, leading to porous perovskite films that substantially impair device performance. Anti-solvent engineering, which introduces a secondary solvent to modulate the crystallization process, is a well established technique in perovskite photovoltaic research. This study systematically examines the effects of four different anti-solvents on perovskite films and corresponding devices. It also investigates the optimal dipping-time of (trifluoromethyl)benzene as an anti-solvent, as well as the impact of varying amounts of anti-solvent additive perfluorinated acid. The optimized devices achieved a maximum power conversion efficiency of 12.68%. Full article

(This article belongs to the Special Issue Advanced Developments of Photovoltaic Devices and Perovskite Solar Cells: 2nd Edition)

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15 pages, 3223 KiB

Open AccessArticle

Efficiency Performance of 7-Level Multiplexed and 3-Level Neutral Point Clamped (NPC) Converters

by Shafquat Hussain, Simone Cosso, Massimiliano Passalacqua, Luis Ramon Vaccaro, Andrea Formentini and Mario Marchesoni

Energies 2025, 18(9), 2161; https://doi.org/10.3390/en18092161 - 23 Apr 2025

Abstract

In medium-voltage AC applications, multilevel converters are essential due to their ability to achieve high efficiency and significantly reduce total harmonic distortion (THD), ensuring improved performance and power quality. This paper presents a detailed analysis of the efficiency, power loss, and THD characteristics [...] Read more.

In medium-voltage AC applications, multilevel converters are essential due to their ability to achieve high efficiency and significantly reduce total harmonic distortion (THD), ensuring improved performance and power quality. This paper presents a detailed analysis of the efficiency, power loss, and THD characteristics of multiplexed multilevel converters and neutral point clamped converters. Using MATLAB^®Simulink 2024b, the switching and conduction losses of both multiplexed multilevel converters and NPC converters are calculated. The three-level NPC converter offers advantages of a simpler design, reduced component count, and cost effectiveness with the drawback of low voltage quality. Simulation results validate the THD, power losses, and efficiency for the conventional three-phase three-level NPC converter and the three-phase multiplexed multilevel converter, and a detailed comparison is performed. Full article

(This article belongs to the Collection Editorial Board Members’ Collection Series: Advances in Power Converters)

23 pages, 1783 KiB

Open AccessArticle

Day-Ahead Scheduling of IES Containing Solar Thermal Power Generation Based on CNN-MI-BILSTM Considering Source-Load Uncertainty

by Kun Ding, Yalu Sun, Boyang Chen, Jing Chen, Lixia Sun, Yingjun Wu and Yusheng Xia

Energies 2025, 18(9), 2160; https://doi.org/10.3390/en18092160 - 23 Apr 2025

Abstract

The fluctuating uncertainty of load demand as an influencing factor for day-ahead scheduling of an integrated energy system with photovoltaic (PV) power generation may cause an imbalance between supply and demand, and to solve this problem, this paper proposes a day-ahead optimal scheduling [...] Read more.

The fluctuating uncertainty of load demand as an influencing factor for day-ahead scheduling of an integrated energy system with photovoltaic (PV) power generation may cause an imbalance between supply and demand, and to solve this problem, this paper proposes a day-ahead optimal scheduling model considering uncertain loads and electric heating appliance (EH)–PV energy storage. The model fuses the multi-interval uncertainty set with the CNN-MI-BILSTM neural network prediction technique, which significantly improves the accuracy and reliability of load prediction and overcomes the limitations of traditional methods in dealing with load volatility. By integrating the EH–photothermal storage module, the model achieves efficient coupled power generation and thermal storage operation, aiming to optimize economic targets while enhancing the grid’s peak-shaving and valley-filling capabilities and utilization of renewable energy. The validity of the proposed model is verified by algorithm prediction simulation and day-ahead scheduling experiments under different configurations. Full article

(This article belongs to the Special Issue Renewable Energy Power Generation and Power Demand Side Management)

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20 pages, 920 KiB

Open AccessArticle

Comprehensive Benefit Evaluation Analysis of Multi-Energy Complementary Off-Grid System Operation

by Yu Lei, Xiaobin Yan, Shenhao Yang, Yu Fan, Chao Ma, Qingsong Li, Yuanfeng Huang and Wei Yang

Energies 2025, 18(9), 2159; https://doi.org/10.3390/en18092159 - 23 Apr 2025

Abstract

In the future, China’s demand for centralized industrial development in remote areas will gradually increase, but the operation evaluation analysis of off-grid systems applicable to the development of such areas has not yet matured, and it is an urgent challenge to improve the [...] Read more.

In the future, China’s demand for centralized industrial development in remote areas will gradually increase, but the operation evaluation analysis of off-grid systems applicable to the development of such areas has not yet matured, and it is an urgent challenge to improve the operation mechanism of off-grid systems and then conduct a comprehensive benefit evaluation of off-grid systems. First of all, this paper focuses on the problem that the existing dimensions of the benefit evaluation of multi-energy complementary off-grid systems are not refined and comprehensive enough, and takes into account their high safety and reliability requirements, as well as the potential impacts on local industries and people’s lives after their completion, and then constructs a more complete comprehensive benefit evaluation indicator system for multi-energy complementary off-grid systems. Secondly, the subjective and objective weighting method based on the combination of the AHP (analytic hierarchy process) and AEM (anti-entropy method) is used to assign weights to the evaluation indicators. Finally, based on the TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) comprehensive evaluation method, a comprehensive benefit evaluation of a multi-energy complementary off-grid system under different operation schemes is conducted, and the example results show that the size of the relative closeness under different operation schemes has a maximum difference of 0.5592, which verifies that the proposed evaluation indicator system and the multilevel evaluation method can comprehensively evaluate and analyze the strengths and weaknesses of multi-energy complementary off-grid systems under different operation schemes, and provide theoretical guidance and decision-making support for the further promotion and construction of multi-energy complementary off-grid systems. Full article

(This article belongs to the Special Issue Leveraging Flexibility Resources to Enhance Renewable Energy Integration and Grid Stability)

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25 pages, 8244 KiB

Open AccessArticle

Sustainable Energy Storage Systems: Polypyrrole-Filled Polyimide-Modified Carbon Nanotube Sheets with Remarkable Energy Density

by Andekuba Andezai and Jude O. Iroh

Energies 2025, 18(9), 2158; https://doi.org/10.3390/en18092158 - 23 Apr 2025

Abstract

Organic hybrid materials are gaining traction as electrode candidates for energy storage due to their structural tunability and environmental compatibility. This study investigates polyimide/carbon nanotube/polypyrrole (PI/CNTs/PPy) hybrid nanocomposites, focusing on the correlation between thermal imidization temperature, polypyrrole deposition time, and the resulting electrochemical [...] Read more.

Organic hybrid materials are gaining traction as electrode candidates for energy storage due to their structural tunability and environmental compatibility. This study investigates polyimide/carbon nanotube/polypyrrole (PI/CNTs/PPy) hybrid nanocomposites, focusing on the correlation between thermal imidization temperature, polypyrrole deposition time, and the resulting electrochemical properties. By modulating PI processing temperatures (90 °C, 180 °C, 250 °C) and PPy deposition durations (60–700 s), this research uncovers critical structure–function relationships governing charge storage behavior. Scanning electron microscopy and electrochemical impedance spectroscopy reveal that low-temperature imidization preserves porosity and enables ion-accessible pathways, while moderate PPy deposition enhances electrical conductivity without blocking pore networks. The optimized composite, processed at 90 °C with 60 s PPy deposition, demonstrates superior specific capacitance (850 F/g), high redox contribution (~70% of total charge), low charge transfer resistance, and enhanced energy/power density. In contrast, high-temperature processing and prolonged PPy deposition result in structural densification, increased resistance, and diminished performance. These findings highlight a synergistic design approach that leverages partial imidization and controlled doping to balance ionic diffusion, electron transport, and redox activity. The results provide a framework for developing scalable, high-performance, and sustainable electrode materials for next-generation lithium-ion batteries and supercapacitors. Full article

(This article belongs to the Topic Advanced Polymeric Composites: Processing, Characterization and Mechanical Behavior)

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13 pages, 1759 KiB

Open AccessReview

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

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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18 pages, 4292 KiB

Open AccessArticle

The Purge Characteristics and Strategy in a Proton Exchange Membrane Fuel Cell with a Linear Segmentation-Based Anode Recirculation System

by Weihao Guo, Xiaoxuan Mu, Weida Shen, Chaoqi Ma, Jie Yu, Fu Wang and Jinliang Yuan

Energies 2025, 18(9), 2156; https://doi.org/10.3390/en18092156 - 23 Apr 2025

Abstract

This study introduces a novel linear segmentation method to optimize the nitrogen purge strategy for proton exchange membrane fuel cells (PEMFCs) operating in an anode recirculation mode. The method simplifies the design of purge cycles by eliminating the need for complex mathematical modeling [...] Read more.

This study introduces a novel linear segmentation method to optimize the nitrogen purge strategy for proton exchange membrane fuel cells (PEMFCs) operating in an anode recirculation mode. The method simplifies the design of purge cycles by eliminating the need for complex mathematical modeling and multivariable optimization, making it more suitable for industrial applications while avoiding the need for lengthy orthogonal experiments. By experimentally determining the maximum tolerable nitrogen accumulation time and leveraging the linear relationship between nitrogen accumulation and purge duration, the traditional long-cycle purge process is divided into multiple short cycles, establishing an optimal nitrogen discharge strategy. Experimental results demonstrate that the segmented purge cycles significantly reduce voltage fluctuations and improve voltage uniformity across cells. Notably, using a purge threshold with a 30 s closing time and a 2 s opening time resulted in a 19.8% improvement in voltage uniformity. In addition, a detailed analysis of the hydrogen consumption during the purge cycle reveals that an excessive purge frequency leads to significant hydrogen losses, whereas prolonged purge cycles may allow nitrogen accumulation to adversely affect voltage stability. By balancing these effects, the proposed strategy maintains the operational efficiency within the ideal range of 50–60%. Full article

(This article belongs to the Section A5: Hydrogen Energy)

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17 pages, 1151 KiB

Open AccessArticle

Comparative Analysis of the Oxy-Fuel Kinetic Mechanisms by the Ignition Delay Time of Methane

by Sergey Osipov, Vladimir Sokolov, Vadim Yakovlev, Muhammad Maaz Shaikh and Nikolay Rogalev

Energies 2025, 18(9), 2155; https://doi.org/10.3390/en18092155 - 23 Apr 2025

Abstract

Supercritical oxy-fuel combustion, which allows for the high efficiency of power generation with near-zero CO₂ emissions, is considered a promising method to reduce the carbon footprint in the power energy sector. One of the problems in the widespread use of oxy-fuel combustion [...] Read more.

Supercritical oxy-fuel combustion, which allows for the high efficiency of power generation with near-zero CO₂ emissions, is considered a promising method to reduce the carbon footprint in the power energy sector. One of the problems in the widespread use of oxy-fuel combustion is a lack of comparative studies on the existing oxy-fuel combustion kinetic mechanisms depending on mixture composition, which complicates the choice of a kinetic mechanism for modeling oxy-fuel combustion. In this paper, a comparative verification of the kinetic mechanisms of GRI-Mech 3.0, UoS sCO₂ 2.0, OXY-NG, and Skeletal was performed using published experimental data on the ignition delay time of methane under conditions of oxy-fuel combustion. A comparative numerical study of the kinetic mechanisms in the wide range of pressures, CO₂ mass fractions in oxidizer (γ), and excess oxidizer ratios (α) by the ignition delay time is also carried out. It was found that the limits of applicability of all of the mechanisms studied are absent when modeling the ignition delay time, the most accurate mechanism to model the IDT of methane in oxy-fuel conditions being UoS sCO₂ 2.0, while the other three mechanisms are overall much inferior to it in terms of accuracy. However, Skeletal and GRI-Mech 3.0 mechanisms can be used to model the IDT during the oxy-fuel combustion of methane under both atmospheric and supercritical conditions, although only in a narrow range of γ. Full article

(This article belongs to the Section I2: Energy and Combustion Science)

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11 pages, 1518 KiB

Open AccessPerspective

Challenges and Opportunities of the Dynamic Operation of PEM Water Electrolyzers

by Balázs Endrődi, Cintia Alexandra Trapp, István Szén, Imre Bakos, Miklós Lukovics and Csaba Janáky

Energies 2025, 18(9), 2154; https://doi.org/10.3390/en18092154 - 23 Apr 2025

Abstract

Hydrogen is expected to play an important role in decarbonizing different heavy industries and the transportation sector. Water electrolysis is, therefore, one of the most rapidly spreading energy technologies, with PEM electrolyzers taking a continuously increasing share in the technology mix. Most often, [...] Read more.

Hydrogen is expected to play an important role in decarbonizing different heavy industries and the transportation sector. Water electrolysis is, therefore, one of the most rapidly spreading energy technologies, with PEM electrolyzers taking a continuously increasing share in the technology mix. Most often, the aim is to form green hydrogen, utilizing electricity exclusively of renewable origin. The intermittency of such sources, however, poses several technological challenges and financial questions. Focusing on PEM electrolyzers, we discuss the effect of pressure, temperature, and reaction rate changes, induced by the intermittent operation, and general thoughts regarding system component erosion caused by the regular start–stop cycles are also considered. As a case study, we present a high-level techno-economic analysis of data from a pilot 1 MW PEM electrolysis system, coupled to a 20 MW PV farm, deployed in Hungary. We underscore the importance of the often overlooked local regulations and financial incentives, which strongly influence the most beneficial operation scenario. Full article

(This article belongs to the Section A5: Hydrogen Energy)

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21 pages, 1080 KiB

Open AccessArticle

Hardware-Centric Exploration of the Discrete Design Space in Transformer–LSTM Models for Wind Speed Prediction on Memory-Constrained Devices

by Laeeq Aslam, Runmin Zou, Ebrahim Shahzad Awan, Sayyed Shahid Hussain, Kashish Ara Shakil, Mudasir Ahmad Wani and Muhammad Asim

Energies 2025, 18(9), 2153; https://doi.org/10.3390/en18092153 - 23 Apr 2025

Abstract

Wind is one of the most important resources in the renewable energy basket. However, there are questions regarding wind as a sustainable solution, especially concerning its upfront costs, visual impact, noise pollution, and bird collisions. These challenges arise in commercial windmills, whereas for [...] Read more.

Wind is one of the most important resources in the renewable energy basket. However, there are questions regarding wind as a sustainable solution, especially concerning its upfront costs, visual impact, noise pollution, and bird collisions. These challenges arise in commercial windmills, whereas for domestic small-scale windmills, these challenges are limited. On the other hand, accurate wind speed prediction (WSP) is crucial for optimizing power management in renewable energy systems. Existing research focuses on proposing model architectures and optimizing hyperparameters to improve model performance. This approach often results in larger models, which are hosted on cloud servers. Such models face challenges, including bandwidth utilization leading to data delays, increased costs, security risks, concerns about data privacy, and the necessity of continuous internet connectivity. Such resources are not available for domestic windmills. To overcome these obstacles, this work proposes a transformer model integrated with Long Short-Term Memory (LSTM) units, optimized for memory-constrained devices (MCDs). A contribution of this research is the development of a novel cost function that balances the reduction of mean squared error with the constraints of model size. This approach enables model deployment on low-power devices, avoiding the challenges of cloud-based deployment. The model, with its tuned hyperparameters, outperforms recent methodologies in terms of mean squared error, mean absolute error, model size, and R-squared scores across three different datasets. This advancement paves the way for more dynamic and secure on-device wind speed prediction (WSP) applications, representing a step forward in renewable energy management. Full article

(This article belongs to the Special Issue Recent Developments of Wind Energy)

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24 pages, 6072 KiB

Open AccessArticle

The Impact of Environmental Policies on Renewable Energy Storage Decisions in the Power Supply Chain

by Chunyi Ji, Xinyue Wang, Wei Zhao, Xuan Wang and Wuyong Qian

Energies 2025, 18(9), 2152; https://doi.org/10.3390/en18092152 - 22 Apr 2025

Abstract

Energy storage is a proficient means of enhancing power supply reliability and facilitating the use of renewable energy. To study the impact of policies on energy storage decisions in the power supply chain, this paper constructs an electricity supply chain and compares the [...] Read more.

Energy storage is a proficient means of enhancing power supply reliability and facilitating the use of renewable energy. To study the impact of policies on energy storage decisions in the power supply chain, this paper constructs an electricity supply chain and compares the equilibrium results under four scenarios based on the Stackelberg game theory. The research reveals that both discharge subsidy and investment subsidy play a beneficial role in improving the level of energy storage technology, regardless of whether power producers choose to invest in or lease energy storage equipment. Furthermore, when combined with the implementation of a renewable portfolio standard, these subsidies can have beneficial outcomes. During the early stages of development in the energy storage industry, investment subsidy proves more advantageous for enhancing both technology levels and electricity demand. Conversely, at later stages of industry development, discharge subsidies become increasingly advantageous for enhancing technological advancements and fulfilling electricity demand. Furthermore, implementing a strategy in which power generators invest in energy storage can enhance their profitability while concurrently advancing technological standards and satisfying electricity demand. Full article

(This article belongs to the Special Issue Economic Analysis and Policies in the Energy Sector)

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26 pages, 4161 KiB

Open AccessArticle

Exergy Analysis of an On-Vehicle Floating Piston Hydrogen Compression System for Direct-Injection Engines

by Mehdi Nikkhah Koojehri, Ashish Singh, Sandeep Munshi and Gordon McTaggart-Cowan

Energies 2025, 18(9), 2151; https://doi.org/10.3390/en18092151 - 22 Apr 2025

Abstract

Direct injection of hydrogen at high pressures into an otherwise unmodified heavy-duty diesel engine offers a near-term pathway to near-zero greenhouse gas emissions for commercial vehicles. Hydrogen direct-injection engines maintain diesel-like performance with equal or better thermal efficiency. Supplying the hydrogen for injection [...] Read more.

Direct injection of hydrogen at high pressures into an otherwise unmodified heavy-duty diesel engine offers a near-term pathway to near-zero greenhouse gas emissions for commercial vehicles. Hydrogen direct-injection engines maintain diesel-like performance with equal or better thermal efficiency. Supplying the hydrogen for injection pressures of ~30 MPa requires a high-pressure supply. Onboard hydrogen compression enables more complete utilization of the stored compressed hydrogen; however, it introduces a significant parasitic load on the engine. The magnitude of this load depends on factors such as the compressor’s configuration, capacity, pressure ratio, efficiency, and the engine’s operating conditions. This paper presents an exergy analysis of an onboard hydrogen compression system that uses hydraulically driven free-floating pistons, sized for heavy-duty commercial vehicles. Minimizing the parasitic loads from the compressor is essential to retain vehicle performance and maximize system-wide efficiency. The exergy analysis approach provides a comprehensive understanding of the whole compression system by comparably quantifying the losses across all components. A one-dimensional model of the compression system, developed in GT-SUITE^TM and validated with experimental data, is used to quantify the main exergy loss components. Exergy efficiency ranges from 12% to 45% under varying pressure ratios and cycle frequencies, with a pronounced increase in efficiency observed at higher cycle frequencies. Major exergy losses occur in the hydraulic driving system up to 79%, especially during retracting and idle phases for lower pressure ratios and cycle frequencies. Within the compression cylinder, exergy destructions account for less than 10% of the total work input, wherein heat transfer and piston friction are identified as the dominant contributors to exergy destruction, with their effects intensifying at higher pressure ratios. This work highlights the challenges of onboard gas compression and develops a systematic framework that can compare compressor design alternatives for different driving cycles. Full article

(This article belongs to the Special Issue New Fuels and Advanced Combustion Modes for Innovative Internal Combustion Engines: 2nd Edition)

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14 pages, 1622 KiB

Open AccessArticle

Study on Hydrogen Combustion Flame Acceleration Mechanism and Prediction Method During Severe Accidents in Nuclear Power Plants

by Ran Liu, Jingyi Yu, Xiaoming Yang, Yong Liu, Rubing Ma and Yidan Yuan

Energies 2025, 18(9), 2150; https://doi.org/10.3390/en18092150 - 22 Apr 2025

Abstract

Combustion caused by hydrogen-dominated combustible gas mixtures presents critical threats to nuclear safety during severe accidents in nuclear power plants, primarily due to their propensity for flame acceleration, deflagration, and subsequent detonation. Although the direct initiation of detonation from localized hydrogen accumulation at [...] Read more.

Combustion caused by hydrogen-dominated combustible gas mixtures presents critical threats to nuclear safety during severe accidents in nuclear power plants, primarily due to their propensity for flame acceleration, deflagration, and subsequent detonation. Although the direct initiation of detonation from localized hydrogen accumulation at critical concentrations remains challenging, flame acceleration can induce rapid pressure escalation and lead to deflagration-to-detonation transition under suitable conditions. The ultra-high-pressure loads generated almost instantaneously will pose serious risks to containment integrity and equipment or instrument functionality within nuclear facilities. This paper investigates the flame acceleration mechanism and criterion, which is crucial for precise hydrogen risk assessment. A hydrogen combustion flame acceleration model is developed, integrating both laminar and turbulent flame propagation across multiple control volumes. Validated against the RUT test, the model demonstrates high fidelity with a maximum 3.17% deviation in flame propagation velocity and successfully captures the pressure discontinuity. The developed model enables comprehensive simulation with improved predictive accuracy of the flame acceleration process, making it an essential tool for advancing fundamental understanding of hydrogen behavior and severe accident analysis. This model’s development marks a paradigm in nuclear safety research by providing an analytical instrument for integrated severe accident programs in nuclear power plants, contributing to improving the potential hydrogen risks assessment and management in next-generation reactor safety. Full article

(This article belongs to the Special Issue Thermal Hydraulics and Safety Research for Nuclear Reactors)

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