Energies

19 pages, 817 KB

Open AccessArticle

Low-Energy Pretreatment of Organic Waste Using a Vortex Layer Reactor: Effects on Biogas Production, Carbon Conversion, and Process Optimization

by Marcin Niemiec, Marcin Suder, Małgorzata Okręglicka, Monika Komorowska, Yurii Syromiatnykov, Jakub Sikora and Karolina Jakóbik

Energies 2026, 19(11), 2732; https://doi.org/10.3390/en19112732 (registering DOI) - 5 Jun 2026

Abstract

The sustainable management of agri-food waste is a key challenge in the context of the circular economy and energy transition. Anaerobic digestion is an effective method for converting organic waste into renewable energy; however, its efficiency is often limited by substrate properties, such [...] Read more.

The sustainable management of agri-food waste is a key challenge in the context of the circular economy and energy transition. Anaerobic digestion is an effective method for converting organic waste into renewable energy; however, its efficiency is often limited by substrate properties, such as high lignin content, low biodegradability, and unfavorable C: N ratios. This study evaluates a low-energy pretreatment method based on a Vortex Layer Reactor (VLR, equivalent to the AVS-100 system) applied to slaughterhouse waste, swine manure, and spent mushroom substrate. The analysis included biogas yield, methane production, carbon conversion, process kinetics, and net energy efficiency. The results showed that pretreatment effectiveness depends on substrate type. No improvement was observed in slaughterhouse waste, with net energy efficiency decreasing by approximately 9%. In contrast, biogas yield increased by 14% for swine manure and 18% for spent mushroom substrate, with a maximum net energy gain of 17.6%. The process required only 2.16–3.6 kWh·Mg⁻¹ (about 9 kWh·Mg⁻¹ TS), significantly less than conventional methods. The findings indicate that pretreatment should be applied selectively, depending on substrate characteristics. This study supports decision-making in biogas plant management by integrating technological efficiency with energy and operational criteria. Full article

(This article belongs to the Special Issue New Challenges of Anaerobic Digestion for Bioproducts and Bioenergy Production)

23 pages, 11828 KB

Open AccessArticle

Predicted Thermoacoustic Flame Response at Megawatt Scale in a Near-Stoichiometric Atmospheric Industrial Furnace

by Jesse Hofsteenge and Jim Kok

Energies 2026, 19(11), 2731; https://doi.org/10.3390/en19112731 (registering DOI) - 5 Jun 2026

Abstract

While gas-turbine combustors have received much research attention, the forced response of large atmospheric industrial flames is much less studied. To improve the understanding of thermoacoustic instabilities in industrial combustion systems, the forced response of a large natural-gas fired test furnace is computed [...] Read more.

While gas-turbine combustors have received much research attention, the forced response of large atmospheric industrial flames is much less studied. To improve the understanding of thermoacoustic instabilities in industrial combustion systems, the forced response of a large natural-gas fired test furnace is computed using Scale-Adaptive Simulations (SASs) with a Flamelet Generated Manifold model. Two test burner configurations are compared. One produces a partially premixed flame (case P) and the other a non-premixed flame. Furthermore, the non-premixed configuration is simulated at both a slightly rich (case N) and a slightly lean set point (case NL). The flame is forced by perturbing the airflow using a superposition of sine waves at four discrete frequencies. That way, the gain and phase of the Flame Transfer Function (FTF) are determined in three simulations for a total of 12 discrete frequencies between 10 and 230 Hz. The results show very different behaviour of the partially premixed and non-premixed configurations. Case P is simulated to be a compact flame, with a maximum FTF gain of one around 70-80 Hz and a quasi-steady limit of 0.7. Case N and NL are characterised by slightly lifted flames acting as low-pass filters that quickly drop off towards higher frequencies. While the phase shift in case P is linearly dependent on frequency and can be related to its flame length, the non-premixed cases have a sharp initial phase shift that levels off with increasing frequency as the gain reduces to zero. Importantly, a non-zero phase shift at 0 Hz is observed for case NL. The nature of the combustion dynamics is further explored by a Proper Orthogonal Decomposition (POD) analysis. The FTFs are applied to predict the thermoacoustic stability using an Acoustic Network Model (ANM). This model is able to reproduce the stability of the cases observed in experiments. The results presented in this study provide insight on the effect of mixing and stoichiometry on the stability of large industrial furnaces. Full article

(This article belongs to the Special Issue Applied Computational Fluid Dynamics in Energy Systems)

37 pages, 2274 KB

Open AccessArticle

Forecast-Driven Virtual Power Plant Dispatch for Hybrid Renewable Energy Systems: Reducing Grid Dependency Using LSTM Models

by Omaira Jajbhay, Mohamed F. Khan and Andrew G. Swanson

Energies 2026, 19(11), 2730; https://doi.org/10.3390/en19112730 (registering DOI) - 5 Jun 2026

Abstract

This study presents a forecast-driven Advanced Forecasting Model (AFM) and Virtual Power Plant (VPP) framework for a hybrid renewable energy system comprising utility-scale solar PV, wind generation, and a Battery Energy Storage System. Long Short-Term Memory neural networks provide real-time short-term forecasts to [...] Read more.

This study presents a forecast-driven Advanced Forecasting Model (AFM) and Virtual Power Plant (VPP) framework for a hybrid renewable energy system comprising utility-scale solar PV, wind generation, and a Battery Energy Storage System. Long Short-Term Memory neural networks provide real-time short-term forecasts to dynamically schedule power flows based on battery state-of-charge, grid import limits, and system constraints. Solar irradiance forecasting achieved MAE = 10.674 W/m², RMSE = 16.348 W/m², and MAPE = 14.18%, while wind speed forecasting achieved MAE = 0.880 m/s, RMSE = 1.115 m/s, and MAPE = 22.01%. Two dispatch scenarios were evaluated over a 72 h window: a reactive baseline and the proposed AFM/VPP strategy. The AFM reduced total grid imports by 57.48% (1466.34 MWh to 623.47 MWh), increased renewable utilization, and minimized curtailment. Financial analysis indicates an accelerated break-even (Year 6 vs. Year 9), a higher net present value, and cumulative 20-year profits exceeding R26.01 billion despite marginally higher capital expenditure. Emissions analysis shows annual CO₂ reductions from 123,680 t to 61,841 t, yielding 1.236 million tons of avoided emissions over 20 years. These results confirm that forecast-driven dispatch enhances operational efficiency, economic performance, and environmental sustainability, establishing a scalable approach for VPP operation in renewable-rich energy systems. Full article

(This article belongs to the Special Issue AI-Driven Sustainable Power Grids: Enhancing Cybersecurity, Operation, and Control of Conventional, Modern, and Renewable-Based Energy Systems—2nd Edition)

19 pages, 2157 KB

Open AccessArticle

FTimeDD: A Time–Frequency Collaborative Model for Multi-Energy Load Forecasting

by Zi Lin, Ziyi Wang, Tengyue Guo and Min Xia

Energies 2026, 19(11), 2729; https://doi.org/10.3390/en19112729 (registering DOI) - 5 Jun 2026

Abstract

With the global energy transition, Integrated Energy Systems (IESs) improve efficiency by coordinating multiple energy sources, including electricity, cooling, and heating. Accurate load forecasting is essential for reliable energy system operation. However, multi-energy loads show complex coupling, non-stationarity, and long-term dependencies. These characteristics [...] Read more.

With the global energy transition, Integrated Energy Systems (IESs) improve efficiency by coordinating multiple energy sources, including electricity, cooling, and heating. Accurate load forecasting is essential for reliable energy system operation. However, multi-energy loads show complex coupling, non-stationarity, and long-term dependencies. These characteristics pose significant challenges to forecasting tasks. Existing methods have improved short-term forecasting accuracy, but still struggle to jointly capture long-term trends and local fluctuations. To address these issues, this paper proposes FTimeDD, a time–frequency collaborative model for multi-energy load forecasting in IESs. It adopts a dual-path decoupling architecture. The time-domain path separates trend and fluctuation components, while the frequency-domain path extracts dominant periodic features. The two paths are then fused to predict electricity, cooling, and heating loads. Experiments on the ASU Integrated Energy System dataset show that FTimeDD performs well across different forecasting horizons. Compared with the strongest baseline for each metric and horizon, FTimeDD reduces MAE, RMSE, and MAPE by 3.85%, 2.48%, and 1.91% on average, respectively. The method improves forecasting accuracy under the adopted experimental setting while maintaining a compact model scale and low computational cost. Full article

(This article belongs to the Special Issue Artificial Intelligence for Energy Forecasting)

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16 pages, 7107 KB

Open AccessArticle

Influence of Ionomer Overcoating on the Interfacial Properties and Performance of Gas Diffusion Electrode-Based Proton Exchange Membrane Fuel Cells

by Ayon Karmakar, Mrittunjoy Sarker, Zabihollah Najafianashrafi, Joy Marie Mora, Nitul Kakati and Po-Ya Abel Chuang

Energies 2026, 19(11), 2728; https://doi.org/10.3390/en19112728 (registering DOI) - 5 Jun 2026

Abstract

Membrane electrode assemblies (MEA) based on gas diffusion electrodes (GDEs) usually suffer from greater ohmic losses and proton transport resistances owing to poor contact at the membrane–catalyst layer (CL) interface. This affects the overall performance of the proton-exchange-membrane fuel cells (PEMFCs). To address [...] Read more.

Membrane electrode assemblies (MEA) based on gas diffusion electrodes (GDEs) usually suffer from greater ohmic losses and proton transport resistances owing to poor contact at the membrane–catalyst layer (CL) interface. This affects the overall performance of the proton-exchange-membrane fuel cells (PEMFCs). To address this, it is essential to strengthen the interface between the membrane and CL, especially at the cathode side. In this context, the present work is focused on engineering the membrane–CL interface by applying an optimized Nafion ionomer overcoat on top of a Mayer-rod-coated cathode-GDE, within an asymmetric MEA architecture. The role of the Nafion overcoat in improving the membrane–CL interface is inferred from morphological observations and in situ electrochemical characterizations. The electrochemical evaluation indicates the critical role of the ionomer overcoat on GDE, followed by the hot pressing during MEA fabrication, in improving the PEMFC performance. Furthermore, the surface characteristics of the overcoated GDEs have been characterized by profilometry and scanning electron microscopy. The findings suggest progressive smoothening of the CL surface with increasing ionomer overcoat concentration till 10 wt.% and further increase leads to crack generation. The polarization behavior of the overcoated (0–20 wt.%) GDE-MEAs identifies 10 wt.% as the best-performing sample among the discrete cases examined, corresponding to an ~4.8 μm ionomer overlayer (0.86 mg cm⁻²). This configuration exhibits the lowest ohmic resistance and improved proton and mass transport behavior, suggesting enhanced interfacial interaction based on HFR/EIS trends. In addition, the study of relative humidity (RH) transitions (100% RH → 40% RH) and polarization curves indicate superior performance of the 10 wt.%-overcoated GDE-MEA compared to the catalyst-coated membrane (CCM) type MEA under fully humidified conditions. This study manifests that interfacial engineering is highly effective in fabricating a high-performance GDE-based MEA for PEMFCs. Full article

(This article belongs to the Special Issue Research and Development of Key Materials and Devices for Fuel Cells)

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25 pages, 307 KB

Open AccessArticle

Industrial Structure, Green Finance, and Energy Resilience Enhancement in China

by Qiuyao Fu

Energies 2026, 19(11), 2727; https://doi.org/10.3390/en19112727 (registering DOI) - 5 Jun 2026

Abstract

Against the backdrop of global energy transition and multiple uncertainties, enhancing energy resilience has become a core priority for China’s pursuit of secure and sustainable development. Using Chinese provincial panel data from 2011 to 2019, this study applies a two-way fixed effects model, [...] Read more.

Against the backdrop of global energy transition and multiple uncertainties, enhancing energy resilience has become a core priority for China’s pursuit of secure and sustainable development. Using Chinese provincial panel data from 2011 to 2019, this study applies a two-way fixed effects model, mediation effect tests, and interaction term analysis to empirically investigate the relationship between industrial structure, green finance, and energy resilience. The main findings are as follows. First, the increases in gross regional product (GRP) and the added value of the secondary and tertiary sectors significantly enhance energy resilience. Second, heterogeneity analysis indicates that in regions with a high level of green finance, both GRP and the secondary sector’s added value exhibit stronger positive effects on energy resilience, whereas in regions with lower levels of green finance, the tertiary sector’s added value contributes more significantly to energy resilience improvement. In areas with high coal dependency, the secondary sector’s added value shows a significantly positive effect on energy resilience. Increases in industrial and construction industry added value significantly enhance energy resilience, suggesting that the expansion of the secondary industry contributes positively to the stability and resilience of the energy system. Third, the mechanism analysis shows that green finance contributes to energy resilience partly through the optimization of the energy consumption structure. Specifically, by effectively curbing coal consumption and, to a lesser extent, fuel oil production, green finance reduces the structural dependence of the economy on high-carbon energy. By contrast, channels such as electricity generation yield weaker and less robust evidence. These findings suggest that energy resilience is fundamentally shaped by the interplay of industrial structure, financial intermediation, and energy structure adjustment. Therefore, policy should shift from single instruments to integrated governance, synergizing industrial policy, green finance, and energy optimization to bolster energy resilience. Full article

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

21 pages, 2198 KB

Open AccessArticle

Potential Use of Methane Gas from Municipal Waste Storage Facilities: A Case Study of the Karaganda Region

by Ravil Mussin, Denis Akhmatnurov, Nail Zamaliyev, Yelena Tseshkovskaya, Natalya Tsoy, Alexandr Zakharov, Vadim Tseshkovskiy, Nikita Ganyukov, Krzysztof Skrzypkowski, Krzysztof Zagórski and Anna Zagórska

Energies 2026, 19(11), 2726; https://doi.org/10.3390/en19112726 (registering DOI) - 5 Jun 2026

Abstract

This article presents an environmental assessment of emissions from a solid waste landfill in the Karaganda Region of the Republic of Kazakhstan in order to study the dynamics of methane release and determine its energy potential. The study is based on an analysis [...] Read more.

This article presents an environmental assessment of emissions from a solid waste landfill in the Karaganda Region of the Republic of Kazakhstan in order to study the dynamics of methane release and determine its energy potential. The study is based on an analysis of a 13-hectare facility that has been operating since 2015 in a reclaimed quarry with an average annual accumulation volume of up to 4000 tons. The methodology includes a detailed analysis of the morphological composition of waste (57% of the organic fraction) and consideration of regional climatic parameters for modeling the phase-specific formation of biogas, according to the approved national methodology. It has been established that, by 2030, the volume of methane will be 81.7–92.6 tons/year. Based on the data obtained, a set of environmental protection measures is proposed, including the installation of special pipes for degassing and the introduction of automated monitoring based on stationary sensors. The results confirm the technical feasibility of using landfill gas as an alternative energy resource and can serve as a scientific and methodological basis for designing environmentally safe landfills in a sharply continental climate and intensive industrial infrastructure. Full article

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29 pages, 23367 KB

Open AccessArticle

Numerical Simulation of Heat Transfer in Saline Soil Energy Pile Groups

by Weidong Lyu, Zirui Wang, Xudong Zhao and Jinwei Qiu

Energies 2026, 19(11), 2725; https://doi.org/10.3390/en19112725 (registering DOI) - 5 Jun 2026

Abstract

To reduce adverse environmental impacts and boost renewable energy utilization, energy pile technology bridges traditional energy systems and building structures, offering an innovative route for urban low-carbonization. Currently, research on energy piles is confined to conventional non-saline soil, with insufficient exploration of their [...] Read more.

To reduce adverse environmental impacts and boost renewable energy utilization, energy pile technology bridges traditional energy systems and building structures, offering an innovative route for urban low-carbonization. Currently, research on energy piles is confined to conventional non-saline soil, with insufficient exploration of their heat transfer performance in saline soil. Thus, this paper studies the latter based on prior non-saline soil research. The heat transfer performance of pile groups is analyzed in COMSOL Multiphysics by varying the pile diameters, spacing, configurations, and numbers. The findings show that the central pile undergoes the most significant thermal interference, with its water temperature on the 30th day being 1.26 °C higher than that of a single pile. A pile spacing equal to four times the diameter greatly reduces thermal interference, and a spacing of six times the diameter renders the accumulated heat effect insignificant. Additionally, a plum-shaped pile arrangement reduces energy pile group interference effectively, with higher heat transfer capacity than the traditional square arrangement. Increasing pile diameter only benefits heat transfer greatly in the first 10 days, as thermal interference offsets the advantage of expanded heat transfer area from larger diameters. Full article

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25 pages, 8884 KB

Open AccessArticle

Integrated Geology–Engineering Evaluation and Strategy Optimization for Tight Oil Development in Complex Fault Blocks: A Case Study of the G5 Block, Nanpu Sag

by Zhongliang Yu, Tongfeng Cao, Yang Sun, Hong Liu, Jian Cui, Rong Fan, Yajuan Ju, Qian Cheng, Hengbao Li and Junyi Xia

Energies 2026, 19(11), 2724; https://doi.org/10.3390/en19112724 (registering DOI) - 5 Jun 2026

Abstract

To address core challenges involving severe reservoir heterogeneity, complex fracture systems, and rapid energy depletion encountered in the development of tight oil reservoirs in the G5 block of the Nanpu Sag, this study performs a systematic analysis of geological characteristics and optimizes an [...] Read more.

To address core challenges involving severe reservoir heterogeneity, complex fracture systems, and rapid energy depletion encountered in the development of tight oil reservoirs in the G5 block of the Nanpu Sag, this study performs a systematic analysis of geological characteristics and optimizes an integrated geology–engineering development strategy. Through the integration of 3D seismic and well-logging data, the “sandwich-style” superposition architecture of sand bodies in the Es₃⁴ sub-member is quantitatively characterized. It reveals that productivity is co-controlled by high-quality main channel sand bodies (permeability: 0.5–1 mD) and high-density fracture zones (linear density: 3.2 fractures·m⁻¹) along structural ridges. Consequently, a comprehensive technical system is established, incorporating trajectory optimization for high-angle wells, differential stimulated reservoir volume (SRV) fracturing based on the Reservoir Quality Index (RQI), and CO₂ huff-n-puff for energy supplementation. Field applications demonstrate that optimized well placement increased the drilling encounter rate of high-quality reservoirs from 42% to 78%, while CO₂ huff-n-puff technology successfully restored the formation pressure coefficient from 0.65 to 0.82. The implementation of this integrated approach extended the stable production period of typical wells to 18 months, significantly mitigating production decline and increasing the ultimate recovery factor of the block to 14.5%, which provides a favorable recovery level for a complex fault-block tight oil reservoir compared with the generally low primary-recovery performance reported for analogous tight oil systems in rift-basin settings. This study confirms that the coupling zone of fracture systems along structural ridges and high-quality sand bodies represents the optimal target for economic development. The proposed geology–engineering synergy model provides a transferable technical paradigm for the efficient development of similar complex fault-block tight oil reservoirs. Full article

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16 pages, 1413 KB

Open AccessArticle

Electric Shock Simulation and Risk Assessment in Low-Voltage Distribution Networks Under Unknown Topology: A Two-Stage Approach Based on Smart Meter Data

by Zhe Li, Shoukang Luo, Xiaojia Sun, Yang Li, Yubo Zhang, Chakhung Yeung and Yuxuan Ding

Energies 2026, 19(11), 2723; https://doi.org/10.3390/en19112723 (registering DOI) - 5 Jun 2026

Abstract

Low-voltage distribution networks are critical for supplying power to end-users, and electric shock safety is a key concern; however, the frequent incompleteness of topology information in practical operations makes it challenging to accurately assess electric shock risks. This paper proposes a two-stage approach [...] Read more.

Low-voltage distribution networks are critical for supplying power to end-users, and electric shock safety is a key concern; however, the frequent incompleteness of topology information in practical operations makes it challenging to accurately assess electric shock risks. This paper proposes a two-stage approach for electric shock simulation and risk assessment in low-voltage distribution networks with completely unknown topology and absent phase-angle measurements, addressing the critical challenge of unavailable, incomplete, or outdated topology information using only conventional smart meter data. It innovatively investigates shock risks under TT, TN-C, and TN-S grounding systems without prior topology knowledge or synchronized phasors. The proposed methodology combines a phase-angle-agnostic data-driven stage and a model-driven stage: the data-driven stage uses an iterative algorithm for topology label matrix estimation and weighted Laplacian matrix reconstruction with hierarchical clustering to identify network structure and line parameters, requiring only active power, reactive power, voltage magnitude, and current magnitude. The model-driven stage adopts modified nodal analysis with the finite-difference time-domain (MNA-FDTD) method to evaluate transient leakage voltage distribution under single-phase-to-ground faults, thereby assessing electric shock risks in line with international safety standards. Key contributions include a practical phase-free topology identification framework, comparative risk analysis of three grounding systems, and an integrated data-model approach for real-world low-observability networks. Simulation results show accurate topology/parameter identification with a relative Frobenius-norm error of only 1.8% even without phase data. TN-S provides the highest safety complying with IEC standards, followed by TN-C and TT under specific conditions, offering a practical solution for utilities lacking detailed topology records. Full article

(This article belongs to the Section A1: Smart Grids and Microgrids)

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14 pages, 8318 KB

Open AccessArticle

Enhanced Liquid–Solid Triboelectric Nanogenerator with Multi-Tube Nesting Structure for Efficient Wave Energy Harvesting

by Denghui Li, Peng Zhang, Peng Luo, Jiamei Su, Wenhao Li, Shishi Li and Qianxi Zhang

Energies 2026, 19(11), 2722; https://doi.org/10.3390/en19112722 (registering DOI) - 5 Jun 2026

Abstract

Real-time monitoring of marine ecosystems is crucial for global climate change research. In extreme marine environments such as the westerly regions in the Arctic and Antarctic, monitoring buoys and platforms often suffer from severe challenges, including insufficient energy supply, limited battery life, and [...] Read more.

Real-time monitoring of marine ecosystems is crucial for global climate change research. In extreme marine environments such as the westerly regions in the Arctic and Antarctic, monitoring buoys and platforms often suffer from severe challenges, including insufficient energy supply, limited battery life, and difficult maintenance. Triboelectric nanogenerators (TENGs) offer a promising strategy for self-powered marine sensing. However, conventional tubular liquid–solid triboelectric nanogenerators (LS-TENGs) suffer from low efficiency of interfacial charge transfer due to limited contact area and excessive internal resistance, which restricts their output. In this study, a multi-tube nested liquid–solid triboelectric nanogenerator (MLS-TENG) is proposed, and the suitable filling ratio is determined through comparative experiments on structural parameters. This design significantly increases the effective contact area, reduces internal resistance, and improves synergistic charge transfer at multiple interfaces. Experimental results demonstrate that the MLS-TENG exhibits substantially improved electrical output compared with the corresponding single-tube structures. When integrated with a power management module, the capacitor charging efficiency is improved by approximately 120 times. In real sea trials, an array composed of MLS-TENG units successfully drives a self-powered sensing system, achieving stable 4G transmission of environmental parameters. This work provides a scalable structural optimization strategy for constructing high-performance blue energy-harvesting self-powered nodes for the marine Internet of Things. Full article

(This article belongs to the Section D3: Nanoenergy)

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24 pages, 8327 KB

Open AccessReview

Low-Carbon Technologies in Reconstructing Ukraine’s Energy Sector: The Role of Green Hydrogen

by Manuela Tvaronavičienė and Wadim Strielkowski

Energies 2026, 19(11), 2721; https://doi.org/10.3390/en19112721 (registering DOI) - 5 Jun 2026

Abstract

This paper assesses the role of green hydrogen and green ammonia in the low-carbon reconstruction of Ukraine’s energy sector. The country, severely affected by war, has more than 70% of its energy infrastructure damaged or destroyed, which calls for novel solutions for not [...] Read more.

This paper assesses the role of green hydrogen and green ammonia in the low-carbon reconstruction of Ukraine’s energy sector. The country, severely affected by war, has more than 70% of its energy infrastructure damaged or destroyed, which calls for novel solutions for not only reconstructing but also rethinking Ukraine’s energy sector shaped by the Soviet-era planning. In this context, decentralized and renewable energy solutions appear to be one of the best options to achieve this goal. This study combines four novel and mutually reinforcing methods: a Scopus-based literature review of highly cited green hydrogen publications, natural language processing (NLP) and bibliometric network analysis of Ukraine-related hydrogen research, a SWOT assessment, and a geospatial hydrogen production cost model (GEOH2). The novelty of this research lies in this integrated Ukraine-specific framework, which links research trends, wartime reconstruction constraints, hub-level policy choices, and financing risk-sensitive cost modeling. Therefore, the quantitative part of GEOH2 estimates the levelized cost of green hydrogen, while ammonia is treated as a downstream screening-level conversion and export pathway rather than as a full plant-level ammonia model. Our results show that Ukrainian green hydrogen research is concentrated on renewable-energy strategy, wind and solar electrolysis, water and desalination constraints, gas grid blending, underground storage, ammonia derivatives, and decentralized energy systems. The GEOH2 results indicate that southern Ukraine has strong physical potential for competitive green hydrogen production under de-risked financing, while war risk financing can make even resource-rich areas economically unattractive. Odesa and Dnipro emerge as important export-oriented and industrial hubs, whereas Zakarpattia remains strategically relevant as a safer western corridor linked to European markets. Our findings demonstrate that Ukraine’s hydrogen and ammonia development needs to follow a phased pathway: domestic renewable build-out and grid repair, pilot electrolysis projects and screening-level ammonia conversion pathways, targeted de-risking and insurance mechanisms, and only then broader export corridor development. This pathway can support decarbonization, energy security, industrial modernization, and Ukraine’s long-term integration into European clean energy value chains. Full article

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

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19 pages, 1572 KB

Open AccessArticle

Minimal Photovoltaic Solar Cooker for a Catalytic Effect on Energy Poverty

by Antonio Lecuona-Neumann, José-Ignacio Nogueira-Goriba and Jean Boubour

Energies 2026, 19(11), 2720; https://doi.org/10.3390/en19112720 - 4 Jun 2026

Abstract

One to four million annual premature deaths are associated with household air pollution. This indoor pollution is mainly generated by traditional biomass cookstoves. Thus, solar cooking can significantly reduce this toll. Its proliferation would also mitigate deforestation pressures. Additionally, for developing countries, it [...] Read more.

One to four million annual premature deaths are associated with household air pollution. This indoor pollution is mainly generated by traditional biomass cookstoves. Thus, solar cooking can significantly reduce this toll. Its proliferation would also mitigate deforestation pressures. Additionally, for developing countries, it would alleviate the fuel collection workload, mainly borne by women responsible for fuel collection. Electric cooking provides a clean and controllable alternative to thermal cookers for indoor food preparation, sterilization and heating. This study presents a minimal, off-grid photovoltaic solar cooker that operates without batteries and power electronics. Such a cooker constitutes a low-cost and high-reliability solution for electrically decentralized locations. The system encompassing the cooker is conceived as an accessible entry point for household-level photovoltaic (PV) adoption. So, it offers the potential to catalyze the uptake of clean-energy technologies and to support sustainable development. The proposed design dissipates PV power into heat using commercial positive temperature coefficient (PTC) resistors operating near their Curie temperature. A simplified theoretical model is formulated to easily estimate the thermal power and heat-transfer conductances required for achieving cooking temperatures. An instrumented prototype allows for characterizing the transient temperature evolution during controlled heating and cooling experiments in the laboratory, facilitating development in an initial step avoiding the PV panel. The results demonstrate that the minimal PV configuration is technically feasible, robust, and compatible with low-resource settings. This encourages its adoption in communities experiencing energy poverty. Full article

(This article belongs to the Collection Featured Papers in Solar Energy and Photovoltaic Systems Section)

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27 pages, 5655 KB

Open AccessArticle

Energy Supply Resilience and Industrial Continuity Under a Strait of Hormuz Blockade

by Feng An, Shuai Ren, Xuyang Liu and Jingwen Cui

Energies 2026, 19(11), 2719; https://doi.org/10.3390/en19112719 - 4 Jun 2026

Abstract

A blockade or severe disruption in the Strait of Hormuz would test energy supply resilience by reducing crude oil and LNG availability and by raising routing, freight, insurance, port-handling, warehousing, and transport-support costs. This paper develops a short-run multi-regional input–output stress test to [...] Read more.

A blockade or severe disruption in the Strait of Hormuz would test energy supply resilience by reducing crude oil and LNG availability and by raising routing, freight, insurance, port-handling, warehousing, and transport-support costs. This paper develops a short-run multi-regional input–output stress test to assess where such an energy-route shock enters the production system, how reserves and inventories reduce pass-through, which cross-border links carry residual costs, and where final demand absorbs them. Using the OECD ICIO 2025 edition for 2022, we map the shock to oil and gas extraction, refining, utilities, transport, and transport-support sectors, with an additional premium for major Gulf energy exporters. We propagate the shock for seven input–output rounds under inventory damping. First-round exposure and later-round burden do not coincide, as energy-intensive materials, aviation services, chemicals, minerals, metals, electronics, and machinery face higher downstream costs through material and logistics purchases. With 30% inventory absorption, the upstream energy shock needed for downstream manufacturing to reach a 10% added-cost threshold rises from 73.6% to 85.3%. The results support targeted reserve release, coordinated rerouting, port-logistics priority, inventory management around high-value links, and continuity protection for vulnerable sectors. Full article

(This article belongs to the Special Issue Energy Policies and Sustainable Development)

28 pages, 8310 KB

Open AccessArticle

Monitoring and Simulation of Curing-Induced Residual Strain in Epoxy Core of Ultra-High-Voltage Bushing

by Yu Zhang, Rui Liu, Yun Feng, Wenlong Liao, Zhou Mu, Yueping Yang, Zhenyu Wang, Lei Yan and Hongyu Nie

Energies 2026, 19(11), 2718; https://doi.org/10.3390/en19112718 - 4 Jun 2026

Abstract

The UHV dry-type bushing plays a critical role in power transmission by enabling electrical connection, electrical insulation, and mechanical support, making it a core component for ensuring the safe and stable operation of UHV direct current (DC) transmission projects. Epoxy resin, serving as [...] Read more.

The UHV dry-type bushing plays a critical role in power transmission by enabling electrical connection, electrical insulation, and mechanical support, making it a core component for ensuring the safe and stable operation of UHV direct current (DC) transmission projects. Epoxy resin, serving as the fundamental insulating material for the bushing core, undergoes significant residual strain during high-temperature curing due to chemical shrinkage and thermal strain, which directly affects the molding quality and service reliability of the component. This paper investigates the curing process of a large-thickness epoxy material, which is on the same scale as a UHV bushing. An in situ monitoring system combining fiber Bragg grating (FBG) sensors and thermocouples, together with COMSOL Multiphysics simulations, is employed to systematically study the evolution of the temperature field and residual strain throughout the entire curing process, considering the demolding effect. The results show that during the curing stage, the internal temperature distribution is non-uniform, with a maximum temperature difference of 65 °C between the center and the edge. The residual strain is dominated by chemical shrinkage (accounting for 73.25%) and exhibits a pronounced radial gradient. Mold constraint and demolding cause abrupt changes in the strain. The developed thermo-chemo-mechanical coupled model shows good agreement between simulations and experimental measurements. Thermal cycling relaxes the residual stress, achieving a reduction of 3.89–5.77%. This study provides support for process optimization and defect prevention in large-scale epoxy insulation components. Full article

(This article belongs to the Special Issue Simulation and Analysis of Electrical Power Systems—2nd Edition)

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15 pages, 5945 KB

Open AccessPerspective

Toward Energy-Efficient and Circular Wind Power Systems: Closing the Material Loops of Wind Turbine Blades

by Jie Yang, Yiye Lu, Junze Gong, Mingxin Xu, Jiale Wu, Lele Dong, Haocheng Xu, Qing Lu, Wei Li and Qiang Lu

Energies 2026, 19(11), 2717; https://doi.org/10.3390/en19112717 - 4 Jun 2026

Abstract

This perspective focuses on the field of solid waste recovery and resource utilization for end-of-life (EoL) wind turbine blades. Wind energy plays a central role in the global transition toward low-carbon energy systems owing to its technological maturity, scalability, and widespread resource availability. [...] Read more.

This perspective focuses on the field of solid waste recovery and resource utilization for end-of-life (EoL) wind turbine blades. Wind energy plays a central role in the global transition toward low-carbon energy systems owing to its technological maturity, scalability, and widespread resource availability. As global installed wind power capacity exceeded 1000 GW in 2024, improving the life-cycle energy efficiency and resource productivity of wind energy systems has become increasingly important. In this context, wind turbine blades (WTBs), the most material-intensive components with high embodied energy, are approaching large-scale end-of-life replacement, with global EoL blade waste projected to reach 2–4 million tons by 2030. Although blades may reach the end of their structural service life, they contain substantial quantities of reinforcing fibers and polymeric matrices that embody significant material and manufacturing energy. Integrating blade recycling into the wind energy value chain represents a critical opportunity to reduce dependence on energy-intensive virgin materials and lower life-cycle energy consumption and associated carbon emissions. However, the realization of energy-efficient circular utilization remains constrained by several challenges, including inefficient heat and mass transfer during blade depolymerization, limited valorization of resin-derived products, and performance degradation of recovered fibers. This perspective examines the material characteristics of blades from a life-cycle energy utilization standpoint, assesses existing recycling pathways, and identifies key technological and system-level bottlenecks. Emphasis is placed on process intensification, product upgrading, and design-for-circularity strategies to support the long-term sustainability of wind power systems. Full article

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

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21 pages, 1058 KB

Open AccessArticle

Assessment of the Renewable Energy Recovery Potential from Municipal Solid Waste: A Polish Case Study

by Emilia den Boer, Kamil Banaszkiewicz, Iwona Pasiecznik, Jan den Boer, Hongzchi Ma, Elias Hakalehto and Łukasz Kowalczyk

Energies 2026, 19(11), 2716; https://doi.org/10.3390/en19112716 - 4 Jun 2026

Abstract

This study investigates whether the optimal utilization of the biomass potential contained in municipal solid waste (MSW) can support the implementation of circular economy (CE) principles and contribute to climate policy objectives, particularly the reduction in greenhouse gas (GHG) emissions in the waste [...] Read more.

This study investigates whether the optimal utilization of the biomass potential contained in municipal solid waste (MSW) can support the implementation of circular economy (CE) principles and contribute to climate policy objectives, particularly the reduction in greenhouse gas (GHG) emissions in the waste management sector. The analysis evaluates whether waste-to-energy recovery can support the objectives of the European Green Deal, including a 55% reduction in GHG emissions by 2035 and the achievement of climate neutrality by 2050. The assessment was conducted for two MSW streams generated in a Polish municipality: separately collected biowaste and residual MSW remaining after meeting European reuse and recycling targets. The study summarizes the results of detailed experimental investigations of the physicochemical and fuel properties of these waste streams. Proven and commercially available energy recovery technologies, including anaerobic digestion (AD) of biowaste and incineration of residual waste, were analyzed. GHG emissions were assessed using a life cycle assessment (LCA) approach, taking into account both direct emissions and avoided emissions resulting from the substitution of conventional energy and fertilizer production. The experimental results revealed significant variability in the biodegradability and energy potential of individual biowaste fractions, with the highest biogas yields observed for kitchen waste. Residual waste exhibited a considerable calorific value and a significant share of renewable energy due to its biomass content. The results indicate that the share of renewable energy in electricity generated from waste is expected to increase from 46.1% in 2025 to 49.9% in 2040. In relation to the total electricity demand of the analyzed city, energy recovered from waste accounts for 1.8 ± 0.3% in 2025 and 1.3 ± 0.2% in 2040. Scenario-based modeling demonstrated that the target system, maximizing energy recovery from both biowaste and residual waste, achieves a consistently negative GHG emission balance throughout the analyzed period (2025–2040), ranging from −72 ± 15 kg CO₂-eq/ton in 2025, through the most favorable value of −81 ± 17 kg CO₂-eq/ton in 2035, to −57 ± 12 kg CO₂-eq/ton in 2040, expressed per ton of total managed biowaste and residual waste. Full article

37 pages, 2217 KB

Open AccessReview

Optimal Planning of Electric–Hydrogen Coupled Integrated Energy System: A Comprehensive Review

by Hongbo Ren, Lili Miao, Qiong Wu, Xinyu Liu and Weisheng Zhou

Energies 2026, 19(11), 2715; https://doi.org/10.3390/en19112715 - 4 Jun 2026

Abstract

Against the backdrop of climate change, the volatility of energy supply and demand in integrated energy systems (IESs) has intensified, resulting in heightened scheduling challenges. Electric–hydrogen coupling has emerged as a pivotal approach to fostering multi-energy complementarity while enhancing the flexibility and stability [...] Read more.

Against the backdrop of climate change, the volatility of energy supply and demand in integrated energy systems (IESs) has intensified, resulting in heightened scheduling challenges. Electric–hydrogen coupling has emerged as a pivotal approach to fostering multi-energy complementarity while enhancing the flexibility and stability of IES. Rational planning of an electric–hydrogen coupled integrated energy system (EH-IES) can further strengthen energy interconnection and mutual support. First, the architecture and diverse coupling modes of the EH-IES are outlined based on key technologies and coupling mechanisms. Accurate modeling serves as the “cornerstone” of planning, with electric power and hydrogen energy equipment acting as the foundational “carriers” and electric–hydrogen coupling devices as the critical “link.” By examining application scenarios across the transportation, building, and industrial sectors, the study analyzes EH-IES planning scenarios, objectives, and modeling methodologies. Sector-specific planning primarily focuses on equipment configuration and layout, evaluated from economic and/or environmental perspectives. Finally, future research directions for EH-IES planning are proposed, addressing multiple uncertainties, energy demand dynamics, and market mechanisms. These insights aim to provide a reference for subsequent studies. Full article

(This article belongs to the Special Issue Sustainable Energy Systems: Progress, Challenges and Prospects)

22 pages, 11024 KB

Open AccessArticle

Time–Frequency Domain Signal Analysis for Knock Detection in Hydrogen-Fueled Engines

by Brijesh Kinkhabwala, Uwe Wagner and Thomas Koch

Energies 2026, 19(11), 2714; https://doi.org/10.3390/en19112714 - 4 Jun 2026

Abstract

Hydrogen is a promising carbon-neutral fuel for future internal combustion engines due to its wide flammability range, high flame speed, and absence of carbon-based emissions. However, its high reactivity significantly increases susceptibility to abnormal combustion phenomena such as knock and pre-ignition, which can [...] Read more.

Hydrogen is a promising carbon-neutral fuel for future internal combustion engines due to its wide flammability range, high flame speed, and absence of carbon-based emissions. However, its high reactivity significantly increases susceptibility to abnormal combustion phenomena such as knock and pre-ignition, which can compromise engine efficiency, durability, and operational stability. Accurate detection and characterization of knock in hydrogen-fueled spark-ignition engines remain challenging due to the highly transient, broadband, and cycle-dependent nature of abnormal combustion-induced pressure oscillations. Conventional knock indicators based solely on time-domain pressure oscillations or fixed-band frequency analysis are limited in their ability to capture transient resonance behavior and cyclic variability. This study presents an integrated frequency- and time–frequency-domain methodology for knock detection using high-resolution in-cylinder pressure data acquired from a single-cylinder research engine operating under hydrogen port fuel injection (PFI). A discrete Fast Fourier Transform (DFFT) approach applied at stationary points of dynamically windowed pressure signals enables accurate identification of dominant resonance modes while minimizing spectral leakage. A Gaussian-based adaptive windowing strategy is introduced to capture combustion-driven cyclic variations more effectively. Short-Time Fourier Transform (STFT) and sum-based spectral analysis further provide detailed time–frequency localization of transient knock events. The proposed methodology demonstrates a clear separation between normal combustion and knock conditions, enabling reliable cycle-by-cycle identification of abnormal combustion events under varying operating conditions. The experimentally observed resonance frequencies are validated against theoretical predictions using Draper’s acoustic resonance equation, supporting the physical interpretation of knock-induced pressure oscillations. The results demonstrate that the proposed adaptive spectral methodology significantly improves knock detection accuracy compared to conventional indicators and provides a robust framework for advanced knock diagnostics, engine calibration, and combustion control in hydrogen-fueled engines. Full article

(This article belongs to the Special Issue Advanced Combustion Technologies: Challenges and Solutions for a Low-Carbon Future)

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