Energies

14 pages, 705 KiB

Open AccessArticle

Electrical Properties of Electric Vehicle Gear Oils

by Ewa Barglik, Agnieszka Skibińska, Wojciech Krasodomski, Kornel Dybich and Dariusz Sacha

Energies 2025, 18(13), 3579; https://doi.org/10.3390/en18133579 (registering DOI) - 7 Jul 2025

This study compared the oxidation resistance of three commercial oils used in electric car transmissions. The tests were carried out on a stand equipped with a gear train in accordance with ASTM D5704. The changes in physicochemical and dielectric parameters as well as [...] Read more.

This study compared the oxidation resistance of three commercial oils used in electric car transmissions. The tests were carried out on a stand equipped with a gear train in accordance with ASTM D5704. The changes in physicochemical and dielectric parameters as well as the degree of degradation were assessed by means of the FTIR spectral analysis method. Significant changes in physicochemical parameters were noticeable, including an increase in the acid number as well as an increase in kinematic viscosity at 40 °C and a decrease at 100 °C. The test results show that the oil dedicated to hybrid vehicles degraded the least, while the other oils, dedicated to electric vehicles, lost their lubricating properties to a significant extent. In addition, attention was paid to the abrasion generated during the operation of the gearbox, which has a fairly considerable impact on the change in the dielectric properties of the oils tested. In the future, more detailed research should be carried out on the effects of varying temperatures and of an electromagnetic field on the degradation of gear oils dedicated to EVs and to determine how their dielectric properties change. Full article

(This article belongs to the Section E: Electric Vehicles)

33 pages, 5059 KiB

Open AccessArticle

The Carbon Reduction Contribution of Battery Electric Vehicles: Evidence from China

by Ying Sun, Le Xiong, Rui Yan, Ruizhu Rao and Hongshuo Du

Energies 2025, 18(13), 3578; https://doi.org/10.3390/en18133578 (registering DOI) - 7 Jul 2025

Abstract

The transition to passenger car electrification is a crucial step in China’s strategic efforts to achieve carbon peak and carbon neutrality. However, previous research has not considered the variances in vehicle models. Hence, this study aims to fill this gap by comparing the [...] Read more.

The transition to passenger car electrification is a crucial step in China’s strategic efforts to achieve carbon peak and carbon neutrality. However, previous research has not considered the variances in vehicle models. Hence, this study aims to fill this gap by comparing the carbon emission reduction and economic feasibility of battery electric vehicles (BEVs) in the Chinese market, taking into account different powertrains, vehicle segments, classes, and driving ranges. Next, the study identifies the most cost-effective BEV within each market segment, employing life-cycle assessment and life cycle cost analysis methods. Moreover, at different levels of technological development, we construct three low-carbon measures, including electricity decarbonization (ED), energy efficiency improvement (EEI), and vehicle lightweight (LW), to quantify the emission mitigation potentials from different carbon reduction pathways. The findings indicate that BEVs achieve an average carbon reduction of about 31.85% compared to internal combustion engine vehicles (ICEVs), demonstrating a significant advantage in carbon reduction. However, BEVs are not economically competitive. The total life cycle cost of BEVs is 1.04–1.68 times higher than that of ICEVs, with infrastructure costs accounting for 18.8–57.8% of the vehicle’ s life cycle costs. In terms of cost-effectiveness, different models yield different results, with sedans generally outperforming sport utility vehicles (SUVs). Among sedans, both A-class and B-class sedans have already reached a point of cost-effectiveness, with the BEV400 emerging as the optimal choice. In low-carbon emission reduction scenarios, BEVs could achieve carbon reduction potentials of up to 45.3%, 14.9%, and 9.0% in the ED, EEI, and LW scenarios, respectively. Thus, electricity decarbonization exhibits the highest potential for mitigating carbon emissions, followed by energy efficiency improvement and vehicle lightweight. There are obvious differences in the stages of impact among different measures. The ED measure primarily impacts the waste treatment process (WTP) stage, followed by the vehicle cycle, while the EEI measure only affects the WTP stage. The LW measure has a complex impact on emission reductions, as the carbon reductions achieved in the WTP stage are partially offset by the increased carbon emissions in the vehicle cycle. Full article

(This article belongs to the Special Issue Measurement Systems for Electric Machines and Motor Drives: 2nd Edition)

20 pages, 1881 KiB

Open AccessArticle

Assessment of Regulation Capacity Requirements for Sending-End Grids Considering Frequency Security

by Min Li, Xiaodi Wang, Fang Liu, Xiaming Guo, Dawei Chen and Yunfeng Wen

Energies 2025, 18(13), 3577; https://doi.org/10.3390/en18133577 (registering DOI) - 7 Jul 2025

Abstract

With the large-scale integration of converter-based renewable energy into power systems and the large-scale construction of HVDC, risks associated with supply–demand imbalance and post-contingency frequency instability of sending-end power grids have significantly escalated. This paper proposes a novel method for evaluating the regulation [...] Read more.

With the large-scale integration of converter-based renewable energy into power systems and the large-scale construction of HVDC, risks associated with supply–demand imbalance and post-contingency frequency instability of sending-end power grids have significantly escalated. This paper proposes a novel method for evaluating the regulation capacity requirements of sending-end grids, addressing both normal-state power balance and post-disturbance frequency security. In normal states, multiple flexible metrics that can quantify the supply–demand imbalance trend are introduced. Then, thermal power units and energy storage serve as the benchmark to quantify the specific capacity requirements. For post-contingencies, frequency security metrics are derived based on the system frequency dynamic model with synchronous generators, renewable energy, and energy storage. The derived frequency security metrics can quantify the credible frequency regulation capacity required to ensure system stability under a predefined disturbance. A multi-objective capacity requirement assessment model for both the normal state and the post-contingency frequency regulation is ultimately formulated to determine the minimum capacity requirements. The effectiveness of the proposed evaluation method is verified using the numerical simulation based on a practical sending-end grid. Full article

(This article belongs to the Special Issue Advances in Sustainable Power and Energy Systems: 2nd Edition)

► Show Figures

Figure 1

34 pages, 1569 KiB

Open AccessReview

Microgrids’ Control Strategies and Real-Time Monitoring Systems: A Comprehensive Review

by Kayode Ebenezer Ojo, Akshay Kumar Saha and Viranjay Mohan Srivastava

Energies 2025, 18(13), 3576; https://doi.org/10.3390/en18133576 (registering DOI) - 7 Jul 2025

Abstract

Microgrids (MGs) technologies, with their advanced control techniques and real-time monitoring systems, provide users with attractive benefits including enhanced power quality, stability, sustainability, and environmentally friendly energy. As a result of continuous technological development, Internet of Things (IoT) architectures and technologies are becoming [...] Read more.

Microgrids (MGs) technologies, with their advanced control techniques and real-time monitoring systems, provide users with attractive benefits including enhanced power quality, stability, sustainability, and environmentally friendly energy. As a result of continuous technological development, Internet of Things (IoT) architectures and technologies are becoming more and more important to the future smart grid’s creation, control, monitoring, and protection of microgrids. Since microgrids are made up of several components that can function in network distribution mode using AC, DC, and hybrid systems, an appropriate control strategy and monitoring system is necessary to ensure that the power from microgrids is delivered to sensitive loads and the main grid effectively. As a result, this article thoroughly assesses MGs’ control systems and groups them based on their degree of protection, energy conversion, integration, advantages, and disadvantages. The functions of IoT and monitoring systems for MGs’ data analytics, energy transactions, and security threats are also demonstrated in this article. This study also identifies several factors, challenges, and concerns about the long-term advancement of MGs’ control technology. This work can serve as a guide for all upcoming energy management and microgrid monitoring systems. Full article

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

► Show Figures

Figure 1

27 pages, 1406 KiB

Open AccessArticle

Genetic Characterization of Natural Oil Seeps in the Carpathians and Their Relationship to the Tectonic Structure

by Wojciech Bieleń, Irena Matyasik, Marek Janiga and Agnieszka Wciślak-Oleszycka

Energies 2025, 18(13), 3575; https://doi.org/10.3390/en18133575 (registering DOI) - 7 Jul 2025

Abstract

The paper presents the geochemical characteristics of 26 selected oil seeps, more than half of which are remnants of old oil wells. The samples were collected from three tectonic units: the Magura, Silesian, and Skole units in the Polish part of the Carpathians. [...] Read more.

The paper presents the geochemical characteristics of 26 selected oil seeps, more than half of which are remnants of old oil wells. The samples were collected from three tectonic units: the Magura, Silesian, and Skole units in the Polish part of the Carpathians. The analyzed seeps are mainly located on outcrops of Inoceramian beds within the Magura nappe, the Krosno Beds and Transition Beds in the Silesian nappe, as well as the Menilite Beds of the Skole unit. The study primarily focused on genetic characteristics, which were used to correlate the seeps with the oils from the deposits of these tectonic units and to assess the degree of secondary alterations. All hydrocarbon seeps were analyzed in terms of their location on surface cross-sections, and attempts were made to assign them features based on the classification proposed in 1952, which takes into account the tectonic characteristics of the regions where the seeps were identified. In the general genetic characterization, these seeps did not show significant differences, suggesting a similar source of supply as the crude oils. Among the analyzed seeps, three genetic groups were distinguished. For correlation purposes, information from published materials on crude oils and their genetic characteristics was used. Of the five classification types described in the literature, only two could be assigned to those occurring in the Carpathians. Considering the tectonic structure and the location of the seeps (based on surface cross-sections), it has been determined that most of the analyzed seeps are the result of migration along faults connecting source rocks or, less frequently, deformed deep accumulations with the surface. Full article

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

39 pages, 7836 KiB

Open AccessReview

Synchronverter Control Strategy: A Review of Different Improvements and Applications

by Michell Josep Quintero-Durán, John Edwin Candelo-Becerra, Mario Eduardo González-Niño, Saúl Andrés Hernández-Moreno and Rodolpho Fernando Váz

Energies 2025, 18(13), 3574; https://doi.org/10.3390/en18133574 (registering DOI) - 7 Jul 2025

Abstract

In power grids that integrate renewable energy sources, the virtual synchronous machine (VSM) or synchronverter offers a viable solution to the challenge posed by reduced inertia. This technology employs inverters to transfer power to the electrical network that relies on a control algorithm [...] Read more.

In power grids that integrate renewable energy sources, the virtual synchronous machine (VSM) or synchronverter offers a viable solution to the challenge posed by reduced inertia. This technology employs inverters to transfer power to the electrical network that relies on a control algorithm emulating the dynamic behavior of synchronous machines. Over the past decade, it has been applied in various contexts, leveraging its control structure based on the fundamental equations of synchronous machines. Although several review articles have been published on control strategies for grid-forming inverters, they often lack a specific focus on recent developments related to the synchronverter. Therefore, this paper aims to fill that gap by presenting a detailed review on high-quality research databases to retrieve recent documents published in recent years. These documents were classified according to journals, conferences, and books. A keyword bibliographic analysis was performed to identify the attractive topics related to the synchronverter control strategy. The paper reviews recent improvements in and applications of the synchronverter, identifying emerging trends and new potential use cases to provide a workflow guide for readers and researchers, as the documents are presented in comprehensive tables, streamlining the process of locating specific references. In addition, some advantages and disadvantages of synchronverters are reported. Full article

► Show Figures

Figure 1

22 pages, 2190 KiB

Open AccessArticle

Thermal Impacts of Air Cavities Associated with Insulated Panels Deployed for Exterior Building Envelope Assemblies

by Utsav Dahal and Moncef Krarti

Energies 2025, 18(13), 3573; https://doi.org/10.3390/en18133573 (registering DOI) - 7 Jul 2025

Abstract

This paper presents a comprehensive investigation to evaluate the impacts of air cavities between existing walls and insulated panels on the overall R-values of the retrofitted building envelope systems, addressing a key challenge in exterior envelope retrofitting. The effects of several factors are [...] Read more.

This paper presents a comprehensive investigation to evaluate the impacts of air cavities between existing walls and insulated panels on the overall R-values of the retrofitted building envelope systems, addressing a key challenge in exterior envelope retrofitting. The effects of several factors are considered including the air cavity thickness (ranging from 0.1 cm to 5 cm), airflow velocity (varying between 0.1 m/s and 1 m/s), and surface emissivity (set between 0.1 and 0.9), in addition to the thickness of the insulated panels (ranging from 1 cm to 7 cm). It is found that any increase in the air cavity thickness increases the overall R-values of the building envelope assemblies when air is trapped within the sealed cavity. However, when air convection is prevalent, the overall R-value of the retrofitted walls decreases with any increase in air velocity and air cavity thickness. For sealed air cavities, the analysis results show a 9% improvement in R-value of the retrofitted walls. However, the R-value of retrofitted walls with unsealed air cavities can degrade by 76% and 81% for natural and forced air flows, respectively. Emissivity adjustment is found to be the most effective in improving the thermal performance of building envelopes with sealed air cavities, increasing the R-value of retrofitted walls by 13.6% when reduced from 0.9 to 0.1. Full article

(This article belongs to the Special Issue Energy Efficiency and Energy Performance in Buildings—2nd Edition)

28 pages, 3966 KiB

Open AccessArticle

Photovoltaic Power Forecasting Based on Variational Mode Decomposition and Long Short-Term Memory Neural Network

by Zhijian Hou, Yunhui Zhang, Xuemei Cheng and Xiaojiang Ye

Energies 2025, 18(13), 3572; https://doi.org/10.3390/en18133572 (registering DOI) - 7 Jul 2025

Abstract

The accurate forecasting of photovoltaic (PV) power is vital for grid stability. This paper presents a hybrid forecasting model that combines Variational Mode Decomposition (VMD) and Long Short-Term Memory (LSTM). The model uses VMD to decompose the PV power into modal components and [...] Read more.

The accurate forecasting of photovoltaic (PV) power is vital for grid stability. This paper presents a hybrid forecasting model that combines Variational Mode Decomposition (VMD) and Long Short-Term Memory (LSTM). The model uses VMD to decompose the PV power into modal components and residuals. These components are combined with meteorological variables and their first-order differences, and feature extraction techniques are used to generate multiple sets of feature vectors. These vectors are utilized as inputs for LSTM sub-models, which predict the modal components and residuals. Finally, the aggregation of prediction results is used to achieve the PV power prediction. Validated on Australia’s 1.8 MW Yulara PV plant, the model surpasses 13 benchmark models, achieving an MAE of 63.480 kW, RMSE of 81.520 kW, and R² of 92.3%. Additionally, the results of a paired t-test showed that the mean differences in the MAE and RMSE were negative, and the 95% confidence intervals for the difference did not include zero, indicating statistical significance. To further evaluate the model’s robustness, white noise with varying levels of signal-to-noise ratios was introduced to the photovoltaic power and global radiation signals. The results showed that the model exhibited higher prediction accuracy and better noise tolerance compared to other models. Full article

(This article belongs to the Section A2: Solar Energy and Photovoltaic Systems)

► Show Figures

Figure 1

18 pages, 33192 KiB

Open AccessArticle

Fault Cycling and Its Impact on Hydrocarbon Accumulation: Insights from the Neogene Southwestern Qaidam Basin

by Zhaozhou Chen, Zhen Liu, Jun Li, Fei Zhou, Zihao Feng and Xinruo Ma

Energies 2025, 18(13), 3571; https://doi.org/10.3390/en18133571 (registering DOI) - 7 Jul 2025

Abstract

Building upon the geological cycle theory, this study proposes fault cycles as a critical component of tectonic cyclicity in petroliferous basins. Focusing on reservoir-controlling faults in the southwestern Qaidam Basin, we systematically analyze fault architectures and identify three distinct fault activation episodes: the [...] Read more.

Building upon the geological cycle theory, this study proposes fault cycles as a critical component of tectonic cyclicity in petroliferous basins. Focusing on reservoir-controlling faults in the southwestern Qaidam Basin, we systematically analyze fault architectures and identify three distinct fault activation episodes: the Lulehe Formation (LLH Fm.), the upper part of the Xiaganchaigou Formation (UXG Fm.), and the Shizigou Formation (SZG Fm.). Three types of fault cycle models are established. These fault cycles correlate with the evolution of regional tectonic stress fields, corresponding to the Cenozoic transition from extensional to compressional stress regimes in the basin. Mechanistic analysis reveals the hierarchical control of fault cycles in hydrocarbon systems: the early cycle governs the proto-basin geometry and low-amplitude structural trap development; the middle cycle affects the source rock distribution; and the late cycle controls trap finalization and hydrocarbon migration. This study proposes a fault cycle-controlled accumulation model, providing a dynamic perspective that shifts from conventional static fault concepts to reveal fault activity periodicity and its critical multi-phase control over hydrocarbon migration and accumulation, essential for exploration in multi-episodic fault provinces. Full article

(This article belongs to the Special Issue Petroleum Exploration, Development and Transportation)

► Show Figures

Figure 1

18 pages, 1011 KiB

Open AccessOpinion

The Fifth Freedom: Shaping EU Innovation Policy for Renewable Energy Storage and Decarbonization

by Esmeralda Colombo

Energies 2025, 18(13), 3570; https://doi.org/10.3390/en18133570 (registering DOI) - 7 Jul 2025

Abstract

This article proposes recognizing innovation as the European Union’s “fifth freedom”, alongside the free movement of goods, services, capital, and people, with the aim of embedding it into renewable energy legislation. Focusing on renewable energy storage—a critical but overlooked component of decarbonization—it identifies [...] Read more.

This article proposes recognizing innovation as the European Union’s “fifth freedom”, alongside the free movement of goods, services, capital, and people, with the aim of embedding it into renewable energy legislation. Focusing on renewable energy storage—a critical but overlooked component of decarbonization—it identifies structural barriers in EU cleantech innovation, including regulatory fragmentation, slow financing, and weak industrial coordination. To address these, this article introduces the Risk–Resilience–Reward (RRR) framework, a strategic tool for more anticipatory policymaking. It outlines how the proposed Clean Energy Delivery Agency and Clean Energy Deployment Fund could operationalize the RRR framework to accelerate storage deployment and strengthen EU competitiveness. Embedding purpose-led principles in energy policy, this article positions storage as the “unsung hero of decarbonization” and offers takeaways for advancing a just, sustainable EU economy. Full article

(This article belongs to the Special Issue Management and Economics in the Energy Policy of the 21st Century: Theoretical Approaches and Practical Solutions)

► Show Figures

Figure 1

15 pages, 1486 KiB

Open AccessArticle

Assessment of Building Compactness at Initial Design Stage of Single-Family Houses

by Edwin Koźniewski

Energies 2025, 18(13), 3569; https://doi.org/10.3390/en18133569 - 7 Jul 2025

Abstract

The paper is the culmination of research on geometric aspects of assessing the energy demand of a single-family house. In a recent study, two collections of single-family houses were analyzed: (a) a collection of 21 with outlines assumed a priori so that the [...] Read more.

The paper is the culmination of research on geometric aspects of assessing the energy demand of a single-family house. In a recent study, two collections of single-family houses were analyzed: (a) a collection of 21 with outlines assumed a priori so that the building area was constant (which is not achievable in practice) and (b) a collection of 33 real buildings, recently designed by the Polish design studio Galeria Domów. These examples show the functioning of the indicators analyzed by the author in earlier papers and indicate the

{R C}_{s q}

indicator that best reflects the assessment of building compactness in percentage points in relation to the ideal shape of the building plan, which is a square. The

{R C}_{s q}

index is economically expressed by only two parameters, namely the base area

A_{f}

and the building outline perimeter

P

, and therefore is easy to implement in the BIM system and at the same time covers high-rise buildings. As it turned out, the tested buildings from Galeria Domów have very good geometric and therefore energy efficiency. The above-mentioned indicator also highlights the advisability of analyzing the heated part in addition to the standard full-contour analyses. Full article

(This article belongs to the Special Issue Ultra-Low Energy Consumption and Zero-Energy Buildings in Response to Climate Change)

► Show Figures

Figure 1

24 pages, 2080 KiB

Open AccessArticle

Techno-Economic Analysis of Non-Wire Alternative (NWA) Portfolios Integrating Energy Storage Systems (ESS) with Photovoltaics (PV) or Demand Response (DR) Resources Across Various Load Profiles

by Juwon Park and Sung-Kwan Joo

Energies 2025, 18(13), 3568; https://doi.org/10.3390/en18133568 - 7 Jul 2025

Abstract

The Non-Wire Alternative (NWA) approach has gained attention as a strategy to replace or defer traditional grid infrastructure upgrades by leveraging integrated solutions combining Energy Storage Systems (ESSs) with Distributed Energy Resources (DERs). The overall feasibility and economics of distributed flexibility solutions can [...] Read more.

The Non-Wire Alternative (NWA) approach has gained attention as a strategy to replace or defer traditional grid infrastructure upgrades by leveraging integrated solutions combining Energy Storage Systems (ESSs) with Distributed Energy Resources (DERs). The overall feasibility and economics of distributed flexibility solutions can be enhanced by leveraging the synergies among various DERs for NWA deployment. This study presents the results of a techno-economic analysis of an NWA portfolio that integrates Photovoltaic (PV) generation and Demand Response (DR) resources with ESSs. Three representative load profiles are analyzed under different load growth scenarios: a balanced mix of industrial, commercial, and residential loads; residential-dominant loads; and commercial/industrial-dominant loads. The analysis shows that the combined deployment of PVs and DRs significantly reduces the required ESS capacity. Furthermore, economic analysis based on Benefit–Cost Analysis (BCA) demonstrated that combining ESSs with either PVs or DRs enhances economic efficiency compared with an NWA portfolio that relies on ESSs alone, particularly under low-capacity factor conditions. However, the effectiveness of a DR or PV varies depending on the load profile. DR is less effective when the peak load durations are prolonged, whereas PV offers limited economic benefits under residential loads with the evening peak demand. These techno-economic results highlight the importance of tailoring NWA portfolios to specific load conditions to maximize both technical performance and economic value. Full article

(This article belongs to the Special Issue Innovations and Recent Trends in Power Systems: Smart Grids, Energy Storage Systems and Electric Vehicle Integrations)

► Show Figures

Figure 1

18 pages, 2763 KiB

Open AccessArticle

A Multi-Timescale Operational Strategy for Active Distribution Networks with Load Forecasting Integration

by Dongli Jia, Zhaoying Ren, Keyan Liu, Kaiyuan He and Zukun Li

Energies 2025, 18(13), 3567; https://doi.org/10.3390/en18133567 - 7 Jul 2025

Abstract

To enhance the operational stability of distribution networks during peak periods, this paper proposes a multi-timescale operational method considering load forecasting impacts. Firstly, the Crested Porcupine Optimizer (CPO) is employed to optimize the hyperparameters of long short-term memory (LSTM) networks for an accurate [...] Read more.

To enhance the operational stability of distribution networks during peak periods, this paper proposes a multi-timescale operational method considering load forecasting impacts. Firstly, the Crested Porcupine Optimizer (CPO) is employed to optimize the hyperparameters of long short-term memory (LSTM) networks for an accurate prediction of the next-day load curves. Building on this foundation, a multi-timescale optimization strategy is developed: During the day-ahead operation phase, a conservation voltage reduction (CVR)-based regulation plan is formulated to coordinate the control of on-load tap changers (OLTCs) and distributed resources, alleviating peak-shaving pressure on the upstream grid. In the intraday optimization phase, real-time adjustments of OLTC tap positions are implemented to address potential voltage violations, accompanied by an electrical distance-based control strategy for flexible adjustable resources, enabling rapid voltage recovery and enhancing system stability and robustness. Finally, a modified IEEE-33 node system is adopted to verify the effectiveness of the proposed multi-timescale operational method. The method demonstrates a load forecasting accuracy of 93.22%, achieves a reduction of 1.906% in load power demand, and enables timely voltage regulation during intraday limit violations, effectively maintaining grid operational stability. Full article

► Show Figures

Figure 1

25 pages, 668 KiB

Open AccessArticle

Bridging the Energy Divide: An Analysis of the Socioeconomic and Technical Factors Influencing Electricity Theft in Kinshasa, DR Congo

by Patrick Kankonde and Pitshou Bokoro

Energies 2025, 18(13), 3566; https://doi.org/10.3390/en18133566 - 7 Jul 2025

Abstract

Electricity theft remains a persistent challenge, particularly in developing economies where infrastructure limitations and socioeconomic disparities contribute to illegal connections. This study analyzes the determinants influencing electricity theft in Kinshasa, the Democratic Republic of Congo, using a logistic regression model applied to 385 [...] Read more.

Electricity theft remains a persistent challenge, particularly in developing economies where infrastructure limitations and socioeconomic disparities contribute to illegal connections. This study analyzes the determinants influencing electricity theft in Kinshasa, the Democratic Republic of Congo, using a logistic regression model applied to 385 observations, which includes random bootstrapping sampling for enhanced stability and power analysis validation to confirm the adequacy of the sample size. The model achieved an AUC of 0.86, demonstrating strong discriminatory power, while the Hosmer–Lemeshow test (p = 0.471) confirmed its robust fit. Our findings indicate that electricity supply quality, financial stress, tampering awareness, and billing transparency are key predictors of theft likelihood. Households experiencing unreliable service and economic hardship showed higher theft probability, while those receiving regular invoices and alternative legal energy solutions exhibited lower risk. Lasso regression was implemented to refine predictor selection, ensuring model efficiency. Based on these insights, a multifaceted policy approach—including grid modernization, prepaid billing systems, awareness campaigns, and regulatory enforcement—is recommended to mitigate electricity theft and promote sustainable energy access in urban environments. Full article

(This article belongs to the Section F4: Critical Energy Infrastructure)

► Show Figures

Figure 1

23 pages, 546 KiB

Open AccessArticle

Environmental and Social Dimensions of Energy Transformation Using Geothermal Energy

by Michał Kaczmarczyk and Anna Sowiżdżał

Energies 2025, 18(13), 3565; https://doi.org/10.3390/en18133565 - 7 Jul 2025

Abstract

The use of geothermal energy is gaining strategic importance in the context of sustainable development and the decarbonisation of local energy systems. As a stable and low-emission renewable energy source, geothermal energy offers tangible environmental and social benefits, including improved air quality, reduced [...] Read more.

The use of geothermal energy is gaining strategic importance in the context of sustainable development and the decarbonisation of local energy systems. As a stable and low-emission renewable energy source, geothermal energy offers tangible environmental and social benefits, including improved air quality, reduced greenhouse gas emissions, and enhanced energy independence. This article presents a comprehensive overview of the social dimensions of geothermal energy deployment in Poland, with a particular focus on environmental impacts, public acceptance, and participatory governance. Based on a Polish geothermal district heating system example, the paper demonstrates that geothermal projects can significantly reduce local pollution and support low-carbon economic transitions. The study includes a comparative assessment of avoided emissions, a critical discussion of potential social barriers, and SWOT and PESTEL analyses identifying systemic enablers and constraints. The authors argue that for geothermal energy to fulfil its sustainability potential, it must be supported by inclusive planning, transparent communication, and a holistic policy framework integrating environmental, technological, and social criteria. Full article

► Show Figures

Figure 1

23 pages, 3988 KiB

Open AccessArticle

Research on Equivalent One-Dimensional Cylindrical Modeling Method for Lead–Bismuth Fast Reactor Fuel Assemblies

by Jinjie Xiao, Yongfa Zhang, Song Li, Ling Chen, Jiannan Li and Cong Zhang

Energies 2025, 18(13), 3564; https://doi.org/10.3390/en18133564 - 6 Jul 2025

Abstract

The lead-cooled fast reactor (LFR), a Generation IV nuclear system candidate, presents unique neutronic characteristics distinct from pressurized water reactors. Its neutron spectrum spans wider energy ranges with fast neutron dominance, exhibiting resonance phenomena across energy regions. These features require a fine energy [...] Read more.

The lead-cooled fast reactor (LFR), a Generation IV nuclear system candidate, presents unique neutronic characteristics distinct from pressurized water reactors. Its neutron spectrum spans wider energy ranges with fast neutron dominance, exhibiting resonance phenomena across energy regions. These features require a fine energy group structure for fuel lattice calculations, significantly increasing computational demands. To balance local heterogeneity modeling with computational efficiency, researchers across the world adopt fuel assembly equivalence methods using 1D cylindrical models through volume equivalence principles. This approach enables detailed energy group calculations in simplified geometries, followed by lattice homogenization for few-group parameter generation, effectively reducing whole-core computational loads. However, limitations emerge when handling strongly heterogeneous components like structural/control rods. This study investigates the 1D equivalence method’s accuracy in lead–bismuth fast reactors under various fuel assembly configurations. Through comprehensive analysis of material distributions and their equivalence impacts, the applicability of the one-dimensional equivalence approach to fuel assemblies of different geometries and material types is analyzed in this paper. The research further proposes corrective solutions for low-accuracy scenarios, enhancing computational method reliability. This paper is significant in its optimization of the physical calculation and analysis process of a new type of fast reactor component and has important engineering application value. Full article

(This article belongs to the Section B4: Nuclear Energy)

► Show Figures

Figure 1

36 pages, 6674 KiB

Open AccessArticle

Marangoni Convection of Self-Rewetting Fluid Layers with a Deformable Interface in a Square Enclosure and Driven by Imposed Nonuniform Heat Energy Fluxes

by Bashir Elbousefi, William Schupbach and Kannan N. Premnath

Energies 2025, 18(13), 3563; https://doi.org/10.3390/en18133563 - 6 Jul 2025

Abstract

Fluids that exhibit self-rewetting properties, such as aqueous long-chain alcohol solutions, display a unique quadratic relationship between surface tension and temperature and are marked by a positive gradient. This characteristic leads to distinctive patterns of thermocapillary convection and associated interfacial dynamics, setting self-rewetting [...] Read more.

Fluids that exhibit self-rewetting properties, such as aqueous long-chain alcohol solutions, display a unique quadratic relationship between surface tension and temperature and are marked by a positive gradient. This characteristic leads to distinctive patterns of thermocapillary convection and associated interfacial dynamics, setting self-rewetting fluids apart from normal fluids (NFs). The potential to improve heat transfer using self-rewetting fluids (SRFs) is garnering interest for use in various technologies, including low-gravity conditions and microfluidic systems. Our research aims to shed light on the contrasting behaviors of SRFs in comparison to NFs regarding interfacial transport phenomena. This study focuses on the thermocapillary convection in SRF layers with a deformable interface enclosed inside a closed container modeled as a square cavity, which is subject to nonuniform heating, represented using a Gaussian profile for the heat flux variation on one of its sides, in the absence of gravity. To achieve this, we have enhanced a central-moment-based lattice Boltzmann method (LBM) utilizing three distribution functions for tracking interfaces, computing two-fluid motions with temperature-dependent surface tension and energy transport, respectively. Through numerical simulations, the impacts of several characteristic parameters, including the viscosity and thermal conductivity ratios, as well as the surface tension–temperature sensitivity parameters, on the distribution and magnitude of the thermocapillary-driven motion are examined. In contrast to that in NFs, the counter-rotating pair of vortices generated in the SRF layers, due to the surface tension gradient at the interface, is found to be directed toward the SRF layers’ hotter zones. Significant interfacial deformations are observed, especially when there are contrasts in the viscosities of the SRF layers. The thermocapillary convection is found to be enhanced if the bottom SRF layer has a higher thermal conductivity or viscosity than that of the top layer or when distributed, rather than localized, heating is applied. Furthermore, the higher the magnitude of the effect of the dimensionless quadratic surface tension sensitivity coefficient on the temperature, or of the effect of the imposed heat flux, the greater the peak interfacial velocity current generated due to the Marangoni stresses. In addition, an examination of the Nusselt number profiles reveals significant redistribution of the heat transfer rates in the SRF layers due to concomitant nonlinear thermocapillary effects. Full article

(This article belongs to the Section J1: Heat and Mass Transfer)

► Show Figures

Figure 1

19 pages, 2227 KiB

Open AccessArticle

A Comparative Study of Fission Yield Libraries Between ORIGEN2 and ENDF/B-VIII.0 for Molten Salt Reactor Burnup Calculation

by Yunfei Zhang, Guifeng Zhu, Yang Zou, Jian Guo, Bo Zhou, Rui Yan and Ao Zhang

Energies 2025, 18(13), 3562; https://doi.org/10.3390/en18133562 - 6 Jul 2025

Abstract

As a promising nuclear technology, molten salt reactors (MSRs) have a bright future in the energy sector due to their unique advantages such as high efficiency, safety, and fuel flexibility. However, the accurate analysis of fission products in MSRs requires reliable fission yield [...] Read more.

As a promising nuclear technology, molten salt reactors (MSRs) have a bright future in the energy sector due to their unique advantages such as high efficiency, safety, and fuel flexibility. However, the accurate analysis of fission products in MSRs requires reliable fission yield data. Current reactor burnup analysis often uses the ORIGEN2 code, whose fission yield libraries mainly originate from the outdated 1970s ENDF/B-VI nuclear database, thus risking data obsolescence. This study evaluates ORIGEN2’s fission yield libraries (THERMAL, PWRU, PWRU50) against the modern ENDF/B-VIII.0 library. Through a comprehensive comparative analysis of Oak Ridge National Laboratory’s Molten Salt Reactor Experiment (MSRE) model, numerical simulations reveal library-dependent differences in MSR burnup characteristics. The PWRU library best matches ENDF/B-VIII.0 for U-235-fueled cases in keff results, while the PWRU50 library has minimal keff deviation in U-233-fueled setups. Moreover, in both fuel cases, the fission yield library was found to significantly affect the activity of key radionuclides, including Kr-85, Kr-85m, I-133m, Cs-136, Sn-123, Sn-125, Sn-127, Sb-124, Sb-125, Cd-115m, Te-125m, Te-129m, etc. Additionally, the fission gas decay heat power calculated via the ORIGEN2 library is over 20% lower than that from the ENDF/B-VIII.0 library tens of days after shutdown, mainly due to differences in long-lived Kr-85 production. These findings highlight the need to update traditional fission yield libraries in burnup codes. For next-generation MSR designs, this is crucial to ensure accurate safety assessments and the effective development of this promising energy technology. Full article

(This article belongs to the Special Issue Molten Salt Reactors: Innovations and Challenges in Nuclear Energy)

► Show Figures

Figure 1

27 pages, 2952 KiB

Open AccessArticle

Designing a Thermoacoustic Cooler for Energy Applications: Experimental Insights

by Leszek Remiorz, Krzysztof Grzywnowicz, Eryk Remiorz and Wojciech Uchman

Energies 2025, 18(13), 3561; https://doi.org/10.3390/en18133561 - 6 Jul 2025

Abstract

Thermoacoustic devices, such as refrigerators and heat pumps, present unique measurement challenges due to the simultaneous presence of rapidly fluctuating acoustic parameters and more stable thermal variables. Accurate and informative measurements during operation are crucial for developing effective control algorithms and optimizing performance [...] Read more.

Thermoacoustic devices, such as refrigerators and heat pumps, present unique measurement challenges due to the simultaneous presence of rapidly fluctuating acoustic parameters and more stable thermal variables. Accurate and informative measurements during operation are crucial for developing effective control algorithms and optimizing performance under specific conditions. However, issues like inappropriate sampling frequencies and excessive data storage can lead to unintended averaging, compromising measurement quality. This study introduces a comprehensive experimental procedure aimed at enhancing the reliability of measurements in thermoacoustic systems. The approach encompasses meticulous experimental design, identification of measurement uncertainties and influencing factors during standard operation, and a statistical uncertainty analysis. Experimental findings reveal a significant reduction in temperature measurement uncertainty with increased thermoacoustic channel length and highlight the substantial impact of device structural features on performance. These insights are instrumental for refining measurement protocols and advancing the development of efficient thermoacoustic technologies. Full article

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

► Show Figures

Figure 1

Journal Description

Energies

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI