Energies

28 pages, 3790 KiB

Open AccessArticle

PEMFC Semi-Empirical Model Improvement by Reconstructing Concentration Loss

by Qinwen Yang, Xuan Liu, Gang Xiao and Zhen Zhang

Energies 2025, 18(7), 1754; https://doi.org/10.3390/en18071754 (registering DOI) - 31 Mar 2025

The performance of proton exchange membrane fuel cells (PEMFCs) is greatly affected by their operating parameters, especially at high current densities. An advanced concentration loss model is proposed to improve a semi-empirical model describing PEMFC polarization, with the aim of accurate prediction at [...] Read more.

The performance of proton exchange membrane fuel cells (PEMFCs) is greatly affected by their operating parameters, especially at high current densities. An advanced concentration loss model is proposed to improve a semi-empirical model describing PEMFC polarization, with the aim of accurate prediction at the whole current density interval from low to high levels. Experiments are designed to verify the improved semi-empirical model. Model comparison shows that the improved semi-empirical model has a better prediction accuracy and generalization ability than others. The effects of operating parameters and structural parameters on PEMFC performance are analyzed. The results indicate that a relatively high operating temperature, pressure, and gas diffusion layer (GDL) porosity can increase PEMFC performance. The influence of relative humidity and PEM thickness on PEMFC performance is different at low and high current densities. A relatively high humidity can improve PEMFC performance at a low current density, but PEMFC performance will be reduced if the relative humidity is too high at a high current density. A thinner PEM thickness can improve PEMFC performance at a low current density, but PEMFC performance does not necessarily improve with a decreasing PEM thickness at a high current density. Overall, the improved semi-empirical model realizes an accurate analysis of PEMFC performance from a low to high current density. Full article

(This article belongs to the Section D2: Electrochem: Batteries, Fuel Cells, Capacitors)

24 pages, 1825 KiB

Open AccessArticle

Decision-Making and Selection Framework for Potential Implementation of Concentrated Solar Power Technologies: Case Study

by Maycon Figueira Magalhães, Boniface Dominick Mselle and Francisca Galindo

Energies 2025, 18(7), 1753; https://doi.org/10.3390/en18071753 (registering DOI) - 31 Mar 2025

Abstract

The decarbonization of industrial processes requires efficient and scalable renewable energy solutions. Concentrated Solar Power (CSP) technology stands out by providing both electricity and high-temperature heat, yet its optimal deployment remains a challenge. This study presents an innovative framework for selecting and optimizing [...] Read more.

The decarbonization of industrial processes requires efficient and scalable renewable energy solutions. Concentrated Solar Power (CSP) technology stands out by providing both electricity and high-temperature heat, yet its optimal deployment remains a challenge. This study presents an innovative framework for selecting and optimizing CSP technologies tailored for potential industrial practical applications. In this study, a multi-phase approach is deployed integrating a decision matrix, performance simulations using SOLARPILOT and SAM, and techno-economic evaluation to identify the best CSP solution. The study addresses the feasibility of four candidate CSP technologies, the characteristics of deployment areas, operation parameters such as energy storage time, and characteristics of energy storage material (comparing commercially available materials and an innovative molten salt named FERT-1). The results highlight solar towers as the most suitable technology, while the characteristics of the deployment can lead to over 3.2% difference in annual energy generation (when comparing between two areas, A1 and A2). Regarding energy storage, an optimal storage time of 11 h was identified, achieving a Levelized Cost of Electricity (LCOE) of 24–25 cents/kWh and a 31–32% energy capacity factor. Moreover, regarding energy storage material, the innovative molten salt highlighted improved thermal efficiency. Full article

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

28 pages, 2383 KiB

Open AccessArticle

Reduced-Order Modeling and Stability Analysis of Grid-Following and Grid-Forming Hybrid Renewable Energy Plants

by Yue Ma, Ning Chen and Luming Ge

Energies 2025, 18(7), 1752; https://doi.org/10.3390/en18071752 (registering DOI) - 31 Mar 2025

Abstract

The control methods of energy systems can be categorized into grid-following and grid-forming types. The grid-following control method relies on grid synchronization and is prone to stability issues in weak grid conditions. By contrast, the grid-forming control method exhibits synchronous machine characteristics, providing [...] Read more.

The control methods of energy systems can be categorized into grid-following and grid-forming types. The grid-following control method relies on grid synchronization and is prone to stability issues in weak grid conditions. By contrast, the grid-forming control method exhibits synchronous machine characteristics, providing voltage support to the system, but potentially introducing stability risks under strong grid conditions. Constructing a grid-following and grid-forming hybrid renewable energy plant can effectively enhance the system’s support capability and ensure reliable operation. However, the interactions among multiple inverters are complex, and traditional modeling methods are inadequate to meet the modeling requirements for such systems. To effectively address this problem, this paper presents a reduced-order modeling method that simplifies the complex system into a simple system consisting of an equivalent grid-following, an equivalent grid-forming, and grid impedance through frequency decoupling and the aggregation of similar inverters. Furthermore, this study employs both the Nyquist stability criterion and the harmonic characteristic analysis method to elucidate how the capacity ratio between grid-following and grid-forming affects system stability. Full article

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

21 pages, 7250 KiB

Open AccessArticle

Exploring the Future Energy Value of Long-Duration Energy Storage

by Anna H. Schleifer, Stuart M. Cohen, Wesley Cole, Paul Denholm and Nate Blair

Energies 2025, 18(7), 1751; https://doi.org/10.3390/en18071751 (registering DOI) - 31 Mar 2025

Abstract

Long-duration energy storage is commonly viewed as a key technology for providing flexibility to the grid and broader energy systems over a multidecadal time frame. However, prior work has typically used present-day grid infrastructures to characterize the relationship between the duration and arbitrage [...] Read more.

Long-duration energy storage is commonly viewed as a key technology for providing flexibility to the grid and broader energy systems over a multidecadal time frame. However, prior work has typically used present-day grid infrastructures to characterize the relationship between the duration and arbitrage value of storage in electricity markets. This study leverages established National Renewable Energy Laboratory grid planning and operations tools, analysis, and data to execute a price-taker model of an energy storage system for several 8760 h price series representative of current and future contiguous United States grid infrastructures with varying shares of variable renewable energy (VRE). We find that the total value of energy storage typically increases with VRE shares, but any increase in the relative value of longer storage durations over time depends on the region and grid mix. Some regions see incremental value increasing notably, up to 20–40 h in 2050, while others do not. The negative effect of lower roundtrip efficiency on value is also found to be scenario-dependent, with the energy value in higher VRE scenarios being less sensitive to roundtrip efficiency and more supportive of longer storage durations. Long-duration storage value and deployment potential are a function of evolving electricity sector infrastructure, markets, and policy, making it critical to consistently revisit potential long-duration storage contributions to the grid. Full article

(This article belongs to the Section D: Energy Storage and Application)

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30 pages, 1428 KiB

Open AccessArticle

Revolutionizing Electric Vehicle Charging Stations with Efficient Deep Q Networks Powered by Multimodal Bioinspired Analysis for Improved Performance

by Sugunakar Mamidala, Yellapragada Venkata Pavan Kumar and Rammohan Mallipeddi

Energies 2025, 18(7), 1750; https://doi.org/10.3390/en18071750 (registering DOI) - 31 Mar 2025

Abstract

The rapid growth of electric vehicle (EV) adoption presents significant challenges in planning efficient charging infrastructure, including suboptimal station placement, energy consumption, and rising infrastructural costs. The conventional methods, such as grey wolf optimization (GWO), fail to address real-time user demand and dynamic [...] Read more.

The rapid growth of electric vehicle (EV) adoption presents significant challenges in planning efficient charging infrastructure, including suboptimal station placement, energy consumption, and rising infrastructural costs. The conventional methods, such as grey wolf optimization (GWO), fail to address real-time user demand and dynamic factors like fluctuating grid loads and environmental impact. These approaches rely on fixed models, often leading to inefficient energy use, higher operational costs, and increased traffic congestion. This paper proposes a novel framework that integrates deep Q networks (DQNs) for real-time charging optimization, coupled with multimodal bioinspired algorithms like ant lion optimization (ALO) and moth flame optimization (MFO). Unlike conventional geographic placement models that overlook evolving travel patterns, this system dynamically adapts to user behavior, optimizing both onboard and offboard charging systems. The DQN enables continuous learning from changing demand and grid conditions, while ALO and MFO identify optimal station locations, reducing energy consumption and emissions. The proposed framework incorporates dynamic pricing and demand response strategies. These adjustments help balance energy usage, reducing costs and preventing overloading of the grid during peak times, offering real-time adaptability, optimized station placement, and energy efficiency. To improve the performance of the system, the proposed framework ensures more sustainable, cost-effective EV infrastructural planning, minimized environmental impacts, and enhanced charging efficiency. From the results for the proposed system, we recorded various performance parameters such as the installation cost, which decreased to USD 1200 per unit, i.e., a 20% cost efficiency increase, optimal energy utilization increases to 85% and 92% during peak hours and off-peak hours respectively, a charging slot availability increase to 95%, a 30% carbon emission reduction, and 95% performance retention under the stress condition. Further, the power quality is improved by reducing the sag, swell, flicker, and notch by 2 V, 3 V, 0.05 V, and 0.03 V, respectively, with an increase in efficiency to 89.9%. This study addresses critical gaps in real-time flexibility, cost-effective station deployment, and grid resilience by offering a scalable and intelligent EV charging solution. Full article

(This article belongs to the Special Issue Sustainable Transportation Systems with Electric and Autonomous Vehicles)

16 pages, 3996 KiB

Open AccessArticle

A Comprehensive System for Protection of Photovoltaic Installations in Normal and Emergency Conditions

by Konrad Seklecki, Marek Olesz, Marek Adamowicz, Mikołaj Nowak, Leszek Sławomir Litzbarski, Kamil Balcarek and Jacek Grochowski

Energies 2025, 18(7), 1749; https://doi.org/10.3390/en18071749 (registering DOI) - 31 Mar 2025

Abstract

The rapid growth of the photovoltaic industry necessitates the development of innovative solutions to ensure the safe operation of these systems. One of the most critical challenges in photovoltaic installations is ensuring protection against electric shock under both operational and emergency conditions, as [...] Read more.

The rapid growth of the photovoltaic industry necessitates the development of innovative solutions to ensure the safe operation of these systems. One of the most critical challenges in photovoltaic installations is ensuring protection against electric shock under both operational and emergency conditions, as well as minimizing the risk of fire spread in case of an installation fire. Existing safety measures do not provide a sufficient level of protection, particularly in terms of fire safety. To address these shortcomings, a comprehensive safety system has been developed. This system includes a photovoltaic panel shutter and a safety switch device, which enables the short-circuiting of individual panel outputs while also providing a break in the DC circuit. The proposed solution can be classified as part of the Balance of System (BoS). The effectiveness of this safety system has been validated through both numerical simulations and experimental investigations. Furthermore, an economic analysis indicates that implementing this system will not significantly impact the overall cost of a photovoltaic system. Full article

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

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26 pages, 3050 KiB

Open AccessArticle

Navigating Environmental Concerns: Unveiling the Role of Economic Governance, Energy Transition, and Population Aging on Transport-Based CO₂ Emissions in China

by Huan Wu, Jianguo Du and Yasir Rasool

Energies 2025, 18(7), 1748; https://doi.org/10.3390/en18071748 (registering DOI) - 31 Mar 2025

Abstract

Achieving the Sustainable Development Goals (SDGs) is crucial for addressing global environmental challenges. SDG 13 calls for urgent climate action, while SDG 7 promotes sustainable energy. These objectives are particularly relevant to China, where transport-related CO₂ emissions continue to rise due to [...] Read more.

Achieving the Sustainable Development Goals (SDGs) is crucial for addressing global environmental challenges. SDG 13 calls for urgent climate action, while SDG 7 promotes sustainable energy. These objectives are particularly relevant to China, where transport-related CO₂ emissions continue to rise due to urbanization, industrial growth, and increasing energy demand. This study examines the impact of economic governance, population aging, human capital, financial innovation, GDP growth, and energy transition on China’s transport-related CO₂ emissions, using quarterly data from 2006Q1 to 2018Q4. The Method of Moments Quantile Regression (MMQR) is applied to analyze heterogeneous effects across different emission levels. The findings reveal that economic governance (ECOG), energy transition (ENT), and human capital (HI) significantly reduce transport CO₂ emissions (TCO_2E) by enhancing institutional effectiveness and promoting clean energy adoption. In contrast, population aging (POPAGE), financial innovation (FI), and GDP contribute to higher emissions by increasing energy consumption and private transport dependency. These insights highlight the need for stronger governance frameworks, sustainable financial policies, and increased investment in renewable energy. Policymakers should strengthen environmental regulations, expand green financing initiatives, and enhance public transport infrastructure to align with SDGs 7 and 13. By implementing these strategies, China can make significant progress toward reducing transport emissions, achieving carbon neutrality, and ensuring long-term sustainability. Full article

(This article belongs to the Section C: Energy Economics and Policy)

26 pages, 5052 KiB

Open AccessArticle

Research on the Construction Method of Inter-Provincial Spot Trading Network Model Considering Power Grid Congestion

by Hui Cui, Guodong Huang, Jingyang Zhou, Chenxu Hu, Shuyan Zhang, Shaochong Zhang and Bo Zhou

Energies 2025, 18(7), 1747; https://doi.org/10.3390/en18071747 (registering DOI) - 31 Mar 2025

Abstract

This study proposes a full-cost electricity pricing model (M3) based on power flow tracing, addressing limitations in traditional nodal pricing and postage stamp methods. M3 dynamically allocates fixed transmission costs based on actual grid utilization, improving fairness, price signal accuracy, and congestion management. [...] Read more.

This study proposes a full-cost electricity pricing model (M3) based on power flow tracing, addressing limitations in traditional nodal pricing and postage stamp methods. M3 dynamically allocates fixed transmission costs based on actual grid utilization, improving fairness, price signal accuracy, and congestion management. The model achieves fast convergence within 20 iterations across tested networks. Sensitivity analysis confirms that fuel costs and load variations significantly impact pricing, making M3 more adaptive and responsive. A regression-based forecasting model further enhances price predictability. The dual IEEE 118-bus case study validates M3’s feasibility in inter-provincial electricity markets, demonstrating its effectiveness for real-time pricing and investment planning. Full article

(This article belongs to the Section F: Electrical Engineering)

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34 pages, 2671 KiB

Open AccessArticle

Self-Diagnostic Advanced Metering Infrastructure Based on Power-Line Communication: A Study Case in Spanish Low-Voltage Distribution Networks

by Matías Ariel Kippke Salomón, José Manuel Carou Álvarez, Lucía Suárez Ramón and Pablo Arboleya

Energies 2025, 18(7), 1746; https://doi.org/10.3390/en18071746 (registering DOI) - 31 Mar 2025

Abstract

The transformation of low-voltage distribution grids toward decentralized, user-centric models has increased the need for advanced metering infrastructures capable of ensuring both visibility and control. This paper presents a self-diagnostic advanced metering solution based on power-line communication deployed in a segment of the [...] Read more.

The transformation of low-voltage distribution grids toward decentralized, user-centric models has increased the need for advanced metering infrastructures capable of ensuring both visibility and control. This paper presents a self-diagnostic advanced metering solution based on power-line communication deployed in a segment of the Spanish distribution network. The proposed infrastructure leverages the existing power network as a shared-media communication channel, reducing capital expenditures while enhancing system observability. A methodology is introduced for integrating smart metering data with topological and operational analytics to improve network monitoring and energy management. This study details the proposed metering infrastructure, highlighting its role in enhancing distribution network resilience through asynchronous energy measurements, event-driven analytics, and dynamic grid management strategies. The self-diagnostic module enables the detection of non-technical losses, identification of congested areas, and monitoring of network assets. Furthermore, this paper discusses the regulatory and technological challenges associated with scaling metering solutions, particularly in the context of increasing distributed energy resource penetration and evolving European Union regulatory frameworks. The findings demonstrate that a well-integrated advanced metering infrastructure system significantly improves distribution network efficiency, enabling proactive congestion detection and advanced load management techniques. However, this study also emphasizes the limitations of PLC in high-noise environments and proposes enhancements such as hybrid communication approaches to improve reliability and real-time performance. The insights provided contribute to the ongoing evolution of metering infrastructure technologies, offering a path toward more efficient and resource-optimized smart grids. Full article

(This article belongs to the Special Issue Approaches and Experiences of Monitoring and Control of Electrical Distribution Grids)

30 pages, 1626 KiB

Open AccessArticle

Home Biogas Production from Organic Waste: Challenges and Process Optimization of Methane Fermentation

by Jadwiga Holewa-Rataj, Mateusz Rataj, Piotr Kapusta, Joanna Brzeszcz, Marek Janiga and Anna Król

Energies 2025, 18(7), 1745; https://doi.org/10.3390/en18071745 (registering DOI) - 31 Mar 2025

Abstract

This publication presents an analysis of the possibilities for home biogas production using an original method. The assumptions for a biogas-generating system and key principles for the methane fermentation process are outlined. Research on the methane fermentation of both kitchen waste and green [...] Read more.

This publication presents an analysis of the possibilities for home biogas production using an original method. The assumptions for a biogas-generating system and key principles for the methane fermentation process are outlined. Research on the methane fermentation of both kitchen waste and green waste was conducted using a methanogenic consortium. The studies allowed for the characterization of the microorganisms comprising the consortium, and tests confirmed the feasibility of conducting methane fermentation of both types of waste at both laboratory and technical scales, as well as estimating the biogas productivity of the substrates. Based on the research conducted at both scales, the range of conditions under which the biogas production process is possible was determined, with particular reference to temperature conditions and the pH of the leachate. The tests, primarily conducted at a technical scale, allowed for the definition and implementation of optimization measures that resulted in increased process efficiency at the technical scale. Among the main optimization measures were the use of sand as a phase to maintain an anaerobic zone at the start of the process, the use of wood ash to stabilize pH, and the use of substrates and water at room temperature. Full article

(This article belongs to the Special Issue Biomass Resources to Bioenergy)

13 pages, 6774 KiB

Open AccessArticle

Predictive Modeling of Textile Heat Sinks for Enhanced Thermal Management in Space and Military Applications

by Michal Frydrysiak and Piotr Kosobudzki

Energies 2025, 18(7), 1744; https://doi.org/10.3390/en18071744 (registering DOI) - 31 Mar 2025

Abstract

This paper presents the research and numerical modeling of heat flow through a textile heat sink (THS). The aim of this research is to create a numerical model of a THS that not only simulates the thermal behavior of knitted fabrics, which are [...] Read more.

This paper presents the research and numerical modeling of heat flow through a textile heat sink (THS). The aim of this research is to create a numerical model of a THS that not only simulates the thermal behavior of knitted fabrics, which are used to construct a THS, but also serves as a predictive tool for the heat flow coming from different devices, thus increasing thermal management safety. By integrating modeling tools with textile engineering, this study contributes valuable insights to the development of effective passive cooling solutions for textronics applications, e.g., in thermal management in the military or air space sectors. THS is a support tool for multilayer insulation (MLI) blankets in space satellites, used to maintain the insulation performance of MLI to retain the extremely low temperature of satellite sensors or fuel tanks. The textile radiator made of spacer knitted 3D fabric consists of monofilament yarns covered with aluminum. THS samples were made on the HD 6/20-65 EL machine of Karl Mayer, with the calibration number E12. Numerical modeling was performed using ANSYS software. The numerical simulations of the temperature gradient presented the heat flow for source temperatures of 50 °C and 70 °C for different values of air velocity. Full article

(This article belongs to the Special Issue Advancements and Future Prospects of Heat Exchangers in Thermal and Energy Management)

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26 pages, 12771 KiB

Open AccessReview

Safety Analysis of Hydrogen-Powered Train in Different Application Scenarios: A Review

by Lei Xu, Yankun Li, Wenchao Zhang, Tiancai Ma and Xiuhui Jing

Energies 2025, 18(7), 1743; https://doi.org/10.3390/en18071743 (registering DOI) - 31 Mar 2025

Abstract

Currently, there are many gaps in the research on the safety of hydrogen-powered trains, and the hazardous points vary across different scenarios. It is necessary to conduct safety analysis for various scenarios in order to develop effective accident response strategies. Considering the implementation [...] Read more.

Currently, there are many gaps in the research on the safety of hydrogen-powered trains, and the hazardous points vary across different scenarios. It is necessary to conduct safety analysis for various scenarios in order to develop effective accident response strategies. Considering the implementation of hydrogen power in the rail transport sector, this paper reviews the development status of hydrogen-powered trains and the hydrogen leak hazard chain. Based on the literature and industry data, a thorough analysis is conducted on the challenges faced by hydrogen-powered trains in the scenario of electrified railways, tunnels, train stations, hydrogen refueling stations, and garages. Existing railway facilities are not ready to deal with accidental hydrogen leakage, and the promotion of hydrogen-powered trains needs to be cautious. Full article

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

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28 pages, 2344 KiB

Open AccessReview

Research Progress and Technical Challenges of Geothermal Energy Development from Hot Dry Rock: A Review

by Yilong Yuan, Xinli Zhang, Han Yu, Chenghao Zhong, Yu Wang, Dongguang Wen, Tianfu Xu and Fabrizio Gherardi

Energies 2025, 18(7), 1742; https://doi.org/10.3390/en18071742 (registering DOI) - 31 Mar 2025

Abstract

The reserves of hot dry rock (HDR) geothermal resources are huge. The main method used to develop HDR geothermal resources is called an enhanced geothermal system (EGS), and this generally uses hydraulic fracturing. After nearly 50 years of research and development, more and [...] Read more.

The reserves of hot dry rock (HDR) geothermal resources are huge. The main method used to develop HDR geothermal resources is called an enhanced geothermal system (EGS), and this generally uses hydraulic fracturing. After nearly 50 years of research and development, more and more countries have joined the ranks engaged in the exploration and development of HDR in the world. This paper summarizes the base technologies, key technologies, and game-changing technologies used to promote the commercialization of HDR geothermal resources. According to the present situation of the exploration, development, and utilization of HDR at home and abroad, the evaluation and site selection, efficient and low-cost drilling, and geothermal utilization of HDR geothermal resources are defined as the base technologies. Key technologies include the high-resolution exploration and characterization of HDR, efficient and complex fracture network reservoir creation, effective microseismic control, fracture network connectivity, and reservoir characterization. Game-changing technologies include downhole liquid explosion fracture creation, downhole in-situ efficient heat transfer and power generation, and the use of CO₂ and other working fluids for high-efficient power generation. Most of the base technologies already have industrial applications, but future efforts must focus on reducing costs. The majority of key technologies are still in the site demonstration and validation phase and have not yet been applied on an industrial scale. However, breakthroughs in cost reduction and application effectiveness are urgently needed for these key technologies. Game-changing technologies remain at the laboratory research stage, but any breakthroughs in this area could significantly advance the efficient development of HDR geothermal resources. In addition, we conducted a comparative analysis of the respective advantages of China and the United States in some key technologies of HDR development. On this basis, we summarized the key challenges identified throughout the discussion and highlighted the most pressing research priorities. We hope these technologies can guide new breakthroughs in HDR geothermal development in China and other countries, helping to establish a batch of HDR exploitation demonstration areas. In addition, we look forward to fostering collaboration between China and the United States through technical comparisons, jointly promoting the commercial development of HDR geothermal resources. Full article

(This article belongs to the Section H2: Geothermal)

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36 pages, 9769 KiB

Open AccessArticle

Model Development and Implementation of Techno-Economic Assessment of Hydrogen Logistics Value Chain: A Case Study of Selected Regions in the Czech Republic

by David Poul, Xuexiu Jia, Martin Pavlas and Petr Stehlík

Energies 2025, 18(7), 1741; https://doi.org/10.3390/en18071741 (registering DOI) - 31 Mar 2025

Abstract

With the rising demand for renewable hydrogen as an alternative sustainable fuel, efficient transport strategies have become essential, particularly for regional and small-scale applications. While most previous studies focus on the long-distance transport of hydrogen, little attention has been given to the application [...] Read more.

With the rising demand for renewable hydrogen as an alternative sustainable fuel, efficient transport strategies have become essential, particularly for regional and small-scale applications. While most previous studies focus on the long-distance transport of hydrogen, little attention has been given to the application in regions that are remote from major transmission infrastructure. This study evaluates the techno-economic performance of hydrogen road transport using multiple-element hydrogen gas containers and compares it with multimodal transport using rail. The comparison is performed for the southeastern region of the Czech Republic. The comprehensive techno-economic assessment incorporates detailed technical evaluations, precise fuel and energy consumption calculations, and real-world infrastructure planning to enhance accuracy. Results showed that multimodal transport of hydrogen can significantly reduce the cost for distances exceeding 90 km. The cost is calculated based on annual vehicle utilization, assuming the remaining utilization will be allocated to other tasks throughout the year. However, the cost-effectiveness of rail transportation is influenced by track capacity limits and possible delays. Additionally, this study highlights the crucial role of regional logistics hubs in optimizing transport modes, further reducing costs and improving efficiency. Full article

(This article belongs to the Special Issue Environmental Footprint of Energy Production and Storage Systems Based on Renewable Energy Sources)

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30 pages, 3755 KiB

Open AccessSystematic Review

Combining Energy Performance and Indoor Environmental Quality (IEQ) in Buildings: A Systematic Review on Common IEQ Guidelines and Energy Codes in North America

by Ishanka Perera, Kasun Hewage, Anber Rana and Rehan Sadiq

Energies 2025, 18(7), 1740; https://doi.org/10.3390/en18071740 (registering DOI) - 31 Mar 2025

Abstract

The indoor environmental quality (IEQ) in buildings is vital for health, work efficiency, productivity, and the overall sustainability of buildings. IEQ is governed by four parameters: indoor air quality and thermal, acoustic, and visual comfort. The recent pandemic has compelled people to think [...] Read more.

The indoor environmental quality (IEQ) in buildings is vital for health, work efficiency, productivity, and the overall sustainability of buildings. IEQ is governed by four parameters: indoor air quality and thermal, acoustic, and visual comfort. The recent pandemic has compelled people to think beyond energy efficiency and refocus on the health, well-being, and productivity of building occupants. Despite numerous IEQ guidelines and standards, there remains a paucity of systematic research that critically examines the relationship between IEQ and building energy efficiency. This systematic review explores the existing equilibrium and identifies gaps between IEQ standards and building energy codes. Firstly, this review examined the status of the IEQ standards and identified that most of the North American IEQ guidelines cannot achieve energy efficiency targets. Secondly, existing building energy codes were reviewed to determine how well these codes fare with IEQ requirements. It was revealed that the expensive energy certification documents are more focused on IEQ than traditional energy codes. The identified factors indicate that most building energy codes can meet only indoor air quality thresholds (a subset of IEQ), while other parameters are inadequately addressed. This review revealed 19 relationships between IEQs and energy efficiency. Building energy code/IEQ guidelines developers could consider the identified 19 relationships to develop a combined set of guidelines/standards for future building stock. An integration model between IEQ and energy efficiency is proposed as a future research direction to contribute to the better design and construction of modern buildings. The findings will facilitate the construction of healthy and sustainable buildings, and they aim to generate new residential communities that achieve an optimal health–energy–carbon nexus. Full article

(This article belongs to the Special Issue Sustainable Built Environment: Energy Efficiency Technologies, Performance Evaluation and Indoor Environment Quality)

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25 pages, 1966 KiB

Open AccessArticle

Optimizing Feedstock Selection for Sustainable Small-Scale Biogas Systems Using the Analytic Hierarchy Process

by Joshua Ngetuny, Tobias Baldauf and Wilfried Zörner

Energies 2025, 18(7), 1739; https://doi.org/10.3390/en18071739 (registering DOI) - 31 Mar 2025

Abstract

Small-scale biogas systems can play a pivotal role in sustainable energy provision, particularly in developing countries. However, their dependence on livestock manure as the only feedstock poses challenges to their adoption and long-term viability. This often leads to insufficient biogas production and plant [...] Read more.

Small-scale biogas systems can play a pivotal role in sustainable energy provision, particularly in developing countries. However, their dependence on livestock manure as the only feedstock poses challenges to their adoption and long-term viability. This often leads to insufficient biogas production and plant abandonment. This study proposes co-digestion of livestock manure with other farm residues to enhance the technical sustainability of small-scale biogas systems by ensuring adequate and consistent biogas production throughout the plant’s lifespan, minimizing the risks associated with reliance on a single feedstock. A novel feedstock selection approach is developed using the Analytic Hierarchy Process (AHP), a multicriteria decision-making method, to prioritize feedstocks based on adequacy, supply consistency, and logistical ease. AHP is chosen due to its capability to handle both quantitative and qualitative evaluation criteria. This approach is applied to the Fès-Meknès region of Morocco, which offers abundant livestock and crop residues alongside product utilization pathways. The prioritization and ranking of the potential feedstocks identified in the region reveals cattle manure as the top-ranked feedstock due to its consistent supply and ease of collection, followed by straw, valued for its storability and nutrient stability. Sheep, horse, and chicken manure ranked third, fourth, and fifth, respectively, while household food waste and fruit and vegetable residues, limited by seasonality and perishability, were ranked lower. Based on these findings, co-digestion of cattle manure and straw is proposed as a sustainable strategy for small-scale biogas plants in Fès-Meknès, addressing feedstock shortages, enhancing biogas production, and reducing plant abandonment. This approach strengthens technical sustainability and promotes the broader adoption of biogas technologies in developing countries. Full article

(This article belongs to the Special Issue Biomass Resources to Bioenergy)

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29 pages, 7936 KiB

Open AccessArticle

Dynamic Response of a 15 MW Jacket-Supported Offshore Wind Turbine Excited by Different Loadings

by Renqiang Xi, Lijie Yu, Xiaowei Meng and Wanli Yu

Energies 2025, 18(7), 1738; https://doi.org/10.3390/en18071738 (registering DOI) - 31 Mar 2025

Abstract

This study investigates the dynamic behavior of a jacket-supported offshore wind turbine (JOWT) by developing its substructure and controller tailored for the IEA 15 MW reference wind turbine. A fully coupled numerical model integrating the turbine, jacket, and pile is established to analyze [...] Read more.

This study investigates the dynamic behavior of a jacket-supported offshore wind turbine (JOWT) by developing its substructure and controller tailored for the IEA 15 MW reference wind turbine. A fully coupled numerical model integrating the turbine, jacket, and pile is established to analyze the natural frequencies and dynamic responses of the system under wind–wave–current loading and seismic excitations. Validation studies confirm that the proposed 15 MW JOWT configuration complies with international standards regarding natural frequency constraints, bearing capacity requirements, and serviceability limit state criteria. Notably, the fixed-base assumption leads to overestimations of natural frequencies by 32.4% and 13.9% in the fore-aft third- and fourth-order modes, respectively, highlighting the necessity of soil–structure interaction (SSI) modeling. During both operational and extreme wind–wave conditions, structural responses are governed by first-mode vibrations, with the pile-head axial forces constituting the primary resistance against jacket overturning moments. In contrast, seismic excitations conversely trigger significantly higher-mode activation in the support structure, where SSI effects substantially influence response magnitudes. Comparative analysis demonstrates that neglecting SSI underestimates peak seismic responses under the BCR (Bonds Corner Record of 1979 Imperial Valley Earthquake) ground motion by 29% (nacelle acceleration), 21% (yaw-bearing bending moment), 42% (yaw-bearing shear force), and 17% (tower-base bending moment). Full article

(This article belongs to the Section A3: Wind, Wave and Tidal Energy)

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12 pages, 1123 KiB

Open AccessArticle

Energy Efficiency Indicators About an Italian Representative Hollow Glass Plant

by Dario Atzori, Claudia Bassano, Simone Tiozzo, Sandra Corasaniti and Angelo Spena

Energies 2025, 18(7), 1737; https://doi.org/10.3390/en18071737 (registering DOI) - 31 Mar 2025

Abstract

In recent years, the European Union has actively advocated for decarbonising hard-to-abate industries, including the glass sector. Stakeholders in both glass manufacturing and the research community have collaborated to fulfil ambitious CO₂ emission reduction objectives mandated by Brussels, in several ways. The [...] Read more.

In recent years, the European Union has actively advocated for decarbonising hard-to-abate industries, including the glass sector. Stakeholders in both glass manufacturing and the research community have collaborated to fulfil ambitious CO₂ emission reduction objectives mandated by Brussels, in several ways. The initial strategic action to be undertaken involves reducing energy consumption through energy efficiency interventions; to achieve this goal, it is essential to be aware of own consumption indicators by comparing them with appropriate performance ones. There are not many updated references connected to real-world cases, nor are indicators specifically tied to individual phases of the production process available. After a brief presentation of the container glass sector, which is the most important subsector, in terms of production capacity in Italy and the EU and its production process, the manuscript describes a real and representative plant of the sector, which has made its data available anonymously. In this way, energy performance indices representative of a typical production of the sector have been defined: they are updated and more detailed than the ones available in the literature. This representation therefore constitutes a case study that is representative of the most common plant configuration in the hollow glass sector in the EU. Full article

(This article belongs to the Special Issue Energy, Environment, and Social Effects Obtainable through the Renewable Energy Community Institution)

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15 pages, 5960 KiB

Open AccessArticle

Research and Application of Drilling Fluid Cooling System for Dry Hot Rock

by Kuan Li, Bing Li, Shanshan Shi, Zhenyu Wu and Hengchun Zhang

Energies 2025, 18(7), 1736; https://doi.org/10.3390/en18071736 - 31 Mar 2025

Abstract

The drilling fluid cooling system is a key technology for reducing wellbore temperatures, improving the working environment of downhole equipment, and ensuring safe and efficient drilling in high-temperature wells. Based on the existing drilling fluid cooling system, this article designs and develops a [...] Read more.

The drilling fluid cooling system is a key technology for reducing wellbore temperatures, improving the working environment of downhole equipment, and ensuring safe and efficient drilling in high-temperature wells. Based on the existing drilling fluid cooling system, this article designs and develops a closed drilling fluid cooling system according to the working environment and cooling requirements of the GH-02 dry hot rock trial production well in the Gonghe Basin, Qinghai Province. The system mainly includes a cascade cooling module, a convective heat exchange module, and a monitoring and control module. Based on the formation conditions and drilling design of the GH-02 well, a transient temperature prediction model for wellbore circulation is established to provide a basis for the design of the cooling system. Under the conditions of a drilling fluid displacement of 30 L/s and a bottomhole circulation temperature not exceeding 105 °C, the maximum allowable inlet temperature of the drilling fluid is 55.6 °C, and the outlet temperature of the drilling fluid is 69.2 °C. The heat exchange of the drilling fluid circulation is not less than 1785 kW. Considering the heat transfer efficiency and reserve coefficient, the heat transfer area of the spiral plate heat exchanger calculated using the average temperature difference method is not less than 75 m². By applying this drilling fluid cooling system in the 3055 m~4013 m section of well GH-02, the inlet temperature is controlled at 45 °C~55 °C, and the measured bottomhole circulation temperature remains below 105 °C. After adopting the drilling fluid cooling system, the performance of the drilling fluid is stable during the drilling process, downhole tools such as the drill bits, screws, and MWD work normally, and the failure rate of the mud pump and logging instruments is significantly reduced. The drilling fluid cooling system effectively maintains the safe and efficient operation of the drilling system, which has been promoted and applied in shale oil wells in Dagang Oilfield. Full article

(This article belongs to the Special Issue Advances in Geothermal Energy from Synergies with Oil and Gas Industries)

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