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Variable-Length Pendulum-Based Mechatronic Systems for Energy Harvesting: A Review of Dynamic Models
Analysis of the Temperature Reached by the Traction Battery of an Electric Vehicle during the Drying Phase in the Paint Booth
Transition to Low-Carbon Vehicle Market: Characterization, System Dynamics Modeling, and Forecasting
The Role of EU Transport Market Liberalization in Shaping Directions of Rail Energy Consumption Rationalization in Relation to the Export of Goods: The Case of Poland
A SWOT Analysis of the Green Hydrogen Market

Journal Description

Energies

Energies is a peer-reviewed, open access journal of related scientific research, technology development, engineering policy, and management studies related to the general field of energy, from technologies of energy supply, conversion, dispatch, and final use to the physical and chemical processes behind such technologies. Energies is published semimonthly online by MDPI. The European Biomass Industry Association (EUBIA), Association of European Renewable Energy Research Centres (EUREC), Institute of Energy and Fuel Processing Technology (ITPE), International Society for Porous Media (InterPore), CYTED and others are affiliated with Energies and their members receive a discount on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Ei Compendex, RePEc, Inspec, CAPlus / SciFinder, and other databases.
Journal Rank: CiteScore - Q1 (Control and Optimization)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 17.5 days after submission; acceptance to publication is undertaken in 3.4 days (median values for papers published in this journal in the first half of 2024).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Sections: published in 41 topical sections.
Testimonials: See what our editors and authors say about Energies.
Companion journals for Energies include: Gases, Nanoenergy Advances, Solar, Wind and Energy Storage and Applications

Impact Factor: 3.0 (2023); 5-Year Impact Factor: 3.0 (2023)

Imprint Information Journal Flyer Open Access ISSN: 1996-1073

Latest Articles

23 pages, 6135 KiB

Open AccessArticle

Assessing Stability in Renewable Microgrid Using a Novel-Optimized Controller for PVBattery Based Micro Grid with Opal-RT-Based Real-Time Validation

by Anshuman Satpathy, Rahimi Bin Baharom, Naeem M. S. Hannon, Niranjan Nayak and Snehamoy Dhar

Energies 2024, 17(20), 5024; https://doi.org/10.3390/en17205024 (registering DOI) - 10 Oct 2024

This paper focuses on the distributed generation (DG) controller of a PV-based microgrid. An independent DG controller (IDGC) is designed for PV applications to improve Maximum-Power Point Tracking (MPPT). The Extreme-Learning Machine (ELM)-based MPPT method exactly estimates the controller’s reference input, such as [...] Read more.

This paper focuses on the distributed generation (DG) controller of a PV-based microgrid. An independent DG controller (IDGC) is designed for PV applications to improve Maximum-Power Point Tracking (MPPT). The Extreme-Learning Machine (ELM)-based MPPT method exactly estimates the controller’s reference input, such as the voltage and current at the MPP. Feedback controls employ linear PI schemes or nonlinear, intricate techniques. Here, the converter controller is an IDGC that is improved by directly measuring the converter duty cycle and PWM index in a single DG PV-based MG. It introduces a fast-learning Extreme-Learning Machine (ELM) using the Moore–Penrose pseudo-inverse technique and online sequential ridge methods for robust control reference (CR) estimation. This approach ensures the stability of the microgrid during PV uncertainties and various operational conditions. The internal DG control approach improves the stability of the microgrid during a three-phase fault at the load bus, partial shading, irradiance changes, islanding operations, and load changes. The model is designed and simulated on the MATLAB/SIMULINK platform, and some of the results are validated on a hardware-in-the-loop (HIL) platform. Full article

(This article belongs to the Topic Advanced Energy Harvesting Technology)

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15 pages, 2029 KiB

Open AccessArticle

An Open-Source Tool for Composite Power System Reliability Assessment in Julia™

by Josif Figueroa, Kush Bubbar and Greg Young-Morris

Energies 2024, 17(20), 5023; https://doi.org/10.3390/en17205023 (registering DOI) - 10 Oct 2024

This paper introduces an open-source tool capable of performing the Composite System Reliability evaluation developed in the high-level, dynamic Julia™ programming language. Employing Monte Carlo Simulation and parallel computing, the tool evaluates probabilistic adequacy indices for combined generation and transmission systems, focusing on [...] Read more.

This paper introduces an open-source tool capable of performing the Composite System Reliability evaluation developed in the high-level, dynamic Julia™ programming language. Employing Monte Carlo Simulation and parallel computing, the tool evaluates probabilistic adequacy indices for combined generation and transmission systems, focusing on both individual delivery points and the broader system. Proficiency in Optimal Power Flow problem formulations is demonstrated through two distinct methods: DC and linearized AC, enabling comprehensive resource and transmission adequacy analysis with high-performance solvers. Addressing replicability and the insufficiency of available software, the tool supports diverse analyses on a unified platform. The paper discusses the tool’s design and validation, particularly focusing on the two optimal power flow problem formulations. These insights significantly contribute to understanding transmission system performance and have implications for power system planning. Full article

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

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26 pages, 3842 KiB

Open AccessArticle

Multi-Objective Optimization Operation of Multi-Agent Active Distribution Network Based on Analytical Target Cascading Method

by Yiran Zhao, Yong Xue, Ruixin Zhang, Jiahao Yin, Yang Yang and Yanbo Chen

Energies 2024, 17(20), 5022; https://doi.org/10.3390/en17205022 (registering DOI) - 10 Oct 2024

In the context of the green energy transition, the rapid expansion of flexible resources such as distributed renewable energy, electric vehicles (EVs), and energy storage has significantly impacted the operation of distribution networks. This paper proposes a multi-objective optimization approach for active distribution [...] Read more.

In the context of the green energy transition, the rapid expansion of flexible resources such as distributed renewable energy, electric vehicles (EVs), and energy storage has significantly impacted the operation of distribution networks. This paper proposes a multi-objective optimization approach for active distribution networks (ADNs) based on analytical target cascading (ATC). Firstly, a dynamic optimal power flow (DOPF) calculation method is developed using second-order conic relaxation (SOCR) to address power flow and voltage issues in the distribution network, incorporating active management (AM) elements. Secondly, this study focuses on aggregating the power of flexible resources within station areas connected to distribution network nodes and incorporating these resources into demand response (DR) programs. Finally, a two-layer model for collaborative multi-objective scheduling between station areas and the active distribution network is implemented using the ATC method. Case studies demonstrate the model’s effectiveness and validity, showing its potential for enhancing the operation of distribution networks amidst the increasing integration of flexible resources. Full article

(This article belongs to the Special Issue Planning, Operation, and Control of New Power Systems)

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19 pages, 775 KiB

Open AccessReview

Asymmetric Operation of Power Networks, State of the Art, Challenges, and Opportunities

by Ansar Berdygozhin and David Campos-Gaona

Energies 2024, 17(20), 5021; https://doi.org/10.3390/en17205021 (registering DOI) - 10 Oct 2024

The asymmetric operation is a method that allows High and Extra-High Voltage (HV, EHV) power lines to function with one or two phases open. With the increasing share of Renewable Energy Sources (RES) in National Power Systems (NPS), they are becoming more volatile [...] Read more.

The asymmetric operation is a method that allows High and Extra-High Voltage (HV, EHV) power lines to function with one or two phases open. With the increasing share of Renewable Energy Sources (RES) in National Power Systems (NPS), they are becoming more volatile and less reliable due to decreasing inertia and other issues related to the integration and exploitation of the Inverter-Based Resources (IBR) (decreasing short-circuit ratio, different types of interactions, etc.). On the other hand, phase-to-ground faults are a common cause of tripping off power lines which affects the overall reliability of the power system. Thus, for power systems experiencing a decreasing trend in reliability and robustness, the asymmetrical operation of the power lines may enhance them. In this way, this article reviews the state of the art and new developments in the academic landscape regarding asymmetrical operation. The review is not, however, limited to HV and EHV systems, so it examines cases of asymmetric operation in Low and Medium Voltages (LV, MV) as well. The challenges and opportunities that this unique mode of operation imposes on power networks are also presented, providing a fresh reference for researchers looking to enter this topic. Full article

(This article belongs to the Special Issue Energy, Electrical and Power Engineering 2024)

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23 pages, 2275 KiB

Open AccessArticle

A Post-Disaster Fault Recovery Model for Distribution Networks Considering Road Damage and Dual Repair Teams

by Wei Liu, Qingshan Xu, Minglei Qin and Yongbiao Yang

Energies 2024, 17(20), 5020; https://doi.org/10.3390/en17205020 (registering DOI) - 10 Oct 2024

Extreme weather, such as rainstorms, often triggers faults in the distribution network, and power outages occur. Some serious faults cannot be repaired by one team alone and may require equipment replacement or engineering construction crews to work together. Rainstorms can also lead to [...] Read more.

Extreme weather, such as rainstorms, often triggers faults in the distribution network, and power outages occur. Some serious faults cannot be repaired by one team alone and may require equipment replacement or engineering construction crews to work together. Rainstorms can also lead to road damage or severe waterlogging, making some road sections impassable. Based on this, this paper first establishes a road network model to describe the dynamic changes in access performance and road damage. It provides the shortest time-consuming route suggestions for the traffic access of mobile class resources in the post-disaster recovery task of power distribution networks. Then, the model proposes a joint repair model with general repair crew (GRC) and senior repair crew (SRC) collaboration. Different types of faults match different functions of repair crews (RCs). Finally, the proposed scheme is simulated and analyzed in a road network and power grid extreme post-disaster recovery model, including a mobile energy storage system (MESS) and distributed power sources. The simulation finds that considering road damage and severe failures produces a significant difference in the progress and load loss of the recovery task. The model proposed in this paper is more suitable for the actual scenario requirements, and the simulation results and loss assessment obtained are more accurate and informative. Full article

(This article belongs to the Topic Intelligent, Flexible, and Effective Operation of Smart Grids with Novel Energy Technologies and Equipment)

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15 pages, 3041 KiB

Open AccessArticle

Research on Electric Hydrogen Hybrid Storage Operation Strategy for Wind Power Fluctuation Suppression

by Dongsen Li, Kang Qian, Ciwei Gao, Yiyue Xu, Qiang Xing and Zhangfan Wang

Energies 2024, 17(20), 5019; https://doi.org/10.3390/en17205019 (registering DOI) - 10 Oct 2024

Due to real-time fluctuations in wind farm output, large-scale renewable energy (RE) generation poses significant challenges to power system stability. To address this issue, this paper proposes a deep reinforcement learning (DRL)-based electric hydrogen hybrid storage (EHHS) strategy to mitigate wind power fluctuations [...] Read more.

Due to real-time fluctuations in wind farm output, large-scale renewable energy (RE) generation poses significant challenges to power system stability. To address this issue, this paper proposes a deep reinforcement learning (DRL)-based electric hydrogen hybrid storage (EHHS) strategy to mitigate wind power fluctuations (WPFs). First, a wavelet packet power decomposition algorithm based on variable frequency entropy improvement is proposed. This algorithm characterizes the energy characteristics of the original wind power in different frequency bands. Second, to minimize WPF and the comprehensive operating cost of EHHS, an optimization model for suppressing wind power in the integrated power and hydrogen system (IPHS) is constructed. Next, considering the real-time and stochastic characteristics of wind power, the wind power smoothing model is transformed into a Markov decision process. A modified proximal policy optimization (MPPO) based on wind power deviation is proposed for training and solving. Based on the DRL agent’s real-time perception of wind power energy characteristics and the IPHS operation status, a WPF smoothing strategy is formulated. Finally, a numerical analysis based on a specific wind farm is conducted. The simulation results based on MATLAB R2021b show that the proposed strategy effectively suppresses WPF and demonstrates excellent convergence stability. The comprehensive performance of the MPPO is improved by 21.25% compared with the proximal policy optimization (PPO) and 42.52% compared with MPPO. Full article

(This article belongs to the Special Issue Operation and Control of Distributed Power Resources Under Market Environment)

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21 pages, 6692 KiB

Open AccessArticle

Optimizing S Chemical Looping Combustion with Cu-Fe Combined Oxygen Carriers: Performance and Mechanistic Insights

by Lihuai Peng and Min Zheng

Energies 2024, 17(20), 5018; https://doi.org/10.3390/en17205018 (registering DOI) - 10 Oct 2024

This study focuses on the S-to-H₂SO₄ industry by investigating the chemical looping combustion (CLC) process utilizing Fe-based and Cu-based oxygen carriers (OCs), which are widely applied in CLC technology. The primary objective is to conduct combined CLC reactions of these [...] Read more.

This study focuses on the S-to-H₂SO₄ industry by investigating the chemical looping combustion (CLC) process utilizing Fe-based and Cu-based oxygen carriers (OCs), which are widely applied in CLC technology. The primary objective is to conduct combined CLC reactions of these two metal carriers in a three-zone temperature tube furnace, aiming to achieve a higher SO₂ yield than what is attainable by reacting a single metal carrier with S. The investigation reveals promising industrial applications, offering potential benefits in terms of reducing equipment costs, enhancing energy efficiency, and lowering the emissions of the H₂SO₄ production industry. Through a series of experiments, the study examines the effects of reaction temperature and material molar ratios on SO₂ generation. The solid reaction products were characterized using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS). The experimental results indicate that the combined Cu-based and Fe-based OCs exhibit a higher SO₂ yield during the reduction stage compared to using either Fe-based or Cu-based OCs independently. Under optimal conditions, with a carrier gas flow rate of 300 mL/min, an Fe₂O₃/S molar ratio of 6:1 in the second temperature zone, and a reaction temperature of 900 °C, the total SO₂ yield in the third temperature zone reached approximately 85%. This was achieved at a reaction temperature of 850 °C, with an Fe₂O₃/S molar ratio of 6:1 in the first half of the zone and a CuO/S molar ratio of 12:1 in the second half of the zone. SEM-EDS analysis further revealed that the combined OCs showed no significant signs of agglomeration or sintering after 10 cycles of the reaction. However, Cu-based carrier particles increased in size by 50%, while Fe-based carrier particles remained relatively stable. Additionally, the low mass-to-atom ratio of S on the surface of OCs after the cyclic reaction suggests that the reduced-state OCs can be fully oxidized and regenerated following the release of SO₂ during oxidation. Full article

(This article belongs to the Section I3: Energy Chemistry)

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24 pages, 4416 KiB

Open AccessArticle

Cybersecurity Certification Requirements for Distributed Energy Resources: A Survey of SunSpec Alliance Standards

by Sean Tsikteris, Odyssefs Diamantopoulos Pantaleon and Eirini Eleni Tsiropoulou

Energies 2024, 17(19), 5017; https://doi.org/10.3390/en17195017 - 9 Oct 2024

This survey paper explores the cybersecurity certification requirements defined by the SunSpec Alliance for Distributed Energy Resource (DER) devices, focusing on aspects such as software updates, device communications, authentication mechanisms, device security, logging, and test procedures. The SunSpec cybersecurity standards mandate support for [...] Read more.

This survey paper explores the cybersecurity certification requirements defined by the SunSpec Alliance for Distributed Energy Resource (DER) devices, focusing on aspects such as software updates, device communications, authentication mechanisms, device security, logging, and test procedures. The SunSpec cybersecurity standards mandate support for remote and automated software updates, secure communication protocols, stringent authentication practices, and robust logging mechanisms to ensure operational integrity. Furthermore, the paper discusses the implementation of the SAE J3072 standard using the IEEE 2030.5 protocol, emphasizing the secure interactions between electric vehicle supply equipment (EVSE) and plug-in electric vehicles (PEVs) for functionalities like vehicle-to-grid (V2G) capabilities. This research also examines the SunSpec Modbus standard, which enhances the interoperability among DER system components, facilitating compliance with grid interconnection standards. This paper also analyzes the existing SunSpec Device Information Models, which standardize data exchange formats for DER systems across communication interfaces. Finally, this paper concludes with a detailed discussion of the energy storage cybersecurity specification and the blockchain cybersecurity requirements as proposed by SunSpec Alliance. Full article

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19 pages, 4532 KiB

Open AccessArticle

Modular Microgrid Technology with a Single Development Environment Per Life Cycle

by Teodora Mîndra, Oana Chenaru, Radu Dobrescu and Lucian Toma

Energies 2024, 17(19), 5016; https://doi.org/10.3390/en17195016 - 9 Oct 2024

The life cycle of a microgrid covers all the stages from idea to implementation, through exploitation until the end of its life, with a lifespan of around 25 years. Covering them usually requires several software tools, which can make the integration of results [...] Read more.

The life cycle of a microgrid covers all the stages from idea to implementation, through exploitation until the end of its life, with a lifespan of around 25 years. Covering them usually requires several software tools, which can make the integration of results from different stages difficult and may imply costs being hard to estimate from the beginning of a project. This paper proposes a unified platform composed of four modules developed in MATLAB 2022b, designed to assist all the processes a microgrid passes through during its lifetime. This entire platform can be used by a user with low IT knowledge, because it is completed with fill-in-the-blank alone, as a major advantage. The authors detail the architecture, functions and development of the platform, either by highlighting the novel integration of existing MATLAB tools or by developing new ones and designing new user interfaces linked with scripts based on its complex mathematical libraries. By consolidating processes into a single platform, the proposed solution enhances integration, reduces complexity and provides better cost predictability throughout the project’s duration. A proof-of-concept for this platform was presented by applying the life-cycle assessment process on a real-case study, a microgrid consisting of a photovoltaic plant, and an office building as the consumer and energy storage units. This platform has also been developed by involving students within summer internships, as a process strengthening the cooperation between industry and academia. Being an open-source application, the platform will be used within the educational process, where the students will have the possibility to add functionalities, improve the graphical representation, create new reports, etc. Full article

(This article belongs to the Special Issue Planning and Operation of Distributed Energy Resources in Smart Grids II)

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18 pages, 3643 KiB

Open AccessArticle

MMD-TSC: An Adaptive Multi-Objective Traffic Signal Control for Energy Saving with Traffic Efficiency

by Yuqi Zhang, Yingying Zhou, Beilei Wang and Jie Song

Energies 2024, 17(19), 5015; https://doi.org/10.3390/en17195015 - 9 Oct 2024

Reducing traffic energy consumption is crucial for smart cities, and vehicle carbon emissions are a key energy indicator. Traffic signal control (TSC) is a useful method because it can affect the energy consumption of vehicles on the road by controlling the stop-and-go of [...] Read more.

Reducing traffic energy consumption is crucial for smart cities, and vehicle carbon emissions are a key energy indicator. Traffic signal control (TSC) is a useful method because it can affect the energy consumption of vehicles on the road by controlling the stop-and-go of vehicles at traffic intersections. However, setting traffic signals to reduce energy consumption will affect traffic efficiency and this is not in line with traffic management objectives. Current studies adopt multi-objective optimization methods with high traffic efficiency and low carbon emissions to solve this problem. However, most methods use static weights, which cannot adapt to complex and dynamic traffic states, resulting in non-optimal performance. Current energy indicators for urban transportation often fail to consider passenger fairness. This fairness is significant because the purpose of urban transportation is to serve people’s mobility needs not vehicles. Therefore, this paper proposes Multi-objective Adaptive Meta-DQN TSC (MMD-TSC), which introduces a dynamic weight adaptation mechanism to simultaneously optimize traffic efficiency and energy saving, and incorporates the per capita carbon emissions as the energy indicator. Firstly, this paper integrates traffic state data such as vehicle positions, velocities, vehicle types, and the number of passengers and incorporates fairness into the energy indicators, using per capita carbon emissions as the target for reducing energy consumption. Then, it proposes MMD-TSC with dynamic weights between energy consumption and traffic efficiency as reward functions. The MMD-TSC model includes two agents, the TSC agent and the weight agent, which are responsible for traffic signal adjustment and weight calculation, respectively. The weights are calculated by a function of traffic states. Finally, the paper describes the design of the MMD-TSC model learning algorithm and uses a SUMO (Simulation of Urban Mobility) v.1.20.0 for traffic simulation. The results show that in non-highly congested traffic states, the MMD-TSC model has higher traffic efficiency and lower energy consumption compared to static multi-objective TSC models and single-objective TSC models, and can adaptively achieve traffic management objectives. Compared with using vehicle average carbon emissions as the energy consumption indicator, using per capita carbon emissions achieves Pareto improvements in traffic efficiency and energy consumption indicators. The energy utilization efficiency of the MMD-TSC model is improved by 35% compared to the fixed-time TSC. Full article

(This article belongs to the Special Issue Hybrid Intelligent Modeling Technology and Optimization Strategy for Industrial Energy Consumption Processes)

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16 pages, 1278 KiB

Open AccessArticle

Evaluation of the Energy Management System in Water and Wastewater Utilities in the Context of Sustainable Development—A Case Study

by Joanna Machnik-Slomka, Elżbieta Pawlowska, Iwona Klosok-Bazan and Miroslava Goňo

Energies 2024, 17(19), 5014; https://doi.org/10.3390/en17195014 - 9 Oct 2024

Energy management in enterprises is an important issue in the context of improving energy efficiency, energy use, and energy consumption. This is consistent with the Sustainable Development Goals. The purpose of this study was to evaluate the energy management system of water and [...] Read more.

Energy management in enterprises is an important issue in the context of improving energy efficiency, energy use, and energy consumption. This is consistent with the Sustainable Development Goals. The purpose of this study was to evaluate the energy management system of water and wastewater utility in the context of sustainable development based on the opinions of managers and employees. The results indicate the involvement of the surveyed enterprise in energy management system development activity. This demonstrates the orientation of the surveyed enterprise to support activities to improve energy performance in line with the implementation of sustainable development. The added value is that the developed research tool can be used in studies of other enterprises to assess the level of energy management. Full article

(This article belongs to the Topic Energy Management and Sustainable Development from Economic, Social and Environmental Aspects)

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19 pages, 4781 KiB

Open AccessArticle

The Impact of Ambient Weather Conditions and Energy Usage Patterns on the Performance of a Domestic Off-Grid Photovoltaic System

by Iviwe Mcingani, Edson L. Meyer and Ochuko K. Overen

Energies 2024, 17(19), 5013; https://doi.org/10.3390/en17195013 - 9 Oct 2024

Solar photovoltaic (PV) systems are growing rapidly as a renewable energy source. Evaluating the performance of a PV system based on local weather conditions is crucial for its adoption and deployment. However, the current IEC 61724 standard, used for assessing PV system performance, [...] Read more.

Solar photovoltaic (PV) systems are growing rapidly as a renewable energy source. Evaluating the performance of a PV system based on local weather conditions is crucial for its adoption and deployment. However, the current IEC 61724 standard, used for assessing PV system performance, is limited to grid-connected systems. This standard may not accurately reflect the performance of off-grid PV systems. This study aims to evaluate how ambient weather conditions and energy usage patterns affect the performance of an off-grid PV system. This study uses a 3.8 kWp building-integrated photovoltaic (BIPV) system located at SolarWatt Park, University of Fort Hare, Alice, as a case study. Meteorological and electrical data from August and November are analyzed to assess the winter and summer performance of the BIPV system using the IEC 61724 standard. The BIPV system generated 376.29 kWh in winter and 366.38 kWh in summer, with a total energy consumption of 209.50 kWh in winter and 236.65 kWh in summer. Solar irradiation during winter was 130.18 kWh/m², while it was 210.24 kWh/m² during summer. The average daily performance ratio (PR) was 44.01% in winter and 28.94% in summer. The observed decrease in PR during the summer month was attributed to the higher levels of solar irradiance experienced during this time, which outweighs the increased AC energy output. The low-performance ratio does not indicate technical issues but rather a mismatch between the load demand and PV generation. The results of this study highlight the need for a separate method to assess the performance of off-grid PV systems. Full article

(This article belongs to the Special Issue Simulation Modelling and Analysis of a Renewable Energy System, Volume II)

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12 pages, 2984 KiB

Open AccessArticle

Influence of Reaction Conditions on the Yield of Supercritical Multicomponent Thermal Fluids

by Wei Zhang, Zhilin Qi, Jie Tian, Fang Xu, Deyu Kong, Mingda Dong, Shenyao Yang and Wende Yan

Energies 2024, 17(19), 5012; https://doi.org/10.3390/en17195012 - 9 Oct 2024

Supercritical multicomponent thermal fluid (scMCTF) is a novel medium with great potential for heavy oil thermal recovery. The production rate of scMCTF will affect the injection efficiency of thermal fluid, and then affect the development effect of thermal recovery. However, at present, there [...] Read more.

Supercritical multicomponent thermal fluid (scMCTF) is a novel medium with great potential for heavy oil thermal recovery. The production rate of scMCTF will affect the injection efficiency of thermal fluid, and then affect the development effect of thermal recovery. However, at present, there are few reports on the production rate of each component of scMCTF, and their understanding is not clear. According to the existing production rate data of supercritical water (scH₂O) gasification products, based on the generation mechanism of scMCTF, the production rate of thermal fluid generation products under different generation conditions was calculated, and its influencing factors were identified. The results show the following: (1) The factors affecting the production rate of scMCTF generation products can be divided into three categories: reaction raw material factors, reaction condition factors, and catalytic factors. (2) The hydrocarbon number of raw material, reaction temperature, reaction time, and catalyst concentration were positively correlated with the production rate of the product. (3) The concentration of the reaction raw material is negatively correlated with the production rate of the product. The higher the concentration of the raw material is, the lower the concentration of H₂O is, and the steam reforming reaction is inhibited, which leads to the decrease in the production rate. (4) The effect of reaction pressure and catalyst load on the product is not significant. (5) The reaction product production rate increased first and then decreased with the ratio of H₂O to oil in the raw material emulsion and the ratio of preheated H₂O to raw material discharge. (6) The effect of metal salt catalysts is relatively stable, and the catalytic effect of simple metal catalysts is significantly different under the action of different types of accelerators, so it is necessary to study the degree of synergization of different accelerators on the catalytic effect. The results can lay a foundation for the subsequent experimental and theoretical research design. Full article

(This article belongs to the Special Issue New Advances in Oil, Gas and Geothermal Reservoirs: 2nd Edition)

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16 pages, 3505 KiB

Open AccessArticle

LCCO₂ Assessment and Fertilizer Production from Absorbed-CO₂ Solid Matter in a Small-Scale DACCU Plant

by Tianjiao Cheng, Takeji Hirota, Hiroshi Onoda and Andante Hadi Pandyaswargo

Energies 2024, 17(19), 5011; https://doi.org/10.3390/en17195011 - 9 Oct 2024

This study investigates a novel method of utilizing Direct Air Capture (DAC) technology for fertilizer production. Unlike traditional Direct Air Carbon Capture and Utilization (DACCU) technologies, Direct Air Carbon Capture for Fertilizers (FDAC) has the potential to produce fertilizers directly. This study aims [...] Read more.

This study investigates a novel method of utilizing Direct Air Capture (DAC) technology for fertilizer production. Unlike traditional Direct Air Carbon Capture and Utilization (DACCU) technologies, Direct Air Carbon Capture for Fertilizers (FDAC) has the potential to produce fertilizers directly. This study aims to assess the feasibility of FDAC-based fertilizer production by examining the current state of traditional DAC technologies, evaluating the CO₂ fixation potential of FDAC, and analyzing the decarbonization effect of producing fertilizers using FDAC. Our evaluation results indicate that CO₂ emissions from producing 1 ton of conventional chemical fertilizer, FDAC fertilizer (current status), FDAC fertilizer with ingredient adjustment (sodium hydroxide), and FDAC fertilizer with ingredient adjustment (magnesium hydroxide) are 1.69, 1.12, 1.04, and 1.06 tons of CO₂, respectively. The FDAC fertilizer (current status) emits 0.57 tons of CO₂ per ton less than commercial fertilizers. FDAC fertilizers also have the potential to reduce CO₂ emissions further when the fertilizer composition is adjusted, offering a promising solution for lowering the environmental impact of fertilizer production. Significant CO₂ reduction can be expected by replacing conventional low-intensity chemical fertilizers with FDAC-produced fertilizers. Full article

(This article belongs to the Special Issue Carbon Capture, Storage and Utilization Technologies: Advances and Challenges)

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11 pages, 2294 KiB

Open AccessArticle

CO₂ Conversion by Oxygen-Enriched Gasification of Wood Chips

by Clemens Schmittmann and Peter Quicker

Energies 2024, 17(19), 5010; https://doi.org/10.3390/en17195010 - 9 Oct 2024

With increasing efforts to lower CO₂ emissions globally, the demand for carbon-based resources in industries remains on a high level, leading to new technologies being able to provide those essential carbon sources. To the best of our knowledge, we were able to [...] Read more.

With increasing efforts to lower CO₂ emissions globally, the demand for carbon-based resources in industries remains on a high level, leading to new technologies being able to provide those essential carbon sources. To the best of our knowledge, we were able to show for the first time the adaption of a readily available gasifier for the gasification of wood chips using only O₂ (18.4–23.1 Vol.-%) and CO₂ as gasification agents, creating a nitrogen-free product gas. It was found that the setup used was able to convert up to 27.2% of the CO₂ from the gasification agent to CO, creating a promising route for the production of renewable carbon sources for future carbon-based applications. Furthermore, no decrease in gasification performance was observed as the cold gas efficiency was at 83.5–95.5% with only minor formation of tar. Full article

(This article belongs to the Special Issue Advanced Bioenergy, Biomass and Waste Conversion Technologies)

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19 pages, 9356 KiB

Open AccessArticle

Scaling Law of Flow and Heat Transfer Characteristics in Turbulent Radiative Rayleigh-Bénard Convection of Optically Thick Media

by Jiajun Song, Panxin Li, Lu Chen, Yuhang Zhao, Fengshi Tian and Benwen Li

Energies 2024, 17(19), 5009; https://doi.org/10.3390/en17195009 - 8 Oct 2024

Radiative natural convection is of vital importance in the process of energy storage, power generation, and thermal storage technology. As the attenuation coefficients of many heat transfer media in these fields are high enough to be considered as optically thick media, like nanofluids [...] Read more.

Radiative natural convection is of vital importance in the process of energy storage, power generation, and thermal storage technology. As the attenuation coefficients of many heat transfer media in these fields are high enough to be considered as optically thick media, like nanofluids or molten salts in concentrated solar power or phase change thermal storage, Rosseland approximation is commonly used. In this paper, we delve into the impact of thermal radiation on the Rayleigh-Bénard (RB) convection. Theoretical analysis has been conducted by modifying the Grossmann-Lohse (GL) model. Based on turbulent dissipation theory, the corresponding scaling laws in four main regimes are proposed. Direct numerical simulation (DNS) was also performed, revealing that radiation exerts a notable influence on both flow and heat transfer, particularly on the formation of large-scale circulation. By comparing with DNS results, it is found that due to the presence of radiation, the modified Nu scaling law in small Pr range of the GL model is more suitable for predicting the transport characteristics of optical thick media with large Pr. The maximum deviation between the results of DNS and prediction model is about 10%, suggesting the summarized scaling law can effectively predict the Nu of radiative RB convection. Full article

(This article belongs to the Special Issue Advanced Technology for Solar Thermal Cooling, Heating, and Energy Storage)

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27 pages, 5679 KiB

Open AccessArticle

Analysis of Optimal HVDC Back-to-Back Placement Based on Composite System Reliability

by Nanang Hariyanto, Niko B. Simamora, Kevin M. Banjar-Nahor and Hendry Timotiyas Paradongan

Energies 2024, 17(19), 5008; https://doi.org/10.3390/en17195008 - 8 Oct 2024

HVDC is a promising interconnection solution for connecting asynchronous systems and ensuring power control. In Indonesia, a remote industrial system in Sumatra is experiencing load growth and has the option to draw power from the Sumatra system. However, due to frequency differences, the [...] Read more.

HVDC is a promising interconnection solution for connecting asynchronous systems and ensuring power control. In Indonesia, a remote industrial system in Sumatra is experiencing load growth and has the option to draw power from the Sumatra system. However, due to frequency differences, the use of HVDC is crucial. The Generation Expansion Planning has proposed six converters but not their interconnection points. This study will determine the most reliable interconnection locations. The chosen converters are modular multilevel converters (MMCs) with high modularity. The converter reliability modeling considers voltage levels, the number of modules, and redundancy strategies. This modeling is then implemented at the power system level to obtain the best placement at the available high-voltage (HV) substation options. Determining the best placement is based on the optimal reliability index. The optimal placement also includes the option to convert from HV to medium-voltage (MV) interconnection. MV interconnection offers higher flexibility but tends to be more expensive. The availability for HV converters is 99.69%, while for MV converters, it is slightly higher, at 99.81%. Additionally, converting from HV to MV reduces the SAIFI (system average interruption frequency index) from 0.2668 to 0.2284 occurrences per year, lowering the interruption cost from 7.804 million USD to 5.737 million USD per year. The sensitivity of interruption, investment, and maintenance costs shows that converting at least one HV converter to MV remains economical. In this case study, the optimal converter placement includes Area VI–2, recommended for conversion from HV to a more distributed MV configuration, improving reliability and economic efficiency. Full article

(This article belongs to the Special Issue The Planning, Operation and Control of Renewable Energy Power Grid)

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33 pages, 3482 KiB

Open AccessReview

Literature Review on Thermodynamic and Kinetic Limitations of Thermal Decomposition of Methane

by Andrzej Mianowski, Mateusz Szul, Tomasz Radko, Aleksander Sobolewski and Tomasz Iluk

Energies 2024, 17(19), 5007; https://doi.org/10.3390/en17195007 - 8 Oct 2024

The state of the art in methane pyrolysis does not yet provide a definitive answer as to whether the concept of an elementary reaction is universally applicable to the apparently simple process of methane dissociation. Similarly, the literature currently lacks a comprehensive and [...] Read more.

The state of the art in methane pyrolysis does not yet provide a definitive answer as to whether the concept of an elementary reaction is universally applicable to the apparently simple process of methane dissociation. Similarly, the literature currently lacks a comprehensive and unambiguous description of the methane pyrolysis process and, in particular, a single model that would well represent its course at both the micro and macro scales. Given the wide range of conditions under which this reaction can occur—whether thermal or thermo-catalytic, in solid or fluidized bed reactors—it is crucial to evaluate the usefulness of different kinetic models and their compatibility with basic thermodynamic principles and design assumptions. To address these research gaps, the authors analysed the thermodynamic and kinetic dependencies involved in the thermal decomposition of methane, using the synthesis of methane from its elemental components and its reversibility as a basis for exploring suitable kinetic models. Using experimental data available in the literature, a wide range of kinetic models have been analysed to determine how they all relate to the reaction rate constant. It was found that regardless of whether the process is catalytic or purely thermal, for temperatures above 900 °C the reversibility of the reaction has a negligible effect on the hydrogen yield. This work shows how the determined kinetic parameters are consistent with the Kinetic Compensation Effect (KCE) and, by incorporating elements of Transition State Theory (TST), the possibility of the existence of Entropy–Enthalpy Compensation (EEC). The indicated correspondence between KCE and EEC is strengthened by the calculated average activation entropy at isokinetic temperature

({∆ S}_{B} = - 275.0 J \cdot (m o l \cdot K)^{- 1}) .

Based on these results, the authors also show that changes in the activation energy

(E = 20 - 421 k J \cdot {m o l}^{- 1})

can only serve as an estimate of the optimal process conditions, since the isoconversion temperature (

T_{i s o} = 1200 - 1450 K > T_{e q}

) is shown to depend not only on thermodynamic principles but also on the way the reaction is carried out, with temperature (T) and pressure (P) locally compensating each other. Full article

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

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17 pages, 3255 KiB

Open AccessArticle

Bidding Strategy for the Alliance of Prosumer Aggregators in the Distribution Market

by Chunyi Wang, Jiawei Xing, Yuejiao Wang, Jing Xu, Zhixin Fu, Benjie Xu and Haoming Liu

Energies 2024, 17(19), 5006; https://doi.org/10.3390/en17195006 - 8 Oct 2024

Photovoltaic energy storage system (PV-ESS) prosumer aggregators are characterized by a large number but small scale in the distribution system and are not competitive enough to participate in market transactions. For this reason, a prosumer aggregator alliance is proposed to participate in the [...] Read more.

Photovoltaic energy storage system (PV-ESS) prosumer aggregators are characterized by a large number but small scale in the distribution system and are not competitive enough to participate in market transactions. For this reason, a prosumer aggregator alliance is proposed to participate in the distribution market bidding strategy. Firstly, based on the framework for prosumer aggregator alliances participating in distribution market trading, a bilevel bidding model is constructed. The upper level represents the optimal decision-making model for the prosumer aggregators, while the lower level constitutes the distribution market-clearing model. Secondly, the additional benefits obtained by the alliance are distributed more fairly using the improved Shapley value based on the PV self-consumption rate. Given the problem that the traditional diagonalization algorithm (DA) has an excessive number of iterations when solving the game equilibrium problem of multiple subjects, the DA is improved by optimizing the initial value of the inputs. Finally, case studies are conducted based on the improved IEEE-33 bus distribution system to validate the feasibility and economic viability of the proposed strategy. The case study results show that forming cooperative alliances to participate in market bidding can significantly increase overall profits. The improved DA reduces the number of bids and computation time by 75% and 80%, respectively. Additionally, the improved Shapley value facilitates compensation for some of the aggregators. Full article

(This article belongs to the Special Issue Operation and Control of Distributed Power Resources Under Market Environment)

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17 pages, 5718 KiB

Open AccessArticle

Analysis of Electricity Supply and Demand Balance in Residential Microgrids Integrated with Micro-CAES in Northern Portugal

by Jan Markowski, Jacek Leszczyński, Paula Fernanda Varandas Ferreira, Géremi Gilson Dranka and Dominik Gryboś

Energies 2024, 17(19), 5005; https://doi.org/10.3390/en17195005 - 8 Oct 2024

As global energy demand continues to rise, integrating renewable energy sources (RES) into power systems has become increasingly important. However, the intermittent nature of RES, such as solar and wind, presents challenges for maintaining a stable energy supply. To address this issue, energy [...] Read more.

As global energy demand continues to rise, integrating renewable energy sources (RES) into power systems has become increasingly important. However, the intermittent nature of RES, such as solar and wind, presents challenges for maintaining a stable energy supply. To address this issue, energy storage systems are essential. One promising technology is micro-compressed air energy storage (micro-CAES), which stores excess energy as compressed air and releases it when needed to balance supply and demand. This study investigates the integration of micro-CAES with RES in a 19-home microgrid in northern Portugal. The research aims to evaluate the effectiveness of a microgrid configuration that includes 100 kW of solar PV, 70 kW of wind power, and a 50 kWh micro-CAES system. Using real-world data on electricity consumption and local renewable potential, a simulation is conducted to assess the performance of this system. The findings reveal that this configuration can supply up to 68.8% of the annual energy demand, significantly reducing reliance on the external grid and enhancing the system’s resilience. These results highlight the potential of micro-CAES to improve the efficiency and sustainability of small-scale renewable energy systems, demonstrating its value as a key component in future energy solutions. Full article

(This article belongs to the Section F1: Electrical Power System)

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