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 (Engineering (miscellaneous))
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 16.1 days after submission; acceptance to publication is undertaken in 3.3 days (median values for papers published in this journal in the second half of 2023).
- 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: Fuels, Gases, Nanoenergy Advances and Solar.
Impact Factor:
3.2 (2022);
5-Year Impact Factor:
3.3 (2022)
Latest Articles
Gasification of Liquid Hydrocarbon Waste by the Ultra-Superheated Mixture of Steam and Carbon Dioxide: A Thermodynamic Study
Energies 2024, 17(9), 2126; https://doi.org/10.3390/en17092126 (registering DOI) - 29 Apr 2024
Abstract
The thermodynamic modeling of waste oil (WO) gasification by a high-temperature gasification agent (GA) composed of an ultra-superheated H2O/CO2 mixture is carried out. The GA is assumed to be obtained by the gaseous detonation of fuel–oxidizer–diluent mixture in a pulsed
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The thermodynamic modeling of waste oil (WO) gasification by a high-temperature gasification agent (GA) composed of an ultra-superheated H2O/CO2 mixture is carried out. The GA is assumed to be obtained by the gaseous detonation of fuel–oxidizer–diluent mixture in a pulsed detonation gun (PDG). N-hexadecane is used as a WO surrogate. Methane or the produced syngas (generally a mixture of H2, CO, CH4, CO2, etc.) is used as fuel for the PDG. Oxygen, air, or oxygen-enriched air are used as oxidizers for the PDG. Low-temperature steam is used as a diluent gas. The gasification process is assumed to proceed in a flow-through gasifier at atmospheric pressure. It is shown that the use of the detonation products of the stoichiometric methane–oxygen and methane–air mixtures theoretically leads to the complete conversion of WO into a syngas consisting exclusively of H2 and CO, or into energy gas with high contents of CH4 and C2-C3 hydrocarbons and an LHV of 36.7 (fuel–oxygen mixture) and 13.6 MJ/kg (fuel–air mixture). The use of the detonation products of the stoichiometric mixture of the produced syngas with oxygen or with oxygen-enriched air also allows theoretically achieving the complete conversion of WO into syngas consisting exclusively of H2 and CO. About 33% of the produced syngas mixed with oxygen can be theoretically used for PDG self-feeding, thus making the gasification technology very attractive and cost-effective. To self-feed the PDG with the mixture of the produced syngas with air, it is necessary to increase the backpressure in the gasifier and/or enrich the air with oxygen. The addition of low-temperature steam to the fuel–oxygen mixture in the PDG allows controlling the H2/CO ratio in the produced syngas from 1.3 to 3.4.
Full article
(This article belongs to the Special Issue Pyrolysis and Gasification of Biomass and Waste II)
Open AccessArticle
Design and Analysis of New Type of Magnetically Controlled Reactor
by
Yang Liu, Fuyao Yang, Yu Han, Jie Gao, Cong Wang, Dezhi Chen and Haonan Bai
Energies 2024, 17(9), 2125; https://doi.org/10.3390/en17092125 (registering DOI) - 29 Apr 2024
Abstract
In recent years, various new types of magnetic materials have emerged, especially in the field of nanotechnology. The application of material composite technology has formed a new type of dual-phase composite magnetic material. Under the control of an external magnetic field, the material
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In recent years, various new types of magnetic materials have emerged, especially in the field of nanotechnology. The application of material composite technology has formed a new type of dual-phase composite magnetic material. Under the control of an external magnetic field, the material can achieve functional conversion between the hard magnetic phase and the soft magnetic phase, with magnetic permeability, non-magnetic permeability, and excitation ability. In this paper, it is proposed to use this material as the basic material for the magnetic state control of the reactor core, break through the bondage of the traditional reactor core to the performance of the controllable reactor, and innovatively form a new type of reactor structure. By adding a detection and control system, according to the working state of the power grid, the function conversion of the nano adjustable magnetic material is effectively adjusted to realize the automatic adjustment of the magnetic state of the reactor. Firstly, the preparation and material properties of dual-phase composite magnetic materials were studied. The design and preparation process from magnetic powder to bulk magnet were given, and the magnetic properties were measured. Secondly, a new 380 V/100 kVar magnetically controlled reactor was designed by using dual-phase composite magnetic material to form a composite core of magnetically controlled reactor on silicon steel sheet. The simulation analysis of electromagnetic characteristics and volt-ampere characteristics was carried out to verify the correctness of the proposed scheme.
Full article
(This article belongs to the Section F: Electrical Engineering)
Open AccessArticle
Geochemical Characteristics of the Paleozoic Marine Source Rocks and Ultra-Deep Hydrocarbon Accumulation Mode of the Awati Sag
by
Zezhang Song, Ziyu Zhang, Xiaoheng Ding, Yuanyin Zhang, Zhongkai Bai, Lihong Liu and Yongjin Gao
Energies 2024, 17(9), 2124; https://doi.org/10.3390/en17092124 (registering DOI) - 29 Apr 2024
Abstract
The Lower Paleozoic of the Awati Sag and its periphery is a region with relatively low levels of exploration and stands as a frontier for ultra-deep hydrocarbon exploration. Based on outcrop and core samples, this study integrated organic geochemical analysis, total organic carbon
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The Lower Paleozoic of the Awati Sag and its periphery is a region with relatively low levels of exploration and stands as a frontier for ultra-deep hydrocarbon exploration. Based on outcrop and core samples, this study integrated organic geochemical analysis, total organic carbon (TOC) logging interpretation, and one-dimensional and two-dimensional hydrocarbon accumulation simulations, to clarify the primary source rock of the Lower Paleozoic and its characteristics, as well as its hydrocarbon accumulation mode. The findings indicate the following: (1) The Lower Paleozoic features two sets of industrial source rocks. The Yuertusi Formation, with its considerable thickness (approximately 200 m), widespread distribution, and elevated TOC (averaging approximately 5% from experimental data and logging interpretation), stands out as the Lower Paleozoic’s most pivotal source rock. (2) The Yuertusi and Saergan Formations are in a high-to-over-mature stage, with the Yuertusi initiating oil generation in the early Silurian and transitioning to gas by the late Permian. The Saergan began producing oil in the Carboniferous, followed by gas in the late Permian. (3) The potential ultra-deep gas reservoirs in the Awati Sag are mainly distributed in the structural traps closer to the deep faults in five potential target formations. Deep natural gas typically exhibits mixed-source signatures, with the mixing notably pronounced along the Shajingzi Fault Belt due to influential basin-controlling faults.
Full article
(This article belongs to the Section H: Geo-Energy)
Open AccessArticle
Monitoring Energy Flows for Efficient Electricity Control in Low-Voltage Smart Grids
by
Ivan Alymov and Moshe Averbukh
Energies 2024, 17(9), 2123; https://doi.org/10.3390/en17092123 (registering DOI) - 29 Apr 2024
Abstract
Modern low-voltage distribution lines, especially those linked with renewable energy sources, face technical hurdles like unaccounted and illegal electricity use, increased power losses, voltage control issues, and overheating. Tackling these challenges effectively requires continuously monitoring power flows and identifying problematic network spots. This
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Modern low-voltage distribution lines, especially those linked with renewable energy sources, face technical hurdles like unaccounted and illegal electricity use, increased power losses, voltage control issues, and overheating. Tackling these challenges effectively requires continuously monitoring power flows and identifying problematic network spots. This study introduces a method involving ongoing energy flow monitoring from distribution transformers and other sources to end-users through auxiliary facilities. The algorithm seamlessly integrates with consumers’ existing smart power meters and supporting infrastructure, eliminating the need for extra equipment or data. Deployed in several distribution networks totaling about 40 GWh/year over two years, this diagnostic system showed promising results. It notably cut total power consumption by around 6% by detecting and mitigating illegal energy waste and addressing technical issues. Additionally, it reduced technical personnel involvement in operational tasks by approximately twentyfold, significantly enhancing network profitability overall.
Full article
(This article belongs to the Special Issue Control of Renewable Energy Sources in Power Systems and Smart Grids: 2nd Edition)
Open AccessArticle
Diminishing Performance of Pt/CNT in Ethanol Oxidation after High-Potential Scanning
by
Fengping Hu, Jinchang Xu, Lin Wei, Zhenyou Wang and Fangming Jiang
Energies 2024, 17(9), 2122; https://doi.org/10.3390/en17092122 (registering DOI) - 29 Apr 2024
Abstract
Regenerative fuel cells and the phenomenon of cell reversal (CR) necessitate creating robust catalyst layers for consistent performance in fuel cells. This research used in situ Raman spectroscopy to observe molecular alterations on carbon nanotube-supported platinum catalysts (Pt/CNT) during ethanol oxidation. Following a
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Regenerative fuel cells and the phenomenon of cell reversal (CR) necessitate creating robust catalyst layers for consistent performance in fuel cells. This research used in situ Raman spectroscopy to observe molecular alterations on carbon nanotube-supported platinum catalysts (Pt/CNT) during ethanol oxidation. Following a CR event simulation, the ethanol oxidation efficiency on Pt/CNT was amplified 2.8 times after high-potential scanning but reverted to its initial efficiency after 100 cycles. The adsorbed *CO2− species on Pt/CNT was pivotal for initiating ethanol oxidation, with the rate assessed through Raman analysis. In addition to water electrolysis, the carbon substrate was degraded. This study sheds light on the mechanisms behind catalyst degradation, steering the creation of more advanced catalysts.
Full article
(This article belongs to the Section I3: Energy Chemistry)
Open AccessArticle
The Reliability and Profitability of Virtual Power Plant with Short-Term Power Market Trading and Non-Spinning Reserve Diesel Generator
by
Reza Nadimi, Masahito Takahashi, Koji Tokimatsu and Mika Goto
Energies 2024, 17(9), 2121; https://doi.org/10.3390/en17092121 (registering DOI) - 29 Apr 2024
Abstract
This study examines the profitability and reliability of a virtual power plant (VPP) with the existence of a diesel genset (DG) in the day-ahead (DA) and intra-day (ID) power markets. The study’s unique contribution lies in integrating the VPP system with non-spinning reserve
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This study examines the profitability and reliability of a virtual power plant (VPP) with the existence of a diesel genset (DG) in the day-ahead (DA) and intra-day (ID) power markets. The study’s unique contribution lies in integrating the VPP system with non-spinning reserve DG while limiting the DG operation via minimum running time and maximum number of switching times (on/off) per day. This contribution decreases the renewables’ uncertainty and increases the VPP’s reliability. Moreover, the study proposes an optimization model as a decision-making support tool for power market participants to choose the most profitable short-term market. The proposed model suggests choosing the DA market in 62% of time (from 579 days) based on estimated VPP power supply, and market prices. Even though there is uncertainty about VPP power supply and market prices, the division between the plan and actual profits is 1.8 × 106 Japanese yen [JPY] per day on average. The share of surplus power sold from the mentioned gap is 5.5%, which implies the opportunity cost of inaccurate weather forecasting. The results also show that the reliability of the VPP system in the presence of a DG increases from 64.9% to 66.2% for 14 h and mitigates the loss of power load by 1.3%.
Full article
(This article belongs to the Section B: Energy and Environment)
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Open AccessArticle
Optimization of Frequency Modulation Energy Storage Configuration in Power Grid Based on Equivalent Full Cycle Model
by
Wentao Huang, Qingqing Zheng, Ying Hu, Yalan Huang and Shasha Zhou
Energies 2024, 17(9), 2120; https://doi.org/10.3390/en17092120 (registering DOI) - 29 Apr 2024
Abstract
This paper aims to meet the challenges of large-scale access to renewable energy and increasingly complex power grid structure, and deeply discusses the application value of energy storage configuration optimization scheme in power grid frequency modulation. Based on the equivalent full cycle model
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This paper aims to meet the challenges of large-scale access to renewable energy and increasingly complex power grid structure, and deeply discusses the application value of energy storage configuration optimization scheme in power grid frequency modulation. Based on the equivalent full cycle model and a large number of actual operation data, various energy storage technologies are technically analyzed, and the economic and environmental performance of different energy storage configuration schemes are comprehensively evaluated. On this basis, this paper puts forward a set of efficient and economical energy storage configuration optimization strategies to meet the demand of power grid frequency modulation and promote the wide application of energy storage technology. After an in-depth analysis, it is found that the optimized energy storage configuration scheme is excellent in technology, economy, and environmental protection. Specifically, in terms of technical performance, the optimization scheme has significantly improved key indicators such as energy storage efficiency, capacity and power, and response speed, which can better meet the requirements of power grid frequency modulation. Through the verification of actual operation data, it is found that the overall efficiency of the optimized energy storage configuration scheme is above 55%, which is helpful to the stability and efficiency of power grid frequency modulation. In terms of economic performance, although the initial investment cost of the optimization scheme may be high, it is found that it has good economy through the evaluation of long-term operation benefits. Considering that the energy storage system can reduce the operating cost of the power grid, improve the energy utilization rate, and achieve the optimization of cost-effectiveness in the long run, this scheme is economically feasible and attractive. In terms of environmental performance, the optimization scheme effectively reduces the negative impact on the environment by improving energy storage efficiency, reducing emissions, and optimizing resource utilization. This is not only conducive to the sustainable development of the power grid but also in line with the current global trend of promoting green and low-carbon transformation. To sum up, this paper not only provides an efficient and economical energy storage allocation optimization strategy for power grid frequency modulation but also provides a scientific basis for relevant decision-making departments. By promoting the practical application and development of energy storage technology, this paper is helpful to improve the frequency modulation ability of power grid, optimize energy structure, and reduce environmental pollution, and thus achieve the goal of sustainable energy development. The data results and in-depth analysis of this paper provide strong support for the practical application of energy storage configuration optimization scheme and also provide important reference for the further innovation and development of energy storage technology.
Full article
(This article belongs to the Special Issue Advanced Energy Storage Technologies and Applications (AESAs))
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Optimal Scheduling of Electricity and Carbon in Multi-Park Integrated Energy Systems
by
Kun Li, Yulong Ying, Xiangyu Yu and Jingchao Li
Energies 2024, 17(9), 2119; https://doi.org/10.3390/en17092119 (registering DOI) - 29 Apr 2024
Abstract
In order to maximize the utilization efficiency of renewable energy resources and reduce carbon costs in multi-park integrated energy systems (MIESs), this paper proposes an electricity–carbon energy scheduling method for MIESs, where a electricity–carbon joint trading market is established to allow energy interactions
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In order to maximize the utilization efficiency of renewable energy resources and reduce carbon costs in multi-park integrated energy systems (MIESs), this paper proposes an electricity–carbon energy scheduling method for MIESs, where a electricity–carbon joint trading market is established to allow energy interactions between IESs so as to satisfy their energy deficiencies and surpluses. Simultaneously, through leveraging differences in carbon prices among regions, carbon quotas are shared between all IESs, thereby reducing the overall carbon trading costs within the region. The paper also suggests that to encourage carbon cooperation between IESs, incentive measures such as government subsidies could be provided to foster collaboration. The simulation results demonstrate that the proposed electricity–carbon energy scheduling method for MIESs can effectively improve the utilization flexibility of various energy resources and obtain the higher economic benefits, compared with the traditional method where each IES operates independently.
Full article
(This article belongs to the Section C: Energy Economics and Policy)
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Open AccessArticle
Mean Field Game-Based Algorithms for Charging in Solar-Powered Parking Lots and Discharging into Homes a Large Population of Heterogeneous Electric Vehicles
by
Samuel M. Muhindo
Energies 2024, 17(9), 2118; https://doi.org/10.3390/en17092118 (registering DOI) - 29 Apr 2024
Abstract
An optimal daily scheme is presented to coordinate a large population of heterogeneous battery electric vehicles when charging in daytime work solar-powered parking lots and discharging into homes during evening peak-demand hours. First, we develop a grid-to-vehicle strategy to share the solar energy
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An optimal daily scheme is presented to coordinate a large population of heterogeneous battery electric vehicles when charging in daytime work solar-powered parking lots and discharging into homes during evening peak-demand hours. First, we develop a grid-to-vehicle strategy to share the solar energy available in a parking lot between vehicles where the statistics of their arrival states of charge are dictated by an aggregator. Then, we develop a vehicle-to-grid strategy so that vehicle owners with a satisfactory level of energy in their batteries could help to decongest the grid when they return by providing backup power to their homes at an aggregate level per vehicle based on a duration proposed by an aggregator. Both strategies, with concepts from Mean Field Games, would be implemented to reduce the standard deviation in the states of charge of batteries at the end of charging/discharging vehicles while maintaining some fairness and decentralization criteria. Realistic numerical results, based on deterministic data while considering the physical constraints of vehicle batteries, show, first, in the case of charging in a parking lot, a strong to slight decrease in the standard deviation in the states of charge at the end, respectively, for the sunniest day, an average day, and the cloudiest day; then, in the case of discharging into the grid, over three days, we observe at the end the same strong decrease in the standard deviation in the states of charge.
Full article
(This article belongs to the Special Issue Energy Management Systems of Electric Vehicles: New Trends and Dynamic Futures)
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Open AccessArticle
Combined Effects of Thermal Buoyancy, Wind Action, and State of the First-Floor Lobby Entrance on the Pressure Difference in a High-Rise Building
by
Haiwei Xu, Lingfeng Su, Wenjuan Lou and Hongyang Shan
Energies 2024, 17(9), 2117; https://doi.org/10.3390/en17092117 (registering DOI) - 29 Apr 2024
Abstract
The stack effect in high-rise buildings, stemming from an inside/outside temperature difference, may produce a significant pressure difference on the elevator doors, potentially causing elevator malfunctions. This effect can also be influenced by wind action and human behaviors, e.g., opening/closing of building entrances.
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The stack effect in high-rise buildings, stemming from an inside/outside temperature difference, may produce a significant pressure difference on the elevator doors, potentially causing elevator malfunctions. This effect can also be influenced by wind action and human behaviors, e.g., opening/closing of building entrances. In this study, a wind tunnel test was conducted to determine the real wind pressure distribution on a high-rise building in northern China. A numerical simulation utilizing the Conjunction of Multizone Infiltration Specialists software (COMIS) was carried out to investigate the pressure difference of elevator doors under the effects of thermal buoyancy, wind action, and opening/closing of the first-floor lobby entrance. An alternative solution of a locally strengthened envelope is proposed and validated for the studied building zone. The study reveals that the opening of the first-floor lobby entrance increases the pressure difference regardless of the environmental conditions, and the increase of wind speed tends to increase the pressure difference in winter but decrease it in summer. The proposed countermeasure combination, involving using revolving doors instead of swing doors, increasing additional partitions, and strengthening the local building envelope, was found to be synergistic and effective in reducing the pressure difference inside the building. The research findings offer practical engineering solutions for mitigating elevator door pressure challenges in high-rise buildings.
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(This article belongs to the Section A3: Wind, Wave and Tidal Energy)
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Development and Validation of a Novel Zero-Dimensional Heat Rejection Model for High-Efficiency Engines
by
Francesca Furia, Vittorio Ravaglioli, Alberto Cerofolini and Carlo Bussi
Energies 2024, 17(9), 2116; https://doi.org/10.3390/en17092116 (registering DOI) - 29 Apr 2024
Abstract
In recent years, the trend towards the performance maximization of modern internal combustion engines has led to the creation of accurate simulation models to optimize the engine design and operating conditions. Temperature management is crucial to achieve the performance goals of an internal
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In recent years, the trend towards the performance maximization of modern internal combustion engines has led to the creation of accurate simulation models to optimize the engine design and operating conditions. Temperature management is crucial to achieve the performance goals of an internal combustion engine without affecting the component’s reliability. Formula 1 mandates that only a limited number of experimental tests can be performed, which leads to the necessity of simulators capable of substituting empirical tests. Furthermore, the requirement of adapting the vehicle setup before each race weekend to maximize the performance on each circuit layout necessitates short computational time. To address this, the development of a zero-dimensional model of the thermal flows within an engine is presented in this paper. This model allows to precisely compute the dynamic variations of all the heat flows inside the combustion engine, excluding only the radiative ones and the engine components’ temperatures. The new simulation approach has been developed and validated on a Formula 1 engine and shown to be precise and fast. The results demonstrate the value of the proposed model with an average engine fluid temperature error of less than 1 °C for a computational cost comparable with on-board applications.
Full article
(This article belongs to the Special Issue Internal Combustion Engine: Research and Application—2nd Edition)
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Open AccessArticle
Online Estimation of Three-Phase Induction Motor Parameters Using an Extended Kalman Filter for Energy Saving
by
Sasiya Udomsuk, Kongpol Areerak, Tidarut Areerak and Kongpan Areerak
Energies 2024, 17(9), 2115; https://doi.org/10.3390/en17092115 (registering DOI) - 28 Apr 2024
Abstract
In this paper, the online estimation of three-phase induction motor parameters using an extended Kalman filter for energy saving is proposed. The optimal value of the stator current on the d-axis is calculated to obtain the minimum power loss. Accurate motor parameters
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In this paper, the online estimation of three-phase induction motor parameters using an extended Kalman filter for energy saving is proposed. The optimal value of the stator current on the d-axis is calculated to obtain the minimum power loss. Accurate motor parameters are required to calculate the optimal stator current value for energy saving. Hence, to estimate motor parameters in real time, an online estimator known as the extended Kalman filter is applied. The energy consumption results for the motor using the proposed approach (estimated parameters with extended Kalman filter) are compared with those obtained using the conventional approach and energy saving (fixed parameters without parameter estimation) approach. As revealed by the comparison results from implementation in a laboratory, the proposed approach can provide minimum power losses for the three-phase induction motor drive, and the maximum energy-saving percentage is 60.18% compared with using the conventional drive approach.
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(This article belongs to the Section F: Electrical Engineering)
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Charge Carrier Formation following Energy Gap Law in Photo-Activated Organic Materials for Efficient Solar Cells
by
Aniket Rana, Nikita Vashistha, Amit Kumar, Mahesh Kumar and Rajiv K. Singh
Energies 2024, 17(9), 2114; https://doi.org/10.3390/en17092114 (registering DOI) - 28 Apr 2024
Abstract
The charge carrier formation and transport in the pristine polymers as well as in the polymer–fullerene blend is still a hot topic of discussion for the scientific community. In the present work, the carrier generation in some prominent organic molecules has been studied
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The charge carrier formation and transport in the pristine polymers as well as in the polymer–fullerene blend is still a hot topic of discussion for the scientific community. In the present work, the carrier generation in some prominent organic molecules has been studied through ultrafast transient absorption spectroscopy. The identification of the exciton and polaron lifetimes of these polymers has led to device performance-related understanding. In the Energy Gap Law, the slope of the linear fit gradient (γ) of lifetimes vs. bandgap are subjected to the geometrical rearrangements experienced by the polymers during the non-radiative decay from the excited state to the ground state. The value of gradient (γ) for excitons and polarons is found to be −1.1 eV−1 and 1.14 eV−1, respectively. It suggests that the exciton decay to the ground state is likely to involve a high distortion in polymer equilibrium geometry. This observation supports the basis of Stokes shift found in the conjugated polymers due to the high disorder. It provides the possible reasons for the substantial variation in the exciton lifetime. As the bandgap becomes larger, exciton decay rate tends to reduce due to the weak attraction between the holes in the HUMO and electron in the LUMO. The precise inverse action is observed for the polymer–fullerene blend, as the decay of polaron tends to increase as the bandgap of polymer increases.
Full article
(This article belongs to the Special Issue New Insights into Solar Cells)
Open AccessArticle
Improved Error-Based Ensemble Learning Model for Compressor Performance Parameter Prediction
by
Xinguo Miao, Lei Liu, Zhiyong Wang and Xiaoming Chen
Energies 2024, 17(9), 2113; https://doi.org/10.3390/en17092113 (registering DOI) - 28 Apr 2024
Abstract
Large compressors have complex structures and constantly changing operating conditions. It is challenging to build physical models of compressors to analyse their performance parameters. An improved error-based stacked ensemble learning prediction model is proposed in this work. This model simplifies the modelling steps
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Large compressors have complex structures and constantly changing operating conditions. It is challenging to build physical models of compressors to analyse their performance parameters. An improved error-based stacked ensemble learning prediction model is proposed in this work. This model simplifies the modelling steps in a data-driven manner and obtains accurate prediction results. An enhanced integrated model employs K-fold cross-validation to assign dataset weights based on validation set errors, achieving a 12.4% reduction in average output error. Additionally, the output error of the meta-model undergoes a Box–Cox transformation for error compensation, decreasing the average output error by 14.0%. The Stacking model, combining the above improvements, notably reduces the root-mean-square errors for power, surge, and blocking boundaries by 24.2%, 20.6%, and 23.3%, respectively. This integration significantly boosts prediction accuracy.
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(This article belongs to the Section F5: Artificial Intelligence and Smart Energy)
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Enhancing the Efficiency of Rotary Thermal Propulsion Systems
by
Xuankun Shen and Aaron W. Costall
Energies 2024, 17(9), 2112; https://doi.org/10.3390/en17092112 (registering DOI) - 28 Apr 2024
Abstract
Transport electrification is essential for reducing CO2 emissions, and technologies such as hybrid and range-extended electric vehicles will play a crucial transitional role. Such vehicles employ an internal combustion engine for on-board chemical energy conversion. The Wankel rotary engine should be an
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Transport electrification is essential for reducing CO2 emissions, and technologies such as hybrid and range-extended electric vehicles will play a crucial transitional role. Such vehicles employ an internal combustion engine for on-board chemical energy conversion. The Wankel rotary engine should be an excellent candidate for this purpose, offering a high power-to-weight ratio, simplicity, compactness, perfect balance, and low cost. Until recently, however, it has not been in production in the automotive market, due, in part, to relatively low combustion efficiency and high fuel consumption and unburnt hydrocarbon emissions, which can be traced to constraints on flame speed, an elongated combustion chamber, and relatively low compression ratios. This work used large eddy simulations to study the in-chamber flow in a peripherally ported 225cc Wankel rotary engine, providing insight into these limitations. Flow structures created during the intake phase play a key role in turbulence production but the presence of the pinch point inherent to Wankel engine combustion chambers inhibits flame propagation. Two efficiency-enhancement technologies are introduced as disruptive solutions: (i) pre-chamber jet ignition and (ii) a two-stage rotary engine. These concepts overcome the traditional efficiency limitations and show that the Wankel rotary engine design can be further enhanced for its role as a range extender in electrified vehicles.
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(This article belongs to the Special Issue Disruptive Solutions for Innovative Internal Combustion Engines and Advanced Combustion)
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Energy Management Strategy for a Net Zero Emission Islanded Photovoltaic Microgrid-Based Green Hydrogen System
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Nisrine Naseri, Soumia El Hani, Mohamed Machmoum, Elhoussin Elbouchikhi and Amina Daghouri
Energies 2024, 17(9), 2111; https://doi.org/10.3390/en17092111 (registering DOI) - 28 Apr 2024
Abstract
Investing in green hydrogen systems has become a global objective to achieve the net-zero emission goal. Therefore, it is seen as the primary force behind efforts to restructure the world’s energy, lessen our reliance on gas, attain carbon neutrality, and combat climate change.
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Investing in green hydrogen systems has become a global objective to achieve the net-zero emission goal. Therefore, it is seen as the primary force behind efforts to restructure the world’s energy, lessen our reliance on gas, attain carbon neutrality, and combat climate change. This paper proposes a power management for a net zero emission PV microgrid-based decentralized green hydrogen system. The hybrid microgrid combines a fuel cell, battery, PV, electrolyzer, and compressed hydrogen storage (CHSU) unit aimed at power sharing between the total components of the islanded DC microgrid and minimizing the equivalent hydrogen consumption (EHC) by the fuel cell and the battery. In order to minimize the EHC and maintain the battery SOC, an optimization-based approach known as the Equivalent Consumption Minimization Strategy (ECMS) is used. A rule-based management is used to manage the power consumed by the electrolyzer and the CHSU by the PV system in case of excess power. The battery is controlled by an inverse droop control to regulate the dc bus voltage and the output power of the PV system is maximized by the fuzzy logic controller-based MPPT. As the hybrid microgrid works in the islanded mode, a two-level hierarchical control is applied in order to generate the voltage and the frequency references. The suggested energy management approach establishes the operating point for each system component in order to enhance the system’s efficiency. It allows the hybrid system to use less hydrogen while managing energy more efficiently.
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(This article belongs to the Section A1: Smart Grids and Microgrids)
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Simulation-Based Evaluation of the Impact of an Electrochromic Glazing on the Energy Use and Indoor Comfort of an Office Room
by
Henriqueta Teixeira, A. Moret Rodrigues, Daniel Aelenei and M. Glória Gomes
Energies 2024, 17(9), 2110; https://doi.org/10.3390/en17092110 (registering DOI) - 28 Apr 2024
Abstract
Electrochromic glazing alters its optical properties in the absence/presence of an electrical charge, varying from clear to dark to control daylighting and solar heat gains. This study aims to evaluate the impact of an electrochromic glazing, with indoor glare or temperature control, on
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Electrochromic glazing alters its optical properties in the absence/presence of an electrical charge, varying from clear to dark to control daylighting and solar heat gains. This study aims to evaluate the impact of an electrochromic glazing, with indoor glare or temperature control, on the energy performance and thermal and visual comfort of an office room under three European climates, using a calibrated simulation model. The novelty of the paper lies in its combined performance assessment, using different standards and metrics. The results showed reduced climatization energy requirements with temperature control, but significantly increased artificial lighting energy use. Glare control achieved useful illuminance levels during 74–80% of working hours. Concerning temperature control, working hours within thermal comfort increased (21–43%) under a free-float regime. Moreover, the performance of this glazing was compared to that of a clear glazing with/without a reflective film and a thermochromic glazing for different solar orientations. The electrochromic glazing with glare control showed the highest energy savings (14–36%) for a western orientation, and the lowest negative impact on daylighting for a northern orientation. The best glare reduction was achieved with the reflective film. Considering the free-float regime, the electrochromic glazing, with temperature control, showed the highest increase in working hours within thermal comfort (6–9%) for a western orientation.
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(This article belongs to the Special Issue Advanced Energy Systems in Energy Resilient, Zero/Positive Energy Buildings, Communities and Districts)
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Open AccessArticle
Experimental Study on Ultra-Low Concentration Methane Regenerative Thermal Oxidation
by
Junhui Yang, Liguo Yang, Jida Zhang, Xiaoxu Fan, Sheng Li, Luyao Zhang and Weijie Zhang
Energies 2024, 17(9), 2109; https://doi.org/10.3390/en17092109 (registering DOI) - 28 Apr 2024
Abstract
As a major coal country, China faces the issue of significant gas emissions during the coal mining process. This study aims to improve the utilization efficiency of mine gas, reduce greenhouse gas emissions, and promote the low-carbon and green transformation of the coal
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As a major coal country, China faces the issue of significant gas emissions during the coal mining process. This study aims to improve the utilization efficiency of mine gas, reduce greenhouse gas emissions, and promote the low-carbon and green transformation of the coal industry. A 10 kW gas regenerative thermal oxidizer (RTO) experimental system was constructed. The effects of initial methane concentration, low-temperature flue gas proportion, and operating load on combustion temperature, methane oxidation rate, high-temperature flue gas energy, and system thermal efficiency were studied. The results show that when the combustion temperature is below 600 °C, the CH4 combustion reaction cannot proceed effectively, and the system temperature continuously decreases and cannot be maintained stably. The experiment determines the stable operating methane concentration range of the RTO. In this experimental system, the lower limit of the initial methane concentration is 0.28%, corresponding to an 86% methane oxidation rate. As the initial methane concentration decreases, the combustion temperature also decreases, and the methane oxidation rate follows suit. The higher the low-temperature flue gas proportion, the higher the combustion temperature, and the system’s thermal efficiency and output heat decrease with the increase in the low-temperature flue gas proportion. This experiment explores multiple factors affecting regenerative thermal oxidation, providing a basis for ensuring the safe and stable operation of the system and its optimization. Improving the thermal insulation and heat exchange performance of the storage body can expand the lower limit of the initial methane concentration, thereby increasing the stability and thermal efficiency of the system.
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(This article belongs to the Topic Mining Safety and Sustainability, 2nd Volume)
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Open AccessEditorial
Advances in Numerical Heat Transfer and Fluid Flow
by
Artur S. Bartosik
Energies 2024, 17(9), 2108; https://doi.org/10.3390/en17092108 (registering DOI) - 28 Apr 2024
Abstract
Scientists continuously are looking for new methods that allow them to better understand the flow and heat transfer phenomena [...]
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(This article belongs to the Special Issue Numerical Heat Transfer and Fluid Flow 2023)
Open AccessArticle
Influence of Organic Matter Thermal Maturity on Rare Earth Element Distribution: A Study of Middle Devonian Black Shales from the Appalachian Basin, USA
by
Shailee Bhattacharya, Shikha Sharma, Vikas Agrawal, Michael C. Dix, Giovanni Zanoni, Justin E. Birdwell, Albert S. Wylie, Jr. and Tom Wagner
Energies 2024, 17(9), 2107; https://doi.org/10.3390/en17092107 (registering DOI) - 28 Apr 2024
Abstract
This study focuses on understanding the association of rare earth elements (REE; lanthanides + yttrium + scandium) with organic matter from the Middle Devonian black shales of the Appalachian Basin. Developing a better understanding of the role of organic matter (OM) and thermal
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This study focuses on understanding the association of rare earth elements (REE; lanthanides + yttrium + scandium) with organic matter from the Middle Devonian black shales of the Appalachian Basin. Developing a better understanding of the role of organic matter (OM) and thermal maturity in REE partitioning may help improve current geochemical models of REE enrichment in a wide range of black shales. We studied relationships between whole rock REE content and total organic carbon (TOC) and compared the correlations with a suite of global oil shales that contain TOC as high as 60 wt.%. The sequential leaching of the Appalachian shale samples was conducted to evaluate the REE content associated with carbonates, Fe–Mn oxyhydroxides, sulfides, and organics. Finally, the residue from the leaching experiment was analyzed to assess the mineralogical changes and REE extraction efficiency. Our results show that heavier REE (HREE) have a positive correlation with TOC in our Appalachian core samples. However, data from the global oil shales display an opposite trend. We propose that although TOC controls REE enrichment, thermal maturation likely plays a critical role in HREE partitioning into refractory organic phases, such as pyrobitumen. The REE inventory from a core in the Appalachian Basin shows that (1) the total REE ranges between 180 and 270 ppm and the OM-rich samples tend to contain more REE than the calcareous shales; (2) there is a relatively higher abundance of middle REE (MREE) to HREE than lighter REE (LREE); (3) there is a disproportionate increase in Y and Tb with TOC likely due to the rocks being over-mature; and (4) the REE extraction demonstrates that although the OM has higher HREE concentration, the organic leachates contain more LREE, suggesting it is more challenging to extract HREE from OM than using traditional leaching techniques.
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(This article belongs to the Special Issue Exploration and Development of Unconventional Oil and Gas Resources: Latest Advances and Prospects)
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