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 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
Multizone Modeling for Hybrid Thermal Energy Storage
Energies 2024, 17(12), 2854; https://doi.org/10.3390/en17122854 - 10 Jun 2024
Abstract
This study presents a one-dimensional mathematical model developed to simulate multi-zone thermal storage systems using phase change materials (PCMs). The model enables precise analysis of temperature distribution in the layered storage based on several PCM configurations and properties. It is distinguished by its
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This study presents a one-dimensional mathematical model developed to simulate multi-zone thermal storage systems using phase change materials (PCMs). The model enables precise analysis of temperature distribution in the layered storage based on several PCM configurations and properties. It is distinguished by its adaptability to various tank geometries and the number of PCM capsules, enabling its application under diverse operating conditions. By simplifying the implementation of heat transfer processes that depend on the shape of the capsule and the thermal properties of the PCM, the computation time can be reduced to a level that makes simulations over longer periods feasible. Experimental validation confirmed the accuracy of the model, with deviations below 6%, underscoring its practical applicability. The study demonstrates that individual layering in the storage tank can be achieved by filling it with PCMs of different melting points without compromising the maximum storage capacity. It is shown that including a PCM layer can maintain the outlet temperature 20% longer while storing 14% more energy. The results point out the model’s potential to improve the performance of thermal storage systems through targeted PCM layer configurations. The model serves as the basis for the planning and optimization of these systems.
Full article
(This article belongs to the Special Issue Highly Efficient Thermal Energy Storage (TES) Technologies)
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Open AccessArticle
Combustion Efficiency of Various Forms of Solid Biofuels in Terms of Changes in the Method of Fuel Feeding into the Combustion Chamber
by
Małgorzata Dula, Artur Kraszkiewicz and Stanisław Parafiniuk
Energies 2024, 17(12), 2853; https://doi.org/10.3390/en17122853 - 10 Jun 2024
Abstract
This study analyzes the combustion of pellets and briquettes made of plant biomass in low-power heating devices powered periodically with fuel being placed on the grate, as well as after modification using an automatic fuel feeding system in the gutter burner. The use
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This study analyzes the combustion of pellets and briquettes made of plant biomass in low-power heating devices powered periodically with fuel being placed on the grate, as well as after modification using an automatic fuel feeding system in the gutter burner. The use of herbaceous biomass in the form of pellets in low-power heating devices with automatic fuel feeding and combustion in a gutter burner is not widely promoted and popular. Therefore, this study used four types of herbaceous waste biomass (wheat straw, rye straw, oat straw and hay) and one type of woody waste biomass (birch sawdust) for testing. The basic chemical characteristics were determined for the raw materials. After appropriate preparation, the selected starting materials were subjected to briquetting and pelleting processes. Selected physical properties were also determined for the obtained biofuels. Biofuels made from birch sawdust had the lowest heat value (16.34 MJ·kg−1), although biofuels made from wheat, rye and hay straw had a slightly lower calorific value, respectively: 16.29; 16.28 and 16.26 MJ·kg−1. However, the calorific value of oat straw biofuels was only 15.47 MJ kg−1. Moreover, the ash content for herbaceous biomass was 2–4 times higher than for woody biomass. Similar differences between herbaceous and woody biomass were also observed for the nitrogen and sulfur content. To burn the prepared biofuels, a domestic grate-fired biomass boiler was used, periodically fed with portions of fuel in the form of pellets or briquettes (type A tests), which was then modified with a gutter burner enabling the automatic feeding of fuel in the form of pellets (type B tests). During the combustion tests with simultaneous timing, the concentration of CO2, CO, NO and SO2 in the exhaust gases was examined and the temperature of the supplied air and exhaust gases was measured. The stack loss (qA), combustion efficiency index (CEI) and toxicity index (TI) were also calculated. The research shows that the use of automatic fuel feeding stabilizes the combustion process. The combustion process is balanced between herbaceous and woody biomass biofuels. Disparities in CO2, CO and Tgas emissions are decreasing. However, during type B tests, an increase in NO emissions is observed. At the same time, the research conducted indicates that the combustion of herbaceous biomass pellets with their automatic feeding into the combustion chamber is characterized by an increase in combustion efficiency, indicating that when the combustion process is automated, they are a good replacement for wood biofuels—both pellets and briquettes.
Full article
(This article belongs to the Section I1: Fuel)
Open AccessReview
An Overview of Pyrolysis as Waste Treatment to Produce Eco-Energy
by
Ana B. Cuevas, David E. Leiva-Candia and M. P. Dorado
Energies 2024, 17(12), 2852; https://doi.org/10.3390/en17122852 - 10 Jun 2024
Abstract
The aim of this review is to understand the progress in waste material management through pyrolysis to produce eco-energy. The growing demand for energy, combined with the depletion of traditional fossil fuels and their contribution to environmental problems, has led to the search
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The aim of this review is to understand the progress in waste material management through pyrolysis to produce eco-energy. The growing demand for energy, combined with the depletion of traditional fossil fuels and their contribution to environmental problems, has led to the search for waste-to-energy technologies in pursuit of carbon neutrality. While municipal residues are only part of the waste management problem, the impact of discarded plastics on the environment and landfills is significant. Plastics not only take centuries to decompose, but also seriously pollute the oceans. Pyrolysis is a thermochemical process that allows for the thermal decomposition of waste in the absence of oxygen. There are several types of pyrolytic reactors, including batch and continuous ones. Batch reactors are preferred to process polymeric waste, with studies highlighting the importance of optimizing parameters, i.e., type of feedstock, heating rate, and pyrolysis temperature. Moreover, the choice of reactor type can influence the yield and structure of the final compounds. Furthermore, various studies have highlighted the gas heating value obtained through waste pyrolysis and how the composition of the liquid fraction is influenced by the type of polyethylene used. Though scientific interest in pyrolysis is remarkable, as publications have increased in recent years, kinetics studies are scarce. Overall, pyrolysis is a promising technique for managing waste materials to produce energy. Ongoing research and development in this area offer significant potential for improving the sustainability of waste management systems.
Full article
(This article belongs to the Special Issue In-Depth Investigations in Bioenergy)
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Open AccessArticle
Quantitative Analysis of Fracture Roughness and Multi-Field Effects for CO2-ECBM Projects
by
Lingshuo Zhang and Yafei Shan
Energies 2024, 17(12), 2851; https://doi.org/10.3390/en17122851 - 10 Jun 2024
Abstract
Carbon Dioxide-Enhanced Coalbed Methane (CO2-ECBM), a progressive technique for extracting coalbed methane, substantially boosts gas recovery and simultaneously reduces greenhouse gas emissions. In this process, the dynamics of coalbed fractures, crucial for CO2 and methane migration, significantly affect carbon storage
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Carbon Dioxide-Enhanced Coalbed Methane (CO2-ECBM), a progressive technique for extracting coalbed methane, substantially boosts gas recovery and simultaneously reduces greenhouse gas emissions. In this process, the dynamics of coalbed fractures, crucial for CO2 and methane migration, significantly affect carbon storage and methane retrieval. However, the extent to which fracture roughness, under the coupled thermal-hydro-mechanic effects, impacts engineering efficiency remains ambiguous. Addressing this, our study introduces a pioneering, cross-disciplinary mathematical model. This model innovatively quantifies fracture roughness, incorporating it with gas flow dynamics under multifaceted field conditions in coalbeds. This comprehensive approach examines the synergistic impact of CO2 and methane adsorption/desorption, their pressure changes, adsorption-induced coalbed stress, ambient stress, temperature variations, deformation, and fracture roughness. Finite element analysis of the model demonstrates its alignment with real-world data, precisely depicting fracture roughness in coalbed networks. The application of finite element analysis to the proposed mathematical model reveals that (1) fracture roughness ξ markedly influences residual coalbed methane and injected CO2 pressures; (2) coalbed permeability and porosity are inversely proportional to ξ; and (3) adsorption/desorption reactions are highly sensitive to ξ. This research offers novel insights into fracture behavior quantification in coalbed methane extraction engineering.
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(This article belongs to the Section H: Geo-Energy)
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Open AccessReview
A Review of Non-Isolated High-Gain Y-Source Converters Topologies
by
Hao Wang, Panbao Wang, Enpeng Yan, Wei Wang and Dianguo Xu
Energies 2024, 17(12), 2850; https://doi.org/10.3390/en17122850 - 10 Jun 2024
Abstract
Due to the low voltage and high randomness of renewable energy, high-performance grid-connected converters are needed. With the advantages of a high boost ratio, flexible design, and simple control, the Y-Source Converter (YSC) is widely concerned. However, there are a few drawbacks to
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Due to the low voltage and high randomness of renewable energy, high-performance grid-connected converters are needed. With the advantages of a high boost ratio, flexible design, and simple control, the Y-Source Converter (YSC) is widely concerned. However, there are a few drawbacks to the traditional Y-source converter, including significant switching stress, voltage voltage overshoot, and discontinuous current. To solve the problems above, a series of improved topologies are proposed. Moreover, the voltage gain, current ripple, and soft switching characteristics have also been optimized. So far, the existing literature lacks the collation and comparison of different topologies of Y-source, as well as the analysis of its evolution process. Therefore, this paper provides a comprehensive overview of Y-source converters’ topologies. According to their features and applications, different topologies are classified and described, leading to guidance for the selection of YSCs under different scenarios. Meanwhile, the working principle, evolution process, and vital issues are analyzed. By revealing their deductive rules, valuable suggestions are provided for the future development of YSCs.
Full article
(This article belongs to the Special Issue Power Electronic Converter Topologies and Control for Integration of Renewable Energy and Multi-Energy Sources)
Open AccessArticle
Modeling Pressure Gradient of Gas–Oil–Water Three-Phase Flow in Horizontal Pipes Downstream of Restrictions
by
Denghong Zhou and Yilin Fan
Energies 2024, 17(12), 2849; https://doi.org/10.3390/en17122849 - 10 Jun 2024
Abstract
Gas–oil–water three-phase slug flows in pipes commonly exist in the oil and gas industry as oil fields are becoming mature and water production is becoming inevitable. Although studies on multiphase flows in pipes have been ongoing for decades, most previous research has focused
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Gas–oil–water three-phase slug flows in pipes commonly exist in the oil and gas industry as oil fields are becoming mature and water production is becoming inevitable. Although studies on multiphase flows in pipes have been ongoing for decades, most previous research has focused on gas–liquid or oil–water two-phase flows, with limited studies on gas–liquid–liquid flows. This leads to limited modeling studies on gas–liquid–liquid flows. One factor contributing to the complexity of the gas–liquid–liquid flow is the mixing between the oil and water phases, which have closer fluid properties and low interfacial tension. Restrictions or piping components play a crucial role in altering phase mixing. Unfortunately, modeling studies that consider the effects of these restrictions are limited due to the scarcity of experimental research. To address this gap, we conducted experimental studies on a gas–liquid–liquid flow downstream of a restriction and developed a new mechanistic modeling approach to predict the pressure gradient. Our model focuses on the flow pattern where the oil and water phases are partially mixed. This work emphasizes the modeling approach. The model evaluation results show that the model outperforms other existing models, with an average absolute relative error of 6.71%. Additionally, the parametric study shows that the new modeling approach effectively captures the effects of restriction size, water cut, and gas and liquid flow rates on the three-phase slug flow pressure gradient in horizontal pipes. Most previous slug flow modeling work assumes either a stratified flow or fully dispersed flow between the oil and water phases. This work provides a novel perspective in modeling a three-phase slug flow in which the oil and water phases are partially mixed. In addition, this novel approach to modeling the restriction effects on the pressure gradient paves the way for future modeling for different types of piping components or restrictions.
Full article
(This article belongs to the Section H1: Petroleum Engineering)
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Open AccessArticle
Biomethane Production from the Two-Stage Anaerobic Co-Digestion of Cow Manure: Residual Edible Oil with Two Qualities of Waste-Activated Sludge
by
Jesus Eduardo de la Cruz-Azuara, Alejandro Ruiz-Marin, Yunuen Canedo-Lopez, Claudia Alejandra Aguilar-Ucan, Rosa Maria Ceron-Breton, Julia Griselda Ceron-Breton and Francisco Anguebes-Franseschi
Energies 2024, 17(12), 2848; https://doi.org/10.3390/en17122848 - 10 Jun 2024
Abstract
Wastewater treatment systems produce large volumes of sludge which is not used; its final disposal is in soil or landfill. This sludge represents a biomethane-energy alternative through anaerobic co-digestion, contributing to reducing the environmental impacts caused by their inadequate disposal. Biomethane production by
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Wastewater treatment systems produce large volumes of sludge which is not used; its final disposal is in soil or landfill. This sludge represents a biomethane-energy alternative through anaerobic co-digestion, contributing to reducing the environmental impacts caused by their inadequate disposal. Biomethane production by the two-stage production method in batch digesters with pH and temperature control was evaluated by two qualities of waste-activated sludge (SLB50 and SLB90) and with a mixture of two co-substrates: cow manure (CEV50 and CEV90) and residual edible oil (CAV50 and CAV90). Bacteria in good-quality sludge (SLB90) showed a faster adaptation of 2 days than those in low-quality sludge (SLB50), with a 25-day lag phase. The highest CH4 production was for SLB90 (303.99 cm3 d−1) compared to SLB50 (4.33 cm3 d−1). However, the cow manure–sludge mixture (CEV90) contributed to the increased production of CH4 (42,422.8 cm3 d−1) compared to CEV50 (12,881.45 cm3 CH4 d−1); for CAV90 and CAV50, these were 767.32 cm3 d−1 and 211.42 cm3 d−1, respectively. The addition of sludge co-substrates improves the nutrient balance and C/N ratio; consequently, methane production improves. This methodology could be integrated into concepts of the circular economy.
Full article
(This article belongs to the Section B: Energy and Environment)
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Open AccessArticle
Performance Analysis of Vermiculite–Potassium Carbonate Composite Materials for Efficient Thermochemical Energy Storage
by
Jianquan Lin, Qian Zhao and Haotian Huang
Energies 2024, 17(12), 2847; https://doi.org/10.3390/en17122847 - 9 Jun 2024
Abstract
In this study, the preparation of the composite material consisting of expanded vermiculite (EV) and potassium carbonate (K2CO3) was conducted using a solution impregnation method. Sorption and desorption experiments were undertaken to investigate the dynamic and thermodynamic properties of
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In this study, the preparation of the composite material consisting of expanded vermiculite (EV) and potassium carbonate (K2CO3) was conducted using a solution impregnation method. Sorption and desorption experiments were undertaken to investigate the dynamic and thermodynamic properties of the EV/K2CO3 composites with varying salt contents. The findings suggest that the EV/K2CO3 composites effectively address the issues of solution leakage resulting from the deliquescence and excessive hydration of pure K2CO3 salt, thereby substantially improving the water sorption capacity and overall stability of the composite materials. The salt content plays a vital role in the sorption and desorption processes of EV/K2CO3 composites. As the salt content rises, the resistance to sorption mass transfer increases, resulting in a decline in the average sorption rate. Concurrently, as the salt content increases, there is a corresponding increase in the average desorption rate, water uptake, and heat storage density. Specifically, at a temperature of 30 °C and a relative humidity of 60%, the EVPC40 composite with a salt content of 67.4% demonstrates water uptake, mass energy density, and volumetric energy density values of 0.68 g/g, 1633.6 kJ/kg, and 160 kWh/m3, respectively. In comparison to pure K2CO3 salt, the utilization of EV/K2CO3 composites under identical heat demand conditions results in a 57% reduction in the required reaction material. This study offers essential empirical evidence and theoretical backing for the utilization and development of EV/K2CO3 composites within thermochemical energy storage systems.
Full article
(This article belongs to the Topic Thermal Energy Transfer and Storage)
Open AccessReview
Non-Linear Phenomena in Voltage and Frequency Converters Supplying Non-Thermal Plasma Reactors
by
Grzegorz Karol Komarzyniec, Henryka Danuta Stryczewska and Oleksandr Boiko
Energies 2024, 17(12), 2846; https://doi.org/10.3390/en17122846 - 9 Jun 2024
Abstract
Atmospheric pressure cold plasmas have recently been the subject of intense research and applications for solving problems in the fields of energy, environmental engineering, and biomedicine. Non-thermal atmospheric pressure plasma sources, with dielectric barrier discharges, plasma jets, and arc discharges, are non-linear power
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Atmospheric pressure cold plasmas have recently been the subject of intense research and applications for solving problems in the fields of energy, environmental engineering, and biomedicine. Non-thermal atmospheric pressure plasma sources, with dielectric barrier discharges, plasma jets, and arc discharges, are non-linear power loads. They require special power systems, which are usually designed separately for each type of plasma reactor, depending on the requirements of the plasma-chemical process, the power of the receiver, the type of process gas, the current, voltage and frequency requirements, and the efficiency of the power source. This paper presents non-linear phenomena accompanying plasma generation in the power supply plasma reactor system, such as harmonic generation, resonance, and ferroresonance of currents and voltages, and the switching of overvoltages and pulse generation. When properly applied, this can support the operation of the above-mentioned reactors by providing improved discharge ignition depending on the working gas, thus increasing the efficiency of the plasma process and improving the cooperation of the plasma-generation system with the power supply.
Full article
(This article belongs to the Special Issue Energy, Electrical and Power Engineering 2024)
Open AccessArticle
Study on Discharge Characteristic Performance of New Energy Electric Vehicle Batteries in Teaching Experiments of Safety Simulation under Different Operating Conditions
by
Meilin Gong, Jiatao Chen, Jianming Chen and Xiaohuan Zhao
Energies 2024, 17(12), 2845; https://doi.org/10.3390/en17122845 - 9 Jun 2024
Abstract
High-voltage heat release from batteries can cause safety issues for electric vehicles. Relevant scientific research work is carried out in the laboratory. The battery safety of laboratory experiments should not be underestimated. In order to evaluate the safety performance of batteries in the
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High-voltage heat release from batteries can cause safety issues for electric vehicles. Relevant scientific research work is carried out in the laboratory. The battery safety of laboratory experiments should not be underestimated. In order to evaluate the safety performance of batteries in the laboratory testing of driving conditions of electric vehicles, this paper simulated and compared the discharge characteristics of two common batteries (lithium iron phosphate (LFP) battery and nickel–cobalt–manganese (NCM) ternary lithium battery) in three different operating conditions. The operating conditions are the NEDC (New European Driving Cycle), WLTP (World Light Vehicle Test Procedure) and CLTC-P (China light vehicle test cycle) for normal driving of electric vehicles. LFP batteries have a higher maximum voltage and lower minimum voltage under the same initial voltage conditions, with a maximum voltage difference variation of 11 V. The maximum current of WLTP is significantly higher than NEDC and CLTC-P operating conditions (>20 A). Low current discharge conditions should be emulated in teaching simulation and experiments for safety reasons. The simulation data showed that the LFP battery had good performance in maintaining the voltage plateau and discharge voltage stability, while the NCM battery had excellent energy density and long-term endurance.
Full article
(This article belongs to the Special Issue Advances in Hybrid Vehicles: Volume II)
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Open AccessArticle
Combinatorial Component Day-Ahead Load Forecasting through Unanchored Time Series Chain Evaluation
by
Dimitrios Kontogiannis, Dimitrios Bargiotas, Athanasios Fevgas, Aspassia Daskalopulu and Lefteri H. Tsoukalas
Energies 2024, 17(12), 2844; https://doi.org/10.3390/en17122844 - 9 Jun 2024
Abstract
Accurate and interpretable short-term load forecasting tasks are essential to the optimal operation of liberalized electricity markets since they contribute to the efficient development of energy trading and demand response strategies as well as the successful integration of renewable energy sources. Consequently, performant
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Accurate and interpretable short-term load forecasting tasks are essential to the optimal operation of liberalized electricity markets since they contribute to the efficient development of energy trading and demand response strategies as well as the successful integration of renewable energy sources. Consequently, performant day-ahead consumption forecasting models need to capture feature nonlinearities, analyze system dynamics and conserve evolving temporal patterns in order to minimize the impact of noise and adapt to concept drift. Prominent estimators and standalone decomposition-based approaches may not fully address those challenges as they often yield small error rate improvements and omit optimal time series evolution. Therefore, in this work we propose a combinatorial component decomposition method focused on the selection of important renewable generation component sequences extracted from the combined output of seasonal-trend decomposition using locally estimated scatterplot smoothing, singular spectrum analysis and empirical mode decomposition methods. The proposed method was applied on five well-known kernel models in order to evaluate day-ahead consumption forecasts on linear, tree-based and neural network structures. Moreover, for the assessment of pattern conservation, an intuitive metric function, labeled as Weighted Average Unanchored Chain Divergence (WAUCD), based on distance scores and unanchored time series chains is introduced. The results indicated that the application of the combinatorial component method improved the accuracy and the pattern conservation capabilities of most models substantially. In this examination, the long short-term memory (LSTM) and deep neural network (DNN) kernels reduced their mean absolute percentage error by 46.87% and 42.76% respectively and predicted sequences that consistently evolved over 30% closer to the original target in terms of daily and weekly patterns.
Full article
(This article belongs to the Special Issue Energy, Electrical and Power Engineering 2024)
Open AccessArticle
Influence of γ-Fe2O3 Nanoparticles Added to Gasoline–Bio-Oil Blends Derived from Plastic Waste on Combustion and Emissions Generated in a Gasoline Engine
by
Paul Palmay, Diego Barzallo, Cesar Puente, Ricardo Robalino, Dayana Quinaluisa and Joan Carles Bruno
Energies 2024, 17(12), 2843; https://doi.org/10.3390/en17122843 - 9 Jun 2024
Abstract
The environmental pressure to reduce the use of fossil fuels such as gasoline generates the need to search for new fuels that have similar characteristics to conventional fuels. In this sense, the objective of the present study is the use of commercial gasoline
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The environmental pressure to reduce the use of fossil fuels such as gasoline generates the need to search for new fuels that have similar characteristics to conventional fuels. In this sense, the objective of the present study is the use of commercial gasoline in mixtures with pyrolytic oil from plastic waste and the addition of γ-Fe2O3 nanoparticles (NPs) in a spark ignition engine to analyze both the power generated in a real engine and the emissions resulting from the combustion process. The pyrolytic oil used was obtained from thermal pyrolysis at low temperatures (450 °C) of a mixture composed of 75% polystyrene (PS) and 25% polypropylene (PP), which was mixed with 87 octane commercial gasoline in 2% and 5% by volume and 40 mg of γ-Fe2O3 NPs. A standard sample was proposed, which was only gasoline, one mixture of gasoline with bio-oil, and a gasoline, bio-oil, and NPs mixture. The bio-oil produced from the pyrolysis of PS and PP enhances the octane number of the fuel and improves the engine’s power performance at low revolutions. In contrast, the addition of iron NPs significantly improves gaseous emissions with a reduction in emissions of CO (carbon monoxide), NOx (nitrogen oxide), and HCs (hydrocarbons) due to its advantages, which include its catalytic effect, presence of active oxygen, and its large surface area.
Full article
(This article belongs to the Section I1: Fuel)
Open AccessArticle
A Study on the Distribution Dynamics, Regional Disparities, and Convergence of China’s Energy Transition
by
Peifang Tian, Zhiyuan Gao and Yu Hao
Energies 2024, 17(12), 2842; https://doi.org/10.3390/en17122842 - 9 Jun 2024
Abstract
Abstract: Energy transition, as a crucial aspect of the country’s high-value-added economic development, involves the construction of an energy transition index system and empirical analysis using methods such as the entropy weighting method, kernel density estimation, Markov chain, Dagum Gini coefficient, σ-convergence, and
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Abstract: Energy transition, as a crucial aspect of the country’s high-value-added economic development, involves the construction of an energy transition index system and empirical analysis using methods such as the entropy weighting method, kernel density estimation, Markov chain, Dagum Gini coefficient, σ-convergence, and β-convergence. This study measures the level of energy transition in 280 Chinese cities from 2010 to 2019 and analyzes their evolutionary trends, regional disparities, structural differences, and convergence. The findings reveal that China’s energy transition generally exhibits characteristics of “improvement in development levels and reduction in absolute disparities”. The disparities in energy transition primarily stem from developmental differences among the three major regions, displaying typical σ-convergence and β-convergence characteristics. This analysis contributes to understanding the real level and distribution features of China’s energy transition, providing a basis for identifying focal points for enhancing energy transition in the current and future stages.
Full article
(This article belongs to the Section C: Energy Economics and Policy)
Open AccessArticle
A Dynamic Tanks-in-Series Model for a High-Temperature PEM Fuel Cell
by
Valery A. Danilov, Gunther Kolb and Carsten Cremers
Energies 2024, 17(12), 2841; https://doi.org/10.3390/en17122841 - 9 Jun 2024
Abstract
A dynamic tanks-in-series model has been developed for the coupled heat, mass, and charge transfer processes in a high-temperature proton exchange membrane fuel cell. The semi-empirical model includes the heat and mass balance equations in the gas channels and the membrane electrode assembly
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A dynamic tanks-in-series model has been developed for the coupled heat, mass, and charge transfer processes in a high-temperature proton exchange membrane fuel cell. The semi-empirical model includes the heat and mass balance equations in the gas channels and the membrane electrode assembly together with the charge balance at the electrode/membrane interfaces. The outputs of the tanks-in-series model are the concentration, the temperature, and the current density with a step change from tank to tank. The dynamic non-isothermal model is capable of predicting both the transient and steady-state behavior of the fuel cell and reproducing impedance data under harmonic perturbations of the cell potential together with a comprehensive interpretation of experimental data.
Full article
(This article belongs to the Special Issue Solid Oxide Fuel Cells: Modelling and Research)
Open AccessArticle
Weather-Based Prediction of Power Consumption in District Heating Network: Case Study in Finland
by
Aleksei Vakhnin, Ivan Ryzhikov, Christina Brester, Harri Niska and Mikko Kolehmainen
Energies 2024, 17(12), 2840; https://doi.org/10.3390/en17122840 - 9 Jun 2024
Abstract
Accurate prediction of energy consumption in district heating systems plays an important role in supporting effective and clean energy production and distribution in dense urban areas. Predictive models are needed for flexible and cost-effective operation of energy production and usage, e.g., using peak
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Accurate prediction of energy consumption in district heating systems plays an important role in supporting effective and clean energy production and distribution in dense urban areas. Predictive models are needed for flexible and cost-effective operation of energy production and usage, e.g., using peak shaving or load shifting to compensate for heat losses in the pipeline. This helps to avoid exceedance of power plant capacity. The purpose of this study is to automate the process of building machine learning (ML) models to solve a short-term power demand prediction problem. The dataset contains a district heating network’s measured hourly power consumption and ambient temperature for 415 days. In this paper, we propose a hybrid evolutionary-based algorithm, named GA-SHADE, for the simultaneous optimization of ML models and feature selection. The GA-SHADE algorithm is a hybrid algorithm consisting of a Genetic Algorithm (GA) and success-history-based parameter adaptation for differential evolution (SHADE). The results of the numerical experiments show that the proposed GA-SHADE algorithm allows the identification of simplified ML models with good prediction performance in terms of the optimized feature subset and model hyperparameters. The main contributions of the study are (1) using the proposed GA-SHADE, ML models with varying numbers of features and performance are obtained. (2) The proposed GA-SHADE algorithm self-adapts during operation and has only one control parameter. There is no fine-tuning required before execution. (3) Due to the evolutionary nature of the algorithm, it is not sensitive to the number of features and hyperparameters to be optimized in ML models. In conclusion, this study confirms that each optimized ML model uses a unique set and number of features. Out of the six ML models considered, SVR and NN are better candidates and have demonstrated the best performance across several metrics. All numerical experiments were compared against the measurements and proven by the standard statistical tests.
Full article
(This article belongs to the Special Issue Artificial Intelligence in Energy Efficient Buildings)
Open AccessArticle
Trace Elements in Maize Biomass Used to Phyto-Stabilise Iron-Contaminated Soils for Energy Production
by
Mirosław Wyszkowski and Natalia Kordala
Energies 2024, 17(12), 2839; https://doi.org/10.3390/en17122839 - 8 Jun 2024
Abstract
The aim of the study was to determine the feasibility of using maize biomass for the phyto-stabilisation of iron-contaminated soils under conditions involving the application of humic acids (HAs). The biomass yield content of maize trace elements was analysed. In the absence of
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The aim of the study was to determine the feasibility of using maize biomass for the phyto-stabilisation of iron-contaminated soils under conditions involving the application of humic acids (HAs). The biomass yield content of maize trace elements was analysed. In the absence of HAs, the first dose of Fe-stimulated plant biomass growth was compared to the absence of Fe contamination. The highest soil Fe contamination resulted in a very large reduction in maize biomass yield, with a maximum of 93%. The addition of HAs had a positive effect on plant biomass, with a maximum of 53%, and reduced the negative effect of Fe. There was an almost linear increase in maize biomass yield with increasing doses of HAs. Analogous changes were observed in dry matter content in maize. Soil treatment with Fe caused a significant increase in its content in maize biomass, with a maximum increase of three times in the series without HAs. There was also a decrease in Co, Cr and Cd content (by 17%, 21% and 44%, respectively) and an increase in Cu, Ni, Pb, Zn and Mn accumulation (by 32%, 63%, 75%, 97% and 203%, respectively). The application of HAs to the soil reduced the content of this trace element and its growth in the biomass of this plant under the influence of Fe contamination. They had a similar effect on other trace elements contained in the maize biomass. HAs contributed to a decrease in the level of most of the tested trace elements (except Ni and Pb) in the maize biomass. The reduction ranged from 11% (Cr and Mn) to 72% (Cd). The accumulation of Ni and Pb in the maize biomass was higher in the objects with HAs application than in the series without their addition. Humic acid application is a promising method for the reduction of the effects of soil Fe contamination on plants.
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(This article belongs to the Special Issue Biomass and Bio-Energy—2nd Edition)
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Open AccessArticle
Advancing Industrial Process Electrification and Heat Pump Integration with New Exergy Pinch Analysis Targeting Techniques
by
Timothy Gordon Walmsley, Benjamin James Lincoln, Roger Padullés and Donald John Cleland
Energies 2024, 17(12), 2838; https://doi.org/10.3390/en17122838 - 8 Jun 2024
Abstract
The process integration and electrification concept has significant potential to support the industrial transition to low- and net-zero-carbon process heating. This increasingly essential concept requires an expanded set of process analysis tools to fully comprehend the interplay of heat recovery and process electrification
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The process integration and electrification concept has significant potential to support the industrial transition to low- and net-zero-carbon process heating. This increasingly essential concept requires an expanded set of process analysis tools to fully comprehend the interplay of heat recovery and process electrification (e.g., heat pumping). In this paper, new Exergy Pinch Analysis tools and methods are proposed that can set lower bound work targets by acutely balancing process heat recovery and heat pumping. As part of the analysis, net energy and exergy load curves enable visualization of energy and exergy surpluses and deficits. As extensions to the grand composite curve in conventional Pinch Analysis, these curves enable examination of different pocket-cutting strategies, revealing their distinct impacts on heat, exergy, and work targets. Demonstrated via case studies on a spray dryer and an evaporator, the exergy analysis targets net shaft-work correctly. In the evaporator case study, the analysis points to the heat recovery pockets playing an essential role in reducing the work target by 25.7%. The findings offer substantial potential for improved industrial energy management, providing a robust framework for engineers to enhance industrial process and energy sustainability.
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(This article belongs to the Special Issue Advanced Research on Heat Exchangers Networks and Heat Recovery)
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Open AccessArticle
Energy Poverty and Democratic Values: A European Perspective
by
Aleksy Kwilinski, Oleksii Lyulyov and Tetyana Pimonenko
Energies 2024, 17(12), 2837; https://doi.org/10.3390/en17122837 - 8 Jun 2024
Abstract
This paper explores the complex relationship between energy poverty and the maintenance of democratic values within the European Union (EU), suggesting that energy poverty not only impacts economic stability and health outcomes but also poses significant challenges to democratic engagement and equity. To
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This paper explores the complex relationship between energy poverty and the maintenance of democratic values within the European Union (EU), suggesting that energy poverty not only impacts economic stability and health outcomes but also poses significant challenges to democratic engagement and equity. To measure energy poverty, a composite index is developed using the entropy method, which surpasses traditional measures focused solely on access to energy or its developmental implications. To assess the level of democratic governance in EU countries, the voice and accountability index (VEA), which is part of the World Governance Indicators compiled by the World Bank, is utilized. By analyzing EU data from 2006 to 2022, the findings suggest that a 1% improvement in VEA quality, represented by a coefficient of 0.122, is correlated with a notable improvement in the energy poverty index. This suggests that the EU should focus on enhancing transparency and public participation in energy decision-making, along with ensuring accountability in policy implementation. The research also differentiates between full and flawed democracies, noting that tailored approaches are needed. In full democracies, leveraging economic prosperity and trade is crucial due to their significant positive impacts on the energy poverty index. In contrast, in flawed democracies, enhancing governance and accountability is more impactful, as evidenced by a higher coefficient of 0.193. Strengthening legal and regulatory frameworks, improving regulatory quality, and ensuring public engagement in governance could substantially mitigate energy poverty in these contexts. In addition, this paper demonstrates that this relationship is influenced by factors such as income inequality, energy intensity, and trade openness.
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(This article belongs to the Special Issue Environmental Footprint of Energy Production and Storage Systems Based on Renewable Energy Sources)
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Open AccessReview
Comprehensive Overview of Recent Research and Industrial Advancements in Nuclear Hydrogen Production
by
Venizelos Venizelou and Andreas Poullikkas
Energies 2024, 17(12), 2836; https://doi.org/10.3390/en17122836 - 8 Jun 2024
Abstract
As new sources of energy and advanced technologies are used, there is a continuous evolution in energy supply, demand, and distribution. Advanced nuclear reactors and clean hydrogen have the opportunity to scale together and diversify the hydrogen production market away from fossil fuel-based
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As new sources of energy and advanced technologies are used, there is a continuous evolution in energy supply, demand, and distribution. Advanced nuclear reactors and clean hydrogen have the opportunity to scale together and diversify the hydrogen production market away from fossil fuel-based production. Nevertheless, the technical uncertainties surrounding nuclear hydrogen processes necessitate thorough research and a solid development effort. This paper aims to position pink hydrogen for nuclear hydrogen production at the forefront of sustainable energy-related solutions by offering a comprehensive review of recent advancements in nuclear hydrogen production, covering both research endeavors and industrial applications. It delves into various pink hydrogen generation methodologies, elucidating their respective merits and challenges. Furthermore, this paper analyzes the evolving landscape of pink hydrogen in terms of its levelized cost by comparatively assessing different production pathways. By synthesizing insights from academic research and industrial practices, this paper provides valuable perspectives for stakeholders involved in shaping the future of nuclear hydrogen production.
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(This article belongs to the Special Issue Advances in Hydrogen Energy III)
Open AccessArticle
A Two-Stage Twisted Blade μ-Vertical Axis Wind Turbine: An Enhanced Savonius Rotor Design
by
Andrés Pérez-Terrazo, Martin Moreno, Iván Trejo-Zúñiga and José Alberto López
Energies 2024, 17(12), 2835; https://doi.org/10.3390/en17122835 - 8 Jun 2024
Abstract
Wind turbines are a solution for sustainable energy, significantly reducing carbon emissions and fostering a circular economy for more cost-effective and cleaner power generation, in line with worldwide environmental aspirations. In this context, this research aims to explore a novel two-stage, twisted-blade micro-Vertical-Axis
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Wind turbines are a solution for sustainable energy, significantly reducing carbon emissions and fostering a circular economy for more cost-effective and cleaner power generation, in line with worldwide environmental aspirations. In this context, this research aims to explore a novel two-stage, twisted-blade micro-Vertical-Axis Wind Turbine ( -VAWT)alternative inspired by the Savonius Rotor (SR). This investigation utilizes the SST turbulence model to explore the power coefficient ( ) and torque coefficient ( ), finding values ranging from 0.02 to 0.08 across the turbine by altering the free stream velocity (V). analysis further delves into four specific sections, highlighting areas of particular interest. These results are validated by examining velocity contours, pressure contours, and streamlines in four horizontal sections, demonstrating that the proposed turbine model exhibits minimal torque fluctuation. Moreover, the analysis of vertical wind streamlines illustrates very low interference with various wind turbine proposals, underscoring the turbine’s efficiency and potential for integration into diverse wind energy projects.
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(This article belongs to the Special Issue Low Carbon Energy Generation and Utilization Technologies)
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