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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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27 pages, 3809 KiB  
Review
A Review of Coupled Geochemical–Geomechanical Impacts in Subsurface CO2, H2, and Air Storage Systems
by Zhuofan Shi, Dejene L. Driba, Nora Lopez Rivera, Mohammad Kariminasab and Lauren E. Beckingham
Energies 2024, 17(12), 2928; https://doi.org/10.3390/en17122928 - 14 Jun 2024
Viewed by 346
Abstract
Increased demand for decarbonization and renewable energy has led to increasing interest in engineered subsurface storage systems for large-scale carbon reduction and energy storage. In these applications, a working fluid (CO2, H2, air, etc.) is injected into a deep [...] Read more.
Increased demand for decarbonization and renewable energy has led to increasing interest in engineered subsurface storage systems for large-scale carbon reduction and energy storage. In these applications, a working fluid (CO2, H2, air, etc.) is injected into a deep formation for permanent sequestration or seasonal energy storage. The heterogeneous nature of the porous formation and the fluid–rock interactions introduce complexity and uncertainty in the fate of the injected component and host formations in these applications. Interactions between the working gas, native brine, and formation mineralogy must be adequately assessed to evaluate the efficiency, risk, and viability of a particular storage site and operational regime. This study reviews the current state of knowledge about coupled geochemical–geomechanical impacts in geologic carbon sequestration (GCS), underground hydrogen storage (UHS), and compressed air energy storage (CAES) systems involving the injection of CO2, H2, and air. Specific review topics include (1) existing injection induced geochemical reactions in these systems; (2) the impact of these reactions on the porosity and permeability of host formation; (3) the impact of these reactions on the mechanical properties of host formation; and (4) the investigation of geochemical-geomechanical process in pilot scale GCS. This study helps to facilitate an understanding of the potential geochemical–geomechanical risks involved in different subsurface energy storage systems and highlights future research needs. Full article
(This article belongs to the Collection Renewable Energy and Energy Storage Systems)
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29 pages, 9209 KiB  
Review
Biogas Upgrading Technology: Conventional Processes and Emerging Solutions Analysis
by Matteo Galloni and Gioele Di Marcoberardino
Energies 2024, 17(12), 2907; https://doi.org/10.3390/en17122907 - 13 Jun 2024
Viewed by 428
Abstract
The purpose of this research is to investigate a variety of approaches to the conversion of biomass, with a particular emphasis on employing anaerobic digestion and biogas upgrading systems. An analysis of the existing technologies is performed, with a focus on highlighting the [...] Read more.
The purpose of this research is to investigate a variety of approaches to the conversion of biomass, with a particular emphasis on employing anaerobic digestion and biogas upgrading systems. An analysis of the existing technologies is performed, with a focus on highlighting the benefits and downsides of each alternative. In order to assess the effects of nitrogen and oxygen in the biogas on the cryogenic distillation process, an investigation is being carried out. The findings suggest that the presence of these two chemical species in the biogas necessitates the final condensation of methane in order to separate them from one another. In conclusion, a qualitative economic analysis is carried out in order to ascertain the most cost-effective strategy that can be implemented in a typical Italian installation. According to the assumptions that were used, membrane separation is the solution that offers the most cost-effectiveness. Full article
(This article belongs to the Special Issue New Trends in Biofuels and Bioenergy for Sustainable Development II)
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24 pages, 2653 KiB  
Article
Energy Consumption Analysis and Characterization of the Residential Sector in the US towards Sustainable Development
by Khaled Bawaneh, Samir Das and Md. Rasheduzzaman
Energies 2024, 17(11), 2789; https://doi.org/10.3390/en17112789 - 6 Jun 2024
Viewed by 376
Abstract
In 2023, residential and commercial sectors together consumed approximately 27.6% of total United States (U.S.) energy, equivalent to about 20.6 quadrillion Btu. Factoring in the electrical system energy losses, the residential sector represented approximately 19.7% of total U.S. energy consumption during that time. [...] Read more.
In 2023, residential and commercial sectors together consumed approximately 27.6% of total United States (U.S.) energy, equivalent to about 20.6 quadrillion Btu. Factoring in the electrical system energy losses, the residential sector represented approximately 19.7% of total U.S. energy consumption during that time. There were approximately 144 million housing units in the United States in 2023, which is increasing yearly. In this study, information on energy usage in the United States residential sector has been analyzed and then represented as energy intensities to establish benchmark data and to compare energy consumption of varying sizes and locations. First, public sources were identified and data from these previously published sources were aggregated to determine the energy use of the residential sector within the US. Next, as part of this study, the energy data for seven houses/apartments from five different United States climate zones were collected firsthand. That data were analyzed, and the energy intensity of each home was calculated and then compared with the energy intensities of the other homes in the same states using Residential Energy Consumption Survey (RECS) data. The energy intensity for each facility was calculated based on the actual energy bills. Finally, the study evaluated the carbon footprint associated with residential energy consumption in all 50 states to reinforce the importance of sustainable development initiatives. Full article
(This article belongs to the Section A: Sustainable Energy)
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18 pages, 2358 KiB  
Article
Automotive e-Fuels via Hydrocracking of FT-Wax: e-Gasoline and e-Diesel Production
by Athanasios Dimitriadis, Loukia P. Chrysikou and Stella Bezergianni
Energies 2024, 17(11), 2756; https://doi.org/10.3390/en17112756 - 5 Jun 2024
Viewed by 325
Abstract
The main goal of this research is the production of e-fuels in gasoline- and diesel-range hydrocarbons via the hydrocracking of wax from Fischer–Tropsch (FT-wax) synthesis. The hydrogen for the hydrocracking process originated from solar energy via water electrolysis, thus, the produced fuels were [...] Read more.
The main goal of this research is the production of e-fuels in gasoline- and diesel-range hydrocarbons via the hydrocracking of wax from Fischer–Tropsch (FT-wax) synthesis. The hydrogen for the hydrocracking process originated from solar energy via water electrolysis, thus, the produced fuels were called e-fuels. The FT-wax was produced via the Fischer–Tropsch synthesis of syngas stream from the chemical looping gasification (CLG) of biogenic residues. For the hydrocracking tests, a continuous-operation TRL3 (Technology Readiness Level) pilot plant was utilized. At first, hydrocracking catalyst screening was performed for the upgrading of the FT-wax. Three hydrocracking catalysts were investigated (Ni-W, Ni-W zeolite-supported, and Ni-W Al2O3-supported catalyst) via various operating conditions to identify the optimal operating window for each one. These three catalysts were selected, as they are typical catalysts that are used in the petroleum refinery industry. The optimal catalyst was found to be the NiW catalyst, as it led to high e-fuel yields (38 wt% e-gasoline and 47 wt% e-diesel) with an average hydrogen consumption. The optimum operating window was found at a 603 K reactor temperature, 8.3 MPa system pressure, 1 hr−1 LHSV, and 2500 scfb H2/oil ratio. In the next phase, the production of 5 L of hydrocracked wax was performed utilizing the optimum NiW catalyst and the optimal operating parameters. The liquid product was further fractionated to separate the fractions of e-gasoline, e-diesel, and e-heavy fuel. The e-gasoline and e-diesel fractions were qualitatively assessed, indicating that they fulfilled almost all EN 228 and EN 590 for petroleum-based gasoline and diesel, respectively. Furthermore, a 12-month storage study showed that the product can be stored for a period of 4 months in ambient conditions. In general, green transportation e-fuels with favorable properties that met most of the fossil fuels specifications were produced successfully from the hydrocracking of FT-wax. Full article
(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)
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13 pages, 7199 KiB  
Article
Machine Learning Techniques for Spatio-Temporal Air Pollution Prediction to Drive Sustainable Urban Development in the Era of Energy and Data Transformation
by Mateusz Zareba, Szymon Cogiel, Tomasz Danek and Elzbieta Weglinska
Energies 2024, 17(11), 2738; https://doi.org/10.3390/en17112738 - 4 Jun 2024
Viewed by 466
Abstract
Sustainable urban development in the era of energy and digital transformation is crucial from a societal perspective. Utilizing modern techniques for analyzing large datasets, including machine learning and artificial intelligence, enables a deeper understanding of historical data and the efficient prediction of future [...] Read more.
Sustainable urban development in the era of energy and digital transformation is crucial from a societal perspective. Utilizing modern techniques for analyzing large datasets, including machine learning and artificial intelligence, enables a deeper understanding of historical data and the efficient prediction of future events based on data from IoT sensors. This study conducted a multidimensional historical analysis of air pollution to investigate the impacts of energy transformation and environmental policy and to determine the long-term environmental implications of certain actions. Additionally, machine learning (ML) techniques were employed for air pollution prediction, taking spatial factors into account. By utilizing multiple low-cost air sensors categorized as IoT devices, this study incorporated data from various locations and assessed the influence of neighboring sensors on predictions. Different ML approaches were analyzed, including regression models, deep neural networks, and ensemble learning. The possibility of implementing such predictions in publicly accessible IT mobile systems was explored. The research was conducted in Krakow, Poland, a UNESCO-listed city that has had long struggle with air pollution. Krakow is also at the forefront of implementing policies to prohibit the use of solid fuels for heating and establishing clean transport zones. The research showed that population growth within the city does not have a negative impact on PMx concentrations, and transitioning from coal-based to sustainable energy sources emerges as the primary factor in improving air quality, especially for PMx, while the impact of transportation remains less relevant. The best results for predicting rare smog events can be achieved using linear ML models. Implementing actions based on this research can significantly contribute to building a smart city that takes into account the impact of air pollution on quality of life. Full article
(This article belongs to the Special Issue Advancements in Sustainable Energy Technologies: Innovations, Integration, and Impact)
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15 pages, 3190 KiB  
Article
Novel Integrated Zeta Inverter for Standalone Applications
by Anderson Aparecido Dionizio, Guilherme Masquetti Pelz, Leonardo Poltronieri Sampaio and Sérgio Augusto Oliveira da Silva
Energies 2024, 17(11), 2748; https://doi.org/10.3390/en17112748 - 4 Jun 2024
Viewed by 301
Abstract
In recent years, distributed generation systems based on renewable energy sources have gained increasing prominence. Thus, the DC/AC converters based on power electronics devices have become increasingly important. In this context, this article presents an integrated Zeta inverter for low-power conditions, which operates [...] Read more.
In recent years, distributed generation systems based on renewable energy sources have gained increasing prominence. Thus, the DC/AC converters based on power electronics devices have become increasingly important. In this context, this article presents an integrated Zeta inverter for low-power conditions, which operates in continuous conduction mode (CCM), achieving efficiency greater than 95%. The proposed topology is composed of four power switches, two operating at high frequency and two operating at low frequency, i.e., at the output frequency. Compared with the topologies in the literature, these configurations make it a competitive solution from the point of view of efficiency, number of elements, and, consequently, implementation cost. The proposed converter operates as a sinusoidal voltage source for local loads and is supplied by a DC source, such as batteries or a photovoltaic array. A multi-resonant voltage controller was used to guarantee the sinusoidal voltage provided to the non-linear load while dealing with the complex dynamics of the Zeta converter in the CCM. Experimental results from a 324 W prototype show the converter’s implementation feasibility and the high efficiency of the DC/AC conversion. Full article
(This article belongs to the Special Issue Power Electronic and Power Conversion Systems for Renewable Energy)
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29 pages, 4449 KiB  
Article
Techno-Economic Assessment of Molten Salt-Based Concentrated Solar Power: Case Study of Linear Fresnel Reflector with a Fossil Fuel Backup under Saudi Arabia’s Climate Conditions
by Ahmed Aljudaya, Stavros Michailos, Derek B. Ingham, Kevin J. Hughes, Lin Ma and Mohamed Pourkashanian
Energies 2024, 17(11), 2719; https://doi.org/10.3390/en17112719 - 3 Jun 2024
Viewed by 248
Abstract
Concentrated solar power (CSP) has gained traction for generating electricity at high capacity and meeting base-load energy demands in the energy mix market in a cost-effective manner. The linear Fresnel reflector (LFR) is valued for its cost-effectiveness, reduced capital and operational expenses, and [...] Read more.
Concentrated solar power (CSP) has gained traction for generating electricity at high capacity and meeting base-load energy demands in the energy mix market in a cost-effective manner. The linear Fresnel reflector (LFR) is valued for its cost-effectiveness, reduced capital and operational expenses, and limited land impact compared to alternatives such as the parabolic trough collector (PTC). To this end, the aim of this study is to optimize the operational parameters, such as the solar multiple (SM), thermal energy storage (TES), and fossil fuel (FF) backup system, in LFR power plants using molten salt as a heat transfer fluid (HTF). A 50 MW LFR power plant in Duba, Saudi Arabia, serves as a case study, with a Direct Normal Irradiance (DNI) above 2500 kWh/m2. About 600 SM-TES configurations are analyzed with the aim of minimizing the levelized cost of electricity (LCOE). The analysis shows that a solar-only plant can achieve a low LCOE of 11.92 ¢/kWh with a capacity factor (CF) up to 36%, generating around 131 GWh/y. By utilizing a TES system, the SM of 3.5 and a 15 h duration TES provides the optimum integration by increasing the annual energy generation (AEG) to 337 GWh, lowering the LCOE to 9.24 ¢/kWh, and boosting the CF to 86%. The techno-economic optimization reveals the superiority of the LFR with substantial TES over solar-only systems, exhibiting a 300% increase in annual energy output and a 20% reduction in LCOE. Additionally, employing the FF backup system at 64% of the turbine’s rated capacity boosts AEG by 17%, accompanied by a 5% LCOE reduction. However, this enhancement comes with a trade-off, involving burning a substantial amount of natural gas (503,429 MMBtu), leading to greenhouse gas emissions totaling 14,185 tonnes CO₂ eq. This comprehensive analysis is a first-of-a-kind study and provides insights into the optimal designs of LFR power plants and addresses thermal, economic, and environmental considerations of utilizing molten salt with a large TES system as well as employing natural gas backup. The outcomes of the research address a wide audience including academics, operators, and policy makers. Full article
(This article belongs to the Collection Renewable Energy and Energy Storage Systems)
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21 pages, 4318 KiB  
Article
Impact of Using n-Octanol/Diesel Blends on the Performance and Emissions of a Direct-Injection Diesel Engine
by Jongkap Ahn, Kwonwoo Jang, Jeonghyeon Yang, Beomsoo Kim and Jaesung Kwon
Energies 2024, 17(11), 2691; https://doi.org/10.3390/en17112691 - 1 Jun 2024
Viewed by 240
Abstract
This study evaluates the viability of n-octanol as an alternative fuel in a direct-injection diesel engine, aiming to enhance sustainability and efficiency. Experiments fueled by different blends of n-octanol with pure diesel were conducted to analyze their impacts on engine performance and emissions. [...] Read more.
This study evaluates the viability of n-octanol as an alternative fuel in a direct-injection diesel engine, aiming to enhance sustainability and efficiency. Experiments fueled by different blends of n-octanol with pure diesel were conducted to analyze their impacts on engine performance and emissions. The methodology involved testing each blend in a single-cylinder engine, measuring engine performance parameters such as brake torque and brake power under full-load conditions across a range of engine speeds. Comparative assessments of performance and emission characteristics at a constant engine speed were also conducted with varying loads. The results indicated that while n-octanol blends consistently improved brake thermal efficiency, they also increased brake-specific fuel consumption due to the lower energy content of n-octanol. Consequently, while all n-octanol blends reduced nitrogen oxide emissions compared to pure diesel, they also significantly decreased carbon monoxide, hydrocarbons, and smoke opacity, presenting a comprehensive reduction in harmful emissions. However, the benefits came with complex trade-offs: notably, higher concentrations of n-octanol led to a relative increase in nitrogen oxide emissions as the n-octanol ratio increased. The study concludes that n-octanol significantly improves engine efficiency and reduces diesel dependence, but optimizing the blend ratio is crucial to balance performance improvements with comprehensive emission reductions. Full article
(This article belongs to the Special Issue Internal Combustion Engines for Carbon Neutrality: Performance, Combustion and Emission)
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19 pages, 4366 KiB  
Article
Performance Analysis and Optimization of Compressed Air Energy Storage Integrated with Latent Thermal Energy Storage
by Xiaoli Yu, Wenbo Dou, Zhiping Zhang, Yan Hong, Gao Qian and Zhi Li
Energies 2024, 17(11), 2608; https://doi.org/10.3390/en17112608 - 28 May 2024
Viewed by 357
Abstract
Recovering compression waste heat using latent thermal energy storage (LTES) is a promising method to enhance the round-trip efficiency of compressed air energy storage (CAES) systems. In this study, a systematic thermodynamic model coupled with a concentric diffusion heat transfer model of the [...] Read more.
Recovering compression waste heat using latent thermal energy storage (LTES) is a promising method to enhance the round-trip efficiency of compressed air energy storage (CAES) systems. In this study, a systematic thermodynamic model coupled with a concentric diffusion heat transfer model of the cylindrical packed-bed LTES is established for a CAES system, and the numerical simulation model is validated by experimental data in the reference. Based on the numerical model, the charging–discharging performance of LTES and CAES systems is evaluated under different layouts of phase change materials (PCMs) in LTES, and the optimal layout of PCM is specified as a three-stage layout, since the exergy efficiency of LTES and round-trip efficiency are improved by 8.2% and 6.9% compared with a one-stage layout. Then, the proportion of three PCMs is optimized using response surface methods. The optimization results indicate that the exergy efficiency of LTES and round-trip efficiency of the CAES system are expected to be 80.9% and 73.3% under the PCM proportion of 0.48:0.3:0.22 for three stages, which are 7.0% and 13.1% higher than the original three-stage PCMs with equal proportions. Full article
(This article belongs to the Special Issue Large-Scale Underground Energy Storage/Conversion Technologies Integrated with Renewable Energy Sources)
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24 pages, 9576 KiB  
Article
Standalone and Hybridised Flywheels for Frequency Response Services: A Techno-Economic Feasibility Study
by Andrew J. Hutchinson and Daniel T. Gladwin
Energies 2024, 17(11), 2577; https://doi.org/10.3390/en17112577 - 26 May 2024
Viewed by 436
Abstract
Frequency response services are one of the key components used by major electrical networks worldwide, acting to help control the frequency within set boundaries. Battery Energy Storage Systems (BESSs) are commonly deployed for this purpose; however, their potential is limited by susceptibility to [...] Read more.
Frequency response services are one of the key components used by major electrical networks worldwide, acting to help control the frequency within set boundaries. Battery Energy Storage Systems (BESSs) are commonly deployed for this purpose; however, their potential is limited by susceptibility to cycle-based degradation and widely reported safety incidents. Flywheel Energy Storage Systems (FESSs) do not share these weaknesses and hence could be a potential candidate for longer-term participation in frequency response markets. This study presents the most in-depth and wide-ranging techno-economic analysis of the feasibility of FESSs for frequency response to date. Standalone FESSs are shown to be economically viable across a range of different specifications, achieving a positive Net Present Value (NPV) under varying economic conditions. At a capital cost of 500 GBP/kW with a discount rate of 4%, a 5C FESS can achieve an NPV of GBP 38,586 as a standalone unit. The complex trade-offs when considering hybridising FESSs and BESSs for this application are also investigated in-depth for the first time, again showing positive changes to NPV under various scenarios. Conversely, under some conditions, hybridisation can have a significant negative impact, showcasing the optimisation needed when considering hybrid systems. The impact of introducing a hybrid BESS varies from a low of decreasing the NPV of the system by GBP 97,955 to a high of increasing the NPV by GBP 119,621 depending on the configuration chosen. This comprehensive work provides the foundations for future research into FESS deployment for frequency response services and shows for the first time the circumstances under which deployment for this application would be both technically and economically viable. Full article
(This article belongs to the Collection Renewable Energy and Energy Storage Systems)
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23 pages, 21208 KiB  
Article
Failure Characterization of Discrete SiC MOSFETs under Forward Power Cycling Test
by Tianqi Huang, Bhanu Pratap Singh, Yongqian Liu and Staffan Norrga
Energies 2024, 17(11), 2557; https://doi.org/10.3390/en17112557 - 24 May 2024
Viewed by 472
Abstract
Silicon carbide (SiC)-based metal–oxide–semiconductor field-effect transistors (MOSFETs) hold promising application prospects in future high-capacity high-power converters due to their excellent electrothermal characteristics. However, as nascent power electronic devices, their long-term operational reliability lacks sufficient field data. The power cycling test is an important [...] Read more.
Silicon carbide (SiC)-based metal–oxide–semiconductor field-effect transistors (MOSFETs) hold promising application prospects in future high-capacity high-power converters due to their excellent electrothermal characteristics. However, as nascent power electronic devices, their long-term operational reliability lacks sufficient field data. The power cycling test is an important experimental method to assess packaging-related reliability. In order to obtain data closest to actual working conditions, forward power cycling is utilized to carry out SiC MOSFET degradation experiments. Due to the wide bandgap characteristics of SiC MOSFETs, the short-term drift of the threshold voltage is much more serious than that of silicon (Si)-based devices. Therefore, an offline threshold voltage measurement circuit is implemented during power cycling tests to minimize errors arising from this short-term drift. Different characterizations are performed based on power cycling tests, focused on measuring the on-state resistance, thermal impedance, and threshold voltage of the devices. The findings reveal that the primary failure mode under forward power cycling tests, with a maximum junction temperature of 130 ∘C, is bond-wire degradation. Conversely, the solder layer and gate oxide exhibit minimal degradation tendencies under these conditions. Full article
(This article belongs to the Special Issue Design, Simulations, and Reliability of Power Converter)
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21 pages, 10163 KiB  
Article
Photovoltaic Manufacturing Factories and Industrial Site Environmental Impact Assessment
by Peter Brailovsky, Lorena Sanchez, Dilara Subasi, Jochen Rentsch, Ralf Preu and Sebastian Nold
Energies 2024, 17(11), 2540; https://doi.org/10.3390/en17112540 - 24 May 2024
Viewed by 524
Abstract
Life cycle inventories (LCIs) and life cycle assessments (LCAs) of photovoltaic (PV) modules and their components focus on the operations of PV factories, but the factories and industrial site product and construction stages are either not or only partially tackled. This work contributes [...] Read more.
Life cycle inventories (LCIs) and life cycle assessments (LCAs) of photovoltaic (PV) modules and their components focus on the operations of PV factories, but the factories and industrial site product and construction stages are either not or only partially tackled. This work contributes through the bottom-up, model-based generation of LCIs and LCAs for setting up a vertically integrated 5 GWp/a PV industrial site, including the manufacturing of silicon ingots, wafers, solar cells, and PV modules, on a 50 ha greenfield location. Two comparative LCAs are performed. The first compares the annualized environmental impacts of the developed LCI sets with four existing inventories in the Ecoinvent v3.8 database. The second comparative LCA explores the environmental impact differences concerning the industrial site when using different building systems for the factories. Here, the reference system with a steel structure is compared with two alternative building systems: precast concrete and structural timber. The results show that the wafer, cell, and module factories’ annualized environmental impacts with the Ecoinvent LCIs are strongly overestimated. For the ingot factory, the opposite result is identified. The impacts of all four factories show reductions of between 11.7% and 94.3% for 14 of the 15 impact categories. High mean environmental impact shares of 79.0%, 78.2% and 79.2% for the steel, precast concrete and timber structural building systems, respectively, are generated at the product stage. The process and facilities equipment generates 54.2%, 54.4% and 58.2% of the total product and construction stages’ mean environmental impact shares. The proposed alternative timber building system reduces the environmental impacts in 14 of the 15 evaluated categories, with reductions ranging from 1.1% to 12.4%. Full article
(This article belongs to the Special Issue Life Cycle Assessment in Renewable and Sustainable Energy)
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21 pages, 623 KiB  
Article
Global Conditions and Changes in the Level of Renewable Energy Sources
by Jolanta Latosińska, Dorota Miłek and Łukasz Gibowski
Energies 2024, 17(11), 2553; https://doi.org/10.3390/en17112553 - 24 May 2024
Viewed by 544
Abstract
The progressing globalization of the contemporary economy impacts its volatility and unpredictability. The directions of changes in the socioeconomic development of the contemporary global economy are determined by a number of interrelated diverse factors. Factors clearly influencing the development of the modern international [...] Read more.
The progressing globalization of the contemporary economy impacts its volatility and unpredictability. The directions of changes in the socioeconomic development of the contemporary global economy are determined by a number of interrelated diverse factors. Factors clearly influencing the development of the modern international economy include innovation, digitization processes, instability of the economy caused by armed conflicts or pandemic outbreaks, the concept of sustainable development, climate policy, as well as issues related to the depletion of energy resources and the necessity of ensuring global energy security. The purpose of the article is to identify the factors of the development of the contemporary economy along with the analysis and evaluation of their impacts on changes in the level of renewable energy sources (RESs) in the EU countries. The time scope of the analysis covers the years 2013 and 2022 (a 10-year perspective). The study used the methods of literature study, literature criticism, statistical data analysis (statistical databases: EUROSTAT and IRENA), and linear ordering methods (TOPSIS and EDAS). The study results indicate that the levels of the RESs have changed in response to the factors diagnosed in the study. In the years studied, the leaders in terms of levels of RES development were France, Spain, and Denmark. Full article
(This article belongs to the Collection Renewable Energy and Energy Storage Systems)
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28 pages, 3714 KiB  
Review
Review of Recent Applications of Heat Pipe Heat Exchanger Use for Waste Heat Recovery
by Yi Ding, Qiang Guo, Wenyuan Guo, Wenxiao Chu and Qiuwang Wang
Energies 2024, 17(11), 2504; https://doi.org/10.3390/en17112504 - 23 May 2024
Viewed by 422
Abstract
With the reduction in fossil fuels and growing concerns about global warming, energy has become one of the most important issues facing humanity. It is crucial to improve energy utilization efficiency and promote a low-carbon transition. In comparison with traditional heat exchangers, heat [...] Read more.
With the reduction in fossil fuels and growing concerns about global warming, energy has become one of the most important issues facing humanity. It is crucial to improve energy utilization efficiency and promote a low-carbon transition. In comparison with traditional heat exchangers, heat pipe heat exchangers indicate high compactness, a flexible arrangement, complete separation of hot and cold fluids, good isothermal operations, etc. As a result, heat pipe heat exchangers have attracted wide attention and application in various fields in recent years. This paper provides an overview of the application of heat pipe heat exchangers, with a focus on the application in waste heat recovery, and analyzes the opportunities and challenges of heat pipe heat exchanger applications based on existing publications. Full article
(This article belongs to the Section J: Thermal Management)
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21 pages, 8696 KiB  
Article
Dynamic Clustering of Wind Turbines Using SCADA Signal Analysis
by Pere Marti-Puig and Carles Núñez-Vilaplana
Energies 2024, 17(11), 2514; https://doi.org/10.3390/en17112514 - 23 May 2024
Viewed by 394
Abstract
This work explores the ability to dynamically group the Wind Turbine (WT) of a Wind Farm (WF) based on the behavior of some of their Supervisory Control And Data Acquisition (SCADA) signals to detect the turbines that exhibit abnormal behavior. This study is [...] Read more.
This work explores the ability to dynamically group the Wind Turbine (WT) of a Wind Farm (WF) based on the behavior of some of their Supervisory Control And Data Acquisition (SCADA) signals to detect the turbines that exhibit abnormal behavior. This study is centered on a small WF of five WTs and uses the observation that the same signals from different WTs in the same WF coherently evolve temporally in a time domain, describing very similar waveforms. In this contribution, averaged signals from the SCADA system are used and omit maximums, minimums and standard deviations, focusing mainly on velocities and other slowly varying signals. For the temporal analysis, sliding windows of different temporal durations are explored. The signals are encoded using the Discrete Cosine Transform, which reduces the problem’s dimensions. A hierarchical tree is built in each time window. Clusters are formed by pruning the tree using a threshold interpretable in terms of distance. It is unnecessary to work with an a priori known number of clusters. A protocol for enumerating the clusters based on the tree’s shape is then established, making it easier to follow the evolution of the clusters over time. The capability to automatically identify WTs whose signals differ from the group’s behavior can alert and program preventive maintenance operations on such WTs before a major breakdown occurs. Full article
(This article belongs to the Section A3: Wind, Wave and Tidal Energy)
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16 pages, 1760 KiB  
Article
Pollutant Emissions and Heavy Metal Migration in Co-Combustion of Sewage Sludge and Coal
by Chunyu Liu, Changtao Yue and Yue Ma
Energies 2024, 17(11), 2457; https://doi.org/10.3390/en17112457 - 21 May 2024
Viewed by 357
Abstract
The treatment of sewage sludge has become a global concern. Large amounts of sewage sludge can be disposed of by burning coal-mixed sludge. Thermogravimetric analysis and lab-scale combustion experiments in a drop tube furnace were utilized to study the combustion characteristics, pollutant emissions, [...] Read more.
The treatment of sewage sludge has become a global concern. Large amounts of sewage sludge can be disposed of by burning coal-mixed sludge. Thermogravimetric analysis and lab-scale combustion experiments in a drop tube furnace were utilized to study the combustion characteristics, pollutant emissions, and heavy metal migration during the co-combustion of coal and sewage sludge. The results showed that the blended fuels with a sewage sludge content less than 10 weight percent exhibited coal-like combustion characteristics. Additionally, the additional sewage sludge favored the ignition performance of blended fuels. When sewage sludge was added, the SO2 emissions rose to 76 mg/Nm3 under the 10% sludge condition—nearly three times higher than that of coal alone. While NOx emissions stayed mostly unchanged, HCl and HF emissions were very low. Meanwhile, Cr, Cu, and Ni migrated to the bottom ash, and their concentrations were all reduced with an increase in sewage sludge. Pb, Cd, Cr, Cu, Ni, and Hg migrated to the flue gas, mostly in the form of gaseous components. The results provide crucial information in the co-combustion of sewage sludge and coal, with implications in the development and improvement of large-scale, harmless, and resource-recovering techniques for waste sludge. Full article
(This article belongs to the Section B: Energy and Environment)
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29 pages, 11216 KiB  
Article
Using Quality Function Deployment to Assess the Efficiency of Mini-Channel Heat Exchangers
by Artur Piasecki, Sylwia Hożejowska, Aneta Masternak-Janus and Magdalena Piasecka
Energies 2024, 17(10), 2436; https://doi.org/10.3390/en17102436 - 20 May 2024
Viewed by 398
Abstract
This article addresses the design of a compact heat exchanger for the cooling of electronic systems. The Quality Function Deployment (QFD) method is used to identify crucial product features to improve device performance and key customer requirements. The QFD simplifies management processes, allowing [...] Read more.
This article addresses the design of a compact heat exchanger for the cooling of electronic systems. The Quality Function Deployment (QFD) method is used to identify crucial product features to improve device performance and key customer requirements. The QFD simplifies management processes, allowing modifications to device components, such as design parameters (dimensions and materials) and operating conditions (flow type and preferred temperature range). The study was applied to analyse the fundamental features of a compact heat exchanger, assessing their impact on enhancing heat transfer intensity during fluid flow through mini-channels. The thermal efficiency of the compact heat exchanger was tested experimentally. The results allow to verify the results obtained from the numerical simulations due to Simcenter STAR-CCM+. Consequently, the experimental part was reduced in favour of numerical simulations conducted using this commercial CFD software version 2020.2.1 Build 15.04.01. The numerical simulations performed with the aid of CFD showed increases in the heat transfer coefficient of up to 180% compared to the case treated as a reference. The application of the QFD matrix significantly reduces the time required to develop suitable design and material solutions and determine the operating parameters for the cooling of miniature electronic devices. Full article
(This article belongs to the Section J: Thermal Management)
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37 pages, 7263 KiB  
Article
Hot Bridge-Wire Ignition of Nanocomposite Aluminum Thermite Synthesized Using Sol-Gel-Derived Aerogel with Tailored Properties for Enhanced Reactivity and Reduced Sensitivity
by Ilyes Ghedjatti, Shiwei Yuan and Haixing Wang
Energies 2024, 17(10), 2437; https://doi.org/10.3390/en17102437 - 20 May 2024
Viewed by 539
Abstract
The development of nano-energetic materials has significantly advanced, leading to enhanced properties and novel applications in areas such as aerospace, defense, energy storage, and automobile. This research aims to engineer multi-dimensional nano-energetic material systems with precise control over energy release rates, spatial distribution, [...] Read more.
The development of nano-energetic materials has significantly advanced, leading to enhanced properties and novel applications in areas such as aerospace, defense, energy storage, and automobile. This research aims to engineer multi-dimensional nano-energetic material systems with precise control over energy release rates, spatial distribution, and temporal and pressure history. In this context, sol–gel processing has been explored for the manufacture of nanocomposite aluminum thermites using aerogels. The goal is to produce nano-thermites (Al/Fe2O3) with fast energy release rates that are insensitive to unintended initiation while demonstrating the potential of sol–gel-derived aerogels in terms of versatility, tailored properties, and compatibility. The findings provide insightful conclusions on the influence of factors such as secondary oxidizers (KClO3) and dispersants (n-hexane and acetone) on the reaction kinetics and the sensitivity, playing crucial roles in determining reactivity and combustion performance. In tandem, ignition systems contribute significantly in terms of a high degree of reliability and speed. However, the advantages of using nano-thermites combined with hot bridge-wire systems in terms of ignition and combustion efficiency for potential, practical applications are not well-documented in the literature. Thus, this research also highlights the practicality along with safety and simplicity of use, making nano-Al/Fe2O3-KClO3 in combination with hot bridge-wire ignition a suitable choice for experimental purposes and beyond. Full article
(This article belongs to the Special Issue Nanoparticles and Nanofluids for Energy Applications 2023)
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19 pages, 2976 KiB  
Article
Long-Term Energy System Modelling for a Clean Energy Transition in Egypt’s Energy Sector
by Anna Gibson, Zen Makuch, Rudolf Yeganyan, Naomi Tan, Carla Cannone and Mark Howells
Energies 2024, 17(10), 2397; https://doi.org/10.3390/en17102397 - 16 May 2024
Viewed by 536
Abstract
Egypt has the potential to generate a significant amount of energy from renewable technologies, in particular solar PV, concentrated solar power (CSP), and onshore and offshore wind. The energy sector is reliant on fossil fuels, particularly natural gas, for electricity production and is [...] Read more.
Egypt has the potential to generate a significant amount of energy from renewable technologies, in particular solar PV, concentrated solar power (CSP), and onshore and offshore wind. The energy sector is reliant on fossil fuels, particularly natural gas, for electricity production and is at risk of locking itself into a high carbon pathway. Globally, reducing greenhouse gas (GHG) emissions associated with national energy sectors is a target outlined in the UN’s Paris Agreement. To reduce carbon dioxide (CO2) emissions associated with a higher dependence on fossil fuels, Egypt must consider upscaling renewable energy technologies (RETs) to achieve a clean energy transition (CET). This research modelled six scenarios using clicSAND for OSeMOSYS to identify the technologies and policy target improvements that are needed to upscale RETs within Egypt’s energy sector. The results showed that solar PV and onshore wind are key technologies to be upscaled to contribute towards Egypt’s CET. The optimal renewable target is the International Renewable Energy Agency’s (IRENA) target of 53% of electricity being sourced from RETs by 2030, which will cost USD 16.4 billion more up to 2035 than Egypt’s current Integrated Sustainable Energy Strategy (ISES) target of 42% by 2035; it also saves 732.0 MtCO2 over the entire modelling period to 2070. Socio-economic barriers to this transition are considered, such as recent discoveries of natural gas reserves combined with a history of energy insecurity, political instability impacting investor confidence, and a lack of international climate funding. The paper concludes with policy recommendations that would enable Egypt to progress towards achieving a CET. Full article
(This article belongs to the Collection Energy Transition towards Carbon Neutrality)
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21 pages, 4200 KiB  
Article
Operative Benefits of Residential Battery Storage for Decarbonizing Energy Systems: A German Case Study
by Natapon Wanapinit, Nils Offermann, Connor Thelen, Christoph Kost and Christian Rehtanz
Energies 2024, 17(10), 2376; https://doi.org/10.3390/en17102376 - 15 May 2024
Viewed by 506
Abstract
The reduction in PV prices and interest in energy independence accelerate the adoption of residential battery storage. This storage can support various functions of an energy system undergoing decarbonization. In this work, operative benefits of storage from the system perspective, namely, generation cost [...] Read more.
The reduction in PV prices and interest in energy independence accelerate the adoption of residential battery storage. This storage can support various functions of an energy system undergoing decarbonization. In this work, operative benefits of storage from the system perspective, namely, generation cost reduction and congestion mitigation, are investigated. Germany is chosen as a case study due to its strong reliance on variable renewable energy. For the analysis, an economic dispatch model with a high spatial resolution is coupled with a pan-European transmission grid model. It is shown that the system’s generation costs are highest when the assets are used only to maximize PV self-consumption, and the costs are lowest when the storage also reacts to the market dynamics. This amounts to a 6% cost reduction. Both operation strategies result in an equal level of grid congestion and infrastructure loading. This is improved with a strategy that accounts for regional peak reduction as a secondary objective. The high congestion level emphasizes that grid expansion needs to keep pace with the generation and electrification expansion necessary to decarbonize other sectors. Lastly, policymakers should enable multipurpose utilization, e.g., via the introduction of market-oriented retail electricity prices with intervention options for grid operators. Full article
(This article belongs to the Section D: Energy Storage and Application)
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25 pages, 4840 KiB  
Article
Energy Management of Hydrogen Hybrid Electric Vehicles—Online-Capable Control
by David Machacek, Nazim Yasar, Fabio Widmer, Thomas Huber and Christopher Onder
Energies 2024, 17(10), 2369; https://doi.org/10.3390/en17102369 - 14 May 2024
Viewed by 616
Abstract
The results shown in this paper extend our research group’s previous work, which presents the theoretically achievable hydrogen engine-out NO​xeo (H​2-NO​xeo) Pareto front of a hydrogen hybrid electric vehicle (H​2-HEV). [...] Read more.
The results shown in this paper extend our research group’s previous work, which presents the theoretically achievable hydrogen engine-out NO​xeo (H​2-NO​xeo) Pareto front of a hydrogen hybrid electric vehicle (H​2-HEV). While the Pareto front is calculated offline, which requires significant computing power and time, this work presents an online-capable algorithm to tackle the energy management of a H​2-HEV with explicit consideration of the H​2-NO​xeo trade-off. Through the inclusion of realistic predictive data on the upcoming driving mission, a model predictive control algorithm (MPC) is utilized to effectively tackle the conflicting goal of achieving low hydrogen consumption while simultaneously minimizing NO​xeo. In a case study, it is shown that MPC is able to satisfy user-defined NO​xeo limits over the course of various driving missions. Moreover, a comparison with the optimal Pareto front highlights MPC’s ability to achieve close-to-optimal fuel performance for any desired cumulated NO​xeo target on four realistic routes for passenger cars. Full article
(This article belongs to the Special Issue Sustainable and Low Carbon Development in the Energy Sector)
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19 pages, 5028 KiB  
Article
Accuracy of Simscape Solar Cell Block for Modeling a Partially Shaded Photovoltaic Module
by Tihomir Betti, Ante Kristić, Ivan Marasović and Vesna Pekić
Energies 2024, 17(10), 2276; https://doi.org/10.3390/en17102276 - 9 May 2024
Viewed by 469
Abstract
With half-cut photovoltaic (PV) modules being the dominant technology on the market, there is an increasing necessity for accurate modeling of this module type. Circuit simulators such as Simulink are widely used to study different topics regarding photovoltaics, often employing a solar cell [...] Read more.
With half-cut photovoltaic (PV) modules being the dominant technology on the market, there is an increasing necessity for accurate modeling of this module type. Circuit simulators such as Simulink are widely used to study different topics regarding photovoltaics, often employing a solar cell block available from the Simcape library. The purpose of this work is to validate this model against measurements for a partially shaded half-cut PV module. Diverse shading scenarios are created by varying the number of shaded substrings, the number of shaded solar cells in the substring, and the shading level. For every shading scenario, the PV module’s I-V curve is measured, along with in-plane irradiance, air temperature, and module temperature. A comprehensive evaluation of simulation accuracy is presented. The results confirm a high accuracy of the model with mean nRMSE values of 2.2% for I-V curves and 2.8% when P-V curves are considered. It is found that the simulation errors tend to increase when increasing the number of shaded substrings. At the same time, no obvious dependency of simulation accuracy on the shading level or the number of shaded solar cells in the substring is found. Full article
(This article belongs to the Special Issue Advances in Solar Systems and Energy Efficiency)
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17 pages, 4226 KiB  
Article
Performance Analysis Based on Fuel Valve Train Control Optimization of Ammonia-Fuel Ships
by Lim Seungtaek, Lee Hosaeng and Seo Youngkyun
Energies 2024, 17(10), 2272; https://doi.org/10.3390/en17102272 - 8 May 2024
Viewed by 531
Abstract
In order to reduce carbon emissions, which are currently a problem in the shipping and offshore plant sectors, the international community is strengthening regulations such as the Energy Efficiency Design Index (EEDI) and Energy Efficiency Existing Ship Index (EEXI). To cope with this, [...] Read more.
In order to reduce carbon emissions, which are currently a problem in the shipping and offshore plant sectors, the international community is strengthening regulations such as the Energy Efficiency Design Index (EEDI) and Energy Efficiency Existing Ship Index (EEXI). To cope with this, eco-friendly fuel propulsion technology is being developed, and the development of an ammonia fuel supply system is in progress. Among them, fuel valve train (FVT) technology was researched for the final supply and cutoff of fuel and purging through nitrogen for ammonia engines. In this paper, we analyzed the change in ammonia supply due to FVT opening and the change in nitrogen supply due to closure. In addition, a plan to minimize risk factors was presented by applying a control method to remove residual fuel in FVT. According to the presented FVT model, the difference in the flow rate of supplied fuel was as much as 17.8 kg/s. Additionally, by opening the gas bleed valve at intervals during the closing process and purging about 0.28 kg of nitrogen, the internal fuel could be completely discharged. This is expected to have an impact on improving the marine environment through the application of eco-friendly fuels and the development of fuel supply system technology. Full article
(This article belongs to the Special Issue Advances in Fuel Energy)
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23 pages, 10457 KiB  
Article
Small-Scale Battery Energy Storage System for Testing Algorithms Aimed at Peak Power Reduction
by Krzysztof Sozański, Szymon Wermiński and Jacek Kaniewski
Energies 2024, 17(9), 2217; https://doi.org/10.3390/en17092217 - 4 May 2024
Viewed by 835
Abstract
This study describes a laboratory model of a battery energy storage system (BESS) designed for testing algorithms aimed at reducing peak power consumption in railway traction substations. The system comprises a DC/DC converter and battery energy storage. This article details a laboratory model [...] Read more.
This study describes a laboratory model of a battery energy storage system (BESS) designed for testing algorithms aimed at reducing peak power consumption in railway traction substations. The system comprises a DC/DC converter and battery energy storage. This article details a laboratory model of a bidirectional buck-boost DC/DC converter, which is used to transfer energy between the battery energy storage and a DC line. It presents an analysis of DC/DC converter systems along with simulation studies. Furthermore, the results of laboratory tests on the DC/DC converter model are also provided. The control algorithm of the system in the traction substation is focused on reducing peak power, offering benefits such as lower charges for the railway operator due to the possibility of reducing contracted power requirements. From the perspective of the power grid, the reduction in power fluctuations and, consequently, voltage sags, is advantageous. This paper includes a description of a hardware simulator for verifying the system’s control algorithms. The verification of the control algorithms was performed through experimental tests conducted on a laboratory model (a hardware simulator) of the system for dynamic load reduction in traction substations, on a power scale of 1:1000 (5.5 kW). The experimental tests on the laboratory model (hardware simulator) demonstrated the effectiveness of the algorithm in reducing the peak power drawn from the power source. Full article
(This article belongs to the Collection Featured Papers in Electrical Power and Energy System)
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25 pages, 4301 KiB  
Review
Review of Fuel-Cell Electric Vehicles
by Tingke Fang, Coleman Vairin, Annette von Jouanne, Emmanuel Agamloh and Alex Yokochi
Energies 2024, 17(9), 2160; https://doi.org/10.3390/en17092160 - 30 Apr 2024
Cited by 2 | Viewed by 1043
Abstract
This paper presents an overview of the status and future prospects of fuel-cell electric vehicles (FC-EVs). As global concerns about emissions escalate, FC-EVs have emerged as a promising substitute for traditional internal combustion engine vehicles. This paper discusses the fundamentals of fuel-cell technology [...] Read more.
This paper presents an overview of the status and future prospects of fuel-cell electric vehicles (FC-EVs). As global concerns about emissions escalate, FC-EVs have emerged as a promising substitute for traditional internal combustion engine vehicles. This paper discusses the fundamentals of fuel-cell technology considering the major types of fuel cells that have been researched and delves into the most suitable fuel cells for FC-EV applications, including comparisons with mainstream vehicle technologies. The present state of FC-EVs, ongoing research, and the challenges and opportunities that need to be accounted for are discussed. Furthermore, the comparison between promising proton-exchange membrane fuel cell (PEMFC) and solid oxide fuel cell (SOFC) technologies used in EVs provides valuable insights into their respective strengths and challenges. By synthesizing these aspects, the paper aims to provide a comprehensive understanding and facilitate decision-making for future advancements in sustainable FC-EV transportation, thereby contributing to the realization of a cleaner, greener, and more environmentally friendly future. Full article
(This article belongs to the Section E: Electric Vehicles)
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16 pages, 3009 KiB  
Article
Assessment and Forecasting of Energy Efficiency in Economic Sectors in Poland
by Joanna Żurakowska-Sawa and Mariusz Pyra
Energies 2024, 17(9), 2128; https://doi.org/10.3390/en17092128 - 29 Apr 2024
Viewed by 511
Abstract
The material developed focuses on the analysis of energy efficiency trends in Poland, utilising ODEX indicators for the sectors of industry, transport, households and in general, from 2011 to 2021. The objective of the study is to assess the progress made in energy [...] Read more.
The material developed focuses on the analysis of energy efficiency trends in Poland, utilising ODEX indicators for the sectors of industry, transport, households and in general, from 2011 to 2021. The objective of the study is to assess the progress made in energy efficiency and to forecast future trends in these sectors. The methods employed are based on statistical modelling of time series, taking into account sector-specific energy consumption dynamics. The following techniques were employed: linear regression, cluster analysis to identify patterns of change, statistical hypothesis testing for energy efficiency and simplified autoregressive models. The results demonstrated significant improvements in energy efficiency in the industrial sector, stability of the ODEX indicator in the transport sector and gradual improvements in households and overall. The prediction indicates an upward trend in the ODEX indicator in the short term, suggesting an increase in energy demand. However, it also predicts a decline in the long term, which may indicate the effectiveness of future energy efficiency strategies and investments. Consequently, the necessity for continued efforts to increase energy efficiency and further research into the factors influencing energy efficiency in different economic sectors is emphasised. Full article
(This article belongs to the Section A: Sustainable Energy)
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33 pages, 16459 KiB  
Article
Elevational Earth-Sheltered Buildings with Horizontal Overhang Photovoltaic-Integrated Panels—New Energy-Plus Building Concept in the Territory of Serbia
by Aleksandar Nešović, Robert Kowalik, Milan Bojović, Agata Janaszek and Stanisław Adamczak
Energies 2024, 17(9), 2100; https://doi.org/10.3390/en17092100 - 27 Apr 2024
Viewed by 686
Abstract
The global scientific community is intensively promoting energy-plus buildings. Following the leading world trends, this paper presents a new energy-plus building concept—elevational earth-sheltered buildings with three different types of horizontal overhang photovoltaic-integrated panels: wooden support columns covered with clay tiles, steel pipes as [...] Read more.
The global scientific community is intensively promoting energy-plus buildings. Following the leading world trends, this paper presents a new energy-plus building concept—elevational earth-sheltered buildings with three different types of horizontal overhang photovoltaic-integrated panels: wooden support columns covered with clay tiles, steel pipes as support columns covered with sheet steel, and concrete support columns with concrete coverage. In this instance, the specific multi-numerical case study building model for the city of Kragujevac (located in central Serbia with favorable climatic conditions) was performed over 7 months (from 1 October to 30 April), taking into account the soil temperature, the effects of solar shading, the performance of the heating system—a ground source heat pump—and the characteristics of the artificial and automatic lighting control system. The simulation results show that the optimal depth of a horizontal overhang (energy-plus status) depends on the occupant’s habits, in addition to meteorological conditions. The presented methodology can be used for any other location, both in Europe and the world. Full article
(This article belongs to the Special Issue Energy Efficiency of the Buildings III)
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31 pages, 5856 KiB  
Article
Proposal and Study of a Pumped Thermal Energy Storage to Improve the Economic Results of a Concentrated Solar Power That Works with a Hybrid Rankine–Brayton Propane Cycle
by Antonio Jesús Subires, Antonio Rovira and Marta Muñoz
Energies 2024, 17(9), 2005; https://doi.org/10.3390/en17092005 - 24 Apr 2024
Viewed by 561
Abstract
This work proposes a pumped thermal energy storage (PTES) integrated into the power block of a concentrated solar power plant. The power block operates under a Hybrid Rankine–Brayton (HRB) cycle using propane as the working fluid. During PTES charging, some thermal energy is [...] Read more.
This work proposes a pumped thermal energy storage (PTES) integrated into the power block of a concentrated solar power plant. The power block operates under a Hybrid Rankine–Brayton (HRB) cycle using propane as the working fluid. During PTES charging, some thermal energy is obtained from a dedicated compressor (additional to that of the HRB cycle), which is stored. During discharge, both compressors (HRB and PTES) are off, restoring the consumed energy and resulting in about a 13% increase in nominal power output. The system is also able to store thermal energy that would otherwise be rejected through the condenser if the PTES were turned off, leading to efficiency improvements in some cases. Considering the 2022 Spanish electricity market prices, the proposed PTES integration with 4 h of storage is feasible. The levelized cost of storage is calculated and compared to those of other PTES systems, achieving around a 40% reduction compared with an equivalent PTES Rankine. These results encourage future studies where the proposed PTES could be integrated into other power cycles that include a recompression process. Full article
(This article belongs to the Collection Renewable Energy and Energy Storage Systems)
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21 pages, 3893 KiB  
Article
Solution for Post-Mining Sites: Thermo-Economic Analysis of a Large-Scale Integrated Energy Storage System
by Jakub Ochmann, Michał Jurczyk, Krzysztof Rusin, Sebastian Rulik, Łukasz Bartela and Wojciech Uchman
Energies 2024, 17(8), 1970; https://doi.org/10.3390/en17081970 - 21 Apr 2024
Viewed by 672
Abstract
The intensive development of renewable energy sources and the decreasing efficiency of conventional energy sources are reducing the flexibility of the electric power system. It becomes necessary to develop energy storage systems that allow reducing the differences between generation and energy demand. This [...] Read more.
The intensive development of renewable energy sources and the decreasing efficiency of conventional energy sources are reducing the flexibility of the electric power system. It becomes necessary to develop energy storage systems that allow reducing the differences between generation and energy demand. This article presents a multivariant analysis of an adiabatic compressed air energy storage system. The system uses a post-mining shaft as a reservoir of compressed air and also as a location for the development of a heat storage tank. Consideration was given to the length of the discharge stage, which directly affects the capital expenditure and operating schedule of the system. The basis for the analyses was the in-house numerical model, which takes into account the variability of air parameters during system operation. The numerical model also includes calculations of Thermal Energy Storage’s transient performance. The energy efficiency of the system operating on a daily cycle varies from 67.9% to 70.3%. Various mechanisms for economic support of energy storage systems were analyzed. The levelized cost of storage varies, depending on the variant, from 75.86 EUR/MWh for the most favorable case to 223.24 EUR/MWh for the least favorable case. Full article
(This article belongs to the Collection Renewable Energy and Energy Storage Systems)
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17 pages, 1058 KiB  
Article
Anaerobic Digestion as a Possible Method of Managing Waste from Mushroom Production with Sewage Sludge as Co-Substrate
by Katarzyna Bernat, Thi Cam Tu Le, Dorota Kulikowska and Ram Thapa
Energies 2024, 17(8), 1938; https://doi.org/10.3390/en17081938 - 18 Apr 2024
Viewed by 718
Abstract
The mushroom agroindustry generates a huge amount of waste from mushroom production (WMP). The composition of WMP is not standardized but differs mainly in terms of organic matter (OM) content and OM biodegradability. This makes WMP management, including anaerobic digestion (AD), a significant [...] Read more.
The mushroom agroindustry generates a huge amount of waste from mushroom production (WMP). The composition of WMP is not standardized but differs mainly in terms of organic matter (OM) content and OM biodegradability. This makes WMP management, including anaerobic digestion (AD), a significant challenge. A potential solution could be co-digestion of WMP with municipal sewage sludge (SS), especially SS generated in small rural wastewater treatment plants (WWTPs). Therefore, this study investigated mesophilic methane production (MP) from WMP, SS, and mixtures of SS and WMP at ratios of 70:30, 50:50, and 30:70 (w/w OM). Even though the maximum cumulative MP from WMP was relatively low (approx. 60 NL/kg OM), co-digesting WMP with SS increased both MP and the methane content of the biogas: with 30%, 50%, and 70% shares of SS, MP increased almost 2, 2.5, and 3.3 times, and the methane content increased to 61%, 62%, and 64%, respectively. As the SS content was increased, the kinetic coefficients of MP and OM removal decreased (from 0.211 to 0.146 d−1 and from 0.215 to 0.152 d−1), whereas the initial rate of MP and of OM removal increased (from 12.5 to 36.8 NL/(kg OM·d) and from 0.51 kg OM/(m3·d) to 0.59 kg OM/(m3·d), respectively). The effectiveness of OM removal (EOMrem) was lowest with WMP only, at 46.6%. When the SS content of the mixtures was increased to 30%, 50%, and 70%, EOMrem also increased to 55.3%, 60.1%, and 64.9%, respectively. The relationship between maximal MP and the overall OM removed was such that both increased simultaneously. The higher values of EOMrem and, consequently, the lower final contents of OM with more effective MP indicate that the organics were degraded more efficiently. These results suggest that co-digestion may be a profitable solution for simultaneously utilizing both of these waste products, increasing the efficiency of biogas production to such an extent that it would be profitable to conduct AD on mushroom farms. This is a flexible approach that allows varying proportions of WMP and SS to be used, depending on the availability of both substrates and the energy needs of the mushroom farm. However, it should be borne in mind that a higher share of WMP results in lower gas productivity. Full article
(This article belongs to the Special Issue Biomass and Bio-Energy—2nd Edition)
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30 pages, 4051 KiB  
Article
Integrated Black Oil Modeling for Efficient Simulation and Optimization of Carbon Storage in Saline Aquifers
by Ismail Ismail, Sofianos Panagiotis Fotias, Dimitris Avgoulas and Vassilis Gaganis
Energies 2024, 17(8), 1914; https://doi.org/10.3390/en17081914 - 17 Apr 2024
Viewed by 720
Abstract
Carbon capture and storage technologies play a crucial role in mitigating climate change by capturing and storing carbon dioxide emissions underground. Saline aquifers, among other geological formations, hold promise for long-term CO2 storage. However, accurately assessing their storage capacity and CO2 [...] Read more.
Carbon capture and storage technologies play a crucial role in mitigating climate change by capturing and storing carbon dioxide emissions underground. Saline aquifers, among other geological formations, hold promise for long-term CO2 storage. However, accurately assessing their storage capacity and CO2 behavior underground necessitates advanced numerical simulation and modeling techniques. In this study, we introduce an approach based on a solubility thermodynamic model that leverages cubic equations of state offline from the simulator. This approach enables the precise prediction of CO2–brine equilibrium properties and facilitates the conversion of compositional data into black oil PVT data suitable for black oil simulations. By incorporating industry-scale saline aquifer properties, we simulate a carbon storage scheme using the black oil model technique, significantly reducing computation time by at least four times while preserving the essential physical phenomena observed in underground carbon storage operations. A comparative analysis between black oil and compositional simulations reveals consistent results for reservoir pressure, CO2 saturation distributions, and mass fraction of trapping mechanisms, with differences of less than 4%. This validation underscores the reliability and efficiency of integrating the black oil model technique into carbon storage simulations in saline aquifer formations, offering tangible benefits to industry operators and regulators by striking a balance between accuracy and efficiency. The capability of this approach to extend to temperatures of up to 300 °C and pressures of up to 600 bars broadens its applicability beyond conventional CCS applications, serving as a valuable tool for optimizing decision-making processes in CCS projects, particularly in scenarios where profitability may be marginal. Full article
(This article belongs to the Collection Feature Papers in Carbon Capture, Utilization, and Storage)
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13 pages, 2848 KiB  
Article
Radiated Electromagnetic Emission from Photovoltaic Systems—Measurement Results: Inverters and Modules
by Désirée Kroner, Urban Lundgren, André Augusto and Math Bollen
Energies 2024, 17(8), 1893; https://doi.org/10.3390/en17081893 - 16 Apr 2024
Viewed by 750
Abstract
Radiated electromagnetic emission of photovoltaic systems, for example, adversely impacting radiocommunication, can pose a major barrier against further increase in photovoltaic penetration. This is particularly the case near sensitive infrastructure and activities such as hospitals, airports, search and rescue, and military. To understand [...] Read more.
Radiated electromagnetic emission of photovoltaic systems, for example, adversely impacting radiocommunication, can pose a major barrier against further increase in photovoltaic penetration. This is particularly the case near sensitive infrastructure and activities such as hospitals, airports, search and rescue, and military. To understand the impact of each component and installation detail, we performed systematic radiated electromagnetic emission measurements on comparable commercial photovoltaic systems in the frequency range 150 kHz to 30 MHz. Our measurements indicate that string inverters are unlikely to interfere with radiocommunication when installed according to recommended standards, rules, guidelines, and regulations. It was shown that module-level power optimizers are the main cause of high levels of radiated emissions. The frameless bifacial module showed higher levels of radiated emissions than the monofacial module with frame. Changes in cable management and earthing have less impact on radiated emissions than the choice of solar inverter concept and module type. Full article
(This article belongs to the Section A: Sustainable Energy)
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22 pages, 3873 KiB  
Article
Artificial Intelligence-Centric Low-Enthalpy Geothermal Field Development Planning
by Torsten Clemens, Maria-Magdalena Chiotoroiu, Anthony Corso, Markus Zechner and Mykel J. Kochenderfer
Energies 2024, 17(8), 1887; https://doi.org/10.3390/en17081887 - 16 Apr 2024
Viewed by 582
Abstract
Low-enthalpy geothermal energy can make a major contribution towards reducing CO2 emissions. However, the development of geothermal reservoirs is costly and time intensive. In particular, high capital expenditures, data acquisition costs, and long periods of time from identifying a geothermal resource to [...] Read more.
Low-enthalpy geothermal energy can make a major contribution towards reducing CO2 emissions. However, the development of geothermal reservoirs is costly and time intensive. In particular, high capital expenditures, data acquisition costs, and long periods of time from identifying a geothermal resource to geothermal heat extraction make geothermal field developments challenging. Conventional geothermal field development planning follows a linear approach starting with numerical model calibrations of the existing subsurface data, simulations of forecasts for geothermal heat production, and cost estimations. Next, data acquisition actions are evaluated and performed, and then the models are changed by integrating the new data before being finally used for forecasting and economics. There are several challenges when using this approach and the duration of model rebuilding with the availability of new data is time consuming. Furthermore, the approach does not address sequential decision making under uncertainty as it focuses on individual data acquisition actions. An artificial intelligence (AI)-centric approach to field development planning substantially improves cycle times and the expected rewards from geothermal projects. The reason for this is that various methods such as machine learning in data conditioning and distance-based generalized sensitivity analysis assess the uncertainty and quantify its potential impact on the final value. The use of AI for sequential decision making under uncertainty results in an optimized data acquisition strategy, a recommendation of a specific development scenario, or advice against further investment. This approach is illustrated by applying AI-centric geothermal field development planning to an Austrian low-enthalpy geothermal case. The results show an increase in the expected value of over 27% and a reduction in data acquisition costs by more than 35% when compared with conventional field development planning strategies. Furthermore, the results are used in systematic trade-off assessments of various key performance indicators. Full article
(This article belongs to the Section H2: Geothermal)
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14 pages, 585 KiB  
Article
Assessing Energy Potential and Chemical Composition of Food Waste Thermodynamic Conversion Products: A Literature Review
by Andreja Škorjanc, Darko Goričanec and Danijela Urbancl
Energies 2024, 17(8), 1897; https://doi.org/10.3390/en17081897 - 16 Apr 2024
Viewed by 593
Abstract
This study examines the considerable volume of food waste generated annually in Slovenia, which amounted to over 143,000 tons in 2020. The analysis shows that 40% of food waste consists of edible parts, highlighting the potential for reduction through increased consumer awareness and [...] Read more.
This study examines the considerable volume of food waste generated annually in Slovenia, which amounted to over 143,000 tons in 2020. The analysis shows that 40% of food waste consists of edible parts, highlighting the potential for reduction through increased consumer awareness and attitudes towards food consumption. The study shows that the consumption phase contributes the most to waste food (46%), followed by primary production (25%) and processing/manufacture (24%). The study addresses various thermodynamic processes, in particular, thermal conversion methods, such as torrefaction pyrolysis and hydrothermal carbonization, which optimize energy potential by reducing the atomic ratio (H/C) and (O/C), thereby increasing calorific value and facilitating the production of solid fuels. The main results show the effectiveness of torrefaction, pyrolysis and hydrothermal carbonization (HTC) in increasing the energy potential of food waste. Full article
(This article belongs to the Special Issue Sustainable Energy Development in Liquid Waste and Biomass)
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16 pages, 454 KiB  
Article
Approach to Design of Piezoelectric Energy Harvester for Sensors on Electric Machine Rotors
by Lukas Brandl, Hans-Christian Reuss and Daniel Heidle
Energies 2024, 17(8), 1884; https://doi.org/10.3390/en17081884 - 15 Apr 2024
Viewed by 551
Abstract
The reliability and efficiency of components are key aspects in the automotive industry. Electric machines become the focus of development. Thus, improvements in efficiency and reliability have gained significance. While it is established to attach sensors to the fixed parts of machines, such [...] Read more.
The reliability and efficiency of components are key aspects in the automotive industry. Electric machines become the focus of development. Thus, improvements in efficiency and reliability have gained significance. While it is established to attach sensors to the fixed parts of machines, such as stators, moving parts like rotors pose a major challenge due to the power supply. Piezoelectric generators can operate as energy harvesters on rotors and thus enable the rotor-based integration of sensors. The research in this article proposes the first approach to the design of a piezoelectric energy harvester (PEH) for an electric machine rotor dedicated to powering a wireless sensor system. After introducing the field of PEHs, the integration of the proposed device on a rotor shaft is presented. Further, a gap between the provided and needed data for the design of a PEH is identified. To overcome this gap, a method is presented, starting with the definition of the rotor shaft dimensions and the applied mechanical loads, including a method for the calculation of the imbalance of the rotor. With the first set of dimensions of the shaft and PEH, a co-simulation is performed to calculate the power output of this rotor and PEH set. The results of the simulation indicate the feasible implementation of the PEH on the rotor, providing enough energy to power a temperature sensor. Full article
(This article belongs to the Special Issue Energy Harvesting and Storage for Microsystems)
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15 pages, 1899 KiB  
Article
Determination of Kinetic and Thermodynamic Parameters of Biomass Gasification with TG-FTIR and Regression Model Fitting
by Viktória Zsinka, Bálint Levente Tarcsay and Norbert Miskolczi
Energies 2024, 17(8), 1875; https://doi.org/10.3390/en17081875 - 15 Apr 2024
Viewed by 626
Abstract
In this study, the decomposition of five different raw materials (maize, wheat and piney biomass, industrial wood chips and sunflower husk) were investigated using the TG-FTIR method to obtain raw data for model-based calculations. The data obtained from the thermogravimetric analysis served as [...] Read more.
In this study, the decomposition of five different raw materials (maize, wheat and piney biomass, industrial wood chips and sunflower husk) were investigated using the TG-FTIR method to obtain raw data for model-based calculations. The data obtained from the thermogravimetric analysis served as a basis for kinetic analysis with three different isoconversional, model-free methods, which were the KAS, FWO and Friedman methods. Afterwards, the activation energy and the pre-exponential factor were determined, and no significant difference could be identified among the used methods (difference was under 5%), achieving 203–270 kJ/mol of Ea on average. Thereafter, the thermodynamic parameters were studied. Based on the TG-FTIR data, a logistic regression model was fitted to the data, which gives information about the thermal degradation and the obtained components with different heating rates. The FTIR analysis resulted in differential peaks corresponding to the studied components that were detected within the temperature range of 350–380 °C. The primary degradation processes occurred within a broader temperature range of 200–600 °C. Accordingly, in this work, the use of logistic mixture models as an alternative to traditional kinetic models for the description of the TGA process was also investigated, reaching adequate performance in fitting by a validation data coefficient of determination of R2 = 0.9988. Full article
(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)
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26 pages, 3558 KiB  
Article
Residual Biomass Gasification for Small-Scale Decentralized Electricity Production: Business Models for Lower Societal Costs
by Laurene Desclaux and Amaro Olimpio Pereira, Jr.
Energies 2024, 17(8), 1868; https://doi.org/10.3390/en17081868 - 13 Apr 2024
Viewed by 669
Abstract
Biomass gasification, a promising sustainable technology for decentralized electricity production, has the potential to displace fossil fuels while valorizing locally produced waste. Previous studies indicate that its technical and financial viabilities vary among projects, and few projects have been successfully developed, despite the [...] Read more.
Biomass gasification, a promising sustainable technology for decentralized electricity production, has the potential to displace fossil fuels while valorizing locally produced waste. Previous studies indicate that its technical and financial viabilities vary among projects, and few projects have been successfully developed, despite the sustainability benefits. This study identified and characterized the factors that influence the economic and environmental performances of such projects using a novel, hybrid method, with qualitative analysis using the Business Model Canvas and quantitative life-cycle costs (LCCs) considering the financial and external costs. The financial LCCs and external electricity generation costs were evaluated for business models in agro-industrial factories using proprietary residual biomasses and for those in isolated grids using local agricultural waste. The business models used for biomass gasification projects affect their LCCs and externalities more than factors such as their investment costs and energy efficiencies. The relationship between the business models, the financial performances of the projects, and their impacts on society are highlighted, showing that although projects using proprietary biomass waste have lower financial costs, off-grid projects generate more positive externalities, resulting in lower costs for society. These results indicate that policy support focused on appropriate business models may contribute to optimizing the use of financial incentives to foster investment in new sustainable technologies, contributing to the energy transition. Full article
(This article belongs to the Special Issue Energy Economics: Global Trends in Technology and Policy)
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17 pages, 10921 KiB  
Article
The Impact of Aluminosilicate Additives upon the Chlorine Distribution and Melting Behavior of Poultry Litter Ash
by Izabella Maj, Kamil Niesporek, Krzysztof Matus, Francesco Miccio, Mauro Mazzocchi and Paweł Łój
Energies 2024, 17(8), 1854; https://doi.org/10.3390/en17081854 - 12 Apr 2024
Viewed by 660
Abstract
The use of poultry litter (PL) as a sustainable fuel is gaining more attention due to its wide availability and carbon neutrality. However, this type of feedstock is rich in ash and typically contains a high concentration of chlorine (Cl) and alkali elements [...] Read more.
The use of poultry litter (PL) as a sustainable fuel is gaining more attention due to its wide availability and carbon neutrality. However, this type of feedstock is rich in ash and typically contains a high concentration of chlorine (Cl) and alkali elements (Na, K). Therefore, it is likely to cause unwanted issues during combustion and co-combustion, such as chlorine-induced corrosion, ash deposition, and bed agglomeration. In this study, for the first time, the influence of aluminosilicate additives on the above problems of poultry litter was investigated. Three aluminosilicate minerals are under consideration: kaolin, halloysite, and bentonite. Their influence on the chemical composition and meting tendencies of two poultry litter ashes are determined. The investigated ashes, PL1 and PL2, are characterized by different chlorine contents of 6.38% and 0.42%, respectively. The results show that in the case of the chlorine-rich PL1 ash, the additives reduced the chlorine content by up to 45%, resulting in a 3.93% of chlorine in the case of halloysite, 3.48% in the case of kaolin, and 4.25% in the case of bentonite. The additives also positively influenced the shrinkage starting temperature and the deformation temperature of the PL1 ash. Full article
(This article belongs to the Special Issue Sustainable Energy Development in Liquid Waste and Biomass)
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39 pages, 18434 KiB  
Article
Current Controller Design of Grid-Connected Inverter with Incomplete Observation Considering L-/LC-Type Grid Impedance
by Sung-Dong Kim, Thuy Vi Tran, Seung-Jin Yoon and Kyeong-Hwa Kim
Energies 2024, 17(8), 1855; https://doi.org/10.3390/en17081855 - 12 Apr 2024
Cited by 3 | Viewed by 518
Abstract
This paper presents a current control design for stabilizing an inductive-capacitive-inductive (LCL)-filtered grid-connected inverter (GCI) system under uncertain grid impedance and distorted grid environment. To deal with the negative impact of grid impedance, LC-type grid impedance is considered in both the system model [...] Read more.
This paper presents a current control design for stabilizing an inductive-capacitive-inductive (LCL)-filtered grid-connected inverter (GCI) system under uncertain grid impedance and distorted grid environment. To deal with the negative impact of grid impedance, LC-type grid impedance is considered in both the system model derivation and controller design process of an LCL-filtered GCI system. In addition, the integral and resonant control terms are also augmented into the system model in the synchronous reference frame to guarantee the reference tracking of zero steady-state error and good harmonic disturbance compensation of the grid-injected currents from GCI. By considering the effect of grid impedance on the control design process, an incomplete state feedback controller will be designed based on the linear-quadratic regulator (LQR) without damaging the asymptotic stabilization and robustness of the GCI system under uncertain grid impedance. By means of the closed-loop pole map evaluation, the asymptotic stability, robustness, and resonance-damping capability of the proposed current control scheme are confirmed even when all the system states are not available. In order to reduce the number of required sensors for the realization of the controller, a discrete-time current-type full-state observer is employed in this paper to estimate the system state variables with high precision. The feasibility and effectiveness of the proposed control scheme are demonstrated by the PSIM simulations and experiments by using a three-phase GCI prototype system under adverse grid conditions. The comprehensive evaluation results show that the designed control scheme maintains the stability and robustness of the LCL-filtered GCI when connecting to unexpected grids, such as harmonic distortion and L-type and LC-type grid impedances. As a result, the proposed control scheme successfully stabilizes the entire GCI system with high-quality grid-injected currents even when the GCI faces severe grid distortions and an extra grid dynamic caused by the L-type or LC-type grid impedance. Furthermore, low-order distortion harmonics come from the background grid voltages and are maintained as acceptable limits according to the IEEE Std. 1547-2003. Comparative test result with the conventional one also confirms the effectiveness of the proposed control scheme under LC-type grid impedance thanks to the consideration of LC grid impedance in the design process. Full article
(This article belongs to the Special Issue New Insights into Distributed Energy Systems)
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23 pages, 7716 KiB  
Article
Design of Three Electric Vehicle Charging Tariff Systems to Improve Photovoltaic Self-Consumption
by Garazi Etxegarai, Haritza Camblong, Aitzol Ezeiza and Tek Tjing Lie
Energies 2024, 17(8), 1806; https://doi.org/10.3390/en17081806 - 9 Apr 2024
Viewed by 621
Abstract
Electric vehicles (EVs) are emerging as one of the pillars for achieving climate neutrality. They represent both a threat and an opportunity for the operation of the network. Used as flexible loads, they can favor the self-consumption of photovoltaic (PV) energy. This paper [...] Read more.
Electric vehicles (EVs) are emerging as one of the pillars for achieving climate neutrality. They represent both a threat and an opportunity for the operation of the network. Used as flexible loads, they can favor the self-consumption of photovoltaic (PV) energy. This paper presents three EV charging tariff systems (TSs) based on the self-consumption of excess PV energy. The TS objectives are to increase the self-consumption rate (SCR) and thus indirectly decrease the charging cost of the EV users. Two of the proposed TSs correspond to an indirect control of EV charging. The third TS is a hybrid system where the charging power is controlled. The TS is designed using a series of rules that consider the momentary PV surplus and the charging power of each EV. The influence of the TS is simulated by considering real data from a PV collective self-consumption project in the Basque Country (Spain). The TS simulations performed with 6 months of data show a 13.1% increase in the SCR when applying the third TS, reaching an average of 93.09% for the SCR. In addition, the cost of EV charging is reduced by 25%. Full article
(This article belongs to the Special Issue Electric Vehicles for Smart Cities: Trends, Challenges and Opportunities)
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16 pages, 5316 KiB  
Article
Optimization Operation Strategy for Shared Energy Storage and Regional Integrated Energy Systems Based on Multi-Level Game
by Yulong Yang, Tao Chen, Han Yan, Jiaqi Wang, Zhongwen Yan and Weiyang Liu
Energies 2024, 17(7), 1770; https://doi.org/10.3390/en17071770 - 8 Apr 2024
Viewed by 633
Abstract
Regional Integrated Energy Systems (RIESs) and Shared Energy Storage Systems (SESSs) have significant advantages in improving energy utilization efficiency. However, establishing a coordinated optimization strategy between RIESs and SESSs is an urgent problem to be solved. This paper constructs an operational framework for [...] Read more.
Regional Integrated Energy Systems (RIESs) and Shared Energy Storage Systems (SESSs) have significant advantages in improving energy utilization efficiency. However, establishing a coordinated optimization strategy between RIESs and SESSs is an urgent problem to be solved. This paper constructs an operational framework for RIESs considering the participation of SESSs. It analyzes the game relationships between various entities based on the dual role of energy storage stations as both energy consumers and suppliers, and it establishes optimization models for each stakeholder. Finally, the improved Differential Evolution Algorithm (JADE) combined with the Gurobi solver is employed on the MATLAB 2021a platform to solve the cases, verifying that the proposed strategy can enhance the investment willingness of energy storage developers, balance the interests among the Integrated Energy Operator (IEO), Energy Storage Operator (ESO) and the user, and improve the overall economic efficiency of RIESs. Full article
(This article belongs to the Topic Advances in Power Science and Technology)
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20 pages, 7165 KiB  
Article
Thermodynamic Analysis of a Cogeneration System Combined with Heat, Cold, and Electricity Based on the Supercritical CO2 Power Cycle
by Rujun Zhang, Xiaohe Wang, Shuang Yang and Xin Shen
Energies 2024, 17(7), 1767; https://doi.org/10.3390/en17071767 - 8 Apr 2024
Viewed by 641
Abstract
The supercritical CO2 power cycle driven by solar as a new generation of solar thermal power generation technology has drawn significant attention worldwide. In this paper, a cogeneration system derived from a supercritical CO2 recompression Brayton cycle is proposed, by considering [...] Read more.
The supercritical CO2 power cycle driven by solar as a new generation of solar thermal power generation technology has drawn significant attention worldwide. In this paper, a cogeneration system derived from a supercritical CO2 recompression Brayton cycle is proposed, by considering the recovery of waste heat from the turbine outlet. The absorption refrigeration cycle is powered by the medium-temperature waste heat from the turbine outlet, while the low-temperature waste heat is employed for heating, achieving the cascaded utilization of the heat from the turbine outlet. As for the proposed combined cooling, heating, and power (CCHP) system, a dynamic model was built and verified in MATLAB R2021b/Simulink. Under design conditions, values for the energy utilization factor (EUF) and exergy efficiency of the cogeneration system were obtained. Moreover, the thermodynamic performances of the system were investigated in variable cooling/heating load and irradiation conditions. Compared with the reference system, it is indicated that the energy utilization factor (EUF) and exergy efficiency are 84.7% and 64.8%, which are improved by 11.5% and 10.3%. The proposed supercritical CO2 CCHP system offers an effective solution for the efficient utilization of solar energy. Full article
(This article belongs to the Special Issue Advances in Solar Systems and Energy Efficiency)
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20 pages, 7192 KiB  
Article
Advanced Flame front Detection in Combustion Processes Using Autoencoder Approach
by Federico Ricci and Francesco Mariani
Energies 2024, 17(7), 1759; https://doi.org/10.3390/en17071759 - 6 Apr 2024
Viewed by 726
Abstract
This research explores the detection of flame front evolution in spark-ignition engines using an innovative neural network, the autoencoder. High-speed camera images from an optical access engine were analyzed under different air excess coefficient λ conditions to evaluate the autoencoder’s performance. This study [...] Read more.
This research explores the detection of flame front evolution in spark-ignition engines using an innovative neural network, the autoencoder. High-speed camera images from an optical access engine were analyzed under different air excess coefficient λ conditions to evaluate the autoencoder’s performance. This study compared this new approach (AE) with an established method used by the same research group (BR) across multiple combustion cycles. Results revealed that the AE method outperformed the BR in accurately identifying flame pixels and significantly reducing overestimations outside the flame boundary. AE exhibited higher sensitivity levels, indicating its superior ability to identify pixels and minimize errors compared to the BR method. Additionally, AE’s accuracy in representing combustion evolution was notably improved, offering a more detailed depiction of the process. AE’s strength lies in its independence from specific threshold searches, a requirement in the BR method. By relying on learned representations within its latent space, AE eliminates laborious threshold exploration, ensuring reliability and reducing workload pressures. Comparative analyses consistently confirmed AE’s superior performance in accurately reproducing and delineating combustion evolution compared to BR. This study highlights AE’s potential as a promising technique for precise flame front detection in combustion processes. Its ability to autonomously extract features, minimize errors, and enhance overall accuracy signifies a significant step forward in analyzing flame fronts. AE’s reliability, reduced need for manual intervention, and adaptability across various conditions suggest a promising future for improving combustion analysis techniques in spark-ignition engines with optical access. Full article
(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)
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21 pages, 4213 KiB  
Article
Possibilities of Utilising Biomass Collected from Road Verges to Produce Biogas and Biodiesel
by Robert Czubaszek, Agnieszka Wysocka-Czubaszek, Aneta Sienkiewicz, Alicja Piotrowska-Niczyporuk, Martin J. Wassen and Andrzej Bajguz
Energies 2024, 17(7), 1751; https://doi.org/10.3390/en17071751 - 5 Apr 2024
Viewed by 927
Abstract
Grass collected as part of roadside maintenance is conventionally subjected to composting, which has the disadvantage of generating significant CO2 emissions. Thus, it is crucial to find an alternative method for the utilisation of grass waste. The aim of this study was [...] Read more.
Grass collected as part of roadside maintenance is conventionally subjected to composting, which has the disadvantage of generating significant CO2 emissions. Thus, it is crucial to find an alternative method for the utilisation of grass waste. The aim of this study was to determine the specific biogas yield (SBY) from the anaerobic mono-digestion of grass from road verges and to assess the content of Fatty Acid Methyl Esters (FAMEs) in grass in relation to the time of cutting and the preservation method of the studied material. The biochemical biogas potential (BBP) test and the FAMEs content were performed on fresh and ensiled grass collected in spring, summer, and autumn. The highest biogas production was obtained from fresh grass cut in spring (715.05 ± 26.43 NL kgVS−1), while the minimum SBY was observed for fresh grass cut in summer (540.19 ± 24.32 NL kgVS−1). The methane (CH4) content in the biogas ranged between 55.0 ± 2.0% and 60.0 ± 1.0%. The contents of ammonia (NH3) and hydrogen sulphide (H2S) in biogas remained below the threshold values for these inhibitors. The highest level of total FAMEs was determined in fresh grass cut in autumn (98.08 ± 19.25 mg gDM−1), while the lowest level was detected in fresh grass cut in spring (56.37 ± 7.03 mg gDM−1). C16:0 and C18:0, which are ideal for biofuel production, were present in the largest amount (66.87 ± 15.56 mg gDM−1) in fresh grass cut in autumn. The ensiling process significantly impacted the content of total FAMEs in spring grass, leading to a reduction in total saturated fatty acids (SFAs) and an increase in total unsaturated fatty acids (USFAs). We conclude that grass biomass collected during the maintenance of road verges is a valuable feedstock for the production of both liquid and gaseous biofuels; however, generating energy from biogas appears to be more efficient than producing biodiesel. Full article
(This article belongs to the Special Issue Sustainable Energy Development in Liquid Waste and Biomass)
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12 pages, 3601 KiB  
Article
Biohydrogen Production and Quantitative Determination of Monosaccharide Production Using Hyperthermophilic Anaerobic Fermentation of Corn Stover
by Parveen Fatemeh Rupani, Ruben Sakrabani, Beenish Sadaqat and Weilan Shao
Energies 2024, 17(7), 1734; https://doi.org/10.3390/en17071734 - 4 Apr 2024
Viewed by 658
Abstract
Second-generation biofuels from lignocellulosic biomass remain critical and require several challenges due to lignin compounds’ inefficient degradation and recalcitrate characteristics. In this regard, this study focuses on enzymatic technology as a promising treatment that is beneficial in breaking down the biomass’s hemicellulose and [...] Read more.
Second-generation biofuels from lignocellulosic biomass remain critical and require several challenges due to lignin compounds’ inefficient degradation and recalcitrate characteristics. In this regard, this study focuses on enzymatic technology as a promising treatment that is beneficial in breaking down the biomass’s hemicellulose and cellulosic parts. Thermostable bacterial species owe thermostable enzymes that are able to degrade complex carbohydrate compounds and produce efficient hydrogen production. The present study investigates the direct utilization of ligninolytic enzymes such as cellulase and xylanase derived from the hyperthermophilic bacteria Thermotoga maritima (ATCC 43589 strain). The results show that xylanase and cellulase enzymes extracted from Thermotoga maritima could depolymerize the lignin bonds of corn stover substrate and release monomers such as Galactose in the media. In conclusion, this study can open a new advanced research window on directly applying a hyperthermophilic consortium of enzymes capable of hydrolyzing lignocellulose material toward hydrogen production. Full article
(This article belongs to the Special Issue The Significance of Agro-Waste in Second-Generation Biofuels towards Circular Bioeconomy)
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29 pages, 12691 KiB  
Article
Insights from a Comprehensive Capacity Expansion Planning Modeling on the Operation and Value of Hydropower Plants under High Renewable Penetrations
by Evangelos S. Chatzistylianos, Georgios N. Psarros and Stavros A. Papathanassiou
Energies 2024, 17(7), 1723; https://doi.org/10.3390/en17071723 - 3 Apr 2024
Cited by 2 | Viewed by 635
Abstract
This paper presents a quantitative assessment of the value of hydroelectric power plants (HPPs) in power systems with a significant penetration of variable renewable energy sources (VRESs). Through a capacity expansion planning (CEP) model that incorporates a detailed representation of HPP operating principles, [...] Read more.
This paper presents a quantitative assessment of the value of hydroelectric power plants (HPPs) in power systems with a significant penetration of variable renewable energy sources (VRESs). Through a capacity expansion planning (CEP) model that incorporates a detailed representation of HPP operating principles, the study investigates the construction and application of HPP rule curves essential for seasonal operation. A comparative analysis is also conducted between the proposed rule curve formulation and alternative modeling techniques from the literature. The CEP model optimizes installed capacities per technology to achieve predefined VRES penetration targets, considering hourly granularity and separate rule curves for each HPP. A case study involving twelve reservoir hydropower stations and two open-loop pumped hydro stations is examined, accounting for standalone plants and cascaded hydro systems across six river basins. The study evaluates the additional generation and storage required to replace the hydropower fleet under high VRES penetration levels, assessing the resulting increases in total system cost emanating from introducing such new investments. Furthermore, the study approximates the storage capabilities of HPPs and investigates the impact of simplified HPP modeling on system operation and investment decisions. Overall, the findings underscore the importance of reevaluating hydro rule curves for future high VRES penetration conditions and highlight the significance of HPPs in the energy transition towards carbon neutrality. Full article
(This article belongs to the Special Issue Energy, Electrical and Power Engineering 2024)
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13 pages, 2228 KiB  
Article
Thermodynamic Feasibility Evaluation of Alkaline Thermal Treatment Process for Hydrogen Production and Carbon Capture from Biomass by Process Modeling
by Yujung Jung and Sanghun Lee
Energies 2024, 17(7), 1661; https://doi.org/10.3390/en17071661 - 30 Mar 2024
Viewed by 726
Abstract
Hydrogen is attracting attention as a low-carbon fuel. In particular, economical hydrogen production technologies without carbon emissions are gaining increasing attention. Recently, alkaline thermal treatment (ATT) has been proposed to reduce carbon emissions by capturing carbon in its solid phase during hydrogen production. [...] Read more.
Hydrogen is attracting attention as a low-carbon fuel. In particular, economical hydrogen production technologies without carbon emissions are gaining increasing attention. Recently, alkaline thermal treatment (ATT) has been proposed to reduce carbon emissions by capturing carbon in its solid phase during hydrogen production. By adding an alkali catalyst to the conventional thermochemical hydrogen production reaction, ATT enables carbon capture through the reaction of an alkali catalyst and carbon. In this study, a thermodynamic feasibility evaluation was carried out, and the effects of the process conditions for ATT with wheat straw grass (WSG) as biomass were investigated using Aspen Plus software V12.1. First, an ATT process model was developed, and basic thermodynamic equilibrium compositions were obtained in various conditions. Then, the effects of the process parameters of the reactor temperature and the mass ratio of NaOH/WSG (alkali/biomass, A/B value) were analyzed. Finally, the product gas compositions, process efficiency, and amount of carbon capture were evaluated. The results showed that the ATT process could be an efficient hydrogen production process with carbon capture, and the optimal process conditions were a reactor temperature of 800 °C, an A/B value of three, and a flow rate of steam of 6.9 × 10−5 L/min. Under these conditions, the maximum efficiency and the amount of carbon dioxide captured were 56.9% and 28.41 mmol/g WSG, respectively. Full article
(This article belongs to the Collection Feature Papers in Carbon Capture, Utilization, and Storage)
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16 pages, 20102 KiB  
Article
Joint Estimation of SOC and SOH for Lithium-Ion Batteries Based on Dual Adaptive Central Difference H-Infinity Filter
by Bingyu Sang, Zaijun Wu, Bo Yang, Junjie Wei and Youhong Wan
Energies 2024, 17(7), 1640; https://doi.org/10.3390/en17071640 - 29 Mar 2024
Viewed by 812
Abstract
The accurate estimation of the state-of-charge (SOC) and state-of-health (SOH) of lithium-ion batteries is crucial for the safe and reliable operation of battery systems. In order to overcome the practical problems of low accuracy, slow convergence and insufficient robustness in the existing joint [...] Read more.
The accurate estimation of the state-of-charge (SOC) and state-of-health (SOH) of lithium-ion batteries is crucial for the safe and reliable operation of battery systems. In order to overcome the practical problems of low accuracy, slow convergence and insufficient robustness in the existing joint estimation algorithms of SOC and SOH, a Dual Adaptive Central Difference H-Infinity Filter algorithm is proposed. Firstly, the Forgetting Factor Recursive Least Squares (FFRLS) algorithm is employed for parameter identification, and an inner loop with multiple updates of the parameter estimation vector is added to improve the accuracy of parameter identification. Secondly, the capacity is selected as the characterization of SOH, and the open circuit voltage and capacity are used as the state variables for capacity estimation to improve its convergence speed. Meanwhile, considering the interaction between SOC and SOH, the state space equations of SOC and SOH estimation are established. Moreover, the proposed algorithm introduces a robust discrete H-infinity filter equation to improve the measurement update on the basis of the central differential Kalman filter with good accuracy, and combines the Sage–Husa adaptive filter to achieve the joint estimation of SOC and SOH. Finally, under Urban Dynamometer Driving Schedule (UDDS) and Highway Fuel Economy Test (HWFET) conditions, the SOC estimation errors are 0.5% and 0.63%, and the SOH maximum estimation errors are 0.73% and 0.86%, indicating that the proposed algorithm has higher accuracy compared to the traditional algorithm. The experimental results at different initial values of capacity and SOC demonstrate that the proposed algorithm showcases enhanced convergence speed and robustness. Full article
(This article belongs to the Collection Renewable Energy and Energy Storage Systems)
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25 pages, 4578 KiB  
Article
A Dependability Neural Network Approach for Short-Term Production Estimation of a Wind Power Plant
by Fabio Famoso, Ludovica Maria Oliveri, Sebastian Brusca and Ferdinando Chiacchio
Energies 2024, 17(7), 1627; https://doi.org/10.3390/en17071627 - 28 Mar 2024
Cited by 1 | Viewed by 559
Abstract
This paper presents a novel approach to estimating short-term production of wind farms, which are made up of numerous turbine generators. It harnesses the power of big data through a blend of data-driven and model-based methods. Specifically, it combines an Artificial Neural Network [...] Read more.
This paper presents a novel approach to estimating short-term production of wind farms, which are made up of numerous turbine generators. It harnesses the power of big data through a blend of data-driven and model-based methods. Specifically, it combines an Artificial Neural Network (ANN) for immediate future predictions of wind turbine power output with a stochastic model for dependability, using Hybrid Reliability Block Diagrams. A thorough state-of-the-art review has been conducted in order to demonstrate the applicability of an ANN for non-linear stochastic problems of energy or power forecast estimation. The study leverages an innovative cluster analysis to group wind turbines and reduce the computational effort of the ANN, with a dependability model that improves the accuracy of the data-driven output estimation. Therefore, the main novelty is the employment of a hybrid model that combines an ANN with a dependability stochastic model that accounts for the realistic operational scenarios of wind turbines, including their susceptibility to random shutdowns This approach marks a significant advancement in the field, introducing a methodology which can aid the design and the power production forecast. The research has been applied to a case study of a 24 MW wind farm located in the south of Italy, characterized by 28 turbines. The findings demonstrate that the integrated model significantly enhances short-term wind-energy production estimation, achieving a 480% improvement in accuracy over the solo-clustering approach. Full article
(This article belongs to the Special Issue Volume Ⅱ: Advances in Wind and Solar Farm Forecasting)
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15 pages, 1254 KiB  
Review
Unlocking Geothermal Energy: A Thorough Literature Review of Lithuanian Geothermal Complexes and Their Production Potential
by Abdul Rashid Memon, Pijus Makauskas, Ieva Kaminskaite-Baranauskiene and Mayur Pal
Energies 2024, 17(7), 1576; https://doi.org/10.3390/en17071576 - 26 Mar 2024
Viewed by 621
Abstract
Lithuania is located on the East of Baltic sedimentary basin and has a geothermal anomaly situated in the southwestern region of the country. There are two primary geothermal complexes within the anomaly, composed of Cambrian and Devonian aquifers. The Cambrian formation is composed [...] Read more.
Lithuania is located on the East of Baltic sedimentary basin and has a geothermal anomaly situated in the southwestern region of the country. There are two primary geothermal complexes within the anomaly, composed of Cambrian and Devonian aquifers. The Cambrian formation is composed of sandstones that have a reservoir temperature reaching up to 96 °C (depth > 2000 m). The Devonian aquifer is composed of unconsolidated sands of Parnu–Kemeri and has a reservoir temperature of up to 46 °C (depth > 1000 m). Historically, both formations have been investigated for geothermal energy production. In this article, we present a detailed literature review of the geothermal work carried out on both formations, including past, present, and some possible future studies. The study presented in this paper highlights the key findings of previous research work, summarizes the research gaps, and then elaborates on the possible applications of emerging technologies to bridge the research gaps and improve our understanding of geothermal complexes in Lithuania. Although it is not the main aim of this article, this article also touches upon the important need to develop 2D/3D numerical models, to quantify uncertainties, in the evaluation of the geothermal potential in Lithuania for commercial development. This study also highlights possibilities of extending geothermal development to depleted hydrocarbon reservoirs through repurposing the high-water-production wells. Moreover, from the literature review, it can be concluded that the Lithuanian geothermal aquifers are hyper-saline in nature and temperature changes lead to the deposition of salts both upstream and downstream of the reservoir. Therefore, there is a need for developing multiphysics thermo-mechanical–chemical (THMC) models for evaluation of reservoir behavior. The literature also describes the potential use and development of the THMC model as a part of future work that must be carried out. Full article
(This article belongs to the Collection Renewable Energy and Energy Storage Systems)
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