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Energies, Volume 16, Issue 7 (April-1 2023) – 364 articles

Cover Story (view full-size image): Methane and methanol are promising products for carbon capture and utilization concepts through CO2 hydrogenation. In the search for effective, robust, easy-to-manufacture and stable catalysts, supported metal-based catalysts have been proven to be advantageous. Whilst nickel for methane synthesis and copper for methanol synthesis stand out as efficient and cost-effective catalytically active metals, the best choice of a support material is still a matter of ongoing debate. This review discusses the potential of the alkaline earth metal oxide MgO as a support material for CO2 hydrogenation catalysts. Due to its basicity, it gives access to bifunctional catalysts by showing a pronounced CO2 adsorption capacity. Whilst carbonate formation seems to be beneficial in CO2 methanation, it may have an adverse effect during methanol synthesis from CO2View this paper
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19 pages, 2830 KiB  
Article
Application of the Calcium Looping Process for Thermochemical Storage of Variable Energy
by Kelly Atkinson, Robin Hughes and Arturo Macchi
Energies 2023, 16(7), 3299; https://doi.org/10.3390/en16073299 - 6 Apr 2023
Cited by 3 | Viewed by 1606
Abstract
The calcium looping (CaL) process, which exploits the reversible calcination of calcium carbonate, has been proposed as a solution to the challenges facing deployment of concentrated solar power (CSP). As an extension of the work undertaken to date, this project proposes a novel [...] Read more.
The calcium looping (CaL) process, which exploits the reversible calcination of calcium carbonate, has been proposed as a solution to the challenges facing deployment of concentrated solar power (CSP). As an extension of the work undertaken to date, this project proposes a novel configuration of the CSP-CaL process which may offer advantages over other proposed configurations, including a reduction in process equipment requirements, elimination of pressure differentials between vessels, and a reduction in compression duty during the energy discharge period. The results obtained through process simulation indicate that the proposed process can achieve round-trip efficiencies in the range of 32–46% and energy storage densities in the range of 0.3–1.0 GJ/m3. These parameters are strongly dependent on the residual conversion of the CaO sorbent as well as the efficiency of the power cycles used to remove heat on the carbonator side of the process. Full article
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29 pages, 5280 KiB  
Review
An Assessment of Energy Flexibility Solutions from the Perspective of Low-Tech
by Muhammad Salman Shahid, Seun Osonuga, Nana Kofi Twum-Duah, Sacha Hodencq, Benoit Delinchant and Frédéric Wurtz
Energies 2023, 16(7), 3298; https://doi.org/10.3390/en16073298 - 6 Apr 2023
Viewed by 2554
Abstract
The energy transition is a multidisciplinary challenge that warrants solutions that are robust and sustainable. Energy flexibility, one of the key pillars of the energy transition, is an umbrella term that covers multiple innovative solutions implemented at all levels of the electric grid [...] Read more.
The energy transition is a multidisciplinary challenge that warrants solutions that are robust and sustainable. Energy flexibility, one of the key pillars of the energy transition, is an umbrella term that covers multiple innovative solutions implemented at all levels of the electric grid to ensure power quality standards, amongst other objectives. Low-tech, on the other hand, emphasizes designing, producing, and sustainably implementing solutions. Therefore, considering the multidisciplinary nature of energy transition and the existing energy flexibility solutions, the purpose of this research work is multilateral: first, it presents the concept of low-tech and its associated mechanisms; then, it addresses the misconceptions and similarities that low-tech might have with other innovation approaches; and finally, it provides an assessment of existing flexibility solutions using low-tech as a tool. The result of this assessment is presented qualitatively and indicates that indirect energy flexibility solutions rank higher on a low-tech scale relative to supply-side energy flexibility solutions and energy storage flexibility solutions. Full article
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10 pages, 2837 KiB  
Article
On the Summarization of Meteorological Data for Solar Thermal Power Generation Forecast
by Icaro Figueiredo Vilasboas, Julio Augusto Mendes da Silva and Osvaldo José Venturini
Energies 2023, 16(7), 3297; https://doi.org/10.3390/en16073297 - 6 Apr 2023
Cited by 1 | Viewed by 1263
Abstract
The establishment of the typical weather conditions of a given locality is of fundamental importance to determine the optimal configurations for solar thermal power plants and to calculate feasibility indicators in the power plant design phase. Therefore, this work proposes a summarization method [...] Read more.
The establishment of the typical weather conditions of a given locality is of fundamental importance to determine the optimal configurations for solar thermal power plants and to calculate feasibility indicators in the power plant design phase. Therefore, this work proposes a summarization method to statistically represent historical weather data using typical meteorological days (TMDs) based on the cumulative distribution function (CDF) and hourly normalized root mean square difference (nRMSD). The proposed approach is compared with regular Sandia selection in forecasting the electricity produced by a solar thermal power plant in ten different Brazilian cities. Considering the determination of the annual generation of electricity, the results obtained show that when considering an overall average of weather characteristics, commonly used for analyzing solar thermal power plant designs, the normalized mean average error (nMAE) is 20.8 ± 4.8% relative to the use of historical data of 20 years established at hourly intervals. On the other hand, a typical meteorological year (TMY) is the most accurate approach (nMAE = 1.0 ± 1.1%), but the costliest in computational time (CT = 381.6 ± 56.3 s). Some TMD cases, in turn, present a reasonable trade-off between computational time and accuracy. The case using 4 TMD, for example, increased the error by about 11 percentual points while the computational time was reduced by about 81 times, which is quite significant for the simulation and optimization of complex heliothermic systems. Full article
(This article belongs to the Section A2: Solar Energy and Photovoltaic Systems)
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17 pages, 1865 KiB  
Article
In Situ Biogas Upgrading in a Randomly Packed Gas-Stirred Tank Reactor (GSTR)
by Giuseppe Lembo, Silvia Rosa, Antonella Marone and Antonella Signorini
Energies 2023, 16(7), 3296; https://doi.org/10.3390/en16073296 - 6 Apr 2023
Cited by 2 | Viewed by 1158
Abstract
This study evaluated different strategies to increase gas–liquid mass transfer in a randomly packed gas stirred tank reactor (GSTR) continuously fed with second cheese whey (SCW), at thermophilic condition (55 °C), for the purpose of carrying out in situ biogas upgrading. Two different [...] Read more.
This study evaluated different strategies to increase gas–liquid mass transfer in a randomly packed gas stirred tank reactor (GSTR) continuously fed with second cheese whey (SCW), at thermophilic condition (55 °C), for the purpose of carrying out in situ biogas upgrading. Two different H2 addition rates (1.18 and 1.47 LH2 LR−1 d−1) and three different biogas recirculation rates (118, 176 and 235 L LR−1 d−1) were applied. The higher recirculation rate showed the best upgrading performance; H2 utilization efficiency averaged 88%, and the CH4 concentration in biogas increased from 49.3% during conventional anaerobic digestion to 75%, with a methane evolution rate of 0.37 LCH4 LR−1 d−1. The microbial community samples were collected at the end of each experimental phase, as well as one of the thermophilic sludge used as inoculum; metanogenomic analysis was performed using Illumina-based 16S sequencing. The whole microbial community composition was kept quite stable throughout the conventional anaerobic digestion (AD) and during the H2 addition experimental phases (UP1, UP2, UP3, UP4). On the contrary, the methanogens community was deeply modified by the addition of H2 to the GSTR. Methanogens of the Methanoculleus genus progressively increased in UP1 (47%) and UP2 (51%) until they became dominant in UP3 (94%) and UP4 (77%). At the same time, members of Methanotermobacter genus decreased to 19%, 23%, 3% and 10% in UP1, UP2, UP3 and UP4, respectively. In addition, members of the Methanosarcina genus decreased during the hydrogen addition phases. Full article
(This article belongs to the Special Issue Biological Processes in the Green Hydrogen Value Chain)
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15 pages, 10490 KiB  
Article
Prediction Error-Based Power Forecasting of Wind Energy System Using Hybrid WT–ROPSO–NARMAX Model
by Aamer A. Shah, Almani A. Aftab, Xueshan Han, Mazhar Hussain Baloch, Mohamed Shaik Honnurvali and Sohaib Tahir Chauhdary
Energies 2023, 16(7), 3295; https://doi.org/10.3390/en16073295 - 6 Apr 2023
Viewed by 1223
Abstract
The volatility and intermittency of wind energy result in highly unpredictable wind power output, which poses challenges to the stability of the intact power system when integrating large-scale wind power. The accuracy of wind power prediction is critical for maximizing the utilization of [...] Read more.
The volatility and intermittency of wind energy result in highly unpredictable wind power output, which poses challenges to the stability of the intact power system when integrating large-scale wind power. The accuracy of wind power prediction is critical for maximizing the utilization of wind energy, improving the quality of power supply, and maintaining the stable operation of the power grid. To address this challenge, this paper proposes a novel hybrid forecasting model, referred to as Hybrid WT–PSO–NARMAX, which combines wavelet transform, randomness operator-based particle swarm optimization (ROPSO), and non-linear autoregressive moving average with external inputs (NARMAX). The model is specifically designed for power generation forecasting in wind energy systems, and it incorporates the interactions between the wind system’s supervisory control and data acquisition’s (SCADA) actual power record and numerical weather prediction (NWP) meteorological data for one year. In the proposed model, wavelet transform is utilized to significantly improve the quality of the chaotic meteorological and SCADA data. The NARMAX techniques are used to map the non-linear relationship between the NWP meteorological variables and SCADA wind power. ROPSO is then employed to optimize the parameters of NARMAX to achieve higher forecasting accuracy. The performance of the proposed model is compared with other forecasting strategies, and it outperforms in terms of forecasting accuracy improvement. Additionally, the proposed Prediction Error-Based Power Forecasting (PEBF) approach is introduced, which retrains the model to update the results whenever the difference between forecasted and actual wind powers exceeds a certain limit. The efficiency of the developed scheme is evaluated through a real case study involving a 180 MW grid-connected wind energy system located in Shenyang, China. The proposed model’s forecasting accuracy is evaluated using various assessment metrics, including mean absolute error (MAE) and root mean square error (RMSE), with the average values of MAE and RMSE being 0.27% and 0.30%, respectively. The simulation and numerical results demonstrated that the proposed model accurately predicts wind output power. Full article
(This article belongs to the Special Issue Advanced Artificial Intelligence Application for Power Systems)
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15 pages, 4496 KiB  
Article
Impact of Static Air-Gap Eccentricity Fault on Synchronous Generator Efficiency
by Yu-Ling He, Ling Tang, Kai Sun, Wen-Hao Zhang, Xue-Wei Wu and Hai-Peng Wang
Energies 2023, 16(7), 3294; https://doi.org/10.3390/en16073294 - 6 Apr 2023
Viewed by 1093
Abstract
This paper presents a precise analysis of the efficiency characteristic of the synchronous generator under both normal and SAGE conditions. In this work, various losses of the synchronous generator are computed by the qualitative theoretical model and the finite element analysis in detail. [...] Read more.
This paper presents a precise analysis of the efficiency characteristic of the synchronous generator under both normal and SAGE conditions. In this work, various losses of the synchronous generator are computed by the qualitative theoretical model and the finite element analysis in detail. Further, the generator efficiency model is proposed according to the relationship between the output power and the loss. The presented model is verified in a 5-kW non-salient synchronous generator. The result demonstrates that the loss increases and the efficiency reduce as the SAGE intensifies. Full article
(This article belongs to the Section F3: Power Electronics)
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19 pages, 1983 KiB  
Article
Research and Optimization of Hybrid On-Board Energy Storage System of an Electric Locomotive for Quarry Rail Transport
by Sergey Goolak, Liliia Kondratieva, Ievgen Riabov, Vaidas Lukoševičius, Artūras Keršys and Rolandas Makaras
Energies 2023, 16(7), 3293; https://doi.org/10.3390/en16073293 - 6 Apr 2023
Cited by 4 | Viewed by 1646
Abstract
Operation modes of rolling stock at mining enterprises are considered and analyzed. The justification of the need to replace it with a modern specialized electric locomotive for quarry railway transport, equipped with an asynchronous traction electric drive and an on-board energy storage system, [...] Read more.
Operation modes of rolling stock at mining enterprises are considered and analyzed. The justification of the need to replace it with a modern specialized electric locomotive for quarry railway transport, equipped with an asynchronous traction electric drive and an on-board energy storage system, is presented. The determination of the parameters and structure of the on-board energy storage system, based on the condition of power compensation with limited power consumption from the traction network and ensuring the autonomous movement of the electric locomotive, is considered. This study was carried out by modeling the processes of energy exchange in the traction system of an electric locomotive. The use of lithium cells and supercapacitors in energy storage is considered. Variants of the hybridization of energy storage were studied from the standpoint of minimizing the weight, size, and cost indicators. It was established that reducing the mass of the energy storage device, which includes lithium cells and supercapacitors, leads to an increase in the cost of one kilowatt-hour of energy storage capacity, which reduces the attractiveness of capital expenditures for the creation of such an energy storage device. Hybridization of the energy storage device by combining lithium cells of different types practically does not improve its weight, size, and cost indicators. The recommended option is a storage capacity of energy based on LTO elements, for which it is necessary to select elements in order to minimize weight, size, and cost indicators. Full article
(This article belongs to the Special Issue Forecasting and Optimization in Transport Energy Management Systems)
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23 pages, 331 KiB  
Article
Financial, Economic, and Environmental Analyses of Upgrading Reverse Osmosis Plant Fed with Treated Wastewater
by Foroogh Nazari Chamaki, Glenn P. Jenkins and Majid Hashemipour
Energies 2023, 16(7), 3292; https://doi.org/10.3390/en16073292 - 6 Apr 2023
Viewed by 1382
Abstract
One of the most effective strategies to mitigate water shortages worldwide is to reuse treated wastewater for freshwater production employing reverse osmosis (RO) technology. This strategy is appropriate in urban areas of arid or semi-arid regions as it can provide a sustainable and [...] Read more.
One of the most effective strategies to mitigate water shortages worldwide is to reuse treated wastewater for freshwater production employing reverse osmosis (RO) technology. This strategy is appropriate in urban areas of arid or semi-arid regions as it can provide a sustainable and reliable water source close to the consumers. One of the drawbacks of RO is the high variability of production costs due to the electricity intensity. In addition, depending on the electricity source, it can also result in substantial environmental costs. This study showed that upgrading pumping and RO membrane systems of a wastewater reuse plant in Cyprus can significantly alleviate these drawbacks in terms cost, water recovery rate, and air pollution. The water-recovery rate of the upgraded RO plant increased from 43.2 to 75 percent, which resulted in a substantial net financial benefit due to the reduction in the quantity of wastewater purchased and the increase in potable water produced. The upgraded system also reduced the electricity requirement from 3.63 kWh/m3 to 1.92 kWh/m3. Pollution emissions decreased substantially because of the reduction in electricity requirements. The beneficiaries of these lower emission costs are the residents of Cyprus and global society. Overall, the benefit of upgrading the plant is highly attractive with more than 65 percent annual real internal rates of return in financial and economic terms. Positive net present values are realized for all the scenarios considered. Full article
(This article belongs to the Special Issue Water and Wastewater Treatment- Energy Efficiency)
11 pages, 1614 KiB  
Article
Abnormality Detection Method for Wind Turbine Bearings Based on CNN-LSTM
by Fanghong Zhang, Yuze Zhu, Chuanjiang Zhang, Peng Yu and Qingan Li
Energies 2023, 16(7), 3291; https://doi.org/10.3390/en16073291 - 6 Apr 2023
Cited by 6 | Viewed by 1502
Abstract
Wind turbine energy generators operate in a variety of environments and often under harsh operational conditions, which can result in the mechanical failure of wind turbines. In order to ensure the efficient operation of wind turbines, the detection of any abnormality in the [...] Read more.
Wind turbine energy generators operate in a variety of environments and often under harsh operational conditions, which can result in the mechanical failure of wind turbines. In order to ensure the efficient operation of wind turbines, the detection of any abnormality in the mechanics is particularly important. In this paper, a method for detecting abnormalities in the bearings of wind turbine energy generators, based on the cascade deep learning model, is proposed. First, data on the mechanics of wind turbine generators were collected, and the correlation between the data was studied in order to select the parameters related to the bearing temperature. Then, the logical relationship between the observation parameters and the target parameters was established based on a one-dimensional convolutional neural network (CNN) and a long short-term memory (LSTM) network, and the difference between the predicted temperature and the actual temperature was assessed using the root mean square error evaluation model. Finally, a numerical example was used to verify the operational data from a wind farm unit in northwest China. The results show that the CNN-LSTM model proposed in this paper can detect abnormalities earlier in the state of the main bearing than the LSTM model, and the CNN-LSTM model can detect abnormalities in the main bearing that the LSTM network cannot find. Full article
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21 pages, 5881 KiB  
Article
Simple and Robust MPPT Current Control of a Wound Rotor Synchronous Wind Generator
by Lucky Dube, Graham C. Garner, Karen S. Garner and Maarten J. Kamper
Energies 2023, 16(7), 3290; https://doi.org/10.3390/en16073290 - 6 Apr 2023
Cited by 4 | Viewed by 1720
Abstract
In the search for efficient non-permanent magnet variable-speed wind generator solutions, this paper proposes a maximum power point tracking (MPPT) current-control method for a wound rotor synchronous wind generator. The focus is on direct-drive, medium-speed wind generators. In the proposed method, the currents [...] Read more.
In the search for efficient non-permanent magnet variable-speed wind generator solutions, this paper proposes a maximum power point tracking (MPPT) current-control method for a wound rotor synchronous wind generator. The focus is on direct-drive, medium-speed wind generators. In the proposed method, the currents of the wound rotor synchronous generator (WRSG) are optimally adjusted according to the generator speed to ensure maximum power generation from the wind turbine without needing information on wind speed. The design, modeling, and simulation of the MPPT current controllers are done in Matlab/Simulink with the WRSG in the synchronous reference frame. The controller is put to the test using different wind speed profiles between cut-in and rated speeds. The simulation results indicate that the proposed current control method is simple, effective, and robust, suggesting its practical implementation. To validate the simulation results, experimental work on a 4.2 kW WRSG prototype system is presented to demonstrate the stability and robustness of the MPPT current control method in operating the turbine at or near the maximum power point. Full article
(This article belongs to the Special Issue Wind Energy Technologies Development)
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12 pages, 719 KiB  
Article
Analysis of Different Third-Generation Solar Cells Using the Discrete Electrical Model d1MxP
by João Paulo N. Torres, Ricardo A. Marques Lameirinhas, Catarina Pinho Correia Valério Bernardo, Sofia Lima Martins, Pedro Mendonça dos Santos, Helena Isabel Veiga, Maria João Marques Martins and Paula Manuela Santos do Rego Figueiredo
Energies 2023, 16(7), 3289; https://doi.org/10.3390/en16073289 - 6 Apr 2023
Cited by 3 | Viewed by 1175
Abstract
The performance of photovoltaic solar cells is usually analyzed using continuous models, for instance, 1M5P. I-V and P-V curves are fitted by a mathematical expression from the electrical model. In the case of 1M5P, characteristics are fitted using five parameters that are obtained [...] Read more.
The performance of photovoltaic solar cells is usually analyzed using continuous models, for instance, 1M5P. I-V and P-V curves are fitted by a mathematical expression from the electrical model. In the case of 1M5P, characteristics are fitted using five parameters that are obtained using a small number of I-V points from a wider set of data, keeping the curve shape given by the mathematical expression from the model. A novel model was recently proposed to overcome this issue. The d1MxP model is based on the discretization of the electrical behavior of the diodes in models such as 1M5P. The d1MxP methodology is equivalent to an analytical incremental calculation and since it connects the given points, the model error should be lower than the one obtained using models as 1M5P. It is based on the connection of adjacent points (with small voltage differences) instead of having the entire voltage range represented by some parameters (as the continuous models do, for instance, 1M5P). In this work, the d1MxP model is applied to perovskite solar cells and paint-type dye-sensitized solar cells. The aim is to analyze the behavior of the discrete model in different third-generation solar cells since their performance cannot be well characterized by the 1M5P model. The accuracy on the maximum power point is relevant, resulting in perovskite solar cells, an improvement of up to 2.61% and, in paint-type dye-sensitized solar cells, an increase of up to 5.03%. Full article
(This article belongs to the Special Issue Advances in Photovoltaic Solar Energy)
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17 pages, 7065 KiB  
Article
Numerical Study on the Mechanism of Coal and Gas Outburst in the Coal Seam Thickening Area during Mining
by Zhengshuai Liu, Longyong Shu, Zhonggang Huo and Yongpeng Fan
Energies 2023, 16(7), 3288; https://doi.org/10.3390/en16073288 - 6 Apr 2023
Cited by 3 | Viewed by 1054
Abstract
Most coal and gas outbursts occur in the coal thickness variation zone. However, it is difficult to illustrate the mechanism of outbursts in coal thickening areas by physical simulation experiments. In this study, a coupled multi-field model, established by considering the stress–strain field, [...] Read more.
Most coal and gas outbursts occur in the coal thickness variation zone. However, it is difficult to illustrate the mechanism of outbursts in coal thickening areas by physical simulation experiments. In this study, a coupled multi-field model, established by considering the stress–strain field, gas transport field and damage field, was used to investigate the evolution of stress, gas pressure and plastic failure zones under different variation gradients and amplitudes of coal thickness. The simulation results show that the stress peak at the coal thickening transition zone caused by mining is higher than that at the constant thickness coal seam. The stress peak at the coal thickening transition zone decreases from 18.8 MPa to 16.9 MPa with the increase in the transition zone from 0 m to 10 m under the constant coal thickness variation from 3 m to 7 m; while it increases from 16.2 MPa to 19.3 MPa with the increase in the transition zone from 2 m to 10 m under the constant coal thickness variation gradient of 45°. Similarly, the plastic deformation volume of the coal seam between the driving face and the coal thickening interface increases with the increase in the coal thickness variation gradient and amplitude. In addition, the gas pressure in the fracture declines slower in the coal thickness variation zone affected by the higher coal thickness variation gradients or amplitudes. The mechanism for outbursts occurring in the increasing coal thickness area was further discussed, and combined with the simulation results for the energy principle of outbursts. Compared with the constant thickness coal seam, the elastic energy increases from 1.85 MJ to 1.94 MJ, and the free gas expansion energy increases from 24.19 MJ to 50.57 MJ when the coal thickness varies from 3 m to 13 m within a 10 m transition zone. The variation of coal thickness causes higher stress, higher gas pressure and low coal strength, which triggers outbursts more easily. The research could provide the theoretical support to prevent and control outbursts in coal seam thickening areas during mining. Full article
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27 pages, 7183 KiB  
Review
Supercapacitor Energy Storages in Hybrid Power Supplies for Frequency-Controlled Electric Drives: Review of Topologies and Automatic Control Systems
by Polyakov Vladimir and Plotnikov Iurii
Energies 2023, 16(7), 3287; https://doi.org/10.3390/en16073287 - 6 Apr 2023
Cited by 6 | Viewed by 1963
Abstract
This article provides an overview of the use of supercapacitor energy storage systems in adjustable AC drives for various purposes. The structures of the power section of combined (hybrid) power supplies for vehicle electric drives (hybrid electric vehicles and public transport vehicles) and [...] Read more.
This article provides an overview of the use of supercapacitor energy storage systems in adjustable AC drives for various purposes. The structures of the power section of combined (hybrid) power supplies for vehicle electric drives (hybrid electric vehicles and public transport vehicles) and general-purpose electric drives of an industrial grade (cranes, freight, and passenger lifts) are given. This review focuses on the problems inherent in conventional solutions adopted in the implementation of the power section, as well as the effect that can be obtained when using supercapacitor energy storage systems in controlled electric drives. The topologies of reversible DC/DC converters for supercapacitor energy storage devices are considered with a comparative assessment of their advantages and disadvantages, as well as their areas of application. This paper provides an overview of the structures of automatic control systems for supercapacitor energy storage devices. The composition and principles of regulating variables, the types of regulators used, and the criteria for setting regulation systems are analysed. Full article
(This article belongs to the Section F1: Electrical Power System)
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13 pages, 3130 KiB  
Article
Synergistic Germanium-Decorated h-BN/MoS2 Heterostructure Nanosheets: An Advanced Electrocatalyst for Energy Storage Applications
by M. Saravanan, Rajkumar Palanisamy, V. Sethuraman, K. Diwakar, P. Senthil Kumar, P. Sundara Venkatesh, N. Kannan, R. Joel Kingston, K. Aravinth and Jinho Kim
Energies 2023, 16(7), 3286; https://doi.org/10.3390/en16073286 - 6 Apr 2023
Cited by 2 | Viewed by 1541
Abstract
Increasing concerns about the vulnerability of the world’s energy supply and the necessity to implement sustainable technologies have prompted researchers to develop high-performance electrocatalysts that are affordable and efficient for converting and storing renewable energy. This article reports a facile approach to fabricating [...] Read more.
Increasing concerns about the vulnerability of the world’s energy supply and the necessity to implement sustainable technologies have prompted researchers to develop high-performance electrocatalysts that are affordable and efficient for converting and storing renewable energy. This article reports a facile approach to fabricating two-dimensional (2D) Ge-decorated h-BN/MoS2 heterostructure nanosheets by self-assembly for multiple electrochemical applications such as supercapacitor and hydrogen evolution reactions. The organization of the physical and chemical links between the germanium modulations on the heterostructure of boron nitride/molybdenum sulphide (Ge/h-BN/MoS2) were facilitated to generate more active sites. Furthermore, the asymmetric supercapacitor of Ge-decorated h-BN/MoS2 amplified the capacitance to 558.53 F g−1 at 1 A g−1 current density and 159.19 F g−1 at 10 A g−1, in addition to a retention rate of 85.69% after 2000 cycles. Moreover, the Ge-decorated h-BN/MoS2 catalyst realized a low over-potential value, with an RHE of 0.57 (HER) at 5 mA/cm2, a Tafel value of ∼204 mV/dec, and long-term electrolysis stability of 10 h. This work may open the door for further investigations on metal-decorated heterostructures, which have a significant potential for both supercapacitor and water-splitting applications. Full article
(This article belongs to the Section L: Energy Sources)
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15 pages, 4145 KiB  
Article
Process Improvement of Biogas Production from Sewage Sludge Applying Iron Oxides-Based Additives
by Regimantas Dauknys and Aušra Mažeikienė
Energies 2023, 16(7), 3285; https://doi.org/10.3390/en16073285 - 6 Apr 2023
Cited by 1 | Viewed by 1289
Abstract
Iron additives are effective in the anaerobic sewage sludge digestion process, but the composition and dosage of these additives are not precisely defined. This research investigates the effects of three iron oxides-based additives on the destruction of volatile solids, the production and quality [...] Read more.
Iron additives are effective in the anaerobic sewage sludge digestion process, but the composition and dosage of these additives are not precisely defined. This research investigates the effects of three iron oxides-based additives on the destruction of volatile solids, the production and quality of biogas, as well as the quality of the supernatant. Additive No 1 contained >41.5% of FeO and >41.5% of Fe2O3, additive No 2 contained ≥86% of Fe3O4, and additive No 3 contained ≥98% of Fe3O4. The best results were obtained by applying an iron oxides-based additive with a higher content of divalent iron oxide. The increase in efficiency of the VSs destruction was not significant and on average 2.2%. The increase in biogas production was on average 20% while the average increase in the content of methane in the biogas was 6.3%. Applying the additive, the reduction in the concentration of ammonium nitrogen in the supernatant was up to 28%, as well as a reduction in the concentration of phosphate phosphorus in the supernatant by up to 3.1 times could be expected compared to the case when the additive was not applied. The dose of additive No 1 was between 7.5 g/kg of dry solids and 15 g/kg of dry solids in the lab-scale test. The dose was specified in the full-scale test, and the recommended dose of the additive was 10 g/kg of dry solids to improve biogas production. Full article
(This article belongs to the Special Issue Wastewater Treatment Related to Energy)
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41 pages, 1472 KiB  
Review
A Review of CCUS in the Context of Foams, Regulatory Frameworks and Monitoring
by Alirza Orujov, Kipp Coddington and Saman A. Aryana
Energies 2023, 16(7), 3284; https://doi.org/10.3390/en16073284 - 6 Apr 2023
Cited by 3 | Viewed by 4201
Abstract
Greenhouse gas emission into the atmosphere is considered the main reason for the rise in Earth’s mean surface temperature. According to the Paris Agreement, to prevent the rise of the global average surface temperature beyond two degrees Celsius, global CO2 emissions must [...] Read more.
Greenhouse gas emission into the atmosphere is considered the main reason for the rise in Earth’s mean surface temperature. According to the Paris Agreement, to prevent the rise of the global average surface temperature beyond two degrees Celsius, global CO2 emissions must be cut substantially. While a transition to a net-zero emission scenario is envisioned by mid-century, carbon capture, utilization, and storage (CCUS) will play a crucial role in mitigating ongoing greenhouse gas emissions. Injection of CO2 into geological formations is a major pathway to enable large-scale storage. Despite significant recent technological advancements, mass deployment of these technologies still faces several technical and non-technical difficulties. This paper provides an overview of technical milestones reached thus far in CO2 capture, utilization, geological storage, monitoring technologies, and non-technical aspects such as regulatory frameworks and related policies in the US and the rest of the world. This paper describes different injection methods to store CO2 in various subsurface formations, the use of foams and the resulting potential gains in CO2 storage capacity, the role of nanoparticles for foam stabilization, and ensuring long-term storage safety. This work also addresses several safety-related aspects of geological storage and subsurface monitoring technologies that may mitigate risks associated with long-term storage. Full article
(This article belongs to the Topic Low-Carbon Power and Energy Systems)
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14 pages, 236 KiB  
Article
Electricity Supply Unreliability and Technical Efficiency: Evidence from Listed Chinese Manufacturing Companies
by Presley K. Wesseh, Jr., Yuqing Zhong and Chin Hui Hao
Energies 2023, 16(7), 3283; https://doi.org/10.3390/en16073283 - 6 Apr 2023
Cited by 1 | Viewed by 1047
Abstract
This study examines the extent to which electricity shortage influences technical efficiency using data of 805 listed manufacturing companies in China from 2009 to 2020 collected from the CSMAR database. To achieve the objectives of this paper, first, a stochastic frontier analysis (SFA) [...] Read more.
This study examines the extent to which electricity shortage influences technical efficiency using data of 805 listed manufacturing companies in China from 2009 to 2020 collected from the CSMAR database. To achieve the objectives of this paper, first, a stochastic frontier analysis (SFA) is used to estimate the technical efficiency (TE) score of manufacturing companies. Subsequently, the TE score is used to evaluate the electricity shortage index and other factors that are postulated to affect enterprise productivity. Two estimation methods have been adopted including ordinary least squares (OLS), which is less robust to endogeneity and instrumental variable (IV) estimation, which turns out to be more robust to endogeneity in the data. The empirical results show that, under OLS estimation, electricity shortage has a significantly negative impact on the technical efficiency of the listed manufacturing companies. However, when IV regression is implemented to address endogeneity issues in the data, electricity shortages tend to have a significantly positive impact on the technical efficiency, underscoring the importance of capturing endogeneity in the data. Extending the baseline results, this study also finds that, while the size of an enterprise may have no bearing, state-owned companies are more likely to be negatively affected by electricity shortages compared to privately owned companies. These results have significant implications for industrial policy design in China in particular, and developing countries in general. Most importantly, the results of this study underscore the importance of policies and measures to promote a shift in the ownership structure towards the private sector. Full article
24 pages, 23958 KiB  
Article
Acoustic Noise Reduction in an 8/6 Switched Reluctance Machine Using Structural Design
by Francisco Juarez-Leon, Nathan Emery and Berker Bilgin
Energies 2023, 16(7), 3282; https://doi.org/10.3390/en16073282 - 6 Apr 2023
Cited by 2 | Viewed by 1488
Abstract
Today, switched reluctance motors (SRMs) represent a promising technology for the long-term sustainability of electrified transportation, mainly due to their simpler structure, lower production cost, and robust configuration compared to other motor technologies. Notwithstanding, high acoustic noise and torque ripple are two performance [...] Read more.
Today, switched reluctance motors (SRMs) represent a promising technology for the long-term sustainability of electrified transportation, mainly due to their simpler structure, lower production cost, and robust configuration compared to other motor technologies. Notwithstanding, high acoustic noise and torque ripple are two performance imperfections that have prevented the widespread implementation of SRMs. This paper presents different structural design techniques to reduce the acoustic noise of an 8/6 SRM, while maintaining the electromagnetic performance of the machine. For each technique, a corresponding multiphysics FEA analysis of the motor’s performance is presented. The accuracy of the multiphysics model is confirmed experimentally using acoustic noise measurements obtained from a four-phase 8/6 SRM. Then, several structural techniques have been investigated on the 8/6 SRM represented in two main categories: stator-housing modifications and rotor modifications. The best design strategies are then combined to improve the acoustic noise level of the 8/6 SRM while maintaining its performance. Full article
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13 pages, 2976 KiB  
Article
Optimum Conditions for Enhanced Biohydrogen Production from a Mixture of Food Waste and Sewage Sludge with Alkali Pretreatment
by Joo-Youn Nam
Energies 2023, 16(7), 3281; https://doi.org/10.3390/en16073281 - 6 Apr 2023
Cited by 3 | Viewed by 1477
Abstract
Given the increasing demand for hydrogen, owing to its environmentally friendly nature, it is important to explore efficient methods for hydrogen production. This study investigates dark-fermentative hydrogen production by the co-digestion of food waste and sewage sludge. Both wastes were subjected to alkali [...] Read more.
Given the increasing demand for hydrogen, owing to its environmentally friendly nature, it is important to explore efficient methods for hydrogen production. This study investigates dark-fermentative hydrogen production by the co-digestion of food waste and sewage sludge. Both wastes were subjected to alkali pretreatment (at pH 13) to enhance biodegradability. Batch tests were conducted to enhance hydrogen production from food waste and sewage sludge under various volatile solid (VS) concentrations of 1.5–5% and food waste to sewage sludge mixing ratios of 0:100–100:0. We found that alkali pretreatment was effective in increasing hydrogen yields. The maximum specific hydrogen production rate of 163.8 mL H2/g volatile suspended solid/h was obtained at a VS concentration of 5.0% and food waste composition of 62.5%. Additionally, VS concentration of 2.8% and food waste composition of 100% yielded a maximum hydrogen production potential of 152.1 mL H2/g VS. Our findings indicate that food waste and sewage sludge with alkali pretreatment are potential substrates to produce biohydrogen. Full article
(This article belongs to the Special Issue CO2 Reduction and H2 Promotion Techniques in Energies)
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18 pages, 9617 KiB  
Article
The Scheduling Research of a Wind-Solar-Hydro Hybrid System Based on a Sand-Table Deduction Model at Ultra-Short-Term Scales
by Tianyao Zhang, Weibin Huang, Shijun Chen, Yanmei Zhu, Fuxing Kang, Yerong Zhou and Guangwen Ma
Energies 2023, 16(7), 3280; https://doi.org/10.3390/en16073280 - 6 Apr 2023
Viewed by 1295
Abstract
Establishing a wind-solar-hydro hybrid generation system is an effective way of ensuring the smooth passage of clean energy into the grid, and its related scheduling research is a complex and real-time optimization problem. Compared with the traditional scheduling method, this research investigates and [...] Read more.
Establishing a wind-solar-hydro hybrid generation system is an effective way of ensuring the smooth passage of clean energy into the grid, and its related scheduling research is a complex and real-time optimization problem. Compared with the traditional scheduling method, this research investigates and improves the accuracy of the scheduling model and the flexibility of the scheduling strategy. The paper innovatively introduces a sand-table deduction model and designs a real-time adaptive scheduling algorithm to evaluate the source-load matching capability of the hybrid wind-solar-hydro system at ultra-short-term scales, and verifies it through arithmetic examples. The results show that the proposed adaptive sand-table scheduling model can reflect the actual output characteristics of the hybrid wind-solar-hydro system, track the load curve, and suppress the fluctuation of wind and solar energy, with good source-load matching capability. Full article
(This article belongs to the Topic Multi-Energy Systems, 2nd Volume)
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24 pages, 12161 KiB  
Article
Hydromechanical Impacts of CO2 Storage in Coal Seams of the Upper Silesian Coal Basin (Poland)
by Maria Wetzel, Christopher Otto, Min Chen, Shakil Masum, Hywel Thomas, Tomasz Urych, Bartłomiej Bezak and Thomas Kempka
Energies 2023, 16(7), 3279; https://doi.org/10.3390/en16073279 - 6 Apr 2023
Cited by 5 | Viewed by 1653
Abstract
Deep un-mineable coal deposits are viable reservoirs for permanent and safe storage of carbon dioxide (CO2) due to their ability to adsorb large amounts of CO2 in the microporous coal structure. A reduced amount of CO2 released into the [...] Read more.
Deep un-mineable coal deposits are viable reservoirs for permanent and safe storage of carbon dioxide (CO2) due to their ability to adsorb large amounts of CO2 in the microporous coal structure. A reduced amount of CO2 released into the atmosphere contributes in turn to the mitigation of climate change. However, there are a number of geomechanical risks associated with the commercial-scale storage of CO2, such as potential fault or fracture reactivation, microseismic events, cap rock integrity or ground surface uplift. The present study assesses potential site-specific hydromechanical impacts for a coal deposit of the Upper Silesian Coal Basin by means of numerical simulations. For that purpose, a near-field model is developed to simulate the injection and migration of CO2, as well as the coal-CO2 interactions in the vicinity of horizontal wells along with the corresponding changes in permeability and stresses. The resulting effective stress changes are then integrated as boundary condition into a far-field numerical model to study the geomechanical response at site-scale. An extensive scenario analysis is carried out, consisting of 52 simulation runs, whereby the impacts of injection pressures, well arrangement within two target coal seams as well as the effect of different geological uncertainties (e.g., regional stress regime and rock properties) is examined for operational and post-operational scenarios. The injection-induced vertical displacements amount in maximum to 3.59 cm and 1.07 cm directly above the coal seam and at the ground surface, respectively. The results further demonstrate that neither fault slip nor dilation, as a potential consequence of slip, are to be expected during the investigated scenarios. Nevertheless, even if fault integrity is not compromised, dilation tendencies indicate that faults may be hydraulically conductive and could represent local pathways for upward fluid migration. Therefore, the site-specific stress regime has to be determined as accurately as possible by in-situ stress measurements, and also fault properties need to be accounted for an extensive risk assessment. The present study obtained a quantitative understanding of the geomechanical processes taking place at the operational and post-operational states, supporting the assessment and mitigation of environmental risks associated with CO2 storage in coal seams. Full article
(This article belongs to the Special Issue Advances in Carbon Capture, Utilization and Storage (CCUS))
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18 pages, 5497 KiB  
Article
The Apeli: An Affordable, Low-Emission and Fuel-Flexible Tier 4 Advanced Biomass Cookstove
by Dennis Krüger and Özge Mutlu
Energies 2023, 16(7), 3278; https://doi.org/10.3390/en16073278 - 6 Apr 2023
Cited by 1 | Viewed by 1996
Abstract
Based on the decision of representatives from the West African region and feedback from locals in Togo, an advanced continuous-feed, forced-draft, biomass cookstove named “Apeli” was developed. The stove was tested in modified ISO measurements based on the ISO 19867-1:2018 standard. This included [...] Read more.
Based on the decision of representatives from the West African region and feedback from locals in Togo, an advanced continuous-feed, forced-draft, biomass cookstove named “Apeli” was developed. The stove was tested in modified ISO measurements based on the ISO 19867-1:2018 standard. This included a long shutdown operation using wood pellets and short shutdown operations using wood pellets, bamboo pellets, wheat straw pellets and palm kernel shells. Due to the fast shutdown capability, the short shutdown was chosen for more realistic results using this stove type. For cold start and long shutdown operation using wood pellets, the thermal efficiency is determined as 44.1% at a 1116 W power output by emitting 0.272 g CO and 17.2 mg PM 2.5 per MJd at high load. At low load, the efficiency is 38.0% at a 526 W power output by emitting 1.1 g CO and 45.1 mg PM 2.5 per MJd. Due to a misinterpretation of the standard, the burnout duration of the tests with long shutdown is approx. 1.5 min shorter than required. Using a worst-case approximation, values for a theoretical ISO-conforming measurement were calculated and rated according to the ISO 19867-3:2018 standard. The results showed that the Apeli would correspond to Tier 4 for efficiency and PM 2.5 as well as Tier 5 for CO in high-power operation using wood pellets. The use of alternative fuels is possible, but can lead to higher emissions compared to the use of wood pellets. With regard to possibly using the biochar produced in the process for soil application, it has been demonstrated that the PAH content ensures European BioChar-Agro-Organic limitations. The first results of a field test in Togo have shown that operating and feeding the stove by the target group is easy. The required permanent presence of the user during cooking with this stove seems to have a limited influence on acceptance, which seems to primarily depend on the age of the user. Moreover, it can be concluded that the Apeli has good potential to be mass-produced locally at low costs with a reliable supply of spare parts. This can contribute not only to improving clean cooking, but also to fighting air pollution and deforestation caused by solid fuel burning due to the reduced consumption of resources in the form of fuel, especially wood. Full article
(This article belongs to the Section B: Energy and Environment)
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20 pages, 6425 KiB  
Article
Global Hydrogen and Synfuel Exchanges in an Emission-Free Energy System
by Felix Lippkau, David Franzmann, Thushara Addanki, Patrick Buchenberg, Heidi Heinrichs, Philipp Kuhn, Thomas Hamacher and Markus Blesl
Energies 2023, 16(7), 3277; https://doi.org/10.3390/en16073277 - 6 Apr 2023
Cited by 5 | Viewed by 1932
Abstract
This study investigates the global allocation of hydrogen and synfuels in order to achieve the well below 2 °C, preferably 1.5 °C target set in the Paris Agreement. For this purpose, TIMES Integrated Assessment Model (TIAM), a global energy system model is used. [...] Read more.
This study investigates the global allocation of hydrogen and synfuels in order to achieve the well below 2 °C, preferably 1.5 °C target set in the Paris Agreement. For this purpose, TIMES Integrated Assessment Model (TIAM), a global energy system model is used. In order to investigate global hydrogen and synfuel flows, cost potential curves are aggregated and implemented into TIAM, as well as demand technologies for the end use sectors. Furthermore, hydrogen and synfuel trades are established using liquid hydrogen transport (LH2), and both new and existing technologies for synfuels are implemented. To represent a wide range of possible future events, four different scenarios are considered with different characteristics of climate and security of supply policies. The results show that in the case of climate policy, the renewable energies need tremendous expansion. The final energy consumption is shifting towards the direct use of electricity, while certain demand technologies (e.g., aviation and international shipping) require hydrogen and synfuels for full decarbonization. Due to different security of supply policies, the global allocation of hydrogen and synfuel production and exports is shifting, while the 1.5 °C target remains feasible in the different climate policy scenarios. Considering climate policy, Middle East Asia is the preferred region for hydrogen export. For synfuel production, several regions are competitive, including Middle East Asia, Mexico, Africa, South America and Australia. In the case of security of supply policies, Middle East Asia is sharing the export volume with Africa, while only minor changes can be seen in the synfuel supply. Full article
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22 pages, 16509 KiB  
Article
Sustainable Retrofit of Existing Buildings: Impact Assessment of Residual Fluorocarbons through Uncertainty and Sensitivity Analyses
by Gianluca Maracchini, Rocco Di Filippo, Rossano Albatici, Oreste S. Bursi and Rosa Di Maggio
Energies 2023, 16(7), 3276; https://doi.org/10.3390/en16073276 - 6 Apr 2023
Cited by 3 | Viewed by 1262
Abstract
Fluorocarbons are an important category of greenhouse gas emissions, and currently, their use is prohibited due to their significant contribution to the global ozone depletion potential (ODP). During this century, they will continue to emit greenhouse gases into the environment since they are [...] Read more.
Fluorocarbons are an important category of greenhouse gas emissions, and currently, their use is prohibited due to their significant contribution to the global ozone depletion potential (ODP). During this century, they will continue to emit greenhouse gases into the environment since they are present in the thermal insulation foam and HVAC systems in existing buildings; however, proper disposal of these banks of CFCs/HFCs from existing buildings can limit their effects on the environment. However, there are no studies that have investigated quantifying the achievable environmental savings in this case. In this study, a comparative life cycle assessment (LCA) is conducted to evaluate, for the first time in the literature, the environmental savings achievable through the removal and disposal of CFC/HFC banks from buildings including damage-related emissions. To cope with the scarcity of data, uncertainty and sensitivity analysis techniques are applied. The results show that, for the selected archetype building, the largest annual emissions of CFCs/HFCs come from the external thermal insulation of the envelope. The removal of this material can lead to an additional significant reduction in the GWP (up to 569 kgCO2eq/m2) and the ODP (up to 117 × 10−3 kgCFC-11eq/m2), i.e., higher than that achievable by reducing energy consumption through energy retrofit measures (276 and 0, respectively). Thus, CFC/HFC banks should not be neglected in LCA studies of existing buildings due to their possible significant impact on a building’s ecoprofile. Full article
(This article belongs to the Section G: Energy and Buildings)
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15 pages, 7247 KiB  
Article
Gas Hydrates Reserve Characterization Using Thermo-Hydro-Mechanical Numerical Simulation: A Case Study of Green Canyon 955, Gulf of Mexico
by Sulav Dhakal and Ipsita Gupta
Energies 2023, 16(7), 3275; https://doi.org/10.3390/en16073275 - 6 Apr 2023
Viewed by 1171
Abstract
The Gulf of Mexico is a widely explored and producing region for offshore oil and gas resources, with significant submarine methane hydrates. Estimates of hydrate saturation and distribution rely on drilling expeditions and seismic surveys that tend to provide either large-scale estimates or [...] Read more.
The Gulf of Mexico is a widely explored and producing region for offshore oil and gas resources, with significant submarine methane hydrates. Estimates of hydrate saturation and distribution rely on drilling expeditions and seismic surveys that tend to provide either large-scale estimates or highly localized well data. In this study, hydrate reserve characterization is done using numerical simulation at Green Canyon block 955 (GC955). In addition, coupled thermo-hydro-mechanical (THM) simulation results show that hydrate saturation and geobody distribution are determined by the thermodynamic conditions as well as reservoir structures, stratigraphic differences, and permeability differences. Hydrate formation due to upflow of free gas and dissociation due to gas production and oceanic temperature rise due to climate change are simulated. The abundance of free gas under the hydrate stability zone and favorable pressure and temperature meant little hydrate was depleted from the reservoir. Furthermore, the maximum displacement due to warming reached 0.5 m in 100 years and 4.2 m in 180 days based on a simulation of constant production of methane gas. The displacement direction and magnitude suggest that there is little possibility of slope failure. Therefore, the GC955 site studied in this paper can be considered a favorable site for potential hydrate exploitation. Full article
(This article belongs to the Section H: Geo-Energy)
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21 pages, 6876 KiB  
Article
P-Y Curve Correction of Shallow Seabed Formation Containing Hydrate
by Haoyu Diao, Honghai Fan, Rongyi Ji, Bangchen Wu, Yuguang Ye, Yuhan Liu, Fei Zhou, Yixiang Yang and Zhi Yan
Energies 2023, 16(7), 3274; https://doi.org/10.3390/en16073274 - 6 Apr 2023
Cited by 2 | Viewed by 1031
Abstract
With the continuous growth in global energy demand, the exploration and development of hydrates has been the focus of increasing attention, and the accurate evaluation of the mechanical properties of hydrate layers has become particularly important. In this study, using a self-developed hydrate [...] Read more.
With the continuous growth in global energy demand, the exploration and development of hydrates has been the focus of increasing attention, and the accurate evaluation of the mechanical properties of hydrate layers has become particularly important. In this study, using a self-developed hydrate sample preparation device and hydrate triaxial seepage test platform, triaxial shear tests were carried out using the in situ synthesis method for hydrate sediment in the laboratory, and the stress–strain curves of hydrate sediment with different levels of saturation were obtained. By analyzing the stress–strain curve, the mechanical parameters of hydrate sediment were calculated and simulated using ABAQUS (2021, Dassault systemes, Vélizy Villacoublay France) finite element software. Several p-y curves were calculated and compared with the simulation results, and the p-y curve correction method of the hydrate layer in a shallow seabed was obtained. It was found that the strength of the hydrate sediment increased with an increase in saturation. At the same time, an increase in confining pressure and a decrease in temperature also increased the strength of hydrate deposits. Through comparison with the existing API (American Petroleum Institute) standard p-y curve, it was found that its strength is low because the existence of the hydrate improves the formation strength. Full article
(This article belongs to the Section H: Geo-Energy)
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14 pages, 738 KiB  
Article
Online Lifetime Prediction for Lithium-Ion Batteries with Cycle-by-Cycle Updates, Variance Reduction, and Model Ensembling
by Calum Strange, Rasheed Ibraheem and Gonçalo dos Reis
Energies 2023, 16(7), 3273; https://doi.org/10.3390/en16073273 - 6 Apr 2023
Cited by 3 | Viewed by 2147
Abstract
Lithium-ion batteries have found applications in many parts of our daily lives. Predicting their remaining useful life (RUL) is thus essential for management and prognostics. Most approaches look at early life prediction of RUL in the context of designing charging profiles or optimising [...] Read more.
Lithium-ion batteries have found applications in many parts of our daily lives. Predicting their remaining useful life (RUL) is thus essential for management and prognostics. Most approaches look at early life prediction of RUL in the context of designing charging profiles or optimising cell design. While critical, said approaches are not directly applicable to the regular testing of cells used in applications. This article focuses on a class of models called ‘one-cycle’ models which are suitable for this task and characterized by versatility (in terms of online prediction frameworks and model combinations), prediction from limited input, and cells’ history independence. Our contribution is fourfold. First, we show the wider deployability of the so-called one-cycle model for a different type of battery data, thus confirming its wider scope of use. Second, reflecting on how prediction models can be leveraged within battery management cloud solutions, we propose a universal Exponential-smoothing (e-forgetting) mechanism that leverages cycle-to-cycle prediction updates to reduce prediction variance. Third, we use this new model as a second-life assessment tool by proposing a knee region classifier. Last, using model ensembling, we build a “model of models”. We show that it outperforms each underpinning model (from in-cycle variability, cycle-to-cycle variability, and empirical models). This ‘ensembling’ strategy allows coupling explainable and black-box methods, thus giving the user extra control over the final model. Full article
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26 pages, 11088 KiB  
Article
Thermoacoustic Combustion Stability Analysis of a Bluff Body-Stabilized Burner Fueled by Methane–Air and Hydrogen–Air Mixtures
by Vito Ceglie, Michele Stefanizzi, Tommaso Capurso, Francesco Fornarelli and Sergio M. Camporeale
Energies 2023, 16(7), 3272; https://doi.org/10.3390/en16073272 - 6 Apr 2023
Cited by 1 | Viewed by 1910
Abstract
Hydrogen can play a key role in the gradual transition towards a full decarbonization of the combustion sector, e.g., in power generation. Despite the advantages related to the use of this carbon-free fuel, there are still several challenging technical issues that must be [...] Read more.
Hydrogen can play a key role in the gradual transition towards a full decarbonization of the combustion sector, e.g., in power generation. Despite the advantages related to the use of this carbon-free fuel, there are still several challenging technical issues that must be addressed such as the thermoacoustic instability triggered by hydrogen. Given that burners are usually designed to work with methane or other fossil fuels, it is important to investigate their thermoacoustic behavior when fueled by hydrogen. In this framework, the present work aims to propose a methodology which combines Computational Fluid Dynamics CFD (3D Reynolds-Averaged Navier-Stokes (RANS)) and Finite Element Method (FEM) approaches in order to investigate the fluid dynamic and the thermoacoustic behavior introduced by hydrogen in a burner (a lab-scale bluff body stabilized burner) designed to work with methane. The case of CH4-air mixture was used for the validation against experimental results and benchmark CFD data available in the literature. Numerical results obtained from CFD simulations, namely thermofluidodynamic properties and flame characteristics (i.e., time delay and heat release rate) are used to evaluate the effects of the fuel change on the Flame Response Function to the acoustic perturbation by means of a FEM approach. As results, in the H2-air mixture case, the time delay decreases and heat release rate increases with respect to the CH4-air mixture. A study on the Rayleigh index was carried out in order to analyze the influence of H2-air mixture on thermoacoustic instability of the burner. Finally, an analysis of both frequency and growth rate (GR) on the first four modes was carried out by comparing the two mixtures. In the H2-air case the modes are prone to become more unstable with respect to the same modes of the case fueled by CH4-air, due to the change in flame topology and variation of the heat release rate and time delay fields. Full article
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21 pages, 3979 KiB  
Review
Review of Methods to Create Meteorological Data Suitable for Moisture Control Design by Hygrothermal Building Envelope Simulation
by Sughwan Kim, Daniel Zirkelbach and Hartwig M. Künzel
Energies 2023, 16(7), 3271; https://doi.org/10.3390/en16073271 - 6 Apr 2023
Cited by 3 | Viewed by 1325
Abstract
Hygrothermal simulations have become essential for sustainable and resilient building design because moisture is the major cause of problems in buildings. Appropriate meteorological input data are important to obtain meaningful simulation results. Therefore, this article reviews different methods to create Hygrothermal Reference Years [...] Read more.
Hygrothermal simulations have become essential for sustainable and resilient building design because moisture is the major cause of problems in buildings. Appropriate meteorological input data are important to obtain meaningful simulation results. Therefore, this article reviews different methods to create Hygrothermal Reference Years (HRY) as severe or average climate inputs. The current standards define HRYs solely based on outdoor temperature, although moisture problems are caused by a combination of climate parameters, including driving rain and other loads. Therefore, there are also methods considering several impact parameters. The existing methods can be classified into two categories: construction-independent and construction-dependent methods. The former determines HRY based on a weather data analysis and is useful for large-scale parametric studies comprising many climatic parameters acting on buildings. The latter is based in addition to computer simulations to verify the HRY also in the context of specific construction types. It is a more comprehensive approach since the moisture responses of constructions are the decisive outcome for performance predictions. The advantages and disadvantages of the different methods are summarized and compared. Lastly, further research questions and simplifications aimed at practitioners are pointed out to arrive at reliable hygrothermal building performance predictions. Full article
(This article belongs to the Special Issue Energy Efficiency of the Buildings II)
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24 pages, 3951 KiB  
Article
Learning from Other Community Renewable Energy Projects: Transnational Transfer of Multi-Functional Energy Gardens from the Netherlands to Germany
by Maria Rosaria Di Nucci, Michael Krug, Lucas Schwarz, Vincenzo Gatta and Erik Laes
Energies 2023, 16(7), 3270; https://doi.org/10.3390/en16073270 - 6 Apr 2023
Viewed by 2576
Abstract
Citizen energy in general and renewable energy communities (RECs) in particular are becoming key vehicles for decentralisation, but also for the democratisation of the energy system. These initiatives are now more diverse than ever and are likely to continue to act as incubators [...] Read more.
Citizen energy in general and renewable energy communities (RECs) in particular are becoming key vehicles for decentralisation, but also for the democratisation of the energy system. These initiatives are now more diverse than ever and are likely to continue to act as incubators for significant projects in the transition to a renewable energy system. Beside the legal, regulatory, and financial challenges, there are several socio-economic and regulatory barriers that hinder the implementation of community energy projects. For this reason, policy learning and the dissemination of good/best practices that are transferable also to other contexts are important. This is an aspect that has not yet attracted much investigation, and only a few studies have explored the importance of transfer activities for the implementation of REC initiatives and their motives. This article aimed to address this knowledge gap by focussing on the transfer processes of best practices initiated in a particular region and discusses how these can be adapted and transferred to other contexts. We analysed the transfer case of a community renewable energy initiative, the multifunctional energy gardens, from the Netherlands to the German federal State of Thuringia, and extracted lessons with an overall validity for the transferability of drivers and success factors. We show how examples from other contexts with similar enabling conditions can represent significant foundations on which to build an effective strategy and what framework conditions are necessary to enhance the uptake of pervasive community energy initiatives in regions with low community energy development. Full article
(This article belongs to the Collection Renewable Energy and Energy Storage Systems)
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