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Volume 14
Issue 23
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Energies, Volume 14, Issue 23 (December-1 2021) – 366 articles

Cover Story (view full-size image): Carbon capture and utilization (CCU) is a promising solution able to mitigate the problem of carbon dioxide accumulation in the atmosphere, looking toward the removal of the carbon-based fuels in the energy production. Electrochemistry is an important tool that allows the implementation of both the capture and valorization of CO2. Via electrodialysis and regeneration of alkaline carbonate solutions, it is possible to separate carbon dioxide from flue gas, then a nanostructured catalyst converts it to syngas (a mixture of CO and H2) through catalytic reduction. Since syngas is a useful precursor for chemicals and fuels, this system is a green solution to achieve the carbon-neutral cycle. View this paper.
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20 pages, 728 KiB  
Article
Conceptualizing Walking and Walkability in the Smart City through a Model Composite w2 Smart City Utility Index
by Anna Visvizi, Shahira Assem Abdel-Razek, Roman Wosiek and Radosław Malik
Energies 2021, 14(23), 8193; https://doi.org/10.3390/en14238193 - 6 Dec 2021
Cited by 13 | Viewed by 3768
Abstract
This paper explores walking and walkability in the smart city and makes a case for their centrality in the debate on the resilience and sustainability of smart cities, as outlined in the United Nations’ (UN) Sustainable Development Goals (SDGs). It is argued that, [...] Read more.
This paper explores walking and walkability in the smart city and makes a case for their centrality in the debate on the resilience and sustainability of smart cities, as outlined in the United Nations’ (UN) Sustainable Development Goals (SDGs). It is argued that, while the human/inhabitant-centric paradigm of urban development consolidates, and research on walking, walkability, and pedestrian satisfaction flourishes, the inroads of ICT render it necessary to reflect on these issues in the conceptually- and geographically-delimited space of the smart city. More importantly, it becomes imperative to make respective findings useful and usable for policymakers. To this end, by approaching walking and walkability through the lens of utility, the objective of this paper is to develop a conceptual framework in which the relevance of walking and walkability, hereafter referred to as w2, as a distinct subject of research in the smart cities debate is validated. This framework is then employed to construct a model of a composite w2 smart city utility index. With the focus on the development of the conceptual framework, in which the w2 utility index is embedded, this paper constitutes the first conceptual step of the composite index development process. The value added of this paper is three-fold: First, the relevance of walking and walkability as a distinct subject of research in the realm of smart cities research is established. Second, a mismatch between end-users’ satisfaction derived from walking and their perception of walkability and the objective factors influencing walking and walkability is identified and conceptualized by referencing the concept of utility. Third, a model smart city w2 utility index is proposed as a diagnostic and prognostic tool that, in the subsequent stages of research and implementation, will prove useful for decisionmakers and other stakeholders involved in the process of managing smart cities. Full article
(This article belongs to the Section G1: Smart Cities and Urban Management)
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17 pages, 3855 KiB  
Article
Performance Assessment of Using Thermoelectric Generators for Waste Heat Recovery from Vapor Compression Refrigeration Systems
by Alaa Attar, Mohamed Rady, Abdullah Abuhabaya, Faisal Albatati, Abdelkarim Hegab and Eydhah Almatrafi
Energies 2021, 14(23), 8192; https://doi.org/10.3390/en14238192 - 6 Dec 2021
Cited by 5 | Viewed by 2856
Abstract
This article reports on an experimental analysis and performance assessment of using thermoelectric generators (TEGs) for waste heat recovery from residential vapor compression refrigeration systems. The analysis shows that there is a good opportunity for waste heat recovery using TEGs by de-superheating refrigerant [...] Read more.
This article reports on an experimental analysis and performance assessment of using thermoelectric generators (TEGs) for waste heat recovery from residential vapor compression refrigeration systems. The analysis shows that there is a good opportunity for waste heat recovery using TEGs by de-superheating refrigerant after the compressor. Design and manufacturing of a de-superheater unit consisting of a tube and plate heat exchanger and thermoelectric generator modules (HE-TEGs) have been performed and integrated in an experimental test rig of R134a refrigeration cycle. Experimental assessment of the performance parameters, as compared to the basic refrigeration system, reveals that the overall coefficient of performance (COP) using HE-TEGs desuperheater unit increases by values ranging from 17% to 32% depending on the condenser and evaporator loads. Exergy analysis shows that the enhancement is attributed to reduction in the exergy destruction in the condenser and compressor due to lower values of condenser pressure and pressure ratio of the compressor. The output power of the HE-TEGs unit is found to be sufficient for driving the TEGs heat sinks air cooling fan, thus providing a passive de-superheating system without an additional external source of electricity. Further enhancement of the refrigeration cycle performance can be achieved by installation of additional HE-TEGs units. Full article
(This article belongs to the Special Issue Waste Heat Recovery Using Thermoelectric Generators)
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19 pages, 12819 KiB  
Article
Evolution of Temperature Field around Underground Power Cable for Static and Cyclic Heating
by Shahbaz Ahmad, Zarghaam Haider Rizvi, Joan Chetam Christine Arp, Frank Wuttke, Vineet Tirth and Saiful Islam
Energies 2021, 14(23), 8191; https://doi.org/10.3390/en14238191 - 6 Dec 2021
Cited by 10 | Viewed by 3830
Abstract
Power transmission covering long-distances has shifted from overhead high voltage cables to underground power cable systems due to numerous failures under severe weather conditions and electromagnetic pollution. The underground power cable systems are limited by the melting point of the insulator around the [...] Read more.
Power transmission covering long-distances has shifted from overhead high voltage cables to underground power cable systems due to numerous failures under severe weather conditions and electromagnetic pollution. The underground power cable systems are limited by the melting point of the insulator around the conductor, which depends on the surrounding soils’ heat transfer capacity or the thermal conductivity. In the past, numerical and theoretical studies have been conducted based on the mechanistic heat and mass transfer model. However, limited experimental evidence has been provided. Therefore, in this study, we performed a series of experiments for static and cyclic thermal loads with a cylindrical heater embedded in the sand. The results suggest thermal charging of the surrounding dry sand and natural convection within the wet sand. A comparison of heat transfer for dry, unsaturated and fully saturated sand is presented with graphs and colour maps which provide valuable information and insight of heat and mass transfer around an underground power cable. Furthermore, the measurements of thermal conductivity against density, moisture and temperature are presented showing positive nonlinear dependence. Full article
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24 pages, 40023 KiB  
Review
A Review on the Production of Light Olefins Using Steam Cracking of Hydrocarbons
by Zahra Gholami, Fatemeh Gholami, Zdeněk Tišler and Mohammadtaghi Vakili
Energies 2021, 14(23), 8190; https://doi.org/10.3390/en14238190 - 6 Dec 2021
Cited by 64 | Viewed by 21208
Abstract
Light olefins are the main building blocks used in the petrochemical and chemical industries for the production of different components such as polymers, synthetic fibers, rubbers, and plastic materials. Currently, steam cracking of hydrocarbons is the main technology for the production of light [...] Read more.
Light olefins are the main building blocks used in the petrochemical and chemical industries for the production of different components such as polymers, synthetic fibers, rubbers, and plastic materials. Currently, steam cracking of hydrocarbons is the main technology for the production of light olefins. In steam cracking, the pyrolysis of feedstocks occurs in the cracking furnace, where hydrocarbon feed and steam are first mixed and preheated in the convection section and then enter the furnace radiation section to crack to the desired products. This paper summarizes olefin production via the steam cracking process; and the reaction mechanism and cracking furnace are also discussed. The effect of different operating parameters, including temperature, residence time, feedstock composition, and the steam-to-hydrocarbon ratio, are also reviewed. Full article
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14 pages, 6062 KiB  
Article
The Impact of Government Subsidies on Single-Channel Recycling Based on Recycling Propaganda
by Fangfang Zhang, Hao Wang and Xiaoyu Wu
Energies 2021, 14(23), 8189; https://doi.org/10.3390/en14238189 - 6 Dec 2021
Cited by 5 | Viewed by 2202
Abstract
The recycling of waste products is an important way to achieve global sustainable development. To analyze the impact of different objects of government subsidies on single-channel recycling based on recycling propaganda, four theory game models of single-channel recycling based on government subsidies and [...] Read more.
The recycling of waste products is an important way to achieve global sustainable development. To analyze the impact of different objects of government subsidies on single-channel recycling based on recycling propaganda, four theory game models of single-channel recycling based on government subsidies and recycling propaganda are established. By comparing and analyzing the effects of different subsidies and propaganda strategies on the recycling of waste products in the four models, this article mainly draws the following conclusions: the government selecting different objects to subsidize has the same effect on the unit recycling price, quantity, and revenue of waste products; when the government subsidizes the processors, the consigned recycling price of waste products will increase, but when the government subsidizes recyclers, it will decrease; when the propagandist is determined, the optimal value of propaganda is related to the sensitivity of residents to the unit recycling price of waste products, the unit propaganda of waste products, and the expenses of propagating waste products. Full article
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14 pages, 4636 KiB  
Article
Efficient Wireless Drone Charging Pad for Any Landing Position and Orientation
by Tommaso Campi, Silvano Cruciani, Francesca Maradei and Mauro Feliziani
Energies 2021, 14(23), 8188; https://doi.org/10.3390/en14238188 - 6 Dec 2021
Cited by 11 | Viewed by 3198
Abstract
A wireless charging pad for drones based on resonant magnetic technology to recharge the internal battery is presented. The goal of the study was to design a robust, reliable and efficient charging station where a drone can land to automatically recharge its battery. [...] Read more.
A wireless charging pad for drones based on resonant magnetic technology to recharge the internal battery is presented. The goal of the study was to design a robust, reliable and efficient charging station where a drone can land to automatically recharge its battery. The components of the wireless power transfer (WPT) system on board the drone must be compact and light in order not to alter the payload of the drone. In this study, the non-planar receiving coil of the WPT system is integrated into the drone’s landing gear while the transmitting pad is designed to be efficient for any landing point and orientation of the drone in the charging pad area. To meet these requirements, power transmission is accomplished by an array of planar coils integrated into the ground base station. The configuration of the WPT coil system, including a three-dimensional receiving coil and a multicoil transmitter, is deeply analyzed to evaluate the performance of the WPT, considering potential lateral misalignment and rotation of the receiving coil due to imprecise drone landing. According to the proposed configuration, the battery of a light drone (2 kg in weight and 0.5 kg in payload) is recharged in less than an hour, with an efficiency always greater than 75%. Full article
(This article belongs to the Special Issue Intelligent Wireless Power Transfer System and Its Application 2021)
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22 pages, 57559 KiB  
Article
A Data-Driven Clustering Analysis for the Impact of COVID-19 on the Electricity Consumption Pattern of Zhejiang Province, China
by Zhiang Zhang, Ali Cheshmehzangi and Saeid Pourroostaei Ardakani
Energies 2021, 14(23), 8187; https://doi.org/10.3390/en14238187 - 6 Dec 2021
Cited by 12 | Viewed by 2377
Abstract
The COVID-19 pandemic has impacted electricity consumption patterns and such an impact cannot be analyzed by simple data analytics. In China, specifically, city lock-down policies lasted for only a few weeks and the spread of COVID-19 was quickly under control. This has made [...] Read more.
The COVID-19 pandemic has impacted electricity consumption patterns and such an impact cannot be analyzed by simple data analytics. In China, specifically, city lock-down policies lasted for only a few weeks and the spread of COVID-19 was quickly under control. This has made it challenging to analyze the hidden impact of COVID-19 on electricity consumption. This paper targets the electricity consumption of a group of regions in China and proposes a new clustering-based method to quantitatively investigate the impact of COVID-19 on the industrial-driven electricity consumption pattern. This method performs K-means clustering on time-series electricity consumption data of multiple regions and uses quantitative metrics, including clustering evaluation metrics and dynamic time warping, to quantify the impact and pattern changes. The proposed method is applied to the two-year daily electricity consumption data of 87 regions of Zhejiang province, China, and quantitively confirms COVID-19 has changed the electricity consumption pattern of Zhejiang in both the short-term and long-term. The time evolution of the pattern change is also revealed by the method, so the impact start and end time can be inferred. Results also show the short-term impact of COVID-19 is similar across different regions, while the long-term impact is not. In some regions, the pandemic only caused a time-shift in electricity consumption; but in others, the electricity consumption pattern has been permanently changed. The data-driven analysis of this paper can be the first step to fully interpret the COVID-19 impact by considering economic and social parameters in future studies. Full article
(This article belongs to the Special Issue COVID-19 Pandemics: Energy, Economic, Environmental, Social, Policy and Health Impacts)
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18 pages, 9853 KiB  
Article
Experimental Research on the Selective Absorption of Solar Energy by Hybrid Nanofluids
by Xin Jin, Guiping Lin, Haichuan Jin, Zunru Fu and Haoyang Sun
Energies 2021, 14(23), 8186; https://doi.org/10.3390/en14238186 - 6 Dec 2021
Cited by 3 | Viewed by 2641
Abstract
As low-cost, widely distributed and easily accessible renewable clean energy, solar energy has attracted more and more attention. Direct absorption solar collectors can convert solar energy into heat, but their efficiency is closely related to the absorption performance of the working fluid. In [...] Read more.
As low-cost, widely distributed and easily accessible renewable clean energy, solar energy has attracted more and more attention. Direct absorption solar collectors can convert solar energy into heat, but their efficiency is closely related to the absorption performance of the working fluid. In order to improve the absorption efficiency of direct absorption solar collectors, an experimental study on the selective absorption of solar energy by hybrid nanofluids was carried out. Five hybrid nanofluids were prepared and characterized, and the energy transfer advantages of hybrid nanofluid over single nanofluid were carefully studied. Experiments have found that the light-to-heat conversion properties of hybrid nanofluids show no obvious advantages or disadvantages compared with single nanofluid, and their performance is closely related to the types of nanoparticles. In addition, the hybrid nanofluid generally has two peaks, exactly the same as the single nanofluid in the mixed component, but the absorption curve is flatter than that of the single nanofluid. Further research of more types of hybrid nanofluids can provide new insights into the use of solar energy. Full article
(This article belongs to the Topic Solar Thermal Energy and Photovoltaic Systems)
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23 pages, 5499 KiB  
Article
Pumping Schedule Optimization in Acid Fracturing Treatment by Unified Fracture Design
by Rahman Lotfi, Mostafa Hosseini, Davood Aftabi, Alireza Baghbanan and Guanshui Xu
Energies 2021, 14(23), 8185; https://doi.org/10.3390/en14238185 - 6 Dec 2021
Viewed by 2040
Abstract
Acid fracturing simulation has been widely used to improve well performance in carbonate reservoirs. In this study, a computational method is presented to optimize acid fracturing treatments. First, fracture geometry parameters are calculated using unified fracture design methods. Then, the controllable design parameters [...] Read more.
Acid fracturing simulation has been widely used to improve well performance in carbonate reservoirs. In this study, a computational method is presented to optimize acid fracturing treatments. First, fracture geometry parameters are calculated using unified fracture design methods. Then, the controllable design parameters are iterated till the fracture geometry parameters reach their optimal values. The results show higher flow rates are required to achieve optimal fracture geometry parameters with larger acid volumes. Detailed sensitivity analyses are performed on controllable and reservoir parameters. It shows that higher flow rates should be applied for fluids with lower viscosity. Straight acid reaches optimal conditions at higher flow rates and lower volumes. These conditions for retarded acids appear to be only at lower flow rates and higher volumes. The study of the acid concentration for gelled acids shows that both flow rate and volume increase as the concentration increases. For the formation with lower permeability, a higher flow rate is required to achieve the desired larger fracture half-length and smaller fracture width. Further investigations also show that the formation with higher Young’s modulus requires decreasing the acid volume and increasing the optimal flow rate, while the formation with higher closure stress requires increasing the acid volume and decreasing the flow rate. Full article
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25 pages, 5553 KiB  
Article
Passivity-Based Control of Water Pumping System Using BLDC Motor Drive Fed by Solar PV Array with Battery Storage System
by Ihor Shchur, Marek Lis and Yurii Biletskyi
Energies 2021, 14(23), 8184; https://doi.org/10.3390/en14238184 - 6 Dec 2021
Cited by 12 | Viewed by 2323
Abstract
In remote locations, it is advisable to combine solar water pumping with electric energy storage and power supply for other forms of consumption. In such complex systems, individual subsystems feature their own local control, and the general automatic control of the system in [...] Read more.
In remote locations, it is advisable to combine solar water pumping with electric energy storage and power supply for other forms of consumption. In such complex systems, individual subsystems feature their own local control, and the general automatic control of the system in different modes of its operation is carried out in accordance with an energy management strategy (EMS). In this paper, the functions of local and general control of the solar water pumping system with battery storage and external power supply are combined in the system of passivity-based control (PBC). The EMS is constructed in such a way that for all modes, only two PBC systems are developed, which are switched depending on the battery’s state of charge and the current levels of the two main disturbances—solar irradiation and electrical consumption. For each system, two control influence former (CIF) structures were synthesized and their operation was investigated by computer simulation. Despite the simplicity of CIFs’ implementation, due to the introduced interconnection and damping coefficients, such control allows the provision of the required voltage regulation with a static error up to 1%, sufficient quality of transients during disturbances and switching of the system structure, as well as system asymptotic stability. Full article
(This article belongs to the Special Issue Improvements of the Electricity Power System)
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23 pages, 5669 KiB  
Review
Applications of 2D MXenes for Electrochemical Energy Conversion and Storage
by Chenchen Ji, Haonan Cui, Hongyu Mi and Shengchun Yang
Energies 2021, 14(23), 8183; https://doi.org/10.3390/en14238183 - 6 Dec 2021
Cited by 9 | Viewed by 3860
Abstract
As newly emerged 2D layered transition metal carbides or carbonitrides, MXenes have attracted growing attention in energy conversion and storage applications due to their exceptional high electronic conductivity, ample functional groups (e.g., -OH, -F, -O), desirable hydrophilicity, and superior dispersibility in aqueous solutions. [...] Read more.
As newly emerged 2D layered transition metal carbides or carbonitrides, MXenes have attracted growing attention in energy conversion and storage applications due to their exceptional high electronic conductivity, ample functional groups (e.g., -OH, -F, -O), desirable hydrophilicity, and superior dispersibility in aqueous solutions. The significant advantages of MXenes enable them to be intriguing structural units to engineer advanced MXene-based nanocomposites for electrochemical storage devices with remarkable performances. Herein, this review summarizes the current advances of MXene-based materials for energy storage (e.g., supercapacitors, lithium ion batteries, and zinc ion storage devices), in which the fabrication routes and the special functions of MXenes for electrode materials, conductive matrix, surface modification, heteroatom doping, crumpling, and protective layer to prevent dendrite growth are highlighted. Additionally, given that MXene are versatile for self-assembling into specific configuration with geometric flexibility, great efforts about methodologies (e.g., vacuum filtration, mask-assisted filtration, screen printing, extrusion printing technique, and directly writing) of patterned MXene-based composite film or MXene-based conductive ink for fabricating more types of energy storage device were also discussed. Finally, the existing challenges and prospects of MXene-based materials and growing trend for further energy storage devices are also presented. Full article
(This article belongs to the Topic Applications of Nanomaterials in Energy Systems)
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15 pages, 3118 KiB  
Article
Methane Pyrolysis in Molten Potassium Chloride: An Experimental and Economic Analysis
by Jinho Boo, Eun Hee Ko, No-Kuk Park, Changkook Ryu, Yo-Han Kim, Jinmo Park and Dohyung Kang
Energies 2021, 14(23), 8182; https://doi.org/10.3390/en14238182 - 6 Dec 2021
Cited by 19 | Viewed by 5805
Abstract
Although steam methane reforming (CH4 + 2H2O → 4H2 + CO2) is the most commercialized process for producing hydrogen from methane, more than 10 kg of carbon dioxide is emitted to produce 1 kg of hydrogen. Methane [...] Read more.
Although steam methane reforming (CH4 + 2H2O → 4H2 + CO2) is the most commercialized process for producing hydrogen from methane, more than 10 kg of carbon dioxide is emitted to produce 1 kg of hydrogen. Methane pyrolysis (CH4 → 2H2 + C) has attracted much attention as an alternative to steam methane reforming because the co-product of hydrogen is solid carbon. In this study, the simultaneous production of hydrogen and separable solid carbon from methane was experimentally achieved in a bubble column filled with molten potassium chloride. The melt acted as a carbon-separating agent and as a pyrolytic catalyst, and enabled 40 h of continuous running without catalytic deactivation with an apparent activation energy of 277 kJ/mole. The resultant solid was purified by water washing or acid washing, or heating at high temperature to remove salt residues from the carbon. Heating the solid product at 1200 °C produced the highest purity carbon (97.2 at%). The economic feasibility of methane pyrolysis was evaluated by varying key parameters, that is, melt loss, melt price, and carbon revenue. Given a potassium chloride loss of <0.1 kg of salt per kg of produced carbon, the carbon revenue was calculated to be USD > 0.45 per kg of produced carbon. In this case, methane pyrolysis using molten potassium chloride may be comparable to steam methane reforming with carbon capture storage. Full article
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25 pages, 3494 KiB  
Review
The Current Picture of the Transition to a Green Economy in the EU—Trends in Climate and Energy Policy versus State Security
by Ireneusz Miciuła, Henryk Wojtaszek, Bogdan Włodarczyk, Marek Szturo, Miłosz Gac, Jerzy Będźmirowski, Katarzyna Kazojć and Judyta Kabus
Energies 2021, 14(23), 8181; https://doi.org/10.3390/en14238181 - 6 Dec 2021
Cited by 10 | Viewed by 2382
Abstract
This article presents the historical progression of changes and arguments indicating the need to move from fossil energy sources to the green economy in the European Union (EU) countries. It shows trends in the EU’s climate and energy policy compared to the rest [...] Read more.
This article presents the historical progression of changes and arguments indicating the need to move from fossil energy sources to the green economy in the European Union (EU) countries. It shows trends in the EU’s climate and energy policy compared to the rest of the world. At the same time, it points to the elements of the necessary compromise between the climate requirements and the energy security of countries and their economies. The aim of the article is to present the main quantitative challenges for the development of the green economy in the EU, which are analyzed from the perspective of the year 2030. For this year, specific values have been established to be achieved by European countries in several fundamental areas. On the other hand, the strategic goals and further development perspective are included until 2050. This undoubtedly indicates the complexity of the issue, which is intensified as a result of the various economic and political strategies of many European Union members. At the same time, as part of the analysis carried out, efforts are made to develop concepts and practical recommendations for the development of a green European economy. Full article
(This article belongs to the Special Issue Energy―History and Time Trends)
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15 pages, 1968 KiB  
Article
A Prediction Model of Pressure Loss of Cement Slurry in Deep-Water HTHP Directional Wells
by Kunhong Lv, Hao Huang, Xingqiang Zhong, Yian Tong, Xingjie Ling and Qiao Deng
Energies 2021, 14(23), 8180; https://doi.org/10.3390/en14238180 - 6 Dec 2021
Cited by 4 | Viewed by 1839
Abstract
The exploitations of deep-water wells often use directional well drilling to reach the target layer. Affected by special environments in deep water, the prediction of pressure loss of cement slurry is particularly important. This paper presents a prediction model of pressure loss suitable [...] Read more.
The exploitations of deep-water wells often use directional well drilling to reach the target layer. Affected by special environments in deep water, the prediction of pressure loss of cement slurry is particularly important. This paper presents a prediction model of pressure loss suitable for deep-water directional wells. This model takes the complex interaction between the temperature, pressure and hydration kinetics of cement slurry into account. Based on the initial and boundary conditions, the finite difference method is used to discretize and calculate the model to ensure the stability and convergence of the result calculated by this model. Finally, the calculation equation of the model is used to predict the transient temperature and pressure loss of Wells X1 and X2, and a comparison is made between the predicted value and the monitoring data. The comparison results show that the maximum error between the temperature and pressure predicted by the model and the field measured value is within 6%. Thus, this model is of high accuracy and can meet the needs of site construction. It is concluded that this result can provide reliable theoretical guidance for temperature and pressure prediction, as well as the anti-channeling design of HTHP directional wells. Full article
(This article belongs to the Special Issue Development of Unconventional Reservoirs 2021)
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14 pages, 2742 KiB  
Article
A Novel Low Voltage Selective Circuit Breaker with Additional Current Path
by Bartosz Rozegnał, Paweł Albrechtowicz and Piotr Cisek
Energies 2021, 14(23), 8179; https://doi.org/10.3390/en14238179 - 6 Dec 2021
Viewed by 1762
Abstract
The subject of the article is a description of the operating principle of the new proposal of the selective circuit breaker, which is an extension of the existing selective devices. The solution proposed in the article allows one to increase the selectivity range [...] Read more.
The subject of the article is a description of the operating principle of the new proposal of the selective circuit breaker, which is an extension of the existing selective devices. The solution proposed in the article allows one to increase the selectivity range of classic selective circuit breakers. In the case of networks with high values of short-circuit loop impedance, operating at reduced supply voltage, the proposed solution will not limit the short-circuit current too excessively as it is in the case of classic solutions. This advantage will allow for the correct reaction of the protections preceding them. The article presents the structure and analysis of the selection of parameters of the proposed solution. The results of simulation calculations have also been illustrated. Full article
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14 pages, 4853 KiB  
Article
Influence of Untreated Metal Waste from 3D Printing on Electrical Properties of Alkali-Activated Slag Mortars
by Lukáš Fiala, Michaela Petříková, Martin Keppert, Martin Böhm, Jaroslav Pokorný and Robert Černý
Energies 2021, 14(23), 8178; https://doi.org/10.3390/en14238178 - 6 Dec 2021
Viewed by 1941
Abstract
The negative environmental impact of cement production emphasizes the need to use alternative binders for construction materials. Alkali-activated slag is a more environmentally friendly candidate which can be utilized in the design of mortars with favorable material properties. However, the electrical properties of [...] Read more.
The negative environmental impact of cement production emphasizes the need to use alternative binders for construction materials. Alkali-activated slag is a more environmentally friendly candidate which can be utilized in the design of mortars with favorable material properties. However, the electrical properties of such materials are generally poor and need to be optimized by various metallic or carbon-based admixtures to gain new sophisticated material functions, such as self-sensing, self-heating, or energy harvesting. This paper investigates the influence of waste metal powder originating from the 3D printing process on the material properties of alkali-activated slag mortars. The untreated metal powder was characterized by means of XRD and SEM/EDS analyses revealing high nickel content, which was promising in terms of gaining self-heating function due to the high electrical conductivity and stability of nickel in a highly alkaline environment. The designed mortars with the waste metal admixture in the amount up to 250 wt.% to the slag and aggregates were then characterized in terms of basic physical, thermal, and electrical properties. Compared to the reference mortar, the designed mortars were of increased porosity of 17–32%. The thermal conductivity of ~1–1.1 W/m·K was at a favorable level for self-heating. However, the electrical conductivity of ~10−6 S/m was insufficient to allow the generation of the Joule heat. Even though a high amount of 3D printing waste could be used due to the good workability of mixtures, its additional treatment will be necessary to achieve reasonable, effective electrical conductivity of mortars resulting in self-heating function. Full article
(This article belongs to the Special Issue Experimental and Computational Assessment of Building Envelopes, Materials and Components)
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25 pages, 2337 KiB  
Article
Physical Constraints on Global Social-Ecological Energy System
by Marco Casazza, Francesco Gonella, Gengyuan Liu, Antonio Proto and Renato Passaro
Energies 2021, 14(23), 8177; https://doi.org/10.3390/en14238177 - 6 Dec 2021
Cited by 2 | Viewed by 2767
Abstract
Energy is the main driver of human Social-Ecological System (SES) dynamics. Collective energy properties of human SES can be described applying the principles of statistical mechanics: (i) energy consumption repartition; (ii) efficiency; (iii) performance, as efficient power, in relation to the least-action principle. [...] Read more.
Energy is the main driver of human Social-Ecological System (SES) dynamics. Collective energy properties of human SES can be described applying the principles of statistical mechanics: (i) energy consumption repartition; (ii) efficiency; (iii) performance, as efficient power, in relation to the least-action principle. International Energy Agency data are analyzed through the lens of such principles. Declining physical efficiency and growth of power losses emerge from our analysis. Losses mainly depend on intermediate system outputs and non-energy final output. Energy performance at Country level also depends on efficient power consumption. Better and worse performing Countries are identified accordingly. Five policy-relevant areas are identified in relation to the physical principles introduced in this paper: Improve efficiency; Decouple economic growth from environmental degradation; Focus on high value added and labor-intensive sectors; Rationalize inefficient fossil fuel subsidies that encourage wasteful consumption; Upgrade the technological capabilities. Coherently with our findings, policies should support the following actions: (1) redefine sectoral energy distribution shares; (2) Improve Country-level performance, if needed; (3) Reduce intermediate outputs and non-energy final output; (4) Reduce resources supply to improve eco-efficiency together with system performance. Full article
(This article belongs to the Collection Feature Papers in Energy, Environment and Well-Being)
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27 pages, 29474 KiB  
Article
Pine Wood and Sewage Sludge Torrefaction Process for Production Renewable Solid Biofuels and Biochar as Carbon Carrier for Fertilizers
by Piotr Piersa, Szymon Szufa, Justyna Czerwińska, Hilal Ünyay, Łukasz Adrian, Grzegorz Wielgosinski, Andrzej Obraniak, Wiktoria Lewandowska, Marta Marczak-Grzesik, Maria Dzikuć, Zdzislawa Romanowska-Duda and Tomasz P. Olejnik
Energies 2021, 14(23), 8176; https://doi.org/10.3390/en14238176 - 6 Dec 2021
Cited by 18 | Viewed by 2812
Abstract
This work presents the results of research on the thermo-chemical conversion of woody biomass–pine wood coming from lodzkie voivodship forests and sewage sludge from the Group Sewage Treatment Plant of the Łódź Urban Agglomeration. Laboratory scale analyses of the carbonization process were carried [...] Read more.
This work presents the results of research on the thermo-chemical conversion of woody biomass–pine wood coming from lodzkie voivodship forests and sewage sludge from the Group Sewage Treatment Plant of the Łódź Urban Agglomeration. Laboratory scale analyses of the carbonization process were carried out, initially using the TGA technique (to assess activation energy (EA)), followed by a flow reactor operating at temperature levels of 280–525 °C. Both the parameters of carbonized solid biofuel and biochar as a carrier for fertilizer (proximate and ultimate analysis) and the quality of the torgas (VOC) were analyzed. Analysis of the pine wood and sewage sludge torrefaction process shows clearly that the optimum process temperature would be around 325–350 °C from a mass loss ratio and economical perspective. This paper shows clearly that woody biomass, such as pine wood and sewage sludge, is a very interesting material both for biofuel production and in further processing for biochar production, used not only as an energy carrier but also as a new type of carbon source in fertilizer mixtures. Full article
(This article belongs to the Special Issue Biomass Torrefaction and Its Applications in Low-Carbon Industry)
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15 pages, 3688 KiB  
Article
Research on Dynamic Modeling of KF Algorithm for Detecting Distorted AC Signal
by Haoyao Nie and Xiaohua Nie
Energies 2021, 14(23), 8175; https://doi.org/10.3390/en14238175 - 6 Dec 2021
Cited by 1 | Viewed by 1427
Abstract
Kalman filter (KF) is often based on two models, which are phase angle vector (PAV) model and orthogonal vector (OV) model, in the application of distorted grid AC signal detection. However, these two models lack rigorous and detailed derivation from the principle of [...] Read more.
Kalman filter (KF) is often based on two models, which are phase angle vector (PAV) model and orthogonal vector (OV) model, in the application of distorted grid AC signal detection. However, these two models lack rigorous and detailed derivation from the principle of dynamic modeling. This paper presents a phase angle vector dynamic (PAVD) model and an orthogonal vector dynamic (OVD) model, which are combined with Kalman filter for detecting distorted grid AC signal. They reveal that the state noise covariance of the dynamic model−based KF is related to the sampling cycle, and overcome the defect of more detecting error for conventional model−based KF. Experiment and evaluation results show that the proposed KF algorithms are reasonable and effective. Therefore, this paper contributes a guiding significance for the application of KF algorithm in harmonic detection. Full article
(This article belongs to the Topic Application of Innovative Power Electronic Technologies)
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19 pages, 4823 KiB  
Article
Fog Computing Approach for Shared Mobility in Smart Cities
by Raafat Aburukba, A. R. Al-Ali, Ahmed H. Riaz, Ahmad Al Nabulsi, Danayal Khan, Shavaiz Khan and Moustafa Amer
Energies 2021, 14(23), 8174; https://doi.org/10.3390/en14238174 - 6 Dec 2021
Cited by 6 | Viewed by 2457
Abstract
Smart transportation a smart city application where traditional individual models are transforming to shared and distributed ownership. These models are used to serve commuters for inter- and intra-city travel. However, short-range urban transportation services within campuses, residential compounds, and public parks are not [...] Read more.
Smart transportation a smart city application where traditional individual models are transforming to shared and distributed ownership. These models are used to serve commuters for inter- and intra-city travel. However, short-range urban transportation services within campuses, residential compounds, and public parks are not explored to their full capacity compared to the distributed vehicle model. This paper aims to explore and design an adequate framework for battery-operated shared mobility within a large community for short-range travel. This work identifies the characteristics of the shared mobility for battery-operated vehicles and accordingly proposes an adequate solution that deals with real-time data collection, tracking, and automated decisions. Furthermore, given the requirement for real-time decisions with low latency for critical requests, the paper deploys the proposed framework within the 3-tier computing model, namely edge, fog, and cloud tiers. The solution design considers the power consumption requirement at the edge by offloading the computational requests to the fog tier and utilizing the LoRaWAN communication technology. A prototype implementation is presented to validate the proposed framework for a university campus using e-bikes. The results show the scalability of the proposed design and the achievement of low latency for requests that require real-time decisions. Full article
(This article belongs to the Special Issue Selected Papers from the 5th International Conference on Smart Grid and Smart Cities (ICSGSC2021))
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14 pages, 606 KiB  
Article
Identifying Actions to Prepare Electricity Infrastructure in Seaports for Future Power Supplying Cruise Ships with Energy from Land
by Joanna Kizielewicz and Katarzyna Skrzeszewska
Energies 2021, 14(23), 8173; https://doi.org/10.3390/en14238173 - 6 Dec 2021
Cited by 7 | Viewed by 2093
Abstract
Cruise ships are unfortunately at the infamous forefront of the means of maritime transport emitting the largest amounts of harmful substances into the atmosphere and aquatic environment. At the initiative of IMO and the European Union, formal restrictions were introduced regarding the level [...] Read more.
Cruise ships are unfortunately at the infamous forefront of the means of maritime transport emitting the largest amounts of harmful substances into the atmosphere and aquatic environment. At the initiative of IMO and the European Union, formal restrictions were introduced regarding the level of harmful emissions on the high seas and in ports generated by seagoing vessels. To meet these challenges, shipowners have invested in various technological solutions on their ships to reduce the number of harmful emissions, and by ordering new vessels; they promote the use of pro-ecological solutions related to energy saving and eliminate environmental harm. However, despite the actions taken by shipowners, seaports unfortunately lag behind the challenges and expectations of the market and are still not prepared, for example, to power the ships moored in ports with shore-side energy to reduce the environmental pollution when the ships are at berth. The aim of this paper is to identify actions taken by seaport authorities to prepare electricity infrastructure in seaports to power vessels with energy from the land. Key legal restrictions concerning reduction in pollutions emitted from ships in the ports are also described and analyzed. The results of the study also show the approach of seaports to the issue of Onshore Energy Supply for cruise ships. The research was conducted among the selected ports in the Baltic Sea Region where cruise ships are accepted. The following research questions were formulated: (1) What legal regulations oblige seaports and shipowners to reduce the level of pollutions emitted into the environment? (2) Do the ports use a benchmark to assess the level of harmful emissions when defining the amount of port fees for cruise shipowners? (3) How are cruise ships powered in the port? (4) What investments are planned in the port regarding the infrastructure related to the diversification of shore-side electricity for the ships? The studies were conducted by using a few research methods, i.e., the desk research method, the exploration method, and the CAWI Computer Assisted Web Interview. The results of this research can provide an interesting source of information both for cruise ship owners and cruise seaport authorities, but also potentially for shipyards where new vessels are constructed. Full article
(This article belongs to the Special Issue Sustainable Management of Energy Resources, Energy Strategies and Climate Change)
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13 pages, 4703 KiB  
Article
Investigation on Energy Flow Characteristics of Fuel Cell System Based on Real Vehicle Tests
by Zhijie Duan, Chen Li, Lili Feng, Shuguang Yu, Zengyou Jiang, Xiaoming Xu, Jichao Hong and Dongfang Chen
Energies 2021, 14(23), 8172; https://doi.org/10.3390/en14238172 - 6 Dec 2021
Cited by 2 | Viewed by 1870
Abstract
For fuel cell hybrid vehicles, the energy distribution mechanism of the fuel cell and power battery should reasonably allocate the power output of the fuel cell and power battery, optimize the efficiency of both and control the power battery SOC to fluctuate within [...] Read more.
For fuel cell hybrid vehicles, the energy distribution mechanism of the fuel cell and power battery should reasonably allocate the power output of the fuel cell and power battery, optimize the efficiency of both and control the power battery SOC to fluctuate within a reasonable range. To test the energy flow and operation characteristics of the powertrain of two hybrid car models on the market, two test vehicles (called vehicle A and vehicle B in this paper) are tested on an AIP 4WD chassis dynamometer under constant power and the China Light-Duty Vehicle Test Cycle-Passenger cycle condition, respectively. The test results show that vehicle A has a smaller power battery SOC variation interval and a lower variable rate than vehicle B. The cumulative power battery output energy of vehicle B is more significant than that of vehicle A. More importantly, the current rare public test reports of fuel cell vehicles make this study very valuable. This paper has important reference significance for the energy flow characteristics and energy management strategy of existing fuel cell hybrid vehicles. Full article
(This article belongs to the Special Issue Design, Testing and Fault Diagnosis for Fuel Cells)
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22 pages, 2845 KiB  
Article
A QoS-Aware Machine Learning-Based Framework for AMI Applications in Smart Grids
by Asfandyar Khan, Arif Iqbal Umar, Arslan Munir, Syed Hamad Shirazi, Muazzam A. Khan and Muhammad Adnan
Energies 2021, 14(23), 8171; https://doi.org/10.3390/en14238171 - 6 Dec 2021
Cited by 6 | Viewed by 2450
Abstract
The Internet of things (IoT) enables a diverse set of applications such as distribution automation, smart cities, wireless sensor networks, and advanced metering infrastructure (AMI). In smart grids (SGs), quality of service (QoS) and AMI traffic management need to be considered in the [...] Read more.
The Internet of things (IoT) enables a diverse set of applications such as distribution automation, smart cities, wireless sensor networks, and advanced metering infrastructure (AMI). In smart grids (SGs), quality of service (QoS) and AMI traffic management need to be considered in the design of efficient AMI architectures. In this article, we propose a QoS-aware machine-learning-based framework for AMI applications in smart grids. Our proposed framework comprises a three-tier hierarchical architecture for AMI applications, a machine-learning-based hierarchical clustering approach, and a priority-based scheduling technique to ensure QoS in AMI applications in smart grids. We introduce a three-tier hierarchical architecture for AMI applications in smart grids to take advantage of IoT communication technologies and the cloud infrastructure. In this architecture, smart meters are deployed over a georeferenced area where the control center has remote access over the Internet to these network devices. More specifically, these devices can be digitally controlled and monitored using simple web interfaces such as REST APIs. We modify the existing K-means algorithm to construct a hierarchical clustering topology that employs Wi-SUN technology for bi-directional communication between smart meters and data concentrators. Further, we develop a queuing model in which different priorities are assigned to each item of the critical and normal AMI traffic based on its latency and packet size. The critical AMI traffic is scheduled first using priority-based scheduling while the normal traffic is scheduled with a first-in–first-out scheduling scheme to ensure the QoS requirements of both traffic classes in the smart grid network. The numerical results demonstrate that the target coverage and connectivity requirements of all smart meters are fulfilled with the least number of data concentrators in the design. Additionally, the numerical results show that the architectural cost is reduced, and the bottleneck problem of the data concentrator is eliminated. Furthermore, the performance of the proposed framework is evaluated and validated on the CloudSim simulator. The simulation results of our proposed framework show efficient performance in terms of CPU utilization compared to a traditional framework that uses single-hop communication from smart meters to data concentrators with a first-in–first-out scheduling scheme. Full article
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35 pages, 75427 KiB  
Article
Setting and Testing of the Out-of-Step Protection at Mongolian Transmission System
by Francisco Gonzalez-Longatt, Choidorj Adiyabazar and Ernesto Vazquez Martinez
Energies 2021, 14(23), 8170; https://doi.org/10.3390/en14238170 - 6 Dec 2021
Cited by 8 | Viewed by 3567
Abstract
Modern distance relays have integrated numerous protection functions, including power-swing blocking and out-of-step or pole-slip tripping functions. The main purpose of the power-swing blocking function is to differentiate faults from power swings and block distance or other relay elements from operating during stable [...] Read more.
Modern distance relays have integrated numerous protection functions, including power-swing blocking and out-of-step or pole-slip tripping functions. The main purpose of the power-swing blocking function is to differentiate faults from power swings and block distance or other relay elements from operating during stable or unstable power swings. Most power-swing blocking elements are based on traditional methods that monitor the positive sequence impedance rate. The required settings for the power-swing blocking elements could be difficult to calculate in many applications, particularly those where fast swings can be expected. For these cases, extensive stability studies are necessary to determine the fastest rate of possible power swings. This paper presents a detailed step-by-step method for settings calculation of out-of-step (OOS) protection, both blocking and tripping functions considering a generic two-source system. Then the method is applied to define the protection relay settings installed at the interconnection between the Russian and Mongolian power systems, as it is crucial to feed the demand-rich Mongolian power system. In this paper, a specific impedance method is used for defining the OOS protection settings. This paper innovates by testing the settings using the recordings of the major events of 15 September 2018 in two approaches: hybrid co-simulation and cyber-physical. Both tests have demonstrated the appropriate performance of the proposed settings and proving the proposed methodology works appropriately. Full article
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19 pages, 2644 KiB  
Article
The Influencing Effects of Industrial Eco-Efficiency on Carbon Emissions in the Yangtze River Delta
by Zaijun Li, Xiang Zheng and Dongqi Sun
Energies 2021, 14(23), 8169; https://doi.org/10.3390/en14238169 - 6 Dec 2021
Cited by 6 | Viewed by 2230
Abstract
A low-carbon economy is the most important requirement to realize high-quality integrated development of the Yangtze River Delta. Utilizing the following models: a super-efficiency slacks-based measure model, a spatio-temporal correlation model, a bivariate LISA model, a spatial econometric model, and a geographically weighted [...] Read more.
A low-carbon economy is the most important requirement to realize high-quality integrated development of the Yangtze River Delta. Utilizing the following models: a super-efficiency slacks-based measure model, a spatio-temporal correlation model, a bivariate LISA model, a spatial econometric model, and a geographically weighted random forest model, this study measured urban industrial eco-efficiency (IEE) and then analyzed its influencing effects on carbon emission in the Yangtze River Delta from 2000 to 2017. The influencing factors included spatio-temporal correlation intensity, spatio-temporal association type, direct and indirect impacts, and local importance impacts. Findings showed that: (1) The temporal correlation intensity between IEE and scale efficiency (SE) and carbon emissions exhibited an inverted V-shaped variation trend, while the temporal correlation intensity between pure technical efficiency (PTE) and carbon emissions exhibited a W-shaped fluctuation trend. The negative spatial correlation between IEE and carbon emissions was mainly distributed in the developed cities of the delta, while the positive correlation was mainly distributed in central Anhui Province and Yancheng and Taizhou cities. The spatial correlation between PTE and carbon emissions exhibited a spatial pattern of being higher in the central part of the delta and lower in the northern and southern parts. The negative spatial correlation between SE and carbon emissions was mainly clustered in Zhejiang Province and scattered in Jiangsu and Anhui provinces, with the cities with positive correlations being concentrated around two locations: the junction of Anhui and Jiangsu provinces, and within central Jiangsu Province. (2) The direct and indirect effects of IEE on carbon emissions were significantly negative, indicating that IEE contributed to reducing carbon emissions. The direct impact of PTE on carbon emissions was also significantly negative, while its indirect effect was insignificant. Both the direct and indirect effects of SE on carbon emissions were significantly negative. (3) It was found that the positive effect of IEE was more likely to alleviate the increase in carbon emissions in northern Anhui City. Further, PTE was more conducive to reducing the increase in carbon emissions in northwestern Anhui City, southern Zhejiang City, and in other cities including Changzhou and Wuxi. Finally, it was found that SE played a relatively important role in reducing the increase in carbon emissions only in four cities: Changzhou, Suqian, Lu’an, and Wenzhou. Full article
(This article belongs to the Special Issue Low-Carbon Consumption and Production towards Carbon Neutrality in China)
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15 pages, 3970 KiB  
Article
Flexible Films as Anode Materials Based on rGO and TiO2/MnO2 in Li-Ion Batteries Free of Non-Active Agents
by Tomasz Kędzierski, Daria Baranowska, Damian Bęben, Beata Zielińska, Xuecheng Chen and Ewa Mijowska
Energies 2021, 14(23), 8168; https://doi.org/10.3390/en14238168 - 6 Dec 2021
Cited by 5 | Viewed by 2561
Abstract
Recently, to meet the growing demand for stable and flexible batteries, anodes in the form of thin films have drawn the attention of researchers. It is clear that mass production of such batteries would bring the worldwide distribution of flexible devices and wearable [...] Read more.
Recently, to meet the growing demand for stable and flexible batteries, anodes in the form of thin films have drawn the attention of researchers. It is clear that mass production of such batteries would bring the worldwide distribution of flexible devices and wearable electronics closer. Currently, electrodes are deposited on a flexible substrate and consist of conductive and binding agents that increase the volume/weight of the electrode. Here, we propose free-standing and non-active-material-free thin films based on reduced graphene oxide (rGO), titanium dioxide (TiO2) and manganese dioxide (MnO2) as working electrodes in lithium-ion half-cells prepared via the vacuum-assisted filtration method. The electrochemical performance of the assembled half-cells exhibited good cyclic stability and a reversible capacity at lower current densities. The addition of TiO2 and MnO2 improved the capacity of the rGO film, while rGO itself provided a stable rate performance. rGO/TiO2/MnO2 film showed the highest discharge capacity (483 mAh/g at 50 mA/g). In addition, all assembled cells displayed excellent repeatability and reversibility in cyclic voltammetry measurements and good lithium-ion diffusion through the electrolyte, SEI layer and the active material itself. Full article
(This article belongs to the Topic Energy Storage and Conversion Systems)
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12 pages, 1931 KiB  
Article
Effect of the Presence of HCl on Simultaneous CO2 Capture and Contaminants Removal from Simulated Biomass Gasification Producer Gas by CaO-Fe2O3 Sorbent in Calcium Looping Cycles
by Forogh Dashtestani, Mohammad Nusheh, Vilailuck Siriwongrungson, Janjira Hongrapipat, Vlatko Materic, Alex C. K. Yip and Shusheng Pang
Energies 2021, 14(23), 8167; https://doi.org/10.3390/en14238167 - 6 Dec 2021
Cited by 5 | Viewed by 2258
Abstract
This study investigated the effect of HCl in biomass gasification producer gas on the CO2 capture efficiency and contaminants removal efficiency by CaO-Fe2O3 based sorbent material in the calcium looping process. Experiments were conducted in a fixed bed reactor [...] Read more.
This study investigated the effect of HCl in biomass gasification producer gas on the CO2 capture efficiency and contaminants removal efficiency by CaO-Fe2O3 based sorbent material in the calcium looping process. Experiments were conducted in a fixed bed reactor to capture CO2 from the producer gas with the combined contaminants of HCl at 200 ppmv, H2S at 230 ppmv, and NH3 at 2300 ppmv. The results show that with presence of HCl in the feeding gas, sorbent reactivity for CO2 capture and contaminants removal was enhanced. The maximum CO2 capture was achieved at carbonation temperatures of 680 °C, with efficiencies of 93%, 92%, and 87%, respectively, for three carbonation-calcination cycles. At this carbonation temperature, the average contaminant removal efficiencies were 92.7% for HCl, 99% for NH3, and 94.7% for H2S. The outlet contaminant concentrations during the calcination process were also examined which is useful for CO2 reuse. The pore structure change of the used sorbent material suggests that the HCl in the feeding gas contributes to high CO2 capture efficiency and contaminants removal simultaneously. Full article
(This article belongs to the Topic Sustainable Energy Technology)
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13 pages, 2043 KiB  
Article
Concepts for Hydrogen Internal Combustion Engines and Their Implications on the Exhaust Gas Aftertreatment System
by Stefan Sterlepper, Marcus Fischer, Johannes Claßen, Verena Huth and Stefan Pischinger
Energies 2021, 14(23), 8166; https://doi.org/10.3390/en14238166 - 6 Dec 2021
Cited by 42 | Viewed by 9143
Abstract
Hydrogen as carbon-free fuel is a very promising candidate for climate-neutral internal combustion engine operation. In comparison to other renewable fuels, hydrogen does obviously not produce CO2 emissions. In this work, two concepts of hydrogen internal combustion engines (H2-ICEs) are [...] Read more.
Hydrogen as carbon-free fuel is a very promising candidate for climate-neutral internal combustion engine operation. In comparison to other renewable fuels, hydrogen does obviously not produce CO2 emissions. In this work, two concepts of hydrogen internal combustion engines (H2-ICEs) are investigated experimentally. One approach is the modification of a state-of-the-art gasoline passenger car engine using hydrogen direct injection. It targets gasoline-like specific power output by mixture enrichment down to stoichiometric operation. Another approach is to use a heavy-duty diesel engine equipped with spark ignition and hydrogen port fuel injection. Here, a diesel-like indicated efficiency is targeted through constant lean-burn operation. The measurement results show that both approaches are applicable. For the gasoline engine-based concept, stoichiometric operation requires a three-way catalyst or a three-way NOX storage catalyst as the primary exhaust gas aftertreatment system. For the diesel engine-based concept, state-of-the-art selective catalytic reduction (SCR) catalysts can be used to reduce the NOx emissions, provided the engine calibration ensures sufficient exhaust gas temperature levels. In conclusion, while H2-ICEs present new challenges for the development of the exhaust gas aftertreatment systems, they are capable to realize zero-impact tailpipe emission operation. Full article
(This article belongs to the Special Issue Hydrogen-Fuelled Spark-Ignition Engines)
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22 pages, 881 KiB  
Article
The Challenges of Poland’s Energy Transition
by Sylwia Mrozowska, Jan A. Wendt and Krzysztof Tomaszewski
Energies 2021, 14(23), 8165; https://doi.org/10.3390/en14238165 - 6 Dec 2021
Cited by 27 | Viewed by 5520
Abstract
The ongoing climate changes necessitate an effective climate policy. The energy transition is now an important topic and problem, especially in Poland. (1) The undertaken analysis of the problem of energy transition is important for political, social and technological reasons. Political, because it [...] Read more.
The ongoing climate changes necessitate an effective climate policy. The energy transition is now an important topic and problem, especially in Poland. (1) The undertaken analysis of the problem of energy transition is important for political, social and technological reasons. Political, because it shows the weakness of the implementation of Polish energy policy in regards to climate change. Social, because energy transition will bring about significant social changes in the largest industrial region of Poland. Technological, as the departure from fossil fuels requires the introduction of other sources of energy on a massive scale, for which Poland is not prepared. The aim of the study was to critically analyse the activities to date in the field of energy transition in Poland. The second goal of the analysis was an attempt to answer the question of whether the process of energy transition and achieving the goals set in the EU’s European Green Deal are possible at all until 2050. (2) To achieve the goals, the system method and the decision-making method were primarily used. These methods allowed for an examination of the main determinants of the Polish energy transformation. (3) The main results include the confirmation, contrary to the announcements of the Polish government, that despite the adoption in Poland of the strategy “Poland’s energy policy until 2040”, the effective implementation of the energy transition before 2050 is not only very difficult, but may even be impossible to implement in the assumed time. This is due to political, economic, social and technological conditions. Coal energy is outdated, expensive and ineffective. Due to natural conditions, wind energy is not able to meet the energy demand of the industry. The development of nuclear energy is only in the planning phase. (4) To sum up, in the next thirty years, Poland will not be able to achieve the assumed effects of the energy transition, which is in contradiction with the official declaration of the government. Full article
(This article belongs to the Collection Feature Papers in Energy, Environment and Well-Being)
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12 pages, 10738 KiB  
Article
Melting and Heat Transfer Characteristics of Urea Water Solution According to a Heating Module’s Operating Conditions in a Frozen Urea Tank
by Byeong Gyu Jeong, Kwang Chul Oh and Seong Uk Jang
Energies 2021, 14(23), 8164; https://doi.org/10.3390/en14238164 - 6 Dec 2021
Cited by 1 | Viewed by 2663
Abstract
The urea-selective catalytic reduction (SCR) system, a nitrogen oxide reduction device for diesel vehicles, is a catalytic system that uses urea water solution (UWS) as a reducing agent. This system has a relatively wide range of operating temperatures. However, the freezing point of [...] Read more.
The urea-selective catalytic reduction (SCR) system, a nitrogen oxide reduction device for diesel vehicles, is a catalytic system that uses urea water solution (UWS) as a reducing agent. This system has a relatively wide range of operating temperatures. However, the freezing point of the reducing urea solution used in this system is −11 °C. When the ambient temperature dips below this freezing point in winter, the solution may freeze. Therefore, it is important to understand the melting characteristics of frozen UWS in relation to the operating conditions of the heating device to supply the minimum amount of aqueous solution required by the system in the initial stage of normal operation and startup of the urea–SCR system. In this study, we artificially froze a liquid solution by placing it along with a heating module in an acrylic chamber to simulate a urea solution tank. Two types of heating modules (P120 and P160) consisting of two heating elements and heat transfer bodies were used to melt the frozen solution. The melting characteristics of the frozen solution were observed, for example, changes in the temperature distribution around the heating module and the cross-sectional melting shape with the passage of time since the start of the power supply to the heating module. The shape of melting around the heating module differed depending on the level of UWS relative to the heater inside the urea tank. In case 1, it melted in a wide shape with an open top, and in case 2, it melted in a closed shape. This shape change was attributed to the formation of internal gaseous space due to volume reduction during melting and the heat transfer characteristics of the fluid and solid substances. Full article
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