Next Issue
Volume 14, July-1
Previous Issue
Volume 14, June-1
energies-logo

Journal Browser

Journal Browser

Energies, Volume 14, Issue 12 (June-2 2021) – 355 articles

Cover Story (view full-size image): When developing a sustainability plan in a complex and heavily urbanized territory, one of the most relevant options available is installing rooftop photovoltaic (PV) panels. This study develops an approach based on a cluster analysis of the urban/morphological characteristics of the municipalities. Once a clear group diversification is obtained, the roof surface of the center of gravity of each cluster is extrapolated to all similar settlements. This, together with the information of local solar irradiation, allowed us to compute each cluster’s potential solar energy production and its capability to respond to the local energy demand, a key parameter to decide about the possibility of a local smart electricity network. Finally, the emissions avoided thanks to solar PV development are computed in terms of carbon dioxide and other relevant pollutants. View this paper
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
Article
Neighborhood Energy Modeling and Monitoring: A Case Study
Energies 2021, 14(12), 3716; https://doi.org/10.3390/en14123716 - 21 Jun 2021
Cited by 1 | Viewed by 1097
Abstract
Cities and nations worldwide are pledging to energy and carbon neutral objectives that imply a huge contribution from buildings. High-performance targets, either zero energy or zero carbon, are typically difficult to be reached by single buildings, but groups of properly-managed buildings might reach [...] Read more.
Cities and nations worldwide are pledging to energy and carbon neutral objectives that imply a huge contribution from buildings. High-performance targets, either zero energy or zero carbon, are typically difficult to be reached by single buildings, but groups of properly-managed buildings might reach these ambitious goals. For this purpose we need tools and experiences to model, monitor, manage and optimize buildings and their neighborhood-level systems. The paper describes the activities pursued for the deployment of an advanced energy management system for a multi-carrier energy grid of an existing neighborhood in the area of Milan. The activities included: (i) development of a detailed monitoring plan, (ii) deployment of the monitoring plan, (iii) development of a virtual model of the neighborhood and simulation of the energy performance. Comparisons against early-stage energy monitoring data proved promising and the generation system showed high efficiency (EER equal to 5.84), to be further exploited. Full article
(This article belongs to the Special Issue Advanced Buildings Thermal Monitoring)
Show Figures

Figure 1

Article
Absorption Power and Cooling Combined Cycle with an Aqueous Salt Solution as a Working Fluid and a Technically Feasible Configuration
Energies 2021, 14(12), 3715; https://doi.org/10.3390/en14123715 - 21 Jun 2021
Viewed by 699
Abstract
Combined systems for power production and thermally activated cooling have a high potential for improving the efficiency and utilisation of thermal systems. In this regard, various configurations have been proposed and are comprehensively reviewed. They are primarily based on absorption systems and the [...] Read more.
Combined systems for power production and thermally activated cooling have a high potential for improving the efficiency and utilisation of thermal systems. In this regard, various configurations have been proposed and are comprehensively reviewed. They are primarily based on absorption systems and the implementation of multiple levels of complexity and flexibility. The configuration of the absorption power and cooling combined cycle proposed herein has wide commercial applicability owing to its simplicity. The configuration of the components is not new. However, the utilisation of aqueous salt solutions, the comparison with ammonia chiller and with absorption power cycles, the focus on parameters that are important for real-life applications, and the comparison of the performances for constant heat input and waste heat recovery are novel. The proposed cycle is also compared with a system based on the organic Rankine cycle and vapour compression cycle. An investigation of its performance proves that the system is suitable for a given range of boundary conditions from a thermodynamic standpoint, as well as in terms of system complexity and technical feasibility. New possibilities with regard to added power production have the potential to improve the economics and promote the use of absorption chiller systems. Full article
(This article belongs to the Special Issue Alternative and Emerging Cooling and Heating Technologies)
Show Figures

Graphical abstract

Article
Comparison of Consumption and Renewable Sources of Energy in European Union Countries—Sectoral Indicators, Economic Conditions and Environmental Impacts
Energies 2021, 14(12), 3714; https://doi.org/10.3390/en14123714 - 21 Jun 2021
Cited by 6 | Viewed by 859
Abstract
The use of energy is a precondition for global economic and civilisational development. However, the growing demand for energy is depleting traditional energy resources and, most importantly, causing environmental pollution, mainly through the emission of greenhouse gases. As energy is necessary for the [...] Read more.
The use of energy is a precondition for global economic and civilisational development. However, the growing demand for energy is depleting traditional energy resources and, most importantly, causing environmental pollution, mainly through the emission of greenhouse gases. As energy is necessary for the functioning of all sectors of the economy, such as industry, services, transport as well as households, these sectors are the largest contributors to energy consumption. Renewable energy sources are an alternative to generating energy from conventional fossil fuels. The main objective of this paper was to determine and compare the level, trends and variation in energy consumption by different economic sectors in countries of the European Union in 2010–2019. An analysis of the share of renewable energy consumption in different economic sectors was also carried out, as well as an assessment of the relationship of these indicators with the level of economic development of the countries and environmental impacts in the form of greenhouse gas emissions from energy consumption. To explore the topics under discussion, a dozen of indicators have been considered in the article. The source of empirical data collected was the European Statistical Office. The researched period covered the years 2010–2019. The empirical data was statistically analysed. The article considers changes in the values of the studied indicators, differentiation between countries and the results of correlation and regression analysis. As shown by the data from 2010–2019, the countries of the European Union vary significantly in respect of primary and final energy consumption. The highest final energy consumption occurs in the transport sector, followed by slightly lower consumption in the industrial sector and households sector and the lowest but also significant consumption in the commercial and public services sector. Since 2010, total primary and final energy consumption has decreased in the EU (27) countries. Total energy consumption and consumption by individual sectors in modern economies of the EU (27) countries are reflected on the one hand in economic development and on the other—in exacerbation of adverse climate changes. Therefore, all EU Member States, aware of their energy consumption and their own contribution to environmental pollution, should take effective and sustainable corrective action in this area as soon as possible. Full article
(This article belongs to the Special Issue Strategic Planning and Management in Energy)
Show Figures

Figure 1

Article
The Effect of Ceiling Heating and Mechanical Ventilation on Thermal Comfort
Energies 2021, 14(12), 3712; https://doi.org/10.3390/en14123712 - 21 Jun 2021
Cited by 1 | Viewed by 611
Abstract
In the case of public buildings with ceiling heating and mechanical ventilation, radiant temperature asymmetry caused by the warm ceiling and draught occur simultaneously. The currently available literature does not offer an exhaustive description of the comfort conditions resulting from such a thermal [...] Read more.
In the case of public buildings with ceiling heating and mechanical ventilation, radiant temperature asymmetry caused by the warm ceiling and draught occur simultaneously. The currently available literature does not offer an exhaustive description of the comfort conditions resulting from such a thermal environment. This research focuses on complementing the available knowledge, using instrumental measurements, as well as subject measurements carried out on 20 individuals. Relying on these measurements, the purpose of the research is to support the understanding of the combined mechanisms of action of the two local discomfort parameters. The main result of this research is that, if the predicted percentage dissatified is less than 6%, the radiant temperature asymmetry is in an interval of 5–15 °C, and the draught rate is 15% or 25%, the actual mean vote and the predicted mean vote values differ significantly, and the actual mean vote is always lower, with a few exceptions. In addition, the research highlights the changes of the actual mean vote caused by raising the draught rate from 15% to 25%, in the presence of radiant temperature asymmetry caused by warm ceilings. Full article
(This article belongs to the Special Issue Energy Efficiency of the Buildings)
Show Figures

Figure 1

Article
The Interconnection and Damping Assignment Passivity-Based Control Synthesis via the Optimal Control Method for Electric Vehicle Subsystems
Energies 2021, 14(12), 3711; https://doi.org/10.3390/en14123711 - 21 Jun 2021
Cited by 1 | Viewed by 606
Abstract
The interconnection between optimal control theory and the theory of energy-shaping control is described in our paper. For linear and nonlinear systems, the application of the theory of optimal control for the synthesis of parameters of energy-shaping control matrices is demonstrated in detail. [...] Read more.
The interconnection between optimal control theory and the theory of energy-shaping control is described in our paper. For linear and nonlinear systems, the application of the theory of optimal control for the synthesis of parameters of energy-shaping control matrices is demonstrated in detail. The use of a Riccati equation allows us to form an optimality criterion and to synthesize the energy-shaping control system that provides the desired transient processes. The proposed approach was applied to the synthesis of control influences for electric vehicle subsystems, such as a two-mass system and a permanent magnets synchronous motor. The results of computer simulation studies, as well as those conducted on real experimental installations, are given in this paper. Full article
(This article belongs to the Special Issue Power Processing Systems for Electric Vehicles)
Show Figures

Figure 1

Article
Gate Road Support Deformation Forecasting Based on Multivariate Singular Spectrum Analysis and Fuzzy Time Series
Energies 2021, 14(12), 3710; https://doi.org/10.3390/en14123710 - 21 Jun 2021
Viewed by 618
Abstract
Underground mining engineers and planners in our country are faced with extremely difficult working conditions and a continuous shortage of money. Production disruptions are frequent and can sometimes last more than a week. During this time, gate road support is additionally exposed to [...] Read more.
Underground mining engineers and planners in our country are faced with extremely difficult working conditions and a continuous shortage of money. Production disruptions are frequent and can sometimes last more than a week. During this time, gate road support is additionally exposed to rock stress and the result is its progressive deformation and the loss of functionality of gate roads. In such an environment, it is necessary to develop a low-cost methodology to maintain a gate road support system. For this purpose, we have developed a model consisting of two main phases. The first phase is related to support deformation monitoring, while the second phase is related to data analysis. To record support deformations over a defined time horizon we use laser scanning technology together with multivariate singular spectrum analysis to conduct data processing and forecasting. Fuzzy time series is applied to classify the intensity of displacements into several independent groups (clusters). Full article
(This article belongs to the Special Issue Mining Innovation)
Show Figures

Figure 1

Article
Management of the Energy and Economic Potential of Nuclear Waste Use
Energies 2021, 14(12), 3709; https://doi.org/10.3390/en14123709 - 21 Jun 2021
Cited by 1 | Viewed by 896
Abstract
Recently, issues related to the effects (benefit or harm) of processing nuclear waste and its further use as fuel have been increasingly often raised in the scientific discussion. In this regard, the research aims to investigate issues related to the assessment of the [...] Read more.
Recently, issues related to the effects (benefit or harm) of processing nuclear waste and its further use as fuel have been increasingly often raised in the scientific discussion. In this regard, the research aims to investigate issues related to the assessment of the economic potential of nuclear waste use, as well as the cooperation between states in the context of the reduction of risks associated with nuclear waste storage and processing. The research methodology is based on an integrated approach, including statistical, factor analysis, and the proposed system of performance indicators for managing spent nuclear fuel use. The research was carried out on the basis of materials from Russia and the EU countries. In the course of the study, a model of cooperation between states has been developed (based on the example of technologies and methods of processing nuclear waste used in the EU and Russia) according to the nuclear waste (spent nuclear fuel) management algorithm. The model considers the risks and threats associated with ecology and safety. The developments and other results described in the study should be used in further research devoted to the use of nuclear waste as heat-producing elements. Full article
(This article belongs to the Special Issue Management and Technology for Energy Efficiency Development)
Show Figures

Figure 1

Article
An Assessment of the Energy Poverty and Gender Nexus towards Clean Energy Adoption in Rural South Africa
Energies 2021, 14(12), 3708; https://doi.org/10.3390/en14123708 - 21 Jun 2021
Cited by 4 | Viewed by 785
Abstract
South Africa has about 2.5 million households without electricity access, most of which are located in rural areas and urban informal settlements. The nexus of energy poverty and gender is at play in the affected communities, as women and girls are culturally stereotyped [...] Read more.
South Africa has about 2.5 million households without electricity access, most of which are located in rural areas and urban informal settlements. The nexus of energy poverty and gender is at play in the affected communities, as women and girls are culturally stereotyped with the task of collecting unclean fuels (e.g., firewood) and using these for their households’ energy demands. Therefore, this study prioritized rural women and girls as respondents in the provinces most affected by gendered energy poverty (GEP) in the country. The study was carried out in selected rural unelectrified areas of Limpopo, Mpumalanga, and KwaZulu-Natal provinces using structured interviews. The study revealed that GEP in the rural areas has exposed women and girls living there to security concerns, health hazards, premature death, domestic fire accidents, time poverty, income poverty, illiteracy, drudgery in households and farm tasks, etc., at different levels of severity. It also showed the effects of perceptions, age, income, and culture on the choice of energy use among the respondents. Mitigation strategies against GEP in rural South African communities through clean energy adoption are also proposed in this paper. Full article
(This article belongs to the Special Issue The Nexus among Sustainable Development Goals and Clean Energies)
Show Figures

Figure 1

Article
Research on the Optimized Operation of Hybrid Wind and Battery Energy Storage System Based on Peak-Valley Electricity Price
Energies 2021, 14(12), 3707; https://doi.org/10.3390/en14123707 - 21 Jun 2021
Cited by 2 | Viewed by 625
Abstract
The combined operation of hybrid wind power and a battery energy storage system can be used to convert cheap valley energy to expensive peak energy, thus improving the economic benefits of wind farms. Considering the peak–valley electricity price, an optimization model of the [...] Read more.
The combined operation of hybrid wind power and a battery energy storage system can be used to convert cheap valley energy to expensive peak energy, thus improving the economic benefits of wind farms. Considering the peak–valley electricity price, an optimization model of the economic benefits of a combined wind–storage system was developed. A charging/discharging strategy of the battery storage system was proposed to maximize the economic benefits of the combined wind–storage system based on the forecast wind power. The maximal economic benefits were obtained based on scenario analysis, taking into account the wind-power forecast error, and costs associated with the loss of battery life, battery operation, and maintenance. Case simulation results highlight the effectiveness of the proposed model. The results show that the hybrid wind–storage system is not only able to convert cheap electricity in the valley period into expensive electricity in the peak period, thus resulting in higher economic benefits, but can also balance the deviation between actual output and plans for the wind power generator to decrease the loss penalty. The analyzed examples show that, following an increase in the deviation of the forecast wind power, the profit of the combined wind–storage system can increase by up to 45% using the charging/discharging strategy, compared with a wind farm that does not utilize energy storage. In addition, the profit of the combined wind–storage system can increase by up to 16% compared with separate systems, following an increase in the deviation penalty deviation coefficient. Full article
Show Figures

Figure 1

Article
An Energy Efficiency Estimation Procedure for Small Wind Turbines at Chosen Locations in Poland
Energies 2021, 14(12), 3706; https://doi.org/10.3390/en14123706 - 21 Jun 2021
Cited by 1 | Viewed by 782
Abstract
Contrary to the extensive amount of research on large wind turbines, substantial analyses of small wind turbines are still rare. In the present study, the wind energy potential of three locations in Poland is analyzed using real wind data from a five-year period [...] Read more.
Contrary to the extensive amount of research on large wind turbines, substantial analyses of small wind turbines are still rare. In the present study, the wind energy potential of three locations in Poland is analyzed using real wind data from a five-year period and the parameters of the selected turbine model. Appropriate simulations are performed to assess the energy efficiency of the analyzed investments at a coastal, foothill, or lowland site. According to the results, the most favorable location for a small wind turbine is the coastal site (wind zone I). The payback time at this location is approximately 13 years, whereas the payback times at the other two analyzed are more than 3 times longer. The payback periods for the latter locations significantly exceed the estimated lifetime of the wind turbine, ruling out their economic viability. The cost of electricity generation varies greatly, from 0.16 EUR/kWh at the coastal location to 0.71 EUR/kWh at the lowland location. These results provide a reference for developing more efficient solutions, such as the use of a turbine with a shielded rotor, which can increase the power of the turbine by approximately 2.5 times. Full article
(This article belongs to the Special Issue Economic Analysis of Wind Power in the EU)
Show Figures

Graphical abstract

Article
Research on Temperature Monitoring Method of Cable on 10 kV Railway Power Transmission Lines Based on Distributed Temperature Sensor
Energies 2021, 14(12), 3705; https://doi.org/10.3390/en14123705 - 21 Jun 2021
Cited by 3 | Viewed by 679
Abstract
Railway power transmission lines (RPTL) are power lines that provide nontraction power supply for railways, such as communications and signals along the railway. With the advancement of technology, power cables are being used more and more widely. Operational experience has shown that during [...] Read more.
Railway power transmission lines (RPTL) are power lines that provide nontraction power supply for railways, such as communications and signals along the railway. With the advancement of technology, power cables are being used more and more widely. Operational experience has shown that during the operation of power cables, abnormal heat is often caused by fault factors such as poor joint crimping and severe partial discharge caused by insulation defects, leading to cable burns in extreme cases. Distributed temperature sensors (DTS), a kind of spatial continuous temperature sensor using sensing optical fiber, can measure the temperature along the cable and are expected to realize on-line monitoring and positioning of cable heating faults. This paper first builds a finite element model of the cable under various faults to calculate the distribution characteristics of the temperature field of the faulty cable. Then the results are verified through experiments with the external sensing fiber and the artificially manufactured heating points of the cable. The conclusions show that it is feasible to use a distributed sensing fiber to monitor and locate the heating fault of power cable. Full article
(This article belongs to the Topic Innovative Techniques for Smart Grids)
Show Figures

Figure 1

Article
Regional Climate Change Competitiveness—Modelling Approach
Energies 2021, 14(12), 3704; https://doi.org/10.3390/en14123704 - 21 Jun 2021
Cited by 1 | Viewed by 569
Abstract
The article deals with the competitiveness of regions in the face of climate change. The aim was to present the concept of measuring the Regional Climate Change Competitiveness Index. We used a comparative and logical analysis of the concept of regional competitiveness and [...] Read more.
The article deals with the competitiveness of regions in the face of climate change. The aim was to present the concept of measuring the Regional Climate Change Competitiveness Index. We used a comparative and logical analysis of the concept of regional competitiveness and heuristic conceptual methods to construct the index and measurement scale. The structure of the index includes six broad sub-indexes: Basic, Natural, Efficiency, Innovation, Sectoral, Social, and 89 indicators. A practical application of the model was presented for the Mazowieckie province in Poland. This allowed the region’s performance in the context of climate change to be presented, and regional weaknesses in the process of adaptation to climate change to be identified. The conclusions of the research confirm the possibility of applying the Regional Climate Change Competitiveness Index in the economic analysis and strategic planning. The presented model constitutes one of the earliest tools for the evaluation of climate change competitiveness at a regional level. Full article
(This article belongs to the Special Issue Economics and Finance of Energy and Climate Change)
Show Figures

Figure 1

Article
Two-Stage Biodiesel Synthesis from Used Cooking Oil with a High Acid Value via an Ultrasound-Assisted Method
Energies 2021, 14(12), 3703; https://doi.org/10.3390/en14123703 - 21 Jun 2021
Cited by 1 | Viewed by 572
Abstract
In this study, ultrasound was used to accelerate two-stage (esterification–transesterification) catalytic synthesis of biodiesel from used cooking oil, which originally had a high acid value (4.35 mg KOH/g). In the first stage, acid-catalyzed esterification reaction conditions were developed with a 9:1 methanol/oil molar [...] Read more.
In this study, ultrasound was used to accelerate two-stage (esterification–transesterification) catalytic synthesis of biodiesel from used cooking oil, which originally had a high acid value (4.35 mg KOH/g). In the first stage, acid-catalyzed esterification reaction conditions were developed with a 9:1 methanol/oil molar ratio, sulfuric acid dosage at 2 wt %, and a reaction temperature of 60 °C. Under ultrasound irradiation for 40 min, the acid value was effectively decreased from 4.35 to 1.67 mg KOH/g, which was decreased to a sufficient level (<2 mg KOH/g) to avoid the saponification problem for the subsequent transesterification reaction. In the following stage, base-catalyzed transesterification reactions were carried out with a 12:1 methanol/oil molar ratio, a sodium hydroxide dosage of 1 wt %, and a reaction temperature of 65 °C. Under ultrasound-assisted transesterification for 40 min, the conversion rate of biodiesel reached 97.05%, which met the requirement of EN 14214 standard, i.e., 96.5% minimum. In order to evaluate and explore the improvement of the ultrasound-assisted two-stage (esterification–transesterification) process in shortening the reaction time, additional two-stage biodiesel synthesis experiments using the traditional mechanical stirring method under the optimal conditions were further carried out in this study. It was found that, under the same optimal conditions, using the ultrasound-assisted two-stage process, the total reaction time was significantly reduced to only 80 min, which was much shorter than the total time required by the conventional method of 140 min. It is worth noting that compared with the traditional method without ultrasound, the intensification of the ultrasound-assisted two-stage process significantly shortened the total time from 140 min to 80 min, which is a reduction of 42.9%. It was concluded that the ultrasound-assisted two-stage (esterification–transesterification) catalytic process is an effective and time-saving method for synthesizing biodiesel from used cooking oil with a high acid value. Full article
(This article belongs to the Special Issue Selected Papers from TIKI IEEE ICICE 2019&ICASI 2020 in Energies)
Show Figures

Figure 1

Article
Offshore Wind Potential of West Central Taiwan: A Case Study
Energies 2021, 14(12), 3702; https://doi.org/10.3390/en14123702 - 21 Jun 2021
Viewed by 668
Abstract
In this study, we present the wind distributions from a long-term offshore met mast and a novel approach based on the measure–correlate–predict (MCP) method from short-term onshore-wind-turbine data. The annual energy production (AEP) and capacity factors (CFs) of one onshore and four offshore [...] Read more.
In this study, we present the wind distributions from a long-term offshore met mast and a novel approach based on the measure–correlate–predict (MCP) method from short-term onshore-wind-turbine data. The annual energy production (AEP) and capacity factors (CFs) of one onshore and four offshore wind-turbine generators (WTG) available on the market are evaluated on the basis of wind-distribution analysis from both the real met mast and the MCP method. Here, we also consider the power loss from a 4-month light detection and ranging (LiDAR) power-curve test on an onshore turbine to enhance the accuracy of further AEP and CF evaluations. The achieved Weibull distributions could efficiently represent the probability distribution of wind-speed variation, mean wind speed (MWS), and both the scale and shape parameters of Weibull distribution in Taiwan sites. The power-loss effect is also considered when calculating the AEPs and CFs of different WTGs. Successful offshore wind development requires (1) quick, accurate, and economical harnessing of a wind resource and (2) selection of the most suitable and efficient turbine for a specific offshore site. Full article
(This article belongs to the Topic Exergy Analysis and Its Applications)
Show Figures

Figure 1

Article
Three-Phase PWM Inverter for Isolated Grid-Connected Renewable Energy Applications
Energies 2021, 14(12), 3701; https://doi.org/10.3390/en14123701 - 21 Jun 2021
Cited by 1 | Viewed by 812
Abstract
This paper proposes a three-phase isolated flyback inverter (IFBI) for single-stage grid-tied solar PV applications, considering a simple sinusoidal pulse-width modulation (SPWM) scheme. The proposed single-stage inverter employs a reduced passive elements count by considering three input-parallel output-differential (IPOD) flyback converter modules. Additionally, [...] Read more.
This paper proposes a three-phase isolated flyback inverter (IFBI) for single-stage grid-tied solar PV applications, considering a simple sinusoidal pulse-width modulation (SPWM) scheme. The proposed single-stage inverter employs a reduced passive elements count by considering three input-parallel output-differential (IPOD) flyback converter modules. Additionally, a single small size LC-input low-pass filter is utilized at the input paralleling point for ripple-free input current operation, which is essential in grid-connected renewable energy applications. In addition, a mathematical model of the IFBI is presented to confirm the existence of its low-order harmonic components. A simple PI controller-based control scheme, considering only two loops and five sensors, is used to control the proposed grid-tied IFBI. Continuous modulation scheme (CMS) combined with SPWM is used to diminish the low-frequency harmonic components. Moreover, a simple selective harmonic elimination (SHE) loop is used for second-order harmonic components (SOHC) elimination from grid-injected currents. The SHE has decreased the SOHC from 43% to 0.96%, which improves the grid current THD from 39% to 3.65%, to follow the IEEE harmonic standard limits. Additionally, the harmonic elimination technique decreases the circulating power between the inverter paralleled modules, which enhances the grid currents power factor. The proposed inverter is verified through a grid-connected 200 V, 1.6 kW, 60 Hz experimental prototype, and the switching frequency is 50 kHz. TMS-based DSP controller is used to control the grid-injected power to follow the reference power set-point. Full article
Show Figures

Figure 1

Article
Amplitude-Preserved Wave Equation: An Example to Image the Gas Hydrate System
Energies 2021, 14(12), 3700; https://doi.org/10.3390/en14123700 - 21 Jun 2021
Viewed by 525
Abstract
Natural gas hydrate is an important energy source. Therefore, it is extremely important to provide a clear imaging profile to determine its distribution for energy exploration. In view of the problems existing in conventional migration methods, e.g., the limited imaging angles, we proposed [...] Read more.
Natural gas hydrate is an important energy source. Therefore, it is extremely important to provide a clear imaging profile to determine its distribution for energy exploration. In view of the problems existing in conventional migration methods, e.g., the limited imaging angles, we proposed to utilize an amplitude-preserved one-way wave equation migration based on matrix decomposition to deal with primary and multiple waves. With respect to seismic data gathered at the Chilean continental margin, a conventional processing flow to obtain seismic records with a high signal-to-noise ratio is introduced. Then, the imaging results of the conventional and amplitude-preserved one-way wave equation migration methods based on primary waves are compared, to demonstrate the necessity of implementing amplitude-preserving migration. Moreover, a simple two-layer model is imaged by using primary and multiple waves, which proves the superiority of multiple waves in imaging compared with primary waves and lays the foundation for further application. For the real data, the imaging sections of primary and multiple waves are compared. We found that multiple waves are able to provide a wider imaging illumination while primary waves fail to illuminate, especially for the imaging of bottom simulating reflections (BSRs), because multiple waves have a longer travelling path and carry more information. By imaging the actual seismic data, we can make a conclusion that the imaging result generated by multiple waves can be viewed as a supplementary for the imaging result of primary waves, and it has some guiding values for further hydrate and in general shallow gas exploration. Full article
(This article belongs to the Special Issue Natural Gas Hydrates as Energy Resource: Prospects and Challenges)
Show Figures

Figure 1

Article
Analysis and Predicting the Energy Consumption of Low-Pressure Carburising Processes
Energies 2021, 14(12), 3699; https://doi.org/10.3390/en14123699 - 21 Jun 2021
Viewed by 497
Abstract
The monitoring of the performance of heat treatment equipment has been the subject of a number of studies. This paper proposes and explores a new study on the models—and the monitoring thereof—for predicting the energy intensity of low-pressure carburisation processes using the DeepCaseMaster [...] Read more.
The monitoring of the performance of heat treatment equipment has been the subject of a number of studies. This paper proposes and explores a new study on the models—and the monitoring thereof—for predicting the energy intensity of low-pressure carburisation processes using the DeepCaseMaster Evolution soaking furnace. For research purposes, 18 carburising experiments were performed with different carbon layers, at different input parameters, such as the number of cycles, time, temperature and average carburising pressure. Based on the research experiments conducted and statistical analysis, the influence of individual parameters on the energy consumption of the pump and heating systems was determined. Moreover, the models were verified on real data of low-pressure carburising processes. The innovativeness of the proposed solution is a combination of two areas: (1) defining and measurement of the parameters of the low-pressure carburising process; and (2) predicting the energy consumption of low-pressure carburising processes using correlation and regression analyses. The possibilities of using the results of this research in practice are demonstrated convincingly. Full article
Show Figures

Figure 1

Article
An Eco-Friendly Gas Insulated Transformer Design
Energies 2021, 14(12), 3698; https://doi.org/10.3390/en14123698 - 21 Jun 2021
Viewed by 686
Abstract
Electricity companies around the world are constantly seeking ways to provide electricity more safely and efficiently while reducing the negative impact on the environment. Mineral oils have been the most popular transformer insulation, having excellent electrical insulating properties, but have many problems such [...] Read more.
Electricity companies around the world are constantly seeking ways to provide electricity more safely and efficiently while reducing the negative impact on the environment. Mineral oils have been the most popular transformer insulation, having excellent electrical insulating properties, but have many problems such as high flammability, significant cleaning problems, and are toxic to fish and wildlife. This paper presents an alternative approach to mineral oil: a transformer design that is clean and provides better performance and environmental benefits. A 50 kVA, 34.5/0.4 kV gas insulated distribution transformer was designed and evaluated using the COMSOL Multiphysics environment. R410A was used as insulation material. R410A is a near-azeotropic mixture of difluoromethane (CH2F2, called R-32) and pentafluoro ethane (C2HF5, called R-125), which is used as a refrigerant in air conditioning applications. It has excellent properties including environmentally friendly, no-ozone depletion, low greenhouse effect, non-explosive and non-flammable, First, the breakdown voltage of the selected gas was determined. The electrostatic and thermal properties of the R410A gas insulated transformer were investigated in the COMSOL environment. The simulation results for the performance of oil and SF6 gas insulated transformers using the same model were compared. The gas-insulated transformer is believed to have equivalent performance and is an environmentally friendly alternative to current oil-based transformers. Full article
(This article belongs to the Special Issue State-of-the-Art Energy Related Technologies in Canada 2020-2021)
Show Figures

Figure 1

Article
Analysis of Market-Ready Traffic Sign Recognition Systems in Cars: A Test Field Study
Energies 2021, 14(12), 3697; https://doi.org/10.3390/en14123697 - 21 Jun 2021
Cited by 2 | Viewed by 702
Abstract
Advanced Driver Assistance System (ADAS) represents a collection of vehicle-based intelligent safety systems. One in particular, Traffic Sign Recognition System (TSRS), is designed to detect and interpret roadside information in the form of signage. Even though TSRS has been on the market for [...] Read more.
Advanced Driver Assistance System (ADAS) represents a collection of vehicle-based intelligent safety systems. One in particular, Traffic Sign Recognition System (TSRS), is designed to detect and interpret roadside information in the form of signage. Even though TSRS has been on the market for more than a decade now, the available ones differ in hardware and software solutions they use, as well as in quantity and typology of signs they recognize. The aim of this study is to determine whether differences between detection and readability accuracy of market-ready TSRS exist and to what extent, as well as how different levels of “graphical changes” on the signs affect their accuracy. For this purpose, signs (“speed limit” and “prohibition of overtaking”) were placed on a test field and 17 vehicles from 14 different car brands underwent testing. Overall, the results showed that sign detection and readability by TSRS differ between car brands and that even small changes in the design of signs can drastically affect TSRS accuracy. Even in a controlled environment where no sign has been altered, there has been a 5% margin of misread signs. Full article
(This article belongs to the Special Issue Advances in Automated Driving Systems)
Show Figures

Figure 1

Article
Functional and Operational Requirements to Be Fulfilled by Conical Picks Regarding Their Wear Rate and Investment Costs
Energies 2021, 14(12), 3696; https://doi.org/10.3390/en14123696 - 21 Jun 2021
Cited by 2 | Viewed by 626
Abstract
User’s choices of conical picks currently involve specifying their material and geometric parameters (functional requirements), incorporating the place and conditions of their work (operational requirements). The selection is usually made based on solely one criterion, which is the price. Thus, at the stage [...] Read more.
User’s choices of conical picks currently involve specifying their material and geometric parameters (functional requirements), incorporating the place and conditions of their work (operational requirements). The selection is usually made based on solely one criterion, which is the price. Thus, at the stage of both purchase and operation, the quality of picks, as well as their matching for a specific machine, are not assessed. The problem of defining whether the producer has fulfilled the user’s requirements arises only when the user questions the picks’ quality. Analysis of this problem has resulted in developing assumptions, concepts and research procedures based on the cutting process requirements. The procedure allows conducting tests to determine the geometric parameters of a pick, the type of material of the pick body and WC-Co insert, as well as the pick wear rate (intensity). The C2 index describes the wear rate (intensity)—the smaller its value, the slower the pick’s wear. Laboratory tests were carried out at the AGH University of Science and Technology in Kraków, Poland. Following the developed method and procedure, the quality of picks was precisely and unambiguously assessed. The C2 index, apart from testing the quality of picks, was also used to forecast their wear. Based on the C2 index, a method is proposed to estimate the wear rate of conical picks provided by different manufacturers and determine the acceptable unit price and operating costs. Thus, it is possible and reasonable to precisely define the investment requirements and appropriately select the pick. Relevant tests were carried out for eight different types of conical picks used in roadheaders, longwall shearers and shaft-boring roadheaders. Full article
(This article belongs to the Special Issue The IMTech 2021 Innovative Mining Technologies)
Show Figures

Figure 1

Article
Overview of a Theory for Planning Similar Experiments with Different Fluids at Supercritical Pressure
Energies 2021, 14(12), 3695; https://doi.org/10.3390/en14123695 - 21 Jun 2021
Cited by 1 | Viewed by 449
Abstract
The recent advancements achieved in the development of a fluid-to-fluid similarity theory for heat transfer with fluids at supercritical pressures are summarised. The prime mover for the development of the theory was the interest in the development of Supercritical Water nuclear Reactors (SCWRs) [...] Read more.
The recent advancements achieved in the development of a fluid-to-fluid similarity theory for heat transfer with fluids at supercritical pressures are summarised. The prime mover for the development of the theory was the interest in the development of Supercritical Water nuclear Reactors (SCWRs) in the frame of research being developed worldwide; however, the theory is general and can be applied to any system involving fluids at a supercritical pressure. The steps involved in the development of the rationale at the basis of the theory are discussed and presented in a synthetic form, highlighting the relevance of the results achieved so far and separately published elsewhere, with the aim to provide a complete overview of the potential involved in the application of the theory. The adopted rationale, completely different from the ones in the previous literature on the subject, was based on a specific definition of similarity, aiming to achieve, as much as possible, similar distributions of enthalpies and fluid densities in a duct containing fluids at a supercritical pressure. This provides sufficient assurance that the complex phenomena governing heat transfer in the addressed conditions, which heavily depend on the changes in fluid density and in other thermophysical properties along and across the flow duct, are represented in sufficient similarity. The developed rationale can be used for planning possible counterpart experiments, with the aid of supporting computational fluid-dynamic (CFD) calculations, and it also clarifies the role of relevant dimensionless numbers in setting up semi-empirical correlations for heat transfer in these difficult conditions, experiencing normal, enhanced and deteriorated regimes. This paper is intended as a contribution to a common reflection on the results achieved so far in view of the assessment of a sufficient body of knowledge and understanding to base successful predictive capabilities for heat transfer with fluids at supercritical pressures. Full article
(This article belongs to the Special Issue Design and Safety Issues of Nuclear Plants and Installations)
Show Figures

Figure 1

Article
Simulations of Airflow in the Roof Space of a Gothic Sanctuary Using CFD Models
Energies 2021, 14(12), 3694; https://doi.org/10.3390/en14123694 - 21 Jun 2021
Cited by 1 | Viewed by 556
Abstract
For a deep understanding of the airflow in an environment of historic wooden trusses, it is necessary to analyze the object using simulation methods. To calculate the amount of air passing through the structural openings (components) using dynamic simulation, multi-zone network models based [...] Read more.
For a deep understanding of the airflow in an environment of historic wooden trusses, it is necessary to analyze the object using simulation methods. To calculate the amount of air passing through the structural openings (components) using dynamic simulation, multi-zone network models based on the simplicity of modeling the individual zones are suitable. For a more detailed analysis of airflow and temperature distribution within one space, a computational fluid dynamics (CFD) simulation model was performed. The air volume through openings and surface temperatures was adopted from the multi-zone airflow network model. By using this simulation technique during a sunny summer day four characteristic states of air movement were simulated in the attic: more intense flow at noon and at midnight caused by a large temperature difference between air and surrounding surfaces and, subsequently, less intense flow when the air was mixed up effectively. The temperature distribution in the cross-sections did not only indicate an increase in temperature with increasing height (up to 50 °C at noon) but also a temperature increase near the southern roof. The surface temperature of the masonry walls was stable (19–33 °C), while the air temperature fluctuated. The image of the flow was completed by ventilation through the tower, which acted as a solar chimney. The airflow through the door to the tower was almost 0.5 m3 s−1 at summer midnight. Full article
Show Figures

Figure 1

Article
Effects of Kaolin Addition on Mechanical Properties for Cemented Coal Gangue-Fly Ash Backfill under Uniaxial Loading
Energies 2021, 14(12), 3693; https://doi.org/10.3390/en14123693 - 21 Jun 2021
Cited by 2 | Viewed by 653
Abstract
In this investigation, six groups of cemented coal gangue-fly ash backfill (CGFB) samples with varying amounts of kaolin (0, 10, 20, 30, 40, and 50%) instead of cement are prepared, and their mechanical properties are analyzed using uniaxial compression, acoustic emission, scanning electron [...] Read more.
In this investigation, six groups of cemented coal gangue-fly ash backfill (CGFB) samples with varying amounts of kaolin (0, 10, 20, 30, 40, and 50%) instead of cement are prepared, and their mechanical properties are analyzed using uniaxial compression, acoustic emission, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The uniaxial compressive strength, peak strain, and elastic modulus of CGFB samples decreased with the kaolin content. The average uniaxial compressive strength, elastic modulus, and peak strain of CGFB samples with 10% amount of kaolin are close to that of CGFB samples with no kaolin. The contribution of kaolin hydration to the strength of CGFB sample is lower than that of cement hydration, and the hydration products such as ettringite and calcium-silicate-hydrate gel decrease, thereby reducing strength, which mainly plays a role in filling pores. The contents of kaolin affect the failure characteristics of CGFB samples, which show tensile failure accompanied by local shear failure, and the failure degree increases with the kaolin content. The porosity of the fracture surface shows a decreasing trend as a whole. When the amount of kaolin instead of cement is 10%, the mechanical properties of CGFB samples are slightly different from those of CGFB samples without kaolin, and CGFB can meet the demand of filling strength. The research results provide a theoretical basis for the application of kaolin admixture in fill mining. Full article
Show Figures

Figure 1

Article
The Sliding Window and SHAP Theory—An Improved System with a Long Short-Term Memory Network Model for State of Charge Prediction in Electric Vehicle Application
Energies 2021, 14(12), 3692; https://doi.org/10.3390/en14123692 - 21 Jun 2021
Cited by 3 | Viewed by 838
Abstract
The state of charge (SOC) prediction for an electric vehicle battery pack is critical to ensure the reliability, efficiency, and life of the battery pack. Various techniques and statistical systems have been proposed in the past to improve the prediction accuracy, reduce complexity, [...] Read more.
The state of charge (SOC) prediction for an electric vehicle battery pack is critical to ensure the reliability, efficiency, and life of the battery pack. Various techniques and statistical systems have been proposed in the past to improve the prediction accuracy, reduce complexity, and increase adaptability. Machine learning techniques have been vigorously introduced in recent years, to be incorporated into the existing prediction algorithms, or as a stand-alone system, with a large amount of recorded past data to interpret the battery characteristics, and further predict for the present and future. This paper presents an overview of the machine learning techniques followed by a proposed pre-processing technique employed as the input to the long short-term memory network (LSTM) algorithm. The proposed pre-processing technique is based on the time-based sliding window algorithm (SW) and the Shapley additive explanation theory (SHAP). The proposed technique showed improvement in accuracy, adaptability, and reliability of SOC prediction when compared to other conventional machine learning models. All the data employed in this investigation were extracted from the actual driving cycle of five different electric vehicles driven by different drivers throughout a year. The computed prediction error, as compared to the original SOC data extracted from the vehicle, was within the range of less than 2%. The proposed enhanced technique also demonstrated the feasibility and robustness of the prediction results through the persistent computed output from a random selection of the data sets, consisting of different driving profiles and ambient conditions. Full article
Show Figures

Figure 1

Article
Potential Impact of Renewable Energy on the Sustainable Development of Russian Arctic Territories
Energies 2021, 14(12), 3691; https://doi.org/10.3390/en14123691 - 21 Jun 2021
Cited by 4 | Viewed by 735
Abstract
In recent decades, there has been a positive trend in world politics in the field of promoting territories’ sustainable development. At the same time, one of the most relevant areas is to promote the transition to renewable energy sources (RES), which correspond to [...] Read more.
In recent decades, there has been a positive trend in world politics in the field of promoting territories’ sustainable development. At the same time, one of the most relevant areas is to promote the transition to renewable energy sources (RES), which correspond to one of the UN’s goals—Sustainable Development Goal 7 (SDG 7) “Ensuring universal access to affordable, reliable, sustainable and modern energy sources for all”. This article is devoted to the study of the renewable energy sources’ impact on the sustainable development of the Russian Arctic zone. The authors chose the level of carbon dioxide (CO2) emissions as an indicator reflecting the impact of RES on sustainable development, since this factor is one of the main factors for assessing trends in the activities of countries aimed at achieving progress on most of the Sustainable Development Goals of territories. The hypothesis of the relationship between the use of renewable energy sources and the achievement of progress on the Sustainable Development Goals, one of the indicators of which is the level of CO2 emissions, was tested and confirmed. An econometric analysis of panel data for 15 countries that are actively implementing the concept of sustainable development, including decarbonizing policies, was carried out, where the resulting indicator for achieving progress on the SDG was the amount of CO2 emissions. The factors influencing the resulting variable were indicators selected based on a review of existing models, as well as indicators of the Sustainable Development Goals’ achievement. Using an econometric analysis of interdependence, the indicators of progress towards the Sustainable Development Goals that are more likely to have an impact on the level of CO2 emissions were identified. These are electricity consumption, the share of renewable energy sources in the energy balance, the average per capita income of the population, and carbon intensity. Based on the results obtained, it can be concluded that renewable energy sources are a factor contributing to the achievement of progress on the Sustainable Development Goals. The results obtained are also applicable to the Arctic region, since all countries that have territories in the Arctic zone adhere to the policy of decarbonization and try to reduce the use of fossil fuels. Full article
Show Figures

Figure 1

Review
Some Key Issues in Hypersonic Propulsion
Energies 2021, 14(12), 3690; https://doi.org/10.3390/en14123690 - 21 Jun 2021
Cited by 2 | Viewed by 539
Abstract
This paper summarizes and discusses some critical aspects of flying hypersonically. The first is the L/D (lift over drag) ratio determining thrust and that in turn depends on the slenderness Küchemann’s τ parameter. This second parameter is found to depend on the relative [...] Read more.
This paper summarizes and discusses some critical aspects of flying hypersonically. The first is the L/D (lift over drag) ratio determining thrust and that in turn depends on the slenderness Küchemann’s τ parameter. This second parameter is found to depend on the relative importance of wave versus friction drag. Ultimately, all engineering drag is argued to depend on vorticity formed at the expense of the vehicle kinetic energy, thus requiring work by thrust. Different mixing strategies are discussed and shown to depend also on mechanisms forming vorticity when the regime is compressible. Supersonic combustion is briefly analyzed and found, at sufficiently high combustor Mach, to take place locally at constant volume, unlike conventional Brayton cycles. Full article
(This article belongs to the Special Issue Combustion and Propulsion Systems)
Show Figures

Figure 1

Article
Series-Parallel Reconfigurable Electric Double-Layer Capacitor Module with Cell Equalization Capability, High Energy Utilization Ratio, and Good Modularity
Energies 2021, 14(12), 3689; https://doi.org/10.3390/en14123689 - 21 Jun 2021
Viewed by 576
Abstract
Voltages of electric double-layer capacitor (EDLC) modules vary rather wider than traditional secondary batteries. Although EDLCs should desirably be cycled in a voltage range as wide as possible to achieve a high energy utilization ratio, the wide voltage variation of EDLC modules impairs [...] Read more.
Voltages of electric double-layer capacitor (EDLC) modules vary rather wider than traditional secondary batteries. Although EDLCs should desirably be cycled in a voltage range as wide as possible to achieve a high energy utilization ratio, the wide voltage variation of EDLC modules impairs the performance of DC–DC converters. To address such issues, previous works reported series-parallel reconfiguration techniques, which are roughly divided into balance- and unbalance-shift circuits. However, conventional balance-shift circuits are not applicable to modules comprising odd number cells, impairing modularity. Unbalance-shift circuits, on the other hand, unavoidably cause cell voltage imbalance that reduces energy utilization ratio. This paper proposes a novel series-parallel reconfigurable EDLC module with cell voltage equalization capability. The proposed reconfigurable EDLC module is applicable to any number of cells, realizing good modularity. Furthermore, all cells in the proposed module can be charged and discharged uniformly without generating cell voltage imbalance, achieving an improved energy utilization ratio compared with conventional techniques. A five-cell module prototype was built for experimental verification. While the module voltage varied between 1.04 and 2.83 V, all cells discharged from 2.5 to 0.3 V. The result is equivalent to a 98.6% energy utilization ratio. Full article
(This article belongs to the Section D: Energy Storage and Application)
Show Figures

Figure 1

Article
Complementing Syngas with Natural Gas in Spark Ignition Engines for Power Production: Effects on Emissions and Combustion
Energies 2021, 14(12), 3688; https://doi.org/10.3390/en14123688 - 21 Jun 2021
Cited by 5 | Viewed by 666
Abstract
Power generation units based on the bio-syngas system face two main challenges due to (i) the possible temporary shortage of primary sources and (ii) the engine power derating associated with the use of low-energy density fuels in combustion engines. In both cases, an [...] Read more.
Power generation units based on the bio-syngas system face two main challenges due to (i) the possible temporary shortage of primary sources and (ii) the engine power derating associated with the use of low-energy density fuels in combustion engines. In both cases, an external input fuel is provided. Hence, complementing syngas with traditional fuels, like natural gas, becomes a necessity. In this work, an experimental methodology is proposed, aiming at the quantification of the impact of the use of both natural gas and syngas in spark ignition (SI) engines on performance and emissions. The main research questions focus on investigating brake thermal efficiency (BTE), power derating, and pollutant emission (NOx, CO, THC, CO2) formation, offering quantitative findings that present the basis for engine optimization procedures. Experimental measurements were performed on a Toyota 4Y-E engine (a 4-cylinders, 4-stroke spark ignition engine) at partial load (10 kW) under different syngas energy shares (SES) and at four different spark ignition timings (10°, 25°, 35° and 45° BTDC). Results reveal that the impact of the different fuel mixtures on BTE is negligible if compared to the influence of spark advance variation on BTE. On the other hand, power derating has proven to be a limiting factor and becomes more prominent with increasing SES. An increasing SES also resulted in an increase of CO and CO2 emissions, while NOx and THC emissions decreased with increasing SES. Full article
Show Figures

Figure 1

Article
Rooftop PV: Potential and Impacts in a Complex Territory
Energies 2021, 14(12), 3687; https://doi.org/10.3390/en14123687 - 21 Jun 2021
Cited by 2 | Viewed by 897
Abstract
When developing a sustainability plan in a complex and heavily urbanized territory, one of the most relevant options available is installing rooftop photovoltaic (PV) panels. Thus, it is essential to determine the amount of available surface and the potential impact of such installations [...] Read more.
When developing a sustainability plan in a complex and heavily urbanized territory, one of the most relevant options available is installing rooftop photovoltaic (PV) panels. Thus, it is essential to determine the amount of available surface and the potential impact of such installations on the energy and emission budget of the area. Instead of processing remotely sensed imagery, which is a long process and does not allow considering the buildings’ ownership, this study develops an approach based on a cluster analysis of the urban/morphological characteristics of the municipalities. Once a clear group diversification is obtained, the roof surface of the center of gravity of each cluster is extrapolated to all similar settlements. This, together with the information of local solar irradiation, allowed us to compute each cluster’s potential solar energy production and its capability to respond to the local energy demand, a key parameter to decide about the possibility of a local smart electricity network. Finally, the emissions avoided thanks to solar PV development are computed in terms of carbon dioxide and other relevant pollutants. This approach is applied to the residential rooftop of Lombardy, a Northern Italy region with a wide variety of urban morphologies and landscapes. The potential production of rooftop PV exceeds the estimated electricity consumption of residential buildings and would allow sparing almost 4 M ton of CO2 equivalent or 5% of the overall regional emissions. Full article
Show Figures

Graphical abstract

Article
Reduction of Fractionation of Lightweight Slurry to Geothermal Boreholes
Energies 2021, 14(12), 3686; https://doi.org/10.3390/en14123686 - 21 Jun 2021
Cited by 2 | Viewed by 487
Abstract
When designing the cement slurry for casing string cementing in geothermal boreholes, the appropriate thermal conductivity is selected. In the zone of geothermal water, where thermal energy is collected, cement slurry is used, from which the cement sheath has high thermal conductivity. On [...] Read more.
When designing the cement slurry for casing string cementing in geothermal boreholes, the appropriate thermal conductivity is selected. In the zone of geothermal water, where thermal energy is collected, cement slurry is used, from which the cement sheath has high thermal conductivity. On the other hand, the remaining part of the opening is sealed with slurry, from which the cement sheath will reduce thermal energy losses through appropriate thermal insulation. Cement slurry with appropriate thermal insulation includes light insulating materials. However, the use of such additives is very problematic as they are fractionated due to their low density. Therefore, measures should be taken to prevent fractionation of the cement slurry for sealing geothermal boreholes. This article presents the results of research on fractionation of cement slurries for sealing geothermal boreholes. 12 slurries were used for the tests. Six of them are based on class A cement, and six based on class G cement. This action shows the differences in fractionation depending on the binder used. However, the main area of research is determining the effectiveness of counteracting fractionation by the means used for this purpose. As a result of the conducted works, a very good improvement of the cement slurry stability is obtained after the introduction of xanthan gum, as well as filtration perlite. These measures prevent fractionation, so that the cement slurry has a homogeneous structure, and the cement sheath provides the required thermal insulation in the geothermal well. Full article
(This article belongs to the Special Issue Use of Geothermal Energy Sources)
Show Figures

Graphical abstract

Previous Issue
Next Issue
Back to TopTop