Energies

24 pages, 10730 KiB

Open AccessArticle

Short-Term Deterministic Solar Irradiance Forecasting Considering a Heuristics-Based, Operational Approach

by Armando Castillejo-Cuberos, John Boland and Rodrigo Escobar

Energies 2021, 14(18), 6005; https://doi.org/10.3390/en14186005 - 21 Sep 2021

Cited by 4 | Viewed by 2402

Solar energy is an economic and clean power source subject to natural variability, while energy storage might attenuate it, ultimately, effective and operationally feasible forecasting techniques for energy management are needed for better grid integration. This work presents a novel deterministic forecast method [...] Read more.

Solar energy is an economic and clean power source subject to natural variability, while energy storage might attenuate it, ultimately, effective and operationally feasible forecasting techniques for energy management are needed for better grid integration. This work presents a novel deterministic forecast method considering: irradiance pattern classification, Markov chains, fuzzy logic and an operational approach. The method developed was applied in a rolling manner for six years to a target location with no prior data to assess performance and its changes as new local data becomes available. Clearness index, diffuse fraction and irradiance hourly forecasts are analyzed on a yearly basis but also for 20 day types, and compared against smart persistence. Results show the proposed method outperforms smart persistence by ~10% for clearness index and diffuse fraction on the base case, but there are significant differences across the 20 day types analyzed, reaching up to +60% for clear days. Forecast lead time has the greatest impact in forecasting performance, which is important for any practical implementation. Seasonality in data gaps or rejected data can have a definite effect in performance assessment. A novel, comprehensive and detailed analysis framework was shown to present a better assessment of forecasters’ performance. Full article

(This article belongs to the Special Issue Advances in Wind and Solar Farm Forecasting)

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56 pages, 5541 KiB

Open AccessReview

A Critical Review of Experimental Investigations about Convective Heat Transfer Characteristics of Nanofluids under Turbulent and Laminar Regimes with a Focus on the Experimental Setup

by Gianpiero Colangelo, Noemi Francesca Diamante, Marco Milanese, Giuseppe Starace and Arturo de Risi

Energies 2021, 14(18), 6004; https://doi.org/10.3390/en14186004 - 21 Sep 2021

Cited by 13 | Viewed by 3102

Abstract

In this study, several experimental investigations on the effects of nanofluids on the convective heat transfer coefficient in laminar and turbulent conditions were analyzed. The aim of this work is to provide an overview of the thermal performance achieved with the use of [...] Read more.

In this study, several experimental investigations on the effects of nanofluids on the convective heat transfer coefficient in laminar and turbulent conditions were analyzed. The aim of this work is to provide an overview of the thermal performance achieved with the use of nanofluids in various experimental systems. This review covers both forced and natural convection phenomena, with a focus on the different experimental setups used to carry out the experimental campaigns. When possible, a comparison was performed between different experimental campaigns to provide an analysis of the possible common points and differences. A significant increase in the convective heat transfer coefficient was found by using nanofluids instead of traditional heat transfer fluids, in general, even with big data dispersion from one case to another that depended on boundary conditions and the particular experimental setup. In particular, a general trend shows that once a critic value of the Reynolds number or nanoparticle concentrations is reached, the heat transfer performance of the nanofluid decreases or has no appreciable improvement. As a research field still under development, nanofluids are expected to achieve even higher performance and their use will be crucial in many industrial and civil sectors to increase energy efficiency and, thus, mitigate the environmental impact. Full article

(This article belongs to the Special Issue Nanofluids Heat Transfer)

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20 pages, 4388 KiB

Open AccessArticle

Experimental Analysis of the R744/R404A Cascade Refrigeration System with Internal Heat Exchanger. Part 1: Coefficient of Performance Characteristics

by Min-Ju Jeon

Energies 2021, 14(18), 6003; https://doi.org/10.3390/en14186003 - 21 Sep 2021

Cited by 11 | Viewed by 3437

Abstract

This study evaluates the performance of an R744/R404A cascade refrigeration system (CRS) with internal heat exchangers (IHE) in supermarkets. R744 is used as the refrigerant in a low-temperature cycle, and R404A is used as the refrigerant in a high-temperature cycle. In previous studies, [...] Read more.

This study evaluates the performance of an R744/R404A cascade refrigeration system (CRS) with internal heat exchangers (IHE) in supermarkets. R744 is used as the refrigerant in a low-temperature cycle, and R404A is used as the refrigerant in a high-temperature cycle. In previous studies, there are many studies including theoretical performance analysis of the CRS. However, experimental studies on the CRS are lacking, and experimental research on the R744/R404A system with an IHE is scarce. Therefore, this study provides basic data for optimal refrigeration system design by experimentally evaluating the results of modifying various parameters. The operating parameters considered in this study include subcooling and superheating, condensing and evaporating temperature, cascade evaporation temperature, and IHE efficiency in the R744 low- and R404A high-temperature cycle. The main results are summarized as follows: (1) By applying the results of this study, energy efficiency is achieved by optimizing the overall coefficient of performance (COP) of the CRS, and the refrigerant charge of the R404A cycle is minimized and economic efficiency is also obtained, enabling operation and maintenance as an environment-friendly system. (2) When designing the CRS, finding the cascade evaporation temperature that has the optimum and maximum COP according to the refrigerant combination should be considered with the highest priority. Full article

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21 pages, 5287 KiB

Open AccessArticle

Ammonium Chloride (NH₄Cl)—Ammonia (NH₃): Sorption Characteristics for Heat Pump Applications

by George H. Atkinson, Samuel Hinmers, Robert E. Critoph and Michel van der Pal

Energies 2021, 14(18), 6002; https://doi.org/10.3390/en14186002 - 21 Sep 2021

Cited by 12 | Viewed by 4907

Abstract

In a resorption heat pump, the adsorption and desorption reaction of ammonium chloride (NH₄Cl) with ammonia (NH₃) is of interest as a Low Temperature Salt (LTS). Reviewing previously published NH₄Cl-NH₃ equilibrium lines, ammonium chloride appears to [...] Read more.

In a resorption heat pump, the adsorption and desorption reaction of ammonium chloride (NH₄Cl) with ammonia (NH₃) is of interest as a Low Temperature Salt (LTS). Reviewing previously published NH₄Cl-NH₃ equilibrium lines, ammonium chloride appears to offer useable working temperatures (50–70 °C) in the 10–15 bar pressure range during the adsorption reaction, and provides beneficial working conditions for the desorption reaction, when compared with alternative LTS candidates at atmospheric pressure. The NH₄Cl-NH₃ adsorption and desorption reactions, using a NH₄Cl composite salt, have been evaluated under dynamic ‘real-world’ conditions in a Large Temperature Jump (LTJ) experimental testing rig; although there are concerns with mass transfer characteristics, the salt exhibits no hysteresis between the adsorption and desorption reactions, contrary to previous literature. The experimentally obtained equilibrium line values for the reaction enthalpy and entropy are 29,835 J/mol and 207 J/(mol∙K), respectively. Using a semi-empirical model, the NH₄Cl composite salt has been successfully characterised, enabling the prediction of salt reaction behaviour. The model constants, A and n, identified are 4.5 and 5 for adsorption and 5 and 4 for desorption, with an overall salt active fraction (applicable to both reactions) of 0.98. Overall, the working equilibrium line and the dynamic performance of ammonium chloride has been investigated and the applicability of NH₄Cl as a LTS for a resorption heat pump determined. Full article

(This article belongs to the Special Issue Advances on Adsorption Heat Pumps, Stores and Systems)

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28 pages, 62057 KiB

Open AccessArticle

Multi-Criteria Optimization of Energy-Efficient Cementitious Sandwich Panels Building Systems Using Genetic Algorithm

by Ehsan Mirnateghi and Ayman S. Mosallam

Energies 2021, 14(18), 6001; https://doi.org/10.3390/en14186001 - 21 Sep 2021

Cited by 4 | Viewed by 2065

Abstract

This paper presents results of a study that focuses on developing a genetic algorithm (GA) for multi-criteria optimization of orthotropic, energy-efficient cementitious composite sandwich panels (CSP). The current design concept of all commercially produced CSP systems is based on the assumption that such [...] Read more.

This paper presents results of a study that focuses on developing a genetic algorithm (GA) for multi-criteria optimization of orthotropic, energy-efficient cementitious composite sandwich panels (CSP). The current design concept of all commercially produced CSP systems is based on the assumption that such panels are treated as doubly reinforced sections without the consideration of the three-dimensional truss contribution of the orthotropic panel system. This leads to uneconomical design and underestimating both the strength and stiffness of such system. In this study, two of the most common types of commercially produced sandwich were evaluated both numerically and experimentally and results were used as basis for developing a genetic algorithm optimization process using numerical modeling simulations. In order to develop a sandwich panel with high structural performance, design optimization techniques are needed to achieve higher composite action, while maintaining the favorable features of such panels such as lightweight and high thermal insulation. The study involves both linear and nonlinear finite element analyses and parametric optimization. The verification and calibration of the numerical models is based on full-scale experimental results that were performed on two types of commercially produced sandwich panels under different loading scenarios. The genetic algorithm technique is used for optimization to identify an optimum design of the cementitious composite sandwich panels. The GA technique combines Darwin’s principle of survival of fittest and a structured information exchange using randomized crossover operators to evolve an optimum design for the cementitious sandwich panel. Parameters evaluated in the study include: (i) shear connectors’ geometry, its volume fraction and distribution; (ii) exterior cementitious face sheets thickness and (iii) size and geometry steel wires reinforcements. The proposed optimization method succeeded in reducing cost of materials of CSP by about 48% using genetic algorithm methodology. In addition, an optimized design for CSP is proposed that resulted in increasing the panel’s thermal resistance by 40% as compared to existing panels, while meeting ACI Code structural design criteria. Pareto-optimal front and Pareto-optimal solutions have been identified. Correlation between the design variables is also verified and design recommendation are proposed. Full article

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19 pages, 4781 KiB

Open AccessArticle

Identification of Critical Components in the Complex Technical Infrastructure of the Large Hadron Collider Using Relief Feature Ranking and Support Vector Machines

by Ahmed Shokry, Piero Baraldi, Andrea Castellano, Luigi Serio and Enrico Zio

Energies 2021, 14(18), 6000; https://doi.org/10.3390/en14186000 - 21 Sep 2021

Cited by 3 | Viewed by 2151

Abstract

This work proposes a data-driven methodology for identifying critical components in Complex Technical Infrastructures (CTIs), for which the functional logic and/or the system structure functions are not known due the CTI’s complexity and evolving nature. The methodology uses large amounts of CTI monitoring [...] Read more.

This work proposes a data-driven methodology for identifying critical components in Complex Technical Infrastructures (CTIs), for which the functional logic and/or the system structure functions are not known due the CTI’s complexity and evolving nature. The methodology uses large amounts of CTI monitoring data acquired over long periods of time and under different operating conditions. The critical components are identified as those for which the condition monitoring signals permit the optimal classification of the CTI functioning or failed state. The methodology includes two stages: in the first stage, a feature selection filter method based on the Relief technique is used to rank the monitoring signals according to their importance with respect to the CTI functioning or failed state; the second stage identifies the subset of signals among those highlighted by the Relief technique that are most informative with respect to the CTI state. This identification is performed on the basis of evaluating the performance of a Cost-Sensitive Support Vector Machine (CS-SVM) classifier trained with several subsets of the candidate signals. The capabilities of the methodology proposed are assessed through its application to different benchmarks of highly imbalanced datasets, showing performances that are competitive to those obtained by other methods presented in the literature. The methodology is finally applied to the monitoring signals of the Large Hadron Collider (LHC) of the European Organization for Nuclear Research (CERN), a CTI for experiments of physics; the criticality of the identified components has been confirmed by CERN experts. Full article

(This article belongs to the Special Issue Special Issue of ESREL2020 PSAM15)

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27 pages, 3344 KiB

Open AccessFeature PaperArticle

Criteria, Indicators, and Factors of the Sustainable Energy-Saving Economic Development: The Case of Natural Gas Consumption

by Olexandr Yemelyanov, Anastasiya Symak, Tetyana Petrushka, Olena Vovk, Oksana Ivanytska, Dmytro Symak, Anatolii Havryliak, Taras Danylovych and Lilia Lesyk

Energies 2021, 14(18), 5999; https://doi.org/10.3390/en14185999 - 21 Sep 2021

Cited by 23 | Viewed by 4576

Abstract

To solve the contradiction between achieving long-term economic growth and reducing the consumption of certain types of resources, the concept of sustainable resource saving economic development must be put into practice. The purpose of this research is to establish criteria, develop indicators, and [...] Read more.

To solve the contradiction between achieving long-term economic growth and reducing the consumption of certain types of resources, the concept of sustainable resource saving economic development must be put into practice. The purpose of this research is to establish criteria, develop indicators, and identify factors of the sustainable energy-saving economic development, as well as to test the developed theoretical provisions using the example of natural gas consumption by different countries. To achieve this goal, various methods were used, including economic and mathematical modeling, time series analysis, factor analysis, regression analysis, and so on. The criteria were formalized, according to which a certain type of economic development can be attributed to energy saving both at the level of the state economy as a whole and at the level of individual industries and enterprises. It was established that the formalized criteria of the sustainable energy-saving economic development have the form of chains of inequalities, and their application makes it possible to identify the general conditions for ensuring this type of development. The main properties of energy-saving economic development were identified. They include the pace of this development, its potential, balance, permanence, and other characteristics. Indicators that can be used to quantify these characteristics were developed. The factors influencing the scale and time characteristics of sustainable energy-saving economic development at the level of the state economy and that of industries and individual enterprises, were systematized. The dynamics of natural gas consumption in different countries was analyzed. The reasons for the lack of energy-saving natural gas economic development in some countries were identified. A quantitative assessment of the properties of this type of economic development by country was conducted. The influence of some factors on the parameters of the sustainable energy-saving natural gas economic development of countries was analyzed. The existence of a negative effect of the rebound in the consumption of natural gas was established at certain intervals in some countries. The obtained results provide an opportunity to increase the degree of understanding of the complex patterns that underlie the sustainable energy-saving economic development of states, industries, and enterprises. These results can also be used in the development of government programs to stimulate energy conservation. Full article

(This article belongs to the Section C: Energy Economics and Policy)

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19 pages, 9496 KiB

Open AccessArticle

Energy Consumption Model of Aerial Urban Logistic Infrastructures

by Giuseppe Aiello, Rosalinda Inguanta, Giusj D’Angelo and Mario Venticinque

Energies 2021, 14(18), 5998; https://doi.org/10.3390/en14185998 - 21 Sep 2021

Cited by 15 | Viewed by 2990

Abstract

In the last decade, logistic systems based on small aerial vehicles (drones) have become attractive for urban delivery operations as a sustainable alternative to ground vehicles because they are not affected by the congestion of the road network, thus allowing for faster and [...] Read more.

In the last decade, logistic systems based on small aerial vehicles (drones) have become attractive for urban delivery operations as a sustainable alternative to ground vehicles because they are not affected by the congestion of the road network, thus allowing for faster and more reliable services. Aerial logistic systems, however, require a substantially different approach to operations management and need specifically designed supportive infrastructures. While the research on urban aerial delivery mostly focuses on the optimization vehicle operations, the appropriate design of supportive infrastructures is seldom considered. This paper focuses on the energy efficiency of aerial logistic systems, and proposes a new original methodology to obtain a realistic estimate of the overall energy consumed by a swarm of drones employed for urban delivery, taking into account the extension of the area served and its specific features. The methodology proposed offers relevant information for the decision problems related to the appropriate sizing of the infrastructures, the dimensioning of the swarm of drones and the capacity of the energy storage system. The paper also reports a comparison with ground vehicles in the same scenarios, showing the relevant tradeoffs. The results obtained demonstrate how an appropriate design of the supportive infrastructures for urban aerial logistics may significantly impact the overall efficiency of the delivery system. Full article

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22 pages, 726 KiB

Open AccessArticle

Sizing and Management of an Energy System for a Metropolitan Station with Storage and Related District Energy Community

by Mircea Stefan Simoiu, Ioana Fagarasan, Stephane Ploix and Vasile Calofir

Energies 2021, 14(18), 5997; https://doi.org/10.3390/en14185997 - 21 Sep 2021

Cited by 8 | Viewed by 2075

Abstract

Future renewable energy communities will reshape the paradigm in which we design and control efficient power systems at the district level. In this manner, the focus will be fundamentally shifted towards sustainable related concepts such as self-consumption, self-sufficiency and net energy exchanged with [...] Read more.

Future renewable energy communities will reshape the paradigm in which we design and control efficient power systems at the district level. In this manner, the focus will be fundamentally shifted towards sustainable related concepts such as self-consumption, self-sufficiency and net energy exchanged with the grid. In this context, the paper presents a novel approach for optimally designing and controlling the photovoltaic plant and energy storage systems for a metro station in order to increase collective self-consumption and self-sufficiency at the district level. The methodology considers a community of several households connected to a subway station and focuses on the interaction between energy sources and consumers. Furthermore, the optimal solution is determined by using a Mixed Integer Linear Programming Approach, and the impact of different configurations on the overall district benefit is investigated by using several simulation scenarios. The work presents a detailed case study to underline the benefits and flexibility offered by the energy storage system in comparison with a scenario involving only a photovoltaic plant. Full article

(This article belongs to the Special Issue Energy Efficiency of Buildings at the District Scale)

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23 pages, 6353 KiB

Open AccessArticle

Discontinuous Current Mode Modeling and Zero Current Switching of Flyback Converter

by Rustam Kumar, Chih-Chiang Wu, Ching-Yao Liu, Yu-Lin Hsiao, Wei-Hua Chieng and Edward-Yi Chang

Energies 2021, 14(18), 5996; https://doi.org/10.3390/en14185996 - 21 Sep 2021

Cited by 9 | Viewed by 3146

Abstract

The flyback converters are widely used in low power applications. The switch typically requires 600 V breakdown voltage in order to perform large step-down voltage. Thus, slight variation on the switch control can either permanently damage the switch or decrease the efficiency of [...] Read more.

The flyback converters are widely used in low power applications. The switch typically requires 600 V breakdown voltage in order to perform large step-down voltage. Thus, slight variation on the switch control can either permanently damage the switch or decrease the efficiency of the power conversion. In order to achieve higher power efficiency, the previous literature suggested operating the flyback converter in the discontinuous current mode (DCM). It is then required to understand the critical conditions of the DCM through analyzing the dynamic behavior and discontinuous current mechanism. This paper started from the current waveform analyses, proceeded to the derivation of zero current switching (ZCS) formulation, and finally reached the necessary conditions for the DCM. The entire DCM operation was divided into three phases that subsequently affect the result of the zero voltage switching (ZVS) and then to the ZCS. The experiment shows a power efficiency of over 96% when the output power is around 65 W. The switch used in this paper is a Gallium Nitride High-Electron-Mobility Transistor (GaN HEMT) that is advantageous at the high breakdown voltage up to 800 V. The important findings from the experiments include that the output power increases with the increasing input DC voltage and the duty cycle is rather linearly decreasing with the increasing switching frequency when both the zero voltage switching (ZVS) and ZCS conditions are satisfied simultaneously. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductors and Their Applications)

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16 pages, 5226 KiB

Open AccessArticle

Experimental and Numerical Study on the Sooting Behaviors of Furanic Biofuels in Laminar Counterflow Diffusion Flames

by Qianqian Mu, Fuwu Yan, Jizhou Zhang, Lei Xu and Yu Wang

Energies 2021, 14(18), 5995; https://doi.org/10.3390/en14185995 - 21 Sep 2021

Cited by 3 | Viewed by 1901

Abstract

Furanic biofuels have received increasing research interest over recent years, due to their potential in reducing greenhouse gas emissions and mitigating the production of harmful pollutants. Nevertheless, the heterocyclic structure in furans make them readily to produce soot, which requires an in-depth understanding. [...] Read more.

Furanic biofuels have received increasing research interest over recent years, due to their potential in reducing greenhouse gas emissions and mitigating the production of harmful pollutants. Nevertheless, the heterocyclic structure in furans make them readily to produce soot, which requires an in-depth understanding. In this study, the sooting characteristic of several typical furanic biofuels, i.e., furan, 2-methylfuran (MF), and 2,5-dimethylfuran (DMF), were investigated in laminar counterflow flames. Combined laser-based soot measurements with numerical analysis were performed. Special focus was put on understanding how the fuel structure of furans could affect soot formation. The results show that furan has the lowest soot volume fraction, followed by DMF, while MF has the largest value. Kinetic analyses revealed that the decomposition of MF produces high amounts of C3 species, which are efficient benzene precursors. This may be the reason for the enhanced formation of polycyclic aromatic hydrocarbons (PAHs) and soot in MF flames, as compared to DMF and furan flames. The major objectives of this work are to: (1) understand the sooting behavior of furanic fuels in counterflow flames, (2) elucidate the fuel structure effects of furans on soot formation, and (3) provide database of quantitative soot concentration for model validation and refinements. Full article

(This article belongs to the Special Issue Challenges and Research Trends of Combustion Mechanism)

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15 pages, 2213 KiB

Open AccessArticle

Design of a Hybrid Energy System with Energy Storage for Standalone DC Microgrid Application

by Mwaka I. Juma, Bakari M. M. Mwinyiwiwa, Consalva J. Msigwa and Aviti T. Mushi

Energies 2021, 14(18), 5994; https://doi.org/10.3390/en14185994 - 21 Sep 2021

Cited by 17 | Viewed by 4277

Abstract

This paper presents microgrid-distributed energy resources (DERs) for a rural standalone system. It is made up of a solar photovoltaic (solar PV) system, battery energy storage system (BESS), and a wind turbine coupled to a permanent magnet synchronous generator (WT-PMSG). The DERs are [...] Read more.

This paper presents microgrid-distributed energy resources (DERs) for a rural standalone system. It is made up of a solar photovoltaic (solar PV) system, battery energy storage system (BESS), and a wind turbine coupled to a permanent magnet synchronous generator (WT-PMSG). The DERs are controlled by maximum power point tracking (MPPT)-based proportional integral (PI) controllers for both maximum power tracking and error feedback compensation. The MPPT uses the perturb and observe (P&O) algorithm for tracking the maximum power point of the DERs. The PI gains are tuned using the Ziegler–Nichols method. The developed system was built and simulated in MATLAB/Simulink under two conditions—constant load, and step-load changes. The controllers enabled the BESS to charge even during conditions of varying load and other environmental factors such as change of irradiance and wind speed. The reference was tracked extremely well by the output voltage of the DC microgrid. This is useful research for electrifying the rural islanded areas which are too far from the grid. Full article

(This article belongs to the Topic Innovative Techniques for Smart Grids)

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17 pages, 3119 KiB

Open AccessArticle

The Environmental Aspect in the Concept of Corporate Social Responsibility in the Energy Industry and Sustainable Development of the Economy

by Katarzyna Huk and Mateusz Kurowski

Energies 2021, 14(18), 5993; https://doi.org/10.3390/en14185993 - 21 Sep 2021

Cited by 11 | Viewed by 3106

Abstract

Sustainable development is now an important direction for the further development of all economies in the world. It is important to balance economic development with the impact on the environment and our planet. Another direction in the development of management sciences is the [...] Read more.

Sustainable development is now an important direction for the further development of all economies in the world. It is important to balance economic development with the impact on the environment and our planet. Another direction in the development of management sciences is the emergence of the concept of Corporate Social Responsibility, which considers this impact in three key aspects—economic, environmental and social—in terms of microeconomics. This concept gives companies specific guidelines and tools that minimize their negative impact on the environment. Reducing the negative impact of companies influences the environment and this is what is mainly associated with them. However, companies should also pay attention to internal consistency and caring for employees. Company practices such as the exploitation of people, including children, and injustice in the workplace are some of the factors that can be observed in less developed countries. The article focuses on the presentation of the environmental aspect in the context of the concept of corporate social responsibility. We analyzed individual sectors of the economy in terms of the environmental aspect, with particular emphasis on the energy industry. The study is based on a statistical analysis taking into account data from 1718 companies from all over the world. The aim of the article is to present the environmental aspect in the context of corporate social responsibility in the energy industry as a direction for sustainable development of the economy. The article is based on the analysis of the literature and databases presenting CSR, which was created on the basis of questionnaire research. The article shows which regions of the world are worse and which are better in terms of the environmental aspects of CSR. Conclusions on the main CSR guidelines for the environment are also presented. We analyzed factors such as environmental routines, policies and targets, implementation of environmental management systems, ISO 14001/EMAS certification, environmental reporting, environmental requirements inside the supply chain, the trend of GHG emissions and the trend of energy consumption for their environmental impact. The analysis was carried out on the basis of given regions of the world and individual sectors of the economy, especially the energy industry. Full article

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24 pages, 9184 KiB

Open AccessArticle

Impact of Quadrature Booster on Power-System State Estimation in Polar Coordinates

by Tomasz Okon and Kazimierz Wilkosz

Energies 2021, 14(18), 5992; https://doi.org/10.3390/en14185992 - 21 Sep 2021

Cited by 1 | Viewed by 1470

Abstract

The paper concerns the estimation of the state of a power system in which there is a phase shifter called a quadrature booster. The aim of the paper is a comparative analysis of two different cases including the quadrature booster in the state [...] Read more.

The paper concerns the estimation of the state of a power system in which there is a phase shifter called a quadrature booster. The aim of the paper is a comparative analysis of two different cases including the quadrature booster in the state estimation. In the first case, the quadrature booster is represented by a model consisting of two real voltage sources, one in series with a power line and the other in a shunt branch. In the second case, in the power system model, the real branch with the quadrature booster is represented as off at the end where the considered quadrature booster is actually installed. The state estimation is assumed to be carried out in the polar coordinate system. The properties of the state estimation are characterized by: the number of iterations in the calculation process, the index of conditioning of the matrix of coefficients in the equations to be solved (cond(G)), and ratio Je/Jm, which is a measure of the accuracy of the estimation. Using IEEE 14-bus test system, investigations are carried out in such a way as to cover the entire state space of the power system as possible. In the investigations, Monte Carlo experiments are carried out for each of the considered cases of the state estimation. Each of these cases is also analyzed from the point of view of the assumed definition of the state estimation. Investigations show that in the first of the previously described cases, the state estimation is more accurate, but there are more iterations in the calculations and worse conditioning of the estimation process. The comparative analysis also shows that, the accuracy of the results obtained in each of the considered cases is practically independent of the coordinate system in which the estimation calculations are performed. Taking into account the number of iterations in the estimation process and index cond(G), it can be concluded that the implementation of each of the above-mentioned estimation cases in the rectangular coordinate system is more reasonable. Full article

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23 pages, 5656 KiB

Open AccessReview

Evaporator Frosting in Refrigerating Appliances: Fundamentals and Applications

by Christian J. L. Hermes, Joel Boeng, Diogo L. da Silva, Fernando T. Knabben and Andrew D. Sommers

Energies 2021, 14(18), 5991; https://doi.org/10.3390/en14185991 - 21 Sep 2021

Cited by 9 | Viewed by 5096

Abstract

Modern refrigerators are equipped with fan-supplied evaporators often tailor-made to mitigate the impacts of frost accretion, not only in terms of frost blocking, which depletes the cooling capacity and therefore the refrigerator coefficient of performance (COP), but also to allow optimal defrosting, thereby [...] Read more.

Modern refrigerators are equipped with fan-supplied evaporators often tailor-made to mitigate the impacts of frost accretion, not only in terms of frost blocking, which depletes the cooling capacity and therefore the refrigerator coefficient of performance (COP), but also to allow optimal defrosting, thereby avoiding the undesired consequences of condensate retention and additional thermal loads. Evaporator design for frosting conditions can be done either empirically through trial-and-error approaches or using simulation models suitable to predict the distribution of the frost mass along the finned coil. Albeit the former is mandatory for robustness verification prior to product approval, it has been advocated that the latter speeds up the design process and reduces the costs of the engineering undertaking. Therefore, this article is aimed at summarizing the required foundations for the design of efficient evaporators and defrosting systems with minimized performance impacts due to frosting. The thermodynamics, and the heat and mass transfer principles involved in the frost nucleation, growth, and densification phenomena are presented. The thermophysical properties of frost, such as density and thermal conductivity, are discussed, and their relationship with refrigeration operating conditions are established. A first-principles model is presented to predict the growth of the frost layer on the evaporator surface as a function of geometric and operating conditions. The relation between the microscopic properties of frost and their macroscopic effects on the evaporator thermo-hydraulic performance is established and confirmed with experimental evidence. Furthermore, different defrost strategies are compared, and the concept of optimal defrost is formulated. Finally, the results are used to analyze the efficiency of the defrost operation based on the net cooling capacity of the refrigeration system for different duty cycles and evaporator geometries. Full article

(This article belongs to the Special Issue Heat Exchangers: Cooling and Heating Systems)

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82 pages, 2398 KiB

Open AccessReview

Critical Review of Intelligent Battery Systems: Challenges, Implementation, and Potential for Electric Vehicles

by Lidiya Komsiyska, Tobias Buchberger, Simon Diehl, Moritz Ehrensberger, Christian Hanzl, Christoph Hartmann, Markus Hölzle, Jan Kleiner, Meinert Lewerenz, Bernhard Liebhart, Michael Schmid, Dominik Schneider, Sascha Speer, Julia Stöttner, Christoph Terbrack, Michael Hinterberger and Christian Endisch

Energies 2021, 14(18), 5989; https://doi.org/10.3390/en14185989 - 21 Sep 2021

Cited by 71 | Viewed by 9695

Abstract

This review provides an overview of new strategies to address the current challenges of automotive battery systems: Intelligent Battery Systems. They have the potential to make battery systems more performant and future-proof for coming generations of electric vehicles. The essential features of Intelligent [...] Read more.

This review provides an overview of new strategies to address the current challenges of automotive battery systems: Intelligent Battery Systems. They have the potential to make battery systems more performant and future-proof for coming generations of electric vehicles. The essential features of Intelligent Battery Systems are the accurate and robust determination of cell individual states and the ability to control the current of each cell by reconfiguration. They enable high-level functions like fault diagnostics, multi-objective balancing strategies, multilevel inverters, and hybrid energy storage systems. State of the art and recent advances in these topics are compiled and critically discussed in this article. A comprising, critical discussion of the implementation aspects of Intelligent Battery Systems complements the review. We touch on sensing, battery topologies and management, switching elements, communication architecture, and impact on the single-cell. This review contributes to transferring the best technologies from research to product development. Full article

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23 pages, 6766 KiB

Open AccessArticle

Addressing European Ocean Energy Challenge: The DTOceanPlus Structured Innovation Tool for Concept Creation and Selection

by Inès Tunga, Anna Garcia-Teruel, Donald R. Noble and Jillian Henderson

Energies 2021, 14(18), 5988; https://doi.org/10.3390/en14185988 - 21 Sep 2021

Cited by 5 | Viewed by 2565

Abstract

The whole energy system requires renewables that scale and produce reliable, valuable energy at an acceptable cost. The key to increasing the deployment of ocean energy is bringing down development and operating costs. This paper proposes a structured approach to innovation in ocean [...] Read more.

The whole energy system requires renewables that scale and produce reliable, valuable energy at an acceptable cost. The key to increasing the deployment of ocean energy is bringing down development and operating costs. This paper proposes a structured approach to innovation in ocean energy systems that would spur innovation and expand the market for ocean energy. This approach can be used by a wide range of stakeholders—including technology and project developers and investors—when considering creating or improving designs. The Structured Innovation design tool within the DTOceanPlus suite is one of a kind beyond the current state-of-the-art. It enables the adaptation and integration of systematic problem-solving tools based on quality function deployment (QFD), the theory of inventive thinking (TRIZ), and the failure modes and effects analysis (FMEA) methodologies for the ocean energy sector. In obtaining and assessing innovative concepts, the integration of TRIZ into QFD enables the designers to define the innovation problem, identifies trade-offs in the system, and, with TRIZ as a systematic inventive problem-solving methodology, generates potential design concepts for the contradicting requirements. Additionally, the FMEA is used to assess the technical risks associated with the proposed design concepts. The methodology is demonstrated using high-level functional requirements for a small array of ten tidal turbines to improve the devices layout and power cabling architecture. The Structured Innovation design tool output comprises critical functional requirements with the highest overall impact and the least organisational effort to implement, along with appropriate alternative solutions to conflicting requirements. Full article

(This article belongs to the Special Issue Innovation in Grid Connection and Control of Offshore Renewable Energy Systems)

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21 pages, 2960 KiB

Open AccessArticle

Exploring Sustainable Aspects Regarding the Food Supply Chain, Agri-Food Quality Standards, and Global Trade: An Empirical Study among Experts from the European Union and the United States

by Katja Pietrzyck, Sebastian Jarzębowski and Brigitte Petersen

Energies 2021, 14(18), 5987; https://doi.org/10.3390/en14185987 - 21 Sep 2021

Cited by 8 | Viewed by 6320

Abstract

Sustainability is increasingly a priority in the policies of the European Union, especially in the Common Agricultural Policy. This paper focuses on Sustainable Development Goals, the European Green Deal, and the Farm to Fork Strategy in an attempt to establish a relationship with [...] Read more.

Sustainability is increasingly a priority in the policies of the European Union, especially in the Common Agricultural Policy. This paper focuses on Sustainable Development Goals, the European Green Deal, and the Farm to Fork Strategy in an attempt to establish a relationship with the European Union’s trade policy. Three selected components of the agri-food sector—the food supply chain, agri-food quality standards, and global trade—are examined in relation to defined sustainability aspects. The aim is to understand the interrelationship between the three components with specific regard to sustainability, to highlight their high complexity and current relevance, to contribute to systematic analysis in this area, and to present current progress. This qualitative–explorative study is empirically supported by a survey of market experts, and the Transatlantic Trade and Investment Partnership between the European Union and the United States is used as an example. The results show the complexity between the relationships of the three components with a focus on sustainability and reveal a deep uncertainty. The most notable results are the limited level of knowledge and the insufficient attention from business representatives to sustainability aspects. Finally, the study identifies the state of integrating a sustainable perspective into European Union trade policy and provides suggestions for further research. Full article

(This article belongs to the Special Issue Sustainable Agriculture and Food Supply: Scientific, Economic and Policy Analysis)

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12 pages, 1527 KiB

Open AccessArticle

Advanced Metering Infrastructure—Towards a Reliable Network

by Mirosław Kornatka and Tomasz Popławski

Energies 2021, 14(18), 5986; https://doi.org/10.3390/en14185986 - 21 Sep 2021

Cited by 9 | Viewed by 3082

Abstract

In order to ensure continuous energy supply, Distribution System Operators (DSOs) have to monitor and analyze the condition of the power grid, especially checking for random events, such as breakdowns or other disturbances. Still, relatively little information is available on the operation of [...] Read more.

In order to ensure continuous energy supply, Distribution System Operators (DSOs) have to monitor and analyze the condition of the power grid, especially checking for random events, such as breakdowns or other disturbances. Still, relatively little information is available on the operation of the Low Voltage (LV) grid. This can be improved thanks to digital tools, offering online processing of data, which ultimately increases effectiveness of the power grid. Among those tools, the use of the Advanced Metering Infrastructure (AMI) is especially conducive for improving reliability. AMI is one of the elements of the system Supervisory Control and Data Acquisition (SCADA) for the LV grid. Exact knowledge of the reliability conditions of a power grid is also indispensable for optimizing investment. AMI is also key in providing operational capacity for carrying out energy balance in virtual power plants (VPPs). This paper deals with methodology of identification and location of faults in the AMI-supervised LV grid and with calculating the System Average Interruption Duration Index (SAIDI) and System Average Interruption Frequency Index (SAIFI) on the basis of the recorded events. The results presented in the paper are based on data obtained from seven MV/LV transformer stations that supply over 2000 customers. Full article

(This article belongs to the Special Issue Improvements of the Electricity Power System)

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27 pages, 3354 KiB

Open AccessArticle

Strengthening Gender Justice in a Just Transition: A Research Agenda Based on a Systematic Map of Gender in Coal Transitions

by Paula Walk, Isabell Braunger, Josephine Semb, Carolin Brodtmann, Pao-Yu Oei and Claudia Kemfert

Energies 2021, 14(18), 5985; https://doi.org/10.3390/en14185985 - 21 Sep 2021

Cited by 16 | Viewed by 6778

Abstract

For climate change mitigation, a rapid phase-out of fossil fuels such as coal is necessary. This has far-reaching gender-specific consequences. This paper presents a systematic map of the literature that examines the impact of historical coal phase-out processes on women and their role [...] Read more.

For climate change mitigation, a rapid phase-out of fossil fuels such as coal is necessary. This has far-reaching gender-specific consequences. This paper presents a systematic map of the literature that examines the impact of historical coal phase-out processes on women and their role in these processes. The search process consisted of screening over 3100 abstracts and reading 247 full-text studies. The analysis of the 73 publications ultimately included in the systematic map shows that past coal phase-outs meant both opportunities (e.g., increased labour market participation) as well as burdens for women (e.g., double burden of job and household). It becomes clear that agency within coal transitions was also gendered. For example, it was difficult for women to gain access to union structures, which led them to organise themselves into grassroots movements. Our research shows that policies aiming for a just sustainability transition should always be explicitly gender-responsive. However, the impact of sustainability transitions on women’s lives remains largely under-researched. Therefore, we propose a research agenda based on our findings containing six key issues that need to be addressed scientifically. Full article

(This article belongs to the Special Issue Women in Energy Economics and Policy)

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17 pages, 5492 KiB

Open AccessArticle

Possibilities of Upgrading Warsaw Existing Residential Area to Status of Positive Energy Districts

by Hanna Jędrzejuk and Dorota Chwieduk

Energies 2021, 14(18), 5984; https://doi.org/10.3390/en14185984 - 21 Sep 2021

Cited by 10 | Viewed by 2784

Abstract

This paper analyses possibilities of refurbishment of Warsaw’s residential buildings towards standards of the Positive Energy District. The annual final energy consumption in the city in 2019 for the district heating was 8668 GWh, gas (pipelines) was 5300 GWh, electricity from the grid [...] Read more.

This paper analyses possibilities of refurbishment of Warsaw’s residential buildings towards standards of the Positive Energy District. The annual final energy consumption in the city in 2019 for the district heating was 8668 GWh, gas (pipelines) was 5300 GWh, electricity from the grid was 7500 GWh, while the emission of the carbon dioxide was 5.62 × 10⁹ kg. The city consists of 18 districts, which are heterogeneous in terms of typology and structure of buildings. The great variety of buildings can be seen, for example, by the annual final energy demand for space heating and hot water preparation per unit of room area. This annual index ranges from over 400 kWh/m² in historic buildings to 60 kWh/m² in modern buildings. A reduction in the consumption of non-renewable energy sources and carbon dioxide emissions can be achieved by improving the energy standard of residential buildings and by using renewable energy sources: solar energy, geothermal energy and biogas. The potential barriers for achieving the status of a positive energy district, for example, problems connected with ownership, financing new investments and refurbishment and legal boundaries, have been identified. Moreover, changing the existing electrical grid and district heating systems in urban areas in Warsaw requires comprehensive modernization of practically the entire city’s infrastructure. Full article

(This article belongs to the Special Issue Smart Cities and Positive Energy Districts: Urban Perspectives in 2021)

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26 pages, 8650 KiB

Open AccessReview

A Survey on FOPID Controllers for LFO Damping in Power Systems Using Synchronous Generators, FACTS Devices and Inverter-Based Power Plants

by Mahdi Saadatmand, Gevork B. Gharehpetian, Innocent Kamwa, Pierluigi Siano, Josep M. Guerrero and Hassan Haes Alhelou

Energies 2021, 14(18), 5983; https://doi.org/10.3390/en14185983 - 21 Sep 2021

Cited by 14 | Viewed by 3042

Abstract

In recent decades, various types of control techniques have been proposed for use in power systems. Among them, the use of a proportional–integral–derivative (PID) controller is widely recognized as an effective technique. The generalized type of this controller is the fractional-order PID (FOPID) [...] Read more.

In recent decades, various types of control techniques have been proposed for use in power systems. Among them, the use of a proportional–integral–derivative (PID) controller is widely recognized as an effective technique. The generalized type of this controller is the fractional-order PID (FOPID) controller. This type of controller provides a wider range of stability area due to the fractional orders of integrals and derivatives. These types of controllers have been significantly considered as a new approach in power engineering that can enhance the operation and stability of power systems. This paper represents a comprehensive overview of the FOPID controller and its applications in modern power systems for enhancing low-frequency oscillation (LFO) damping. In addition, the performance of this type of controller has been evaluated in a benchmark test system. It can be a driver for the development of FOPID controller applications in modern power systems. Investigation of different pieces of research shows that FOPID controllers, as robust controllers, can play an efficient role in modern power systems. Full article

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23 pages, 3741 KiB

Open AccessReview

Evaporative Cooling Integrated with Solid Desiccant Systems: A Review

by Lanbo Lai, Xiaolin Wang, Gholamreza Kefayati and Eric Hu

Energies 2021, 14(18), 5982; https://doi.org/10.3390/en14185982 - 21 Sep 2021

Cited by 20 | Viewed by 6598

Abstract

Evaporative cooling technology (ECT) has been deemed as an alternative to the conventional vapor-compression air conditioning system for dry climates in recent years due to its simple structure and low operating cost. Generally speaking, the ECT includes two types of different technologies, direct [...] Read more.

Evaporative cooling technology (ECT) has been deemed as an alternative to the conventional vapor-compression air conditioning system for dry climates in recent years due to its simple structure and low operating cost. Generally speaking, the ECT includes two types of different technologies, direct evaporative cooling (DEC) and indirect evaporative cooling (IEC). Both technologies can theoretically reduce the air temperature to the wet-bulb temperature of outdoor air. The major difference between these two technologies is that DEC will introduce extra moisture to the supply air while IEC will not. The enhanced IEC, Maisotsenko-cycle (M-cyle) IEC, can even bring down the air temperature to the dew point temperature. The ECT integrated with solid desiccant systems, i.e., solid desiccant-assisted evaporative cooling technologies (SDECT), could make the technology applicable to a wider range of weather conditions, e.g., weather with high humidity. In this paper, the recent development of various evaporative cooling technologies (ECT), solid desiccant material and the integration of these two technologies, the SDECT, were thoroughly reviewed with respect to their configuration, optimization and desiccant unit improvement. Furthermore, modeling techniques for simulating SDECT with their pros and cons were also reviewed. Potential opportunities and research recommendations were indicated, which include improving the structure and material of M-cycle IEC, developing novel desiccant material and optimizing configuration, water consumption rate and operation strategy of SDECT system. This review paper indicated that the SDECT system could be a potential replacement for the conventional vapor-compressed cooling system and could be applied in hot and humid environments with proper arrangements. Full article

(This article belongs to the Special Issue Research and Development on Indirect Evaporative Cooling Technology)

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21 pages, 4984 KiB

Open AccessArticle

Experimental Analysis of Nucleation Triggering in a Thermal Energy Storage Based on Xylitol Used in a Portable Solar Box Cooker

by Gianluca Coccia, Alessia Aquilanti, Sebastiano Tomassetti, Pio Francesco Muciaccia and Giovanni Di Nicola

Energies 2021, 14(18), 5981; https://doi.org/10.3390/en14185981 - 21 Sep 2021

Cited by 13 | Viewed by 2181

Abstract

Sugar alcohols have interesting thermodynamic properties that make them good options as heat storage materials (HSMs) to be used in solar cookers. Among sugar alcohols, xylitol is affected by severe supercooling that can significantly alter its usefulness in thermal energy storage (TES) systems. [...] Read more.

Sugar alcohols have interesting thermodynamic properties that make them good options as heat storage materials (HSMs) to be used in solar cookers. Among sugar alcohols, xylitol is affected by severe supercooling that can significantly alter its usefulness in thermal energy storage (TES) systems. To overcome the supercooling issue, in this work the thermal behavior of a xylitol-based TES installed in a portable solar box cooker was investigated experimentally. The solar cooker has a 4.08 concentration ratio and the TES is a double-pot system filled with 2.5 kg of commercial-grade xylitol. The TES includes a manual mixing device that can be used to trigger the nucleation of xylitol. The effectiveness of the TES system with and without triggering was assessed through several outdoor tests, divided into heating and cooling phases, using silicone oil as absorbing media. It was found that the average load cooling time, in the temperature range of the test fluid from 110 to 80 °C, increased by about 346% when the solar cooker was equipped with the xylitol-triggered TES. The mixing device can therefore be considered an effective solution for regarding xylitol as an actual and performing phase change material. Full article

(This article belongs to the Section J: Thermal Management)

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13 pages, 6222 KiB

Open AccessArticle

Synthesis and Characterization of ZnO from Thermal Decomposition of Precipitated Zinc Oxalate Dihydrate as an Anode Material of Li-Ion Batteries

by Cornelius Satria Yudha, Anjas Prasetya Hutama, Mintarsih Rahmawati, Hendri Widiyandari, Hartoto Nursukatmo, Hanida Nilasary, Haryo Satriya Oktaviano and Agus Purwanto

Energies 2021, 14(18), 5980; https://doi.org/10.3390/en14185980 - 21 Sep 2021

Cited by 7 | Viewed by 3245

Abstract

Zinc oxide (ZnO) is one of the most promising materials applied in Li-ion batteries. In this research, ZnO was synthesized by the thermal decomposition of zinc oxalate dihydrate. This precursor was obtained from the precipitation process of zinc sulfate with oxalic acid. In-depth [...] Read more.

Zinc oxide (ZnO) is one of the most promising materials applied in Li-ion batteries. In this research, ZnO was synthesized by the thermal decomposition of zinc oxalate dihydrate. This precursor was obtained from the precipitation process of zinc sulfate with oxalic acid. In-depth studies were carried out on the effect of various heating temperatures of zinc oxalate dihydrate precursors on ZnO synthesis. The as-prepared materials were characterized by XRD, SEM, and FTIR. Based on the XRD analysis, the presence of the ZnO-wurtzite phase can be confirmed in samples heated at temperatures above 400 °C. Meanwhile, SEM-EDX results showed that the ZnO particles have a micron size. Cells with ZnO samples as anodes have low columbic efficiency. In contrast, cells with ZnO/Graphite composite anodes have a relatively large capacity compared to pure graphite anodes. Overall, based on the consideration of the characterization results and electrochemical performance, the optimal sintering temperature to obtain ZnO is 600 °C with a cell discharge capacity of ZnO anode and in the form of graphite composites is 356 mAh/g and 450 mAh/g, respectively. This suggests that ZnO can be used as an anode material and an additive component to improve commercial graphite anodes’ electrochemical performance. Full article

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19 pages, 49020 KiB

Open AccessArticle

Hydrodynamic Analysis of Twin-Hull Structures Supporting Floating PV Systems in Offshore and Coastal Regions

by Alexandros Magkouris, Kostas Belibassakis and Eugen Rusu

Energies 2021, 14(18), 5979; https://doi.org/10.3390/en14185979 - 20 Sep 2021

Cited by 11 | Viewed by 3259

Abstract

In this paper, a novel model based on the boundary element method (BEM) is presented for the hydrodynamic analysis of floating twin-hull structures carrying photovoltaic panels, supporting the study of wave responses and their effects on power performance in variable bathymetry regions. The [...] Read more.

In this paper, a novel model based on the boundary element method (BEM) is presented for the hydrodynamic analysis of floating twin-hull structures carrying photovoltaic panels, supporting the study of wave responses and their effects on power performance in variable bathymetry regions. The analysis is restricted to two spatial dimensions for simplicity. The method is free of any mild-slope assumptions. A boundary integral representation is applied for the near field in the vicinity of the floating body, which involved simple (Rankine) sources, while the far field is modeled using complete (normal-mode) series expansions that are derived using separation of variables in the constant depth half-strips on either side of the middle, non-uniform domain, where the depth exhibited a general variation, overcoming a mild bottom-slope assumption. The numerical solution is obtained by means of a low-order panel method. Numerical results are presented concerning twin-hull floating bodies of simple geometry lying over uniform and sloping seabeds. With the aid of systematic comparisons, the effects of the bottom slope and curvature on the hydrodynamic characteristics (hydrodynamic coefficients and responses) of the floating bodies are illustrated and discussed. Finally, the effects of waves on the floating PV performance are presented, indicating significant variations of the performance index ranging from 0 to 15% depending on the sea state. Full article

(This article belongs to the Topic Marine Renewable Energy)

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17 pages, 3372 KiB

Open AccessArticle

Factor Analysis of Well Logs for Total Organic Carbon Estimation in Unconventional Reservoirs

by Norbert P. Szabó, Rafael Valadez-Vergara, Sabuhi Tapdigli, Aja Ugochukwu, István Szabó and Mihály Dobróka

Energies 2021, 14(18), 5978; https://doi.org/10.3390/en14185978 - 20 Sep 2021

Cited by 4 | Viewed by 3056

Abstract

Several approaches have been applied for the evaluation of formation organic content. For further developments in the interpretation of organic richness, this research proposes a multivariate statistical method for exploring the interdependencies between the well logs and model parameters. A factor analysis-based approach [...] Read more.

Several approaches have been applied for the evaluation of formation organic content. For further developments in the interpretation of organic richness, this research proposes a multivariate statistical method for exploring the interdependencies between the well logs and model parameters. A factor analysis-based approach is presented for the quantitative determination of total organic content of shale formations. Uncorrelated factors are extracted from well logging data using Jöreskog’s algorithm, and then the factor logs are correlated with estimated petrophysical properties. Whereas the first factor holds information on the amount of shaliness, the second is identified as an organic factor. The estimation method is applied both to synthetic and real datasets from different reservoir types and geologic basins, i.e., Derecske Trough in East Hungary (tight gas); Kingak formation in North Slope Alaska, United States of America (shale gas); and shale source rock formations in the Norwegian continental shelf. The estimated total organic content logs are verified by core data and/or results from other indirect estimation methods such as interval inversion, artificial neural networks and cluster analysis. The presented statistical method used for the interpretation of wireline logs offers an effective tool for the evaluation of organic matter content in unconventional reservoirs. Full article

(This article belongs to the Special Issue Well Logging Applications)

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32 pages, 3207 KiB

Open AccessArticle

Model of Choice Photovoltaic Panels Considering Customers’ Expectations

by Dominika Siwiec and Andrzej Pacana

Energies 2021, 14(18), 5977; https://doi.org/10.3390/en14185977 - 20 Sep 2021

Cited by 35 | Viewed by 2769

Abstract

Photovoltaic electricity generation is key to achieving deep decarbonization with a high degree of electrification. It is predicted that the energy sector will reduce carbon dioxide by producing electricity mainly from photovoltaic (PV) power. Although dynamic development of the implementation of photovoltaic panels [...] Read more.

Photovoltaic electricity generation is key to achieving deep decarbonization with a high degree of electrification. It is predicted that the energy sector will reduce carbon dioxide by producing electricity mainly from photovoltaic (PV) power. Although dynamic development of the implementation of photovoltaic panels has been observed, their choice considering customer specificity is still a problem. Therefore, the purpose of this study is to propose the model of choice photovoltaic panels considering customers’ expectations. It can support the choice of a photovoltaic panel of a certain quality (satisfaction of concrete customer) in combination with the cost of its purchase. The proposed model includes acquiring and then processing customers’ expectations into technical criteria, while simultaneously considering the weighting of these criteria. It is realized in a standardized way, i.e., the zero-unitarization method (MUZ), after which normalized values of the quality of the photovoltaic panels’ criteria are obtained. In turn, the quality of these products is estimated by the weighted sum model (WSM) and then integrated with purchase cost in qualitative cost analysis (AKJ). As a result, using the scale of relative states, it is possible to categorize customer satisfaction from indicating qualitative cost and selecting the photovoltaic panel expected by customers (the most satisfactory). The effectiveness of the model was demonstrated by a sensitivity analysis, after which the key PV criteria were indicated. The proposed model is intended for any entity who selects a photovoltaic panel for customers. The computerization of calculations may contribute to its utilitarian dissemination. Full article

(This article belongs to the Special Issue Energy Decision Making: Problems, Methods, and Tools)

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18 pages, 749 KiB

Open AccessArticle

Energy Management of Microgrids for Smart Cities: A Review

by Muhammad Salman Sami, Muhammad Abrar, Rizwan Akram, Muhammad Majid Hussain, Mian Hammad Nazir, Muhammad Saad Khan and Safdar Raza

Energies 2021, 14(18), 5976; https://doi.org/10.3390/en14185976 - 20 Sep 2021

Cited by 23 | Viewed by 5366

Abstract

Electric power reliability is one of the most important factors in the social and economic evolution of a smart city, whereas the key factors to make a city smart are smart energy sources and intelligent electricity networks. The development of cost-effective microgrids with [...] Read more.

Electric power reliability is one of the most important factors in the social and economic evolution of a smart city, whereas the key factors to make a city smart are smart energy sources and intelligent electricity networks. The development of cost-effective microgrids with the added functionality of energy storage and backup generation plans has resulted from the combined impact of high energy demands from consumers and environmental concerns, which push for minimizing the energy imbalance, reducing energy losses and CO₂ emissions, and improving the overall security and reliability of a power system. It is now possible to tackle the problem of growing consumer load by utilizing the recent developments in modern types of renewable energy resources (RES) and current technology. These energy alternatives do not emit greenhouse gases (GHG) like fossil fuels do, and so help to mitigate climate change. They also have in socioeconomic advantages due to long-term sustainability. Variability and intermittency are the main drawbacks of renewable energy resources (RES), which affect the consistency of electric supply. Thus, utilizing multiple optimization approaches, the energy management system determines the optimum solution for renewable energy resources (RES) and transfers it to the microgrid. Microgrids maintain the continuity of power delivery, according to the energy management system settings. In a microgrid, an energy management system (EMS) is used to decrease the system’s expenses and adverse consequences. As a result, a variety of strategies and approaches are employed in the development of an efficient energy management system. This article is intended to provide a comprehensive overview of a range of technologies and techniques, and their solutions, for managing the drawbacks of renewable energy supplies, such as variability and load fluctuations, while still matching energy demands for their integration in the microgrids of smart cities. Full article

(This article belongs to the Special Issue Advanced Material and Design in Energy Storage)

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31 pages, 10288 KiB

Open AccessArticle

Old and Modern Wooden Buildings in the Context of Sustainable Development

by Dariusz Bajno, Agnieszka Grzybowska and Łukasz Bednarz

Energies 2021, 14(18), 5975; https://doi.org/10.3390/en14185975 - 20 Sep 2021

Cited by 12 | Viewed by 3901

Abstract

Construction is a powerful industry that is not indifferent to the environment. Neither the maintenance of buildings in a proper technical condition nor their eventual demolition is indifferent to the environment. The main threats to the environment are still the inefficient use of [...] Read more.

Construction is a powerful industry that is not indifferent to the environment. Neither the maintenance of buildings in a proper technical condition nor their eventual demolition is indifferent to the environment. The main threats to the environment are still the inefficient use of construction materials and energy needed for their production and installation, as well as the emission of harmful substances to the environment at the stage of operation of buildings and their demolition. This article discusses the importance of wood as a renewable material in terms of its physical and mechanical properties. The restoration of forest areas is of great importance to the global ecosystem and the sustainable development system, reducing the threat of global warming and the greenhouse effect by reducing CO₂ levels. In addition, demolition wood can be reused in construction, can be safely recycled as it quickly decomposes, or can be used as a source of renewable energy. The preservation of existing timber-framed buildings in good condition contributes to a lower consumption of this raw material for repair, which already significantly reduces the energy required for their manufacture, transport, and assembly. This also reduces the amount of waste that would have to be disposed of in various ways. Both at the stage of design, execution, and then exploitation, one forgets about the physical processes taking place inside the partitions and about the external climatic influences of the environment (precipitation, water vapor, and temperature) on which the type, intensity, and extent of chemical and biological corrosion depend to a very high degree. This paper presents examples of the influence of such impacts on the operational safety of three selected objects: a feed storehouse and an officer casino building from the second half of the nineteenth century and an 18th century rural homestead building. The research carried out on wooden structures of the above-mentioned objects “in situ” was verified by means of simulation models, which presented their initial and current technical conditions in relation to the type and amount of impact they should safely absorb. Moreover, within the framework of this paper, artificial intelligence methods have been implemented to predict the biological corrosion of the structures studied. The aim of the paper was to draw attention to the timber already built into buildings, which may constitute waste even after several years of operation, requiring disposal and at the same time the production of a substitute. The purpose of the research carried out by the authors of the article was to examine the older and newer buildings in use, the structures of which, in whole or in part, were made of wood. On a global scale, there will be considerable demand for the energy required to thermally dispose of this waste or to deposit it in landfills with very limited capacity until its complete biological decomposition. These energy demands and greenhouse gas emissions can be prevented by effective diagnostics of such structures and the predictability of their behaviour over time, with respect to the conditions under which they are operated. The authors of the article, during each assessment of the technical condition of a building containing wooden elements, analysed the condition of their protection each time and predicted the period of their safe life without the need for additional reinforcements or replacement by others. As the later reality shows, it is a very effective method of saving money and energy. Full article

(This article belongs to the Special Issue Advances in Green Energy, Environment and Sustainable Development 2021)

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