Numerical Methods and Computer Simulations in Energy Analysis

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Topic Information

Dear Colleagues,

The main aim of this Topic is the dissemination of research regarding the current state of numerical methods, models, optimization algorithms and computer simulation techniques in energy analysis. Energy analysis is understood as its harvesting, consumption, storage, accumulation, transformation and also its direct usage for the various energy-based numerical technique formulations and implementations. Modern numerical techniques include the Finite Element Method, Finite Volume Method, Boundary Element Method, as well as Finite Difference Method. Likewise, the Topic covers approaches based on optimization algorithms, machine learning methods, and computer simulation techniques. Works on a variety of meshless or semi-analytical approaches are welcome together with those that address artificial intelligence or cellular automata models.

Interaction in between these two fields includes reliability engineering of (solar, geothermal or wind) energy systems, computer analysis of various coupled phenomena in engineering, numerical solutions of various fluid and heat flow problems, as well as simulations of thermal, mechanical and electro-magnetic energy exchanges in modern engineering systems and structures. Numerical studies of energetic efficiency, optimization and durability of new technical solutions are especially welcome, including hybrid energy harvesting.

All contributions related to numerical sensitivity analysis, as well as analyses of statistical scattering or stochastic phenomena in different forms of energy exchanges, are invited also. Semi-analytical approaches in energy numerical analysis are understood as computer programs written in conjunction with computer algebra systems and their applications to deliver energy and its exchange determination for some specific applications.

Manuscripts from both academia, research and development laboratories, industry and also from small companies are invited to this topic collection.

Prof. Dr. Marcin Kamiński
Prof. Dr. Angel A. Juan
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Energies energies	3.2	5.5	2008	16.1 Days	CHF 2600
Mathematics mathematics	2.4	3.5	2013	16.9 Days	CHF 2600
Sci sci	-	3.1	2019	47.7 Days	CHF 1200

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Published Papers (44 papers)

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17 pages, 12746 KiB  

Open AccessArticle

Numerical Investigation and Optimization of Cooling Flow Field Design for Proton Exchange Membrane Fuel Cell

by Jiangnan Song, Ying Huang, Yi Liu, Zongpeng Ma, Lunjun Chen, Taike Li and Xiang Zhang

Energies 2022, 15(7), 2609; https://doi.org/10.3390/en15072609 - 02 Apr 2022

Cited by 7 | Viewed by 2225

Abstract

High temperatures and non-uniform temperatures both have a negative bearing on the performance of proton exchange membrane fuel cells. The temperature of proton exchange membrane fuel cells can be lowered by reasonably distributed cooling channels. The flow field distribution of five different cooling [...] Read more.

High temperatures and non-uniform temperatures both have a negative bearing on the performance of proton exchange membrane fuel cells. The temperature of proton exchange membrane fuel cells can be lowered by reasonably distributed cooling channels. The flow field distribution of five different cooling plates is designed, and the temperature uniformity, pressure drop and velocity of each cooling flow field are analyzed by computational fluid dynamics technology. The results show that while the pressure drop is high, the flow channel distribution of a multi-spiral flow field and honeycomb structure flow field contribute more to improving the temperature uniformity. As the coolant is blocked by the uniform plate, it is found that although the flow field channel with a uniform plate has poor performance in terms of temperature uniformity, its heat dissipation capacity is still better than that of the traditional serpentine flow field. The multi-spiral flow field has the strongest ability to maintain the temperature stability in the cooling plate when the heat flux increases. The increase in Reynolds number, although increasing the pressure drop, can reduce the maximum temperature and temperature difference of the flow field, ameliorate the temperature uniformity and improve the heat transfer capacity of the cooling plate. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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18 pages, 7918 KiB  

Open AccessArticle

Derivative Probes Signal Integration Techniques for High Energy Pulses Measurements

by Adam Jóśko, Bogdan Dziadak, Jacek Starzyński and Jan Sroka

Energies 2022, 15(6), 2244; https://doi.org/10.3390/en15062244 - 18 Mar 2022

Cited by 1 | Viewed by 1575

Abstract

The paper presents problems related to the processing of signals recorded with differential field probes E and H. The fundamental problem to which special attention has been paid is the result of the integration operation. Due to the presence of constant/slowly-varying components in [...] Read more.

The paper presents problems related to the processing of signals recorded with differential field probes E and H. The fundamental problem to which special attention has been paid is the result of the integration operation. Due to the presence of constant/slowly-varying components in the raw signal, there is a drift present in the outcome of integration. This line wander can be enormous. This is particularly evident if the integration is performed in a standard manner, uniformly over the entire recorded waveform. The paper contains the Authors’ proposition to segment the signal and perform the integration independently in each of the sub-regions. This approach is based on the assumption of a local mean value instead of its global character for the recorded waveform. Although this leads to more complex signal processing, it gives significantly better results as it is suppressing the deterioration drift in the integrated signal more than 400 times. The results are presented on laboratory recordings and outdoor tests. In the first case, voltage pulses with durations of about 50 ns and rise times in the range of single ns were recorded. In the second case, high-energy electromagnetic pulse signals were used. It was formed by sinusoidal waveforms packets of 3 GHz frequency with a single packet duration of 5 μs and packet repetition frequency f ≤ 300 Hz. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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16 pages, 6512 KiB  

Open AccessArticle

Numerical Study on Flow and Heat Transfer Characteristics of Supercritical CO₂ in Zigzag Microchannels

by Yi Tu and Yu Zeng

Energies 2022, 15(6), 2099; https://doi.org/10.3390/en15062099 - 13 Mar 2022

Cited by 4 | Viewed by 2077

Abstract

The zigzag channel is the uppermost channel type of an industrial printed circuit heat exchanger (PCHE). The effect of geometric properties on the flow and heat transfer performance of the channel is significant to the PCHE design and optimization. Numerical investigations were conducted [...] Read more.

The zigzag channel is the uppermost channel type of an industrial printed circuit heat exchanger (PCHE). The effect of geometric properties on the flow and heat transfer performance of the channel is significant to the PCHE design and optimization. Numerical investigations were conducted on the flow and heat transfer characteristics of supercritical CO₂ (sCO₂) in semicircular zigzag channels by computational fluid dynamics method. The shear stress transfer (SST) k–ω model was used as turbulence model and the National Institute of Standards and Technology (NIST) real gas model with REFPROP database was used to evaluate the thermophysical parameters of sCO₂ in this numerical method. The effectiveness of the simulation method is verified by experimental data. Thermal hydraulic performance for zigzag channels with different pitch lengths, bending angles, and hydraulic diameters are studied comparatively based on this numerical method, with the boundary conditions which cover the pseudocritical point. The comparison results show that reducing the bending angle and pitch length will strengthen the effect of boundary layer separation on the leeward side of the wall and enhance the heat transfer performance, but the pressure drop of the channel will also increase, and the decrease of channel hydraulic diameter is beneficial to the heat transfer enhancement, but it is not as significant as that of the straight channel. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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30 pages, 1995 KiB  

Open AccessArticle

Evaluation of Interpolation Scheme Alternatives and Variation of the Number of Slave Cells in a Cut-Cell Methodology

by Luis Henríquez-Vargas, Francisco Angel, Lawrence Lackey and Pablo Donoso-García

Mathematics 2022, 10(6), 895; https://doi.org/10.3390/math10060895 - 11 Mar 2022

Viewed by 1670

Abstract

The present work determines numerical solutions applied to flow problems in a cut-cell framework, introducing and evaluating two interpolation alternatives for the treatment of the convective terms and the effect of the variation of the number of slave cells generated near the solid [...] Read more.

The present work determines numerical solutions applied to flow problems in a cut-cell framework, introducing and evaluating two interpolation alternatives for the treatment of the convective terms and the effect of the variation of the number of slave cells generated near the solid interfaces. Using the upwind, QUICK and WAHYD (TVD) schemes, three benchmark cases were studied in the laminar regime, namely, flow between concentric cylindrical walls, flow in an inclined channel and flow around a cylinder. The numerical results obtained were favorable for the proposed interpolation methodology that prevents velocity over/under-estimations on the finite control volume faces, observing a tendency to produce smaller errors and mid-to-high computational efficiencies when coupled with a smaller number of slave cells generated at the boundaries. Although the magnitude of the errors found were small, improvements are of more significance for quantities that depend on gradient estimations at surfaces. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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18 pages, 714 KiB  

Open AccessArticle

On the Dynamic Connectedness of the Stock, Oil, Clean Energy, and Technology Markets

by Amirreza Attarzadeh and Mehmet Balcilar

Energies 2022, 15(5), 1893; https://doi.org/10.3390/en15051893 - 04 Mar 2022

Cited by 10 | Viewed by 2686

Abstract

Using monthly data from September 2004 to February 2020, this paper investigates the connectedness of the renewable energy, common stock, oil, and technology markets. The time-domain Diebold and Yilmaz spillover index approach is used to analyze the volatility spillover between these four markets. [...] Read more.

Using monthly data from September 2004 to February 2020, this paper investigates the connectedness of the renewable energy, common stock, oil, and technology markets. The time-domain Diebold and Yilmaz spillover index approach is used to analyze the volatility spillover between these four markets. The study’s findings reveal that the oil and clean energy markets have bidirectional volatility spillover. The oil market has been found to be a net receiver of volatility. Furthermore, the study shows that volatility spillover is stronger in extreme positive and negative shock periods than in medium shock periods. Our findings show that, during crisis periods, the volatility spillover index rises, while the total connection reached its lowest point in 2015. Our findings suggest that policymakers should be informed that, as long as oil prices remain low, alternative energy-producing industries will not require specific policies to mitigate their vulnerability to crude oil price shocks. However, large spillover in the tails—particularly in the right tail—indicates vulnerability to extreme events, such as the negative effect of oil price increases. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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15 pages, 2412 KiB  

Open AccessFeature PaperArticle

A Combined Experimental-Numerical Investigation of the Thermal Efficiency of the Vessel in Domestic Induction Systems

by Belén Bonet-Sánchez, Iulen Cabeza-Gil, Begoña Calvo, Jorge Grasa, Carlos Franco, Sergio Llorente and Miguel A. Martínez

Mathematics 2022, 10(5), 802; https://doi.org/10.3390/math10050802 - 03 Mar 2022

Cited by 1 | Viewed by 1683

Abstract

New studies are emerging to reduce energy costs and become a more sustainable society. One of the processes where the greatest savings can be made is in cooking, due to its large-scale global use. In this vein, this study aims to analyse the [...] Read more.

New studies are emerging to reduce energy costs and become a more sustainable society. One of the processes where the greatest savings can be made is in cooking, due to its large-scale global use. In this vein, this study aims to analyse the influence of the vessel in the thermal efficiency at the cooking process. For that purpose, a numerical model of a cooking vessel was designed and validated with three different experimental heating tests. One of the key factors of the process is the contact between the vessel and the glass, therefore, two new approaches to model the thermal contact between the vessel and the cooktop were explored. Once the numerical models were calibrated, a full factorial analysis was performed to quantify the influence of the key parameters of the vessel in the heating process during cooking (thermal conductivity, specific heat, convection and radiation coefficients, and vessel concavity). Two of the most influential parameters in the heating process are the conductivity and the thermal contact between the vessel and the glass. Higher cooking efficiency can be achieved both with a low thermal conductivity vessel and with a high concavity, i.e., increasing the isolation between the vessel and the glass. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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24 pages, 7857 KiB  

Open AccessArticle

Numerical Study of Heat Transfer in a Gun Barrel Made of Selected Steels

by Mateusz Zieliński, Piotr Koniorczyk, Zbigniew Surma, Janusz Zmywaczyk and Marek Preiskorn

Energies 2022, 15(5), 1868; https://doi.org/10.3390/en15051868 - 03 Mar 2022

Cited by 8 | Viewed by 2770

Abstract

The results of numerical simulations of transient heat transfer in the barrel wall of a 35 mm caliber cannon for a single shot and the sequences of seven shots and sixty shots for chosen barrel steels are presented. It was assumed that the [...] Read more.

The results of numerical simulations of transient heat transfer in the barrel wall of a 35 mm caliber cannon for a single shot and the sequences of seven shots and sixty shots for chosen barrel steels are presented. It was assumed that the cannon barrel was made of one of the three types of steel: 38HMJ (1.8509), 30HN2MFA and DUPLEX (1.4462). To model the thermal phenomena in the barrel, the barrel wall material was assumed to be homogeneous and the inner surface of the barrel had no protective chromium or nitride layer. The calculations were made for temperature-dependent thermophysical parameters, i.e., thermal conductivity, specific heat and thermal expansion (in the range from RT up to 1000 °C) of the selected barrel steels. A barrel with a total length of 3150 mm was divided into 6 zones (i = 1, …, 6) and in each of them, the heat flux density was calculated as a function of time ${\dot{q}}_i\left(t\right)$ on the inner surface of the barrel. Using lumped parameter methods, an internal ballistic code was developed to compute in each zone the heat transfer coefficient as a function of time h_i(t) and bore gas temperature as a function of time T_g(t) to the cannon barrel for given ammunition parameters. A calculation time equaling 100 ms per single shot was assumed. The results of the calculations were obtained using FEM implemented in COMSOL Multiphysics ver. 5.6 software. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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13 pages, 4311 KiB  

Open AccessArticle

Study on the Weakening Law and Classification of Rock Mass Damage under Blasting Conditions

by Rui Yue, Kegang Li, Qingci Qin, Mingliang Li and Meng Li

Energies 2022, 15(5), 1809; https://doi.org/10.3390/en15051809 - 01 Mar 2022

Cited by 1 | Viewed by 1714

Abstract

To study the effects of declining mechanical parameters caused by blasting excavation on slopes, we introduced the damage degree index D_s, and established a relationship between D_s and the disturbance factor D in the Hoek–Brown criterion, along with a basic quality [...] Read more.

To study the effects of declining mechanical parameters caused by blasting excavation on slopes, we introduced the damage degree index D_s, and established a relationship between D_s and the disturbance factor D in the Hoek–Brown criterion, along with a basic quality index BQ for the rock mass. We then explored the change law for the degree of rock damage D_s as a function of the disturbance factor D. We also used a phosphate mine slope in Guizhou Province for reference, and analyzed the process of damage evolution of the slope based on the RHT (Riedel-Hiermaier-Thoma Constitution) in LS-DYNA (Yunnan, China). Results showed a direct relationship between the GSI value in the Hoek–Brown criterion and the initial damage degree of the slope. As D_s increases, D increases exponentially. However, the compressive strength, elastic modulus, cohesion, and internal friction angle decreased nonlinearly, and the tensile strength of the rock mass decreased linearly. Among these parameters, the compressive strength decreased the most rapidly, while the internal friction angle decreased slowly. We also established a new grade for rock self-stabilization with D_s as the evaluation standard. Thus, these results may provide a theoretical basis for determining the mechanical properties of rocks for future slope protection and stability evaluations. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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11 pages, 1464 KiB  

Open AccessArticle

LambertW Function to Extract Physical Parameters of a Schottky Barrier Diode from Its I–V Characteristics

by Safae Aazou, Matthew Schuette White, Martin Kaltenbrunner, Zouheir Sekkat, Daniel Ayuk Mbi Egbe and El Mahdi Assaid

Energies 2022, 15(5), 1667; https://doi.org/10.3390/en15051667 - 23 Feb 2022

Cited by 1 | Viewed by 5161

Abstract

In the current work, the exact analytical expression of the current–voltage characteristics, which are given in terms of the $LambertW$ function, is used to extract the physical parameters of organic and inorganic Schottky barrier diodes (SBDs). [...] Read more.

In the current work, the exact analytical expression of the current–voltage characteristics, which are given in terms of the $LambertW$ function, is used to extract the physical parameters of organic and inorganic Schottky barrier diodes (SBDs). The extraction is achieved by a variety of methods using the experimental I–V characteristics. The organic SBD is based on a Poly (3-hexylthiophene-2,5-diyle) conjugated polymer (P3HT) with Al contact, measured at 300 K. Regarding the inorganic SBDs, one is based on Iridium–Silicon Carbide (Ir–SiC), measured at 300 K, and the second diode is based on Gold–Gallium Arsenide (Au–GaAs), measured at 200 K. The numerical characteristics based on the physical parameters extracted by the presented methods are in good agreement with the experimental data. The determination coefficient of the modeling methods for the three SBDs is higher than 99.99%. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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19 pages, 3067 KiB  

Open AccessArticle

Numerical Investigation of the Sensitivity of the Acoustic Power Level to Changes in Selected Design Parameters of an Axial Fan

by Dawid Romik and Ireneusz Czajka

Energies 2022, 15(4), 1357; https://doi.org/10.3390/en15041357 - 14 Feb 2022

Cited by 5 | Viewed by 1627

Abstract

The noise generated by different types of fans used in the turbomachinery industry is a topic that has been studied for many years. However, researchers are still looking for a universal solution to reduce noise while maintaining the performance of these machines. This [...] Read more.

The noise generated by different types of fans used in the turbomachinery industry is a topic that has been studied for many years. However, researchers are still looking for a universal solution to reduce noise while maintaining the performance of these machines. This paper, as a contribution to the research, presents the results of numerical investigations of an axial fan installed in a pipeline with a circular cross-section. In particular, the focus was on investigating the sensitivity of the sound power level to changes in selected design and operational parameters of this fan. The simulation studies used the unsteady Reynolds-averaged Navier–Stokes (URANS) approach and the Ffowcs Williams–Hawkings (FW-H) analogy implemented in Ansys Fluent. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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18 pages, 4655 KiB  

Open AccessArticle

Wind Speed Forecasts of a Mesoscale Ensemble for Large-Scale Wind Farms in Northern China: Downscaling Effect of Global Model Forecasts

by Jianqiu Shi, Yubao Liu, Yang Li, Yuewei Liu, Gregory Roux, Lan Shi and Xiaowei Fan

Energies 2022, 15(3), 896; https://doi.org/10.3390/en15030896 - 26 Jan 2022

Cited by 6 | Viewed by 2100

Abstract

To facilitate wind power integration for the electric power grid operated by the Inner Mongolia Electric Power Corporation—a major electric power grid in China—a high-resolution (of 2.7 km grid intervals) mesoscale ensemble prediction system was developed that forecasts winds for 130 wind farms [...] Read more.

To facilitate wind power integration for the electric power grid operated by the Inner Mongolia Electric Power Corporation—a major electric power grid in China—a high-resolution (of 2.7 km grid intervals) mesoscale ensemble prediction system was developed that forecasts winds for 130 wind farms in the Inner Mongolia Autonomous Region. The ensemble system contains 39 forecasting members that are divided into 3 groups; each group is composed of the NCAR (National Center for Atmospheric Research) real-time four-dimensional data assimilation and forecasting model (RTFDDA) with 13 physical perturbation members, but driven by the forecasts of the GFS (Global Forecast System), GEM (Global Environmental Multiscale Model), and GEOS (Goddard Earth Observing System), respectively. The hub-height wind predictions of these three sub-ensemble groups at selected wind turbines across the region were verified against the hub-height wind measurements. The forecast performance and variations with lead time, wind regimes, and diurnal and regional changes were analyzed. The results show that the GFS group outperformed the other two groups with respect to correlation coefficient and mean absolute error. The GFS group had the most accurate forecasts in ~59% of sites, while the GEOS and GEM groups only performed the best on 34% and 2% of occasions, respectively. The wind forecasts were most accurate for wind speeds ranging from 3 to 12 m/s, but with an overestimation for low speeds and an underestimation for high speeds. The GEOS-driven members obtained the least bias error among the three groups. All members performed rather accurately in daytime, but evidently overestimated the winds during nighttime. The GFS group possessed the fewest diurnal errors, and the bias of the GEM group grew significantly during nighttime. The wind speed forecast errors of all three ensemble members increased with the forecast lead time, with the average absolute error increasing by ~0.3 m/s per day during the first 72 h of forecasts. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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17 pages, 5188 KiB  

Open AccessArticle

Convergence Investigation of XFEM Enrichment Schemes for Modeling Cohesive Cracks

by Guangzhong Liu, Jiamin Guo and Yan Bao

Mathematics 2022, 10(3), 383; https://doi.org/10.3390/math10030383 - 26 Jan 2022

Viewed by 2104

Abstract

When simulating cohesive cracks in the XFEM framework, specific enrichment schemes are designed for the non-singular near-tip field and an iteration procedure is used to solve the nonlinearity problem. This paper focuses on convergence and accuracy analysis of XFEM enrichment schemes for cohesive [...] Read more.

When simulating cohesive cracks in the XFEM framework, specific enrichment schemes are designed for the non-singular near-tip field and an iteration procedure is used to solve the nonlinearity problem. This paper focuses on convergence and accuracy analysis of XFEM enrichment schemes for cohesive cracks. Four different kinds of enrichment schemes were manufactured based on the development of XFEM. A double-cantilever beam specimen under an opening load was simulated by Matlab programming, assuming both linear and exponential constitutive models. The displacement and load factors were solved simultaneously by the Newton–Raphson iterative procedure. Finally, based on a linear or an exponential constitutive law, the influences of variations in these enrichment schemes, including (i) specialized tip branch functions and (ii) corrected approximations for blending elements, were determined and some conclusions were drawn. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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18 pages, 9250 KiB  

Open AccessArticle

Analysis of Air Pollution around a CHP Plant: Real Measurements vs. Computer Simulations

by Robert Cichowicz and Maciej Dobrzański

Energies 2022, 15(2), 553; https://doi.org/10.3390/en15020553 - 13 Jan 2022

Cited by 7 | Viewed by 1581

Abstract

This study examines the concentrations of air pollution in the vicinity of a combined heat and power plant (CHP) and a communication route, using computer modeling of pollutant dispersion and spatial analysis based on real measurements in the city of Łódź, Poland, Europe. [...] Read more.

This study examines the concentrations of air pollution in the vicinity of a combined heat and power plant (CHP) and a communication route, using computer modeling of pollutant dispersion and spatial analysis based on real measurements in the city of Łódź, Poland, Europe. The research takes into account the concentrations of particulate matter (PM₁₀, PM_2.5, PM_1.0) and gaseous pollutants (SO₂ and VOC) in winter and summer. The spatial distribution of pollutants is discussed, including the presence of areas with increased accumulations of pollutants. Because atmospheric air has no natural boundaries, when analyzing any location, not only local sources of pollution, but also background pollution, should be analyzed. A clear difference was observed between the concentrations of pollutants in the summer and winter seasons, with significantly higher concentrations in the winter (heating) period. The impacts of road transport, individual heating systems, and combined heat and power plants were also assessed. Computer calculations confirmed that road transport accounted for the largest share of both PM and SO₂ emissions. The CHP plant was responsible for the smallest percentage of dust emissions and was the next largest producer of SO₂ emissions. The share of the total emissions from the individual sources were compared with the results of detailed field tests. The numerical analysis of selected pollution sources in combination with the field analysis shows that the identified pollution sources included in the analysis represent only a part of the total observed pollutant concentrations (suggesting that other background sources account for the rest). Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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13 pages, 5597 KiB  

Open AccessArticle

Study of the Harmonic Analysis and Energy Transmission Mechanism of the Frequency Conversion Transformer

by Zhonghuan Su, Longfu Luo, Jun Liu, Zhongxiang Li, Hu Luo and Peng Zhao

Energies 2022, 15(2), 519; https://doi.org/10.3390/en15020519 - 12 Jan 2022

Viewed by 1476

Abstract

Since the transmission distance of submarine cable transmission is inversely proportional to the input frequency, to solve the problem of large losses in the transmission process of offshore wind power, this paper proposes a three-frequency transformer which enables the output of 50 Hz [...] Read more.

Since the transmission distance of submarine cable transmission is inversely proportional to the input frequency, to solve the problem of large losses in the transmission process of offshore wind power, this paper proposes a three-frequency transformer which enables the output of 50 Hz at the input of 50/3 Hz excitation. In this paper, the magnetic flux of a three-dimensional wound core transformer is analytically modeled, the existing condition of magnetic flux harmonics of a three-dimensional wound core transformer is analyzed, the distribution of harmonic content in magnetic flux is obtained, and the principle of realizing frequency conversion is expounded. Secondly, the finite element analysis of the frequency converter is carried out. Finally, a prototype of a frequency transformer is made and tested to verify the correctness of the proposed scheme. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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15 pages, 4976 KiB  

Open AccessArticle

Residential Short-Term Load Forecasting during Atypical Consumption Behavior

by Cristina Hora, Florin Ciprian Dan, Gabriel Bendea and Calin Secui

Energies 2022, 15(1), 291; https://doi.org/10.3390/en15010291 - 01 Jan 2022

Cited by 5 | Viewed by 1578

Abstract

Short-term load forecasting (STLF) is a fundamental tool for power networks’ proper functionality. As large consumers need to provide their own STLF, the residential consumers are the ones that need to be monitored and forecasted by the power network. There is a huge [...] Read more.

Short-term load forecasting (STLF) is a fundamental tool for power networks’ proper functionality. As large consumers need to provide their own STLF, the residential consumers are the ones that need to be monitored and forecasted by the power network. There is a huge bibliography on all types of residential load forecast in which researchers have struggled to reach smaller forecasting errors. Regarding atypical consumption, we could see few titles before the coronavirus pandemic (COVID-19) restrictions, and afterwards all titles referred to the case of COVID-19. The purpose of this study was to identify, among the most used STLF methods—linear regression (LR), autoregressive integrated moving average (ARIMA) and artificial neural network (ANN)—the one that had the best response in atypical consumption behavior and to state the best action to be taken during atypical consumption behavior on the residential side. The original contribution of this paper regards the forecasting of loads that do not have reference historic data. As the most recent available scenario, we evaluated our forecast with respect to the database of consumption behavior altered by different COVID-19 pandemic restrictions and the cause and effect of the factors influencing residential consumption, both in urban and rural areas. To estimate and validate the results of the forecasts, multiyear hourly residential consumption databases were used. The main findings were related to the huge forecasting errors that were generated, three times higher, if the forecasting algorithm was not set up for atypical consumption. Among the forecasting algorithms deployed, the best results were generated by ANN, followed by ARIMA and LR. We concluded that the forecasting methods deployed retained their hierarchy and accuracy in forecasting error during atypical consumer behavior, similar to forecasting in normal conditions, if a trigger/alarm mechanism was in place and there was sufficient time to adapt/deploy the forecasting algorithm. All results are meant to be used as best practices during power load uncertainty and atypical consumption behavior. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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19 pages, 2943 KiB  

Open AccessArticle

Innovative Construction of the AFPM-Type Electric Machine and the Method for Estimation of Its Performance Parameters on the Basis of the Induction Voltage Shape

by Andrzej Smoleń, Lesław Gołębiowski and Marek Gołębiowski

Energies 2022, 15(1), 236; https://doi.org/10.3390/en15010236 - 30 Dec 2021

Viewed by 1154

Abstract

The article presents an innovative construction of the Axial Flux Permanent Magnet (AFPM) machine designed for generator performance, which provides the shape of induced voltage that enables estimation of the speed and rotational angle of the machine rotor. Design solutions were proposed, the [...] Read more.

The article presents an innovative construction of the Axial Flux Permanent Magnet (AFPM) machine designed for generator performance, which provides the shape of induced voltage that enables estimation of the speed and rotational angle of the machine rotor. Design solutions were proposed, the aim of which is to limit energy losses as a result of the occurrence of eddy currents. The method of direct estimation of the value of the rotational speed and rotational angle of the machine rotor was proposed and investigated on the basis of the measurements of induced voltages and machine phase currents. The advantage of the machine is the utilization of simple and easy-to-use computational procedures. The acquired results were compared with the results obtained for estimation performed by using the Unscented Kalman Filter (UKF). Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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17 pages, 13617 KiB  

Open AccessArticle

A Case Study: Sediment Erosion in Francis Turbines Operated at the San Francisco Hydropower Plant in Ecuador

by Cristian Cruzatty, Darwin Jimenez, Esteban Valencia, Ivan Zambrano, Christian Mora, Xianwu Luo and Edgar Cando

Energies 2022, 15(1), 8; https://doi.org/10.3390/en15010008 - 21 Dec 2021

Cited by 6 | Viewed by 2078

Abstract

The operation of various types of turbomachines is importantly affected by sediment erosion. Francis turbines used for power generation typically suffer said effects due to the fact that they are used in sediment-laden rivers and are usually operated disregarding the long-term effect of [...] Read more.

The operation of various types of turbomachines is importantly affected by sediment erosion. Francis turbines used for power generation typically suffer said effects due to the fact that they are used in sediment-laden rivers and are usually operated disregarding the long-term effect of the erosion on turbine performance. This investigation seeks to study the erosion rate for the main components of the turbines located at San Francisco hydropower plant in Pastaza, Ecuador. A sediment characterization study was performed in order to determine the properties of the particles present in Pastaza River and accurately predict their effect on the turbine flow passages. A numerical approach combining liquid–solid two-phase flow simulation and an erosion model was used to analyze the erosion rates at different operating conditions and determine wear patterns in the components. As expected, the results indicated that an increase in the erosion rate was obtained for higher intake flows. However, a dramatic increase in the erosion rate was observed when the turbine was operated at near-full-load conditions, specifically when guide vane opening exceeded a 90% aperture. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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19 pages, 14905 KiB  

Open AccessArticle

A Multimodal Improved Particle Swarm Optimization for High Dimensional Problems in Electromagnetic Devices

by Rehan Ali Khan, Shiyou Yang, Shafiullah Khan, Shah Fahad and Kalimullah

Energies 2021, 14(24), 8575; https://doi.org/10.3390/en14248575 - 20 Dec 2021

Cited by 5 | Viewed by 2577

Abstract

Particle Swarm Optimization (PSO) is a member of the swarm intelligence-based on a metaheuristic approach which is inspired by the natural deeds of bird flocking and fish schooling. In comparison to other traditional methods, the model of PSO is widely recognized as a [...] Read more.

Particle Swarm Optimization (PSO) is a member of the swarm intelligence-based on a metaheuristic approach which is inspired by the natural deeds of bird flocking and fish schooling. In comparison to other traditional methods, the model of PSO is widely recognized as a simple algorithm and easy to implement. However, the traditional PSO’s have two primary issues: premature convergence and loss of diversity. These problems arise at the latter stages of the evolution process when dealing with high-dimensional, complex and electromagnetic inverse problems. To address these types of issues in the PSO approach, we proposed an Improved PSO (IPSO) which employs a dynamic control parameter as well as an adaptive mutation mechanism. The main proposal of the novel adaptive mutation operator is to prevent the diversity loss of the optimization process while the dynamic factor comprises the balance between exploration and exploitation in the search domain. The experimental outcomes achieved by solving complicated and extremely high-dimensional optimization problems were also validated on superconducting magnetic energy storage devices (SMES). According to numerical and experimental analysis, the IPSO delivers a better optimal solution than the other solutions described, particularly in the early computational evaluation of the generation. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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15 pages, 5974 KiB  

Open AccessArticle

General 3D Analytical Method for Eddy-Current Coupling with Halbach Magnet Arrays Based on Magnetic Scalar Potential and H-Functions

by Xiaoquan Lu, Xinyi He, Ping Jin, Qifeng Huang, Shihai Yang and Mingming Chen

Energies 2021, 14(24), 8458; https://doi.org/10.3390/en14248458 - 15 Dec 2021

Cited by 3 | Viewed by 1970

Abstract

Rapid and accurate eddy-current calculation is necessary to analyze eddy-current couplings (ECCs). This paper presents a general 3D analytical method for calculating the magnetic field distributions, eddy currents, and torques of ECCs with different Halbach magnet arrays. By using Fourier decomposition, the magnetization [...] Read more.

Rapid and accurate eddy-current calculation is necessary to analyze eddy-current couplings (ECCs). This paper presents a general 3D analytical method for calculating the magnetic field distributions, eddy currents, and torques of ECCs with different Halbach magnet arrays. By using Fourier decomposition, the magnetization components of Halbach magnet arrays are determined. Then, with a group of H-formulations in the conductor region and Laplacian equations with magnetic scalar potential in the others, analytical magnetic field distributions are predicted and verified by 3D finite element models. Based on Ohm’s law for moving conductors, eddy-current distributions and torques are obtained at different speeds. Finally, the Halbach magnet arrays with different segments are optimized to enhance the fundamental amplitude and reduce the harmonic contents of air-gap flux densities. The proposed method shows its correctness and validation in analyzing and optimizing ECCs with Halbach magnet arrays. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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14 pages, 3936 KiB  

Open AccessArticle

Numerical Analysis of Heat Transfer Performances of Ionic Liquid and Ionanofluids with Temperature-Dependent Thermophysical Properties

by Amra Hasečić, Jaber Hmoud Almutairi, Siniša Bikić and Ejub Džaferović

Energies 2021, 14(24), 8420; https://doi.org/10.3390/en14248420 - 14 Dec 2021

Viewed by 1733

Abstract

The heat transfer performances of ionic liquids [C₄mpyrr][NTf₂] and ionanofluids with Al₂O₃ nanoparticles under a laminar flow regime, and with constant heat flux on the tube wall is numerically modeled and analyzed for three values of [...] Read more.

The heat transfer performances of ionic liquids [C₄mpyrr][NTf₂] and ionanofluids with Al₂O₃ nanoparticles under a laminar flow regime, and with constant heat flux on the tube wall is numerically modeled and analyzed for three values of initial/inlet temperature and for two Reynolds numbers. Heat transfer characteristics were considered by analyzing the temperature distribution along the upper wall, as well as by analyzing the Nusselt number and heat transfer coefficient. The results obtained numerically were validated using Shah’s equation for ionic liquid. Thermophysical properties were temperature-dependent, and obtained by curve-fitting the experimental values of the thermophysical properties. Furthermore, the same set of results was calculated for the ionic liquid and ionanofluids with constant thermophysical properties. It is concluded that the assumption that thermophysical properties are constant has a significant influence on the heat transfer performance parameters of both ionic liquid and ionanofluids, and therefore such assumptions should not be made in research. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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15 pages, 4058 KiB  

Open AccessArticle

Comparing 2D and 3D Solar Radiation Modeling in Urban Areas

by Štefan Kolečanský, Jaroslav Hofierka, Jozef Bogľarský and Jozef Šupinský

Energies 2021, 14(24), 8364; https://doi.org/10.3390/en14248364 - 11 Dec 2021

Cited by 3 | Viewed by 3037

Abstract

The use of solar radiation in the urban environment is becoming increasingly important for the sustainable development of cities and human societies. Several factors influence the distribution of solar radiation in urban areas, including urban morphology and the physical properties of urban materials. [...] Read more.

The use of solar radiation in the urban environment is becoming increasingly important for the sustainable development of cities and human societies. Several factors influence the distribution of solar radiation in urban areas, including urban morphology and the physical properties of urban materials. Most of these factors can be modeled with a relatively high accuracy using 2D and 3D solar radiation models. In this paper, the r.sun and v.sun solar radiation models are used to calculate solar radiation for the city of Košice in Eastern Slovakia to assess the accuracy of both approaches for vertical surfaces frequently found in urban areas. The results were validated by pyranometer measurements. The results showed relatively good estimates by the 3D v.sun model and poor estimates by the 2D r.sun model. This can be attributed to an improper representation of vertical surfaces by a digital surface model, which has a strong impact on solar resource assessments. We found that 3D city models prepared in level of detail 2 (LoD2) are not always adequate in case of complex buildings with morphological structures, such as terraces. These cast shadows on facades especially when solar altitude is high and, thus, assessments, even by a 3D model, are inaccurate. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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15 pages, 4117 KiB  

Open AccessArticle

Application of Artificial Neural Networks in the Urban Building Energy Modelling of Polish Residential Building Stock

by Marcin Zygmunt and Dariusz Gawin

Energies 2021, 14(24), 8285; https://doi.org/10.3390/en14248285 - 09 Dec 2021

Cited by 6 | Viewed by 1568

Abstract

The development of energy-efficient buildings and sustainable energy supply systems is an obligatory undertaking towards a more sustainable future. To protect the natural environment, the modernization of urban infrastructure is indisputably important, possible to achieve considering numerous buildings as a group, i.e., Building [...] Read more.

The development of energy-efficient buildings and sustainable energy supply systems is an obligatory undertaking towards a more sustainable future. To protect the natural environment, the modernization of urban infrastructure is indisputably important, possible to achieve considering numerous buildings as a group, i.e., Building Energy Cluster (BEC). The urban planning process evaluates multiple complex criteria to select the most profitable scenario in terms of energy consumption, environmental protection, or financial profitability. Thus, Urban Building Energy Modelling (UBEM) is presently a popular approach applied for studies towards the development of sustainable cities. Today’s UBEM tools use various calculation methods and approaches, as well as include different assumptions and limitations. While there are several popular and valuable software for UBEM, there is still no such tool for analyses of the Polish residential stock. In this work an overview on the home-developed tool called TEAC, focusing on its’ mathematical model and use of Artificial Neural Networks (ANN). An exemplary application of the TEAC software is also presented. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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20 pages, 885 KiB  

Open AccessArticle

Modeling, Simulation, and Analysis of a Variable-Length Pendulum Water Pump

by Godiya Yakubu, Paweł Olejnik and Jan Awrejcewicz

Energies 2021, 14(23), 8064; https://doi.org/10.3390/en14238064 - 02 Dec 2021

Cited by 5 | Viewed by 2020

Abstract

Due to the long-term problem of electricity and potable water in most developing and undeveloped countries, predominantly rural areas, a novelty of the pendulum water pump, which uses a vertically excited parametric pendulum with variable-length using a sinusoidal excitation as a vibrating machine, [...] Read more.

Due to the long-term problem of electricity and potable water in most developing and undeveloped countries, predominantly rural areas, a novelty of the pendulum water pump, which uses a vertically excited parametric pendulum with variable-length using a sinusoidal excitation as a vibrating machine, is presented. With this, more oscillations can be achieved, reducing human effort further and having high output than the existing pendulum water pump with the conventional pendulum. The pendulum, lever, and piston assembly are modeled by a separate dynamical system and then joined into the many degrees-of-freedom dynamical systems. The present work includes friction while studying the system dynamics and then simulated to verify the system’s harmonic response. The study showed the effect of the pendulum length variability on the whole system’s performance. The vertically excited parametric pendulum with variable length in the system is established, giving faster and longer oscillations than the pendulum with constant length. Hence, more and richer dynamics are achieved. A quasi-periodicity behavior is noticed in the system even after 50 s of simulation time; this can be compensated when a regular external forcing is applied. Furthermore, the lever and piston oscillations show a transient behavior before it finally reaches a stable behavior. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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24 pages, 7294 KiB  

Open AccessArticle

Designing a Solar Photovoltaic System for Generating Renewable Energy of a Hospital: Performance Analysis and Adjustment Based on RSM and ANFIS Approaches

by Rami Alamoudi, Osman Taylan, Mehmet Azmi Aktacir and Enrique Herrera-Viedma

Mathematics 2021, 9(22), 2929; https://doi.org/10.3390/math9222929 - 17 Nov 2021

Cited by 7 | Viewed by 2589

Abstract

One of the most favorable renewable energy sources, solar photovoltaic (PV) can meet the electricity demand considerably. Sunlight is converted into electricity by the solar PV systems using cells containing semiconductor materials. A PV system is designed to meet the energy needs of [...] Read more.

One of the most favorable renewable energy sources, solar photovoltaic (PV) can meet the electricity demand considerably. Sunlight is converted into electricity by the solar PV systems using cells containing semiconductor materials. A PV system is designed to meet the energy needs of King Abdulaziz University Hospital. A new method has been introduced to find optimal working capacity, and determine the self-consumption and sufficiency rates of the PV system. Response surface methodology (RSM) is used for determining the optimal working conditions of PV panels. Similarly, an adaptive neural network based fuzzy inference system (ANFIS) was employed to analyze the performance of solar PV panels. The outcomes of methods were compared to the actual outcomes available for testing the performance of models. Hence, for a 40 MW target PV system capacity, the RSM determined that approximately 33.96 MW electricity can be produced, when the radiation rate is 896.3 W/m², the module surface temperature is 41.4 °C, the outdoor temperature is 36.2 °C, the wind direction and speed are 305.6 and 6.7 m/s, respectively. The ANFIS model (with nine rules) gave the highest performance with lowest residual for the same design parameters. Hence, it was determined that the hourly electrical energy requirement of the hospital can be met by the PV system during the year. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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16 pages, 4658 KiB  

Open AccessArticle

Application of Empirical Mode Decomposition and Extreme Learning Machine Algorithms on Prediction of the Surface Vibration Signal

by Yan Shen, Ping Wang, Xuesong Wang and Ke Sun

Energies 2021, 14(22), 7519; https://doi.org/10.3390/en14227519 - 11 Nov 2021

Cited by 3 | Viewed by 1478

Abstract

Accurately predicting surface vibration signals of diesel engines is the key to evaluating the operation quality of diesel engines. Based on an improved empirical mode decomposition and extreme learning machine algorithm, the characteristics of diesel engine surface vibration signal were detected, predicted, and [...] Read more.

Accurately predicting surface vibration signals of diesel engines is the key to evaluating the operation quality of diesel engines. Based on an improved empirical mode decomposition and extreme learning machine algorithm, the characteristics of diesel engine surface vibration signal were detected, predicted, and analyzed. First, the surface vibration signal was decomposed into a series of signal components by an improved empirical mode decomposition algorithm. Then, the extreme learning machine algorithm was applied to each signal component to obtain the predicted value of the corresponding signal component and determine the characteristics of the ground vibration signal. Compared with the empirical mode decomposition–extremum learning machine algorithm and the extremum learning machine algorithm, the results show that the improved empirical mode decomposition–extremum learning machine algorithm is feasible and effective. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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29 pages, 3566 KiB  

Open AccessArticle

Evaluation on Coupling of Wall Boiling and Population Balance Models for Vertical Gas-Liquid Subcooled Boiling Flow of First Loop of Nuclear Power Plant

by Guang Hu, Yue Ma and Qianfeng Liu

Energies 2021, 14(21), 7357; https://doi.org/10.3390/en14217357 - 05 Nov 2021

Cited by 6 | Viewed by 1600

Abstract

An accurate prediction of the interphase behaviors of the vertical gas-liquid subcooled boiling flow is meaningful for the first loop of a nuclear power plant (NPP). Therefore, the interphase behaviors including the bubble size distribution in the first loop of the NPP are [...] Read more.

An accurate prediction of the interphase behaviors of the vertical gas-liquid subcooled boiling flow is meaningful for the first loop of a nuclear power plant (NPP). Therefore, the interphase behaviors including the bubble size distribution in the first loop of the NPP are analyzed, evaluated, and validated using various wall boiling models coupled with the population balance model (PBM) kernels in this paper. Firstly, nondimensional numbers of the first loop of the NPP and DEBORA (Development of Borehole Seals for High-Level Radioactive Waste) experiment test cases are analyzed with approximation. Secondly, five active nucleation site density models N_n coupled with the PBM kernel combination, four kernel combinations (C1~C4) with the N_n models are calculated and analyzed. Lastly, various behaviors including the bubble size distribution Sauter mean diameter (SMD) d_p, void fraction α, gas superficial velocity j_g, and liquid superficial velocity j_l are compared and validated with the experimental data of the DEBORA-1 (P = 2.62 MPa). The results indicate that the two N_n models are suitable for the calculations of thefirst loop of the nuclear power plant. For instance, for the bubble size distribution SMD d_p, the specified N_n model with C1 (maximum relative error 9.63%) has relatively better behaviors for the first loop of the NPP. Especially, the combination C1 is applicable for the calculation of the bubble size distribution d_p, void fraction α and liquid superficial velocity j_l while C4 is suitable for the calculation of the gas superficial velocity j_g. These results can provide guidance for the numerical computation of the subcooled boiling flow in the first loop of the NPP. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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21 pages, 3904 KiB  

Open AccessArticle

Investigation of Optimization of Combustion Processes in the Engine of Combat Vehicles by Use of Disk Structure

by Igor Korobiichuk, Viktorij Mel’nick, Volodimir Karachun and Vladyslav Shybetskyi

Energies 2021, 14(21), 7039; https://doi.org/10.3390/en14217039 - 27 Oct 2021

Cited by 3 | Viewed by 1355

Abstract

This work analyzes the possibility of a provision of force-majeure mode of the combat vehicles with the aid of disk construction installed in the baffler, the base of the operation of which is the method of residual cyclical quadratic chain code of construction [...] Read more.

This work analyzes the possibility of a provision of force-majeure mode of the combat vehicles with the aid of disk construction installed in the baffler, the base of the operation of which is the method of residual cyclical quadratic chain code of construction of the “windows” of the movable disk. To determine the optimal parameters of the moving disk of the rotor system, mathematical modeling was performed. The results of mathematical modeling were used to create a PC-based calculation program. The calculation was performed for the rotational frequency ω = 300 s⁻¹ andfor harmonic numbers from 1 to 100. The waveforms used in simulation were as follows: quasi-trapezoidal and rectangular. It is established that at the number of “windows” m = 276 in the moving disk of the rotor system the radiation spectrum acquires a uniform distribution. The object of the research is the process of extreme burning of fuel material in the combat vehicles’ engines, ensuring, according to the technical possibilities of the engine, the implementation of the force-majeure mode of the combat vehicle in the whole. The quantitative and qualitative criteria of fullness of fuel material burning in the engine are chosen as the basis for the evaluation of the reaching of the force-majeure mode. The “flat noise” of the efflux is chosen as the basis of this evaluation. This method ensures the construction of the stochastic structure of “flat noise” in the engine efflux and, in that way, confirms the possibility of technical implementation of the force-majeure mode. The rotor system further ensures not only the force-majeure formation, but also reaches the minimum noise of the combat vehicle at the change of its dislocation. The research results can be further used to optimize the design of exhaust systems, which will reduce emissions. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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18 pages, 9988 KiB  

Open AccessArticle

Small-Scale Solar Photovoltaic Power Prediction for Residential Load in Saudi Arabia Using Machine Learning

by Mohamed Mohana, Abdelaziz Salah Saidi, Salem Alelyani, Mohammed J. Alshayeb, Suhail Basha and Ali Eisa Anqi

Energies 2021, 14(20), 6759; https://doi.org/10.3390/en14206759 - 17 Oct 2021

Cited by 17 | Viewed by 2900

Abstract

Photovoltaic (PV) systems have become one of the most promising alternative energy sources, as they transform the sun’s energy into electricity. This can frequently be achieved without causing any potential harm to the environment. Although their usage in residential places and building sectors [...] Read more.

Photovoltaic (PV) systems have become one of the most promising alternative energy sources, as they transform the sun’s energy into electricity. This can frequently be achieved without causing any potential harm to the environment. Although their usage in residential places and building sectors has notably increased, PV systems are regarded as unpredictable, changeable, and irregular power sources. This is because, in line with the system’s geographic region, the power output depends to a certain extent on the atmospheric environment, which can vary drastically. Therefore, artificial intelligence (AI)-based approaches are extensively employed to examine the effects of climate change on solar power. Then, the most optimal AI algorithm is used to predict the generated power. In this study, we used machine learning (ML)-based algorithms to predict the generated power of a PV system for residential buildings. Using a PV system, Pyranometers, and weather station data amassed from a station at King Khalid University, Abha (Saudi Arabia) with a residential setting, we conducted several experiments to evaluate the predictability of various well-known ML algorithms from the generated power. A backward feature-elimination technique was applied to find the most relevant set of features. Among all the ML prediction models used in the work, the deep-learning-based model provided the minimum errors with the minimum set of features (approximately seven features). When the feature set is greater than ten features, the polynomial regression model shows the best prediction, with minimal errors. Comparing all the prediction models, the highest errors were associated with the linear regression model. In general, it was observed that with a small number of features, the prediction models could minimize the generated power prediction’s mean squared error value to approximately 0.15. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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41 pages, 445 KiB  

Open AccessReview

Basic Principles, Most Common Computational Tools, and Capabilities for Building Energy and Urban Microclimate Simulations

by George M. Stavrakakis, Dimitris Al. Katsaprakakis and Markos Damasiotis

Energies 2021, 14(20), 6707; https://doi.org/10.3390/en14206707 - 15 Oct 2021

Cited by 19 | Viewed by 2859

Abstract

This paper presents basic principles of built-environment physics’ modelling, and it reviews common computational tools and capabilities in a scope of practical design approaches for retrofitting purposes. Well-established simulation models and methods, with applications found mainly in the international scientific literature, are described [...] Read more.

This paper presents basic principles of built-environment physics’ modelling, and it reviews common computational tools and capabilities in a scope of practical design approaches for retrofitting purposes. Well-established simulation models and methods, with applications found mainly in the international scientific literature, are described by means of strengths and weaknesses as regards related tools’ availability, easiness to use, and reliability towards the determination of the optimal blends of retrofit measures for building energy upgrading and Urban Heat Island (UHI) mitigation. The various characteristics of computational approaches are listed and collated by means of comparison among the principal modelling methods as well as among the respective computational tools that may be used for simulation and decision-making purposes. Insights of coupling between building energy and urban microclimate models are also presented. The main goal was to provide a comprehensive overview of available simulation methods that can be used at the early design stages for planning retrofitting strategies and guiding engineers and technical professionals through the simulation tools’ options oriented to the considered case study. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

19 pages, 9326 KiB  

Open AccessArticle

Study on the Efficiency and Dynamic Characteristics of an Energy Harvester Based on Flexible Structure Galloping

by Peng Liao, Jiyang Fu, Wenyong Ma, Yuan Cai and Yuncheng He

Energies 2021, 14(20), 6548; https://doi.org/10.3390/en14206548 - 12 Oct 2021

Cited by 5 | Viewed by 1867

Abstract

According to the engineering phenomenon of the galloping of ice-coated transmission lines at certain wind speeds, this paper proposes a novel type of energy harvester based on the galloping of a flexible structure. It uses the tension generated by the galloping structure to [...] Read more.

According to the engineering phenomenon of the galloping of ice-coated transmission lines at certain wind speeds, this paper proposes a novel type of energy harvester based on the galloping of a flexible structure. It uses the tension generated by the galloping structure to cause periodic strain on the piezoelectric cantilever beam, which is highly efficient for converting wind energy into electricity. On this basis, a physical model of fluid–structure interaction is established, and the Reynolds-averaged Navier–Stokes equation and SST K -ω turbulent model based on ANSYS Fluent are used to carry out a two-dimensional steady computational fluid dynamics (CFD) numerical simulation. First, the CFD technology under different grid densities and time steps is verified. CFD numerical simulation technology is used to simulate the physical model of the energy harvester, and the effect of wind speed on the lateral displacement and aerodynamic force of the flexible structure is analyzed. In addition, this paper also carries out a parameterized study on the influence of the harvester’s behavior, through the wind tunnel test, focusing on the voltage and electric power output efficiency. The harvester has a maximum output power of 119.7 μW/mm³ at the optimal resistance value of 200 KΩ at a wind speed of 10 m/s. The research results provide certain guidance for the design of a high-efficiency harvester with a square aerodynamic shape and a flexible bluff body. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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23 pages, 7415 KiB  

Open AccessArticle

Airtightness and Heat Energy Loss of Mid-Size Terraced Houses Built of Different Construction Materials

by Valdas Paukštys, Gintaris Cinelis, Jūratė Mockienė and Mindaugas Daukšys

Energies 2021, 14(19), 6367; https://doi.org/10.3390/en14196367 - 05 Oct 2021

Cited by 7 | Viewed by 1847

Abstract

The European Union has adopted legislation aimed to increase the use of renewable energy and improve the effectiveness of conventional-form energy use. Additional structure insulation helps to decrease heat energy loss. Airtightness of the building envelope (building airtightness) is an additional factor that [...] Read more.

The European Union has adopted legislation aimed to increase the use of renewable energy and improve the effectiveness of conventional-form energy use. Additional structure insulation helps to decrease heat energy loss. Airtightness of the building envelope (building airtightness) is an additional factor that determines comfortable and energy-saving living environment. The conformity of heat energy loss with the object’s design energy class is one of the mandatory indicators used in the obligatory building energy performance certification procedure. Optionally, the objects to be certified are the entire buildings or separate units (flats). There is an issue of concern whether a flat assessed as a separate housing unit would meet the requirements of design energy class depending on the location of the unit in the building. The study is aimed to determine the change in heat loss of end units in terraced houses (townhouses) as a result of various factors, leading to uneven airtightness of the building envelope. The non-destructive assessment of building airtightness was implemented through the combined use of methods, namely Blower Door Test (around 200 measurements) and Infrared Thermography. The hollow clay unit masonry showed ca. 7–11% less airtightness than the sand–lime block masonry structure. The end units were up to 20% less airtight compared to the inside units. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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14 pages, 5316 KiB  

Open AccessArticle

Numerical Simulation of Leakage and Diffusion Process of LNG Storage Tanks

by Xue Li, Ning Zhou, Bing Chen, Qian Zhang, Vamegh Rasouli, Xuanya Liu, Weiqiu Huang and Lingchen Kong

Energies 2021, 14(19), 6282; https://doi.org/10.3390/en14196282 - 02 Oct 2021

Cited by 7 | Viewed by 2306

Abstract

To investigate the evolution process of LNG (Liquefied Natural Gas) liquid pool and gas cloud diffusion, the Realizable k-ε model and Eluerian model were used to numerically simulate the liquid phase leakage and diffusion process of LNG storage tanks. The experimental [...] Read more.

To investigate the evolution process of LNG (Liquefied Natural Gas) liquid pool and gas cloud diffusion, the Realizable k-ε model and Eluerian model were used to numerically simulate the liquid phase leakage and diffusion process of LNG storage tanks. The experimental results showed that some LNG flashed and vaporized rapidly to form a combustible cloud during the continuous leakage. The diffusion of the explosive cloud was divided into heavy gas accumulation, entrainment heat transfer, and light gas drift. The vapor cloud gradually separated into two parts from the whole “fan leaf shape”. One part was a heavy gas cloud; the other part was a light gas cloud that spread with the wind in the downwind direction. The change of leakage aperture had a greater impact on the whole spill and dispersion process of the storage tank. The increasing leakage aperture would lead to 10.3 times increase in liquid pool area, 78.5% increase in downwind dispersion of methane concentration at 0.5 LFL, 22.6% increase in crosswind dispersion of methane concentration at 0.5 LFL, and 249% increase in flammable vapor cloud volume. Within the variation range of the leakage aperture, the trend of the gas cloud diffusion remained consistent, but the time for the liquid pool to keep stable and the gas cloud to enter the next diffusion stage was delayed. The low-pressure cavity area within 200 m of the leeward surface of the storage tank would accumulate heavy gas for a long time, forming a local high concentration area, which should be an area of focus for alert prediction. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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28 pages, 3609 KiB  

Open AccessArticle

Development of a Low-Cost Data Acquisition System for Very Short-Term Photovoltaic Power Forecasting

by Guilherme Fonseca Bassous, Rodrigo Flora Calili and Carlos Hall Barbosa

Energies 2021, 14(19), 6075; https://doi.org/10.3390/en14196075 - 24 Sep 2021

Cited by 3 | Viewed by 1546

Abstract

The rising adoption of renewable energy sources means we must turn our eyes to limitations in traditional energy systems. Intermittency, if left unaddressed, may lead to several power-quality and energy-efficiency issues. The objective of this work is to develop a working tool to [...] Read more.

The rising adoption of renewable energy sources means we must turn our eyes to limitations in traditional energy systems. Intermittency, if left unaddressed, may lead to several power-quality and energy-efficiency issues. The objective of this work is to develop a working tool to support photovoltaic energy forecast models for real-time operation applications. The current paradigm of intra-hour solar-power forecasting is to use image-based approaches to predict the state of cloud composition for short time horizons. Since the objective of intra-minute forecasting is to address high-frequency intermittency, data must provide information on and surrounding these events. For that purpose, acquisition by exception was chosen as the guiding principle. The system performs power measurements at 1 Hz frequency, and whenever it detects variations over a certain threshold, it saves the data 10 s before and 4 s after the detection point. A multilayer perceptron neural network was used to determine its relevance to the forecasting problem. With a thorough selection of attributes and network structures, the results show very low error with R² greater than 0.93 for both input variables tested with a time horizon of 60 s. In conclusion, the data provided by the acquisition system yielded relevant information for forecasts up to 60 s ahead. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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22 pages, 4920 KiB  

Open AccessArticle

Applicability of Different Double-Layer Models for the Performance Assessment of the Capacitive Energy Extraction Based on Double Layer Expansion (CDLE) Technique

by Zhi Zou, Longcheng Liu, Shuo Meng, Xiaolei Bian and Yongmei Li

Energies 2021, 14(18), 5828; https://doi.org/10.3390/en14185828 - 15 Sep 2021

Cited by 5 | Viewed by 1480

Abstract

Capacitive energy extraction based on double layer expansion (CDLE) is a renewable method of harvesting energy from the salinity difference between seawater and freshwater. It is based on the change in properties of the electric double layer (EDL) formed at the electrode surface [...] Read more.

Capacitive energy extraction based on double layer expansion (CDLE) is a renewable method of harvesting energy from the salinity difference between seawater and freshwater. It is based on the change in properties of the electric double layer (EDL) formed at the electrode surface when the concentration of the solution is changed. Many theoretical models have been developed to describe the structural and thermodynamic properties of the EDL at equilibrium, e.g., the Gouy–Chapman–Stern (GCS), Modified Poisson–Boltzmann–Stern (MPBS), modified Donnan (mD) and improved modified Donnan (i-mD) models. To evaluate the applicability of these models, especially the rationality and the physical interpretation of the parameters that were used in these models, a series of single-pass and full-cycle experiments were performed. The experimental results were compared with the numerical simulations of different EDL models. The analysis suggested that, with optimized parameters, all the EDL models we examined can well explain the equilibrium charge–voltage relation of the single-pass experiment. The GCS and MPBS models involve, however, the use of physically unreasonable parameter values. By comparison, the i-mD model is the most recommended one because of its accuracy in the results and the meaning of the parameters. Nonetheless, the i-mD model alone failed to simulate the energy production of the full-cycle CDLE experiments. Future research regarding the i-mD model is required to understand the process of the CDLE technique better. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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22 pages, 9901 KiB  

Open AccessArticle

Analysis of Hybrid Hetero-Homo Junction Lead-Free Perovskite Solar Cells by SCAPS Simulator

by Marwa. S. Salem, Ahmed Shaker, Abdelhalim Zekry, Mohamed Abouelatta, Adwan Alanazi, Mohammad T. Alshammari and Christian Gontand

Energies 2021, 14(18), 5741; https://doi.org/10.3390/en14185741 - 12 Sep 2021

Cited by 35 | Viewed by 2850

Abstract

In this work, we report on the effect of substituting the active intrinsic i-layer on a conventional pin structure of lead-free perovskite solar cell (PSC) by a homo p-n junction, keeping the thickness of the active layer constant. It is expected that when [...] Read more.

In this work, we report on the effect of substituting the active intrinsic i-layer on a conventional pin structure of lead-free perovskite solar cell (PSC) by a homo p-n junction, keeping the thickness of the active layer constant. It is expected that when the active i-layer is substituted by a p-n homo junction, one can increase the collection efficiency of the photo-generated electrons and holes due to the built-in electric field of the homo junction. The impact of the technological and physical device parameters on the performance parameters of the solar cell have been worked out. It was found that p-side thickness must be wider than the n-side, while its acceptor concentration should be slightly lower than the donor concentration of the n-side to achieve maximum efficiency. In addition, different absorber types, namely, i-absorber, n-absorber and p-absorber, are compared to the proposed pn-absorber, showing a performance-boosting effect when using the latter. Moreover, the proposed structure is made without a hole transport layer (HTL) to avoid the organic issues of the HTL materials. The back metal work function, bulk trap density and ETL material are optimized for best performance of the HTL-free structure, giving J_sc = 26.48, V_oc = 0.948 V, FF = 77.20 and PCE = 19.37% for AM1.5 solar spectra. Such results highlight the prospective of the proposed structure and emphasize the importance of using HTL-free solar cells without deteriorating the efficiency. The solar cell is investigated by using SCAPS simulator. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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21 pages, 13357 KiB  

Open AccessArticle

An Accurate and Efficient Fitness-For-Service Assessment Method of Pipes with Defects under Surface Load

by Jianping Liu, Hong Zhang, Baodong Wang, Dong Zhang, Beilei Ji, Fan Fei and Xiaoben Liu

Energies 2021, 14(17), 5521; https://doi.org/10.3390/en14175521 - 03 Sep 2021

Cited by 1 | Viewed by 1666

Abstract

With continued urbanization in China, the construction of urban gas pipelines is increasing, and the safety of gas pipelines are also increasingly affected by urban development and the increased scope of buildings and roads. Pipes with defects are more likely to fail under [...] Read more.

With continued urbanization in China, the construction of urban gas pipelines is increasing, and the safety of gas pipelines are also increasingly affected by urban development and the increased scope of buildings and roads. Pipes with defects are more likely to fail under the surface loads. In this study, uniaxial tensile tests of high-density polyethylene (HDPE) pipes were carried out to obtain the real material parameters of pipe. A pipeline-soil interaction finite element model of HDPE pipeline with defects under surface load was established. The failure mechanism of the urban gas pipeline was studied and the influence of parameters such as internal pressure, defect position, defect depth on the mechanical behavior, and failure of pipelines were analyzed. A failure criterion for HDPE pipes with defects under surface load was proposed based on the limit-state curves obtained under different working conditions. Furthermore, an accurate and efficient fitness-for-service assessment procedure of pipes with defects under surface load was proposed. The results showed that maximum Mises stress of the pipeline gradually increased with increasing surface load and the position of maximum stress changed from the top and bottom of the pipe to the defect position and both sides of the pipe. Finally, when Mises stress of the HDPE pipe exceeds the yield limit, failure will occur. Internal pressure, defect location, and defect depth were found to influence the failure process and critical surface load of the pipeline. Safety evaluation curves of the gas pipeline with defects under surface load were obtained by calculating the critical failure load of the pipeline under various working conditions. Finally, a nonlinear fitting method was used to derive a formula for calculating the critical surface load under different defect parameters. The proposed method provides a useful reference for urban gas pipeline safety management. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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41 pages, 7665 KiB  

Open AccessArticle

Healthy and Faulty Experimental Performance of a Typical HVAC System under Italian Climatic Conditions: Artificial Neural Network-Based Model and Fault Impact Assessment

by Antonio Rosato, Francesco Guarino, Sergio Sibilio, Evgueniy Entchev, Massimiliano Masullo and Luigi Maffei

Energies 2021, 14(17), 5362; https://doi.org/10.3390/en14175362 - 28 Aug 2021

Cited by 12 | Viewed by 2066

Abstract

The heating, ventilation, and air conditioning (HVAC) system serving the test room of the SENS i-Lab of the Department of Architecture and Industrial Design of the University of Campania Luigi Vanvitelli (Aversa, south of Italy) has been experimentally investigated through a series of [...] Read more.

The heating, ventilation, and air conditioning (HVAC) system serving the test room of the SENS i-Lab of the Department of Architecture and Industrial Design of the University of Campania Luigi Vanvitelli (Aversa, south of Italy) has been experimentally investigated through a series of tests performed during both summer and winter under both normal and faulty scenarios. In particular, five distinct typical faults have been artificially implemented in the HVAC system and analyzed during transient and steady-state operation. An optimal artificial neural network-based system model has been created in the MATLAB platform and verified by contrasting the experimental data with the predictions of twenty-two different neural network architectures. The selected artificial neural network architecture has been coupled with a dynamic simulation model developed by using the TRaNsient SYStems (TRNSYS) software platform with the main aims of (i) making available an experimental dataset characterized by labeled normal and faulty data covering a wide range of operating and climatic conditions; (ii) providing an accurate simulation tool able to generate operation data for assisting further research in fault detection and diagnosis of HVAC units; and (iii) evaluating the impact of selected faults on occupant indoor thermo-hygrometric comfort, temporal trends of key operating system parameters, and electric energy consumptions. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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18 pages, 21752 KiB  

Open AccessArticle

Modeling Pollutant Emissions: Influence of Two Heat and Power Plants on Urban Air Quality

by Robert Cichowicz and Maciej Dobrzański

Energies 2021, 14(17), 5218; https://doi.org/10.3390/en14175218 - 24 Aug 2021

Cited by 9 | Viewed by 1889

Abstract

Large industrial plants, power plants, and combined heat and power plants are popularly believed to be the main sources of point emissions, affecting both local and global air quality. This is because these installations emit significant amounts of pollutants at high altitudes every [...] Read more.

Large industrial plants, power plants, and combined heat and power plants are popularly believed to be the main sources of point emissions, affecting both local and global air quality. This is because these installations emit significant amounts of pollutants at high altitudes every year. In this study, we investigate the impact of two solid fuel (hard coal)-fired CHP plants located within the urban agglomeration on the air quality of the city of Lodz in Poland (Europe). We used an OPA03 computer software to model the spatial distribution of pollutants. The results show that the annual average concentrations of pollutants were highest at an altitude of 25 m above ground level and decreased at lower measurement heights. The concentrations did not exceed permissible levels, reaching only 4% of national and international regulatory limits. We also made field measurements during the winter heating period, using an unmanned aerial vehicle (UAV) equipped with sensors to map the distributions of dust and gas pollutants in the areas with the highest concentrations of emissions from the two heat and power plants. Overall, the field measurements confirmed that it is not high-altitude emissions that have the greatest impact on local air quality. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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24 pages, 1234 KiB  

Open AccessArticle

The Implementation of Multiple Linear Regression for Swimming Pool Facilities: Case Study at Jøa, Norway

by Ole Øiene Smedegård, Thomas Jonsson, Bjørn Aas, Jørn Stene, Laurent Georges and Salvatore Carlucci

Energies 2021, 14(16), 4825; https://doi.org/10.3390/en14164825 - 07 Aug 2021

Cited by 2 | Viewed by 3011

Abstract

This paper presents a statistical model for predicting the time-averaged total power consumption of an indoor swimming facility. The model can be a powerful tool for continuous supervision of the facility’s energy performance that can quickly disclose possible operational disruptions/irregularities and thus minimize [...] Read more.

This paper presents a statistical model for predicting the time-averaged total power consumption of an indoor swimming facility. The model can be a powerful tool for continuous supervision of the facility’s energy performance that can quickly disclose possible operational disruptions/irregularities and thus minimize annual energy use. Multiple linear regression analysis is used to analyze data collected in a swimming facility in Norway. The resolution of the original training dataset was in 1 min time steps and during the investigation was transposed both by time-averaging the data, and by treating part of the dataset exclusively. The statistically significant independent variables were found to be the outdoor dry-bulb temperature and the relative pool usage factor. The model accurately predicted the power consumption in the validation process, and also succeeded in disclosing all the critical operational disruptions in the validation dataset correctly. The model can therefore be applied as a dynamic energy benchmark for fault detection in swimming facilities. The final energy prediction model is relatively simple and can be deployed either in a spreadsheet or in the building automation reporting system, thus the method can contribute instantly to keep the operation of any swimming facility within the optimal individual energy performance range. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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20 pages, 1597 KiB  

Open AccessArticle

Numerical Analysis on the Performance of a Radiant Cooling Panel with Serpentine-Based Design

by Mohammad Hakim Mohd Radzai, Chong Tak Yaw, Chin Wai Lim, Siaw Paw Koh and Nur Amirani Ahmad

Energies 2021, 14(16), 4744; https://doi.org/10.3390/en14164744 - 04 Aug 2021

Cited by 10 | Viewed by 2895

Abstract

Radiant cooling systems (RCS) are gaining acceptance as a heating, ventilation, and air conditioning (HVAC) solution for achieving adequate thermal comfort and maintaining acceptable indoor air quality inside buildings. RCS are well known for their energy-saving potential; however, serious condensation problem hinders the [...] Read more.

Radiant cooling systems (RCS) are gaining acceptance as a heating, ventilation, and air conditioning (HVAC) solution for achieving adequate thermal comfort and maintaining acceptable indoor air quality inside buildings. RCS are well known for their energy-saving potential; however, serious condensation problem hinders the growth of this technology. In order to prevent the risk of condensation, the supply water temperature is kept higher than the dew point temperature of the air inside the room. The full potential of the cooling power of a radiant cooling panel is limited. Therefore, this article is on maximizing the cooling capacity of a radiant cooling panel, in terms of flow configuration. Radiant cooling panels (RCP) with different chilled water pipe configurations are designed and compared, side by side with the conventional serpentine flow configuration. The cooling performance of the radiant cooling panels is evaluated by using computational fluid dynamics (CFD) with Ansys Fluent software (Ansys 2020 R2, PA, USA). Under similar flow and operating conditions, the common serpentine flow configuration exhibits the least effective cooling performance, with the highest pressure drop across the pipe. It is concluded that the proposed designs have the potential of improving the overall efficiency of RCP in terms of temperature distribution, cooling capacity, and pressure drop. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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18 pages, 5572 KiB  

Open AccessArticle

A New Measurement of Anisotropic Relative Permeability and Its Application in Numerical Simulation

by Congcong Li, Shuoliang Wang, Qing You and Chunlei Yu

Energies 2021, 14(16), 4731; https://doi.org/10.3390/en14164731 - 04 Aug 2021

Cited by 8 | Viewed by 1520

Abstract

In this paper, we used a self-developed anisotropic cubic core holder to test anisotropic relative permeability by the unsteady-states method, and introduced the anisotropic relative permeability to the traditional numerical simulator. The oil–water two-phase governing equation considering the anisotropic relative permeability is established, [...] Read more.

In this paper, we used a self-developed anisotropic cubic core holder to test anisotropic relative permeability by the unsteady-states method, and introduced the anisotropic relative permeability to the traditional numerical simulator. The oil–water two-phase governing equation considering the anisotropic relative permeability is established, and the difference discretization is carried out. We formed a new oil–water two-phase numerical simulation method. It is clear that in a heterogeneous rock with millimeter to centimeter scale laminae, relative permeability is an anisotropic tensor. When the displacement direction is parallel to the bedding, the residual oil saturation is high and the displacement efficiency is low. The greater the angle between the displacement direction and the bedding strike, the lower the residual oil saturation is, the higher the displacement efficiency is, and the relative permeability curve tends towards a rightward shift. The new simulator showed that the anisotropic relative permeability not only affects the breakthrough time and sweep range of water flooding, but also has a significant influence on the overall water cut. The new simulator is validated with the actual oilfield model. It could describe the law of oil–water seepage in an anisotropic reservoir, depict the law of remaining oil distribution of a typical fluvial reservoir, and provide technical support for reasonable injection-production directions. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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18 pages, 4183 KiB  

Open AccessArticle

Energy and Exergy Efficiency Analysis of Fluid Flow and Heat Transfer in Sinter Vertical Cooler

by Zude Cheng, Haitao Wang, Junsheng Feng, Yongfang Xia and Hui Dong

Energies 2021, 14(15), 4522; https://doi.org/10.3390/en14154522 - 27 Jul 2021

Cited by 3 | Viewed by 1499

Abstract

In order to fully understand the energy and exergy transfer processes in sinter vertical coolers, a simulation model of the fluid flow and heat transfer in a vertical cooler was established, and energy and exergy efficiency analyses of the gas–solid heat transfer in [...] Read more.

In order to fully understand the energy and exergy transfer processes in sinter vertical coolers, a simulation model of the fluid flow and heat transfer in a vertical cooler was established, and energy and exergy efficiency analyses of the gas–solid heat transfer in a vertical cooler were conducted in detail. Based on the calculation method of the whole working condition, the suitable operational parameters of the vertical cooler were obtained by setting the net exergy efficiency in the vertical cooler as the indicator function. The results show that both the quantity of sinter waste heat recovery (SWHR) and energy efficiency increased as the air flow rate (AFR) increased, and they decreased as the air inlet temperature (AIT) increased. The increase in the sinter inlet temperature (SIT) resulted in an increase in the quantity of SWHR and a decrease in energy efficiency. The air net exergy had the maximum value as the AFR increased, and it only increased monotonically as the SIT and AIT increased. The net exergy efficiency reached the maximum value as the AFR and AIT increased, and the increase in the SIT only resulted in a decrease in the net exergy efficiency. When the sinter annual production of a 360 m² sintering machine was taken as the processing capacity of the vertical cooler, the suitable operational parameters of the vertical cooler were 190 kg/s for the AFR, and 353 K for the AIT. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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14 pages, 4008 KiB  

Open AccessArticle

Numerical Analysis on the Flue Gas Temperature Maintenance System of a Solid Fuel-Fired Boiler Operating at Minimum Loads

by Michalina Kurkus-Gruszecka, Piotr Krawczyk and Janusz Lewandowski

Energies 2021, 14(15), 4420; https://doi.org/10.3390/en14154420 - 22 Jul 2021

Viewed by 2199

Abstract

Currently, energy policy is associated with the increase in the share of renewable sources in systemic energy production. Due to this trend, coal-fired power units must increase their work flexibility. Adapting a coal power plant to work with a lower load often causes [...] Read more.

Currently, energy policy is associated with the increase in the share of renewable sources in systemic energy production. Due to this trend, coal-fired power units must increase their work flexibility. Adapting a coal power plant to work with a lower load often causes the issue of maintaining the temperature before the selective catalytic reduction (SCR) installation at a sufficiently high level. This paper presents a CFD analysis of the mixing area of two flue gas streams before the SCR installation with various methods for mixing flue gas streams. The novelty of the work is mixing the flue gas streams of different temperatures using a flap shape developed by the authors. A series of numerical simulations were performed to develop the location and method of introducing the higher temperature gas, obtaining a uniform distribution of the exhaust gas temperature. The simulation scheme was applied to a series of geometrical modifications of the boundary conditions. The tested solution using only a single, straight flap in the flue gas duct allows the amplitude to be reduced from 298 K to 144 K. As a result of the research, a mixing flap design was developed to reduce the initial temperature amplitude of the flue gas streams from 298 K to 43 K. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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17 pages, 592 KiB  

Open AccessArticle

Ensemble Surrogate Models for Fast LIB Performance Predictions

by Marco Quartulli, Amaia Gil, Ane Miren Florez-Tapia, Pablo Cereijo, Elixabete Ayerbe and Igor G. Olaizola

Energies 2021, 14(14), 4115; https://doi.org/10.3390/en14144115 - 08 Jul 2021

Cited by 8 | Viewed by 2391

Abstract

Battery Cell design and control have been widely explored through modeling and simulation. On the one hand, Doyle’s pseudo-two-dimensional (P2D) model and Single Particle Models are among the most popular electrochemical models capable of predicting battery performance and therefore guiding cell characterization. On [...] Read more.

Battery Cell design and control have been widely explored through modeling and simulation. On the one hand, Doyle’s pseudo-two-dimensional (P2D) model and Single Particle Models are among the most popular electrochemical models capable of predicting battery performance and therefore guiding cell characterization. On the other hand, empirical models obtained, for example, by Machine Learning (ML) methods represent a simpler and computationally more efficient complement to electrochemical models and have been widely used for Battery Management System (BMS) control purposes. This article proposes ML-based ensemble models to be used for the estimation of the performance of an LIB cell across a wide range of input material characteristics and parameters and evaluates 1. Deep Learning ensembles for simulation convergence classification and 2. structured regressors for battery energy and power predictions. The results represent an improvement on state-of-the-art LIB surrogate models and indicate that deep ensembles represent a promising direction for battery modeling and design. Full article

(This article belongs to the Topic Numerical Methods and Computer Simulations in Energy Analysis)

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