Energies

Article

25 pages, 15946 KiB

Open AccessEditor’s ChoiceArticle

Energy Efficiency and Stability of Micro-Hydropower PAT-SEIG Systems for DC Off-Grids

by João M. R. Catelas, João F. P. Fernandes, Modesto Pérez-Sánchez, P. Amparo López-Jiménez, Helena M. Ramos and P. J. Costa Branco

Energies 2024, 17(6), 1382; https://doi.org/10.3390/en17061382 - 13 Mar 2024

Viewed by 1132

Abstract

Using pumps operating as turbines (PATs) offers the possibility of increasing the sustainability of water and energy systems by recovering the excess energy that would be otherwise lost in pressure-reducing valves or head loss chambers. Regarding on-grid applications, there have been many research [...] Read more.

Using pumps operating as turbines (PATs) offers the possibility of increasing the sustainability of water and energy systems by recovering the excess energy that would be otherwise lost in pressure-reducing valves or head loss chambers. Regarding on-grid applications, there have been many research works, and PATs have been implemented in several ways. However, more research still needs to be done on optimizing the efficiency and stability of PATs operating in off-grid systems. This work contributes to the development of stable direct current (DC) off-grid electric systems based on PATs using a self-excited induction generator (SEIG). In this context, a methodology is proposed, based on the hydraulic, mechanical, and electric subsystems, to define the PAT-SEIG operational area to maximize energy conversion and system efficiency. These limits depend highly on the capacitor value, rotational speed, and electric load. In addition, an analytical model is proposed to estimate the PAT-SEIG operation under specific conditions. With this, water managers can design and optimize an off-grid PAT-SEIG system and define the best hydraulic machines, electronic equipment, and control elements to maximize energy conversion within the target of operational limits. Two micro PAT-SEIG setups were implemented in the hydraulic laboratory of IST/CERIS under typical operating conditions to validate the proposed methodology. The system’s maximum efficiency and operational limits can be adapted using different capacitor values for the excitation of the SEIG. Considering the nominal efficiencies of the system’s components, the maximum p.u. efficiency obtained for each PAT-SEIG system was between 0.7 and 0.8 p.u. Full article

(This article belongs to the Section A: Sustainable Energy)

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35 pages, 1956 KiB

Open AccessEditor’s ChoiceArticle

Predictive Energy Management of a Building-Integrated Microgrid: A Case Study

by Romain Mannini, Tejaswinee Darure, Julien Eynard and Stéphane Grieu

Energies 2024, 17(6), 1355; https://doi.org/10.3390/en17061355 - 12 Mar 2024

Cited by 3 | Viewed by 1964

Abstract

The efficient integration of distributed energy resources (DERs) in buildings is a challenge that can be addressed through the deployment of multienergy microgrids (MGs). In this context, the Interreg SUDOE project IMPROVEMENT was launched at the end of the year 2019 with the [...] Read more.

The efficient integration of distributed energy resources (DERs) in buildings is a challenge that can be addressed through the deployment of multienergy microgrids (MGs). In this context, the Interreg SUDOE project IMPROVEMENT was launched at the end of the year 2019 with the aim of developing efficient solutions allowing public buildings with critical loads to be turned into net-zero-energy buildings (nZEBs). The work presented in this paper deals with the development of a predictive energy management system (PEMS) for the management of thermal resources and users’ thermal comfort in public buildings. Optimization-based/optimization-free model predictive control (MPC) algorithms are presented and validated in simulations using data collected in a public building equipped with a multienergy MG. Models of the thermal MG components were developed. The strategy currently used in the building relies on proportional–integral–derivative (PID) and rule-based (RB) controllers. The interconnection between the thermal part and the electrical part of the building-integrated MG is managed by taking advantage of the solar photovoltaic (PV) power generation surplus. The optimization-based MPC EMS has the best performance but is rather computationally expensive. The optimization-free MPC EMS is slightly less efficient but has a significantly reduced computational cost, making it the best solution for in situ implementation. Full article

(This article belongs to the Special Issue Advanced Control, Operation and Energy Management of Distribution Networks and Smart Grids)

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29 pages, 29232 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Current Compensation Method in a Distribution System Based on a Four-Leg Inverter under Unbalanced Load Conditions Using an Artificial Neural Network

by Tae-Gyu Kim, Chang-Gyun An, Junsin Yi and Chung-Yuen Won

Energies 2024, 17(6), 1325; https://doi.org/10.3390/en17061325 - 10 Mar 2024

Viewed by 679

Abstract

This study proposes an unbalanced current compensation method based on a four-leg inverter using an artificial neural network (ANN) under unbalanced load conditions. Distribution systems exhibit rapid load variations, and conventional filter-based control methods suffer from the drawback of requiring an extended time [...] Read more.

This study proposes an unbalanced current compensation method based on a four-leg inverter using an artificial neural network (ANN) under unbalanced load conditions. Distribution systems exhibit rapid load variations, and conventional filter-based control methods suffer from the drawback of requiring an extended time period to reach a steady state. To address this problem, an ANN is applied to calculate the unbalanced current reference and enhance dynamic performance. Additionally, because of the periodic incorrect output inherent in the ANN, applying it to a proportional–integral controller would result in an error being directly reflected in the current reference. In the aforementioned problem, an ANN is applied to the dq0 coordinate system current controller to compensate for the periodic incorrect output in the current reference calculation. The proposed ANN-based unbalanced current compensation method is validated through PSIM simulations and experiments. Full article

(This article belongs to the Special Issue Advanced Control, Optimization, Stability and Reliability of Microgrids and Power Systems)

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18 pages, 11942 KiB

Open AccessEditor’s ChoiceArticle

Investigating the Effect of Gear Ratio in the Case of Joint Multi-Objective Optimization of Electric Motor and Gearbox

by György Istenes and József Polák

Energies 2024, 17(5), 1203; https://doi.org/10.3390/en17051203 - 3 Mar 2024

Cited by 4 | Viewed by 1293

Abstract

In this paper, a software framework is presented through an application that is able to jointly optimize an electric motor and a gearbox for the design of a drive system for electric vehicles. The framework employs a global optimization method and uses both [...] Read more.

In this paper, a software framework is presented through an application that is able to jointly optimize an electric motor and a gearbox for the design of a drive system for electric vehicles. The framework employs a global optimization method and uses both analytical and finite element method (FEM) models to evaluate the objective functions. The optimization process is supported by a statistical surrogate model, which allows a large reduction of runtime. An earlier version of this framework was only suitable for electric motor optimization. In the application presented in a previous paper, the motor of a belt-driven electric drive system was optimized. In this paper, the optimization of the same drive system is shown, but now with a combined optimization of a gear drive and motor. The objective functions of optimization are minimizing the total loss energy and the weight of the drive system. The optimization results are compared with previous results to demonstrate the further potential of joint optimization. Full article

(This article belongs to the Special Issue Advanced Topologies and Control Strategies in Electric Machines and Drives)

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22 pages, 24583 KiB

Open AccessEditor’s ChoiceArticle

Insulation Resistance Degradation Models of Extruded Power Cables under Thermal Ageing

by Xufei Ge, Fulin Fan, Martin J. Given and Brian G. Stewart

Energies 2024, 17(5), 1062; https://doi.org/10.3390/en17051062 - 23 Feb 2024

Cited by 3 | Viewed by 929

Abstract

Insulation resistance (IR) is an essential metric indicating insulation conditions of extruded power cables. To deliver reliable IR simulation as a reference for practical cable inspection, in this paper, four IR degradation models for cross-linked polyethylene-insulated cables under thermal ageing are presented. In [...] Read more.

Insulation resistance (IR) is an essential metric indicating insulation conditions of extruded power cables. To deliver reliable IR simulation as a reference for practical cable inspection, in this paper, four IR degradation models for cross-linked polyethylene-insulated cables under thermal ageing are presented. In addition, the influences of methodologies and temperature profiles on IR simulation are evaluated. Cable cylindrical insulation is first divided into sufficiently small segments whose temperatures are simulated by jointly using a finite volume method and an artificial neural network to model the thermal ageing experiment conditions. The thermal degradation of IR is then simulated by dichotomy models that randomly sample fully degraded segments based on an overall insulation (layer) ageing condition estimation and discretization models that estimate the gradual degradation of individual segments, respectively. Furthermore, uniform and non-uniform temperature profiles are incorporated into dichotomy and discretization models, respectively, for a comparison. The IR simulation results are not only compared between different models, but also discussed around the sensitivity of IR simulation to segment sizes and degradation rates. This provides cable assessment engineers with insights into model behaviour as a reference for their selection of appropriate IR degradation models. Full article

(This article belongs to the Special Issue Dielectric Insulation in Medium- and High-Voltage Power Equipment—Degradation and Failure Mechanism, Diagnostics, and Electrical Parameters Improvement)

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0 pages, 4409 KiB

Open AccessEditor’s ChoiceArticle

Assessing Geothermal Energy Production Potential of Cambrian Geothermal Complexes in Lithuania

by Pijus Makauskas, Ieva Kaminskaite-Baranauskiene, Abdul Rashid Abdul Nabi Memon and Mayur Pal

Energies 2024, 17(5), 1054; https://doi.org/10.3390/en17051054 - 23 Feb 2024

Cited by 1 | Viewed by 958

Abstract

Lithuania has a geothermal anomaly situated in the southwestern region of the country. This anomaly is comprised of two primary geothermal complexes located in western Lithuania. The first complex is characterized by the Pärnu–Kemeri Devonian sandstone aquifers, which exhibit exceptionally good flow properties. [...] Read more.

Lithuania has a geothermal anomaly situated in the southwestern region of the country. This anomaly is comprised of two primary geothermal complexes located in western Lithuania. The first complex is characterized by the Pärnu–Kemeri Devonian sandstone aquifers, which exhibit exceptionally good flow properties. However, the reservoir temperatures in this complex only reach up to 45 °C. The second complex encompasses Cambrian sandstone reservoirs. Although these Cambrian sandstone reservoirs exhibit high temperatures, with the highest reservoir temperatures reaching up to 96 °C, these Cambrian sandstone reservoirs have less favorable petrophysical properties. This study focuses on the high temperature Cambrian Geothermal sandstone reservoirs. The study aims to conduct a geological screening of the existing and depleted hydrocarbon reservoirs with high water production rates. After initial data gathering, numerical modeling is employed with the help of mechanistic box models to evaluate the geothermal potential of the selected sites for commercial development. Ultimately, the study identifies the top five screened sites, which could be developed further for techno-economical modelling. Full article

(This article belongs to the Collection Renewable Energy and Energy Storage Systems)

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12 pages, 1299 KiB

Open AccessEditor’s ChoiceArticle

An Analysis of Risks and Challenges to the Polish Power Industry in the Year 2024

by Stanisław Tokarski, Małgorzata Magdziarczyk and Adam Smoliński

Energies 2024, 17(5), 1044; https://doi.org/10.3390/en17051044 - 22 Feb 2024

Cited by 5 | Viewed by 1195

Abstract

The green transition is a challenge for the Polish economy and energy sector. In this paper, the expert method of analysis was applied and findings revealed that the challenges and prerequisites for an effective transformation of the power sector mainly include technical, technological [...] Read more.

The green transition is a challenge for the Polish economy and energy sector. In this paper, the expert method of analysis was applied and findings revealed that the challenges and prerequisites for an effective transformation of the power sector mainly include technical, technological and organizational issues of energy production and use. The provision of electricity at competitive prices and with a low carbon footprint, for individual consumers and industry, is a prerequisite for maintaining the well-being of the population and ensuring the competitiveness of domestically produced goods. The ambitious climate policy goals of the European Union require immediate action and call for radical changes in the Polish energy sector; in the coming years, it must drastically reduce the amount of energy produced from fossil fuels and replace it with so-called green energy from renewable sources. The main purpose of this article was to highlight the need to modify Poland’s energy policy until 2040 in order to make it more consistent with the ambitious climate goals of the European Union. This article also shows that Poland’s energy transition must include a shift from fossil fuels to renewables, while ensuring that energy security is stabilized by the current energy and generation resources. To this end, we discuss the issues of creating reserves in the national energy system for the entire period of Poland’s energy transition. Full article

(This article belongs to the Section F: Electrical Engineering)

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12 pages, 2992 KiB

Open AccessEditor’s ChoiceArticle

Thermal Evolution of NiFe-NO₃ LDH and Its Application in Energy Storage Systems

by Marco Fortunato, Andrea Pietro Reverberi, Bruno Fabiano and Anna Maria Cardinale

Energies 2024, 17(5), 1035; https://doi.org/10.3390/en17051035 - 22 Feb 2024

Cited by 1 | Viewed by 886

Abstract

In this work, the performances of nickel iron layered double hydroxides (LDH) with the nitrate anion at the interlayer (NiFe-NO₃) for the manufacture of anodes for lithium-ion batteries have been tested before and after its sintering at different temperatures. After synthesis, [...] Read more.

In this work, the performances of nickel iron layered double hydroxides (LDH) with the nitrate anion at the interlayer (NiFe-NO₃) for the manufacture of anodes for lithium-ion batteries have been tested before and after its sintering at different temperatures. After synthesis, the material was thermally analyzed in a range 30–1250 °C, showing a mass loss occurring in three different consecutive steps leading to a total mass decrease of ~30 mass%. Following thermogravimetric analysis (TGA), four samples were prepared by annealing at four different temperatures: one of the four did not undergo a thermal treatment (NiFe-0), while the remaining three were annealed at 250 °C, 360 °C, and 560 °C for 6 h (NiFe-250, NiFe-360, and NiFe-560). All materials where completely characterized via FE-SEM, PXRD, and FT-IR. The pristine LDH material showed some structural and compositional changes for growing temperatures, starting from the typical turbostratic hexagonal structure through a mixture of amorphous metal oxides and finally to the stoichiometric oxides FeNi₂O₄ and NiO. The as-obtained materials were mixed with carbon black (C65) and sodium alginate and tested as electrodes in Swagelok half cells in LP30 vs. metallic Li to perform CV and GCPL analysis. The electrochemical tests showed that the performances of NiFe-0, both in terms of stability and specific capacity, are not so different from the one of the NiFe-560, even if the Ni mass% in the former is lower than in the NiFe-560. This phenomenon could be explained by assuming a combined mechanism of reaction involving both intercalation and conversion. Full article

(This article belongs to the Collection Renewable Energy and Energy Storage Systems)

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28 pages, 11000 KiB

Open AccessEditor’s ChoiceArticle

Optimization of Grid Energy Balance Using Vehicle-to-Grid Network System

by Carlos Armenta-Déu and Laura Demas

Energies 2024, 17(5), 1008; https://doi.org/10.3390/en17051008 - 21 Feb 2024

Cited by 4 | Viewed by 1031

Abstract

This paper proposes a methodological way to compensate for the imbalance between energy generation and consumption using a battery block from electric vehicles as an energy reservoir through the well-known vehicle-to-grid system (V2G). This method is based on a simulation process developed by [...] Read more.

This paper proposes a methodological way to compensate for the imbalance between energy generation and consumption using a battery block from electric vehicles as an energy reservoir through the well-known vehicle-to-grid system (V2G). This method is based on a simulation process developed by the authors that takes into consideration the daily fluctuations in energy consumption as well as the power level generated by an energy source, either conventional, renewable, or hybrid. This study shows that for very large electric vehicle fleets, the system is rendered non-viable, since the remaining energy in the battery block that allows the electric vehicle to be usable during the daytime avoids having to compensate for the energy grid imbalance, only allowing it to cover a percentage of the energy imbalance, which the proposed methodology may optimize. The analysis of the proposed methodology also shows the viability of the system when being applied to a small fleet of electric vehicles, not only compensating for the energy imbalance but also preserving the required energy in the battery of the electric vehicle to make it run. This method allows for predicting the optimum size of an electric vehicle battery, which depends on the energy generation level, coverage factor of the energy imbalance, and size of the electric vehicle fleet. Full article

(This article belongs to the Section A1: Smart Grids and Microgrids)

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20 pages, 3913 KiB

Open AccessEditor’s ChoiceArticle

Modulation Techniques and Coordinated Voltage Vector Distribution: Effects on Efficiency in Dual-Inverter Topology-Based Electric Drives

by Jakub Kucera, Petr Zakopal, Filip Baum and Ondrej Lipcak

Energies 2024, 17(5), 986; https://doi.org/10.3390/en17050986 - 20 Feb 2024

Viewed by 1000

Abstract

The increasing popularity of electric drives employing an isolated dual-inverter (DI) topology is motivated by their superior DC-link voltage and power utilization, fault-tolerant operation, and potential for multilevel operation. These attributes are significant in battery-powered transportation, such as electric vehicles and aviation. Given [...] Read more.

The increasing popularity of electric drives employing an isolated dual-inverter (DI) topology is motivated by their superior DC-link voltage and power utilization, fault-tolerant operation, and potential for multilevel operation. These attributes are significant in battery-powered transportation, such as electric vehicles and aviation. Given the considerable freedom in modulation and control of the DI topology, this paper researches the impact of reference voltage vector distribution between the two individual inverters. The study also evaluates the influence of two well-established asynchronous modulation strategies—Space Vector PWM (SVPWM) and Depenbrock’s Discontinuous Modulation (DPWM1). Since simulation tools nowadays play a crucial role in power electronics design and concept verification, the results are based on extensive and detailed models in Matlab/Simulink. Employing the basic field-oriented control of a 12 kW induction motor with precisely parameterized SiC switching devices for accurate loss calculation, this research reveals the possibility of significant energy savings at multiple operating points. Notably, optimal efficiency is achieved when one inverter operates up to half of the nominal speed while the other solely establishes a neutral point for the winding. Moreover, the results highlight DPWM1 as a superior strategy for the DI topology, showcasing reduced converter losses. Overall, it is shown that the system’s losses can be significantly reduced just by the design of the voltage vector distribution in the drive’s operating range and the modulation strategy selection. Full article

(This article belongs to the Special Issue Modeling, Control and Design of Power Electronics Converters)

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51 pages, 1811 KiB

Open AccessEditor’s ChoiceArticle

The Influence of the Global Energy Crisis on Energy Efficiency: A Comprehensive Analysis

by Bożena Gajdzik, Radosław Wolniak, Rafał Nagaj, Brigita Žuromskaitė-Nagaj and Wieslaw Wes Grebski

Energies 2024, 17(4), 947; https://doi.org/10.3390/en17040947 - 18 Feb 2024

Cited by 17 | Viewed by 3838

Abstract

The global energy crisis, which began in 2021 due to the extraordinary economic recovery after the pandemic and intensified after Russia’s invasion of Ukraine in February 2022, has changed the conditions of energy management, paying more attention to energy efficiency. Natural gas prices [...] Read more.

The global energy crisis, which began in 2021 due to the extraordinary economic recovery after the pandemic and intensified after Russia’s invasion of Ukraine in February 2022, has changed the conditions of energy management, paying more attention to energy efficiency. Natural gas prices have reached record levels and, consequently, so have electricity prices in some markets. Oil prices have reached their highest level since 2008. Higher energy prices have contributed to sharply increased inflation. Households are again becoming interested in buying coal as a source of heat. High energy and gas prices have pushed many families into poverty and forced some factories to cut production or even close. They have also slowed economic growth to the point where some countries are heading for a serious recession. Paradoxically, the negative effects of the energy crisis may accelerate the introduction of cleaner, sustainable, renewable energy such as wind and solar energy. The energy crisis is comparable to the oil crisis of the 1970s, when it contributed to significant advances in energy efficiency. The current crisis has highlighted the importance of investments in renewable energy resources and initiated the process of integrating regional markets, developing energy efficiency and promoting renewable energies. The aim of this article is to comprehensively explore the complex relationship between energy awareness, consumption patterns, and energy efficiency, with a focus on both individual consumers and industries, during the global energy crisis. This paper is based on a literature review, overarching policy documents, energy reports, and other secondary documents. The primary research method was the systematic literature review method, based on which the impact of the global energy crisis on energy efficiency was evaluated. This study emphasizes the diverse influences on energy awareness, ranging from economic factors to consumer preferences and environmental consciousness. The findings of the paper underscore the significant responsibility of industries in contributing to energy-saving efforts and the active role of consumers in the energy market. The responsibility of industries in contributing to energy efficiency is highlighted, with a call for a comprehensive approach that integrates energy-saving criteria into product development and corporate social responsibility. Full article

(This article belongs to the Special Issue Energy Efficiency and Economic Uncertainty in Energy Market)

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16 pages, 2923 KiB

Open AccessEditor’s ChoiceArticle

Assessing the Performance of Continuous-Flow Microbial Fuel Cells and Membrane Electrode Assembly with Electrodeposited Mn Oxide Catalyst

by Laura Mais, Michele Mascia and Annalisa Vacca

Energies 2024, 17(4), 943; https://doi.org/10.3390/en17040943 - 17 Feb 2024

Viewed by 1005

Abstract

Microbial fuel cells (MFCs) are considered promising energy sources whereby chemical energy is converted into electricity via bioelectrochemical reactions utilizing microorganisms. Several factors affect MFC performance, including cathodic reduction of oxygen, electrode materials, cell internal and external resistances, and cell design. This work [...] Read more.

Microbial fuel cells (MFCs) are considered promising energy sources whereby chemical energy is converted into electricity via bioelectrochemical reactions utilizing microorganisms. Several factors affect MFC performance, including cathodic reduction of oxygen, electrode materials, cell internal and external resistances, and cell design. This work describes the effect of the catalyst coating in the air-cathode membrane electrode assembly (MEA) for a microbial fuel cell (MFC) prepared via electrodeposition of manganese oxide. The characterization of the synthesized air-cathode MFC, operating in a continuous mode, was made via electrochemical impedance spectroscopy (EIS) analyses for the determination of the intrinsic properties of the electrode that are crucial for scalability purposes. EIS analysis of the MFCs and of the MEA reveals that the anode and cathode contribute to polarization resistance by about 85% and 15%, respectively, confirming the high catalytic activity of the Mn-based air cathode. The maximum power density of the Mn-based cathode is about 20% higher than that recorded using a Pt/C electrode. Full article

(This article belongs to the Collection Renewable Energy and Energy Storage Systems)

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37 pages, 19749 KiB

Open AccessEditor’s ChoiceArticle

A Practical Framework for Developing Net-Zero Electricity Mix Scenarios: A Case Study of South Korea

by Changgi Min and Heejin Kim

Energies 2024, 17(4), 926; https://doi.org/10.3390/en17040926 - 16 Feb 2024

Cited by 1 | Viewed by 791

Abstract

This paper proposes a practical framework for developing a net-zero electricity mix scenario (NEMS), which considers detailed conditions for supply of each energy. NEMS means a path scenario for power generation amount by year of each generation resource required to achieve carbon neutrality [...] Read more.

This paper proposes a practical framework for developing a net-zero electricity mix scenario (NEMS), which considers detailed conditions for supply of each energy. NEMS means a path scenario for power generation amount by year of each generation resource required to achieve carbon neutrality in 2050. NEMS framework refers to a methodological framework that contains procedures and requirements to continuously update the NEMS by comprehensively reflecting policy changes. For evaluation of NEMS, indicators such as a system inertia resource ratio (SIRR) and a fuel conversion rate (FCR) are proposed. The proposed framework and indicators are applied for the 2050 NEMS in Korea’s electricity sector. The SIRR, indicating the ratio of inertial resources to total resources, projects values of 49% and 15% for the years 2030 and 2050, respectively. Furthermore, the FCR, reflecting the ratio of fuel conversion for resources undergoing this process, predicts that all targeted resources will have completed conversion by the year 2043. Full article

(This article belongs to the Special Issue Energy Transitions: Low-Carbon Pathways for Sustainability)

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28 pages, 9398 KiB

Open AccessEditor’s ChoiceArticle

Adaptive Sliding Mode Control Based on a Radial Neural Model Applied for an Electric Drive with an Elastic Shaft

by Grzegorz Kaczmarczyk, Radoslaw Stanislawski, Jaroslaw Szrek and Marcin Kaminski

Energies 2024, 17(4), 833; https://doi.org/10.3390/en17040833 - 9 Feb 2024

Viewed by 860

Abstract

External disturbances, uncertainties, and nonlinear behavior are problems that are commonly encountered by control system designers. In order to save on energy and materials, mechanical structures have become lighter and more flexible, which only exacerbates the control problem. To resolve this issue, robust [...] Read more.

External disturbances, uncertainties, and nonlinear behavior are problems that are commonly encountered by control system designers. In order to save on energy and materials, mechanical structures have become lighter and more flexible, which only exacerbates the control problem. To resolve this issue, robust and adaptive control strategies have been proposed and have recently gained a lot of interest in modern scientific literature. This article proposes a combination of both approaches: a sliding mode—radial basis function neural network controller applied to an electrical drive with a sophisticated mechanical structure. The proposed sliding surface provides robustness against parameter uncertainties, while the neural network adjusts itself to the current state of the drive and mitigates the oscillations resulting from the elastic connection with the load machine. This article proves the stability of the proposed control algorithm in the sense of Lyapunov, provides an in-depth numerical analysis, and compares those results with the experimental tests. The algorithm was implemented in a 1103 dSPACE fast-prototyping card and was used to control a 0.5 kW DC motor connected to the load machine by a long (thin) steel shaft. Full article

(This article belongs to the Section F: Electrical Engineering)

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17 pages, 2412 KiB

Open AccessEditor’s ChoiceArticle

Synergetic Effect of FeTi in Enhancing the Hydrogen-Storage Kinetics of Nanocrystalline MgH₂

by Roman Paramonov, Tony Spassov, Péter Nagy and Ádám Révész

Energies 2024, 17(4), 794; https://doi.org/10.3390/en17040794 - 7 Feb 2024

Cited by 1 | Viewed by 1014

Abstract

High-energy ball milling was applied to produce nanocrystalline MgH₂-FeTi powder composites. In order to achieve a remarkable synergetic effect between the two materials, the amount of the FeTi catalyst was chosen to be 40 wt.%, 50 wt.% and 60 wt.%. The [...] Read more.

High-energy ball milling was applied to produce nanocrystalline MgH₂-FeTi powder composites. In order to achieve a remarkable synergetic effect between the two materials, the amount of the FeTi catalyst was chosen to be 40 wt.%, 50 wt.% and 60 wt.%. The morphology and microstructure of the as-milled powders were characterized by scanning electron microscopy and X-ray diffraction, respectively. The evaluation of the diffraction profiles by the Convolutional Multiple Whole Profile fitting algorithm provided a detailed microstructural characterization of the coherently scattering α-MgH₂ crystallites. Differential scanning calorimetry experiments revealed two overlapping endotherms corresponding to the dehydrogenation of metastable γ-MgH₂ and stable α-MgH₂ hydrides. Isothermal hydrogen-sorption experiments were carried out in a Sieverts-type apparatus. It was established that the MgH₂-40 wt.% FeTi powder is capable of absorbing 5.8 wt.% hydrogen, while extraordinary absorption kinetics were observed for the MgH₂-50 wt.% FeTi alloy, i.e., 3.3 wt.% H₂ is absorbed after 100 s. Full article

(This article belongs to the Section A5: Hydrogen Energy)

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22 pages, 5699 KiB

Open AccessEditor’s ChoiceArticle

Energy Transition: Semi-Automatic BIM Tool Approach for Elevating Sustainability in the Maputo Natural History Museum

by Giuseppe Piras and Francesco Muzi

Energies 2024, 17(4), 775; https://doi.org/10.3390/en17040775 - 6 Feb 2024

Cited by 8 | Viewed by 1092

Abstract

Mozambique is experiencing the consequences of a severe energy crisis with economic and social impacts. Its strict dependence on hydroelectric sources is being severely tested by recent droughts that have drastically reduced water levels in dams. However, Mozambique is addressing energy poverty by [...] Read more.

Mozambique is experiencing the consequences of a severe energy crisis with economic and social impacts. Its strict dependence on hydroelectric sources is being severely tested by recent droughts that have drastically reduced water levels in dams. However, Mozambique is addressing energy poverty by exploring renewable energy sources thanks to investments in the sector by the European Union. The research concerns an energy analysis profile of the country and the penetration of renewable energy, presenting an energy upgrading scope through a semi-automatic calculation methodology in a Building Information Modeling (BIM) environment. The building under study, located in Maputo, is the Natural History Museum, which plays an important role in biodiversity conservation. Therefore, this paper proposes a BIM methodology for sizing an environmental control system tailored to serve the museum. The proposed system replaces the previous one and includes a photovoltaic system that not only meets the museum’s load but also supplies electricity to the surrounding area. Energy production from renewable sources with a surplus of 30% has been achieved. The proposed digital methodology has identified a maximum gap of 1.5% between the dimensions of the BIM duct and those of a traditional plant design, meeting ASHRAE requirements for environmental control. Full article

(This article belongs to the Section B: Energy and Environment)

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16 pages, 3912 KiB

Open AccessEditor’s ChoiceArticle

Energy and Economic Sustainability of a Small-Scale Hybrid Renewable Energy System Powered by Biogas, Solar Energy, and Wind

by Rafał Figaj

Energies 2024, 17(3), 706; https://doi.org/10.3390/en17030706 - 1 Feb 2024

Cited by 2 | Viewed by 1426

Abstract

Reduction or elimination of reliance on traditional fossil fuels and of the emission of greenhouse gases and pollutants into the environment are affecting energy technologies, systems, and applications. In this context, one potential approach to achieving sustainability, decarbonization, and ensuring the energy and [...] Read more.

Reduction or elimination of reliance on traditional fossil fuels and of the emission of greenhouse gases and pollutants into the environment are affecting energy technologies, systems, and applications. In this context, one potential approach to achieving sustainability, decarbonization, and ensuring the energy and economic viability of existing and future energy systems involves adopting one or more renewable sources. The presented paper concentrates on examining the performance of a small-scale hybrid renewable polygeneration system. This system utilizes biogas produced through anaerobic digestion, which is then supplied to an internal combustion engine, along with solar energy converted into electrical energy by photovoltaic modules and wind energy harnessed through a wind turbine. A small-scale user, represented by residential buildings and a zootechnical farm with heating, cooling, and electrical energy demands, serves as the case study. TRNSYS software is employed to design and model the system, considering realistic assumptions about technical aspects and user energy requirements. The investigation involves analyzing the system’s operation, considering both energy and economic perspectives. The paper discusses the pros and cons of combining biogas, solar, and wind energy in the proposed hybrid system under the considered case study. Despite non-satisfactory economic profitability without incentives, the proposed system allows one to save significant amounts of primary energy and carbon dioxide equivalent emissions. Full article

(This article belongs to the Special Issue Sustainable Technologies for Decarbonising the Energy Sector)

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16 pages, 7619 KiB

Open AccessEditor’s ChoiceArticle

Assessment of the Risk of the Loss of Supply, the Recycling Rate and the Degree of Substitutability of Elements in the NdFeB Magnets of a Small Wind Farm Generator

by Rafał Baron, Daniel Kowol, Piotr Matusiak, Marcin Lutyński and Katarzyna Nowińska

Energies 2024, 17(3), 671; https://doi.org/10.3390/en17030671 - 31 Jan 2024

Viewed by 940

Abstract

Existing shortages on the market of critical and strategic raw materials and problems with the supply chain of selected raw materials, mainly those from China, indicate the need to develop recycling technologies for devices containing the above-mentioned materials. The aim of this work [...] Read more.

Existing shortages on the market of critical and strategic raw materials and problems with the supply chain of selected raw materials, mainly those from China, indicate the need to develop recycling technologies for devices containing the above-mentioned materials. The aim of this work should be to ensure a sustainable supply of raw materials for industry in the EU. One potential source of raw materials may be small-power wind turbine generators equipped with permanent magnets (NdFeB). This research allowed for the development of a methodology for disassembling a generator containing NdFeB magnets in order to determine the shares of individual elements. Due to the significant shares of critical and strategic elements in permanent magnets, a detailed economic analysis was carried out. Based on the research results, economic benefits resulting from the recovery of valuable elements were indicated. The significant market value of critical and strategic raw materials contained in neodymium magnets was demonstrated. The risk of the loss of supplies, the recycling rate and the possibility of replacing the elements in permanent magnets were assessed. Full article

(This article belongs to the Special Issue Energy Security and Just Transition)

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15 pages, 7170 KiB

Open AccessEditor’s ChoiceArticle

Fluid Dynamic Assessment and Development of Nusselt Correlations for Fischer Koch S Structures

by Philipp Knödler and Volker Dreissigacker

Energies 2024, 17(3), 688; https://doi.org/10.3390/en17030688 - 31 Jan 2024

Viewed by 831

Abstract

Lattice structures such as triply periodic minimal surface (TPMS) structures have gained significance due to advancements in additive manufacturing, particularly 3D printing, which enable their engineering to be tailored to specific applications, such as heat exchangers. While traditional heat exchanger designs have been [...] Read more.

Lattice structures such as triply periodic minimal surface (TPMS) structures have gained significance due to advancements in additive manufacturing, particularly 3D printing, which enable their engineering to be tailored to specific applications, such as heat exchangers. While traditional heat exchanger designs have been extensively studied, investigations into the thermal performance of TPMS structures are limited. Considering the extensive range of the geometric design variations in TPMS structures, highly efficient structures on par with the performance of conventional heat exchanger designs can be expected. This study aims to comprehensively evaluate the thermal and flow characteristics of a specific TPMS structure (Fischer Koch S), and, in particular, the impact of various volume fractions on its heat transfer performance and on its friction factor. Another key objective of this study is to develop Nusselt and friction factor correlations as a function of the investigated volume fractions for potential use in future design tools. To this end, a broad CFD study was carried out. Additionally, this study provides insights into the procedures involved in generating Fischer Koch S geometries and the modeling methodology employed in CFD investigations. Based on the results of the CFD study, the thermal and fluid dynamic performances of Fischer Koch unit cells were evaluated, resulting in heat transfer coefficients up to 160 W/m²K for the investigated structures. A comparison between the heat transfer coefficient of the examined TPMS structure and a conventional plate heat exchanger suggested a potential increase in the heat transfer coefficient of approximately 35%. The generated CFD data were subsequently utilized to formulate fitting correlations for the Nusselt number and friction factors as a function of the volume fraction. The fitted parameters of these correlations are provided in this work. Full article

(This article belongs to the Special Issue Advances in Heat Exchangers for Sustainable Technologies Applications)

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18 pages, 3639 KiB

Open AccessEditor’s ChoiceArticle

Photovoltaic Power Generation Forecasting with Hidden Markov Model and Long Short-Term Memory in MISO and SISO Configurations

by Carlos J. Delgado, Estefanía Alfaro-Mejía, Vidya Manian, Efrain O’Neill-Carrillo and Fabio Andrade

Energies 2024, 17(3), 668; https://doi.org/10.3390/en17030668 - 30 Jan 2024

Cited by 4 | Viewed by 1022

Abstract

Photovoltaic (PV) power generation forecasting is an important research topic, aiming to mitigate variability caused by weather conditions and improve power generation planning. Climate factors, including solar irradiance, temperature, and cloud cover, influence the energy conversion achieved by PV systems. Long-term weather forecasting [...] Read more.

Photovoltaic (PV) power generation forecasting is an important research topic, aiming to mitigate variability caused by weather conditions and improve power generation planning. Climate factors, including solar irradiance, temperature, and cloud cover, influence the energy conversion achieved by PV systems. Long-term weather forecasting improves PV power generation planning, while short-term forecasting enhances control methods, such as managing ramp rates. The stochastic nature of weather variables poses a challenge for linear regression methods. Consequently, advanced, state-of-the-art machine learning (ML) approaches capable of handling non-linear data, such as long short-term memory (LSTM), have emerged. This paper introduces the implementation of a multivariate machine learning model to forecast PV power generation, considering multiple weather variables. A deep learning solution was implemented to analyze weather variables in a short time horizon. Utilizing a hidden Markov model for data preprocessing, an LSTM model was trained using the Alice Spring dataset provided by DKA Solar Center. The proposed workflow demonstrated superior performance compared to the results obtained by state-of-the-art methods, including support vector machine, radiation classification coordinate with LSTM (RCC-LSTM), and ESNCNN specifically concerning the proposed multi-input single-output LSTM model. This improvement is attributed to incorporating input features such as active power, temperature, humidity, horizontal and diffuse irradiance, and wind direction, with active power serving as the output variable. The proposed workflow achieved a mean square error (MSE) of

2.17 \times 10^{- 7}

, a root mean square error (RMSE) of

4.65 \times 10^{- 4}

, and a mean absolute error (MAE) of

4.04 \times 10^{- 4}

. Full article

(This article belongs to the Special Issue Intelligent Forecasting and Optimization in Electrical Power Systems II)

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20 pages, 1829 KiB

Open AccessEditor’s ChoiceArticle

Feasibility and Performance Analysis of Cylinder Deactivation for a Heavy-Duty Compressed Natural Gas Engine

by Daniela Anna Misul, Alex Scopelliti, Dario Di Maio, Pierpaolo Napolitano and Carlo Beatrice

Energies 2024, 17(3), 627; https://doi.org/10.3390/en17030627 - 28 Jan 2024

Viewed by 972

Abstract

The rising interest in the use of gaseous fuels, such as bio-methane and hydro-methane, in Heavy-Duty (HD) engines to reduce Greenhouse Gases pushed by the net-zero CO₂ emissions roadmap, introduced the need for appropriate strategies in terms of fuel economy and emissions [...] Read more.

The rising interest in the use of gaseous fuels, such as bio-methane and hydro-methane, in Heavy-Duty (HD) engines to reduce Greenhouse Gases pushed by the net-zero CO₂ emissions roadmap, introduced the need for appropriate strategies in terms of fuel economy and emissions reduction. The present work hence aims at analysing the potential benefits derived from the application of the cylinder deactivation strategy on a six-cylinder HD Natural Gas Spark Ignition (SI) engine, typically employed in buses and trucks. The activity stems from an extensive experimental characterisation of the engine, which allowed for validating a related 1D model at several Steady-State conditions over the entire engine workplan and during dynamic phases, represented by the World Harmonized Transient Cycle (WHTC) homologation cycle. The validated model was exploited to assess the feasibility of the considered strategy, with specific attention to the engine working areas at partial load and monitoring the main performance parameters. Moreover, the introduction in the model of an additional pipeline and of valves actuated by a dedicated control logic, allowed for embedding the capability of using Exhaust Gas Recirculation (EGR). In the identified operating zones, the EGR strategy has shown significant benefits in terms of fuel consumption, with a reduction of up to 10%. Simultaneously, an appreciable increase in the exhaust gas temperature was detected, which may eventually contribute to enhance the Three-Way Catalyst (TWC) conversion efficiency. Considering that few efforts are to be found in the literature but for the application of the cylinder deactivation strategy to Light-Duty or conventionally fuelled vehicles, the present work lays the foundation for a possible application of such technology in Natural Gas Heavy-Duty engines, providing important insights to maximise the efficiency of the entire system. Full article

(This article belongs to the Special Issue Internal Combustion Engine Performance 2023)

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17 pages, 2748 KiB

Open AccessEditor’s ChoiceArticle

Performance Evaluation of Multiple Machine Learning Models in Predicting Power Generation for a Grid-Connected 300 MW Solar Farm

by Obaid Aldosari, Salem Batiyah, Murtada Elbashir, Waleed Alhosaini and Kanagaraj Nallaiyagounder

Energies 2024, 17(2), 525; https://doi.org/10.3390/en17020525 - 22 Jan 2024

Cited by 2 | Viewed by 1152

Abstract

Integrating renewable energy sources (RES), such as photovoltaic (PV) systems, into power system networks increases uncertainty, leading to practical challenges. Therefore, an accurate photovoltaic (PV) power prediction model is required to provide essential data that supports smooth power system operation. Hence, the work [...] Read more.

Integrating renewable energy sources (RES), such as photovoltaic (PV) systems, into power system networks increases uncertainty, leading to practical challenges. Therefore, an accurate photovoltaic (PV) power prediction model is required to provide essential data that supports smooth power system operation. Hence, the work presented in this paper compares and discusses the results of different machine learning (ML) techniques in predicting the power produced by the 300 MW Sakaka PV Power Plant in the north of Saudi Arabia. The validation of the presented work is performed using real-world operational data obtained from the specified solar farm. Several performance measures, including accuracy, precision, recall, F1 Score, and mean square error (MSE), are used in this work to evaluate the performance of the different ML approaches and determine the most precise prediction model. The obtained results show that the Support Vector Machine (SVM) with a Radial basis function (RBF) is the most effective approach for optimizing solar power prediction in large-scale solar farms. Full article

(This article belongs to the Special Issue New Insights into Distributed Energy Systems)

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18 pages, 3890 KiB

Open AccessEditor’s ChoiceArticle

Life Cycle Assessment of Energy Production from Solid Waste Valorization and Wastewater Purification: A Case Study of Meat Processing Industry

by Christos Boukouvalas, Tryfon Kekes, Vasiliki Oikonomopoulou and Magdalini Krokida

Energies 2024, 17(2), 487; https://doi.org/10.3390/en17020487 - 19 Jan 2024

Cited by 2 | Viewed by 995

Abstract

The meat processing industry is a very energy-intensive and water-demanding industry that produces large amounts of solid and aqueous wastes. Therefore, methods for the effective treatment of the produced wastes have been studied in order to treat and reuse water within the industry [...] Read more.

The meat processing industry is a very energy-intensive and water-demanding industry that produces large amounts of solid and aqueous wastes. Therefore, methods for the effective treatment of the produced wastes have been studied in order to treat and reuse water within the industry and valorize the solid wastes for the production of energy and value-added products. The primary aim of this work is to evaluate the overall sustainability of energy produced from solid waste valorization and wastewater treatment in the meat processing industry via Life Cycle Assessment (LCA). For this purpose, the total environmental impact of a typical meat industry that utilizes conventional waste management methods (Scenario A) was evaluated and compared with two different industries with appropriate waste treatment/valorization processes. In the first studied valorization scenario (Scenario B), waste management is conducted using anaerobic digestion, composting, membrane bioreactors, and ultraviolet (UV) treatment, whereas in the second studied valorization scenario (Scenario C), aeration treatment, chlorination, and hydrothermal carbonization (HTC) are the selected treatment techniques. As expected, it is evident from this LCA study, that both Scenarios B and C exhibited a significantly improved environmental footprint in all studied indicators compared with Scenario A, with the reduction in certain environmental impact categories reaching up to 80%. Between the two studied alternative scenarios, the biggest improvement in the environmental footprint of the meat industry was observed in Scenario C, mainly due to the substantial quantity of the produced thermal energy. According to the results of the present case study, it is evident that the incorporation of appropriate methods in the meat industry can result in the efficient generation of energy and a significant improvement in the environmental footprint contributing to environmental safety and sustainability. Full article

(This article belongs to the Special Issue Sustainable Energy Development in Liquid Waste and Biomass)

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20 pages, 4667 KiB

Open AccessEditor’s ChoiceArticle

Integrated Waste-to-Energy Process Optimization for Municipal Solid Waste

by Hossam A. Gabbar and Muhammad Sajjad Ahmad

Energies 2024, 17(2), 497; https://doi.org/10.3390/en17020497 - 19 Jan 2024

Cited by 3 | Viewed by 1487

Abstract

Within the past few decades, thousands of experiments have been performed to characterize urban waste and biomass to estimate their bioenergy potential and product identification. There is a need to develop an integrated process model based on the experimental literature, as well as [...] Read more.

Within the past few decades, thousands of experiments have been performed to characterize urban waste and biomass to estimate their bioenergy potential and product identification. There is a need to develop an integrated process model based on the experimental literature, as well as simulations to obtain suitable products. In this study, municipal solid waste (MSW), including paper and plastic characterization and an integrated process model, were developed to optimize the final products in a reactor system. The process model has two modes, R&D and reactor control (RC), to obtain suitable products including bio-oil, char, and gases. A database was integrated based on thermokinetics, machine learning, and simulation models to optimize product efficiency. The experimental data include those obtained by thermogravimetric analysis and Fourier-transform infrared spectroscopy, which were linked to a pyrolysis experimental setup. Feedstock product mapping models were incorporated into the database along with the temperature, heating rates, elemental analysis, and final product concentration, which were utilized for the pyrolysis reactor setup. Product feasibility was conducted based on life cycle cost, affordability, and product efficiency. The present work will bridge the gap between experimental studies and decision-making based on obtained products under several experimental conditions around the world. Full article

(This article belongs to the Special Issue Advances in Sustainable Energy from Biomass and Waste)

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17 pages, 2482 KiB

Open AccessEditor’s ChoiceArticle

Comprehensive Study of SDC Memristors for Resistive RAM Applications

by Bartłomiej Garda and Karol Bednarz

Energies 2024, 17(2), 467; https://doi.org/10.3390/en17020467 - 18 Jan 2024

Cited by 1 | Viewed by 1189

Abstract

Memristors have garnered considerable attention within the scientific community as devices for emerging construction of Very Large Scale Integration (VLSI) systems. Owing to their inherent properties, they appear to be promising candidates for pivotal components in computational architectures, offering alternatives to the conventional [...] Read more.

Memristors have garnered considerable attention within the scientific community as devices for emerging construction of Very Large Scale Integration (VLSI) systems. Owing to their inherent properties, they appear to be promising candidates for pivotal components in computational architectures, offering alternatives to the conventional von Neumann architectures. This work has focused on exploring potential applications of Self-Directed Channel (SDC) memristors as novel RRAM memory cells. The introductory section of the study is dedicated to evaluating the repeatability of the tested memristors. Subsequently, a detailed account of the binary programming testing process for memristors is provided, along with illustrative characteristics depicting the impact of programming pulses on a memory cell constructed from a memristor. A comprehensive data analysis was then conducted, comparing memristors with varying types of doping. The results revealed that SDC memristors exhibit a high level of switching, certainty between the Low Resistance State (LRS) and High Resistance State (HRS), suggesting their capability to facilitate the storage of multiple bits within a single memory cell. Full article

(This article belongs to the Special Issue Linear and Nonlinear Electric Circuits: Theoretical Analysis and Applications—2nd Edition)

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16 pages, 7777 KiB

Open AccessEditor’s ChoiceArticle

Insulation Condition Assessment in Inverter-Fed Motors Using the High-Frequency Common Mode Current: A Case Study

by Mariam Saeed, Daniel Fernández, Juan Manuel Guerrero, Ignacio Díaz and Fernando Briz

Energies 2024, 17(2), 470; https://doi.org/10.3390/en17020470 - 18 Jan 2024

Cited by 2 | Viewed by 965

Abstract

The use of the common mode current for stator winding insulation condition assessment has been extensively studied. Two main approaches have been followed. The first models the electric behavior of ground-wall insulation as an equivalent

R C

circuit; these methods have been successfully [...] Read more.

The use of the common mode current for stator winding insulation condition assessment has been extensively studied. Two main approaches have been followed. The first models the electric behavior of ground-wall insulation as an equivalent

R C

circuit; these methods have been successfully applied to high-voltage high-power machines. The second uses the high frequency of the common mode current which results from the voltage pulses applied by the inverter. This approach has mainly been studied for the case of low-voltage, inverter-fed machines, and has not yet reached the level of maturity of the first. One fact noticed after a literature review is that in most cases, the faults being detected were induced by connecting external elements between winding and stator magnetic core. This paper presents a case study on the use of the high-frequency common mode current to monitor the stator insulation condition. Insulation degradation occurred progressively with the machine operating normally; no exogenous elements were added. Signal processing able to detect the degradation at early stages will be discussed. Full article

(This article belongs to the Special Issue Modeling, Control and Diagnosis of Electrical Machines and Devices)

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17 pages, 3409 KiB

Open AccessEditor’s ChoiceArticle

LPG, Gasoline, and Diesel Engines for Small Marine Vessels: A Comparative Analysis of Eco-Friendliness and Economic Feasibility

by Jeong Kuk Kim, Siljung Yeo, Jae-Hyuk Choi and Won-Ju Lee

Energies 2024, 17(2), 450; https://doi.org/10.3390/en17020450 - 17 Jan 2024

Viewed by 1369

Abstract

As an escalating global concern for environmentally sustainable marine fuels, liquefied petroleum gas (LPG) is attracting attention as an eco-friendly and economical alternative. This study explored LPG utilization in small marine vessels, focusing on its eco-friendliness and economic feasibility. To assess its environmental [...] Read more.

As an escalating global concern for environmentally sustainable marine fuels, liquefied petroleum gas (LPG) is attracting attention as an eco-friendly and economical alternative. This study explored LPG utilization in small marine vessels, focusing on its eco-friendliness and economic feasibility. To assess its environmental implications, the AVL FIRE simulation program was used to compare CO₂, CO, NO, and soot emissions from LPG engines with those from conventional gasoline and diesel engines. The LPG engine model relied on data from a pioneering type-approved experimental LPG engine designed for small South Korean marine vessels, while parameters for gasoline and diesel engines were adjusted to suit their distinctive features. Regarding long-term economic feasibility, assuming a 30-year ship lifespan, incorporating 2022 annual average prices, average annual price growth rates, and annual fuel consumption data of each fuel, results indicate that LPG engines exhibited lower CO₂, CO, NO, and soot emissions than conventional engines, except that NO emissions were higher than gasoline engines. Evaluating LPG’s economic feasibility over a 30-year ship life cycle for an individual vessel revealed varying fuel cost savings, with the greatest savings observed in gasoline–other (KRW 2220.7 million) and the least in gasoline–coastal (KRW 1152.5 million). These findings offer vital insights for ship operators and policymakers seeking a balance between eco-friendliness and cost-effectiveness, as well as LPG engine technology emerging as pivotal for a sustainable future, harmonizing environmental protection and economic viability. Full article

(This article belongs to the Special Issue Internal Combustion Engine Performance 2023)

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22 pages, 2989 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of a Simplified Model for Three-Phase Equilibrium Calculations of Mixed Gas Hydrates

by Panagiotis Kastanidis, George E. Romanos, Athanasios K. Stubos, Georgia Pappa, Epaminondas Voutsas and Ioannis N. Tsimpanogiannis

Energies 2024, 17(2), 440; https://doi.org/10.3390/en17020440 - 16 Jan 2024

Viewed by 1192

Abstract

In this study, we perform an extensive evaluation of a simple model for hydrate equilibrium calculations of binary, ternary, and limited quaternary gas hydrate systems that are of practical interest for separation of gas mixtures. We adopt the model developed by Lipenkov and [...] Read more.

In this study, we perform an extensive evaluation of a simple model for hydrate equilibrium calculations of binary, ternary, and limited quaternary gas hydrate systems that are of practical interest for separation of gas mixtures. We adopt the model developed by Lipenkov and Istomin and analyze its performance at temperature conditions higher than the lower quadruple point. The model of interest calculates the dissociation pressure of mixed gas hydrate systems using a simple combination rule that involves the hydrate dissociation pressures of the pure gases and the gas mixture composition, which is at equilibrium with the aqueous and hydrate phases. Such an approach has been used extensively and successfully in polar science, as well as research related to space science where the temperatures are very low. However, the particular method has not been examined for cases of higher temperatures (i.e., above the melting point of the pure water). Such temperatures are of interest to practical industrial applications. Gases of interest for this study include eleven chemical components that are related to industrial gas-mixture separations. Calculations using the examined methodology, along with the commercial simulator CSMGem, are compared against experimental measurements, and the range of applicability of the method is delineated. Reasonable agreement (particularly at lower hydrate equilibrium pressures) between experiments and calculations is obtained considering the simplicity of the methodology. Depending on the hydrate-forming mixture considered, the percentage of absolute average deviation in predicting the hydrate equilibrium pressure is found to be in the range 3–91%, with the majority of systems having deviations that are less than 30%. Full article

(This article belongs to the Special Issue Recent Advances in Gas Hydrate Research Related to the Flow, Storage and Transport of Gases)

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31 pages, 5697 KiB

Open AccessEditor’s ChoiceArticle

Fuzzy Approach for Managing Renewable Energy Flows for DC-Microgrid with Composite PV-WT Generators and Energy Storage System

by Mario Versaci and Fabio La Foresta

Energies 2024, 17(2), 402; https://doi.org/10.3390/en17020402 - 13 Jan 2024

Cited by 5 | Viewed by 1235

Abstract

Recently, the implementation of software/hardware systems based on advanced artificial intelligence techniques for continuous monitoring of the electrical parameters of intelligent networks aimed at managing and controlling energy consumption has been of great interest. The contribution of this paper, starting from a recently [...] Read more.

Recently, the implementation of software/hardware systems based on advanced artificial intelligence techniques for continuous monitoring of the electrical parameters of intelligent networks aimed at managing and controlling energy consumption has been of great interest. The contribution of this paper, starting from a recently studied DC-MG, fits into this context by proposing an intuitionistic fuzzy Takagi–Sugeno approach optimized for the energy management of isolated direct current microgrid systems consisting of a photovoltaic and a wind source. Furthermore, a lead-acid battery guarantees the stability of the DC bus while a hydrogen cell ensures the reliability of the system by avoiding blackout conditions and increasing interaction with the loads. The fuzzy rule bank, initially built using the expert’s knowledge, is optimized with the aforementioned procedure, maximizing external energy and minimizing consumption. The complete scheme, modeled using MatLab/Simulink, highlighted performance comparable to fuzzy Takagi–Sugeno systems optimized using a hybrid approach based on particle swarm optimization (to structure the antecedents of the rules) and minimum batch squares (to optimize the output). Full article

(This article belongs to the Special Issue Advanced PV Solutions for Achieving the NZEB Goal)

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15 pages, 3133 KiB

Open AccessEditor’s ChoiceArticle

Thermal Decomposition and Kinetic Parameters of Three Biomass Feedstocks for the Performance of the Gasification Process Using a Thermogravimetric Analyzer

by Rania Almusafir and Joseph D. Smith

Energies 2024, 17(2), 396; https://doi.org/10.3390/en17020396 - 12 Jan 2024

Cited by 2 | Viewed by 973

Abstract

Thermogravimetric analysis (TGA) is a powerful technique and useful method for characterizing biomass as a non-conventional fuel. A TGA apparatus has been utilized to experimentally investigate the impact of biomass feedstock diversity on the performance of the gasification of hardwood (HW), softwood (SW) [...] Read more.

Thermogravimetric analysis (TGA) is a powerful technique and useful method for characterizing biomass as a non-conventional fuel. A TGA apparatus has been utilized to experimentally investigate the impact of biomass feedstock diversity on the performance of the gasification of hardwood (HW), softwood (SW) pellets, and refuse-derived fuel (RDF) materials. The solid conversion rate and the volatile species formation rate have been estimated to quantify the rates of devolatilization for each material. In addition, the combustion kinetic characteristics of the three biomass feedstocks were investigated using TGA at different heating rates, and a thermal kinetic analysis was conducted to describe the gasification process. Therefore, the kinetic parameters have been evaluated for different thermal reactions and non-isothermal kinetic models that depend on the relationships between heating rates and temperature profiles. The results show that the amount of tar content from the RDF was higher than that of pure hardwood and softwood feedstocks. Hence, tar removal must be part of any process using syngas produced from RDF feedstocks in a gas engine to produce electricity. Full article

(This article belongs to the Special Issue Energy Economics: Global Trends in Technology and Policy)

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18 pages, 748 KiB

Open AccessEditor’s ChoiceArticle

Can Electric Vehicle Carsharing Bridge the Green Divide? A Study of BlueLA’s Environmental Impacts among Underserved Communities and the Broader Population

by Ziad Yassine, Elliot W. Martin and Susan A. Shaheen

Energies 2024, 17(2), 356; https://doi.org/10.3390/en17020356 - 10 Jan 2024

Viewed by 1039

Abstract

This study aims to evaluate the potential of electric vehicle (EV) carsharing services to address social and environmental disparities in urban transportation through an evaluation of BlueLA, a one-way station-based carsharing service in Los Angeles, California. BlueLA provides a clean and affordable mobility [...] Read more.

This study aims to evaluate the potential of electric vehicle (EV) carsharing services to address social and environmental disparities in urban transportation through an evaluation of BlueLA, a one-way station-based carsharing service in Los Angeles, California. BlueLA provides a clean and affordable mobility option in underserved communities that face significant air quality burdens and have historically been excluded from environmental benefits. By incorporating BlueLA trip activity data from January 2021 to December 2022 (n = 59,112 trips) and an online user survey implemented in early December 2022 (n = 215 responses), we estimate the impacts of BlueLA on personal vehicle ownership patterns, vehicle miles traveled (VMT), and associated greenhouse gas (GHG) emissions. The results show an overall net reduction in VMT and GHG emissions of 463,845 miles and 656 metric tons, respectively, among the BlueLA user population (3074 registered users). When disaggregating impacts by BlueLA member type, our findings show a net reduction of 234 and 371 metric tons in GHG emissions for Standard (general population) and Community (low-income qualified) members, respectively. Additionally, our socio-demographic analysis highlights clear disparities between these two member groups, with Community members typically having lower incomes (i.e., 74% earning below USD 50,000 annually); lower educational attainment (i.e., 46% with at most an associate’s degree); and larger households (i.e., 23% living in households of four or more) compared to Standard members (i.e., 19% earning below USD 50,000, 24% with at most an associate’s degree, and 9% in households of four or more). Moreover, when comparing the VMT and associated GHG emissions due to BlueLA, we find that the presence of BlueLA reduces VMT and GHG emissions by 34% and 48% respectively, and each BlueLA vehicle replaces 16 personally owned vehicles (shed and postponed purchases). Last, when comparing the emissions produced by the electric fleet of BlueLA to those of a comparable fleet of internal combustion engine vehicles, we find that the use of an EV fleet reduces GHG emissions by 43% in comparison. The BlueLA carsharing service has led to notable net reductions in VMT and thus GHG emissions, with a major share of these reductions observed among Community members. Full article

(This article belongs to the Section E: Electric Vehicles)

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15 pages, 5343 KiB

Open AccessEditor’s ChoiceArticle

Predicting Steam Turbine Power Generation: A Comparison of Long Short-Term Memory and Willans Line Model

by Mostafa Pasandideh, Matthew Taylor, Shafiqur Rahman Tito, Martin Atkins and Mark Apperley

Energies 2024, 17(2), 352; https://doi.org/10.3390/en17020352 - 10 Jan 2024

Cited by 1 | Viewed by 1350

Abstract

This study focuses on using machine learning techniques to accurately predict the generated power in a two-stage back-pressure steam turbine used in the paper production industry. In order to accurately predict power production by a steam turbine, it is crucial to consider the [...] Read more.

This study focuses on using machine learning techniques to accurately predict the generated power in a two-stage back-pressure steam turbine used in the paper production industry. In order to accurately predict power production by a steam turbine, it is crucial to consider the time dependence of the input data. For this purpose, the long-short-term memory (LSTM) approach is employed. Correlation analysis is performed to select parameters with a correlation coefficient greater than 0.8. Initially, nine inputs are considered, and the study showcases the superior performance of the LSTM method, with an accuracy rate of 0.47. Further refinement is conducted by reducing the inputs to four based on correlation analysis, resulting in an improved accuracy rate of 0.39. The comparison between the LSTM method and the Willans line model evaluates the efficacy of the former in predicting production power. The root mean square error (RMSE) evaluation parameter is used to assess the accuracy of the prediction algorithm used for the generator’s production power. By highlighting the importance of selecting appropriate machine learning techniques, high-quality input data, and utilising correlation analysis for input refinement, this work demonstrates a valuable approach to accurately estimating and predicting power production in the energy industry. Full article

(This article belongs to the Special Issue Machine Learning and Deep Learning for Energy Systems II)

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17 pages, 5216 KiB

Open AccessEditor’s ChoiceArticle

Application of Hydrodynamic Cavitation in the Disintegration of Aerobic Granular Sludge—Evaluation of Pretreatment Time on Biomass Properties, Anaerobic Digestion Efficiency and Energy Balance

by Marcin Zieliński, Marcin Dębowski, Joanna Kazimierowicz, Anna Nowicka and Magda Dudek

Energies 2024, 17(2), 335; https://doi.org/10.3390/en17020335 - 9 Jan 2024

Cited by 5 | Viewed by 1572

Abstract

The use of aerobic granular sludge is a promising and future-proof solution for wastewater treatment. The implementation of this technology requires the development of efficient and cost-effective methods for the management of excess sludge. The aim of the research was to evaluate the [...] Read more.

The use of aerobic granular sludge is a promising and future-proof solution for wastewater treatment. The implementation of this technology requires the development of efficient and cost-effective methods for the management of excess sludge. The aim of the research was to evaluate the effects of hydrodynamic cavitation on the efficiency of aerobic granular sludge digestion. Respirometric measurements were performed at a temperature of 38 °C and an initial organic load of 5.0 gVS/L. The changes in the properties of the pretreated biomass, the kinetics of methane fermentation, the amount and composition of the biogas produced, and an energetic evaluation of the process were carried out. A significant influence of hydrodynamic cavitation on the transfer of organic compounds into the dissolved phase was demonstrated. The degree of solubilisation was 37% for COD and 42% and for TOC. The efficiency of CH₄ production from the pretreated sludge reached a value of 496 ± 12 mL/gVS, which corresponds to an increase of 19.6% compared to the raw biomass. The influence of cavitation on the CH₄ content of the biogas was not observed. Strong correlations were found between the efficiency of anaerobic digestion and the concentration of dissolved organic compounds and the hydrodynamic cavitation time used. The gross energy yield was closely correlated with the amount of CH₄. The highest comparable values of 3.12 Wh/gTS to 3.18 Wh/gTS were found in the variants in which the hydrodynamic cavitation (HC) time was between 15 min and 50 min. The highest net energy production of 2890 kWh/MgTS was achieved after 15 min of pretreatment. Full article

(This article belongs to the Special Issue From Waste to Energy: Anaerobic Digestion Technologies)

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19 pages, 8688 KiB

Open AccessEditor’s ChoiceArticle

IoT-Based Indoor Thermal Environment and Occupancy Monitoring for Energy Poverty Care

by Woo-Seung Yun, Wontaek Ryu, Hyuncheol Seo, Won-hwa Hong and Seung-Woo Lee

Energies 2024, 17(2), 326; https://doi.org/10.3390/en17020326 - 9 Jan 2024

Cited by 1 | Viewed by 1184

Abstract

Energy poverty, defined as difficulty meeting the minimum requirements for a thermal environment, is becoming a significant social issue. To provide efficient welfare services, information provision and monitoring are required. However, characteristics of energy poverty, such as inconsistent residential patterns, small living spaces, [...] Read more.

Energy poverty, defined as difficulty meeting the minimum requirements for a thermal environment, is becoming a significant social issue. To provide efficient welfare services, information provision and monitoring are required. However, characteristics of energy poverty, such as inconsistent residential patterns, small living spaces, and limited electricity and telecommunication resources, lead to a lack of information. This research introduces the empirical results of the development of the system. Based on the feedback from welfare workers and experts supporting energy poverty, a monitoring system combining various sensors was prototyped. This system measures temperature, humidity, illuminance, air velocity, CO₂, black bulb temperature, occupancy, and noise and generates indicators for occupancy and thermal environment monitoring. Applicability assessment was conducted across 55 energy poverty households in Korea during the duration of cooling and heating. Subjects were living in spaces averaging 6.3 sqm within buildings over 43 years old and renting on a monthly or weekly basis. Electricity and communication are partially supplied. Based on the actual measurement data and field surveys, the configuration of an energy poverty monitoring system was proposed. In particular, the applicability of the simple methodology for the determination of black bulb temperature, metabolic rate, and clothing insulation required for a thermal environment evaluation was assessed. The proposed system can be efficiently used for taking care of energy poverty where the installation of conventional monitoring systems is restricted. Full article

(This article belongs to the Section G: Energy and Buildings)

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17 pages, 2484 KiB

Open AccessEditor’s ChoiceArticle

Exergy-Based Optimization of a CO₂ Polygeneration System: A Multi-Case Study

by Bourhan Tashtoush, Jing Luo and Tatiana Morosuk

Energies 2024, 17(2), 291; https://doi.org/10.3390/en17020291 - 6 Jan 2024

Viewed by 869

Abstract

A polygeneration system for power, heat, and refrigeration has been evaluated and optimized using exergy-based methods. CO₂ is the working fluid. The study considered two environmental conditions for the potential implementation of the polygeneration system: cold (Case_cold) and hot (Case [...] Read more.

A polygeneration system for power, heat, and refrigeration has been evaluated and optimized using exergy-based methods. CO₂ is the working fluid. The study considered two environmental conditions for the potential implementation of the polygeneration system: cold (Case_cold) and hot (Case_hot). Aspen HYSYS^® was used to perform steady-state simulations, Python was used for the automation of the process, and the connection of Aspen HYSYS^® with Python was successfully applied for single-objective and multi-objective optimizations. A wide range of decision variables was implemented. The minimization of the average cost of a product per unit of exergy was the goal of single-objective optimization and was included in the multi-objective optimization in addition to the maximization of the overall exergy efficiency. Single-objective and multi-objective optimization were applied. Both optimization algorithms result in the necessity to increase the pinch temperature in the heat exchanger (ΔT_pinch,HE), maintain the pinch temperature in the gas cooler (ΔT_pinch,GC), and augment this value for the evaporator (ΔT_pinch,EVAP). Notably, higher isentropic efficiency for turbomachinery correlates with improved optimization outcomes. These findings contribute to the applicability and performance of the polygeneration system, offering potential advancements in sustainable energy solutions. Full article

(This article belongs to the Special Issue Solar Energy for Cooling and Power Generation)

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38 pages, 2269 KiB

Open AccessEditor’s ChoiceArticle

Investigating the Role of Byproduct Oxygen in UK-Based Future Scenario Models for Green Hydrogen Electrolysis

by Cameron Campbell-Stanway, Victor Becerra, Shanker Prabhu and James Bull

Energies 2024, 17(2), 281; https://doi.org/10.3390/en17020281 - 5 Jan 2024

Cited by 2 | Viewed by 1627

Abstract

Water electrolysis for hydrogen production with renewable electricity is regularly studied as an option for decarbonised future energy scenarios. The inclusion of byproduct electrolytic oxygen capture and sale is of interest for parallel decarbonisation efforts elsewhere in the industry and could contribute to [...] Read more.

Water electrolysis for hydrogen production with renewable electricity is regularly studied as an option for decarbonised future energy scenarios. The inclusion of byproduct electrolytic oxygen capture and sale is of interest for parallel decarbonisation efforts elsewhere in the industry and could contribute to reducing green hydrogen costs. A deterministic hydrogen electrolysis system model is constructed to compare oxygen inclusion/exclusion scenarios. This uses wind and solar-PV electricity generation timeseries, a power-dependent electrolysis model to determine the energy efficiency of gas yield, and power allocation for gas post-processing energy within each hourly timestep. This maintains a fully renewable (and therefore low/zero carbon) electricity source for electrolysis and gas post-processing. The model is validated (excluding oxygen) against an existing low-cost GW-scale solar-hydrogen production scenario and an existing hydrogen production costs study with offshore wind generation at the multi-MW scale. For both comparisons, oxygen inclusion is then evaluated to demonstrate both the benefits and drawbacks of capture and utilisation, for different scenario conditions, and high parameter sensitivity can be seen regarding the price of renewable electricity. This work subsequently proposes that the option for the potential utilisation of byproduct oxygen should be included in future research to exemplify otherwise missed benefits. Full article

(This article belongs to the Special Issue Green Hydrogen Production from Water Electrolysis Technologies)

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13 pages, 1939 KiB

Open AccessEditor’s ChoiceArticle

Enzymatic In Situ Interesterification of Rapeseed Oil with Methyl Formate in Diesel Fuel Medium

by Violeta Makareviciene, Kiril Kazancev, Egle Sendzikiene and Milda Gumbyte

Energies 2024, 17(2), 282; https://doi.org/10.3390/en17020282 - 5 Jan 2024

Viewed by 719

Abstract

The purpose of this research was to evaluate the process of enzymatic biodiesel synthesis by directly using rapeseed as a raw material, extracting the oil contained within and interesterifying with a mixture of methyl formate and mineral diesel, choosing the amount of mineral [...] Read more.

The purpose of this research was to evaluate the process of enzymatic biodiesel synthesis by directly using rapeseed as a raw material, extracting the oil contained within and interesterifying with a mixture of methyl formate and mineral diesel, choosing the amount of mineral diesel so that the ratio between it and the rapeseed oil in the seeds was 9:1. As the final product of the interesterification process, a mixture of mineral diesel and biodiesel was obtained directly, which is conventionally produced by mixing the mineral diesel and biodiesel. The tests were performed using enzymatic catalysis using the lipase Lipozyme TL TIM. Process optimization was performed using the response surface methodology. A model describing the interaction of three independent variables and their influence on the yield of rapeseed oil methyl esters was developed. The physical and chemical indicators of the product obtained under optimal interesterification conditions were evaluated. Full article

(This article belongs to the Special Issue Biomass, Biofuels and Waste: 2nd Edition)

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22 pages, 12382 KiB

Open AccessEditor’s ChoiceArticle

Assessing Combined High Photovoltaic and Electric Vehicle Charging Penetration in Low-Voltage Distribution Networks: A Case Study in Malta

by Brian Azzopardi and Yesbol Gabdullin

Energies 2024, 17(1), 263; https://doi.org/10.3390/en17010263 - 4 Jan 2024

Cited by 1 | Viewed by 1069

Abstract

High Photovoltaic (PV) and Electric Vehicle (EV) Charging Penetration challenges the grid’s Low-Voltage (LV) Distribution Network’s stability due to voltage variations and the overloading of feeders. This research paper investigates the potential of combined PV and Electric Vehicle (EV) charging integration within LV [...] Read more.

High Photovoltaic (PV) and Electric Vehicle (EV) Charging Penetration challenges the grid’s Low-Voltage (LV) Distribution Network’s stability due to voltage variations and the overloading of feeders. This research paper investigates the potential of combined PV and Electric Vehicle (EV) charging integration within LV DN, using a representative DN in Malta as a case study. The European Union (EU) has set forth objectives and guidelines that suggest a high likelihood of Distributed Networks (DNs) incorporating a significant number of Photovoltaic Systems (PVs), resulting in overvoltage occurrences, as well as a substantial number of Electric Vehicles (EVs), which may charge in an erratic manner, leading to undervoltage and overloading events. A distribution network (DN) may experience unfavorable situations concurrently due to the simultaneous occurrence of photovoltaic (PV) generation and electric vehicle (EV) charging, particularly in residential case studies. Effectively employing either dispersed or centralized storage is a viable approach to tackle these issues. However, this strategy may defer the requirement for expensive DN investments. The study showcases the extent of automated mitigation attained in the urban zones of Malta. The data presented primarily comprises empirical measurements obtained at the onset of the LV feeder. Full article

(This article belongs to the Special Issue Selected Papers from MEDPOWER 2022—the 13th Mediterranean Conference on Power Generation, Transmission, Distribution and Energy Conversion)

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10 pages, 3280 KiB

Open AccessEditor’s ChoiceArticle

Electrochromic Polymers: From Electrodeposition to Hybrid Solid Devices

by Hadarou Sare and Dongmei Dong

Energies 2024, 17(1), 232; https://doi.org/10.3390/en17010232 - 1 Jan 2024

Cited by 1 | Viewed by 1085

Abstract

This paper reports on the linear colorimetric and electrochromic (EC) characteristics of electrodeposited polyaniline (PANI) films. This paper also investigates the infrared EC properties of acid-doped PANI films. The electrochemical polymerization method was employed to create a porous and thin PANI film layer [...] Read more.

This paper reports on the linear colorimetric and electrochromic (EC) characteristics of electrodeposited polyaniline (PANI) films. This paper also investigates the infrared EC properties of acid-doped PANI films. The electrochemical polymerization method was employed to create a porous and thin PANI film layer onto PET-ITO substrates. This layer was capped with WO₃ film to create a gel electrolyte sandwich structure that demonstrates the compatibility of PANI films with cathodic WO₃ films in full devices. The electrodeposition of the film was fabricated by applying different voltages and time, with the optimal film quality achieved with the 1.7 V voltage and a 20 min deposition period. The surface morphology, optical performance, electrochemical behavior, and molecular structure evolution are comprehensively studied in this work. The linear colorimetric behaviors and the corresponding significant changes in the structure in Raman spectra build direct strong quantitative relations in EC polymers. The well-defined oxidation and reduction peaks observed in the cyclic voltammetry indicate the ion-diffusion dominant process in the electrochromism of PANI. Significant transitions between the benzene and quinone phases in the Raman spectra are found in the bleached and colored states of polymers. This study enhances the understanding of PANI film structure and electrochemical and associated optical properties, providing more insights into the dual-function EC charge storage polymers and other energy-related functional materials. Full article

(This article belongs to the Special Issue Thin Films for Renewable Energy Production, Storage and Conversion)

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30 pages, 20623 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Cooling Strategy Optimization of Cylindrical Lithium-Ion Battery Pack via Multi-Counter Cooling Channels

by Hyeonchang Jeon, Seokmoo Hong, Jinwon Yun and Jaeyoung Han

Energies 2023, 16(23), 7860; https://doi.org/10.3390/en16237860 - 30 Nov 2023

Cited by 1 | Viewed by 1918

Abstract

This study focused on the design of a battery pack cooling channel based on a Tesla Model S electric car. This study aimed to achieve a balance between cooling efficiency and pressure drop while maintaining safe and optimal operating temperatures for the batteries. [...] Read more.

This study focused on the design of a battery pack cooling channel based on a Tesla Model S electric car. This study aimed to achieve a balance between cooling efficiency and pressure drop while maintaining safe and optimal operating temperatures for the batteries. A cooling channel design similar to the basic type employed in the Tesla Model S using 448 cylindrical Li-ion batteries was considered. Consequently, important parameters, such as the maximum temperature and temperature difference in the battery cells in a module, as well as the pressure drop of the coolant, were analyzed. In addition, the characteristics of the temperature changes in each cooling channel shape were investigated. The temperature limit for the battery in a module and the temperature limit difference were set to 40 °C and 5 °C, respectively, to evaluate the performance of the cooling system. Further, the effects of discharge rates (3C and 5C), cooling channel shapes (counter flow and parallel types), and coolant inlet velocities (0.1, 0.2, 0.3, and 0.4 m/s) on battery thermal management were analyzed. The results revealed that the parallel type channel yielded a lower pressure drop than the basic type channel; however, it was not as effective in removing heat from the battery. In contrast, the counter flow type channel effectively removed heat from the batteries with a higher coolant pressure drop in the channel. Therefore, a multi-counter flow type cooling channel combining the advantages of both these channels was proposed to decrease the pressure drop while maintaining appropriate operating temperatures for the battery module. The proposed cooling channel exhibited an excellent cooling performance with lower power consumption and better heat transfer characteristics. However, relatively minimal differences were confirmed for the maximum temperature and temperature difference in the battery module compared with the counter flow type. Therefore, the proposed cooling channel type can be implemented to ensure the optimal temperature operation of the battery module and to decrease system power consumption. Full article

(This article belongs to the Section D2: Electrochem: Batteries, Fuel Cells, Capacitors)

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23 pages, 4327 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Model-Driven Membrane Electrode Assembly Design for High-Performing Open-Cathode Polymer Electrolyte Membrane Fuel Cells

by Anand Sagar, Sachin Chugh and Erik Kjeang

Energies 2023, 16(22), 7472; https://doi.org/10.3390/en16227472 - 7 Nov 2023

Cited by 1 | Viewed by 924

Abstract

Open-cathode fuel cells use air cooling to effectively reduce system cost. However, due to the challenging hygrothermal environment, they generally suffer from low performance compared to conventional, liquid-cooled cells. A pre-validated, three-dimensional computational model is used in the present work to determine the [...] Read more.

Open-cathode fuel cells use air cooling to effectively reduce system cost. However, due to the challenging hygrothermal environment, they generally suffer from low performance compared to conventional, liquid-cooled cells. A pre-validated, three-dimensional computational model is used in the present work to determine the effects of different sub-component designs, namely the polymeric membrane, composition of the cathode catalyst layer (CCL), and structure of the cathode microporous layer (CMPL), on the performance of an open-cathode fuel cell. This comprehensive parametric study performed on a total of 90 cases shows the increment in current density to be 7% and 31% by improvising the membrane and CCL design, respectively, at 0.6 V. A steep increase of 87% is also achieved by strategically modifying the CMPL design at 0.4 V operation. An overall increment of 119% and 131% in current density is achieved for the best membrane electrode assembly (MEA) design at 0.6 and 0.4 V, respectively, as compared to the baseline design. These improvements are achieved by collective improvements in kinetics, oxygen mass transport, ohmic resistance, self-heating, and water retention in the ionomer phase. The proposed MEA design could facilitate open-cathode fuel cell stacks with 2× higher power output or 56% lower weight and materials cost for a given power demand. Full article

(This article belongs to the Section A5: Hydrogen Energy)

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26 pages, 5952 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Equipment- and Time-Constrained Data Acquisition Protocol for Non-Intrusive Appliance Load Monitoring

by Konstantinos Koasidis, Vangelis Marinakis, Haris Doukas, Nikolaos Doumouras, Anastasios Karamaneas and Alexandros Nikas

Energies 2023, 16(21), 7315; https://doi.org/10.3390/en16217315 - 28 Oct 2023

Cited by 1 | Viewed by 1369

Abstract

Energy behaviours will play a key role in decarbonising the building sector but require the provision of tailored insights to assist occupants to reduce their energy use. Energy disaggregation has been proposed to provide such information on the appliance level without needing a [...] Read more.

Energy behaviours will play a key role in decarbonising the building sector but require the provision of tailored insights to assist occupants to reduce their energy use. Energy disaggregation has been proposed to provide such information on the appliance level without needing a smart meter plugged in to each load. However, the use of public datasets with pre-collected data employed for energy disaggregation is associated with limitations regarding its compatibility with random households, while gathering data on the ground still requires extensive, and hitherto under-deployed, equipment and time commitments. Going beyond these two approaches, here, we propose a novel data acquisition protocol based on multiplexing appliances’ signals to create an artificial database for energy disaggregation implementations tailored to each household and dedicated to performing under conditions of time and equipment constraints, requiring that only one smart meter be used and for less than a day. In a case study of a Greek household, we train and compare four common algorithms based on the data gathered through this protocol and perform two tests: an out-of-sample test in the artificially multiplexed signal, and an external test to predict the household’s appliances’ operation based on the time series of a real total consumption signal. We find accurate monitoring of the operation and the power consumption level of high-power appliances, while in low-power appliances the operation is still found to be followed accurately but is also associated with some incorrect triggers. These insights attest to the efficacy of the protocol and its ability to produce meaningful tips for changing energy behaviours even under constraints, while in said conditions, we also find that long short-term memory neural networks consistently outperform all other algorithms, with decision trees closely following. Full article

(This article belongs to the Special Issue Energy Efficiency of the Buildings II)

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14 pages, 3847 KiB

Open AccessEditor’s ChoiceArticle

Combined Effect of In Situ Stress Level and Bedding Anisotropy on Hydraulic Fracture Vertical Growth in Deep Marine Shale Revealed via CT Scans and Acoustic Emission

by Peng Guo, Xiao Li, Shouding Li and Tianqiao Mao

Energies 2023, 16(21), 7270; https://doi.org/10.3390/en16217270 - 26 Oct 2023

Cited by 1 | Viewed by 1126

Abstract

The economic exploitation of unconventional gas and oil in deep shale relies closely on effective hydraulic fracturing stimulations. However, the fracturing operations of deep shale reservoirs face challenges of insufficient fracture growth and a rapid decline in productivity due to the increasing in [...] Read more.

The economic exploitation of unconventional gas and oil in deep shale relies closely on effective hydraulic fracturing stimulations. However, the fracturing operations of deep shale reservoirs face challenges of insufficient fracture growth and a rapid decline in productivity due to the increasing in situ stress level. In addition, the shale strata on the margin of the Sichuan Basin are frequently folded and faulted, and the change in bedding inclinations significantly complicates the process of hydraulic fracturing. The investigation of the combined effect of the in situ stress level and bedding anisotropy on the hydraulic fracture configuration is vital for fracturing engineering design. To analyze this, we conducted hydraulic fracturing tests on shale cores to simulate the hydraulic fracture initiation and growth from a horizontally positioned perforation. By using acoustic emission detection and CT scans, the influence of natural stress levels and the angle of the shale’s bedding on the process of hydraulic fracturing in shale and the resulting fracture geometry were analyzed. The results showed that the area of hydraulic fracture under a higher stress level (σ₁ = 50 MPa, σ₃ = 40 MPa) was about 13%~23% smaller than that created under the lower stress level (σ₁ = 30 MPa, σ₃ = 20 MPa) when the bedding angle was smaller than 60°. With the increase in bedding angle, the curves of the fracture area and fracture network index under two different stress levels presented similar decreasing trends. Also, the time from micro-crack generation to sample breakdown was significantly reduced when the bedding orientation changed from the horizontal to vertical position. The increasing stress level significantly increased the breakdown pressure. In particular, the fracturing of shale samples with bedding angles of 0° and 30° required a higher fluid pressure and released more energy than samples with larger bedding inclinations. Additionally, the measurement of the sample radial deformation indicated that the hydraulic fracture opening extent was reduced by about 46%~81% with the increasing stress level. Full article

(This article belongs to the Topic Structural Characterization and Hydraulic Fracturing Responses of Deep-Buried Geomaterials)

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22 pages, 12874 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

An Experimental and Detailed Kinetics Modeling Study of Norbornadiene in Hydrogen and Methane Mixtures: Ignition Delay Time and Spectroscopic CO Measurements

by Matthew G. Sandberg, Claire M. Grégoire, Darryl J. Mohr, Olivier Mathieu and Eric L. Petersen

Energies 2023, 16(21), 7278; https://doi.org/10.3390/en16217278 - 26 Oct 2023

Viewed by 1070

Abstract

High-energy-density compounds such as norbornadiene (NBD) are being considered as potential cost-effective fuel additives, or partial replacements, for high-speed propulsion applications. To assess the ability of NBD to influence basic fuel reactivity enhancement and to build a database for developing future NBD kinetics [...] Read more.

High-energy-density compounds such as norbornadiene (NBD) are being considered as potential cost-effective fuel additives, or partial replacements, for high-speed propulsion applications. To assess the ability of NBD to influence basic fuel reactivity enhancement and to build a database for developing future NBD kinetics models, ignition delay times were measured in two shock-tube facilities at Texas A&M University for H₂/O₂, CH₄/O₂, H₂/NBD/O₂, and CH₄/NBD/O₂ mixtures (ϕ = 1) that were highly diluted in argon. The reflected-shock temperatures ranged from 1014 to 2227 K, and the reflected-shock pressures remained near 1 atm for all of the experiments, apart from the hydrogen mixtures, which were also tested near 7 atm, targeting the second-explosion limit. The molar concentrations of NBD were supplemented to the baseline mixtures representing 1–2% of the fuel by volume. A chemiluminescence diagnostic was used to track the time history of excited hydroxyl radical (OH*) emission, which was used to define the ignition delay time at the sidewall location. Spectroscopic CO data were also obtained using a tunable quantum cascade laser to complement both the ignition and the chemiluminescence data. The CH₄/O₂ mixtures containing NBD demonstrated reduced ignition delay times, with a pronounced effect at lower temperatures. Conversely, this additive increased the ignition delay time dramatically in the H₂/O₂ mixture, which was attributed to changes in the fundamental chemistry with the introduction of molecules containing carbon bonds, which require stronger activation energies for ignition. Correlations were developed to predict the ignition delay time, which depends on species concentration, temperature, and pressure. Additionally, one tentative mechanism was tested, combining base chemistry from NUIGMech 1.1 with pyrolysis and oxidation reactions for NBD using the recent efforts from experimental and theoretical literature studies. The numerical predictions show that the rapid decomposition of NBD provides a pool of active H-radicals, significantly increasing the reactivity of methane. This study represents the first set of gas-phase ignition and CO time-history data measured in a shock tube for hydrogen and methane mixtures containing the additive NBD. Full article

(This article belongs to the Special Issue Advances in Fuels and Combustion)

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17 pages, 22879 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Influence of the Type and Condition of Road Surfaces on the Exhaust Emissions and Fuel Consumption in the Transport of Timber

by Andrzej Ziółkowski, Paweł Fuć, Piotr Lijewski, Maciej Bednarek, Aleks Jagielski, Władysław Kusiak and Joanna Igielska-Kalwat

Energies 2023, 16(21), 7257; https://doi.org/10.3390/en16217257 - 25 Oct 2023

Cited by 2 | Viewed by 1744

Abstract

Owing to society’s growing ecological awareness, researchers and car manufacturers have increasingly been focusing on the adverse impact of transport on the environment. Many scientific publications have been published addressing the influence of a variety of factors on the exhaust emissions generated by [...] Read more.

Owing to society’s growing ecological awareness, researchers and car manufacturers have increasingly been focusing on the adverse impact of transport on the environment. Many scientific publications have been published addressing the influence of a variety of factors on the exhaust emissions generated by vehicles and machinery. In this paper, the authors present an analysis of the exhaust emissions of components such as CO, THC, and NO_x in relation to the type and condition of the road surface. The analysis was performed on a heavy-duty truck designed for carriage of timber. The investigations were carried out with the use of the PEMS equipment (portable emission measurement system) on bitumen-paved roads and unpaved forest access roads. The portable measurement system allowed for an accurate determination of the influence of the road conditions on the operating parameters of the vehicle powertrain and its exhaust emissions. Additionally, the authors present the influence of the type of road surface on the vehicle fuel consumption calculated based on the carbon balance method. Full article

(This article belongs to the Special Issue CO₂ Emissions from Vehicles (Volume II))

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19 pages, 3389 KiB

Open AccessEditor’s ChoiceArticle

Hydrothermal but Not Mechanical Pretreatment of Wastewater Algae Enhanced Anaerobic Digestion Energy Balance due to Improved Biomass Disintegration and Methane Production Kinetics

by Pavlo Bohutskyi, Duc Phan, Ruth E. Spierling and Trygve J. Lundquist

Energies 2023, 16(20), 7146; https://doi.org/10.3390/en16207146 - 19 Oct 2023

Cited by 2 | Viewed by 1183

Abstract

This study used pilot-scale high-rate algae ponds to assess algal–bacteria biomass productivity and wastewater nutrient removal as well as the impact of mechanical and hydrothermal pretreatments on biomass disintegration, methane production kinetics, and anaerobic digestion (AD) energy balance. Mechanical pretreatment had a minor [...] Read more.

This study used pilot-scale high-rate algae ponds to assess algal–bacteria biomass productivity and wastewater nutrient removal as well as the impact of mechanical and hydrothermal pretreatments on biomass disintegration, methane production kinetics, and anaerobic digestion (AD) energy balance. Mechanical pretreatment had a minor effect on biomass disintegration and methane production. By contrast, hydrothermal pretreatment significantly reduced particle size and increased the solubilized organic matter content by 3.5 times. The methane yield and production rate increased by 20–55% and 20–85%, respectively, with the highest values achieved after pretreatment at 121 °C for 60 min. While the 1st-order and pseudo-1st-order reaction equation models fitted methane production from untreated biomass best (R² > 0.993), the modified Gompertz sigmoidal-type model provided a superior fit for hydrothermally pretreated algae (R² ≥ 0.99). The AD energy balance revealed that hydrothermal pretreatment improved the total energy output by 25–40%, with the highest values for volume-specific and mass-specific total energy outputs reaching 0.23 kW per digester m³ and 2.3 MW per ton of biomass volatile solids. Additionally, net energy recovery (energy output per biomass HHV) increased from 20% for untreated algae to 32–34% for hydrothermally pretreated algae, resulting in net energy ratio and net energy efficiency of 2.14 and 68%, respectively. Full article

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19 pages, 5226 KiB

Open AccessEditor’s ChoiceArticle

Multi-Scale Seismic Measurements for Site Characterization and CO₂ Monitoring in an Enhanced Oil Recovery/Carbon Capture, Utilization, and Sequestration Project, Farnsworth Field, Texas

by George El-kaseeh and Kevin L. McCormack

Energies 2023, 16(20), 7159; https://doi.org/10.3390/en16207159 - 19 Oct 2023

Viewed by 1108

Abstract

To address the challenges of climate change, significantly more geologic carbon sequestration projects are beginning. The characterization of the subsurface and the migration of the plume of supercritical carbon dioxide are two elements of carbon sequestration that can be addressed through the use [...] Read more.

To address the challenges of climate change, significantly more geologic carbon sequestration projects are beginning. The characterization of the subsurface and the migration of the plume of supercritical carbon dioxide are two elements of carbon sequestration that can be addressed through the use of the available seismic methods in the oil and gas industry. In an enhanced oil recovery site in Farnsworth, TX, we employed three separate seismic techniques. The three-dimensional (3D) surface seismic survey required significant planning, design, and processing, but produces both a better understanding of the subsurface structure and a three-dimensional velocity model, which is essential for the second technique, a timelapse vertical seismic profile, and the third technique, cross-well seismic tomography. The timelapse 3D Vertical Seismic Profile (3D VSP) revealed both significant changes in the reservoir between the second and third surveys and geo-bodies that may represent the extent of the underground carbon dioxide. The asymmetry of the primary geo-body may indicate the preferential migration of the carbon dioxide. The third technique, cross-well seismic tomography, suggested a strong correlation between the well logs and the tomographic velocities, but did not observe changes in the injection interval. Full article

(This article belongs to the Special Issue Forecasting CO₂ Sequestration with Enhanced Oil Recovery II)

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19 pages, 761 KiB

Open AccessEditor’s ChoiceArticle

A Stochastic Model of Anomalously Fast Transport of Heat Energy in Crystalline Bodies

by Łukasz Stępień and Zbigniew A. Łagodowski

Energies 2023, 16(20), 7117; https://doi.org/10.3390/en16207117 - 17 Oct 2023

Viewed by 823

Abstract

In this work, a new method for constructing the infinite-dimensional Ornstein–Uhlenbeck stochastic process is introduced. The constructed process is used to perturb the harmonic system in order to model anomalously fast heat transport in one-dimensional nanomaterials. The introduced method made it possible to [...] Read more.

In this work, a new method for constructing the infinite-dimensional Ornstein–Uhlenbeck stochastic process is introduced. The constructed process is used to perturb the harmonic system in order to model anomalously fast heat transport in one-dimensional nanomaterials. The introduced method made it possible to obtain a transition probability function that allows for a different approach to the analysis of equations with such a disturbance. This creates the opportunity to relax assumptions about temporal correlations for such a process, which may lead to a qualitatively different model of energy transport through vibrations of the crystal lattice and, as a result, to obtain the superdiffusion equation on a macroscopic scale with an order of the fractional Laplacian different from the value of 3/4 obtained so far in stochastic models. Simulations confirming these predictions are presented and discussed. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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14 pages, 1345 KiB

Open AccessEditor’s ChoiceArticle

Optimizing Energy Efficiency of Dielectric Materials’ Electrodischarge Dispersion as One Sustainable Development Green Trend

by Antonina Malyushevskaya, Serhii Petrychenko, Krzysztof Przystupa, Olena Mitryasova, Michał Majka and Orest Kochan

Energies 2023, 16(20), 7098; https://doi.org/10.3390/en16207098 - 15 Oct 2023

Viewed by 1378

Abstract

Increasing the energy efficiency of production processes is closely related to minimizing the impact on the environment and is one of the priorities of the concept of sustainable development. Electric discharge is an effective tool for multilevel grinding of non-metallic materials in various [...] Read more.

Increasing the energy efficiency of production processes is closely related to minimizing the impact on the environment and is one of the priorities of the concept of sustainable development. Electric discharge is an effective tool for multilevel grinding of non-metallic materials in various working fluids and obtaining coarse and fine suspensions. We introduce the technique for calculating the electrotechnological parameters necessary for energy-efficient electric discharge dispersion. This technique considers the strength characteristics of the crushed material (dispersed phase) and the electrical conductivity of the working fluid (dispersed medium). It is also essential to consider the energy stored in the capacitor bank, the energy criterion, the critical value of the working fluid’s electrical strength, the radius of the high-voltage electrode point, and the distance from the discharge channel axis to the disintegration object. All this allows obtaining a given granulometric composition of the dispersed phase with minimal energy consumption. Experiments confirmed the validity of the proposed calculation technique. We obtained the water-brown coal suspension with a given dispersion two times faster and consumed four times less energy in comparison with the known methods that did not take into account the electrical conductivity of the working liquid and the mechanical strength of the crushed material. Full article

(This article belongs to the Special Issue Emerging Topics in Future Energy Materials)

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15 pages, 1867 KiB

Open AccessEditor’s ChoiceArticle

Limitations Imposed Using an Iodide/Triiodide Redox Couple in Solar-Powered Electrochromic Devices

by George Syrrokostas, Sarantis Tsamoglou and George Leftheriotis

Energies 2023, 16(20), 7084; https://doi.org/10.3390/en16207084 - 13 Oct 2023

Viewed by 1059

Abstract

In the present study, an iodide/triiodide (I⁻/I₃⁻) redox couple is used in hybrid electrochromic devices (ECDs), and the effects of the applied bias potential and bias time on device performance are studied. An applied bias potential [...] Read more.

In the present study, an iodide/triiodide (I⁻/I₃⁻) redox couple is used in hybrid electrochromic devices (ECDs), and the effects of the applied bias potential and bias time on device performance are studied. An applied bias potential of ~1 V is sufficient to achieve an initial contrast ratio of 8:1 in less than 5 min. Increasing both the bias potential and bias time results in an enhancement in loss reactions at the WO₃/electrolyte interface, rather than improving optical performance. Moreover, long-term performance depends on the testing procedure (regularly cycling or after storage), while the formation of iodine (I₂) decreases the initial transparency of the ECDs and affects their overall performance. However, its formation cannot be avoided, even without cycling the ECDs, and the restoration of the optical performance can take place only when the electrolyte is replaced with a fresh one. Finally, a new methodology is applied for calculating the loss current, and a suggestion is made to avoid a common mistake in calculating the coloration efficiency of these hybrid ECDs. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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