Stochastic Load Forecasts for the Evolving Electrical Distribution System
Open-Winding Permanent Magnet Synchronous Generator for Renewable Energy—A Review
Irradiation Analysis of Tensile Membrane Structures for Building-Integrated Photovoltaics
Low-Cost MPPT Strategy and Protection Circuit Applied to an Ayanz Wind Turbine with Screw Blades

Journal Description

Energies

Energies is a peer-reviewed, open access journal of related scientific research, technology development, engineering policy, and management studies related to the general field of energy, from technologies of energy supply, conversion, dispatch, and final use to the physical and chemical processes behind such technologies. Energies is published semimonthly online by MDPI. The European Biomass Industry Association (EUBIA), Association of European Renewable Energy Research Centres (EUREC), Institute for Chemical Processing of Coal (IChPW), International Society for Porous Media (InterPore), CYTED and others are affiliated with Energies and their members receive a discount on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Ei Compendex, RePEc, Inspec, CAPlus / SciFinder, and other databases.
Journal Rank: CiteScore - Q1 (Engineering (miscellaneous))
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 15.7 days after submission; acceptance to publication is undertaken in 2.9 days (median values for papers published in this journal in the first half of 2023).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Sections: published in 41 topical sections.
Testimonials: See what our editors and authors say about Energies.
Companion journals for Energies include: Fuels, Gases, Nanoenergy Advances and Solar.

Impact Factor: 3.2 (2022); 5-Year Impact Factor: 3.3 (2022)

Imprint Information Journal Flyer Open Access ISSN: 1996-1073

Latest Articles

24 pages, 6417 KiB

Open AccessArticle

A New Methodology for Determination of Layered Injection Allocation in Highly Deviated Wells Drilled in Low-Permeability Reservoirs

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Energies 2023, 16(23), 7764; https://doi.org/10.3390/en16237764 (registering DOI) - 24 Nov 2023

Abstract

During the water injection development process of highly deviated wells in low-permeability reservoirs, the water flooding distance between different layers of the same oil and water well is different due to the deviation of the well. In addition, the heterogeneity of low-permeability reservoirs is strong, and the water absorption capacity between layers is very different. This results in poor effectiveness of commonly used layered injection methods. Some highly deviated wells have premature water breakthroughs after layered water injection, which affects the development effect of the water flooding reservoirs. Therefore, based on the analysis and research of the existing layered injection allocation method and sand body connectivity evaluation method, considering the influence of sand body connectivity, the real displacement distance of highly deviated wells, reservoir physical properties, and other factors, a new methodology for determination of layered injection allocation in highly deviated wells drilled in low-permeability reservoirs is proposed. In this method, the vertical superposition and lateral contact relationship of a single sand body are determined using three methods: sand body configuration identification, seepage unit identification, and single sand body boundary identification. The connectivity coefficient, transition coefficient, and connectivity degree coefficient are introduced to quantitatively evaluate the connectivity of sand bodies and judge the connectivity relationship between single sand bodies. The correlation formula is obtained using the linear regression of the fracture length and ground fluid volume, and the real displacement distance of each layer in highly deviated wells is obtained. The calculation formula of the layered injection allocation is established by analyzing the important factors affecting the layered injection allocation, and a reasonable layered injection allocation is obtained. The calculation parameters of this method are fully considered, the required parameters are easy to obtain, and the practicability is strong. It can provide a method reference for the policy adjustment of layered water injection technology in similar water injection development reservoirs. Full article

(This article belongs to the Topic Petroleum and Gas Engineering)

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23 pages, 5273 KiB

Open AccessArticle

Zero-Voltage-Switching Analysis Model of the Triple-Active-Bridge Converter

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Energies 2023, 16(23), 7763; https://doi.org/10.3390/en16237763 - 24 Nov 2023

Abstract

This study aims to analyze the zero-voltage-switching (ZVS) region of a Triple-Active-Bridge (TAB) converter with five degrees of freedom. A TAB converter is an isolated converter derived from a dual-active-bridge (DAB) converter and composed of three full bridges (FBs) coupled to three winding transformers. To reduce the switching loss of the 12 active switches that compose 3 FBs, the ZVS operation is essential. However, owing to the numerous operation modes derived by five-phase shift ratios, ZVS analysis is complicated, particularly in the time domain. Therefore, this study presents the ZVS analysis model of the TAB converter based on the generalized harmonic approximation (GHA). Through the GHA of a TAB converter, the proposed model consists of unified formulas applicable to all operating ranges of the converter. Unified formulas consider all parameters, such as series inductance, port voltage, parasitic capacitance, transformer voltage, and turn ratio. In the proposed model, the ZVS area is confirmed using five-phase ratios with voltage modulation ratios as variables and verified using MATLAB and experiments. Full article

(This article belongs to the Special Issue Advanced DC-DC Power Converters and Switching Converters II)

16 pages, 2438 KiB

Open AccessArticle

Pilot Protection of a Distribution Network with Distributed Generators Based on 5G and Dynamic Time Warping Considering Cosine Transform

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Energies 2023, 16(23), 7762; https://doi.org/10.3390/en16237762 - 24 Nov 2023

Abstract

The application of 5G-based communication for pilot protection in a distribution network with distributed generators is becoming increasingly widespread, but the existence of a 5G communication transmission data delay adversely affects the rapidity and reliability of the pilot protection based on the principle of the traditional dynamic time warping distance (DTW) algorithm. Therefore, to address this problem, and according to the difference in fault currents between distributed generators and synchronous machines, a new scheme of pilot protection based on the principle of an improved DTW is proposed. The scheme firstly performs cosine transform on the fault current sequence, and then it normalizes the DTW value. Finally, the proposed scheme is verified via simulation. The simulation results show that, compared with the traditional DTW, the proposed algorithm has better anti-delay characteristics and a stronger anti-interference ability, and the scheme can quickly and reliably identify in-zone and out-of-area faults with strong noise resistance. Further, the action times for a single-phase ground fault, two-phase ground fault, two-phase-to-phase fault, and three-phase short-circuit fault were reduced by 2.9 ms, 4.54 ms, 5.81 ms, and 5.89 ms, respectively. In addition, it is also sui for a distribution network with a high wind and photovoltaic penetration rate. Full article

(This article belongs to the Topic Power System Protection)

15 pages, 2432 KiB

Open AccessArticle

Coordinated Planning of Power Systems under Uncertain Characteristics Based on the Multilinear Monte Carlo Method

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Energies 2023, 16(23), 7761; https://doi.org/10.3390/en16237761 - 24 Nov 2023

Abstract

The randomness of the power supply side and the load side of comprehensive energy systems is increasingly prominent. It is very difficult to meet demand through traditional planning methods. To solve this problem, this paper explores the coordinated planning of a power system under uncertain characteristics using the multilinear Monte Carlo method. The uncertain characteristic model and probability density function of the system’s power supply side and load side are established. Taking the optimal operating cost and the maximum wind power consumption as the system planning objectives, a system coordination planning scheme is established, and it is solved by multilinear Monte Carlo simulation. The superiority of this method is verified by taking the modified IEEE 39-bus test system as an example. This method can provide a reference for system planning. Full article

(This article belongs to the Special Issue State-of-the-Art Research in Advanced Materials for Energy Storage Applications)

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27 pages, 2131 KiB

Open AccessReview

Trends and Evolution of the GIS-Based Photovoltaic Potential Calculation

Sebastiano Anselmo

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Maria Ferrara

Energies 2023, 16(23), 7760; https://doi.org/10.3390/en16237760 - 24 Nov 2023

Abstract

In the current framework of energy transition, renewable energy production has gained a renewed relevance. A set of 75 papers was selected from the existing literature and critically analyzed to understand the main inputs and tools used to calculate solar energy and derive theoretical photovoltaic production based on geographic information systems (GISs). A heterogeneous scenario for solar energy estimation emerged from the analysis, with a prevalence of 2.5D tools—mainly ArcGIS and QGIS—whose calculation is refined chiefly by inputting weather data from databases. On the other hand, despite some minor changes, the formula for calculating the photovoltaic potential is widely acknowledged and includes solar energy, exploitable surface, performance ratio, and panel efficiency. While sectorial studies—targeting a specific component of the calculation—are sound, the comprehensive ones are generally problematic due to excessive simplification of some parts. Moreover, validation is often lacking or, when present, only partial. The research on the topic is in constant evolution, increasingly moving towards purely 3D models and refining the estimation to include the time component—both in terms of life cycle and variations between days and seasons. Full article

(This article belongs to the Special Issue Emerging Trends in Energy and Environmental Design Integrating New Services and Tools for Smart Cities and Smart Buildings)

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11 pages, 1502 KiB

Open AccessArticle

Enhancing Water Retention, Transport, and Conductivity Performance in Fuel Cell Applications: Nafion-Based Nanocomposite Membranes with Organomodified Graphene Oxide Nanoplatelets

Muhammad Habib Ur Rehman

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Energies 2023, 16(23), 7759; https://doi.org/10.3390/en16237759 - 24 Nov 2023

Abstract

The synergistic combination of Nafion and sulfonated graphene oxide (GOsulf) in nanocomposite membranes emerged as a promising strategy for advancing proton exchange membrane fuel cell (PEMFC) technology. In the pursuit of elucidating the effect of GOsulf introduction on transport properties and electrochemical performance of Nafion, this work provides a systematic study combining swelling tests, water release tests, ¹H NMR characterization, and Electrochemical Impedance Spectroscopy (EIS) investigation. The incorporation of organomodified GO nanolayers alters the distribution of water molecules within the hydrophilic domains of Nafion and produces a considerable increase in the “bound-water” fraction. This increases its water retention capability while ensuring very high diffusivity even under high temperatures, i.e., 1.5 × 10⁻⁵ cm² s⁻¹ at 130 °C. These peculiar features enable Naf-GOsulf to successfully operate under a dehydrating environment, yielding a proton conductivity of 44.9 mS cm⁻¹ at 30% RH. Full article

(This article belongs to the Special Issue Hydrogen-Based Energy Systems for Sustainable Transportation)

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22 pages, 4841 KiB

Open AccessArticle

Addressing Challenges in Delivering Sustainable Rural Water Provision Using Solar Water Pumping in Malawi: A Stakeholder Analysis

Esther Phiri

Paul N. Rowley

and

Richard E. Blanchard

Energies 2023, 16(23), 7758; https://doi.org/10.3390/en16237758 - 24 Nov 2023

Abstract

Despite the presence of relatively high insolation, solar photovoltaic water pumping (SWP) is rarely used for water provision in Malawi. Current methods of water abstraction are labour-intensive and have low discharge rates. A stakeholder analysis was carried out to evaluate the role, responsibilities, and challenges faced by individuals, communities, and organisations involved in developing SWP systems. Analysis of data collected via semi-structured interviews with stakeholders from government departments, public and private organisations, entrepreneurs, non-governmental organisations, and microfinance organisations shows that the national government should provide an enabling environment for other actors to deliver SWP projects. Further, this study reveals diverse interlinked challenges in delivering sustainable water and energy services related to policies, monitoring, coordination, financing, human resources, information and awareness, stakeholder malfeasance, political interference, and flawed community management. The impacts of these challenges result in inadequate water service provision resulting from access inequality, non-functionality, substandard installations, reliance on donations, substandard renewable energy products, and slow technology uptake. The results of this study imply that, given appropriate finance and management frameworks, effective coordination, enforcement of product and installation standards, and awareness and sensitisation of communities to SWP, significantly improved access to drinking and irrigation water for the rural population of Malawi and other countries in sub-Saharan Africa can be achieved. Full article

(This article belongs to the Special Issue Advances in Photovoltaic Solar Energy II)

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18 pages, 1792 KiB

Open AccessReview

Comparison of Technical and Operational Conditions of Traditional and Modern Charcoal Kilns: A Case Study in Italy

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Energies 2023, 16(23), 7757; https://doi.org/10.3390/en16237757 - 24 Nov 2023

Abstract

The global charcoal trade is steadily growing, with high-income countries importing significant quantities of this material from regions where its production is often associated with severe environmental issues, including forest overexploitation, illegal logging, and environmental pollution. Promoting local charcoal production in high-income countries is crucial to addressing these challenges. In this study, we have chosen to focus on the European context, specifically emphasizing Italy as a case study. Our study aimed to comprehensively compare five distinct charcoal production systems, including both traditional and modern solutions, with a specific focus on evaluating the quality of the resulting charcoal. Additionally, improvements were evaluated to enhance production efficiency. Traditional systems cannot satisfy production requests, resulting in inefficiencies in manpower, costs, times, and yield. Conversely, recent innovations consider mobile and stationary kiln prototypes. Mobile kilns offer flexibility and cost savings but require operator expertise, limit automation, and have long cycles. In contrast, stationary systems operate continuously, increasing productivity and efficiency, despite higher investment costs. Notably, charcoal quality showed minimal differences. These findings highlighted the potential of new technologies to enhance efficiency, reduce cost and environmental impact, and promote sustainable charcoal production. Full article

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22 pages, 9410 KiB

Open AccessArticle

Study of Thermal Inertia in the Subsoil Adjacent to a Civil Engineering Laboratory for a Ground-Coupled Heat Exchanger

Raúl Antonio Gutiérrez-Durán

Luciano. A. Cervantes

Dagoberto López López

Juan Peralta-Jaramillo

Emerita Delgado-Plaza

Guido Abril-Macias

Pablo Limon-Leyva

and

Ian Sosa-Tinoco

Energies 2023, 16(23), 7756; https://doi.org/10.3390/en16237756 - 24 Nov 2023

Abstract

This document presents a study of thermal inertia in the subsoil adjacent to the Civil Engineering laboratory of the Technological Institute of Sonora (ITSON) in the south of Sonora, Mexico, in service of the development of a solution proposal of a ground-coupled air heat exchanger for the cooling months. The research was divided into three phases: first, the monitoring of temperature in 10 layers of the ground; second, the analysis of thermal ground properties; and last, the design and simulation of a ground-coupled air heat exchanger. The objectives were to determine the variation in the thermal inertia of the soil with depth and over time and to determine the optimum depth for a ground-coupled heat exchanger system. The second objective was to develop a design proposal for a ground-coupled heat exchanger for the university laboratory. We found that the optimum depth is 3.0 m in a soil with high-compressibility clay with 21% humidity and 0.152 W/mK of thermal conductivity. However, the proposed design identified the best depth for the cooling system as 3 m considering a ground-coupled heat exchanger for a volume of 222.2 m³, corresponding to the volume of the classrooms of the building. With this design, the approach was to reduce the temperature by at least 10 °C on the hottest day (41 °C) of the year studied. We concluded that with this kind of system, the climate of the building studied could reduce the thermal load of active AC systems and reduce the energy load by 59%. Full article

(This article belongs to the Special Issue Renewable Energy Systems for Sustainable Buildings)

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17 pages, 7141 KiB

Open AccessArticle

Performance Evaluation of a Steam Ejector Considering Non-Equilibrium Condensation in Supersonic Flows

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Energies 2023, 16(23), 7755; https://doi.org/10.3390/en16237755 - 24 Nov 2023

Abstract

The present study established an experimental system of steam ejector refrigeration to evaluate the effect of the operating parameters, such as pressure on the diffuser wall and primary and secondary fluid, on the performance and efficiency of the ejector. The model validation of numerical methods was carried out against the experimental data, while the numerical simulation was conducted by utilizing computational fluid dynamics modeling to analyze the internal flow of the ejector. The results indicated that the escalation of the primary steam pressure in the choking position increased the Mach number and entrainment ratio as the flow area of the secondary fluid remained constant. The optimization studies show that the entrainment ratio was maximum when the primary steam pressure was 0.36 MPa. While the pressure was inordinate, the expansion core increased in size and further compressed the flow area of the secondary fluid, hence reducing the entrainment ratio. Subject to the influence of the normal shockwave, the change in back pressure did not alter the entrainment ratio before the critical back pressure. In contrast, the ejector no longer produces the normal shockwave after the critical back pressure; the entrainment ratio, therefore, was reduced with the increase in back pressure. Full article

(This article belongs to the Topic Advanced Heat and Mass Transfer Technologies)

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15 pages, 3125 KiB

Open AccessArticle

A Communication Encryption-Based Distributed Cooperative Control for Distributed Generators in Microgrids under FDI Attacks

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Energies 2023, 16(23), 7754; https://doi.org/10.3390/en16237754 - 24 Nov 2023

Abstract

To alleviate the hassle of false data injection (FDI) attacks on distributed generators (DGs) in microgrids, a communication encryption-based distributed cooperative control is proposed in this paper. Compared to the conventional distributed control strategies, the proposed control scheme is simpler with much less complex evaluation mechanism by upgrading the secondary control to a second-order control based on the finite-time control theory while combining an encryption strategy. The proposed algorithm provides constant injections to eliminate the impact of FDI attacks based on a robust communication system. The effectiveness and high efficiency of the proposed control scheme is validated in an IEEE 34 Node Test Feeder system with six DGs as a microgrid cyber-physical system (CPS) under different FDI attacks. Full article

(This article belongs to the Special Issue Cyber Security in Microgrids and Smart Grids)

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21 pages, 3000 KiB

Open AccessReview

Municipal Solid Waste Generation Trend and Bioenergy Recovery Potential: A Review

James Darmey

Julius Cudjoe Ahiekpor

Satyanarayana Narra

Osei-Wusu Achaw

and

Herbert Fiifi Ansah

Energies 2023, 16(23), 7753; https://doi.org/10.3390/en16237753 - 24 Nov 2023

Abstract

Finding sustainable solutions to the increasing waste generation in Ghana has received a lot of attention in recent years. Through several waste-to-energy processes, the energy potential of municipal solid waste has recently witnessed significant technological advancements. The Renewable Energy Master Plan has projected the production of about 122 MWp from waste-to-energy installations by 2030 in Ghana. To help policymakers and engineers achieve national goals, this paper reviews the waste generation in Ghana estimated from 2010 to 2030 and the status of various bioenergy technologies in Ghana. This paper further estimates the energy recovery potential of municipal solid waste in Ghana under incineration, anaerobic digestion, and landfill gas recovery technologies. The review establishes that, by 2030, municipal solid waste generation will increase by 123% of the 2023 quantities and may produce 1484.25 MW of installed electricity capacity and 13,002.03 GWh per year, which would amount to nearly 56% of Ghana’s 2030 renewable energy target. Additionally, it was determined that anaerobic digestion, incineration, and landfill gas recovery technologies, when properly developed, will add 105.33 MW, 301.4 MW, and 377.31 MW of installed electrical capacity, respectively, to Ghana’s energy mix in 2028. Full article

(This article belongs to the Special Issue Conversion and Utilization of Solid Wastes and Biomass into Fuels including Green Hydrogen)

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14 pages, 8420 KiB

Open AccessArticle

Experimental Study on the Improvement of the Film Cooling Effectiveness of Various Modified Configurations Based on a Fan-Shaped Film Cooling Hole on a Flat Plate

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Energies 2023, 16(23), 7752; https://doi.org/10.3390/en16237752 - 24 Nov 2023

Abstract

Modern gas turbines have evolved by increasing the turbine inlet temperature (TIT) to improve performance. This development has led to a demand for cooling techniques. Among these, the film cooling, which involves injecting compressed air through holes on the turbine surface, is a prominent cooling technique used to protect the turbine surface. In this study, a comparative analysis is conducted between the conventional fan-shaped film cooling hole, primarily used in film cooling techniques, and modified shapes achieved by altering the geometry of the film cooling hole based on a fan-shaped hole to assess and compare the cooling performance on a flat plate surface. The adiabatic film cooling effectiveness was measured for three film cooling holes, the Baseline of a 7-7-7 fan-shaped film cooling hole, namely, Staircase, which had a double-step at the hole exit, and Compound Expansion, which had an additional expanded flow path at the hole leading edge. The used measurement technique was the pressure-sensitive paint (PSP) technique, using nitrogen gas as the foreign gas, and experiments were conducted at a density ratio of 1.0 and blowing ratios ranging from 0.5 to 2.0. The results reveal that the modified holes featured wider lateral expansion at the hole exits, resulting in a broader distribution of the cooling effectiveness in the lateral direction compared to the Baseline. The Staircase shows a better performance, although an overall cooling effectiveness trend similar to that of the Baseline. Furthermore, the Compound Expansion demonstrates an enhancement in the cooling performance with an increased blowing ratio, notably achieving nearly double the cooling effectiveness compared to that of the Baseline at a blowing ratio of 2.0. Full article

(This article belongs to the Section J1: Heat and Mass Transfer)

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22 pages, 1115 KiB

Open AccessArticle

Modified Genetic Algorithm for the Profit-Based Unit Commitment Problem in Competitive Electricity Market

Lucas Santiago Nepomuceno

Layon Mescolin de Oliveira

Ivo Chaves da Silva Junior

Edimar José de Oliveira

and

Arthur Neves de Paula

Energies 2023, 16(23), 7751; https://doi.org/10.3390/en16237751 - 24 Nov 2023

Abstract

This article proposes a solution to the Profit-Based Unit Commitment (PBUC) problem to maximize the profit of a power generation company that owns thermal units and compressed air energy storage (CAES) systems, considering the Day-Ahead market. The proposed methodology is more realistic as it considers a mixed-integer nonlinear formulation of the PBUC. The problem is solved through two stages, with Stage 1 dedicated to obtaining the operational state of the generating units (On or Off) and the operation mode of the storage system (energy exchange: charging, discharging, idle). Stage 2 determines the dispatch of power from the thermoelectric units and the energy exchange in the storage system. The analysis of the system consisting of 20 thermoelectric units and three storage systems shows the efficiency of the proposed method in making decisions for the power generation company and is therefore promising for real-world applications. Full article

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

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21 pages, 2030 KiB

Open AccessReview

Research Progress on Aging Prediction Methods for Fuel Cells: Mechanism, Methods, and Evaluation Criteria

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Energies 2023, 16(23), 7750; https://doi.org/10.3390/en16237750 - 24 Nov 2023

Abstract

Due to the non-renewable nature and pollution associated with fossil fuels, there is widespread research into alternative energy sources. As a novel energy device, a proton exchange membrane fuel cell (PEMFC) is considered a promising candidate for transportation due to its advantages, including zero carbon emissions, low noise, and high energy density. However, the commercialization of fuel cells faces a significant challenge related to aging and performance degradation during operation. In order to comprehensively address the issue of fuel cell aging and performance decline, this paper provides a detailed review of aging mechanisms and influencing factors from the perspectives of both the PEMFC system and the stack. On this basis, this paper offers targeted solutions to degradation issues stemming from various aging factors and presents research on aging prediction methods to proactively mitigate aging-related problems. Furthermore, to enhance prediction accuracy, this paper categorizes and analyzes the degradation index and accuracy evaluation criteria commonly employed in the existing fuel cell aging research. The results indicate that specific factors leading to aging-related failures are often addressed via targeted solving methods, corresponding to specific degradation indexes. The significance of this study lies in the following aspects: (1) investigating the aging factors in fuel cells and elucidating the multiple aging mechanisms occurring within fuel cells; (2) proposing preventive measures, solutions, and aging prediction methods tailored to address fuel cell aging issues comprehensively, thereby mitigating potential harm; and (3) summarizing the degradation index and accuracy evaluation standards for aging prediction, offering new perspectives for resolving fuel cell aging problems. Full article

(This article belongs to the Special Issue Artificial Intelligence in Prognostics and Health Management of Renewable Energy System)

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14 pages, 2797 KiB

Open AccessArticle

Analysis of the Deposition of Pollutants on the Surface of Photovoltaic Modules

Janusz Teneta

Mirosław Janowski

and

Karolina Bender

Energies 2023, 16(23), 7749; https://doi.org/10.3390/en16237749 - 24 Nov 2023

Abstract

This article presents the results of an experiment to measure the mass of contaminants naturally deposited on the surface of photovoltaic modules. Six types of PV modules included in the installation located on the roof of the C3 building (AGH campus, Krakow, Poland) were tested. More than 120 contamination samples were collected during the experiment, which lasted from 23 March to 15 June 2022. Detailed analysis showed a clear relationship between the tilt angle of the photovoltaic modules and the amount of contamination accumulating on them. The impact of the backsheet color and the way the module was mounted (vertical or horizontal) on the amount of dirt deposited on a given module was also recorded. Because the experiment lasted for many weeks, it was possible to investigate the intensity of the contamination build-up over the following weeks (in the absence of module cleaning) and the effect of precipitation on the module self-cleaning. During one measurement, a layer of contamination with a normalized mass of 181 mg/m² was found to reduce PV module peak power by almost 4%. Full article

(This article belongs to the Special Issue Integration of Distributed Energy Resources (DERs))

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21 pages, 7852 KiB

Open AccessArticle

The Energy Retrofit Impact in Public Buildings: A Numerical Cross-Check Supported by Real Consumption Data

and

Eugenia Rossi di Schio

Energies 2023, 16(23), 7748; https://doi.org/10.3390/en16237748 - 24 Nov 2023

Abstract

In the framework of reducing carbon dioxide emissions and energy consumption, the energy retrofit of existing buildings plays a significant role and is often supported by numerical analyses of the planned activities and expected results. This study analyses a public building (a kindergarten) located in Bialystok (Poland) and aims to determine the building’s energy performance prior to and after thermal modernization. The building was examined by employing two different software packages, Audytor OZC 7.0 Pro and Trnsys 18. The thermal efficiency improvement applied to the renovated building in Bialystok was also analyzed by virtually locating the building in Bologna (Italy). Moreover, a comfort analysis focused on the classrooms of the kindergarten was carried out employing Trnsys. As a novelty, in the analysis, particular attention is paid to ventilation losses and to the influence of envelope elements properties on the building energy demand. The results arising from analyses were compared to real consumption data for the heating season. The results obtained from the two software programs display excellent agreement, and they also match the real consumption data if the heating demand is considered, while some differences arise when the cooling demand is considered. Full article

(This article belongs to the Special Issue Transformation of Energy Markets: Description, Modeling of Functioning Mechanisms and Determining Development Trends – Second Edition)

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23 pages, 6345 KiB

Open AccessReview

Grounding and Isolation Requirements in DC Microgrids: Overview and Critical Analysis

Mohammadreza Azizi

Oleksandr Husev

Oleksandr Veligorskyi

Saeed Rahimpour

and

Carlos Roncero-Clemente

Energies 2023, 16(23), 7747; https://doi.org/10.3390/en16237747 - 24 Nov 2023

Abstract

DC microgrids, along with existing AC grids, are a future trend in energy distribution systems. At the same time, many related issues are still undefined and unsolved. In particular, uncertainty prevails in isolation requirements between AC grids and novel microgrids as well as in the grounding approaches. This paper presents a critical technical analysis and an overview of possible grounding approaches in DC systems and the feasibility of avoiding isolation between AC and DC grids. Full article

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

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21 pages, 12254 KiB

Open AccessArticle

The Design of Water Loop Facility for Supporting the WCLL Breeding Blanket Technology and Safety

Pietro Alessandro Di Maio

Pietro Agostini

and

Alessandro Del Nevo

Energies 2023, 16(23), 7746; https://doi.org/10.3390/en16237746 - 24 Nov 2023

Abstract

The WCLL Breeding Blanket of DEMO and the Test Blanket Module (TBM) of ITER require accurate R&D activities, i.e., concept validation at a relevant scale and safety demonstrations. In view of this, the strategic objective of the Water Loop (WL) facility, belonging to the W-HYDRA experimental platform planned at C.R. Brasimone of ENEA, is twofold: to conduct R&D activities for the WCLL BB to validate design performances and to increase the technical maturity level for selection and validation phases, as well as to support the ITER WCLL Test Blanket System program. Basically, the Water Loop facility will have the capability to investigate the design features and performances of scaled-down or portions of breeding blanket components, as well as full-scale TBM mock-ups. It is a large-/medium-scale water coolant plant that will provide water coolant at high pressure and temperature. It is composed by single-phase primary (designed at 18.5 MPa and 350 °C) and secondary (designed at 2.5 MPa and 220 °C) systems thermally connected with a two-phase tertiary loop acting as an ultimate heat sink (designed at 6 bar and 80 °C). The primary loop has two main sources of power: an electrical heater up to about 1 MWe, installed in the cold side, downstream of the pump and upstream of the test section, and an electron beam gun acting as a heat flux generator. The WL has unique features and is designed as a multi-purpose facility capable of being coupled with the LIFUS5/Mod4 facility to study PbLi/water reaction at a large scale. This paper presents the status of the Water Loop facility, highlighting objectives, design features, and the analyses performed. Full article

(This article belongs to the Special Issue Water Coolant Lithium Lead Breeding Blanket and Test Blanket Module: Design and R&D Activities in 2022)

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12 pages, 10015 KiB

Open AccessArticle

Experimental Investigation of Thermal Properties of Frozen Tap, Demineralized, and Sea Water

Jelena Bošnjak

Mišo Jurčević

Natalia Bodrožić Ćoko

and

Sandro Nižetić

Energies 2023, 16(23), 7745; https://doi.org/10.3390/en16237745 - 24 Nov 2023

Abstract

This paper reports an experimental investigation of the thermal properties of frozen tap, demineralized, and sea water. The presented research assists in a better understanding of the thermal properties of ice and the processes within it and contributes regarding the generation of novel experimental data. The thermal conductivity was measured in a range from −14 °C to −33 °C using the Transient Plane Source (TPS) method. Ice blocks were placed in an expanded polystyrene box in the freezer, which is where the measurements took place. The thermal conductivity of the tap water ice was observed to vary in a range from 1.915 ± 0.005 Wm⁻¹K⁻¹ at −14 °C to 2.060 ± 0.004 Wm⁻¹K⁻¹ at −33 °C. The values obtained for the ice made of demineralized water differed by less than 10%. The thermal conductivity of the sea ice was shown to be more temperature dependent, with the values ranging from 1.262 ± 0.005 Wm⁻¹K⁻¹ at −14 °C to 1.970 Wm⁻¹K⁻¹ ± 0.004 at −33 °C. A noticeable fall in the thermal conductivity of the sea ice was observed in the temperature range from −26 °C to −19 °C. A possible reason for this could be the increased precipitation of salt in that temperature range. Measurements of thermal diffusivity displayed similar trends as those of thermal conductivity. Specific volumetric heat capacity was indirectly calculated. Full article

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