Energies

20 pages, 2989 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Microgrid Control through Genetic Predictive Control: Integrating Genetic Algorithms with Model Predictive Control for Improved Non-Linearity and Non-Convexity Handling

by Muhammed Cavus and Adib Allahham

Energies 2024, 17(17), 4458; https://doi.org/10.3390/en17174458 - 5 Sep 2024

Cited by 1 | Viewed by 614

Abstract

Microgrid (MG) control is crucial for efficient, reliable, and sustainable energy management in distributed energy systems. Genetic Algorithm-based energy management systems (GA-EMS) can optimally control MGs by solving complex, non-linear, and non-convex problems but may struggle with real-time application due to their computational [...] Read more.

Microgrid (MG) control is crucial for efficient, reliable, and sustainable energy management in distributed energy systems. Genetic Algorithm-based energy management systems (GA-EMS) can optimally control MGs by solving complex, non-linear, and non-convex problems but may struggle with real-time application due to their computational demands. Model Predictive Control (MPC)-based EMS, which predicts future behaviour to ensure optimal performance, usually depends on linear models. This paper introduces a novel Genetic Predictive Control (GPC) method that combines a GA and MPC to enhance resource allocation, balance multiple objectives, and adapt dynamically to changing conditions. Integrating GAs with MPC improves the handling of non-linearities and non-convexity, resulting in more accurate and effective control. Comparative analysis reveals that GPC significantly reduces excess power production, improves resource allocation, and balances cost, emissions, and power efficiency. For example, in the Mutation–Random Selection scenario, GPC reduced excess power to 76.0 W compared to 87.0 W with GA; in the Crossover-Elitism scenario, GPC achieved a lower daily cost of USD 113.94 versus the GA’s USD 127.80 and reduced carbon emissions to 52.83 kg CO2e compared to the GA’s 69.71 kg CO2e. While MPC optimises a weighted sum of objectives, setting appropriate weights can be difficult and may lead to non-convex problems. GAs offer multi-objective optimisation, providing Pareto-optimal solutions. GPC maintains optimal performance by forecasting future load demands and adjusting control actions dynamically. Although GPC can sometimes result in higher costs, such as USD 113.94 compared to USD 131.90 in the Crossover–Random Selection scenario, it achieves a better balance among various metrics, proving cost-effective in the long term. By reducing excess power and emissions, GPC promotes economic savings and sustainability. These findings highlight GPC’s potential as a versatile, efficient, and environmentally beneficial tool for power generation systems. Full article

(This article belongs to the Special Issue Renewable Energy System Technologies: 2nd Edition)

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35 pages, 2701 KiB

Open AccessEditor’s ChoiceReview

AI-Driven Innovations in Building Energy Management Systems: A Review of Potential Applications and Energy Savings

by Dalia Mohammed Talat Ebrahim Ali, Violeta Motuzienė and Rasa Džiugaitė-Tumėnienė

Energies 2024, 17(17), 4277; https://doi.org/10.3390/en17174277 - 27 Aug 2024

Cited by 2 | Viewed by 3131

Abstract

Despite the tightening of energy performance standards for buildings in various countries and the increased use of efficient and renewable energy technologies, it is clear that the sector needs to change more rapidly to meet the Net Zero Emissions (NZE) scenario by 2050. [...] Read more.

Despite the tightening of energy performance standards for buildings in various countries and the increased use of efficient and renewable energy technologies, it is clear that the sector needs to change more rapidly to meet the Net Zero Emissions (NZE) scenario by 2050. One of the problems that have been analyzed intensively in recent years is that buildings in operation use much more energy than they were designed to. This problem, known as the energy performance gap, is found in many countries and buildings and is often attributed to the poor management of building energy systems. The application of Artificial Intelligence (AI) to Building Energy Management Systems (BEMS) has untapped potential to address this problem and lead to more sustainable buildings. This paper reviews different AI-based models that have been proposed for different applications and different buildings with the intention to reduce energy consumption. It compares the performance of the different AI-based models evaluated in the reviewed papers by presenting the accuracy and error rates of model performance and identifies where the greatest potential for energy savings could be achieved, and to what extent. The review showed that offices have the greatest potential for energy savings (up to 37%) when they employ AI models for HVAC control and optimization. In residential and educational buildings, the lower intelligence of the existing BEMS results in smaller energy savings (up to 23% and 21%, respectively). Full article

(This article belongs to the Special Issue Building Energy Audits-Diagnosis and Retrofitting towards Decarbonization and Sustainable Cities II)

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18 pages, 340 KiB

Open AccessEditor’s ChoiceArticle

Renewable Energy Transition and the Paris Agreement: How Governance Quality Makes a Difference?

by Olfa Berrich, Fereshteh Mafakheri and Halim Dabbou

Energies 2024, 17(17), 4238; https://doi.org/10.3390/en17174238 - 25 Aug 2024

Viewed by 1151

Abstract

This paper investigates whether the Paris Agreement affects renewable energy deployment and how institutional quality moderates this relationship. According to a generalized method of moments estimation for panel data for both developed and developing countries over the period 2000–2022, the Paris Agreement positively [...] Read more.

This paper investigates whether the Paris Agreement affects renewable energy deployment and how institutional quality moderates this relationship. According to a generalized method of moments estimation for panel data for both developed and developing countries over the period 2000–2022, the Paris Agreement positively influences renewable energy deployment, suggesting that countries are promoting renewable energy to align with institutional expectations to maintain their reputations. The results further show that governance quality is the main determinant of renewable energy deployment. However, the moderating role of governance underscores the less-pronounced impact of the Paris Agreement on countries with high governance indicators, suggesting that these countries may have shifted their focus toward other avenues of climate management beyond the deployment of renewable energy. Furthermore, there is strong evidence of the relationship between forest area, CO₂ emission, trade openness, domestic credit, and renewable energy deployment. The results are robust with the use of a dynamic panel threshold model. Full article

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

26 pages, 1197 KiB

Open AccessEditor’s ChoiceReview

Revolution in Renewables: Integration of Green Hydrogen for a Sustainable Future

by Jimiao Zhang and Jie Li

Energies 2024, 17(16), 4148; https://doi.org/10.3390/en17164148 - 21 Aug 2024

Cited by 3 | Viewed by 2176

Abstract

In recent years, global efforts towards a future with sustainable energy have intensified the development of renewable energy sources (RESs) such as offshore wind, solar photovoltaics (PVs), hydro, and geothermal. Concurrently, green hydrogen, produced via water electrolysis using these RESs, has been recognized [...] Read more.

In recent years, global efforts towards a future with sustainable energy have intensified the development of renewable energy sources (RESs) such as offshore wind, solar photovoltaics (PVs), hydro, and geothermal. Concurrently, green hydrogen, produced via water electrolysis using these RESs, has been recognized as a promising solution to decarbonizing traditionally hard-to-abate sectors. Furthermore, hydrogen storage provides a long-duration energy storage approach to managing the intermittency of RESs, which ensures a reliable and stable electricity supply and supports electric grid operations with ancillary services like frequency and voltage regulation. Despite significant progress, the hydrogen economy remains nascent, with ongoing developments and persistent uncertainties in economic, technological, and regulatory aspects. This paper provides a comprehensive review of the green hydrogen value chain, encompassing production, transportation logistics, storage methodologies, and end-use applications, while identifying key research gaps. Particular emphasis is placed on the integration of green hydrogen into both grid-connected and islanded systems, with a focus on operational strategies to enhance grid resilience and efficiency over both the long and short terms. Moreover, this paper draws on global case studies from pioneering green hydrogen projects to inform strategies that can accelerate the adoption and large-scale deployment of green hydrogen technologies across diverse sectors and geographies. Full article

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

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15 pages, 742 KiB

Open AccessEditor’s ChoiceArticle

Key SDG7 Factors Shaping the Future of Clean Coal Technologies: Analysis of Trends and Prospects in Poland

by Aurelia Rybak, Aleksandra Rybak, Jarosław Joostberens and Spas D. Kolev

Energies 2024, 17(16), 4133; https://doi.org/10.3390/en17164133 - 20 Aug 2024

Cited by 1 | Viewed by 844

Abstract

This article presents the results of an analysis aimed at verifying the relationship between the implementation of SDG Goal 7 and the use of clean coal technologies in Poland. Clean coal technologies in the United Nations plans will constitute a crucial element of [...] Read more.

This article presents the results of an analysis aimed at verifying the relationship between the implementation of SDG Goal 7 and the use of clean coal technologies in Poland. Clean coal technologies in the United Nations plans will constitute a crucial element of the strategy for sustainable development in the energy context. They are intended to be one of the tools for building an energy system based on renewable energy sources, constituting a bridge that enables the transition of Poland’s energy system from coal to renewable energy sources. To identify whether this relationship exists, the Autoregressive Moving Average with Exogenous Input (ARMAX) model was used. The structure of the model, its correctness, and its accuracy were confirmed using information criteria; statistical tests such as Dickey-Fuller, Doornik-Hansen, Durbin-Watson, and Breusch-Pagan; and measures of prediction accuracy such as MAPE, MAE, and RMSE. The explanatory variables were the Objective 7 indicators adopted by Eurostat. Before being introduced to the ARMAX model, they were standardized using the Compound Annual Growth Rate (CAGR) indicator. The analysis made it possible to indicate which of the explanatory variables has the greatest impact on the development of clean coal technologies in Poland, to determine a synthetic CAGR measure for all the explanatory variables, and to compare the results obtained with the indicator determined by the United Nations. Full article

(This article belongs to the Collection Board Members’ Collection Series: Clean Coal Extraction and Using)

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28 pages, 16028 KiB

Open AccessEditor’s ChoiceArticle

Open-Source Internet of Things-Based Supervisory Control and Data Acquisition System for Photovoltaic Monitoring and Control Using HTTP and TCP/IP Protocols

by Wajahat Khalid, Mohsin Jamil, Ashraf Ali Khan and Qasim Awais

Energies 2024, 17(16), 4083; https://doi.org/10.3390/en17164083 - 16 Aug 2024

Cited by 1 | Viewed by 4314

Abstract

This study presents a cost-effective IoT-based Supervisory Control and Data Acquisition system for the real-time monitoring and control of photovoltaic systems in a rural Pakistani community. The system utilizes the Blynk platform with Arduino Nano, GSM SIM800L, and ESP-32 microcontrollers. The key components [...] Read more.

This study presents a cost-effective IoT-based Supervisory Control and Data Acquisition system for the real-time monitoring and control of photovoltaic systems in a rural Pakistani community. The system utilizes the Blynk platform with Arduino Nano, GSM SIM800L, and ESP-32 microcontrollers. The key components include a ZMPT101B voltage sensor, ACS712 current sensors, and a Maximum Power Point Tracking module for optimizing power output. The system operates over both Global System for Mobile Communications and Wi-Fi networks, employing universal asynchronous receiver–transmitter serial communication and using the transmission control protocol/Internet protocol and hypertext transfer protocol for data exchange. Testing showed that the system consumes only 3.462 W of power, making it highly efficient. With an implementation cost of CAD 35.52, it offers an affordable solution for rural areas. The system achieved an average data transmission latency of less than 2 s over Wi-Fi and less than 5 s over GSM, ensuring timely data updates and control. The Blynk 2.0 app provides data retention capabilities, allowing users to access historical data for performance analysis and optimization. This open-source SCADA system demonstrates significant potential for improving efficiency and user engagement in renewable energy management, offering a scalable solution for global applications. Full article

(This article belongs to the Special Issue Simulation Modelling and Analysis of a Renewable Energy System, Volume II)

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17 pages, 4125 KiB

Open AccessEditor’s ChoiceArticle

High Current Density Operation of a Proton Exchange Membrane Fuel Cell with Varying Inlet Relative Humidity—A Modeling Study

by Wei Liu, Anders Christian Olesen, Vincenzo Liso and Torsten Berning

Energies 2024, 17(16), 4077; https://doi.org/10.3390/en17164077 - 16 Aug 2024

Cited by 1 | Viewed by 1129

Abstract

This paper focuses on proton exchange membrane fuel cell (PEMFC) operation at current densities in the order of 6 A/cm². Such high current densities are conceivable when the traditional carbon fiber papers are replaced with perforated metal plates as the gas [...] Read more.

This paper focuses on proton exchange membrane fuel cell (PEMFC) operation at current densities in the order of 6 A/cm². Such high current densities are conceivable when the traditional carbon fiber papers are replaced with perforated metal plates as the gas diffusion layer to enhance waste heat removal, and at the same time the relative humidity inside the fuel cell is kept below 100% by applying appropriate operating conditions as was found in previous one-dimensional modeling work. In the current paper, we applied a three-dimensional, multi-phase computational fluid dynamics model based on Ansys-CFX to obtain additional insight into the underlying physics. The calculated pressure drops are in very good agreement with previous one-dimensional modeling work, and the current densities in all case studies are in the order of 5–6 A/cm², but different from the previous one-dimensional study, the results suggest that the relative humidity is very close to 100% throughout the entire channel length when the inlet relative humidity is 100%, ensuring best hydration cell conditions and hence best performance. Importantly, the model results suggest that fuel cell performance at a high current density in conjunction with relatively low stoichiometric flow ratios around 1.5–2 is possible. Full article

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

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16 pages, 4227 KiB

Open AccessEditor’s ChoiceArticle

Multi-Objective Sensitivity Analysis of a Wind Turbine Equipped with a Pumped Hydro Storage System Using a Reversible Hydraulic Machine

by Lorenzo Dambrosio and Stefano Pio Manzari

Energies 2024, 17(16), 4078; https://doi.org/10.3390/en17164078 - 16 Aug 2024

Cited by 1 | Viewed by 731

Abstract

A typical wind system captures wind energy and converts it into electricity, which is then converted to DC for battery storage using an AC/DC converter; an inverter then supplies AC electricity at the grid frequency. However, this solution involves losses in electronic components [...] Read more.

A typical wind system captures wind energy and converts it into electricity, which is then converted to DC for battery storage using an AC/DC converter; an inverter then supplies AC electricity at the grid frequency. However, this solution involves losses in electronic components and incurs costs and environmental impacts associated with battery storage. To address these issues, a different wind system layout configuration is considered, where the energy storage duties are assumed by a hydro storage system employing a reversible hydraulic pump (referred to as a Pump as Turbine). This solution utilises an elevated reservoir connected to the Pump as Turbine to compensate for fluctuations in wind and load; this approach offers lower costs, a longer lifespan, reduced maintenance, and a smaller waste management cost. This study focuses on a comprehensive sensitivity analysis of the new wind system power layout, considering multiple objectives. Specifically, the analysis targets the net change in the mass of water (potential energy) stored in the pumped hydro system, the captured wind energy, and the torque provided in hydraulic turbine mode. On the other hand, the design variables are represented by the Pump as Turbine-specific speed, the hydraulic system gearbox ratio, and the pump head. To assess how solutions are affected by random changes in wind speed and external load, the sensitivity analysis considers the multi-objective optimisation problem showing for both the wind speed and the external load a stochastic contribution. Full article

(This article belongs to the Special Issue Modern Technologies for Renewable Energy Development and Utilization: 3rd Edition)

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30 pages, 9019 KiB

Open AccessEditor’s ChoiceArticle

Modeling the Optimal Transition of an Urban Neighborhood towards an Energy Community and a Positive Energy District

by Diego Viesi, Gregorio Borelli, Silvia Ricciuti, Giovanni Pernigotto and Md Shahriar Mahbub

Energies 2024, 17(16), 4047; https://doi.org/10.3390/en17164047 - 15 Aug 2024

Viewed by 938

Abstract

Building renovation is a key initiative to promote energy efficiency, the integration of renewable energy sources (RESs), and a reduction in CO₂ emissions. Supporting these goals, emerging research is dedicated to energy communities and positive energy districts. In this work, an urban [...] Read more.

Building renovation is a key initiative to promote energy efficiency, the integration of renewable energy sources (RESs), and a reduction in CO₂ emissions. Supporting these goals, emerging research is dedicated to energy communities and positive energy districts. In this work, an urban neighborhood of six buildings in Trento (Italy) is considered. Firstly, the six buildings are modeled with the Urban Modeling Interface tool to evaluate the energy performances in 2024 and 2050, also accounting for the different climatic conditions for these two time periods. Energy demands for space heating, domestic hot water, space cooling, electricity, and transport are computed. Then, EnergyPLAN coupled with a multi-objective evolutionary algorithm is used to investigate 12 different energy decarbonization scenarios in 2024 and 2050 based on different boundaries for RESs, energy storage, hydrogen, energy system integration, and energy community incentives. Two conflicting objectives are considered: cost and CO₂ emission reductions. The results show, on the one hand, the key role of sector coupling technologies such as heat pumps and electric vehicles in exploiting local renewables and, on the other hand, the higher costs in introducing both electricity storage to approach complete decarbonization and hydrogen as an alternative strategy in the electricity, thermal, and transport sectors. As an example of the quantitative valuable finding of this work, in scenario S1 “all sectors and EC incentive” for the year 2024, a large reduction of 55% of CO₂ emissions with a modest increase of 11% of the total annual cost is identified along the Pareto front. Full article

(This article belongs to the Special Issue Advances in Waste Heat Recovery and Integrated Energy Systems)

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21 pages, 2184 KiB

Open AccessEditor’s ChoiceReview

A Review of Life Cycle Assessment (LCA) Studies for Hydrogen Production Technologies through Water Electrolysis: Recent Advances

by Negar Shaya and Simon Glöser-Chahoud

Energies 2024, 17(16), 3968; https://doi.org/10.3390/en17163968 - 10 Aug 2024

Cited by 1 | Viewed by 3078

Abstract

Climate change is a major concern for the sustainable development of global energy systems. Hydrogen produced through water electrolysis offers a crucial solution by storing and generating renewable energy with minimal environmental impact, thereby reducing carbon emissions in the energy sector. Our research [...] Read more.

Climate change is a major concern for the sustainable development of global energy systems. Hydrogen produced through water electrolysis offers a crucial solution by storing and generating renewable energy with minimal environmental impact, thereby reducing carbon emissions in the energy sector. Our research evaluates current hydrogen production technologies, such as alkaline water electrolysis (AWE), proton exchange membrane water electrolysis (PEMWE), solid oxide electrolysis (SOEC), and anion exchange membrane water electrolysis (AEMWE). We systematically review life cycle assessments (LCA) for these technologies, analyzing their environmental impacts and recent technological advancements. This study fills essential gaps by providing detailed LCAs for emerging technologies and evaluating their scalability and environmental footprints. Our analysis outlines the strengths and weaknesses of each technology, guiding future research and assisting stakeholders in making informed decisions about integrating hydrogen production into the global energy mix. Our approach highlights operational efficiencies and potential sustainability enhancements by employing comparative analyses and reviewing advancements in membrane technology and electrocatalysts. A significant finding is that PEMWE when integrated with renewable energy sources, offers rapid response capabilities that are vital for adaptive energy systems and reducing carbon footprints. Full article

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

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44 pages, 2928 KiB

Open AccessEditor’s ChoiceArticle

Exergy Analysis in Highly Hydrogen-Enriched Methane Fueled Spark-Ignition Engine at Diverse Equivalence Ratios via Two-Zone Quasi-Dimensional Modeling

by Dimitrios C. Rakopoulos, Constantine D. Rakopoulos, George M. Kosmadakis, Evangelos G. Giakoumis and Dimitrios C. Kyritsis

Energies 2024, 17(16), 3964; https://doi.org/10.3390/en17163964 - 9 Aug 2024

Viewed by 1151

Abstract

In the endeavor to accomplish a fully de-carbonized globe, sparkling interest is growing towards using natural gas (NG) having as vastly major component methane (CH₄). This has the lowest carbon/hydrogen atom ratio compared to other conventional fossil fuels used in engines [...] Read more.

In the endeavor to accomplish a fully de-carbonized globe, sparkling interest is growing towards using natural gas (NG) having as vastly major component methane (CH₄). This has the lowest carbon/hydrogen atom ratio compared to other conventional fossil fuels used in engines and power-plants hence mitigating carbon dioxide (CO₂) emissions. Given that using neat hydrogen (H₂) containing nil carbon still possesses several issues, blending CH₄ with H₂ constitutes a stepping-stone towards the ultimate goal of zero producing CO₂. In this context, the current work investigates the exergy terms development in high-speed spark-ignition engine (SI) fueled with various hydrogen/methane blends from neat CH₄ to 50% vol. fraction H₂, at equivalence ratios (EQR) from stoichiometric into the lean region. Experimental data available for that engine were used for validation from the first-law (energy) perspective plus emissions and cycle-by-cycle variations (CCV), using in-house, comprehensive, two-zone (unburned and burned), quasi-dimensional turbulent combustion model tracking tightly the flame-front pathway, developed and reported recently by authors. The latter is expanded to comprise exergy terms accompanying the energy outcomes, affording extra valuable information on judicious energy usage. The development in each zone, over the engine cycle, of various exergy terms accounting too for the reactive and diffusion components making up the chemical exergy is calculated and assessed. The correct calculation of species and temperature histories inside the burned zone subsequent to entrainment of fresh mixture from the unburned zone contributes to more exact computation, especially considering the H₂ percentage in the fuel blend modifying temperature-levels, which is key factor when the irreversibility is calculated from a balance comprising all rest exergy terms. Illustrative diagrams of the exergy terms in every zone and whole charge reveal the influence of H₂ and EQR values on exergy terms, furnishing thorough information. Concerning the joint content of both zones normalized exergy values over the engine cycle, the heat loss transfer exergy curves acquire higher values the higher the H₂ or EQR, the work transfer exergy curves acquire slightly higher values the higher the H₂ and slightly higher values the lower the EQR, and the irreversibility curves acquire lower values the higher the H₂ or EQR. This exergy approach can offer new reflection for the prospective research to advancing engines performance along judicious use of fully friendly ecological fuel as H₂. This extended and in-depth exergy analysis on the use of hydrogen in engines has not appeared in the literature. It can lead to undertaking corrective actions for the irreversibility, exergy losses, and chemical exergy, eventually increasing the knowledge of the SI engines science and technology for building smarter control devices when fueling the IC engines with H₂ fuel, which can prove to be game changer to attaining a clean energy environment transition. Full article

(This article belongs to the Special Issue Internal Combustion Engine Performance 2024)

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19 pages, 3142 KiB

Open AccessEditor’s ChoiceArticle

Dynamic Radiant Barrier for Modulating Heat Transfer and Reducing Building Energy Usage

by Tyler R. Stevens, Behzad Parsi, Rydge B. Mulford and Nathan B. Crane

Energies 2024, 17(16), 3959; https://doi.org/10.3390/en17163959 - 9 Aug 2024

Viewed by 1092

Abstract

Buildings consume significant energy, much of which is used for heating and cooling. Insulation reduces undesired heat transfer to save on heating and cooling energy usage. Radiant barriers are a type of insulation technology that reduces radiant heat absorbed by a structure. Applying [...] Read more.

Buildings consume significant energy, much of which is used for heating and cooling. Insulation reduces undesired heat transfer to save on heating and cooling energy usage. Radiant barriers are a type of insulation technology that reduces radiant heat absorbed by a structure. Applying radiant barriers to buildings reduces costs and improves both energy efficiency and occupant comfort. However, homes often have favorable thermal gradients that could also be used to reduce energy usage if the insulation properties were switched dynamically. This article introduces two dynamic radiant barriers intended for residential attics, which can switch between reflecting and transmitting states as needed. These radiant barriers are manufactured as a single deformable assembly using sheet materials and are compatible with various actuation mechanisms. The efficacy of these radiant barriers is reported based on a hotbox experiment and numerical calculations. The experimental results demonstrate that both proposed dynamic radiant barrier designs increase effective thermal resistance by factors of approximately 2 when comparing insulating to conducting states, and by approximately 4 when comparing the insulating state to the case without a radiant barrier. Additionally, the dynamic radiant barriers achieve heat flux reductions up to 41.9% in the insulating state compared to tests without a dynamic radiant barrier. Full article

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

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25 pages, 7602 KiB

Open AccessEditor’s ChoiceArticle

Enhancing Cyber-Physical Resiliency of Microgrid Control under Denial-of-Service Attack with Digital Twins

by Mahmoud S. Abdelrahman, Ibtissam Kharchouf, Hossam M. Hussein, Mustafa Esoofally and Osama A. Mohammed

Energies 2024, 17(16), 3927; https://doi.org/10.3390/en17163927 - 8 Aug 2024

Viewed by 1052

Abstract

Microgrids (MGs) are the new paradigm of decentralized networks of renewable energy sources, loads, and storage devices that can operate independently or in coordination with the primary grid, incorporating significant flexibility and supply reliability. To increase reliability, traditional individual MGs can be replaced [...] Read more.

Microgrids (MGs) are the new paradigm of decentralized networks of renewable energy sources, loads, and storage devices that can operate independently or in coordination with the primary grid, incorporating significant flexibility and supply reliability. To increase reliability, traditional individual MGs can be replaced by networked microgrids (NMGs), which are more dependable. However, when it comes to operation and control, they also pose challenges for cyber security and communication reliability. Denial of service (DoS) is a common danger to DC microgrids with advanced controllers that rely on active information exchanges and has been recorded as the most frequent cause of cyber incidents. It can disrupt data transmission, leading to ineffective control and system instability. This paper proposes digital twin (DT) technology as an integrated solution, with new, advanced analytics technology using machine learning and artificial intelligence to provide simulation capabilities to predict and estimate future states. By twinning the cyber-physical dynamics of NMGs using data-driven models, DoS attacks targeting cyber-layer agents will be detected and mitigated. A long short-term memory (LSTM) model data-driven digital twin approach for DoS attack detection and mitigation is implemented, tested, and evaluated. Full article

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

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17 pages, 5683 KiB

Open AccessEditor’s ChoiceArticle

Enhancing Lambda Measurement in Hydrogen-Fueled SI Engines through Virtual Sensor Implementation

by Federico Ricci, Massimiliano Avana and Francesco Mariani

Energies 2024, 17(16), 3932; https://doi.org/10.3390/en17163932 - 8 Aug 2024

Viewed by 994

Abstract

The automotive industry is increasingly challenged to develop cleaner, more efficient solutions to comply with stringent emission standards. Hydrogen (H₂)-powered internal combustion engines (ICEs) offer a promising alternative, with the potential to reduce carbon-based emissions and improve efficiency. However, hydrogen combustion [...] Read more.

The automotive industry is increasingly challenged to develop cleaner, more efficient solutions to comply with stringent emission standards. Hydrogen (H₂)-powered internal combustion engines (ICEs) offer a promising alternative, with the potential to reduce carbon-based emissions and improve efficiency. However, hydrogen combustion presents two main challenges related to the calibration process: emissions control and measurement of the air excess coefficient (λ). Traditional lambda sensors struggle with hydrogen’s combustion dynamics, leading to potential inefficiencies and increased pollutant emissions. Consequently, the determination of engine performance could also be compromised. This study explores the feasibility of using machine learning (ML) to replace physical lambda sensors with virtual ones in hydrogen-fueled ICEs. The research was conducted on a single-cylinder spark-ignition (SI) engine, collecting data across a range of air excess coefficients from 1.6 to 3.0. An advanced hybrid model combining long short-term memory (LSTM) networks and convolutional neural networks (CNNs) was developed and fine-tuned to accurately predict the air–fuel ratio; its predictive performance was compared to that obtained with the backpropagation (BP) architecture. The optimal configuration was identified through iterative experimentation, focusing on the neuron count, number of hidden layers, and input variables. The results demonstrate that the LSTM + 1DCNN model successfully converged without overfitting; it also showed better prediction ability in terms of accuracy and robustness when compared with the backpropagation approach. Full article

(This article belongs to the Section I2: Energy and Combustion Science)

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19 pages, 3940 KiB

Open AccessEditor’s ChoiceArticle

Double-Ligand [Fe/PNP/PP₃] and Their Hybrids [Fe/SiO₂@PNP/PP₃] as Catalysts for H₂-Production from HCOOH

by Marinos Theodorakopoulos, Maria Solakidou, Yiannis Deligiannakis and Maria Louloudi

Energies 2024, 17(16), 3934; https://doi.org/10.3390/en17163934 - 8 Aug 2024

Cited by 1 | Viewed by 992

Abstract

Two types of iron-based catalysts, [Fe/SiO₂@^iProPNP/PP3] and [Fe/SiO₂@^tBuPNP/PP3], for the dehydrogenation of formic acid (FADH), were synthesized. These catalysts were developed using a double-ligand approach combining a PNP ligand and a PP3 ligand, demonstrating functionality [...] Read more.

Two types of iron-based catalysts, [Fe/SiO₂@^iProPNP/PP3] and [Fe/SiO₂@^tBuPNP/PP3], for the dehydrogenation of formic acid (FADH), were synthesized. These catalysts were developed using a double-ligand approach combining a PNP ligand and a PP3 ligand, demonstrating functionality without the need for additional cocatalysts or additives. Furthermore, hybrid catalysts [Fe/SiO₂@^iProPNP/PP3] and [Fe/SiO₂@^tBuPNP/PP3] were created by covalently grafting PNP ligands onto SiO₂ particles. The hybrid [Fe/SiO₂@^iProPNP/PP3] exhibited enhanced recyclability, with turnover numbers (TONs) exceeding 74,000. In situ ATR-FTIR and UV-Vis spectroscopies were used to monitor the structure and dynamics of the catalysts under catalytic conditions, revealing the formation of active catalysts through the involvement of all components: [Fe (metal)/PNP (first ligand)/PP3 (second ligand)/FA (substrate)], which are crucial to FADH catalysis. An Arrhenius study revealed that the hybrid [Fe/SiO₂@^iProPNP/PP3] had a lower activation energy (E_a = 42.5 kJ/mol) compared to its homogeneous counterpart (E_a = 48.2 kJ/mol), indicating superior catalytic performance. Conversely, [Fe/SiO₂@^tBuPNP/PP3] showed an increased activation energy (E_a = 48.3 kJ/mol) compared to its homogeneous form (E_a = 46.4 kJ/mol). This study discusses the differing roles of ^tBuPNP and ^iProPNP in catalyst configuration, highlighting the potential of double-ligand catalysts to enhance the performance and recyclability of PNP ligands in FADH, offering significant implications for the development of efficient and reusable catalytic systems. Full article

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

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20 pages, 3316 KiB

Open AccessEditor’s ChoiceArticle

Life Cycle Assessment of Piezoelectric Devices Implemented in Wind Turbine Condition Monitoring Systems

by Rabie Aloui, Raoudha Gaha, Barbara Lafarge, Berk Celik and Caroline Verdari

Energies 2024, 17(16), 3928; https://doi.org/10.3390/en17163928 - 8 Aug 2024

Cited by 1 | Viewed by 3586

Abstract

Assessing the vibration signature produced by a rotating component of the wind turbine enables the identification of operational conditions and the detection of potential faults at an early stage. The main purpose is to enhance the sustainability of wind turbines while increasing the [...] Read more.

Assessing the vibration signature produced by a rotating component of the wind turbine enables the identification of operational conditions and the detection of potential faults at an early stage. The main purpose is to enhance the sustainability of wind turbines while increasing the lifespan and uptime of their operational systems. This vibration analysis is based on the processing of the signal provided by sensors, which often incorporates piezoelectric transducers. This paper evaluates the consequences of employing piezoelectric sensors used for vibration measurement on electrical machines integrated into wind turbines by conducting a life cycle assessment (LCA). The widespread use of piezoelectric materials is due to their high sensitivity to vibrations, although their selection is also influenced by regulatory restrictions. This research focuses on the environmental impact of piezoelectric accelerometers used commonly in condition monitoring systems. The collected literature data on the manufacturing processes are inputted into the LCA model which is powered by the Ecoinvent 3 database. The impact assessment is carried out using the European ILCD 2011 Midpoint+ method by calculating the unique scores of the selected impact categories. The results are presented and discussed in terms of environmental indicators, as well as ecological recommendations on the design. Full article

(This article belongs to the Special Issue Enhancing Energy Efficiency in Industry 4.0 for Sustainable Production, Smart Design and Manufacturing, Demand-Side Management, and Efficient Scheduling with Renewable Energy Sources)

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19 pages, 2052 KiB

Open AccessEditor’s ChoiceArticle

Investment in Offshore Wind Energy in Poland and Its Impact on Public Opinion

by Ewa Chomać-Pierzecka

Energies 2024, 17(16), 3912; https://doi.org/10.3390/en17163912 - 8 Aug 2024

Cited by 1 | Viewed by 1167

Abstract

The availability of energy-bearing resources is a key determinant of the development strategy of the world’s energy systems. In the case of Poland, the wind energy potential of the Baltic Sea provides the basis for the development of offshore wind energy in the [...] Read more.

The availability of energy-bearing resources is a key determinant of the development strategy of the world’s energy systems. In the case of Poland, the wind energy potential of the Baltic Sea provides the basis for the development of offshore wind energy in the country. The processes of transforming solutions towards green technologies require appropriate legislation, significant financial outlays, as well as public support for this dimension of activities. The latter strand requires continuous measurement to dynamically model the energy transition strategy. In the author’s opinion, the available literature does not sufficiently explain this theme in relation to Polish conditions. Hence, it was considered reasonable to investigate the impact of offshore wind energy development in Poland on public opinion in a selected region of Poland, in order to diagnose the current scale of support for the changes taking place, and to identify the main expectations and fears related to this activity, which was assumed as the main objective of the study. The added value of the survey is the analysis of changes in public opinion over time. The methodology used for the research was a study of the scientific literature, with analysis of the results of own and secondary research conducted in Poland. In terms of in-depth research, statistical survey techniques supported by the PQstat programme were used. The results of the survey confirmed significant public support in the surveyed area for offshore wind energy development in Poland (68%). The overall percentage of support for offshore development increased by 5% y/y. Economic considerations for the support of the activities in question with the potential vision of lowering energy prices in the domestic market were confirmed with a result of 65%. It was further confirmed that a key aspect of support for the offshore development strategy in the surveyed region of Poland is the potential for development of the region in relation to offshore farm investments, with a focus on the labour market, with indications of 53% for both themes. Interestingly, there was no concern in relation to the risk of landscape change in an undesirable direction in 2024. Full article

(This article belongs to the Special Issue Economic, Financial, and Social Aspects of Green Energy Transformation)

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14 pages, 1833 KiB

Open AccessEditor’s ChoiceArticle

A Nernst-Based Approach for Modeling of Lithium-Ion Batteries with Non-Flat Voltage Characteristics

by Athar Ahmad, Mario Iamarino and Antonio D’Angola

Energies 2024, 17(16), 3914; https://doi.org/10.3390/en17163914 - 8 Aug 2024

Viewed by 1213

Abstract

This paper presents an easy-to-implement model to predict the voltage in a class of Li-ion batteries characterized by non-flat, gradually decreasing voltage versus capacity. The main application is for the accurate estimation of the battery state of the charge, as in the energy [...] Read more.

This paper presents an easy-to-implement model to predict the voltage in a class of Li-ion batteries characterized by non-flat, gradually decreasing voltage versus capacity. The main application is for the accurate estimation of the battery state of the charge, as in the energy management systems of battery packs used in stationary and mobility applications. The model includes a limited number of parameters and is based on a simple equivalent circuit representation where an open circuit voltage source is connected in series with an equivalent resistance. The non-linear open circuit voltage is described using a Nernst-like term, and the model parameters are estimated based on the manufacturer discharge curves. The results show a good level of model accuracy in the case of three different commercial batteries considered by the study: Panasonic CGR18650AF, Panasonic NCR18650B and Tesla 4680. In particular, accurate description of the voltage curves versus the state of charge at different constant currents and during charging/discharging cycles is achieved. A possible model reduction is also addressed, and the effect of the equivalent internal resistance in improving the model predictions near fully depleted conditions is highlighted. Full article

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

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43 pages, 17688 KiB

Open AccessEditor’s ChoiceReview

Recent Advancements on Slot-Die Coating of Perovskite Solar Cells: The Lab-to-Fab Optimisation Process

by Vera C. M. Duarte and Luísa Andrade

Energies 2024, 17(16), 3896; https://doi.org/10.3390/en17163896 - 7 Aug 2024

Viewed by 1590

Abstract

Perovskite solar cells (PSCs) are the most rapidly advancing photovoltaic technology in terms of power conversion efficiency. An efficiency of 26.1% was achieved in a decade, which is on par with the efficiency of very mature silicon panels. However, PSC commercialisation is partly [...] Read more.

Perovskite solar cells (PSCs) are the most rapidly advancing photovoltaic technology in terms of power conversion efficiency. An efficiency of 26.1% was achieved in a decade, which is on par with the efficiency of very mature silicon panels. However, PSC commercialisation is partly hindered by the difficulty of scaling these devices without efficiency loss, mostly due to the increasing sheet resistance of the transparent conductive layer substrates and the nonuniformity of the layers when deposited across large areas. Therefore, it is crucial for the commercialisation of PSCs to implement easily scalable deposition processes with low material waste and compatibility with roll-to-roll (R2R) processes to reduce manufacturing costs. Slot-die coating can meet all these requirements, allowing for great uniformity over large areas. The most recent developments in PSC upscaling using slot-die coating as the main deposition process, along with its extension to the R2R process, are reviewed, including a thorough discussion of the slot-die coating process and the theory behind its operating limits. In fact, R2R coating is a very promising strategy for PSC industrialisation, since all processing steps use low-cost materials and scalable processes at temperatures lower than 120 °C, allowing the cost-effective and high-throughput production of PSC devices. Full article

(This article belongs to the Special Issue Advanced Technologies of Solar Cells)

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36 pages, 5097 KiB

Open AccessEditor’s ChoiceReview

A Review of Thermal Management and Heat Transfer of Lithium-Ion Batteries

by Liang Xu, Shanyi Wang, Lei Xi, Yunlong Li and Jianmin Gao

Energies 2024, 17(16), 3873; https://doi.org/10.3390/en17163873 - 6 Aug 2024

Cited by 3 | Viewed by 2837

Abstract

With the increasing demand for renewable energy worldwide, lithium-ion batteries are a major candidate for the energy shift due to their superior capabilities. However, the heat generated by these batteries during their operation can lead to serious safety issues and even fires and [...] Read more.

With the increasing demand for renewable energy worldwide, lithium-ion batteries are a major candidate for the energy shift due to their superior capabilities. However, the heat generated by these batteries during their operation can lead to serious safety issues and even fires and explosions if not managed effectively. Lithium-ion batteries also suffer from significant performance degradation at low temperatures, including reduced power output, a shorter cycle life, and reduced usable capacity. Deploying an effective battery thermal management system (BTMS) is crucial to address these obstacles and maintain stable battery operation within a safe temperature range. In this study, we review recent developments in the thermal management and heat transfer of Li-ion batteries to offer more effective, secure, and cost-effective solutions. We evaluate different technologies in BTMSs, such as air cooling, liquid cooling, phase change materials, heat pipes, external preheating, and internal preheating, discussing their advantages and disadvantages. Through comparative analyses of high-temperature cooling and low-temperature preheating, we highlight the research trends to inspire future researchers. According to the review of the literature, submerged liquid BTMS configurations show the greatest potential as a research focus to enhance thermal regulation in Li-ion batteries. In addition, there is considerable research potential in the innovation of air-based BTMSs, the optimization of liquid-based BTMSs, the coupling of heat pipes with PCMs, the integration of PCMs and liquid-cooled hybrid BTMSs, and the application of machine learning and topology optimization in BTMS design. The application of 3D printing in lithium-ion battery thermal management promises to enhance heat transfer efficiency and system adaptability through the design of innovative materials and structures, thereby improving the battery’s performance and safety. Full article

(This article belongs to the Special Issue Advanced Thermal Management Technologies and Heat Transfer)

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32 pages, 6774 KiB

Open AccessEditor’s ChoiceReview

A Comprehensive Review on the Hydrogen–Natural Gas–Diesel Tri-Fuel Engine Exhaust Emissions

by Hassan Sadah Muhssen, Máté Zöldy and Ákos Bereczky

Energies 2024, 17(15), 3862; https://doi.org/10.3390/en17153862 - 5 Aug 2024

Cited by 2 | Viewed by 867

Abstract

Natural gas (NG) is favored for transportation due to its availability and lower CO₂ emissions than fossil fuels, despite drawbacks like poor lean combustion ability and slow burning. According to a few recent studies, using hydrogen (H₂) alongside NG and [...] Read more.

Natural gas (NG) is favored for transportation due to its availability and lower CO₂ emissions than fossil fuels, despite drawbacks like poor lean combustion ability and slow burning. According to a few recent studies, using hydrogen (H₂) alongside NG and diesel in Tri-fuel mode addresses these drawbacks while enhancing efficiency and reducing emissions, making it a promising option for diesel engines. Due to the importance and novelty of this, the continuation of ongoing research, and insufficient literature studies on HNG–diesel engine emissions that are considered helpful to researchers, this research has been conducted. This review summarizes the recent research on the HNG–diesel Tri-fuel engines utilizing hydrogen-enriched natural gas (HNG). The research methodology involved summarizing the effect of engine design, operating conditions, fuel mixing ratios and supplying techniques on the CO, CO₂, NO_x and HC emissions separately. Previous studies show that using natural gas with diesel increases CO and HC emissions while decreasing NO_x and CO₂ compared to pure diesel. However, using hydrogen with diesel reduces CO, CO₂, and HC emissions but increases NO_x. On the other hand, HNG–diesel fuel mode effectively mitigates the disadvantages of using these fuels separately, resulting in decreased emissions of CO, CO₂, HC, and NO_x. The inclusion of hydrogen improves combustion efficiency, reduces ignition delay, and enhances heat release and in-cylinder pressure. Additionally, operational parameters such as engine power, speed, load, air–fuel ratio, compression ratio, and injection parameters directly affect emissions in HNG–diesel Tri-fuel engines. Overall, the Tri-fuel approach offers promising emissions benefits compared to using natural gas or hydrogen separately as dual-fuels. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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32 pages, 24406 KiB

Open AccessEditor’s ChoiceArticle

Photovoltaics Energy Potential in the Largest Greek Cities: Atmospheric and Urban Fabric Effects, Climatic Trends Influences and Socio-Economic Benefits

by Stavros Vigkos and Panagiotis G. Kosmopoulos

Energies 2024, 17(15), 3821; https://doi.org/10.3390/en17153821 - 2 Aug 2024

Viewed by 1597

Abstract

This comprehensive study explores the influence of aerosols and clouds on solar radiation in the urban environments of nine of Greece’s largest cities over the decade from 2014 to 2023. Utilizing a combination of Earth Observation data, radiative transfer models, and geographic information [...] Read more.

This comprehensive study explores the influence of aerosols and clouds on solar radiation in the urban environments of nine of Greece’s largest cities over the decade from 2014 to 2023. Utilizing a combination of Earth Observation data, radiative transfer models, and geographic information systems, the research undertook digital surface modeling and photovoltaic simulations. The study meticulously calculated the optimal rooftop areas for photovoltaic installation in these cities, contributing significantly to their energy adequacy and achieving a balance between daily electricity production and demand. Moreover, the research provides an in-depth analysis of energy and economic losses, while also highlighting the environmental benefits. These include a reduction in pollutant emissions and a decrease in the carbon footprint, aligning with the global shift towards local energy security and the transformation of urban areas into green, smart cities. The innovative methodology of this study, which leverages open access data, sets a strong foundation for future research in this field. It opens up possibilities for similar studies and has the potential to contribute to the creation of an updated, comprehensive solar potential map for continental Greece. This could be instrumental in climate change mitigation and adaptation strategies, thereby promoting sustainable urban development and environmental preservation. Full article

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

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38 pages, 2312 KiB

Open AccessEditor’s ChoiceReview

Hydrogen Purification Technologies in the Context of Its Utilization

by Anna Król, Monika Gajec, Jadwiga Holewa-Rataj, Ewa Kukulska-Zając and Mateusz Rataj

Energies 2024, 17(15), 3794; https://doi.org/10.3390/en17153794 - 1 Aug 2024

Viewed by 2199

Abstract

This publication explores current and prospective methods for hydrogen production and purification, with a strong emphasis on membrane-based technologies for purification and separation. This focus is justified by the ongoing shift towards renewable energy sources (RESs) in electricity generation, necessitating strategic changes to [...] Read more.

This publication explores current and prospective methods for hydrogen production and purification, with a strong emphasis on membrane-based technologies for purification and separation. This focus is justified by the ongoing shift towards renewable energy sources (RESs) in electricity generation, necessitating strategic changes to increase hydrogen utilization, particularly in the automotive, heavy road, and rail sectors, by 2025–2030. The adoption of hydrogen from RESs in the construction, energy, and industrial sectors (e.g., for process heat or fertilizer production) is also under consideration, driving the need for innovative production, separation, and purification methods. Historically, industrial-scale hydrogen has been predominantly derived from fossil fuels, but renewable sources such as electrolysis, biological, and thermal processes now offer alternatives with varying production efficiencies (0.06–80%) and gas compositions. Therefore, selecting appropriate separation and purification methods is critical based on specific usage requirements and the gas composition. Industrial-scale hydrogen purification commonly employs pressure swing adsorption (PSA) technologies, capable of achieving up to 99.99% purity. Cryogenic distillation is suitable for applications needing up to 95% purity. Membrane technologies, including polymer, metallic, and electrolytic membranes, have traditionally been limited to moderate volumes of pure gas production but are crucial for hydrogen purification and separation. This publication critically evaluates the potential of membrane technology for hydrogen separation, particularly in response to the anticipated rise in demand for RES-derived hydrogen, including from renewable feedstocks. Full article

(This article belongs to the Special Issue Advances in Hydrogen Energy IV)

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36 pages, 22665 KiB

Open AccessEditor’s ChoiceArticle

Analysis of the Year-Round Operation of Enhanced Natural Ventilation Systems under Transient Weather Conditions in Europe

by Rafał Andrzejczyk

Energies 2024, 17(15), 3795; https://doi.org/10.3390/en17153795 - 1 Aug 2024

Viewed by 813

Abstract

This study presents the potential of using a natural ventilation system integrated with different combinations of enhancement techniques. The focus was on the perspective of using such configurations of passive ventilation systems (PVSs) in buildings located in different European cities. This work presents [...] Read more.

This study presents the potential of using a natural ventilation system integrated with different combinations of enhancement techniques. The focus was on the perspective of using such configurations of passive ventilation systems (PVSs) in buildings located in different European cities. This work presents the results of obtaining the level of volumetric air flow rate for considering natural ventilation systems. Furthermore, the influences of local weather conditions (temperature, solar radiation, wind speed) were analyzed. Moreover, the year-round operation of all systems was presented. Also noted was the limitation of using PVSs based on the natural draft effect, additionally assisted by wind turbine ventilators in all European localizations. However, for the cities located in the northern part of Europe, it was confirmed that such a system can still meet minimum hygienic recommendations. It was also noted that a system additionally supported by a solar chimney is a much better solution. The best system was a PVS supported by a wind turbine ventilator and solar chimney integrated with PCM accumulation mass. The system should be additionally supported by waste heat from low-temperature sources. In the presented study, a high potential to reduce CO₂ emission from building stock by the recommended system is additionally highlighted. However, there is still a need to analyze the proposed solutions by additional field tests and experimental investigations. Full article

(This article belongs to the Special Issue Development of Distributed Energy Systems Based on Renewable Energy Sources—Current Status and Development Prospects)

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16 pages, 273 KiB

Open AccessEditor’s ChoiceArticle

The Threefold Role of the University in Fostering the Energy Transition: The Case of Bologna and Its Cesena Campus

by Andrea Boeri, Beatrice Turillazzi, Francesca Sabatini, Louise-Nour Sassenou and Gabriele Manella

Energies 2024, 17(15), 3751; https://doi.org/10.3390/en17153751 - 30 Jul 2024

Cited by 1 | Viewed by 863

Abstract

As acceleration toward the transition to a carbon-neutral energy production becomes an urgent imperative, universities are called to play a multifaceted role: to produce knowledge and cutting-edge research for the pursuit of energy transition; to transform infrastructures to promote circular economy practices and [...] Read more.

As acceleration toward the transition to a carbon-neutral energy production becomes an urgent imperative, universities are called to play a multifaceted role: to produce knowledge and cutting-edge research for the pursuit of energy transition; to transform infrastructures to promote circular economy practices and a more sustainable use of their building stock; and to promote energy citizenship through formal and informal education. The authors aim to move from these considerations to critically present some actions and programs in education, research, and campus operations in which the University of Bologna is engaged. The first part presents an overview of the role of universities in this transition, with a focus on the UI GreenMetric international standard for assessing the different dimensions of sustainability. In the core section, an empirical focus is provided on Bologna and its Cesena campus through three directions: the University’s multicampus sustainable strategy (campus operations), the relevant research–action projects on energy justice and the energy transition (research), and the EN-ACTION project to foster energy citizenship and behavioral change in students and citizens (education). This study concludes that the comprehensive approach of the University of Bologna in integrating sustainability into its operations, education, and research while fostering student engagement in energy citizenship, provides a replicable model for other institutions. It highlights the need for consistent and ongoing support to ensure the long-term impact and effectiveness of sustainability initiatives. The integration of social components and engagement with civil society is crucial for fostering a collective behavioral shift toward low-carbon systems, which can be further supported by interdisciplinary and transdisciplinary research approaches. Full article

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

25 pages, 5303 KiB

Open AccessEditor’s ChoiceArticle

Leveraging Pumped Storage Power Plants for Innovative Stability Enhancement of Weakly Interconnected Power Systems

by Antans Sauhats, Andrejs Utāns and Diāna Žalostība

Energies 2024, 17(15), 3754; https://doi.org/10.3390/en17153754 - 30 Jul 2024

Cited by 1 | Viewed by 967

Abstract

The hybrid AC/DC grid, based on a significant share of renewable energy sources, is gradually becoming an essential aspect of the modern energy system. The integration of intermittent renewable generators into contemporary energy systems is accompanied by the decommissioning of power plants containing [...] Read more.

The hybrid AC/DC grid, based on a significant share of renewable energy sources, is gradually becoming an essential aspect of the modern energy system. The integration of intermittent renewable generators into contemporary energy systems is accompanied by the decommissioning of power plants containing synchronous generators. Consequently, this leads to a reduction in system inertia and an increase in the risk of stability disruption. The abrupt disconnection of the primary generator or power line can result in an unanticipated mismatch between power generation and consumption. This discrepancy can trigger substantial and swiftly evolving alterations in power distribution, angular speed, load flow, and the frequency of generators. The risks of an energy system collapse can be mitigated through automation, enabling rapid adjustments to generation and load capacities, as well as power flows, in the electrical network. This article justifies the utilisation of a power control method for high-voltage power line interconnections. The technology of hydro storage power plants and measurements of voltage phasors are employed. The potential for easing power flow restrictions and realising substantial economic benefits is supported by the results obtained using simplified dynamic model of the Baltic power system and Nord Pool electricity market model. Full article

(This article belongs to the Special Issue Complex and Nonlinear Dynamics in Electrical Power and Energy Storage Systems: Analysis, Modelling and Control)

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25 pages, 4840 KiB

Open AccessEditor’s ChoiceArticle

Application of the Metalog Probability Distribution Family to Predict Energy Production by Photovoltaic Systems for the Purposes of Generating Green Hydrogen

by Arkadiusz Małek, Jacek Caban, Monika Stoma, Agnieszka Dudziak and Branislav Šarkan

Energies 2024, 17(15), 3729; https://doi.org/10.3390/en17153729 - 29 Jul 2024

Viewed by 922

Abstract

The article presents the application of the metalog family of probability distributions to predict the energy production of photovoltaic systems for the purpose of generating small amounts of green hydrogen in distributed systems. It can be used for transport purposes as well as [...] Read more.

The article presents the application of the metalog family of probability distributions to predict the energy production of photovoltaic systems for the purpose of generating small amounts of green hydrogen in distributed systems. It can be used for transport purposes as well as to generate energy and heat for housing purposes. The monthly and daily amounts of energy produced by a photovoltaic system with a peak power of 6.15 kWp were analyzed using traditional statistical methods and the metalog probability distribution family. On this basis, it is possible to calculate daily and monthly amounts of hydrogen produced with accuracy from the probability distribution. Probabilistic analysis of the instantaneous power generated by the photovoltaic system was used to determine the nominal power of the hydrogen electrolyzer. In order to use all the energy produced by the photovoltaic system to produce green hydrogen, the use of a stationary energy storage device was proposed and its energy capacity was determined. The calculations contained in the article can be used to design home green hydrogen production systems and support the climate and energy transformation of small companies with a hydrogen demand of up to ¾ kg/day. Full article

(This article belongs to the Special Issue Sustainable Development of Fuel Cells and Hydrogen Technologies)

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19 pages, 18784 KiB

Open AccessEditor’s ChoiceArticle

Robust Secondary Controller for Islanded Microgrids with Unexpected Electrical Partitions under Fault Conditions

by Evangelos E. Pompodakis, Georgios I. Orfanoudakis, Katsigiannis Yiannis and Emmanuel S. Karapidakis

Energies 2024, 17(15), 3727; https://doi.org/10.3390/en17153727 - 29 Jul 2024

Viewed by 798

Abstract

This paper proposes a sophisticated, fault-tolerant, and centralized secondary controller that is designed for inverter-based, islanded microgrids. The proposed controller enhances system resilience to unexpected network partitions, which typically occur due to the tripping of protective devices under fault conditions. In typical radially [...] Read more.

This paper proposes a sophisticated, fault-tolerant, and centralized secondary controller that is designed for inverter-based, islanded microgrids. The proposed controller enhances system resilience to unexpected network partitions, which typically occur due to the tripping of protective devices under fault conditions. In typical radially configured MGs, a line fault can cause protective devices to isolate the faulted line, thereby splitting the MG into two electrically independent sub-microgrids (SMGs), while retaining the existing communication and control framework. In contrast to traditional centralized and distributed secondary controllers, which often fail to restore the frequency to the nominal value (50 Hz) in split SMGs, the proposed controller exhibits exceptional performance. Through simulation studies on 6-bus and 13-bus islanded MG setups, the controller has not only demonstrated its ability to swiftly restore the nominal frequency in both SMGs within a few seconds (specifically 5 s), but also to ensure fair power distribution among the distributed generators (DGs) supplying the SMGs. This rapid frequency stabilization underscores the controller’s effectiveness in maintaining stable frequency levels immediately following a fault. In contrast, the use of traditional centralized and consensus controllers typically results in a frequency deviation of about 3 Hz from the nominal value in one of the SMGs during the microgrid’s partition. Full article

(This article belongs to the Special Issue Control of Renewable Energy Sources in Power Systems and Smart Grids: 2nd Edition)

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21 pages, 1741 KiB

Open AccessEditor’s ChoiceArticle

The Stabilization of a Nonlinear Permanent-Magnet- Synchronous-Generator-Based Wind Energy Conversion System via Coupling-Memory-Sampled Data Control with a Membership-Function-Dependent H_∞ Approach

by Anto Anbarasu Yesudhas, Seong Ryong Lee, Jae Hoon Jeong, Narayanan Govindasami and Young Hoon Joo

Energies 2024, 17(15), 3746; https://doi.org/10.3390/en17153746 - 29 Jul 2024

Cited by 2 | Viewed by 743

Abstract

This study presents the coupling-memory-sampled data control (CMSDC) design for the Takagi–Sugeno (T-S) fuzzy system that solves the stabilization issue of a surface-mounted permanent-magnet synchronous generator (PMSG)-based wind energy conversion system (WECS). A fuzzy CMSDC scheme that includes the sampled data control (SDC) [...] Read more.

This study presents the coupling-memory-sampled data control (CMSDC) design for the Takagi–Sugeno (T-S) fuzzy system that solves the stabilization issue of a surface-mounted permanent-magnet synchronous generator (PMSG)-based wind energy conversion system (WECS). A fuzzy CMSDC scheme that includes the sampled data control (SDC) and memory-sampled data control (MSDC) is designed by employing a Bernoulli distribution order. Meanwhile, the membership-function-dependent (MFD)

H_{\infty}

performance index is presented, mitigating the continuous-time fuzzy system’s disturbances. Then, by using the Lyapunov–Krasovskii functional with the MFD

H_{\infty}

performance index, the data of the sampling pattern, and a constant signal transmission delay, sufficient conditions are derived. These sufficient conditions are linear matrix inequalities (LMIs), ensuring the global asymptotic stability of a PMSG-based WECS under the designed control technique. The proposed method is demonstrated by a numerical simulation implemented on the PMSG-based WECS. Finally, Rossler’s system demonstrates the effectiveness and superiority of the proposed method. Full article

(This article belongs to the Section A3: Wind, Wave and Tidal Energy)

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19 pages, 1026 KiB

Open AccessEditor’s ChoiceArticle

Stochastic Optimal Strategies and Management of Electric Vehicles and Microgrids

by Faa-Jeng Lin, Su-Ying Lu, Ming-Che Hu and Yen-Haw Chen

Energies 2024, 17(15), 3726; https://doi.org/10.3390/en17153726 - 28 Jul 2024

Viewed by 1053

Abstract

This study combines the Nash–Cournot competition model and the stochastic optimization model to examine the impact of electric vehicle (EV) quantity fluctuations on microgrid operations, aiming to optimize energy usage in a competitive electricity market. Integrating distributed energy resources and bidirectional charging, microgrids [...] Read more.

This study combines the Nash–Cournot competition model and the stochastic optimization model to examine the impact of electric vehicle (EV) quantity fluctuations on microgrid operations, aiming to optimize energy usage in a competitive electricity market. Integrating distributed energy resources and bidirectional charging, microgrids offer a novel approach for energy optimization, aiding in renewable energy generation, peak demand management, and emission reduction. Empirical evidence highlights benefits in Taiwan’s electricity market and net-zero emissions target by 2050, with a case study demonstrating enhanced local renewable energy generation due to EVs and microgrid integration. As the number of EVs increases, electricity sales from microgrids decline, but electricity purchases remain stable. The degree of electricity liberalization also influences the supply and demand dynamics of the electricity market. Microgrids selling electricity only to the main grid increases total power consumption by 65.55 million MWh, reducing the market share of the state-owned utility (Taipower). Conversely, allowing retailers to purchase from microgrids increases total consumption by 30.87 million MWh with a slight market share decrease for Taipower. This study contributes to providing an adaptable and flexible general model for future studies to modify and expand based on different scenarios and variables to shape energy and environmental policies. Full article

(This article belongs to the Special Issue Research on Power System Control and Optimization)

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15 pages, 2795 KiB

Open AccessEditor’s ChoiceArticle

Electrochemical Performance of a Hybrid NiCo₂O₄@NiFelt Electrode at Different Operating Temperatures and Electrolyte pH

by Ataollah Niyati, Arianna Moranda, Pouya Beigzadeh Arough, Federico Maria Navarra and Ombretta Paladino

Energies 2024, 17(15), 3703; https://doi.org/10.3390/en17153703 - 26 Jul 2024

Viewed by 799

Abstract

Transition metals such as nickel and cobalt as an alternative to Pt and Pd can be used for oxygen evolution reactions (OERs) and hydrogen production reactions (HERs) in alkaline environments, facilitating green hydrogen production as a sustainable alternative to fossil fuels. In this [...] Read more.

Transition metals such as nickel and cobalt as an alternative to Pt and Pd can be used for oxygen evolution reactions (OERs) and hydrogen production reactions (HERs) in alkaline environments, facilitating green hydrogen production as a sustainable alternative to fossil fuels. In this study, an NiCo₂O₄ catalyst was produced by a sono-hydrothermal method using urea as a hydrolysis agent. The electrochemical performance of the catalyst-coated NiFelt electrode was evaluated at different KOH concentrations (0.25, 0.5, and 1 M) and four operating temperatures in the interval of 20–80 °C. The electrode characteristics were investigated via electrochemical spectroscopy (cyclic voltammetry, EIS, multistep chronopotentiometry, multistep chronoamperometry) using two different reference electrodes (Ag/AgCl and Hg/HgO), to obtain insight into the anodic and cathodic peaks. XRD, SEM, EDS, and TEM analyses confirmed the purity, structure, and nanoscale particle size (20–45 nm) of the NiCo₂O₄ catalyst. The electrode showed symmetric CV with Ag/AgCl, making this reference electrode more appropriate for capacitance measurements, while Hg/HgO proved advantageous for EIS in alkaline solutions due to reduced noise. The overpotential of the catalyst-coated NiFelt decreased by 108 mV at 10 mA/cm² compared to bare NiFelt, showing a good potential for its application in anion exchange membranes and alkaline electrolyzers at an industrial scale. Full article

(This article belongs to the Collection Advanced Materials for Energy Conversion and Storage Devices)

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17 pages, 1593 KiB

Open AccessEditor’s ChoiceArticle

An Analysis of Greenhouse Gas Emissions in Electrolysis for Certifying Clean Hydrogen

by Yunji Kim, Inhong Min, Jieun Lee and Heena Yang

Energies 2024, 17(15), 3698; https://doi.org/10.3390/en17153698 - 26 Jul 2024

Viewed by 975

Abstract

The drive for carbon neutrality has led to legislative measures targeting reduced greenhouse gas emissions across the transportation, construction, and industry sectors. Renewable energy sources, especially solar and wind power, play a pivotal role in this transition. However, their intermittent nature necessitates effective [...] Read more.

The drive for carbon neutrality has led to legislative measures targeting reduced greenhouse gas emissions across the transportation, construction, and industry sectors. Renewable energy sources, especially solar and wind power, play a pivotal role in this transition. However, their intermittent nature necessitates effective storage solutions. Green hydrogen and ammonia have gained attention for their potential to store renewable energy while producing minimal emissions. Despite their theoretical promise of zero greenhouse gas emissions during production, real-world emissions vary based on system configurations and lifecycle assessments, highlighting the need for detailed evaluations of their environmental impact. Therefore, in this study, calculations were performed for the actual amount of produced greenhouse gas emissions that are associated with the production of green hydrogen using electrolysis, from raw material extraction and processing to hydrogen production, with these assessed from well-to-gate emission estimates. Emissions were also evaluated based on various types of renewable energy sources in South Korea, as well as hydrogen production volumes, capacities, and types. Using these data, the following factors were examined in this study: carbon dioxide emissions from the manufacturing stage of electrolysis equipment production, the correlation between materials and carbon dioxide emissions, and process emissions. Current grades of clean hydrogen were verified, and the greenhouse gas reduction effects of green hydrogen were confirmed. These findings are significant against the backdrop of a country such as South Korea, where the proportion of renewable energy in total electricity production is very low at 5.51%. Based on the domestic greenhouse gas emission efficiency standard of 55 kWh/kgH₂, it was found that producing 1 kg of hydrogen emits 0.076 kg of carbon dioxide for hydropower, 0.283 kg for wind power, and 0.924 kg for solar power. The carbon dioxide emissions for AWE and PEM stacks were 8434 kg CO₂ and 3695 kg CO₂, respectively, demonstrating that an alkaline water electrolysis (AWE) system emits about 2.3 times more greenhouse gasses than a proton exchange membrane (PEM) system. This indicates that the total carbon dioxide emissions of green hydrogen are significantly influenced by the type of renewable energy and the type of electrolysis used. Full article

(This article belongs to the Special Issue Transformation to a Green Energy Economy—Challenge or Necessity)

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20 pages, 1108 KiB

Open AccessEditor’s ChoiceArticle

Local Energy Community to Support Hydrogen Production and Network Flexibility

by Massimiliano Ferrara, Fabio Mottola, Daniela Proto, Antonio Ricca and Maria Valenti

Energies 2024, 17(15), 3663; https://doi.org/10.3390/en17153663 - 25 Jul 2024

Cited by 1 | Viewed by 759

Abstract

This paper deals with the optimal scheduling of the resources of a renewable energy community, whose coordination is aimed at providing flexibility services to the electrical distribution network. The available resources are renewable generation units, battery energy storage systems, dispatchable loads, and power-to-hydrogen [...] Read more.

This paper deals with the optimal scheduling of the resources of a renewable energy community, whose coordination is aimed at providing flexibility services to the electrical distribution network. The available resources are renewable generation units, battery energy storage systems, dispatchable loads, and power-to-hydrogen systems. The main purposes behind the proposed strategy are enhancement of self-consumption and hydrogen production from local resources and the maximization of the economic benefits derived from both the selling of hydrogen and the subsidies given to the community for the shared energy. The proposed approach is formulated as an economic problem accounting for the perspectives of both community members and the distribution system operator. In more detail, a mixed-integer constrained non-linear optimization problem is formulated. Technical constraints related to the resources and the power flows in the electrical grid are considered. Numerical applications allow for verifying the effectiveness of the procedure. The results show that it is possible to increase self-consumption and the production of green hydrogen while providing flexibility services through the exploitation of community resources in terms of active and reactive power support. More specifically, the application of the proposed strategy to different case studies showed that daily revenues of up to EUR 1000 for each MW of renewable energy generation installed can be obtained. This value includes the benefit obtained thanks to the provision of flexibility services, which contribute about 58% of the total. Full article

(This article belongs to the Special Issue Smart Grid and Sustainable Energy Integration Technology)

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20 pages, 6222 KiB

Open AccessEditor’s ChoiceArticle

Analysis of Non-Road Mobile Machinery Homologation Standards in Relation to Actual Exhaust Emissions

by Natalia Szymlet, Michalina Kamińska, Andrzej Ziółkowski and Jakub Sobczak

Energies 2024, 17(15), 3624; https://doi.org/10.3390/en17153624 - 24 Jul 2024

Cited by 1 | Viewed by 723

Abstract

This article presents issues related to the current approval procedures in the group of off-road vehicles. Our research aimed to demonstrate significant differences between actual railway vehicle operation and stationary homologation tests regarding exhaust emissions. The research cycle consisted of analyzing emissions of [...] Read more.

This article presents issues related to the current approval procedures in the group of off-road vehicles. Our research aimed to demonstrate significant differences between actual railway vehicle operation and stationary homologation tests regarding exhaust emissions. The research cycle consisted of analyzing emissions of toxic compounds from exhaust systems under real operating conditions, supplemented by a temporal share analysis based on the denormalized NRTC test upon which the tested object was homologated. Based on the conducted analyses, a significant difference was found between the actual operation of the tested railway vehicle and the stationary homologation test. By interpreting emission intensities within the parameter ranges of the propulsion unit’s operation, key areas with a significant impact on the vehicle’s overall emissions were identified. Based on the obtained results, a critical opinion is expressed regarding current homologation standards for the off-road vehicle group and the necessity for further empirical research in the area of actual operation of the tested vehicle group. Full article

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

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18 pages, 1408 KiB

Open AccessEditor’s ChoiceReview

A Comprehensive Review of Syngas Production, Fuel Properties, and Operational Parameters for Biomass Conversion

by Saaida Khlifi, Victor Pozzobon and Marzouk Lajili

Energies 2024, 17(15), 3646; https://doi.org/10.3390/en17153646 - 24 Jul 2024

Cited by 2 | Viewed by 2366

Abstract

This study aims to provide an overview of the growing need for renewable energy conversion and aligns with the broader context of environmentally friendly energy, specifically through producing syngas from biomass. Unlike natural gas, which is mainly composed of methane, syngas contains a [...] Read more.

This study aims to provide an overview of the growing need for renewable energy conversion and aligns with the broader context of environmentally friendly energy, specifically through producing syngas from biomass. Unlike natural gas, which is mainly composed of methane, syngas contains a mixture of combustible CO, H₂, and C_nH_m. Therefore, optimizing its production requires a thorough examination of various operational parameters such as the gasifying agent, the equivalence ratio, the biofuel type, and the state, particularly in densified forms like pellets or briquettes. As new biomass sources are continually discovered and tested, operational parameters are also constantly evaluated, and new techniques are continuously developed. Indeed, these techniques include different gasifier types and the use or non-use of catalysts during biofuel conversion. The present study focuses on these critical aspects to examine their effect on the efficiency of syngas production. It is worth mentioning that syngas is the primary gaseous product from gasification. Moreover, it is essential to note that the pyrolysis process (prior to gasification) can produce, in addition to tar and char, a mixture of gases. The common feature among these gases is their versatility in energy generation, heat production, and chemical synthesis. The analysis encompasses the resulting gas features, including the yield and composition, mainly through the hydrogen-to-carbon monoxide ratio and the carbon monoxide-to-carbon dioxide ratio, as well as the lower heating value and considerations of the tar yield. Full article

(This article belongs to the Special Issue Low Carbon Energy Generation and Utilization Technologies)

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22 pages, 2347 KiB

Open AccessEditor’s ChoiceArticle

Well Integrity in Salt Cavern Hydrogen Storage

by Omid Ahmad Mahmoudi Zamani and Dariusz Knez

Energies 2024, 17(14), 3586; https://doi.org/10.3390/en17143586 - 21 Jul 2024

Cited by 2 | Viewed by 2109

Abstract

Underground hydrogen storage (UHS) in salt caverns is a sustainable energy solution to reduce global warming. Salt rocks provide an exceptional insulator to store natural hydrogen, as they have low porosity and permeability. Nevertheless, the salt creeping nature and hydrogen-induced impact on the [...] Read more.

Underground hydrogen storage (UHS) in salt caverns is a sustainable energy solution to reduce global warming. Salt rocks provide an exceptional insulator to store natural hydrogen, as they have low porosity and permeability. Nevertheless, the salt creeping nature and hydrogen-induced impact on the operational infrastructure threaten the integrity of the injection/production wells. Furthermore, the scarcity of global UHS initiatives indicates that investigations on well integrity remain insufficient. This study strives to profoundly detect the research gap and imperative considerations for well integrity preservation in UHS projects. The research integrates the salt critical characteristics, the geomechanical and geochemical risks, and the necessary measurements to maintain well integrity. The casing mechanical failure was found as the most challenging threat. Furthermore, the corrosive and erosive effects of hydrogen atoms on cement and casing may critically put the well integrity at risk. The research also indicated that the simultaneous impact of temperature on the salt creep behavior and hydrogen-induced corrosion is an unexplored area that has scope for further research. This inclusive research is an up-to-date source for analysis of the previous advancements, current shortcomings, and future requirements to preserve well integrity in UHS initiatives implemented within salt caverns. Full article

(This article belongs to the Special Issue Advanced Methods for Hydrogen Production, Storage and Utilization)

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20 pages, 12983 KiB

Open AccessEditor’s ChoiceArticle

Determination of Ambient Air Vaporizers’ Performance Based on a Study on Heat Transfer in Longitudinal Finned Tubes

by Filip Lisowski and Edward Lisowski

Energies 2024, 17(14), 3579; https://doi.org/10.3390/en17143579 - 21 Jul 2024

Viewed by 1177

Abstract

Ambient air vaporizers (AVVs) are the most commonly used type of heat exchanger for cryogenic regasification stations. The transfer of heat from the environment for heating the liquefied gas and its vaporization is a cost-free and efficient method. Designing ambient air vaporizers for [...] Read more.

Ambient air vaporizers (AVVs) are the most commonly used type of heat exchanger for cryogenic regasification stations. The transfer of heat from the environment for heating the liquefied gas and its vaporization is a cost-free and efficient method. Designing ambient air vaporizers for regasification or fueling stations requires accepting the size and related thermal power of the AVV considering the operating conditions and the type of liquefied gases to be vaporized. The nominal capacity of the ambient air vaporizer depends on its design, the frosting of longitudinal finned tubes, and the airflow through the vaporizer structure. This paper presents the results of experimental studies and computational fluid dynamics (CFD) analysis on determining the heat output of AVV longitudinal finned tubes depending on their design. This experiment was conducted in order to establish a numerical model. The relation between the longitudinal finned tubes thermal power and the air flow velocity is demonstrated and the beneficial effect of forced convection is proved. The obtained results are used for verification calculations of ambient air vaporizers’ performance depending on the size of the AVV, the profile cross-section, and the airflow velocity for different liquefied gases. Under conditions of forced convection, profiles with 12 equal-height fins were discovered to be the most efficient for higher airflow velocity providing up to 7% higher heat rate than profiles with 8 equal-height fins. However, at low air velocity, profiles with 8 equal-length fins showed a comparable heat output to profiles with 12 equal-length fins. Profiles with 8 and 12 unequal high fins differ in average heat output by about 28%. The profile with 12 unequal high fins turned out to be the least effective when 2D airflow was considered in this analysis. Full article

(This article belongs to the Collection Advances in Heat Transfer Enhancement)

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32 pages, 435 KiB

Open AccessEditor’s ChoiceReview

Critical Aspects of Energetic Transition Technologies and the Roles of Materials Chemistry and Engineering

by Guido Busca

Energies 2024, 17(14), 3565; https://doi.org/10.3390/en17143565 - 20 Jul 2024

Cited by 3 | Viewed by 996

Abstract

The perspectives of technological advances needed for short term energetic transition are briefly reviewed and discussed critically. In particular, the technologies for the greenhouse gas emission-free production of electrical energy, its storage and transport, the production, transport, storage and use of hydrogen, and [...] Read more.

The perspectives of technological advances needed for short term energetic transition are briefly reviewed and discussed critically. In particular, the technologies for the greenhouse gas emission-free production of electrical energy, its storage and transport, the production, transport, storage and use of hydrogen, and the use of biomass derived technologies are shortly and critically reviewed. Critical aspects are emphasized. The role of chemistry, and in particular materials chemistry and engineering, in short-term developments are underlined. Full article

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

15 pages, 274 KiB

Open AccessEditor’s ChoiceArticle

Socioeconomic Factors Driving the Transition to a Low-Carbon Energy System

by Evangelia Karasmanaki, Spyros Galatsidas and Georgios Tsantopoulos

Energies 2024, 17(14), 3576; https://doi.org/10.3390/en17143576 - 20 Jul 2024

Viewed by 998

Abstract

Citizen participation via different investment schemes may be a promising solution to the financing barriers inhibiting energy transition. In this regard, citizens may be approached as potential investors in renewables, but, to mobilize their capital, strategies need to be developed. Much like other [...] Read more.

Citizen participation via different investment schemes may be a promising solution to the financing barriers inhibiting energy transition. In this regard, citizens may be approached as potential investors in renewables, but, to mobilize their capital, strategies need to be developed. Much like other services or products seeking to improve their market position, renewable energy investments by citizens also require dedicated efforts to acquire a strong market position. Using a large sample of Greek citizens, this study investigated whether it is possible to identify distinct and addressable citizen clusters which can enable energy developers and marketers to effectively address the preferences and needs of potential investor segments. The performance of k-means cluster analysis identified four clusters: Indifferent Investors were neither driven by economic or social factors, Enthusiastic Investors were motivated both by economic and social factors, Pro-environmental Investors were driven by the environmental benefits, and Social Investors were motivated by the social aspects of the investment. Moreover, each cluster demonstrated different levels of willingness-to-invest in renewable energy and were knowledge about renewable energy investments. It was concluded that citizens should not be approached as a homogeneous target group by marketing experts and policymakers, while novel strategies should be followed. Full article

(This article belongs to the Special Issue Sustainable and Low Carbon Development in the Energy Sector)

29 pages, 4718 KiB

Open AccessEditor’s ChoiceArticle

Optimal Operation of an Industrial Microgrid within a Renewable Energy Community: A Case Study of a Greentech Company

by Matteo Fresia, Tommaso Robbiano, Martina Caliano, Federico Delfino and Stefano Bracco

Energies 2024, 17(14), 3567; https://doi.org/10.3390/en17143567 - 20 Jul 2024

Cited by 1 | Viewed by 775

Abstract

The integration of renewable energy sources in the European power system is one of the main goals set by the European Union. In order to ease this integration, in recent years, Renewable Energy Communities (RECs) have been introduced that aim to increase the [...] Read more.

The integration of renewable energy sources in the European power system is one of the main goals set by the European Union. In order to ease this integration, in recent years, Renewable Energy Communities (RECs) have been introduced that aim to increase the exploitation of renewable energy at the local level. This paper presents an Energy Management System (EMS) for an industrial microgrid owned and operated by a greentech company located in the north of Italy. The company is a member of an REC. The microgrid is made of interconnected busbars, integrating photovoltaic power plants, a fleet of electric vehicles, including company cars and delivery trucks supporting Vehicle-to-Grid (V2G), dedicated charging stations, and a centralized battery energy storage system. The industrial site includes two warehouses, an office building, and a connection to the external medium-voltage network. The EMS is designed to optimize the operation of the microgrid and minimize the operating costs related to the sale and purchase of energy from the external network. Furthermore, as the company is a member of an REC, the EMS must try to follow a desired power exchange profile with the grid, suggested by the REC manager, with the purpose of maximizing the energy that is shared within the community and incentivized. The results demonstrate that, when minimizing only costs, local self-consumption is favored, leading to a Self-Sufficiency Rate (SSR) of 65.37%. On the other hand, when only the adherence to the REC manager’s desired power exchange profile is considered in the objective function, the SSR decreases to 56.43%, net operating costs increase, and the energy shared within the REC is maximized. Full article

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

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40 pages, 6510 KiB

Open AccessEditor’s ChoiceReview

Review of Various Sensor Technologies in Monitoring the Condition of Power Transformers

by Meysam Beheshti Asl, Issouf Fofana and Fethi Meghnefi

Energies 2024, 17(14), 3533; https://doi.org/10.3390/en17143533 - 18 Jul 2024

Viewed by 3744

Abstract

Modern power grids are undergoing a significant transformation with the massive integration of renewable, decentralized, and electronically interfaced energy sources, alongside new digital and wireless communication technologies. This transition necessitates the widespread adoption of robust online diagnostic and monitoring tools. Sensors, known for [...] Read more.

Modern power grids are undergoing a significant transformation with the massive integration of renewable, decentralized, and electronically interfaced energy sources, alongside new digital and wireless communication technologies. This transition necessitates the widespread adoption of robust online diagnostic and monitoring tools. Sensors, known for their intuitive and smart capabilities, play a crucial role in efficient condition monitoring, aiding in the prediction of power outages and facilitating the digital twinning of power equipment. This review comprehensively analyzes various sensor technologies used for monitoring power transformers, focusing on the critical need for reliable and efficient fault detection. The study explores the application of fiber Bragg grating (FBG) sensors, optical fiber sensors, wireless sensing networks, chemical sensors, ultra-high-frequency (UHF) sensors, and piezoelectric sensors in detecting parameters such as partial discharges, core condition, temperature, and dissolved gases. Through an extensive literature review, the sensitivity, accuracy, and practical implementation challenges of these sensor technologies are evaluated. Significant advances in real-time monitoring capabilities and improved diagnostic precision are highlighted in the review. It also identifies key challenges such as environmental susceptibility and the long-term stability of sensors. By synthesizing the current research and methodologies, this paper provides valuable insights into the integration and optimization of sensor technologies for enhancing transformer condition monitoring and reliability in modern power systems. Full article

(This article belongs to the Special Issue Energy, Electrical and Power Engineering 2024)

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18 pages, 612 KiB

Open AccessEditor’s ChoiceArticle

Optimal Placement of Multiple Sources in a Mesh-Type DC Microgrid Using Dijkstra’s Algorithm

by Fouad Boutros, Moustapha Doumiati, Jean-Christophe Olivier, Imad Mougharbel and Hadi Kanaan

Energies 2024, 17(14), 3493; https://doi.org/10.3390/en17143493 - 16 Jul 2024

Viewed by 1160

Abstract

This research paper introduces an optimization methodology for the strategic electric sources’ placement at multiple positions in a DC islanded microgrid characterized by a mesh network, aiming to minimize line losses while considering minimal cable weight. The DC microgrid studied in this paper [...] Read more.

This research paper introduces an optimization methodology for the strategic electric sources’ placement at multiple positions in a DC islanded microgrid characterized by a mesh network, aiming to minimize line losses while considering minimal cable weight. The DC microgrid studied in this paper is composed of PV panels, batteries, a diesel generator, and 20 residential loads. Employing Dijkstra’s algorithm, a graph algorithm used in Google Maps, the study identifies the shortest path (resistance) between potential source nodes and various variable loads within a predefined electric distribution mesh network topology. This study focuses on active power considerations and offers valuable insights into the placement optimization of multiple sources’ positions in DC microgrid mesh networks. A key contribution of this paper lies in the ranking of source node positions based on minimal to maximal line losses, taking into consideration optimal cable weights, while using MATPOWER to validate sources’ ranking based on Dijkstra’s hypothesis. The research further includes a techno-economic study to assess the viability of sources’ placement at multiple positions within the mesh network, comparing it with the optimal placement scenario involving a single position for all sources. This methodology serves as a valuable resource for system designers and operators aiming to minimize line losses and optimize energy distribution in DC microgrids in a mesh topology. Full article

(This article belongs to the Special Issue Application of Reinforcement Learning in Energy Management of Microgrids and Hybrid Energy Storage Systems)

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24 pages, 3459 KiB

Open AccessEditor’s ChoiceArticle

Matching Characteristics of Refrigerant and Operating Parameters in Large Temperature Variation Heat Pump

by Hemin Hu, Tao Wang, Fan Zhang, Bing Zhang and Jian Qi

Energies 2024, 17(14), 3477; https://doi.org/10.3390/en17143477 - 15 Jul 2024

Viewed by 883

Abstract

Characterizing the optimal operating parameters for a heat pump with a specific refrigerant is paramount, as it provides valuable guidance for refrigerant selection. The temperature mismatch between cold and hot fluids in the evaporator and condenser can lead to degraded thermal performance in [...] Read more.

Characterizing the optimal operating parameters for a heat pump with a specific refrigerant is paramount, as it provides valuable guidance for refrigerant selection. The temperature mismatch between cold and hot fluids in the evaporator and condenser can lead to degraded thermal performance in heat pumps with large temperature variations. To address these two key issues, we selected several pure refrigerants with varying critical temperature levels for use in a large temperature variation heat pump configuration. The corresponding thermal performance was then investigated using the Ebsilon code under fixed temperature lift conditions as the operating temperature varied. It indicates that the maximum coefficient of performance (COP) is typically achieved when the deviation factors of temperature and pressure from their critical parameters fall within the ranges of 0.62~0.71 and 0.36~0.5, respectively. Our research recommends the binary refrigerant mixture of R152a/R1336mzz(z) (COP = 3.54) for the current operating conditions, as it significantly improves thermal performance compared to pure R1336mzz (z) (COP = 2.87) and R152a (COP = 3.01). Through research on the impact of the compositional ratio of R152a/R1336mzz(z) on the thermal performance of the heat pump, we found that that the optimal ratio of R1336mzz(z) component to R152a component is 0.5/0.5. This study offers valuable guidance for selecting the most suitable refrigerants for heat pumps in practical engineering design scenarios. Full article

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

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29 pages, 6436 KiB

Open AccessEditor’s ChoiceArticle

Price Risk Exposure of Small Participants in Liberalized Multi-National Power Markets: A Case Study on the Belize–Mexico Interconnection

by Khadija Sherece Usher and Benjamin Craig McLellan

Energies 2024, 17(14), 3464; https://doi.org/10.3390/en17143464 - 14 Jul 2024

Viewed by 789

Abstract

This study examined the price risk of the Belize–Mexico interconnection using ARMA-ARCH models to assess electricity pricing volatility and autoregression to determine the influence of conditional volatilities and import consumption. The findings revealed that the volatility of both markets, especially spot price, showed [...] Read more.

This study examined the price risk of the Belize–Mexico interconnection using ARMA-ARCH models to assess electricity pricing volatility and autoregression to determine the influence of conditional volatilities and import consumption. The findings revealed that the volatility of both markets, especially spot price, showed rare high-impact shocks and prolonged periods of volatile clusters. Volatile pricing tendencies, and forward pricing to a lesser extent, had positive effects on premiums. Premiums were largely dependent on pricing properties and system conditions of the supplier’s (Mexico) side, with negligible influence from the buyer’s (Belize) side. However, significant effects were found during certain hours with the buyer’s loading and transmission loss patterns. Practical implications revealed the possibility of occasional losses caused mostly by information delays and misalignment of risk factors and premiums, which could affect Belize’s power cost affordability and scheduling of local generation. Further research can broaden this current scope to enhance planning on local power supply by integrating current findings on the importation market behavior with the buyer’s local power expansion plan. Full article

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

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24 pages, 4041 KiB

Open AccessEditor’s ChoiceArticle

Transformation towards a Low-Emission and Energy-Efficient Economy Realized in Agriculture through the Increase in Controllability of the Movement of Units Mowing Crops While Simultaneously Discing Their Stubble

by Olga Orynycz, Volodymyr Nadykto, Volodymyr Kyurchev, Karol Tucki and Ewa Kulesza

Energies 2024, 17(14), 3467; https://doi.org/10.3390/en17143467 - 14 Jul 2024

Viewed by 1022

Abstract

When harvesting cereals and fodder grasses, a two-phase method is often used. This process is carried out using trailed and suspended collecting units. The former are asymmetrical and often pose problems regarding the stability of their movement in the horizontal plane. In practice, [...] Read more.

When harvesting cereals and fodder grasses, a two-phase method is often used. This process is carried out using trailed and suspended collecting units. The former are asymmetrical and often pose problems regarding the stability of their movement in the horizontal plane. In practice, suspended harvesting units with a front-mounted header are becoming more and more widely used. The disadvantage of their use is that the soil is exposed after passing through the space between the swaths of the mown crop. This is followed by an intense loss of moisture. In order to eliminate this shortcoming, a collecting unit was proposed, consisting of a tractor with a front attachment and a disc harrow mounted at the rear. An appropriate mathematical model was developed to justify the scheme and parameters of such a unit. In this case, this model is used to assess the controllability of the movement of the dynamic system under the influence of control action in the form of the angular rotation of the tractor’s steered wheels. As a result of mathematical modelling, it was found that satisfactory controllability of the movement of the harvesting units can be ensured by acting on the tractor’s driven wheels with a frequency of 0–1 s⁻¹ and a working speed of close to 3 m·s⁻¹. In this case, it is desirable to set the deflection resistance coefficient of the rear tyres of the tractor (and therefore, the air pressure in them) to a smaller value, and that of the front tyres to a larger value. This helps both to improve the movement controllability of the harvesting unit and to reduce its energy consumption by an average of 6.75%. The emissivity of selected harmful chemicals and particulates emitted by the harvesting unit, depending on the fuel burned, was also examined. The way in which the use of the harvesting unit affects the reduction of emissions of harmful compounds into the atmosphere was also revealed. Full article

(This article belongs to the Special Issue Energy from Agricultural and Forestry Biomass Waste)

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36 pages, 2270 KiB

Open AccessEditor’s ChoiceArticle

Variable-Length Pendulum-Based Mechatronic Systems for Energy Harvesting: A Review of Dynamic Models

by Godiya Yakubu, Paweł Olejnik and Ademola B. Adisa

Energies 2024, 17(14), 3469; https://doi.org/10.3390/en17143469 - 14 Jul 2024

Cited by 1 | Viewed by 1967

Abstract

The ability to power low-power devices and sensors has drawn a great deal of interest to energy harvesting from ambient vibrations. The application of variable-length pendulum systems in conjunction with piezoelectric or electromagnetic energy-harvesting devices is examined in this thorough analysis. Because of [...] Read more.

The ability to power low-power devices and sensors has drawn a great deal of interest to energy harvesting from ambient vibrations. The application of variable-length pendulum systems in conjunction with piezoelectric or electromagnetic energy-harvesting devices is examined in this thorough analysis. Because of their changeable length, such pendulums may effectively convert mechanical vibrations into electrical energy. This study covers these energy-harvesting systems’ basic theories, design concerns, modeling methods, and performance optimization strategies. This article reviews several studies that look at dynamic models, the effects of damping coefficients, device designs, and excitation parameters on energy output. The advantages and disadvantages of piezoelectric and electromagnetic coupling techniques are demonstrated by comparative research. This review also looks at technical advances and future research prospects in variable-length, pendulum-based energy harvesting. An expanded model for an energy harvester based on a variable-length pendulum derived from the modified, swinging Atwood machine is more specifically presented. This model’s numerical simulations, estimated current and voltage outputs, and produced power from the electromagnetic and piezoelectric devices integrated at various points in a 4-DOF variable-length pendulum model all indicate encouraging results. This necessitates extra study, changes, and optimizations to improve the usefulness of the proposed model. Finally, important dynamic models on developing variable-length, pendulum-based energy harvesters for usage in a range of applications to create sustainable energy are summarized. Full article

(This article belongs to the Special Issue Electromagnetic Field Computation for Electrical Engineering Devices)

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22 pages, 7775 KiB

Open AccessEditor’s ChoiceArticle

Numerical and Experimental Determination of Selected Performance Indicators of the Liquid Flat-Plate Solar Collector under Outdoor Conditions

by Wiesław Zima, Łukasz Mika and Karol Sztekler

Energies 2024, 17(14), 3454; https://doi.org/10.3390/en17143454 - 13 Jul 2024

Viewed by 821

Abstract

The paper proposes applying an in-house mathematical model of a liquid flat-plate solar collector to calculate the collector time constant. The described model, proposed for the first time in an earlier study, is a one-dimensional distributed parameter model enabling simulations of the collector [...] Read more.

The paper proposes applying an in-house mathematical model of a liquid flat-plate solar collector to calculate the collector time constant. The described model, proposed for the first time in an earlier study, is a one-dimensional distributed parameter model enabling simulations of the collector operation under arbitrarily variable boundary conditions. The model is based on the solution of energy balance equations for all collector components. The formulated differential equations are solved iteratively using an implicit difference scheme. To obtain a stable numerical solution, it is necessary to use appropriate steps of time and spatial division. These were found by comparing the results obtained from the model with the results of the analytical solution available in the literature for the transient state, which constitutes the novelty of the present study. The accuracy of the results obtained from the model was verified experimentally by comparing the measured and calculated history of the fluid temperature at the outlet of the collector. The calculation of the collector time constant is proposed in the paper as an example of the model’s practical application. The results of the time constant calculation were compared with the values obtained experimentally on the test stand. This is another novelty of the presented research. The analysed collector instantaneous efficiency was then calculated for selected outdoor conditions. The presented mathematical model can also be used to verify the correctness of the collector operation. By comparing, on an ongoing basis, the measured and calculated values of the fluid temperature at the collector outlet, conclusions can be drawn about the process of solar glass fouling or glycol gelling. The simplicity of the model and the low computational demands enable such comparisons in an online mode. Full article

(This article belongs to the Special Issue Solar Energy and Resource Utilization)

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51 pages, 6514 KiB

Open AccessEditor’s ChoiceReview

Review on Absorption Refrigeration Technology and Its Potential in Energy-Saving and Carbon Emission Reduction in Natural Gas and Hydrogen Liquefaction

by Lisong Wang, Lijuan He and Yijian He

Energies 2024, 17(14), 3427; https://doi.org/10.3390/en17143427 - 11 Jul 2024

Cited by 1 | Viewed by 1903

Abstract

With the requirement of energy decarbonization, natural gas (NG) and hydrogen (H₂) become increasingly important in the world’s energy landscape. The liquefaction of NG and H₂ significantly increases energy density, facilitating large-scale storage and long-distance transport. However, conventional liquefaction processes [...] Read more.

With the requirement of energy decarbonization, natural gas (NG) and hydrogen (H₂) become increasingly important in the world’s energy landscape. The liquefaction of NG and H₂ significantly increases energy density, facilitating large-scale storage and long-distance transport. However, conventional liquefaction processes mainly adopt electricity-driven compression refrigeration technology, which generally results in high energy consumption and carbon dioxide emissions. Absorption refrigeration technology (ART) presents a promising avenue for enhancing energy efficiency and reducing emissions in both NG and H₂ liquefaction processes. Its ability to utilize industrial waste heat and renewable thermal energy sources over a large temperature range makes it particularly attractive for sustainable energy practices. This review comprehensively analyzes the progress of ART in terms of working pairs, cycle configurations, and heat and mass transfer in main components. To operate under different driven heat sources and refrigeration temperatures, working pairs exhibit a diversified development trend. The environment-friendly and high-efficiency working pairs, in which ionic liquids and deep eutectic solvents are new absorbents, exhibit promising development potential. Through the coupling of heat and mass transfer within the cycle or the addition of sub-components, cycle configurations with higher energy efficiency and a wider range of operational conditions are greatly focused. Additives, ultrasonic oscillations, and mechanical treatment of heat exchanger surfaces efficiently enhance heat and mass transfer in the absorbers and generators of ART. Notably, nanoparticle additives and ultrasonic oscillations demonstrate a synergistic enhancement effect, which could significantly improve the energy efficiency of ART. For the conventional NG and H₂ liquefaction processes, the energy-saving and carbon emission reduction potential of ART is analyzed from the perspectives of specific power consumption (SPC) and carbon dioxide emissions (CEs). The results show that ART integrated into the liquefaction processes could reduce the SPC and CE by 10~38% and 10~36% for NG liquefaction processes, and 2~24% and 5~24% for H₂ liquefaction processes. ART, which can achieve lower precooling temperatures and higher energy efficiency, shows more attractive perspectives in low carbon emissions of NG and H₂ liquefaction. Full article

(This article belongs to the Special Issue Thermal Energy Storage Systems Modeling and Experimentation)

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17 pages, 4377 KiB

Open AccessEditor’s ChoiceArticle

Integrating Renewable Energy Produced by a Library Building on a University Campus in a Scenario of Collective Self-Consumption

by Ivo Araújo, Leonel J. R. Nunes, David Patíño Vilas and António Curado

Energies 2024, 17(14), 3405; https://doi.org/10.3390/en17143405 - 11 Jul 2024

Cited by 1 | Viewed by 1160

Abstract

Rising fossil fuel costs and environmental concerns are driving the search for new energy sources, particularly renewable energy. Among these sources, solar photovoltaic (PV) is the most promising in southern European countries, mainly through the use of decentralised PV systems designed to produce [...] Read more.

Rising fossil fuel costs and environmental concerns are driving the search for new energy sources, particularly renewable energy. Among these sources, solar photovoltaic (PV) is the most promising in southern European countries, mainly through the use of decentralised PV systems designed to produce electricity close to the point of demand and primarily to meet local energy needs. In an urban scenario, a decentralised energy system usually operates in parallel with the grid, allowing excess power generated to be injected into the grid. Solar carports and rooftop systems are excellent examples of distributed photovoltaic systems, which are far more sustainable than large centralised systems because they do not compete for land use. Despite their operational advantages, these decentralised photovoltaic production plants, which are in most cases financed by specific energy efficiency programs, present challenges in a regulated market where the injection of energy into the electricity grid is restricted by law and support programs. The aim of this work is to integrate two different photovoltaic systems within an academic campus where the only PV source currently available is a solar car park, a solution designed both to provide shaded space for vehicles and to produce energy to be consumed within the facilities. Due to legal restrictions, surplus electricity cannot be sold to the national grid, and solar batteries to store the generated energy are expensive and have a short lifespan. Therefore, since the campus has two different grid connections and a 102.37 kWp PV system, the newly designed system to be installed on the library roof must be calculated to support the installed electricity system during the most critical working hours, determining the specific angle and orientation of the solar panels. On this basis, the energy management of a school campus is fundamental to creating a collective self-consumption system, the basis of a local energy community that can meet energy, environmental, and social objectives. Full article

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

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23 pages, 2181 KiB

Open AccessEditor’s ChoiceArticle

The Role of Blockchain-Secured Digital Twins in Promoting Smart Energy Performance-Based Contracts for Buildings

by Mohamed Nour El-Din, João Poças Martins, Nuno M. M. Ramos and Pedro F. Pereira

Energies 2024, 17(14), 3392; https://doi.org/10.3390/en17143392 - 10 Jul 2024

Viewed by 863

Abstract

Energy performance-based contracts (EPCs) offer a promising solution for enhancing the energy performance of buildings, which is an overarching step towards achieving Net Zero Carbon Buildings, addressing climate change and improving occupants’ comfort. Despite their potential, their execution is constrained by difficulties that [...] Read more.

Energy performance-based contracts (EPCs) offer a promising solution for enhancing the energy performance of buildings, which is an overarching step towards achieving Net Zero Carbon Buildings, addressing climate change and improving occupants’ comfort. Despite their potential, their execution is constrained by difficulties that hinder their diffusion in the architecture, engineering, construction, and operation industry. Notably, the Measurement and Verification process is considered a significant impediment due to data sharing, storage, and security challenges. Nevertheless, there have been minimal efforts to analyze research conducted in this field systematically. A systematic analysis of 113 identified journal articles was conducted to fill this gap. A paucity of research tackling the utilization of digital technologies to enhance the implementation of EPCs was found. Consequently, this article proposes a framework integrating Digital Twin and Blockchain technologies to provide an enhanced EPC execution environment. Digital Twin technology leverages the system by monitoring and evaluating energy performance in real-time, predicting future performance, and facilitating informed decisions. Blockchain technology ensures the integrity, transparency, and accountability of information. Moreover, a private Blockchain infrastructure was originally introduced in the framework to eliminate high transaction costs related to on-chain storage and potential concerns regarding the confidentiality of information in open distributed ledgers. Full article

(This article belongs to the Special Issue Solutions towards Zero Carbon Buildings)

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