Energies

18 pages, 2244 KiB

Open AccessEditor’s ChoiceArticle

An Energy Consumption Approach to Estimate Air Emission Reductions in Container Shipping

by Ernest Czermański, Giuseppe T. Cirella, Aneta Oniszczuk-Jastrząbek, Barbara Pawłowska and Theo Notteboom

Energies 2021, 14(2), 278; https://doi.org/10.3390/en14020278 - 6 Jan 2021

Cited by 45 | Viewed by 5669

Abstract

Container shipping is the largest producer of emissions within the maritime shipping industry. Hence, measures have been designed and implemented to reduce ship emission levels. IMO’s MARPOL Annex VI, with its future plan of applying Tier III requirements, the Energy Efficiency Design Index [...] Read more.

Container shipping is the largest producer of emissions within the maritime shipping industry. Hence, measures have been designed and implemented to reduce ship emission levels. IMO’s MARPOL Annex VI, with its future plan of applying Tier III requirements, the Energy Efficiency Design Index for new ships, and the Ship Energy Efficiency Management Plan for all ships. To assist policy formulation and follow-up, this study applies an energy consumption approach to estimate container ship emissions. The volumes of sulphur oxide (SO_x), nitrous oxide (NO_x), particulate matter (PM), and carbon dioxide (CO₂) emitted from container ships are estimated using 2018 datasets on container shipping and average vessel speed records generated via AIS. Furthermore, the estimated reductions in SO_x, NO_x, PM, and CO₂ are mapped for 2020. The empirical analysis demonstrates that the energy consumption approach is a valuable method to estimate ongoing emission reductions on a continuous basis and to fill data gaps where needed, as the latest worldwide container shipping emissions records date back to 2015. The presented analysis supports early-stage detection of environmental impacts in container shipping and helps to determine in which areas the greatest potential for emission reductions can be found. Full article

(This article belongs to the Special Issue Energy Security as a Key Driving Factor for Socioeconomic Development: From Mitigation to Solution)

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17 pages, 826 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Fresh Validation of the Low Carbon Development Hypothesis under the EKC Scheme in Portugal, Italy, Greece and Spain

by Daniel Balsalobre-Lorente, Nuno Carlos Leitão and Festus Victor Bekun

Energies 2021, 14(1), 250; https://doi.org/10.3390/en14010250 - 5 Jan 2021

Cited by 52 | Viewed by 5426

Abstract

The present study is in line with the United Nations Sustainable Development Goals (UN-SDGs) that address pertinent global issues. This study focuses on the need for access to clean and affordable energy consumption, responsible energy consumption, sustainable economic growth, and climate change mitigation. [...] Read more.

The present study is in line with the United Nations Sustainable Development Goals (UN-SDGs) that address pertinent global issues. This study focuses on the need for access to clean and affordable energy consumption, responsible energy consumption, sustainable economic growth, and climate change mitigation. To this end, this paper evaluates the relevance of the renewable energy sector on the environmental Kuznets curve (EKC) framework in Portugal, Italy, Greece, and Spain for the period 1995–2015. As an econometric strategy, we adopt the use of panel data over the highlighted countries. In the first step, we apply the unit root test recommended by Levin, Lin, and Chu in conjunction with ADF-Fisher, and Phillips-Perron for robustness and consistency. We found that the variables used in this study are integrated I (1) in the first difference. In the second step, we apply the Pedroni cointegration test, and Kao Residual cointegration test, and we observe that the variables are cointegrated in the long run. The generalized least squares (GLS), the panel fully modified least squares (FMOLS), ordinary least squares robust (OLS), and panel quantile regression are considered in this research. The econometric results validate the assumption of the environmental Kuznets curve, i.e., and there is a positive correlation between income per capita and a negative effect of squared income per capita on carbon dioxide emissions. In contrast, we observe that renewable energy reduces CO₂ emissions. Finally, we also find a direct connection between the urban population and the environmental degradation in the examined blocs. These results show that in Portugal, Italy, Greece, and Spain, more is required to achieve environmental sustainability in the respective countries growth trajectory. Further policy prescriptions are appended in the concluding section of this study. Full article

(This article belongs to the Special Issue Economic Growth and Environmental Degradation in the Paradigm of Energy Transition)

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29 pages, 6742 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Fuel Cell Electric Vehicles—A Brief Review of Current Topologies and Energy Management Strategies

by Ioan-Sorin Sorlei, Nicu Bizon, Phatiphat Thounthong, Mihai Varlam, Elena Carcadea, Mihai Culcer, Mariana Iliescu and Mircea Raceanu

Energies 2021, 14(1), 252; https://doi.org/10.3390/en14010252 - 5 Jan 2021

Cited by 231 | Viewed by 18602

Abstract

With the development of technologies in recent decades and the imposition of international standards to reduce greenhouse gas emissions, car manufacturers have turned their attention to new technologies related to electric/hybrid vehicles and electric fuel cell vehicles. This paper focuses on electric fuel [...] Read more.

With the development of technologies in recent decades and the imposition of international standards to reduce greenhouse gas emissions, car manufacturers have turned their attention to new technologies related to electric/hybrid vehicles and electric fuel cell vehicles. This paper focuses on electric fuel cell vehicles, which optimally combine the fuel cell system with hybrid energy storage systems, represented by batteries and ultracapacitors, to meet the dynamic power demand required by the electric motor and auxiliary systems. This paper compares the latest proposed topologies for fuel cell electric vehicles and reveals the new technologies and DC/DC converters involved to generate up-to-date information for researchers and developers interested in this specialized field. From a software point of view, the latest energy management strategies are analyzed and compared with the reference strategies, taking into account performance indicators such as energy efficiency, hydrogen consumption and degradation of the subsystems involved, which is the main challenge for car developers. The advantages and disadvantages of three types of strategies (rule-based strategies, optimization-based strategies and learning-based strategies) are discussed. Thus, future software developers can focus on new control algorithms in the area of artificial intelligence developed to meet the challenges posed by new technologies for autonomous vehicles. Full article

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

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20 pages, 3008 KiB

Open AccessEditor’s ChoiceReview

Vanadium Redox Flow Batteries: A Review Oriented to Fluid-Dynamic Optimization

by Iñigo Aramendia, Unai Fernandez-Gamiz, Adrian Martinez-San-Vicente, Ekaitz Zulueta and Jose Manuel Lopez-Guede

Energies 2021, 14(1), 176; https://doi.org/10.3390/en14010176 - 31 Dec 2020

Cited by 67 | Viewed by 12093

Abstract

Large-scale energy storage systems (ESS) are nowadays growing in popularity due to the increase in the energy production by renewable energy sources, which in general have a random intermittent nature. Currently, several redox flow batteries have been presented as an alternative of the [...] Read more.

Large-scale energy storage systems (ESS) are nowadays growing in popularity due to the increase in the energy production by renewable energy sources, which in general have a random intermittent nature. Currently, several redox flow batteries have been presented as an alternative of the classical ESS; the scalability, design flexibility and long life cycle of the vanadium redox flow battery (VRFB) have made it to stand out. In a VRFB cell, which consists of two electrodes and an ion exchange membrane, the electrolyte flows through the electrodes where the electrochemical reactions take place. Computational Fluid Dynamics (CFD) simulations are a very powerful tool to develop feasible numerical models to enhance the performance and lifetime of VRFBs. This review aims to present and discuss the numerical models developed in this field and, particularly, to analyze different types of flow fields and patterns that can be found in the literature. The numerical studies presented in this review are a helpful tool to evaluate several key parameters important to optimize the energy systems based on redox flow technologies. Full article

(This article belongs to the Special Issue Selected Papers from Eight European Conference on Renewable Energy Systems (ECRES2020))

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17 pages, 2909 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Water-Energy-Nutrients Synergies in the Agrifood Sector: A Circular Economy Framework

by Efthymios Rodias, Eirini Aivazidou, Charisios Achillas, Dimitrios Aidonis and Dionysis Bochtis

Energies 2021, 14(1), 159; https://doi.org/10.3390/en14010159 - 30 Dec 2020

Cited by 63 | Viewed by 8411

Abstract

Circular economy is emerging as a regenerative concept that minimizes emissions, relies on renewable energy, and eliminates waste based on the design of closed-loop systems and the reuse of materials and resources. The implementation of circular economy practices in resource-consuming agricultural systems is [...] Read more.

Circular economy is emerging as a regenerative concept that minimizes emissions, relies on renewable energy, and eliminates waste based on the design of closed-loop systems and the reuse of materials and resources. The implementation of circular economy practices in resource-consuming agricultural systems is essential for reducing the environmental ramifications of the currently linear systems. As the renewable segment of circular economy, bioeconomy facilitates the production of renewable biological resources (i.e., biomass) that transform into nutrients, bio-based products, and bioenergy. The use of recycled agro-industrial wastewater in agricultural activities (e.g., irrigation) can further foster the circularity of the bio-based systems. In this context, this paper aims to provide a literature review in the field of circular economy for the agrifood sector to enhance resource efficiency by: (i) minimizing the use of natural resources (e.g., water, energy), (ii) decreasing the use of chemical fertilizers, (iii) utilizing bio-based materials (e.g., agricultural/livestock residues), and (iv) reusing wastewater from agrifood operations. The final objective is to investigate any direct or indirect interactions within the water-energy-nutrients nexus. The derived framework of synergetic circular economy interventions in agriculture can act as a basis for developing circular bio-based business models and creating value-added agrifood products. Full article

(This article belongs to the Special Issue Energy Efficient Supply Chains)

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21 pages, 5372 KiB

Open AccessEditor’s ChoiceArticle

Wind Turbine Data Analysis and LSTM-Based Prediction in SCADA System

by Imre Delgado and Muhammad Fahim

Energies 2021, 14(1), 125; https://doi.org/10.3390/en14010125 - 29 Dec 2020

Cited by 68 | Viewed by 7929

Abstract

The number of wind farms is increasing every year because many countries are turning their attention to renewable energy sources. Wind turbines are considered one of the best alternatives to produce clean energy. Most of the wind farms installed supervisory control and data [...] Read more.

The number of wind farms is increasing every year because many countries are turning their attention to renewable energy sources. Wind turbines are considered one of the best alternatives to produce clean energy. Most of the wind farms installed supervisory control and data acquisition (SCADA) system in their turbines to monitor wind turbines and logged the information as time-series data. It demands a powerful information extraction process for analysis and prediction. In this research, we present a data analysis framework to visualize the collected data from the SCADA system and recurrent neural network-based variant long short-term memory (LSTM) based prediction. The data analysis is presented in cartesian, polar, and cylindrical coordinates to understand the wind and energy generation relationship. The four features: wind speed, direction, generated active power, and theoretical power are predicted and compared with state-of-the-art methods. The obtained results confirm the applicability of our model in real-life scenarios that can assist the management team to manage the generated energy of wind turbines. Full article

(This article belongs to the Special Issue Soft Computing Techniques in Energy System)

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27 pages, 9262 KiB

Open AccessEditor’s ChoiceReview

Polybenzimidazole-Based Polymer Electrolyte Membranes for High-Temperature Fuel Cells: Current Status and Prospects

by Zhengping Zhou, Oksana Zholobko, Xiang-Fa Wu, Ted Aulich, Jivan Thakare and John Hurley

Energies 2021, 14(1), 135; https://doi.org/10.3390/en14010135 - 29 Dec 2020

Cited by 56 | Viewed by 6537

Abstract

Polymer electrolyte membrane fuel cells (PEMFCs) expect a promising future in addressing the major problems associated with production and consumption of renewable energies and meeting the future societal and environmental needs. Design and fabrication of new proton exchange membranes (PEMs) with high proton [...] Read more.

Polymer electrolyte membrane fuel cells (PEMFCs) expect a promising future in addressing the major problems associated with production and consumption of renewable energies and meeting the future societal and environmental needs. Design and fabrication of new proton exchange membranes (PEMs) with high proton conductivity and durability is crucial to overcome the drawbacks of the present PEMs. Acid-doped polybenzimidazoles (PBIs) carry high proton conductivity and long-term thermal, chemical, and structural stabilities are recognized as the suited polymeric materials for next-generation PEMs of high-temperature fuel cells in place of Nafion^® membranes. This paper aims to review the recent developments in acid-doped PBI-based PEMs for use in PEMFCs. The structures and proton conductivity of a variety of acid-doped PBI-based PEMs are discussed. More recent development in PBI-based electrospun nanofiber PEMs is also considered. The electrochemical performance of PBI-based PEMs in PEMFCs and new trends in the optimization of acid-doped PBIs are explored. Full article

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21 pages, 27857 KiB

Open AccessEditor’s ChoiceReview

Technical and Commercial Challenges of Proton-Exchange Membrane (PEM) Fuel Cells

by Abed Alaswad, Abdelnasir Omran, Jose Ricardo Sodre, Tabbi Wilberforce, Gianmichelle Pignatelli, Michele Dassisti, Ahmad Baroutaji and Abdul Ghani Olabi

Energies 2021, 14(1), 144; https://doi.org/10.3390/en14010144 - 29 Dec 2020

Cited by 129 | Viewed by 12891

Abstract

This review critically evaluates the latest trends in fuel cell development for portable and stationary fuel cell applications and their integration into the automotive industry. Fast start-up, high efficiency, no toxic emissions into the atmosphere and good modularity are the key advantages of [...] Read more.

This review critically evaluates the latest trends in fuel cell development for portable and stationary fuel cell applications and their integration into the automotive industry. Fast start-up, high efficiency, no toxic emissions into the atmosphere and good modularity are the key advantages of fuel cell applications. Despite the merits associated with fuel cells, the high cost of the technology remains a key factor impeding its widespread commercialization. Therefore, this review presents detailed information into the best operating conditions that yield maximum fuel cell performance. The paper recommends future research geared towards robust fuel cell geometry designs, as this determines the cell losses, and material characterization of the various cell components. When this is done properly, it will support a total reduction in the cost of the cell which in effect will reduce the total cost of the system. Despite the strides made by the fuel cell research community, there is a need for public sensitization as some people have reservations regarding the safety of the technology. This hurdle can be overcome if there is a well-documented risk assessment, which also needs to be considered in future research activities. Full article

(This article belongs to the Special Issue Advances in Hydrogen and Fuel Cell Systems)

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27 pages, 1922 KiB

Open AccessEditor’s ChoiceReview

Cyber-Security of Smart Microgrids: A Survey

by Farzam Nejabatkhah, Yun Wei Li, Hao Liang and Rouzbeh Reza Ahrabi

Energies 2021, 14(1), 27; https://doi.org/10.3390/en14010027 - 23 Dec 2020

Cited by 112 | Viewed by 9185

Abstract

In this paper, the cyber-security of smart microgrids is thoroughly discussed. In smart grids, the cyber system and physical process are tightly coupled. Due to the cyber system’s vulnerabilities, any cyber incidents can have economic and physical impacts on their operations. In power [...] Read more.

In this paper, the cyber-security of smart microgrids is thoroughly discussed. In smart grids, the cyber system and physical process are tightly coupled. Due to the cyber system’s vulnerabilities, any cyber incidents can have economic and physical impacts on their operations. In power electronics-intensive smart microgrids, cyber-attacks can have much more harmful and devastating effects on their operation and stability due to low inertia, especially in islanded operation. In this paper, the cyber–physical systems in smart microgrids are briefly studied. Then, the cyber-attacks on data availability, integrity, and confidentiality are discussed. Since a false data injection (FDI) attack that compromises the data integrity in the cyber/communication network is one of the most challenging threats for smart microgrids, it is investigated in detail in this paper. Such FDI attacks can target state estimation, voltage and frequency control, and smart microgrids’ protection systems. The economic and physical/technical impacts of the FDI attacks on smart microgrids are also reviewed in this paper. The defensive strategies against FDI attacks are classified into protection strategies, in which selected meter measurements are protected, and detection/mitigation strategies, based on either static or dynamic detection. In this paper, implementation examples of FDI attacks’ construction and detection/mitigation in smart microgrids are provided. Samples of recent cyber-security projects in the world, and critical cyber-security standards of smart grids, are presented. Finally, future trends of cyber-security in smart microgrids are discussed. Full article

(This article belongs to the Special Issue Microgrids and Fault-Tolerant Control)

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35 pages, 15183 KiB

Open AccessEditor’s ChoiceReview

Power Quality Phenomena in Electric Railway Power Supply Systems: An Exhaustive Framework and Classification

by Hamed Jafari Kaleybar, Morris Brenna, Federica Foiadelli, Seyed Saeed Fazel and Dario Zaninelli

Energies 2020, 13(24), 6662; https://doi.org/10.3390/en13246662 - 17 Dec 2020

Cited by 64 | Viewed by 7327

Abstract

Electric railway power systems (ERPS) as one of the most critical and high-power end-user loads of utility grids are characterized by outlandish power quality (PQ) problems all over the world. The extension and evolution of different supply topologies for these systems has resulted [...] Read more.

Electric railway power systems (ERPS) as one of the most critical and high-power end-user loads of utility grids are characterized by outlandish power quality (PQ) problems all over the world. The extension and evolution of different supply topologies for these systems has resulted in significant and various forms of distortions in network voltage and current in all ERPS, the connected power system, and adjacent consumers. During the last years, numerous studies have been offered to investigate various aspects of PQs in a specific supplying topology. Variation in the supply structure of the ERPS and different types of locomotives has propelled the observation of different PQ phenomena. This versatility and development have led to confront considerable types of two-way interactive interfaces as well as reliability and PQ problems in ERPS. In addition, the lack of standards explicitly dedicated to ERPS has added to the ambiguity and complexity of this issue. In this paper, an extensive review of PQ distortions and phenomena in different configurations of ERPS is proposed and a systematic classification is presented. More than 140 scientific papers and publications are studied and categorized which can provide a fast review and a perfect perspective on the status of PQ indexes for researchers and experts. Full article

(This article belongs to the Special Issue Power Quality in Electrified Transportation Systems)

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31 pages, 4824 KiB

Open AccessEditor’s ChoiceArticle

Studying the Level of Sustainable Energy Development of the European Union Countries and Their Similarity Based on the Economic and Demographic Potential

by Magdalena Tutak, Jarosław Brodny, Dominika Siwiec, Robert Ulewicz and Peter Bindzár

Energies 2020, 13(24), 6643; https://doi.org/10.3390/en13246643 - 16 Dec 2020

Cited by 74 | Viewed by 5316

Abstract

The concept of sustainable economic development takes into account economic, social and environmental aspects and strives to achieve balance between them. One of the basic areas where it is required to revalue the current views on sustainable development is energy. The growing public [...] Read more.

The concept of sustainable economic development takes into account economic, social and environmental aspects and strives to achieve balance between them. One of the basic areas where it is required to revalue the current views on sustainable development is energy. The growing public awareness of environmental protection forces changes in this industry. Despite the global nature of this problem, its solution is perceived differently in various regions of the world. The unquestionable leader in introducing the idea of sustainable development economy is the European Union, where the energy sector is of key importance for the effectiveness of this process. In order to assess the sustainable energy development of the European Union countries, studies were conducted based on 13 selected indicators characterizing this sector in terms of energy, economy and environment. In order to assess the specificity of the European Union countries, these indicators were additionally compared to the gross domestic product value and the number of inhabitants of individual countries. For these cases, multi-criteria analyses were carried out using the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method. It allowed the authors to rank the European Union countries in terms of their adaptation to a sustainable energy economy. Based on the determined values of indicators versus the gross domestic product and the number of inhabitants of the countries in question, these countries were also divided into similar groups with the use of the Kohonen artificial neural networks. These groups can pursue a common energy policy in the field of sustainable development. The aim of the research was to present a new approach to the assessment of sustainable energy development of the European Union countries. The extensive ratio analysis (13 indicators of the sustainable energy development), including the economic and demographic potential of individual countries, and the use of modern tools made it possible to acquire new knowledge in the field of sustainable energy development in the European Union countries. The results should be utilized for more effective sustainable energy development of the European Union countries. Full article

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

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23 pages, 7126 KiB

Open AccessEditor’s ChoiceReview

A Review on Deep Learning Models for Forecasting Time Series Data of Solar Irradiance and Photovoltaic Power

by Rial A. Rajagukguk, Raden A. A. Ramadhan and Hyun-Jin Lee

Energies 2020, 13(24), 6623; https://doi.org/10.3390/en13246623 - 15 Dec 2020

Cited by 190 | Viewed by 11912

Abstract

Presently, deep learning models are an alternative solution for predicting solar energy because of their accuracy. The present study reviews deep learning models for handling time-series data to predict solar irradiance and photovoltaic (PV) power. We selected three standalone models and one hybrid [...] Read more.

Presently, deep learning models are an alternative solution for predicting solar energy because of their accuracy. The present study reviews deep learning models for handling time-series data to predict solar irradiance and photovoltaic (PV) power. We selected three standalone models and one hybrid model for the discussion, namely, recurrent neural network (RNN), long short-term memory (LSTM), gated recurrent unit (GRU), and convolutional neural network-LSTM (CNN–LSTM). The selected models were compared based on the accuracy, input data, forecasting horizon, type of season and weather, and training time. The performance analysis shows that these models have their strengths and limitations in different conditions. Generally, for standalone models, LSTM shows the best performance regarding the root-mean-square error evaluation metric (RMSE). On the other hand, the hybrid model (CNN–LSTM) outperforms the three standalone models, although it requires longer training data time. The most significant finding is that the deep learning models of interest are more suitable for predicting solar irradiance and PV power than other conventional machine learning models. Additionally, we recommend using the relative RMSE as the representative evaluation metric to facilitate accuracy comparison between studies. Full article

(This article belongs to the Section A2: Solar Energy and Photovoltaic Systems)

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15 pages, 5142 KiB

Open AccessEditor’s ChoiceArticle

Forecasting Photovoltaic Power Generation Using Satellite Images

by Dukhwan Yu, Seowoo Lee, Sangwon Lee, Wonik Choi and Ling Liu

Energies 2020, 13(24), 6603; https://doi.org/10.3390/en13246603 - 14 Dec 2020

Cited by 25 | Viewed by 4164

Abstract

As the relative importance of renewable energy in electric power systems increases, the prediction of photovoltaic (PV) power generation has become a crucial technology, for improving stability in the operation of next-generation power systems, such as microgrid and virtual power plants (VPP). In [...] Read more.

As the relative importance of renewable energy in electric power systems increases, the prediction of photovoltaic (PV) power generation has become a crucial technology, for improving stability in the operation of next-generation power systems, such as microgrid and virtual power plants (VPP). In order to improve the accuracy of PV power generation forecasting, a fair amount of research has been applied to weather forecast data (to a learning process). Despite these efforts, the problems of forecasting PV power generation remains challenging since existing methods show limited accuracy due to inappropriate cloud amount forecast data, which are strongly correlated with PV power generation. To address this problem, we propose a PV power forecasting model, including a cloud amount forecasting network trained with satellite images. In addition, our proposed model adopts convolutional self-attention to effectively capture historical features, and thus acquire helpful information from weather forecasts. To show the efficacy of the proposed cloud amount forecast network, we conduct extensive experiments on PV power generation forecasting with and without the cloud amount forecast network. The experimental results show that the Mean Absolute Percentage Error (MAPE) of our proposed prediction model, combined with the cloud amount forecast network, are reduced by 22.5% compared to the model without the cloud amount forecast network. Full article

(This article belongs to the Special Issue Emerging Technologies and Advanced Controls in Renewable-Energy-Based Power Generation Systems)

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13 pages, 3078 KiB

Open AccessEditor’s ChoiceArticle

Towards 100 Positive Energy Districts in Europe: Preliminary Data Analysis of 61 European Cases

by Silvia Bossi, Christoph Gollner and Sarah Theierling

Energies 2020, 13(22), 6083; https://doi.org/10.3390/en13226083 - 20 Nov 2020

Cited by 91 | Viewed by 5677

Abstract

Positive Energy Districts and Neighborhoods (PEDs) are seen as a promising pathway towards sustainable urban areas. Several cities have already taken up such PED-related developments. To support such approaches, European countries joined forces to achieve 100 PEDs until 2025 through a comprehensive research [...] Read more.

Positive Energy Districts and Neighborhoods (PEDs) are seen as a promising pathway towards sustainable urban areas. Several cities have already taken up such PED-related developments. To support such approaches, European countries joined forces to achieve 100 PEDs until 2025 through a comprehensive research and innovation program. A solid understanding and consideration of cities’ strategies, experiences and project features serve as the basis for developing and designing the PED program. JPI Urban Europe has been collecting information on projects towards sustainable urbanization and the energy transition across Europe. The collected cases are summarized in a PED Booklet whose update was recently published on the JPI Urban Europe website. Results presented in this paper provide insights from the analysis of 61 projects in Europe and offer recommendations for future PED developments. Full article

(This article belongs to the Special Issue Smart Cities and Positive Energy Districts: Urban Perspectives in 2020)

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23 pages, 11965 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Potential Liquid-Organic Hydrogen Carrier (LOHC) Systems: A Review on Recent Progress

by Purna Chandra Rao and Minyoung Yoon

Energies 2020, 13(22), 6040; https://doi.org/10.3390/en13226040 - 19 Nov 2020

Cited by 251 | Viewed by 24777

Abstract

The depletion of fossil fuels and rising global warming challenges encourage to find safe and viable energy storage and delivery technologies. Hydrogen is a clean, efficient energy carrier in various mobile fuel-cell applications and owned no adverse effects on the environment and human [...] Read more.

The depletion of fossil fuels and rising global warming challenges encourage to find safe and viable energy storage and delivery technologies. Hydrogen is a clean, efficient energy carrier in various mobile fuel-cell applications and owned no adverse effects on the environment and human health. However, hydrogen storage is considered a bottleneck problem for the progress of the hydrogen economy. Liquid-organic hydrogen carriers (LOHCs) are organic substances in liquid or semi-solid states that store hydrogen by catalytic hydrogenation and dehydrogenation processes over multiple cycles and may support a future hydrogen economy. Remarkably, hydrogen storage in LOHC systems has attracted dramatically more attention than conventional storage systems, such as high-pressure compression, liquefaction, and absorption/adsorption techniques. Potential LOHC media must provide fully reversible hydrogen storage via catalytic processes, thermal stability, low melting points, favorable hydrogenation thermodynamics and kinetics, large-scale availability, and compatibility with current fuel energy infrastructure to practically employ these molecules in various applications. In this review, we present various considerable aspects for the development of ideal LOHC systems. We highlight the recent progress of LOHC candidates and their catalytic approach, as well as briefly discuss the theoretical insights for understanding the reaction mechanism. Full article

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

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36 pages, 1010 KiB

Open AccessEditor’s ChoiceArticle

Greenhouse Gases and Circular Economy Issues in Sustainability Reports from the Energy Sector in the European Union

by Agnieszka Janik, Adam Ryszko and Marek Szafraniec

Energies 2020, 13(22), 5993; https://doi.org/10.3390/en13225993 - 17 Nov 2020

Cited by 53 | Viewed by 6711

Abstract

The achievement of climate neutrality and eco-economic decoupling requires explicit measures to reduce greenhouse gases (GHG) emissions and to implement circular economy (CE) principles in practice. The energy sector is of particular importance in meeting these challenges because it exerts a substantial environmental [...] Read more.

The achievement of climate neutrality and eco-economic decoupling requires explicit measures to reduce greenhouse gases (GHG) emissions and to implement circular economy (CE) principles in practice. The energy sector is of particular importance in meeting these challenges because it exerts a substantial environmental impact. Therefore, it is extremely important to determine how essential GHG and CE issues are for companies operating in the energy sector. This can be reflected in corporate strategies, but it can also be disclosed to the public in sustainability reports. For this reason, this article presents a comprehensive analysis of sustainability reports based on the latest GRI Standards published by companies representing the energy sector in the European Union to determine the existence, quality, and specificity of reporting GHG and CE issues. The research results demonstrate that sustainability reports from the energy sector companies tend to focus more on GHG issues. They rarely point to actions related to CE, including actions enabling a reduction in GHG emissions, as those with high priority. In addition, declarations from the analyzed companies regarding intentions related to GHG and CE issues at the strategic level find a rather poor reflection in the description of specific actions in this area or in demonstrating appropriate indicators at the operational level. Considering the indicators included in the reports, the analyzed companies insufficiently describe the methods they use to gather, compile, and analyze information on the effectiveness of actions taken to address GHG and CE issues. As for the identification of potential determinants of the quality of reporting GHG and CE issues, the research results indicate that it is mostly influenced by external assurance and the report option. Sustainability reports submitted for external assurance and reports with the comprehensive option are significantly more developed than other types of reports. However, the clarity of reports with the core option is higher compared to the comprehensive group. In addition, it was indicated that the clarity of stand-alone reports is higher compared to other types of reports. Full article

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

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23 pages, 3062 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Thermochemical Energy Storage via Solid–Gas Reversible Reactions at High Temperature

by Laurie André and Stéphane Abanades

Energies 2020, 13(22), 5859; https://doi.org/10.3390/en13225859 - 10 Nov 2020

Cited by 67 | Viewed by 6657

Abstract

The exploitation of solar energy, an unlimited and renewable energy resource, is of prime interest to support the replacement of fossil fuels by renewable energy alternatives. Solar energy can be used via concentrated solar power (CSP) combined with thermochemical energy storage (TCES) for [...] Read more.

The exploitation of solar energy, an unlimited and renewable energy resource, is of prime interest to support the replacement of fossil fuels by renewable energy alternatives. Solar energy can be used via concentrated solar power (CSP) combined with thermochemical energy storage (TCES) for the conversion and storage of concentrated solar energy via reversible solid–gas reactions, thus enabling round the clock operation and continuous production. Research is on-going on efficient and economically attractive TCES systems at high temperatures with long-term durability and performance stability. Indeed, the cycling stability with reduced or no loss in capacity over many cycles of heat charge and discharge of the material is pursued. The main thermochemical systems currently investigated are encompassing metal oxide redox pairs (MO_x/MO_x−1), non-stoichiometric perovskites (ABO₃/ABO_3−δ), alkaline earth metal carbonates and hydroxides (MCO₃/MO, M(OH)₂/MO with M = Ca, Sr, Ba). The metal oxides/perovskites can operate in open loop with air as the heat transfer fluid, while carbonates and hydroxides generally require closed loop operation with storage of the fluid (H₂O or CO₂). Alternative sources of natural components are also attracting interest, such as abundant and low-cost ore minerals or recycling waste. For example, limestone and dolomite are being studied to provide for one of the most promising systems, CaCO₃/CaO. Systems based on hydroxides are also progressing, although most of the recent works focused on Ca(OH)₂/CaO. Mixed metal oxides and perovskites are also largely developed and attractive materials, thanks to the possible tuning of both their operating temperature and energy storage capacity. The shape of the material and its stabilization are critical to adapt the material for their integration in reactors, such as packed bed and fluidized bed reactors, and assure a smooth transition for commercial use and development. The recent advances in TCES systems since 2016 are reviewed, and their integration in solar processes for continuous operation is particularly emphasized. Full article

(This article belongs to the Special Issue Development in Thermochemical Energy Storage)

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28 pages, 3457 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Polymer Electrolyte Fuel Cell Degradation Mechanisms and Their Diagnosis by Frequency Response Analysis Methods: A Review

by Antonio Sorrentino, Kai Sundmacher and Tanja Vidakovic-Koch

Energies 2020, 13(21), 5825; https://doi.org/10.3390/en13215825 - 8 Nov 2020

Cited by 52 | Viewed by 6916

Abstract

Several experimental techniques involving dynamic electrical variables are used to study the complex behaviour of polymer electrolyte membrane fuel cells in order to improve performance and durability. Among them, electrochemical impedance spectroscopy (EIS) is one of the most employed methods. Like any frequency [...] Read more.

Several experimental techniques involving dynamic electrical variables are used to study the complex behaviour of polymer electrolyte membrane fuel cells in order to improve performance and durability. Among them, electrochemical impedance spectroscopy (EIS) is one of the most employed methods. Like any frequency response analysis (FRA) methodology, EIS enables one to separate the contribution of many processes to performance losses. However, it fails to identify processes with a similar time constant and the interpretation of EIS spectra is often ambiguous. In the last decade, alternative FRA methodologies based on non-electrical inputs and/or outputs have been developed. These studies were mainly driven by requirements for a better diagnosis of polymer electrolyte membrane fuel cells (PEMFCs) faulty operation conditions as well as better component and material design. In this contribution, a state-of-the-art EIS and novel FRA techniques for PEMFC diagnosis are summarised. First, common degradation mechanisms and their causes are discussed. A mathematical framework based on linear system theory of time invariant systems is described in order to explain the theoretical implications of the use of different input/output configurations. In relation to this, the concepts and potential are depicted as well as the problematic aspects and future prospective of these diagnostic approaches. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membrane Fuel Cell Systems)

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21 pages, 3048 KiB

Open AccessEditor’s ChoiceArticle

Analysis of Wind Turbine Aging through Operation Curves

by Davide Astolfi, Raymond Byrne and Francesco Castellani

Energies 2020, 13(21), 5623; https://doi.org/10.3390/en13215623 - 27 Oct 2020

Cited by 29 | Viewed by 3995

Abstract

The worsening with age of technical systems performance is a matter of fact which is particularly timely to analyze for horizontal-axis wind turbines because they constitute a mature technology. On these grounds, the present study deals with the assessment of wind turbine performance [...] Read more.

The worsening with age of technical systems performance is a matter of fact which is particularly timely to analyze for horizontal-axis wind turbines because they constitute a mature technology. On these grounds, the present study deals with the assessment of wind turbine performance decline with age. The selected test case is a Vestas V52 wind turbine, installed in 2005 at the Dundalk Institute of Technology campus in Ireland. Operation data from 2008 to 2019 have been used for this study. The general idea is analyzing the appropriate operation curves for each working region of the wind turbine: in Region 2 (wind speed between 5 and 9 m/s), the generator speed–power curve is studied, because the wind turbine operates at fixed pitch. In Region 2

\frac{1}{2}

(wind speed between 9 and 13 m/s), the generator speed is rated and the pitch control is relevant: therefore, the pitch angle–power curve is analyzed. Using a support vector regression for the operation curves of interest, it is observed that in Region 2, a progressive degradation occurs as regards the power extracted for given generator speed, and after ten years (from 2008 to 2018), the average production has diminished of the order of 8%. In Region 2

\frac{1}{2}

, the performance decline with age is less regular and, after ten years of operation, the performance has diminished averagely of the 1.3%. The gearbox of the test case wind turbine was substituted with a brand new one at the end of 2018, and it results that the performance in Region 2

\frac{1}{2}

has considerably improved after the gearbox replacement (+3% in 2019 with respect to 2018, +1.7% with respect to 2008), while in Region 2, an improvement is observed (+1.9% in 2019 with respect to 2018) which does not compensate the ten-year period decline (−6.5% in 2019 with respect to 2008). Therefore, the lesson is that for the test case wind turbine, the generator aging impacts remarkably on the power production in Region 2, while in Region 2

\frac{1}{2}

, the impact of the gearbox aging dominates over the generator aging; for this reason, wind turbine refurbishment or component replacement should be carefully considered on the grounds of the wind intensity distribution onsite. Full article

(This article belongs to the Special Issue Wind Turbine Monitoring through Operation Data Analysis)

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31 pages, 775 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Energy Harvesting towards Self-Powered IoT Devices

by Hassan Elahi, Khushboo Munir, Marco Eugeni, Sofiane Atek and Paolo Gaudenzi

Energies 2020, 13(21), 5528; https://doi.org/10.3390/en13215528 - 22 Oct 2020

Cited by 193 | Viewed by 13622

Abstract

The internet of things (IoT) manages a large infrastructure of web-enabled smart devices, small devices that use embedded systems, such as processors, sensors, and communication hardware to collect, send, and elaborate on data acquired from their environment. Thus, from a practical point of [...] Read more.

The internet of things (IoT) manages a large infrastructure of web-enabled smart devices, small devices that use embedded systems, such as processors, sensors, and communication hardware to collect, send, and elaborate on data acquired from their environment. Thus, from a practical point of view, such devices are composed of power-efficient storage, scalable, and lightweight nodes needing power and batteries to operate. From the above reason, it appears clear that energy harvesting plays an important role in increasing the efficiency and lifetime of IoT devices. Moreover, from acquiring energy by the surrounding operational environment, energy harvesting is important to make the IoT device network more sustainable from the environmental point of view. Different state-of-the-art energy harvesters based on mechanical, aeroelastic, wind, solar, radiofrequency, and pyroelectric mechanisms are discussed in this review article. To reduce the power consumption of the batteries, a vital role is played by power management integrated circuits (PMICs), which help to enhance the system’s life span. Moreover, PMICs from different manufacturers that provide power management to IoT devices have been discussed in this paper. Furthermore, the energy harvesting networks can expose themselves to prominent security issues putting the secrecy of the system to risk. These possible attacks are also discussed in this review article. Full article

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

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6 pages, 667 KiB

Open AccessEditor’s ChoicePerspective

The Green Versus Green Trap and a Way Forward

by Haris Doukas, Alexandros Nikas, Giorgos Stamtsis and Ioannis Tsipouridis

Energies 2020, 13(20), 5473; https://doi.org/10.3390/en13205473 - 20 Oct 2020

Cited by 18 | Viewed by 4908

Abstract

Massive deployment of renewables is considered as a decisive step in most countries’ climate efforts. However, at the local scale, it is also perceived by many as a threat to their rich and diverse natural environment. With this perspective, we argue that this [...] Read more.

Massive deployment of renewables is considered as a decisive step in most countries’ climate efforts. However, at the local scale, it is also perceived by many as a threat to their rich and diverse natural environment. With this perspective, we argue that this green versus green pseudo-dilemma highlights how crucial a broad societal buy-in is. New, transparent, participatory processes and mechanisms that are oriented toward social licensing can now be employed. A novel, integrative research agenda must orbit around co-creation to enable and promote resource co-management and co-ownership where possible, with increased consensus. Full article

(This article belongs to the Special Issue Sustainable Management of Energy Resources, Energy Strategies and Climate Change)

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23 pages, 7652 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Integration of Large-Scale Variable Renewable Energy Sources into the Future European Power System: On the Curtailment Challenge

by Chloi Syranidou, Jochen Linssen, Detlef Stolten and Martin Robinius

Energies 2020, 13(20), 5490; https://doi.org/10.3390/en13205490 - 20 Oct 2020

Cited by 23 | Viewed by 4322

Abstract

The future European power system is projected to rely heavily on variable renewable energy sources (VRES), primarily wind and solar generation. However, the difficulties inherent to storing the primary energy of these sources is expected to pose significant challenges in terms of their [...] Read more.

The future European power system is projected to rely heavily on variable renewable energy sources (VRES), primarily wind and solar generation. However, the difficulties inherent to storing the primary energy of these sources is expected to pose significant challenges in terms of their integration into the system. To account for the high variability of renewable energy sources VRES, a novel pan-European dispatch model with high spatio-temporal resolution including load shifting is introduced here, providing highly detailed information regarding renewable energy curtailments for all Europe, typically underestimated in studies of future systems. which also includes modeling of load shifting. The model consists of four separate levels with different approaches for modeling thermal generation flexibility, storage units and demand as well as with spatial resolutions and generation dispatch formulations. Applying the developed model for the future European power system follows the results of corresponding transmission expansion planning studies, which are translated into the desired high spatial resolution. The analysis of the “large scale-RES” scenario for 2050 shows considerable congestion between northern and central Europe, which constitutes the primary cause of VRES curtailments of renewables. In addition, load shifting is shown to mostly improve the integration of solar energy into the system and not wind, which constitutes the dominant energy source for this scenario. Finally, the analysis of the curtailments time series using ideal converters shows that the best locations for their exploitation can be found in western Ireland and western Denmark. Full article

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

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14 pages, 3859 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Mechanical Harvesting of Camelina: Work Productivity, Costs and Seed Loss Evaluation

by Walter Stefanoni, Francesco Latterini, Javier Prieto Ruiz, Simone Bergonzoli, Consuelo Attolico and Luigi Pari

Energies 2020, 13(20), 5329; https://doi.org/10.3390/en13205329 - 13 Oct 2020

Cited by 17 | Viewed by 4043

Abstract

Camelina is a low input crop than can be cultivated in rotation with cereals to provide vegetable oil suitable for bioenergy production, industrial applications and even as source of food for livestock. At large scale farming, camelina seeds are currently harvested using a [...] Read more.

Camelina is a low input crop than can be cultivated in rotation with cereals to provide vegetable oil suitable for bioenergy production, industrial applications and even as source of food for livestock. At large scale farming, camelina seeds are currently harvested using a combine harvester, equipped with a cereal header, but the literature still lacks the knowledge of the performance of the machine, the harvesting cost and the related loss of seeds. The present study aims to fulfill that gap by reporting the results obtained from an ad hoc harvest field test. Camelina seed yield was 0.95 Mg ha⁻¹ which accounted for the 18.60% of the total above ground biomass. Theoretical field capacity, effective field capacity and field efficiency were 3.38 ha h⁻¹, 3.17 ha h⁻¹ and 93.7% respectively, albeit the seed loss was 80.1 kg ha⁻¹ FM (7.82% w/w of the potential seed yield). The presence of material other than grain was rather high, 31.77% w/w, which implies a second step of cleaning to avoid undesired modification of the seed quality. Harvesting cost was estimated in 65.97 € ha⁻¹. Our findings provide evidence on the suitability to use a conventional combine harvester equipped with a cereal header for the harvesting of camelina seeds, although some improvements are required to reduce both seed loss and impurities. Full article

(This article belongs to the Special Issue Renewable Energy Production from Energy Crops and Agricultural Residues)

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30 pages, 6581 KiB

Open AccessEditor’s ChoiceArticle

Enhanced CH₄-CO₂ Hydrate Swapping in the Presence of Low Dosage Methanol

by Jyoti Shanker Pandey, Charilaos Karantonidis, Adam Paul Karcz and Nicolas von Solms

Energies 2020, 13(20), 5238; https://doi.org/10.3390/en13205238 - 9 Oct 2020

Cited by 39 | Viewed by 3962

Abstract

CO₂-rich gas injection into natural gas hydrate reservoirs is proposed as a carbon-neutral, novel technique to store CO₂ while simultaneously producing CH₄ gas from methane hydrate deposits without disturbing geological settings. This method is limited by the mass transport [...] Read more.

CO₂-rich gas injection into natural gas hydrate reservoirs is proposed as a carbon-neutral, novel technique to store CO₂ while simultaneously producing CH₄ gas from methane hydrate deposits without disturbing geological settings. This method is limited by the mass transport barrier created by hydrate film formation at the liquid–gas interface. The very low gas diffusivity through hydrate film formed at this interface causes low CO₂ availability at the gas–hydrate interface, thus lowering the recovery and replacement efficiency during CH₄-CO₂ exchange. In a first-of-its-kind study, we have demonstrate the successful application of low dosage methanol to enhance gas storage and recovery and compare it with water and other surface-active kinetic promoters including SDS and L-methionine. Our study shows 40–80% CH₄ recovery, 83–93% CO₂ storage and 3–10% CH₄-CO₂ replacement efficiency in the presence of 5 wt% methanol, and further improvement in the swapping process due to a change in temperature from 1–4 °C is observed. We also discuss the influence of initial water saturation (30–66%), hydrate morphology (grain-coating and pore-filling) and hydrate surface area on the CH₄-CO₂ hydrate swapping. Very distinctive behavior in methane recovery caused by initial water saturation (above and below S_wi = 0.35) and hydrate morphology is also discussed. Improved CO₂ storage and methane recovery in the presence of methanol is attributed to its dual role as anti-agglomerate and thermodynamic driving force enhancer between CH₄-CO₂ hydrate phase boundaries when methanol is used at a low concentration (5 wt%). The findings of this study can be useful in exploring the usage of low dosage, bio-friendly, anti-agglomerate and hydrate inhibition compounds in improving CH₄ recovery and storing CO₂ in hydrate reservoirs without disturbing geological formation. To the best of the authors’ knowledge, this is the first experimental study to explore the novel application of an anti-agglomerate and hydrate inhibitor in low dosage to address the CO₂ hydrate mass transfer barrier created at the gas–liquid interface to enhance CH₄-CO₂ hydrate exchange. Our study also highlights the importance of prior information about methane hydrate reservoirs, such as residual water saturation, degree of hydrate saturation and hydrate morphology, before applying the CH₄-CO₂ hydrate swapping technique. Full article

(This article belongs to the Special Issue CO₂ Capture, Storage, Utilisation and Sequestration and Hydrocarbon Extraction)

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29 pages, 2495 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Technology, Strategy and Application of Sustainable Energy Systems

by Wenxiao Chu, Francesco Calise, Neven Duić, Poul Alberg Østergaard, Maria Vicidomini and Qiuwang Wang

Energies 2020, 13(19), 5229; https://doi.org/10.3390/en13195229 - 8 Oct 2020

Cited by 33 | Viewed by 10603

Abstract

The global COVID-19 pandemic has had strong impacts on national and international freight, construction and tourism industry, supply chains, and has resulted in a rapid decline in the demand for traditional energy sources. In fact, research has outlined that urban areas depend on [...] Read more.

The global COVID-19 pandemic has had strong impacts on national and international freight, construction and tourism industry, supply chains, and has resulted in a rapid decline in the demand for traditional energy sources. In fact, research has outlined that urban areas depend on global supply chains for their day-to-day basic functions, including energy supplies, food and safe access to potable water. The disruption of global supply chains can leave many urban areas in a very vulnerable position, in which their citizens may struggle to obtain their basic supplies, as the COVID-19 crisis has recently shown. Therefore, solutions aiming to enhance local food, water and energy production systems, even in urban environments, have to be pursued. The COVID-19 crisis has also highlighted in the scientific community the problem of people’s exposure to outdoor and indoor pollution, confirmed as a key element for the increase both in the transmission and severity of the contagion, on top of involving health risks on their own. In this context, most nations are going to adopt new preferential policies to stimulate the development of relevant sustainable energy industries, based on the electrification of the systems supplied by renewable energy sources as confirmed by the International Energy Agency (IEA). Thus, while there is ongoing research focusing on a COVID 19 vaccine, there is also a need for researchers to work cooperatively on novel strategies for world economic recovery incorporating renewable energy policy, technology and management. In this framework, the Sustainable Development of Energy, Water and Environment Systems (SDEWES) conference provides a good platform for researchers and other experts to exchange their academic thoughts, promoting the development and improvements on the renewable energy technologies as well as their role in systems and in the transition towards sustainable energy systems. The 14th SDEWES Conference was held in Dubrovnik, Croatia. It brought together around 570 researchers from 55 countries in the field of sustainable development. The present Special Issue of Energies, specifically dedicated to the 14th SDEWES Conference, focuses on four main fields: energy policy for sustainable development, biomass energy application, building energy saving, and power plant and electric systems. Full article

(This article belongs to the Special Issue Selected Papers from SDEWES 2019 conferences on Sustainable Development of Energy, Water and Environment Systems)

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38 pages, 4240 KiB

Open AccessEditor’s ChoiceArticle

Micro Nuclear Reactors: Potential Replacements for Diesel Gensets within Micro Energy Grids

by Hossam A. Gabbar, Muhammad R. Abdussami and Md. Ibrahim Adham

Energies 2020, 13(19), 5172; https://doi.org/10.3390/en13195172 - 5 Oct 2020

Cited by 17 | Viewed by 4180

Abstract

Resilient operation of medium/large scale off-grid energy systems, which is a key challenge for energy crisis solutions, requires continuous and sustainable energy resources. Conventionally, micro energy grids (MEGs) are adopted to supply electricity and thermal energy simultaneously. Fossil-fired gensets, such as diesel generators, [...] Read more.

Resilient operation of medium/large scale off-grid energy systems, which is a key challenge for energy crisis solutions, requires continuous and sustainable energy resources. Conventionally, micro energy grids (MEGs) are adopted to supply electricity and thermal energy simultaneously. Fossil-fired gensets, such as diesel generators, are indispensable components for off-grid MEGs due to the intermittent nature of renewable energy sources (RESs). However, fossil-fired gensets emit a significant amount of greenhouse gases (GHGs). Therefore, this study investigates an alternative source as an economical and environmental replacement for diesel gensets that can reduce GHG emissions and ensure system reliability. A MEG is developed in this paper to support a considerably large-scale electric and thermal demand at Ontario Tech University (UOIT). Different sizes of diesel gensets and RESs, such as solar, wind, hydro, and biomass, are combined in the MEG for off-grid applications. To evaluate diesel gensets’ competency, the diesel genset is substituted by an emission-free generation source named microreactor (MR). The fossil-fired MEG and MR-based MEG are optimized by an intelligent optimization technique, namely particle swarm optimization (PSO). The objective of the PSO is to minimize the net present cost (NPC). The simulation results show that MR-based MEG could be an excellent replacement for a diesel genset in terms of NPC and selected key performance indicators (KPIs). A comprehensive sensitivity analysis is also carried out to validate the simulation results. Full article

(This article belongs to the Special Issue Nuclear Power, including Fission and Fusion Technologies 2021)

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16 pages, 4239 KiB

Open AccessEditor’s ChoiceArticle

Does the Balance Exist between Cost Efficiency of Different Energy Efficiency Measures? DH Systems Case

by Ieva Pakere, Dace Lauka and Dagnija Blumberga

Energies 2020, 13(19), 5151; https://doi.org/10.3390/en13195151 - 2 Oct 2020

Cited by 12 | Viewed by 2495

Abstract

The main aim of this study is to evaluate the results achieved by implementation of different support policies in form of subsidies for energy efficiency improvements and transition to renewable energy sources. The article compares the energy efficiency measures in district heating systems [...] Read more.

The main aim of this study is to evaluate the results achieved by implementation of different support policies in form of subsidies for energy efficiency improvements and transition to renewable energy sources. The article compares the energy efficiency measures in district heating systems with other support program. In order to assess the effectiveness of implementation of different renewable energy technologies and energy efficiency projects, the levelized costs of saved energy for different support programs were determined. Authors compared different co-financed projects related to replacement of fossil fuel energy sources in district heating (mainly to biomass) and the installation of new biomass boilers, heat pumps, solar collectors and other local technologies in municipal buildings. Results show that financial support for energy efficiency measures in industrial enterprises and district heating systems has been most cost-effective, mainly due to the low co-financing rate (30%) and the high potential for energy savings in different production processes. Authors have identified the blind-spots within the funding allocation for different municipalities, which is not always dedicated to achieved energy savings. Full article

(This article belongs to the Special Issue Recent Studies in District Heating and Cooling Systems)

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18 pages, 838 KiB

Open AccessEditor’s ChoiceArticle

Impact of COVID-19 on the Level of Energy Poverty in Poland

by Rafal Nagaj and Jaroslaw Korpysa

Energies 2020, 13(18), 4977; https://doi.org/10.3390/en13184977 - 22 Sep 2020

Cited by 52 | Viewed by 5447

Abstract

The main objective of the paper is to determine the impact of the COVID-19 pandemic on the level of energy poverty in Poland. In order to achieve such a goal, the first part of the article presents the definition of energy poverty and [...] Read more.

The main objective of the paper is to determine the impact of the COVID-19 pandemic on the level of energy poverty in Poland. In order to achieve such a goal, the first part of the article presents the definition of energy poverty and the nature of its measures, as well as the determinants and policies of the state addressing the issue of energy poverty mitigation. In the second part of the paper, the results of research into the level of energy poverty are analyzed and the variables affecting energy poverty in Poland during the pandemic are determined. It was established on the basis of these results that the present pandemic contributed to the aggravation of financial difficulties in Polish households with regard to financing expenditure on energy carriers. It was found that COVID-19 had a negative impact on the average disposable income of Polish households, which, with the increase in prices and expenditure on energy carriers, led to an increase in the proportion of disposable income spent on energy carriers. The most affected have been the poorest households. Moreover, the long downward trend in the level of energy poverty in Poland has reversed. Thus, it has been proved that COVID-19 has contributed to the intensification of energy poverty in Poland. The theoretical and empirical considerations contained in this paper may be a valuable source of scientific data on the impact of the pandemic on household energy poverty, while public institutions may find them a source of useful information, helping to create effective instruments to mitigate energy poverty in the Polish economy. Full article

(This article belongs to the Special Issue Management and Technology for Energy Efficiency Development)

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18 pages, 12644 KiB

Open AccessEditor’s ChoiceArticle

Parametric Design to Maximize Solar Irradiation and Minimize the Embodied GHG Emissions for a ZEB in Nordic and Mediterranean Climate Zones

by Mattia Manni, Gabriele Lobaccaro, Nicola Lolli and Rolf Andre Bohne

Energies 2020, 13(18), 4981; https://doi.org/10.3390/en13184981 - 22 Sep 2020

Cited by 27 | Viewed by 3921

Abstract

This work presents a validated workflow based on an algorithm developed in Grasshopper to parametrically control the building’s shape, by maximizing the solar irradiation incident on the building envelope and minimizing the embodied emissions. The algorithm is applied to a zero-emission building concept [...] Read more.

This work presents a validated workflow based on an algorithm developed in Grasshopper to parametrically control the building’s shape, by maximizing the solar irradiation incident on the building envelope and minimizing the embodied emissions. The algorithm is applied to a zero-emission building concept in Nordic and Mediterranean climate zones. The algorithm enables conducting both energy and environmental assessments through Ladybug tools. The emissions embodied in materials and the solar irradiation incident on the building envelope were estimated in the early design stage. A three-steps optimization process through evolutionary solvers, such as Galapagos (one-objective) and Octopus (multi-objective), has been conducted to shape the most environmentally responsive ZEB model in both climates. The results demonstrated the replicability of the algorithm to optimize the solar irradiation by producing an increment of solar incident irradiation equal to 35% in the Mediterranean area, and to 20% in the Nordic climate. This could contribute to compensate the additional 15% of emissions due to the higher quantities of employed materials in the optimized design. The developed approach, which is based on the parametric design principles for ZEBs, represents a support instrument for designers to develop highly efficient energy solutions in the early design stages. Full article

(This article belongs to the Special Issue Life Cycle Thinking for a Sustainable Built Environment)

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28 pages, 4766 KiB

Open AccessEditor’s ChoiceReview

Graphene and Lithium-Based Battery Electrodes: A Review of Recent Literature

by Luca Lavagna, Giuseppina Meligrana, Claudio Gerbaldi, Alberto Tagliaferro and Mattia Bartoli

Energies 2020, 13(18), 4867; https://doi.org/10.3390/en13184867 - 17 Sep 2020

Cited by 49 | Viewed by 8107

Abstract

Graphene is a new generation material, which finds potential and practical applications in a vast range of research areas. It has unrivalled characteristics, chiefly in terms of electronic conductivity, mechanical robustness and large surface area, which allow the attainment of outstanding performances in [...] Read more.

Graphene is a new generation material, which finds potential and practical applications in a vast range of research areas. It has unrivalled characteristics, chiefly in terms of electronic conductivity, mechanical robustness and large surface area, which allow the attainment of outstanding performances in the material science field. Some unneglectable issues, such as the high cost of production at high quality and corresponding scarce availability in large amounts necessary for mass scale distribution, slow down graphene widespread utilization; however, in the last decade both basic academic and applied industrial materials research have achieved remarkable breakthroughs thanks to the implementation of graphene and related 1D derivatives. In this work, after briefly recalling the main characteristics of graphene, we present an extensive overview of the most recent advances in the development of the Li-ion battery anodes granted by the use of neat and engineered graphene and related 1D materials. Being far from totally exhaustive, due to the immense scientific production in the field yearly, we chiefly focus here on the role of graphene in materials modification for performance enhancement in both half and full lithium-based cells and give some insights on related promising perspectives. Full article

(This article belongs to the Special Issue Organic/Inorganic Hybrid Materials for Fuel Cells and Advanced Batteries)

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34 pages, 1312 KiB

Open AccessEditor’s ChoiceReview

Review on the PV Hosting Capacity in Distribution Networks

by Samar Fatima, Verner Püvi and Matti Lehtonen

Energies 2020, 13(18), 4756; https://doi.org/10.3390/en13184756 - 11 Sep 2020

Cited by 88 | Viewed by 8652

Abstract

The increasing penetration of Photovoltaic (PV) generation results in challenges regarding network operation, management and planning. Correspondingly, Distribution Network Operators (DNOs) are in the need of totally new understanding. The establishment of comprehensive standards for maximum PV integration into the network, without adversely [...] Read more.

The increasing penetration of Photovoltaic (PV) generation results in challenges regarding network operation, management and planning. Correspondingly, Distribution Network Operators (DNOs) are in the need of totally new understanding. The establishment of comprehensive standards for maximum PV integration into the network, without adversely impacting the normal operating conditions, is also needed. This review article provides an extensive review of the Hosting Capacity (HC) definitions based on different references and estimated HC with actual figures in different geographical areas and network conditions. Moreover, a comprehensive review of limiting factors and improvement methods for HC is presented along with voltage rise limits of different countries under PV integration. Peak load is the major reference used for HC definition and the prime limiting constraint for PV HC is the voltage violations. However, the varying definitions in different references lead to the conclusion that, neither the reference values nor the limiting factors are unique values and HC can alter depending on the reference, network conditions, topology, location, and PV deployment scenario. Full article

(This article belongs to the Special Issue Emerging Photovoltaic Technology in Northern Europe)

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26 pages, 13705 KiB

Open AccessEditor’s ChoiceArticle

Development of a Variable Valve Actuation Control to Improve Diesel Oxidation Catalyst Efficiency and Emissions in a Light Duty Diesel Engine

by José R. Serrano, Francisco J. Arnau, Jaime Martín and Ángel Auñón

Energies 2020, 13(17), 4561; https://doi.org/10.3390/en13174561 - 3 Sep 2020

Cited by 11 | Viewed by 5047

Abstract

Growing interest has arisen to adopt Variable Valve Timing (VVT) technology for automotive engines due to the need to fulfill the pollutant emission regulations. Several VVT strategies, such as the exhaust re-opening and the late exhaust closing, can be used to achieve an [...] Read more.

Growing interest has arisen to adopt Variable Valve Timing (VVT) technology for automotive engines due to the need to fulfill the pollutant emission regulations. Several VVT strategies, such as the exhaust re-opening and the late exhaust closing, can be used to achieve an increment in the after-treatment upstream temperature by increasing the residual gas amount. In this study, a one-dimensional gas dynamics engine model has been used to simulate several VVT strategies and develop a control system to actuate over the valves timing in order to increase diesel oxidation catalyst efficiency and reduce the exhaust pollutant emissions. A transient operating conditions comparison, taking the Worldwide Harmonized Light-Duty Vehicles Test Cycle (WLTC) as a reference, has been done by analyzing fuel economy, HC and CO pollutant emissions levels. The results conclude that the combination of an early exhaust and a late intake valve events leads to a 20% reduction in CO emissions with a fuel penalty of 6% over the low speed stage of the WLTC, during the warm-up of the oxidation catalyst. The same set-up is able to reduce HC emissions down to 16% and NO_x emission by 13%. Full article

(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)

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17 pages, 852 KiB

Open AccessEditor’s ChoiceArticle

The Role of Hydrogen in Achieving Long Term Japanese Energy System Goals

by Anshuman Chaube, Andrew Chapman, Yosuke Shigetomi, Kathryn Huff and James Stubbins

Energies 2020, 13(17), 4539; https://doi.org/10.3390/en13174539 - 2 Sep 2020

Cited by 55 | Viewed by 6809

Abstract

This research qualitatively reviews literature regarding energy system modeling in Japan specific to the future hydrogen economy, leveraging quantitative model outcomes to establish the potential future deployment of hydrogen in Japan. The analysis focuses on the four key sectors of storage, supplementing the [...] Read more.

This research qualitatively reviews literature regarding energy system modeling in Japan specific to the future hydrogen economy, leveraging quantitative model outcomes to establish the potential future deployment of hydrogen in Japan. The analysis focuses on the four key sectors of storage, supplementing the gas grid, power generation, and transportation, detailing the potential range of hydrogen technologies which are expected to penetrate Japanese energy markets up to 2050 and beyond. Alongside key model outcomes, the appropriate policy settings, governance and market mechanisms are described which underpin the potential hydrogen economy future for Japan. We find that transportation, gas grid supplementation, and storage end-uses may emerge in significant quantities due to policies which encourage ambitious implementation targets, investment in technologies and research and development, and the emergence of a future carbon pricing regime. On the other hand, for Japan which will initially be dependent on imported hydrogen, the cost of imports appears critical to the emergence of broad hydrogen usage, particularly in the power generation sector. Further, the consideration of demographics in Japan, recognizing the aging, shrinking population and peoples’ energy use preferences will likely be instrumental in realizing a smooth transition toward a hydrogen economy. Full article

(This article belongs to the Special Issue Governance Strategies and Insights to Accelerate the Production and Diffusion of Hydrogen and Fuel-Cell Technologies)

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14 pages, 352 KiB

Open AccessEditor’s ChoiceArticle

Intraday Electricity Pricing of Night Contracts

by Marcel Kremer, Rüdiger Kiesel and Florentina Paraschiv

Energies 2020, 13(17), 4501; https://doi.org/10.3390/en13174501 - 1 Sep 2020

Cited by 13 | Viewed by 5017

Abstract

This paper investigates the intraday electricity pricing of 15-min. contracts in night hours. We tailor a recently introduced econometric model with fundamental impacts, which is successful in describing the pricing of day contracts. Our estimation results show that the mean reversion and the [...] Read more.

This paper investigates the intraday electricity pricing of 15-min. contracts in night hours. We tailor a recently introduced econometric model with fundamental impacts, which is successful in describing the pricing of day contracts. Our estimation results show that the mean reversion and the positive price impact of neighboring contracts are generic features of the price formation process on the intraday market, independent of the time of day. Intraday auction prices have higher explanatory power for the pricing of night than day contracts, particularly, for the first and last 15-min. contract in a night hour. Intradaily updated forecasts of wind power infeed are the only significant fundamental factors for intraday electricity prices at night. Neither expected conventional capacities nor the slope of the merit order curve contribute to explaining price dynamics. Overall, we conclude that fundamentals lose in importance in night hours and the 15-min. intraday market is rather driven by price information. Full article

(This article belongs to the Special Issue Uncertainties and Risk Management in Competitive Energy Markets)

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24 pages, 4970 KiB

Open AccessEditor’s ChoiceArticle

Performance Comparison between Two Established Microgrid Planning MILP Methodologies Tested On 13 Microgrid Projects

by Michael Stadler, Zack Pecenak, Patrick Mathiesen, Kelsey Fahy and Jan Kleissl

Energies 2020, 13(17), 4460; https://doi.org/10.3390/en13174460 - 28 Aug 2020

Cited by 9 | Viewed by 4689

Abstract

Mixed Integer Linear Programming (MILP) optimization algorithms provide accurate and clear solutions for Microgrid and Distributed Energy Resources projects. Full-scale optimization approaches optimize all time-steps of data sets (e.g., 8760 time-step and higher resolutions), incurring extreme and unpredictable run-times, often prohibiting such approaches [...] Read more.

Mixed Integer Linear Programming (MILP) optimization algorithms provide accurate and clear solutions for Microgrid and Distributed Energy Resources projects. Full-scale optimization approaches optimize all time-steps of data sets (e.g., 8760 time-step and higher resolutions), incurring extreme and unpredictable run-times, often prohibiting such approaches for effective Microgrid designs. To reduce run-times down-sampling approaches exist. Given that the literature evaluates the full-scale and down-sampling approaches only for limited numbers of case studies, there is a lack of a more comprehensive study involving multiple Microgrids. This paper closes this gap by comparing results and run-times of a full-scale 8760 h time-series MILP to a peak preserving day-type MILP for 13 real Microgrid projects. The day-type approach reduces the computational time between 85% and almost 100% (from 2 h computational time to less than 1 min). At the same time the day-type approach keeps the objective function (OF) differences below 1.5% for 77% of the Microgrids. The other cases show OF differences between 6% and 13%, which can be reduced to 1.5% or less by applying a two-stage hybrid approach that designs the Microgrid based on down-sampled data and then performs a full-scale dispatch algorithm. This two stage approach results in 20–99% run-time savings. Full article

(This article belongs to the Special Issue Microgrids: Planning, Protection and Control)

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25 pages, 2428 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

New Reactive Power Compensation Strategies for Railway Infrastructure Capacity Increasing

by Vítor A. Morais, João L. Afonso, Adriano S. Carvalho and António P. Martins

Energies 2020, 13(17), 4379; https://doi.org/10.3390/en13174379 - 25 Aug 2020

Cited by 15 | Viewed by 3482

Abstract

In AC railway electrification systems, the impact of reactive power flow in the feeding voltage magnitude is one aspect contributing to the quality of supply degradation. Specifically, this issue results in limitations in the infrastructure capacity, either in the maximum number of trains [...] Read more.

In AC railway electrification systems, the impact of reactive power flow in the feeding voltage magnitude is one aspect contributing to the quality of supply degradation. Specifically, this issue results in limitations in the infrastructure capacity, either in the maximum number of trains and in maximum train power. In this paper, two reactive power compensation strategies are presented and compared, in terms of the theoretical railway infrastructure capacity. The first strategy considers a static VAR compensator, located in the neutral zone and compensating the substation reactive power, achieving a maximum capacity increase up to 50% without depending on each train active power. The second strategy adapts each train reactive power, achieving also a capacity increase around 50%, only with an increase of the train apparent power below 10%. With a smart metering infrastructure, the implementation of such compensation strategy is viable, satisfying the requirements of real-time knowledge of the railway electrification system state. Specifically, the usage of droop curves to adapt in real time the compensation scheme can bring the operation closer to optimality. Thus, the quality of supply and the infrastructure capacity can be increased with a mobile reactive power compensation scheme, based on a smart metering framework. Full article

(This article belongs to the Special Issue Power Quality in Electrified Transportation Systems)

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21 pages, 7211 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Power and Wind Shear Implications of Large Wind Turbine Scenarios in the US Central Plains

by Rebecca J. Barthelmie, Tristan J. Shepherd, Jeanie A. Aird and Sara C. Pryor

Energies 2020, 13(16), 4269; https://doi.org/10.3390/en13164269 - 18 Aug 2020

Cited by 23 | Viewed by 5904

Abstract

Continued growth of wind turbine physical dimensions is examined in terms of the implications for wind speed, power and shear across the rotor plane. High-resolution simulations with the Weather Research and Forecasting model are used to generate statistics of wind speed profiles for [...] Read more.

Continued growth of wind turbine physical dimensions is examined in terms of the implications for wind speed, power and shear across the rotor plane. High-resolution simulations with the Weather Research and Forecasting model are used to generate statistics of wind speed profiles for scenarios of current and future wind turbines. The nine-month simulations, focused on the eastern Central Plains, show that the power scales broadly as expected with the increase in rotor diameter (D) and wind speeds at hub-height (H). Increasing wind turbine dimensions from current values (approximately H = 100 m, D = 100 m) to those of the new International Energy Agency reference wind turbine (H = 150 m, D = 240 m), the power across the rotor plane increases 7.1 times. The mean domain-wide wind shear exponent (α) decreases from 0.21 (H = 100 m, D = 100 m) to 0.19 for the largest wind turbine scenario considered (H = 168 m, D = 248 m) and the frequency of extreme positive shear (α > 0.2) declines from 48% to 38% of 10-min periods. Thus, deployment of larger wind turbines potentially yields considerable net benefits for both the wind resource and reductions in fatigue loading related to vertical shear. Full article

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

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23 pages, 1559 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Data for Urban Scale Building Energy Modelling: Assessing Impacts and Overcoming Availability Challenges

by Solène Goy, François Maréchal and Donal Finn

Energies 2020, 13(16), 4244; https://doi.org/10.3390/en13164244 - 17 Aug 2020

Cited by 23 | Viewed by 3832

Abstract

Data are essential to urban building energy models and yet, obtaining sufficient and accurate building data at a large-scale is challenging. Previous studies have highlighted that the data impact on urban case studies has not been sufficiently discussed. This paper addresses this gap [...] Read more.

Data are essential to urban building energy models and yet, obtaining sufficient and accurate building data at a large-scale is challenging. Previous studies have highlighted that the data impact on urban case studies has not been sufficiently discussed. This paper addresses this gap by providing an analysis of the impact of input data on building energy modelling at an urban scale. The paper proposes a joint review of data impact and data accessibility to identify areas where future survey efforts should be concentrated. Moreover, a Morris sensitivity analysis is carried out on a large-scale residential case study, to rank input parameters by impact on space heating demand. This paper shows that accessible data impact the whole modelling process, from approach selection to model replicability. The sensitivity analysis shows that the setpoint and thermal characteristics were the most impactful for the case study considered. Solutions proposed to overcome availability and accessibility issues include organising annual workshops between data users and data owners, or developing online databases that could be populated on a volunteer-basis by data owners. Overall, overcoming data challenges is essential for the transition towards smarter cities, and will require an improved communication between all city stakeholders. Full article

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

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26 pages, 5353 KiB

Open AccessEditor’s ChoiceArticle

Power Resilience Enhancement of a Residential Electricity User Using Photovoltaics and a Battery Energy Storage System under Uncertainty Conditions

by Nallapaneni Manoj Kumar, Aritra Ghosh and Shauhrat S. Chopra

Energies 2020, 13(16), 4193; https://doi.org/10.3390/en13164193 - 13 Aug 2020

Cited by 52 | Viewed by 5877

Abstract

Even in today’s modern electric grid infrastructure, the uncertainty in the power supply is more often seen and is mainly due to power outages. The reasons for power outages might be any of the following: extreme weather events, asset failure, natural disasters, power [...] Read more.

Even in today’s modern electric grid infrastructure, the uncertainty in the power supply is more often seen and is mainly due to power outages. The reasons for power outages might be any of the following: extreme weather events, asset failure, natural disasters, power surges, acute accidents, and even operational errors by the workforce. Such uncertain situations are permitting us to think of it as a resilience problem. In most cases, the power outages may last from a few minutes to a few weeks, depending on the nature of the resilience issue and the power supply system (PSS) configuration. Therefore, it is imperative to understand and improve the resilience of a PSS. In this paper, a four-component resilience framework is proposed to study and compare the resilience of three different PSS configurations of residential electricity users (REUs) considering the realistic power outage conditions in the humid subtropical ecosystem. The proposed PSS configurations contain electric grid (EG), natural gas power generator (NGPG), battery energy storage (BES), and photovoltaics (PV) as the assets. The three PSS configurations of a REUs are EG + BES, EG + NGPG + BES, and EG + PV + BES, respectively, and in these, one REU is only the consumer and the other two REUs are prosumers. By using the proposed framework, simulations are performed on the three PSS configuration to understand the increasing load resiliency in the event of a power outage. Also, a comparative techno-economic and life cycle based environmental assessment is performed to select the most resilient PSS configuration among the EG + BES, EG + NGPG + BES, and EG + PV + BES for an REU. From the results, it was established that EG + PV + BES configuration would enhance the power resilience of an REU better than the other two PSS configurations. Besides, it is also observed that the identified resilient PSS configuration is cost-effective and environmentally efficient. Overall, the proposed framework will enable the REUs to opt for the PSS configuration that is resilient and affordable. Full article

(This article belongs to the Special Issue Assessment of Photovoltaic-Battery Systems)

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31 pages, 2982 KiB

Open AccessEditor’s ChoiceArticle

A GIS-Based Planning Approach for Urban Power and Natural Gas Distribution Grids with Different Heat Pump Scenarios

by Jolando M. Kisse, Martin Braun, Simon Letzgus and Tanja M. Kneiske

Energies 2020, 13(16), 4052; https://doi.org/10.3390/en13164052 - 5 Aug 2020

Cited by 17 | Viewed by 6052

Abstract

Next to building insulation, heat pumps driven by electrical compressors (eHPs) or by gas engines (geHPs) can be used to reduce primary energy demand for heating. They come with different investment requirements, operating costs and emissions caused. In addition, they affect both the [...] Read more.

Next to building insulation, heat pumps driven by electrical compressors (eHPs) or by gas engines (geHPs) can be used to reduce primary energy demand for heating. They come with different investment requirements, operating costs and emissions caused. In addition, they affect both the power and gas grids, which necessitates the assessment of both infrastructures regarding grid expansion planning. To calculate costs and CO

_{2}

emissions, 2000 electrical load profiles and 180 different heat demand profiles for single-family homes were simulated and heat pump models were applied. In a case study for a neighborhood energy model, the load profiles were assigned to buildings in an example town using public data on locations, building age and energetic refurbishment variants. In addition, the town’s gas distribution network and low voltage grid were modeled. Power and gas flows were simulated and costs for required grid extensions were calculated for 11% and 16% heat pump penetration. It was found that eHPs have the highest energy costs but will also have the lowest CO

_{2}

emissions by 2030 and 2050. For the investigated case, power grid investments of 11,800 euros/year are relatively low compared to gas grid connection costs of 70,400 euros/year. If eHPs and geHPs are combined, a slight reduction of overall costs is possible, but emissions would rise strongly compared to the all-electric case. Full article

(This article belongs to the Special Issue Integration of Renewables in Power Systems by Multi-Energy System Interaction)

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15 pages, 1549 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Education for Sustainable Energy: Comparison of Different Types of E-Learning Activities

by María Ángeles Martín-Lara and Nuria Rico

Energies 2020, 13(15), 4022; https://doi.org/10.3390/en13154022 - 4 Aug 2020

Cited by 5 | Viewed by 3403

Abstract

This paper reports a comparison of results obtained by using different e-learning strategies for teaching a biogas topic in two courses of the chemical engineering degree at the University of Granada. Particularly, four different asynchronous e-learning activities were carefully chosen: (1) noninteractive videos [...] Read more.

This paper reports a comparison of results obtained by using different e-learning strategies for teaching a biogas topic in two courses of the chemical engineering degree at the University of Granada. Particularly, four different asynchronous e-learning activities were carefully chosen: (1) noninteractive videos and audio files; (2) reading papers and discussion; (3) virtual tour of recommended websites of entities/associations/organizations working in the biogas sector; (4) PowerPoint slides and class notes. Students evaluated their satisfaction level (assessment) and teachers gave scores for evaluation exams (scores). We discuss the results from a quantitative point of view to suggest recommendations for improving e-learning implementations in education for sustainable energy. For dependent variables, reached scores and satisfaction assessment, we find the differences between means for students in two different academic years are no significant. In addition, there are no significant differences between means depending on the type of course. Significant differences appear for scores and satisfaction assessment between different activities. Finally, we deeply analyze the relationship between score and satisfaction assessment. The results show a positive correlation between assessment of e-learning activities and the score level reached by students. Full article

(This article belongs to the Special Issue Toward the Circular Economy in the Energy Sector: The Role of Higher Education)

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20 pages, 10547 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Occupancy Prediction Using Differential Evolution Online Sequential Extreme Learning Machine Model

by Jonas Bielskus, Violeta Motuzienė, Tatjana Vilutienė and Audrius Indriulionis

Energies 2020, 13(15), 4033; https://doi.org/10.3390/en13154033 - 4 Aug 2020

Cited by 11 | Viewed by 3336

Abstract

Despite increasing energy efficiency requirements, the full potential of energy efficiency is still unlocked; many buildings in the EU tend to consume more energy than predicted. Gathering data and developing models to predict occupants’ behaviour is seen as the next frontier in sustainable [...] Read more.

Despite increasing energy efficiency requirements, the full potential of energy efficiency is still unlocked; many buildings in the EU tend to consume more energy than predicted. Gathering data and developing models to predict occupants’ behaviour is seen as the next frontier in sustainable design. Measurements in the analysed open-space office showed accordingly 3.5 and 2.7 times lower occupancy compared to the ones given by DesignBuilder’s and EN 16798-1. This proves that proposed occupancy patterns are only suitable for typical open-space offices. The results of the previous studies and proposed occupancy prediction models have limited applications and limited accuracies. In this paper, the hybrid differential evolution online sequential extreme learning machine (DE-OSELM) model was applied for building occupants’ presence prediction in open-space office. The model was not previously applied in this area of research. It was found that prediction using experimentally gained indoor and outdoor parameters for the whole analysed period resulted in a correlation coefficient R² = 0.72. The best correlation was found with indoor CO₂ concentration—R² = 0.71 for the analysed period. It was concluded that a 4 week measurement period was sufficient for the prediction of the building’s occupancy and that DE-OSELM is a fast and reliable model suitable for this purpose. Full article

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

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35 pages, 815 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Applications of Game Theory to Design and Operation of Modern Power Systems: A Comprehensive Review

by Aviad Navon, Gefen Ben Yosef, Ram Machlev, Shmuel Shapira, Nilanjan Roy Chowdhury, Juri Belikov, Ariel Orda and Yoash Levron

Energies 2020, 13(15), 3982; https://doi.org/10.3390/en13153982 - 2 Aug 2020

Cited by 38 | Viewed by 8775

Abstract

In this work, we review papers that employ game theoretic tools to study the operation and design of modern electric grids. We consider four topics in this context: energy trading, energy balancing, grid planning, and system reliability, and we demonstrate the advantages of [...] Read more.

In this work, we review papers that employ game theoretic tools to study the operation and design of modern electric grids. We consider four topics in this context: energy trading, energy balancing, grid planning, and system reliability, and we demonstrate the advantages of using game-theoretic approaches for analyzing complex interactions among independent players. The results and conclusions provide insights regarding many aspects of design and operation, such as efficient methodologies for expansion planning, cyber-security, and frequency stability, or fair-benefit allocation among players. A central conclusion is that modeling the system from the perspective of one entity with unlimited information and control span is often impractical, so correct modeling of the selfish behavior of independent players may be critical for the development of future power systems. Another conclusion is that correct usage of incentives by appropriate regulation or sophisticated pricing mechanisms may improve the social welfare, and, in several cases, the results obtained are as good as those obtained by central planning. Using an extensive content analysis, we point to several trends in the current research and attempt to identify the research directions that are currently at the focus of the community. Full article

(This article belongs to the Special Issue Power System Dynamics and Renewable Energy Integration)

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27 pages, 2419 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Adaptive Energy Management in 5G Network Slicing: Requirements, Architecture, and Strategies

by Christian Tipantuña and Xavier Hesselbach

Energies 2020, 13(15), 3984; https://doi.org/10.3390/en13153984 - 2 Aug 2020

Cited by 12 | Viewed by 3997

Abstract

Energy consumption is a critical issue for the communications network operators, impacting deeply the cost of the services, as well as the ecological footprint. Network slicing architecture for 5G mobile communications enables multiple independent virtual networks to be created on top of a [...] Read more.

Energy consumption is a critical issue for the communications network operators, impacting deeply the cost of the services, as well as the ecological footprint. Network slicing architecture for 5G mobile communications enables multiple independent virtual networks to be created on top of a common shared physical infrastructure. Each network slice needs different types of resources, including energy, to fulfill the demands requested by each application, operator, or vertical market. The existing literature on network slicing is mainly targeted at the partition of network resources; however, the corresponding management of energy consumption is an unconsidered critical concern. This paper analyzes the requirements for an energy-aware 5G network slicing provisioning according to the 3GPP specifications, proposes an architecture, and studies the strategies to provide efficient energy consumption in terms of renewable and non-renewable sources. NFV and SDN technologies are the essential enablers and leverage the Internet of Things (IoT) connectivity provided by 5G networks. This paper also presents the technical 5G technology documentation related to the proposal, the requirements for adaptive energy management, and the Integer Linear Programming (ILP) formulation of the energy management model. To validate the improvements, an exact optimal algorithmic solution is presented and some heuristic strategies. Full article

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

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21 pages, 12874 KiB

Open AccessEditor’s ChoiceReview

Bibliometric Analysis of Trends in Biomass for Bioenergy Research

by Giovanni Ferrari, Andrea Pezzuolo, Abdul-Sattar Nizami and Francesco Marinello

Energies 2020, 13(14), 3714; https://doi.org/10.3390/en13143714 - 19 Jul 2020

Cited by 47 | Viewed by 5175

Abstract

This paper aims to provide a bibliometric analysis of publication trends on the themes of biomass and bioenergy worldwide. A wide range of studies have been performed in the field of the usage of biomass for energy production, in order to contribute to [...] Read more.

This paper aims to provide a bibliometric analysis of publication trends on the themes of biomass and bioenergy worldwide. A wide range of studies have been performed in the field of the usage of biomass for energy production, in order to contribute to the green transition from fossil fuels to renewable energies. Over the past 20 years (from 2000 to 2019), approximately 10,000 articles have been published in the “Agricultural and Biological Sciences” field on this theme, covering all stages of production—from the harvesting of crops to the particular type of energy produced. Articles were obtained from the SCOPUS database and examined with a text mining tool in order to analyze publication trends over the last two decades. Publications per year in the bioenergy theme have grown from 91 in 2000 to 773 in 2019. In particular the analyses showed how environmental aspects have increased their importance (from 7.3% to 11.8%), along with studies related to crop conditions (from 10.4% to 18.6%). Regarding the use of energy produced, growing trends were recognized for the impact of biofuels (mentions moved from 0.14 times per article in 2000 to 0.38 in 2019) and biogases (from 0.14 to 0.42 mentions). Environmental objectives have guided the interest of researchers, encouraging studies on biomass sources and the optimal use of the energy produced. This analysis aims to describe the research evolution, providing an analysis that can be helpful to predict future scenarios and participation among stakeholders in the sector. Full article

(This article belongs to the Special Issue Biomass for Energy Application)

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21 pages, 6249 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

CFD Simulation and a Pragmatic Analysis of Performance and Emissions of Tomato Seed Biodiesel Blends in a 4-Cylinder Diesel Engine

by Rahim Karami, Mohammad G. Rasul and Mohammad M. K. Khan

Energies 2020, 13(14), 3688; https://doi.org/10.3390/en13143688 - 17 Jul 2020

Cited by 13 | Viewed by 4188

Abstract

Rising global concerns about global warming caused by pollution from excessive fossil fuels consumption, along with the high price of them in diesel engines, are the important reasons to search for fuels which is readily available and do not have destructive effects on [...] Read more.

Rising global concerns about global warming caused by pollution from excessive fossil fuels consumption, along with the high price of them in diesel engines, are the important reasons to search for fuels which is readily available and do not have destructive effects on the environment. Biodiesel is arguably the most appropriate and sustainable alternative to diesel fuel. Tomato seeds are one of the potential sources of biodiesel. They make up about 72% by weight of tomato waste, which contains an average of 24% oil. Tomato seed oil (TSO) can be used as a cheap and non-edible source of biodiesel. This paper investigated, both experimentally and numerically, the effects of different diesel–TSOB (tomato seed oil biodiesel) blends on the performance and emissions parameters of a four-cylinder, four-stroke, indirect injection diesel engine. The main goal of the paper was the simulation of the formation process of the emissions in the combustion chamber. The experimentally measured parameters such as torque, brake specific fuel consumption, exhaust gas temperature, nitrogen oxides, carbon monoxide, carbon dioxide, particulate matter, peak in-cylinder pressure, in-cylinder temperature and Reaction_Progress_Variable at different engine loads and speeds from 1200 to 2400 rpm at increments of 200 rpm are analyzed through ANOVA. The highest brake specific fuel consumption (BSFC) was observed for pure diesel and the lowest for the fuel blend with 10% biodiesel. The fuel blend with 20% biodiesel produced the highest torque. The engine was modeled using the AVL FIRE software. The model simulation results revealed that the highest nitrogen oxide (NOx) is produced in the throat of the combustion chamber to the top of the piston, the place of carbon dioxides (CO₂) formation is near the combustion chamber boundaries and the location of carbon monoxides (CO) formation is near the combustion chamber boundaries and at the center area of the top of the piston. These results also show that the particulate matter (PM) emissions are formed where the fuel is injected into the combustion chamber. Full article

(This article belongs to the Collection Feature Papers in Bio-Energy)

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127 pages, 39930 KiB

Open AccessEditor’s ChoiceReview

A Comprehensive Review on Energy Storage Systems: Types, Comparison, Current Scenario, Applications, Barriers, and Potential Solutions, Policies, and Future Prospects

by Eklas Hossain, Hossain Mansur Resalat Faruque, Md. Samiul Haque Sunny, Naeem Mohammad and Nafiu Nawar

Energies 2020, 13(14), 3651; https://doi.org/10.3390/en13143651 - 15 Jul 2020

Cited by 207 | Viewed by 28314

Abstract

Driven by global concerns about the climate and the environment, the world is opting for renewable energy sources (RESs), such as wind and solar. However, RESs suffer from the discredit of intermittency, for which energy storage systems (ESSs) are gaining popularity worldwide. Surplus [...] Read more.

Driven by global concerns about the climate and the environment, the world is opting for renewable energy sources (RESs), such as wind and solar. However, RESs suffer from the discredit of intermittency, for which energy storage systems (ESSs) are gaining popularity worldwide. Surplus energy obtained from RESs can be stored in several ways, and later utilized during periods of intermittencies or shortages. The idea of storing excess energy is not new, and numerous researches have been conducted to adorn this idea with innovations and improvements. This review is a humble attempt to assemble all the available knowledge on ESSs to benefit novice researchers in this field. This paper covers all core concepts of ESSs, including its evolution, elaborate classification, their comparison, the current scenario, applications, business models, environmental impacts, policies, barriers and probable solutions, and future prospects. This elaborate discussion on energy storage systems will act as a reliable reference and a framework for future developments in this field. Any future progress regarding ESSs will find this paper a helpful document wherein all necessary information has been assembled. Full article

(This article belongs to the Section D: Energy Storage and Application)

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18 pages, 4282 KiB

Open AccessEditor’s ChoiceArticle

Optimal Model for Energy Management Strategy in Smart Building with Energy Storage Systems and Electric Vehicles

by Francisco David Moya, José Luis Torres-Moreno and José Domingo Álvarez

Energies 2020, 13(14), 3605; https://doi.org/10.3390/en13143605 - 13 Jul 2020

Cited by 18 | Viewed by 3914

Abstract

The aim of this work was to develop an optimal model for an energy management strategy in a real micro-grid, which involves a smart building, a photovoltaic system with storage, and a plug-in full electric vehicle. A controller based on a mathematical algorithm [...] Read more.

The aim of this work was to develop an optimal model for an energy management strategy in a real micro-grid, which involves a smart building, a photovoltaic system with storage, and a plug-in full electric vehicle. A controller based on a mathematical algorithm was the core of each strategy, which directly acted on a relay board managing the interconnection between the different elements comprising the micro-grid. The development of an optimization model involving binary variables required an efficient code that achieved solutions in a short time. The analyzed case-study corresponded to the solar energy research center (CIESOL) smart building, a bioclimatic building, that is located at the University of Almería (Spain), designated to research in renewable energies. Using the methodologies described in this work, the total cost of the smart building energy consumption was minimized by decreasing the power supplied from the grid, especially at peak hours. Highlighting the use of a simple model that provided better performance than the current state of the art methodologies. The optimal model for energy management strategy demonstrated the advantages of using classical optimization techniques to solve this specific optimization problem, compared to a rule-based controller. The linear modeling was capable of producing a simple algorithm with less code development and a reduction in the computational effort. Full article

(This article belongs to the Special Issue Assessment of Photovoltaic-Battery Systems)

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30 pages, 1849 KiB

Open AccessEditor’s ChoiceArticle

Cities4ZERO Approach to Foresight for Fostering Smart Energy Transition on Municipal Level

by Merit Tatar, Tarmo Kalvet and Marek Tiits

Energies 2020, 13(14), 3533; https://doi.org/10.3390/en13143533 - 9 Jul 2020

Cited by 8 | Viewed by 5023

Abstract

Smart energy transition efforts at the municipal level are gaining importance and go far beyond implementing single projects. Decarbonising cities involves complex strategic planning and needs system level thinking and changes. This has been increasingly realised at the municipal level, but challenges remain [...] Read more.

Smart energy transition efforts at the municipal level are gaining importance and go far beyond implementing single projects. Decarbonising cities involves complex strategic planning and needs system level thinking and changes. This has been increasingly realised at the municipal level, but challenges remain regarding the tools, involvement of stakeholders and on the development of policies. The focus of the research is on the use of participatory foresight for fostering smart energy transition on a municipal level, the key benefits and success factors that participatory foresight brings, and the replicability of this approach. Within the novel Cities4ZERO framework, an overarching methodology for a smart urban decarbonisation transition, guiding cities through the process of developing the most appropriate strategies, plans, projects, as well as looking for the commitment of key local stakeholders for an effective transition–foresight framework, was developed and tested in five pilot cities. Foresight as applied within the Cities4ZERO framework creates a participatory process which brings stakeholders together to achieve unified scenarios, and a common vision for future urban decarbonisation strategies. The methodology is replicable and increases the quality of strategic energy planning by fostering long-term system thinking. Full article

(This article belongs to the Special Issue Integrated Sustainable Urban Development: Governance and Management Strategies for Connecting Urban Systems)

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18 pages, 4597 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Optimal Sizing of Fuel Cell Hybrid Power Sources with Reliability Consideration

by Adriano Ceschia, Toufik Azib, Olivier Bethoux and Francisco Alves

Energies 2020, 13(13), 3510; https://doi.org/10.3390/en13133510 - 7 Jul 2020

Cited by 11 | Viewed by 3528

Abstract

This paper addresses the issue of optimal sizing reliability applied to a fuel cell/battery hybrid system. This specific problem raises the global problem of strong coupling between hardware and control parameters. To tackle this matter, the proposed methodology uses nested optimization loops. Furthermore, [...] Read more.

This paper addresses the issue of optimal sizing reliability applied to a fuel cell/battery hybrid system. This specific problem raises the global problem of strong coupling between hardware and control parameters. To tackle this matter, the proposed methodology uses nested optimization loops. Furthermore, to increase the optimal design relevance, a reliability assessment of the optimal sizing set is introduced. This new paradigm enables showing the early impact of the reliability criteria on design choices regarding energetic performance index. It leads to a smart design methodology permitting to avoid complexity and save computing time. It considerably helps design engineers set up the best hybridization rate and enables practicing tradeoffs, including reliability aspects in the early design stages. Full article

(This article belongs to the Special Issue Design, Diagnosis and Control and Social Acceptance of Battery, Solar Cell and Fuel Cell System)

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