Energies

Article

25 pages, 5098 KiB

Open AccessEditor’s ChoiceArticle

Enabling Optimal Energy Management with Minimal IoT Requirements: A Legacy A/C Case Study

by Panagiotis Michailidis, Paschalis Pelitaris, Christos Korkas, Iakovos Michailidis, Simone Baldi and Elias Kosmatopoulos

Energies 2021, 14(23), 7910; https://doi.org/10.3390/en14237910 - 25 Nov 2021

Cited by 8 | Viewed by 2089

Abstract

The existing literature on energy saving focuses on large-scale buildings, wherein the energy-saving potential is substantially larger than smaller-scale buildings. However, the research intensity is significantly less for small-scale deployments and their capacities to regulate energy use individually, directly and without depreciating users’ [...] Read more.

The existing literature on energy saving focuses on large-scale buildings, wherein the energy-saving potential is substantially larger than smaller-scale buildings. However, the research intensity is significantly less for small-scale deployments and their capacities to regulate energy use individually, directly and without depreciating users’ comfort and needs. The current research effort focused on energy saving and user satisfaction, concerning a low-cost—yet technically sophisticated—methodology for controlling conventional residential HVAC units through cheap yet reliable actuation and sensing and auxiliary IoT equipment. The basic ingredients of the proposed experimental methodology involve a conventional A/C unit, an Arduino microcontroller, typical wireless IoT sensors and actuators, a configured graphical environment and a sophisticated, model-free, optimization-and-control algorithm (PCAO) that portrays the ground basis for achieving improved performance results in comparison with conventional methods. The main goal of this study was to produce a system that would adequately and expeditiously achieve energy savings by utilizing minimal hardware/equipment (affordability). The system was designed to be easily expandable in terms of new units or thermal equipment (expandability) and also to be autonomous, requiring zero user interventions at the experimental site (automation). The real-life measurements were collected over two different seasonal periods of the year (winter, summer) and concerned a conventional apartment in the city of Xanthi, Northern Greece, where summers and winters exhibit quite diverse climate characteristics. The final results revealed the increased efficiency of PCAO’s optimization in comparison with a conventional rule-based control strategy (RBC), as concerns energy savings and user satisfaction. Full article

(This article belongs to the Special Issue Innovative Solutions towards Autonomous Modular Facade Systems)

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19 pages, 5076 KiB

Open AccessEditor’s ChoiceArticle

How Long Will Combustion Vehicles Be Used? Polish Transport Sector on the Pathway to Climate Neutrality

by Wojciech Rabiega, Artur Gorzałczyński, Robert Jeszke, Paweł Mzyk and Krystian Szczepański

Energies 2021, 14(23), 7871; https://doi.org/10.3390/en14237871 - 24 Nov 2021

Cited by 10 | Viewed by 3126

Abstract

Transformation of road transport sector through replacing of internal combustion vehicles with zero-emission technologies is among key challenges to achievement of climate neutrality by 2050. In a constantly developing economy, the demand for transport services increases to ensure continuity in the supply chain [...] Read more.

Transformation of road transport sector through replacing of internal combustion vehicles with zero-emission technologies is among key challenges to achievement of climate neutrality by 2050. In a constantly developing economy, the demand for transport services increases to ensure continuity in the supply chain and passenger mobility. Deployment of electric technologies in the road transport sector involves both businesses and households, its pace depends on the technological development of zero-emission vehicles, presence of necessary infrastructure and regulations on emission standards for new vehicles entering the market. Thus, this study attempts to estimate how long combustion vehicles will be in use and what the state of the fleet will be in 2050. For obtainment of results the TR³E partial equilibrium model was used. The study simulates the future fleet structure in passenger and freight transport. The results obtained for Poland for the climate neutrality (NEU) scenario show that in 2050 the share of vehicles using fossil fuels will be ca. 30% in both road passenger and freight transport. The consequence of shifts in the structure of the fleet is the reduction of CO₂ emissions ca. 80% by 2050 and increase of the transport demand for electricity and hydrogen. Full article

(This article belongs to the Special Issue Trends in the Development of Electric Vehicle)

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24 pages, 8516 KiB

Open AccessEditor’s ChoiceArticle

Experimental Investigation of the Heat Transfer Characteristics and Operation Limits of a Fork-Type Heat Pipe for Passive Cooling of a Spent Fuel Pool

by Changhwan Lim, Jonghwi Choi and Hyungdae Kim

Energies 2021, 14(23), 7862; https://doi.org/10.3390/en14237862 - 24 Nov 2021

Cited by 5 | Viewed by 2578

Abstract

A fork-type heat pipe (FHP) is a passive heat-transport and air-cooling device used to remove the decay heat of spent nuclear fuels stored in a liquid pool during a station blackout. FHPs have a unique geometrical design to resolve the significant mismatch between [...] Read more.

A fork-type heat pipe (FHP) is a passive heat-transport and air-cooling device used to remove the decay heat of spent nuclear fuels stored in a liquid pool during a station blackout. FHPs have a unique geometrical design to resolve the significant mismatch between the convective heat transfer coefficients of the evaporator and condenser parts. The evaporator at the bottom is a single heat-exchanger tube, whereas the condenser at the top consists of multiple finned tubes to maximize the heat transfer area. In this study, the heat transfer characteristics and operating limits of an FHP device were investigated experimentally. A laboratory-scale model of an FHP was manufactured, and a series of tests were conducted while the temperature was varied to simulate a spent fuel pool. As an index of the average heat transfer performance, the loop conductance was computed from the measurement data. The results show that the loop conductance of the FHP increased with the heat transfer rate but deteriorated significantly at the operating limit. The maximum attainable heat transfer rate of the unit FHP model was accurately predicted by the existing correlations of the counter-current flow limit for a single-rod-type heat pipe. In addition, the instant heat transfer behaviors of the FHP model under different temperature conditions were examined to interpret the measured loop conductance variation and operating limit. Full article

(This article belongs to the Special Issue Two-Phase Flow with Boiling Heat Transfer)

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14 pages, 3893 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Archimedes Screw Design: An Analytical Model for Rapid Estimation of Archimedes Screw Geometry

by Arash YoosefDoost and William David Lubitz

Energies 2021, 14(22), 7812; https://doi.org/10.3390/en14227812 - 22 Nov 2021

Cited by 11 | Viewed by 9603

Abstract

In designing Archimedes screws, determination of the geometry is among the fundamental questions that may affect many aspects of the Archimedes screw powerplant. Most plants are run-of-river and highly depend on local flow duration curves that vary from river to river. An ability [...] Read more.

In designing Archimedes screws, determination of the geometry is among the fundamental questions that may affect many aspects of the Archimedes screw powerplant. Most plants are run-of-river and highly depend on local flow duration curves that vary from river to river. An ability to rapidly produce realistic estimations for the initial design of a site-specific Archimedes screw plant helps to facilitate and accelerate the optimization of the powerplant design. An analytical method in the form of a single equation was developed to rapidly and easily estimate the Archimedes screw geometry for a specific site. This analytical equation was developed based on the accepted, proved or reported common designs characteristics of Archimedes screws. It was then evaluated by comparison of equation predictions to existing Archimedes screw hydropower plant installations. The evaluation results indicate a high correlation and reasonable relative difference. Use of the equation eliminates or simplifies several design steps and loops and accelerates the development of initial design estimations of Archimedes screw generators dramatically. Moreover, it helps to dramatically reduce one of the most significant burdens of small projects: the nonscalable initial investigation costs and enables rapid estimation of the feasibility of Archimedes screw powerplants at many potential sites. Full article

(This article belongs to the Special Issue Energy Conversion System – Small Hydropower Plants)

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20 pages, 2390 KiB

Open AccessEditor’s ChoiceArticle

Relationship among Economic Growth (GDP), Energy Consumption and Carbon Dioxide Emission: Evidence from V4 Countries

by Janusz Myszczyszyn and Błażej Suproń

Energies 2021, 14(22), 7734; https://doi.org/10.3390/en14227734 - 18 Nov 2021

Cited by 20 | Viewed by 3906

Abstract

The main objective of the research was to determine the long-term and short-term correlation between CO₂ emissions per capita, energy consumption per capita, and the level of economic growth of GDP per capita in the V4 countries. These countries, being EU members [...] Read more.

The main objective of the research was to determine the long-term and short-term correlation between CO₂ emissions per capita, energy consumption per capita, and the level of economic growth of GDP per capita in the V4 countries. These countries, being EU members since 2004 and previously being in the sphere of influence of the Soviet Union, have introduced a number of economic reforms, but in the area of climate protection, including decarbonization, they struggle with many problems, as their economies are largely dependent on energy from non-renewable resources. The results of the research are varied, but the authors confirmed, especially in the case of Poland, the long-term correlations between the studied variables. In the short term, such interdependencies also occurred, especially between the level of energy consumption per capita and the level of CO₂ emissions. Full article

(This article belongs to the Special Issue The Role of Spatial Policy Tools in Renewable Energy Investment)

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20 pages, 486 KiB

Open AccessEditor’s ChoiceArticle

Cost-Optimized Microgrid Coalitions Using Bayesian Reinforcement Learning

by Mohammad Sadeghi, Shahram Mollahasani and Melike Erol-Kantarci

Energies 2021, 14(22), 7481; https://doi.org/10.3390/en14227481 - 9 Nov 2021

Cited by 2 | Viewed by 1659

Abstract

Microgrids are empowered by the advances in renewable energy generation, which enable the microgrids to generate the required energy for supplying their loads and trade the surplus energy to other microgrids or the macrogrid. Microgrids need to optimize the scheduling of their demands [...] Read more.

Microgrids are empowered by the advances in renewable energy generation, which enable the microgrids to generate the required energy for supplying their loads and trade the surplus energy to other microgrids or the macrogrid. Microgrids need to optimize the scheduling of their demands and energy levels while trading their surplus with others to minimize the overall cost. This can be affected by various factors such as variations in demand, energy generation, and competition among microgrids due to their dynamic nature. Thus, reaching optimal scheduling is challenging due to the uncertainty caused by the generation/consumption of renewable energy and the complexity of interconnected microgrids and their interplay. Previous works mainly rely on modeling-based approaches and the availability of precise information on microgrid dynamics. This paper addresses the energy trading problem among microgrids by minimizing the cost while uncertainty exists in microgrid generation and demand. To this end, a Bayesian coalitional reinforcement learning-based model is introduced to minimize the energy trading cost among microgrids by forming stable coalitions. The results show that the proposed model can minimize the cost up to 23% with respect to the coalitional game theory model. Full article

(This article belongs to the Special Issue Energy in Networks)

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22 pages, 3649 KiB

Open AccessEditor’s ChoiceArticle

Analysis of the EU-27 Countries Energy Markets Integration in Terms of the Sustainable Development SDG7 Implementation

by Aurelia Rybak, Aleksandra Rybak and Spas D. Kolev

Energies 2021, 14(21), 7079; https://doi.org/10.3390/en14217079 - 29 Oct 2021

Cited by 12 | Viewed by 2161

Abstract

The article presents the results of research related to the SDG7 sustainable development implementation analysis. The goal is to provide affordable and clean energy. Its implementation will allow for development that will simultaneously provide the possibility of economic growth and the achievement of [...] Read more.

The article presents the results of research related to the SDG7 sustainable development implementation analysis. The goal is to provide affordable and clean energy. Its implementation will allow for development that will simultaneously provide the possibility of economic growth and the achievement of an optimal level of citizens’ health and life. The research was conducted for the countries of the European Union EU-27. During the analysis, the indicators proposed by Eurostat were used. The research aimed to examine the progress in EU member states’ energy markets integration. In order to carry out the indispensable research, it was necessary to use a spatial information system. Cluster analysis, as well as TSA analysis, were applied. The conducted research made it possible to verify the posed hypotheses and showed that the energy transformation process of the EU-27 countries is so complicated and heterogeneous that it has given rise to new independent and unique clusters. The authors also verified the adopted set of SDG7 achievement indicators using multiple regression. Additional indicators were also proposed that could complement the set and clarify its analyses. Full article

(This article belongs to the Special Issue Green Economy and Sustainable Development)

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16 pages, 765 KiB

Open AccessEditor’s ChoiceArticle

Quantitative Performance Comparison of Thermal Structure Function Computations

by Nils J. Ziegeler, Peter W. Nolte and Stefan Schweizer

Energies 2021, 14(21), 7068; https://doi.org/10.3390/en14217068 - 28 Oct 2021

Cited by 7 | Viewed by 2332

Abstract

The determination of thermal structure functions from transient thermal measurements using network identification by deconvolution is a delicate process as it is sensitive to noise in the measured data. Great care must be taken not only during the measurement process but also to [...] Read more.

The determination of thermal structure functions from transient thermal measurements using network identification by deconvolution is a delicate process as it is sensitive to noise in the measured data. Great care must be taken not only during the measurement process but also to ensure a stable implementation of the algorithm. In this paper, a method is presented that quantifies the absolute accuracy of network identification on the basis of different test structures. For this purpose, three measures of accuracy are defined. By these metrics, several variants of network identification are optimized and compared against each other. Performance in the presence of noise is analyzed by adding Gaussian noise to the input data. In the cases tested, the use of a Bayesian deconvolution provided the best results. Full article

(This article belongs to the Special Issue Latest Advances in Electrothermal Models II)

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16 pages, 4383 KiB

Open AccessEditor’s ChoiceArticle

Real-Time Monitoring and Static Data Analysis to Assess Energetic and Environmental Performances in the Wastewater Sector: A Case Study

by Maria Rosa di Cicco, Antonio Masiello, Antonio Spagnuolo, Carmela Vetromile, Laura Borea, Giuseppe Giannella, Manuela Iovinella and Carmine Lubritto

Energies 2021, 14(21), 6948; https://doi.org/10.3390/en14216948 - 22 Oct 2021

Cited by 11 | Viewed by 3217

Abstract

Real-time monitoring of energetic-environmental parameters in wastewater treatment plants enables big-data analysis for a true representation of the operating condition of a system, being still frequently mismanaged through policies based on the analysis of static data (energy billing, periodic chemical–physical analysis of wastewater). [...] Read more.

Real-time monitoring of energetic-environmental parameters in wastewater treatment plants enables big-data analysis for a true representation of the operating condition of a system, being still frequently mismanaged through policies based on the analysis of static data (energy billing, periodic chemical–physical analysis of wastewater). Here we discuss the results of monitoring activities based on both offline (“static”) data on the main process variables, and on-line (“dynamic”) data collected through a monitoring system for energetic-environmental parameters (dissolved oxygen, wastewater pH and temperature, TSS intake and output). Static-data analysis relied on a description model that employed statistical normalization techniques (KPIs, operational indicators). Dynamic data were statistically processed to explore possible correlations between energetic-environmental parameters, establishing comparisons with static data. Overall, the system efficiently fulfilled its functions, although it was undersized compared to the organic and hydraulic load it received. From the dynamic-data analysis, no correlation emerged between energy usage of the facility and dissolved oxygen content of the wastewater, whereas the TSS removal efficiency determined through static measurements was found to be underestimated. Finally, using probes allowed to characterize the pattern of pH and temperature values of the wastewater, which represent valuable physiological data for innovative and sustainable resource recovery technologies involving microorganisms. Full article

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18 pages, 7243 KiB

Open AccessEditor’s ChoiceArticle

Power-to-Gas and Power-to-X—The History and Results of Developing a New Storage Concept

by Michael Sterner and Michael Specht

Energies 2021, 14(20), 6594; https://doi.org/10.3390/en14206594 - 13 Oct 2021

Cited by 85 | Viewed by 9431

Abstract

Germany’s energy transition, known as ‘Energiewende’, was always very progressive. However, it came technically to a halt at the question of large-scale, seasonal energy storage for wind and solar, which was not available. At the end of the 2000s, we combined our knowledge [...] Read more.

Germany’s energy transition, known as ‘Energiewende’, was always very progressive. However, it came technically to a halt at the question of large-scale, seasonal energy storage for wind and solar, which was not available. At the end of the 2000s, we combined our knowledge of both electrical and process engineering, imitated nature by copying photosynthesis and developed Power-to-Gas by combining water electrolysis with CO₂-methanation to convert water and CO₂ together with wind and solar power to synthetic natural gas. Storing green energy by coupling the electricity with the gas sector using its vast TWh-scale storage facility was the solution for the biggest energy problem of our time. This was the first concept that created the term ‘sector coupling’ or ‘sectoral integration’. We first implemented demo sites, presented our work in research, industry and ministries, and applied it in many macroeconomic studies. It was an initial idea that inspired others to rethink electricity as well as eFuels as an energy source and energy carrier. We developed the concept further to include Power-to-Liquid, Power-to-Chemicals and other ways to ‘convert’ electricity into molecules and climate-neutral feedstocks, and named it ‘Power-to-X’at the beginning of the 2010s. Full article

(This article belongs to the Special Issue Seasonal Energy Storage with Power-to-Methane Technology)

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16 pages, 7006 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Two Power Converter Topologies in Wind Turbine System

by Andrzej Sikorski, Piotr Falkowski and Marek Korzeniewski

Energies 2021, 14(20), 6574; https://doi.org/10.3390/en14206574 - 13 Oct 2021

Cited by 9 | Viewed by 2462

Abstract

The article presents comprehensive results of research on two representative topologies of converters used in the path of processing energy generated in a wind turbine and transmitted to the grid. The topology T1 uses a two-level transistor-controlled rectifier as a converter from the [...] Read more.

The article presents comprehensive results of research on two representative topologies of converters used in the path of processing energy generated in a wind turbine and transmitted to the grid. The topology T1 uses a two-level transistor-controlled rectifier as a converter from the generator side, while the T2 topology uses DC/DC boost converter. In both topologies, a three-level back-to-back converter with a line filter L was used as a grid converter. The conclusions indicate the tendency of changes in power losses depending on the aforementioned parameters and can be used at the stage of deciding on the choice of topology, operating parameters or selection of control methods depending on the specific operating conditions of the wind turbine. Full article

(This article belongs to the Special Issue Power Electronics in Renewable, Storage, and Charging Systems)

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29 pages, 9353 KiB

Open AccessEditor’s ChoiceArticle

Opportunities in Jet-Impingement Cooling for Gas-Turbine Engines

by Sandip Dutta and Prashant Singh

Energies 2021, 14(20), 6587; https://doi.org/10.3390/en14206587 - 13 Oct 2021

Cited by 19 | Viewed by 5874

Abstract

Impingement heat transfer is considered one of the most effective cooling technologies that yield high localized convective heat transfer coefficients. This paper studies different configurable parameters involved in jet impingement cooling such as, exit orifice shape, crossflow regulation, target surface modification, spent air [...] Read more.

Impingement heat transfer is considered one of the most effective cooling technologies that yield high localized convective heat transfer coefficients. This paper studies different configurable parameters involved in jet impingement cooling such as, exit orifice shape, crossflow regulation, target surface modification, spent air reuse, impingement channel modification, jet pulsation, and other techniques to understand which of them are critical and how these heat-transfer-enhancement concepts work. The aim of this paper is to excite the thermal sciences community of this efficient cooling technique and instill some thoughts for future innovations. New orifice shapes are becoming feasible due to innovative 3D printing technologies. However, the orifice shape variations show that it is hard to beat a sharp-edged round orifice in heat transfer coefficient, but it comes with a higher pressure drop across the orifice. Any attempt to streamline the hole shape indicated a drop in the Nusselt number, thus giving the designer some control over thermal budgeting of a component. Reduction in crossflow has been attempted with channel modifications. The use of high-porosity conductive foam in the impingement space has shown marked improvement in heat transfer performance. A list of possible research topics based on this discussion is provided in the conclusion. Full article

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38 pages, 1673 KiB

Open AccessEditor’s ChoiceArticle

On the Need to Determine Accurately the Impact of Higher-Order Sensitivities on Model Sensitivity Analysis, Uncertainty Quantification and Best-Estimate Predictions

by Dan Gabriel Cacuci

Energies 2021, 14(19), 6318; https://doi.org/10.3390/en14196318 - 3 Oct 2021

Cited by 6 | Viewed by 1582

Abstract

This work aims at underscoring the need for the accurate quantification of the sensitivities (i.e., functional derivatives) of the results (a.k.a. “responses”) produced by large-scale computational models with respect to the models’ parameters, which are seldom known perfectly in practice. The large impact [...] Read more.

This work aims at underscoring the need for the accurate quantification of the sensitivities (i.e., functional derivatives) of the results (a.k.a. “responses”) produced by large-scale computational models with respect to the models’ parameters, which are seldom known perfectly in practice. The large impact that can arise from sensitivities of order higher than first has been highlighted by the results of a third-order sensitivity and uncertainty analysis of an OECD/NEA reactor physics benchmark, which will be briefly reviewed in this work to underscore that neglecting the higher-order sensitivities causes substantial errors in predicting the expectation and variance of model responses. The importance of accurately computing the higher-order sensitivities is further highlighted in this work by presenting a text-book analytical example from the field of neutron transport, which impresses the need for the accurate quantification of higher-order response sensitivities by demonstrating that their neglect would lead to substantial errors in predicting the moments (expectation, variance, skewness, kurtosis) of the model response’s distribution in the phase space of model parameters. The incorporation of response sensitivities in methodologies for uncertainty quantification, data adjustment and predictive modeling currently available for nuclear engineering systems is also reviewed. The fundamental conclusion highlighted by this work is that confidence intervals and tolerance limits on results predicted by models that only employ first-order sensitivities are likely to provide a false sense of confidence, unless such models also demonstrate quantitatively that the second- and higher-order sensitivities provide negligibly small contributions to the respective tolerance limits and confidence intervals. The high-order response sensitivities to parameters underlying large-scale models can be computed most accurately and most efficiently by employing the high-order comprehensive adjoint sensitivity analysis methodology, which overcomes the curse of dimensionality that hampers other methods when applied to large-scale models involving many parameters. Full article

(This article belongs to the Special Issue Advances in Modelling for Nuclear Science and Engineering)

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19 pages, 2485 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Star and String Offshore DC Collector Grid Topologies on the Aspect of Stability—An Impedance Approach

by Matthias Biskoping, Tanmay Kadam, Sriram Karthik Gurumurthy, Ferdinanda Ponci and Antonello Monti

Energies 2021, 14(19), 6253; https://doi.org/10.3390/en14196253 - 1 Oct 2021

Viewed by 1793

Abstract

Offshore Direct Current (DC) collector grids are a promising technology for decreasing the installation and operation costs of offshore wind parks. Nevertheless, the stability properties and hence the design of such DC collector grids is not common or standardised. Hence, this paper describes [...] Read more.

Offshore Direct Current (DC) collector grids are a promising technology for decreasing the installation and operation costs of offshore wind parks. Nevertheless, the stability properties and hence the design of such DC collector grids is not common or standardised. Hence, this paper describes an attempt to fill these gaps by analysing the stability of two different types of DC collector grids—star and string—by considering identical operating conditions. The approach follows a non-parametric formulation of the impedance based Nyquist Stability Criterion. The hyperbolic

Π

equivalent formulation of the telegraph equation is adopted for modelling the submarine cable due to high capacitance that is distributed and thus the conventional 50 Hz

Π

-model is not sufficient anymore. Furthermore, the paper shows how to integrate the complex dynamics of wind turbines into the overall stability assessment through an impedance building algorithm. Finally, it is shown how to stabilise the collector grids by means of active control parameter changes and it has been observed that the star configuration of wind turbines is more favourable on account of stability and controllability. Full article

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30 pages, 3047 KiB

Open AccessEditor’s ChoiceArticle

OMEGAlpes, an Open-Source Optimisation Model Generation Tool to Support Energy Stakeholders at District Scale

by Sacha Hodencq, Mathieu Brugeron, Jaume Fitó, Lou Morriet, Benoit Delinchant and Frédéric Wurtz

Energies 2021, 14(18), 5928; https://doi.org/10.3390/en14185928 - 18 Sep 2021

Cited by 12 | Viewed by 2253

Abstract

Energy modelling is key in order to face the challenges of energy transition. There is a wide variety of modelling tools, depending on their purpose or study phase. This article summarises their main characteristics and highlights ones that are relevant when it comes [...] Read more.

Energy modelling is key in order to face the challenges of energy transition. There is a wide variety of modelling tools, depending on their purpose or study phase. This article summarises their main characteristics and highlights ones that are relevant when it comes to the preliminary design of energy studies at district scale. It introduces OMEGAlpes, a multi-carrier energy modelling tool to support stakeholders in the preliminary design of district-scale energy systems. OMEGAlpes is a Mixed-Integer Linear Programming (MILP) model generation tool for optimisation. It aims at making energy models accessible and understandable through its open-source development and the integration of energy stakeholders and their areas of responsibility into the models. A library of use cases developed with OMEGAlpes is presented and enables the presentation of past, current, and future development with the tool, opening the way for future developments and collaborations. Full article

(This article belongs to the Special Issue Energy Efficiency of Buildings at the District Scale)

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22 pages, 1479 KiB

Open AccessEditor’s ChoiceArticle

Comparison of AC and DC Nanogrid for Office Buildings with EV Charging, PV and Battery Storage

by Ilman Sulaeman, Gautham Ram Chandra Mouli, Aditya Shekhar and Pavol Bauer

Energies 2021, 14(18), 5800; https://doi.org/10.3390/en14185800 - 14 Sep 2021

Cited by 13 | Viewed by 2381

Abstract

Future office buildings are expected to be integrated with energy intensive, inherently DC components such as photovoltaic panels (PV), electric vehicles (EV), LED lighting, and battery storage. This paper conceptualizes the interconnection of these components through a 750 V DC nanogrid as against [...] Read more.

Future office buildings are expected to be integrated with energy intensive, inherently DC components such as photovoltaic panels (PV), electric vehicles (EV), LED lighting, and battery storage. This paper conceptualizes the interconnection of these components through a 750 V DC nanogrid as against a conventional three-phase 400 V AC system. The factors influencing the performance of a DC-based nanogrid are identified and a comparative analysis with respect to a conventional AC nanogrid is presented in terms of efficiency, stability, and protection. It is proved how the minimization of grid energy exchange through power management is a vital system design choice. Secondly, the trade-off between stability, protection, and cost for sizing of the DC buffer capacitors is explored. The transient system response to different fault conditions for both AC and DC nanogrid is investigated. Finally the differences between the two systems in terms of various safety aspects are highlighted. Full article

(This article belongs to the Special Issue Direct Current (DC) Distribution Grids and Microgrids)

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18 pages, 4050 KiB

Open AccessEditor’s ChoiceArticle

Reinforcement Learning for Energy-Storage Systems in Grid-Connected Microgrids: An Investigation of Online vs. Offline Implementation

by Khawaja Haider Ali, Marvin Sigalo, Saptarshi Das, Enrico Anderlini, Asif Ali Tahir and Mohammad Abusara

Energies 2021, 14(18), 5688; https://doi.org/10.3390/en14185688 - 9 Sep 2021

Cited by 10 | Viewed by 3634

Abstract

Grid-connected microgrids consisting of renewable energy sources, battery storage, and load require an appropriate energy management system that controls the battery operation. Traditionally, the operation of the battery is optimised using 24 h of forecasted data of load demand and renewable energy sources [...] Read more.

Grid-connected microgrids consisting of renewable energy sources, battery storage, and load require an appropriate energy management system that controls the battery operation. Traditionally, the operation of the battery is optimised using 24 h of forecasted data of load demand and renewable energy sources (RES) generation using offline optimisation techniques, where the battery actions (charge/discharge/idle) are determined before the start of the day. Reinforcement Learning (RL) has recently been suggested as an alternative to these traditional techniques due to its ability to learn optimal policy online using real data. Two approaches of RL have been suggested in the literature viz. offline and online. In offline RL, the agent learns the optimum policy using predicted generation and load data. Once convergence is achieved, battery commands are dispatched in real time. This method is similar to traditional methods because it relies on forecasted data. In online RL, on the other hand, the agent learns the optimum policy by interacting with the system in real time using real data. This paper investigates the effectiveness of both the approaches. White Gaussian noise with different standard deviations was added to real data to create synthetic predicted data to validate the method. In the first approach, the predicted data were used by an offline RL algorithm. In the second approach, the online RL algorithm interacted with real streaming data in real time, and the agent was trained using real data. When the energy costs of the two approaches were compared, it was found that the online RL provides better results than the offline approach if the difference between real and predicted data is greater than 1.6%. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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25 pages, 2698 KiB

Open AccessEditor’s ChoiceArticle

Development of a Unified Taxonomy for HVAC System Faults

by Yimin Chen, Guanjing Lin, Eliot Crowe and Jessica Granderson

Energies 2021, 14(17), 5581; https://doi.org/10.3390/en14175581 - 6 Sep 2021

Cited by 23 | Viewed by 3335

Abstract

Detecting and diagnosing HVAC faults is critical for maintaining building operation performance, reducing energy waste, and ensuring indoor comfort. An increasing deployment of commercial fault detection and diagnostics (FDD) software tools in commercial buildings in the past decade has significantly increased buildings’ operational [...] Read more.

Detecting and diagnosing HVAC faults is critical for maintaining building operation performance, reducing energy waste, and ensuring indoor comfort. An increasing deployment of commercial fault detection and diagnostics (FDD) software tools in commercial buildings in the past decade has significantly increased buildings’ operational reliability and reduced energy consumption. A massive amount of data has been generated by the FDD software tools. However, efficiently utilizing FDD data for ‘big data’ analytics, algorithm improvement, and other data-driven applications is challenging because the format and naming conventions of those data are very customized, unstructured, and hard to interpret. This paper presents the development of a unified taxonomy for HVAC faults. A taxonomy is an orderly classification of HVAC faults according to their characteristics and causal relations. The taxonomy includes fault categorization, physical hierarchy, fault library, relation model, and naming/tagging scheme. The taxonomy employs both a physical hierarchy of HVAC equipment and a cause-effect relationship model to reveal the root causes of faults in HVAC systems. A structured and standardized vocabulary library is developed to increase data representability and interpretability. The developed fault taxonomy can be used for HVAC system ‘big data’ analytics such as HVAC system fault prevalence analysis or the development of an HVAC FDD software standard. A common type of HVAC equipment-packaged rooftop unit (RTU) is used as an example to demonstrate the application of the developed fault taxonomy. Two RTU FDD software tools are used to show that after mapping FDD data according to the taxonomy, the meta-analysis of the multiple FDD reports is possible and efficient. Full article

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13 pages, 1694 KiB

Open AccessEditor’s ChoiceArticle

Material Flux through an Innovative Recycling Process Treating Different Types of End-of-Life Photovoltaic Panels: Demonstration at Pilot Scale

by Flavia Carla dos Santos Martins Padoan, Pier Giorgio Schiavi, Gianmaria Belardi, Pietro Altimari, Antonio Rubino and Francesca Pagnanelli

Energies 2021, 14(17), 5534; https://doi.org/10.3390/en14175534 - 4 Sep 2021

Cited by 7 | Viewed by 2011

Abstract

A quantitative assessment of the material flux emerging from a pilot plant for the treatment of end-of-life photovoltaic panel waste was reported. The process included the manual dismantling of aluminum frames, mechanical treatment for size reduction, and the physical treatment of the milled [...] Read more.

A quantitative assessment of the material flux emerging from a pilot plant for the treatment of end-of-life photovoltaic panel waste was reported. The process included the manual dismantling of aluminum frames, mechanical treatment for size reduction, and the physical treatment of the milled materials for the release of coarse glass from the encapsulant polymer. Demonstration activities were performed using 1 ton of Si-, 1 ton of CdTe-, and 1 ton of CIGS-based photovoltaic panels (investigated separately), confirming the ability of the process to treat different photovoltaic technologies. The characterization of the input materials was performed and compared with previous literature data. The major bottleneck in the definition of an effective process option for the treatment of different panel technologies was emphasized by the high heterogeneity reported. Mass balances for the proposed process were derived by the recovered material flow. It was highlighted that in processes based on mechanical treatments, producing predominantly coarse fractions allows for the facile separation of most of the valuable components. In this perspective, the present work offers further insights into the design of recycling process to reach increased profitability/sustainability, especially considering the distributions of valuable metals in the process products. Full article

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16 pages, 10773 KiB

Open AccessEditor’s ChoiceArticle

A GIS-Based Procedure for Estimating the Energy Demand Profiles of Buildings towards Urban Energy Policies

by Simone Ferrari, Federica Zagarella, Paola Caputo and Giuliano Dall’O’

Energies 2021, 14(17), 5445; https://doi.org/10.3390/en14175445 - 1 Sep 2021

Cited by 15 | Viewed by 2993

Abstract

Assessing the existing building stock’s hourly energy demand and predicting its variation due to energy efficiency measures are fundamental for planning strategies towards renewable-based Smart Energy Systems. However, the need for accurate methods for this purpose in the literature arises. The present article [...] Read more.

Assessing the existing building stock’s hourly energy demand and predicting its variation due to energy efficiency measures are fundamental for planning strategies towards renewable-based Smart Energy Systems. However, the need for accurate methods for this purpose in the literature arises. The present article describes a GIS-based procedure developed for estimating the energy demand profiles of urban buildings based on the definition of the volumetric consistency of a building stock, characterized by different ages of construction and the most widespread uses, as well as dynamic simulations of a set of Building Energy Models adopting different energy-related features. The simulation models are based on a simple Building Energy Concept where selected thermal zones, representative of different boundary conditions options, are accounted. By associating the simulated hourly energy density profiles to the geo-referenced building stock and to the surveyed thermal system types, the whole hourly energy profile is estimated for the considered area. The method was tested on the building stock of Milan (Italy) and validated with the data available from the annual energy balance of the city. This procedure could support energy planners in defining urban energy demand profiles for energy policy scenarios. Full article

(This article belongs to the Special Issue Energy Performance, Management and Recovery in Buildings)

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16 pages, 9023 KiB

Open AccessEditor’s ChoiceArticle

Analysis and Experimental Verification of the Demagnetization Vulnerability in Various PM Synchronous Machine Configurations for an EV Application

by Gilsu Choi

Energies 2021, 14(17), 5447; https://doi.org/10.3390/en14175447 - 1 Sep 2021

Cited by 10 | Viewed by 3017

Abstract

Safety is a critical feature for all passenger vehicles, making fail–safe operation of the traction drive system highly important. Increasing demands for traction drives that can operate in challenging environments over wide constant power speed ranges expose permanent magnet (PM) machines to conditions [...] Read more.

Safety is a critical feature for all passenger vehicles, making fail–safe operation of the traction drive system highly important. Increasing demands for traction drives that can operate in challenging environments over wide constant power speed ranges expose permanent magnet (PM) machines to conditions that can cause irreversible demagnetization of rotor magnets. In this paper, a comprehensive analysis of the demagnetization vulnerability in PM machines for an electric vehicle (EV) application is presented. The first half of the paper presents rotor demagnetization characteristics of several different PM machines to investigate the impact of different design configurations on demagnetization and to identify promising machine geometries that have higher demagnetization resistance. Experimental verification results of rotor demagnetization in an interior PM (IPM) machine are presented in the latter half of the paper. The experimental tests were carried out on a specially designed locked-rotor test setup combined with closed-loop magnet temperature control. Experimental results confirm that both local and global demagnetization damage can be accurately predicted by time-stepped finite element (FE) analysis. Full article

(This article belongs to the Special Issue Design and Application of Electrical Machines)

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28 pages, 6377 KiB

Open AccessEditor’s ChoiceArticle

A Simulation Study on Risks to Wind Turbine Arrays from Thunderstorm Downbursts in Different Atmospheric Stability Conditions

by Nan-You Lu, Lance Manuel, Patrick Hawbecker and Sukanta Basu

Energies 2021, 14(17), 5407; https://doi.org/10.3390/en14175407 - 31 Aug 2021

Cited by 3 | Viewed by 2339

Abstract

Thunderstorm downbursts have been reported to cause damage or failure to wind turbine arrays. We extend a large-eddy simulation model used in previous work to generate downburst-related inflow fields with a view toward defining correlated wind fields that all turbines in an array [...] Read more.

Thunderstorm downbursts have been reported to cause damage or failure to wind turbine arrays. We extend a large-eddy simulation model used in previous work to generate downburst-related inflow fields with a view toward defining correlated wind fields that all turbines in an array would experience together during a downburst. We are also interested in establishing what role contrasting atmospheric stability conditions can play on the structural demands on the turbines. This interest is because the evening transition period, when thunderstorms are most common, is also when there is generally acknowledged time-varying stability in the atmospheric boundary layer. Our results reveal that the structure of a downburst’s ring vortices and dissipation of its outflow play important roles in the separate inflow fields for turbines located at different parts of the array; these effects vary with stability. Interacting with the ambient winds, the outflow of a downburst is found to have greater impacts in an “average” sense on structural loads for turbines farther from the touchdown center in the stable cases. Worst-case analyses show that the largest extreme loads, although somewhat dependent on the specific structural load variable considered, depend on the location of the turbine and on the prevailing atmospheric stability. The results of our calculations show the highest simulated foreaft tower bending moment to be 85.4 MN-m, which occurs at a unit sited in the array farther from touchdown center of the downburst initiated in a stable boundary layer. Full article

(This article belongs to the Special Issue Recent Advances in Wind Power Meteorology)

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33 pages, 1028 KiB

Open AccessEditor’s ChoiceArticle

A Critical Look at Coulomb Counting Approach for State of Charge Estimation in Batteries

by Kiarash Movassagh, Arif Raihan, Balakumar Balasingam and Krishna Pattipati

Energies 2021, 14(14), 4074; https://doi.org/10.3390/en14144074 - 6 Jul 2021

Cited by 115 | Viewed by 9744

Abstract

In this paper, we consider the problem of state-of-charge estimation for rechargeable batteries. Coulomb counting is a well-known method for estimating the state of charge, and it is regarded as accurate as long as the battery capacity and the beginning state of charge [...] Read more.

In this paper, we consider the problem of state-of-charge estimation for rechargeable batteries. Coulomb counting is a well-known method for estimating the state of charge, and it is regarded as accurate as long as the battery capacity and the beginning state of charge are known. The Coulomb counting approach, on the other hand, is prone to inaccuracies from a variety of sources, and the magnitude of these errors has not been explored in the literature. We formally construct and quantify the state-of-charge estimate error during Coulomb counting due to four types of error sources: (1) current measurement error; (2) current integration approximation error; (3) battery capacity uncertainty; and (4) timing oscillator error/drift. It is demonstrated that the state-of-charge error produced can be either time-cumulative or state-of-charge-proportional. Time-cumulative errors accumulate over time and have the potential to render the state-of-charge estimation utterly invalid in the long term.The proportional errors of the state of charge rise with the accumulated state of charge and reach their worst value within one charge/discharge cycle. The study presents methods for reducing time-cumulative and state-of-charge-proportional mistakes through simulation analysis. Full article

(This article belongs to the Special Issue Enhancement of Battery Lifespan, Safety, and Performance through Estimation and Control Theory and Algorithms)

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20 pages, 1872 KiB

Open AccessEditor’s ChoiceArticle

The Effectiveness of Energy Cooperatives Operating on the Capacity Market

by Jakub Jasiński, Mariusz Kozakiewicz and Maciej Sołtysik

Energies 2021, 14(11), 3226; https://doi.org/10.3390/en14113226 - 31 May 2021

Cited by 26 | Viewed by 3010

Abstract

The European Green Deal aims to make Europe the world’s first climate-neutral continent by 2050 by shifting to a clean circular economy, combating biodiversity loss and reducing pollution levels. In Poland, whose economy invariably remains one of the most dependent on coal consumption [...] Read more.

The European Green Deal aims to make Europe the world’s first climate-neutral continent by 2050 by shifting to a clean circular economy, combating biodiversity loss and reducing pollution levels. In Poland, whose economy invariably remains one of the most dependent on coal consumption in Europe, institutional responses to the above EU objectives have taken the shape of energy cooperatives aimed at filling the gaps in the development of the civic dimension of energy on a local scale and the use of potential renewable energy sources in rural areas, including in relation to the agricultural sector. This article is a continuation of the authors’ previous research work, which has so far focused on the analysis of the development of profitability of Polish institutions that fit into the European idea of a “local energy community”, which includes energy cooperatives. In this research paper, they present the results of subsequent research work and analyses performed on the basis of it which, on the one hand, complement the previously developed optimization model with variables concerning actual energy storage and, on the other hand, analyze the profitability of the operation of energy cooperatives in the conditions of the “capacity market”. The latter was actually introduced in Poland at the beginning of 2021. The research took account of the characteristics of energy producers and consumers in rural areas of Poland, the legally defined rules for the operation of the capacity market and the institutional conditions for the operation of energy cooperatives that can use the potential of energy storage. A dedicated mathematical model in mixed integer programming technology was used, enriched with respect to previous research, making it possible to optimize the operation of energy cooperative with the use of actual energy storage (batteries). Conclusions from the research and simulation show that the installation of energy storage only partially minimizes the volume of energy drawn from the grid in periods when fees related to the capacity market are in force (which should be avoided due to higher costs for consumers). The analysis also indicates that a key challenge is the proper parameterization of energy storage. Full article

(This article belongs to the Special Issue Energy Sources from Agriculture and Rural Areas)

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16 pages, 3666 KiB

Open AccessEditor’s ChoiceArticle

Forecasting Charging Demand of Electric Vehicles Using Time-Series Models

by Yunsun Kim and Sahm Kim

Energies 2021, 14(5), 1487; https://doi.org/10.3390/en14051487 - 9 Mar 2021

Cited by 55 | Viewed by 7415

Abstract

This study compared the methods used to forecast increases in power consumption caused by the rising popularity of electric vehicles (EVs). An excellent model for each region was proposed using multiple scaled geographical datasets over two years. EV charging volumes are influenced by [...] Read more.

This study compared the methods used to forecast increases in power consumption caused by the rising popularity of electric vehicles (EVs). An excellent model for each region was proposed using multiple scaled geographical datasets over two years. EV charging volumes are influenced by various factors, including the condition of a vehicle, the battery’s state-of-charge (SOC), and the distance to the destination. However, power suppliers cannot easily access this information due to privacy issues. Despite a lack of individual information, this study compared various modeling techniques, including trigonometric exponential smoothing state space (i.e., Trigonometric, Box–Cox, Auto-Regressive-Moving-Average (ARMA), Trend, and Seasonality (TBATS)), autoregressive integrated moving average (ARIMA), artificial neural networks (ANN), and long short-term memory (LSTM) modeling, based on past values and exogenous variables. The effect of exogenous variables was evaluated in macro- and micro-scale geographical areas, and the importance of historic data was verified. The basic statistics regarding the number of charging stations and the volume of charging in each region are expected to aid the formulation of a method that can be used by power suppliers. Full article

(This article belongs to the Special Issue Electric Vehicle Charging Networks)

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15 pages, 26179 KiB

Open AccessEditor’s ChoiceArticle

A Di-Carbazole-Based Dye as a Potential Sensitizer for Greenhouse-Integrated Dye-Sensitized Solar Cells

by Dimitris A. Chalkias, Christos Charalampopoulos, Stefania Aivali, Aikaterini K. Andreopoulou, Aggeliki Karavioti and Elias Stathatos

Energies 2021, 14(4), 1159; https://doi.org/10.3390/en14041159 - 22 Feb 2021

Cited by 18 | Viewed by 3596

Abstract

For the first time in dye-sensitized solar cell (DSSC) technology, a di-carbazole-based dye was synthesized and evaluated for its usage as a potential sensitizer for the development of wavelength selective semi-transparent DSSCs for greenhouses-oriented applications. The dye was designed to demonstrate a blue [...] Read more.

For the first time in dye-sensitized solar cell (DSSC) technology, a di-carbazole-based dye was synthesized and evaluated for its usage as a potential sensitizer for the development of wavelength selective semi-transparent DSSCs for greenhouses-oriented applications. The dye was designed to demonstrate a blue light absorption, allowing a high transmittance in the red region of the visible light, even after its adsorption on the anode semiconductor, which is the most important one for the photosynthetic action of the plants. The application of the new dye to DSSCs was examined using either a high-performance iodide-based electrolyte or a highly transparent iodine-free electrolyte to determine a good balance between electric power generation and device transparency. The spectral engineered DSSCs demonstrated quite promising characteristics, providing a high external quantum efficiency (higher than 70%) in the whole blue–green region of the visible light, while allowing high transparency (up to 55%) in the red region, where the second peak in the absorbance spectrum of chlorophyll is located. Finally, the derived results were discussed under the consideration of important metrics for this niche application, including the transparency of the solar cells in the region of photosynthetic active radiation and the attained crop growth factor. The present work constitutes one of the few comprehensive studies carried out up to now in the direction of the development of 3rd generation “agrivoltaics” for their possible integration as cladding materials in energy-autonomous greenhouses. Full article

(This article belongs to the Special Issue Next Generation of Dye-Sensitized Solar Cells)

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13 pages, 280 KiB

Open AccessEditor’s ChoiceArticle

Coopetitive Nature of Energy Communities—The Energy Transition Context

by Karolina Mucha-Kuś, Maciej Sołtysik, Krzysztof Zamasz and Katarzyna Szczepańska-Woszczyna

Energies 2021, 14(4), 931; https://doi.org/10.3390/en14040931 - 10 Feb 2021

Cited by 44 | Viewed by 4083

Abstract

The decentralization of the large-scale energy sector, its replacement with pro-ecological, dispersed production sources and building a citizen dimension of the energy sector are the directional objectives of the energy transformation in the European Union. Building energy self-sufficiency at a local level is [...] Read more.

The decentralization of the large-scale energy sector, its replacement with pro-ecological, dispersed production sources and building a citizen dimension of the energy sector are the directional objectives of the energy transformation in the European Union. Building energy self-sufficiency at a local level is possible, based on the so-called Energy Communities, which include energy clusters and energy cooperatives. Several dozen pilot projects for energy clusters have been implemented in Poland, while energy cooperatives, despite being legally sanctioned and potentially a simpler formula of operation, have not functioned in practice. This article presents the coopetitive nature of Energy Communities. The authors analysed the principles and benefits of creating Energy Communities from a regulatory and practical side. An important element of the analysis is to indicate the managerial, coopetitive nature of the strategies implemented within the Energy Communities. Their members, while operating in a competitive environment, simultaneously cooperate to achieve common benefits. On the basis of the actual data of recipients and producers, the results of simulations of benefits in the economic dimension will be presented, proving the thesis of the legitimacy of creating coopetitive structures of Energy Communities. Full article

(This article belongs to the Special Issue Economic and Policy Challenges of the Energy Transition in CEE Countries)

19 pages, 1231 KiB

Open AccessEditor’s ChoiceArticle

Confronting Energy Poverty in Europe: A Research and Policy Agenda

by Stefan Bouzarovski, Harriet Thomson and Marine Cornelis

Energies 2021, 14(4), 858; https://doi.org/10.3390/en14040858 - 7 Feb 2021

Cited by 110 | Viewed by 12436

Abstract

This paper scrutinizes existing policy efforts to address energy poverty at the governance scale of the European Union (EU) and its constituent Member States. Our main starting point is the recent expansion of energy poverty policies at the EU level, fuelled by the [...] Read more.

This paper scrutinizes existing policy efforts to address energy poverty at the governance scale of the European Union (EU) and its constituent Member States. Our main starting point is the recent expansion of energy poverty policies at the EU level, fuelled by the regulatory provisions of the Clean Energy for all Europeans Package, as well as the establishment of an EU Energy Poverty Observatory. Aided by a systematic and customized methodology, we survey the extensive scientific body of work that has recently been published on the topic, as well as the multiple strategies and measures to address energy poverty that have been formulated across the EU. This includes the principal mitigation approaches adopted by key European and national institutions. We develop a framework to judge the distributional and procedural justice provisions within the recently adopted National Energy and Climate Plans, as an indicator of the power, ability and resolve of relevant institutions to combat the causes and consequences of energy injustice. We also provide a research and policy agenda for future action, highlighting a series of scientific and decision-making challenges in the European and global context. Full article

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

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14 pages, 997 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of Urban Tree Leaf Biomass-Potential, Physico-Mechanical and Chemical Parameters of Raw Material and Solid Biofuel

by Krzysztof Mudryk, Marcin Jewiarz, Marek Wróbel, Marcin Niemiec and Arkadiusz Dyjakon

Energies 2021, 14(4), 818; https://doi.org/10.3390/en14040818 - 4 Feb 2021

Cited by 25 | Viewed by 3979

Abstract

The paper presents the results of research aimed at evaluating the possibility of using selected tree leaf species to produce solid biofuels. The possibility of production of qualitative solid biofuels from urban tree leaves meets the expectations of the municipal sector. Collection of [...] Read more.

The paper presents the results of research aimed at evaluating the possibility of using selected tree leaf species to produce solid biofuels. The possibility of production of qualitative solid biofuels from urban tree leaves meets the expectations of the municipal sector. Collection of tree leaves in urban areas is very often necessary for road safety reasons, the need to collect biomass rich in dust and pollution as well as biomass infested with pests. The production of solid biofuels from tree leaves allows for effective management of this raw material with energy recovery. The performed research indicates such a possibility, and the obtained ash is used as a soil improver. The conducted research showed that the biomass of leaves of five tree species used in the experiment can be a source of raw materials for production of qualitative biofuels. The obtained pellets were characterized by properties comparable to those of classical wood pellets. The lower heating value of the obtained pellets ranged from 14.5 to 15.5 MJ∙kg⁻¹. Physical properties of the obtained pellets described by bulk density (BD 600–660 kg∙m⁻³), mechanical durability (DU 90–96%), moisture (M_ar 10–12.5%) indicate that these products can be used in existing combustion equipment. Preliminary analysis of the obtained ashes (determination of ash melting point, bulk density) indicates that they should not cause difficulties in ash removal systems from the combustion chamber. Full article

(This article belongs to the Special Issue Biomass Pretreatment and Optimisation of Biofuel Production Processes)

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18 pages, 4698 KiB

Open AccessEditor’s ChoiceArticle

Effect of Soiling on Solar Photovoltaic Performance under Desert Climatic Conditions

by Idris Al Siyabi, Arwa Al Mayasi, Aiman Al Shukaili and Sourav Khanna

Energies 2021, 14(3), 659; https://doi.org/10.3390/en14030659 - 28 Jan 2021

Cited by 44 | Viewed by 4273

Abstract

The solar irradiation at the gulf Arabia is considered one of the highest in the world. However, this region is classified as a desert with high dust accumulation. Thus, the objective of this study is to analyze the effect of soiling and the [...] Read more.

The solar irradiation at the gulf Arabia is considered one of the highest in the world. However, this region is classified as a desert with high dust accumulation. Thus, the objective of this study is to analyze the effect of soiling and the photovoltaic (PV) tilt angle on the performance of 2.0 MWp of car park PV plant in Oman. Experimental measurements were taken and a model was developed for simulation. The power generation by the cleaned PV system was measured as 1460 kW around noon. After one week of operation, the power production (at the same irradiance level) reduced to 1390 kW due to soiling. It further reduced to 1196 kW and 904 kW after three and five weeks of operation, respectively. The results also show that a soiling-percentage of 7.5% reduced the monthly electricity generation (307 MWh) by 5.6% and a soiling-percentage of 12.5% reduced the generation by 10.8%. Furthermore, the increase in tilt is not recommended due to the duo-pitch canopy effect of the car park where the panels with 180° azimuth generate lower electricity than the panels with 0° azimuth. In addition, the part of the car park with 180° azimuth caused shading to the other part for high tilt angles. Full article

(This article belongs to the Special Issue Solar Photovoltaics and Solar Thermal Energy Systems)

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23 pages, 20071 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Sustainable Spatial Energy Planning of Large-Scale Wind and PV Farms in Israel: A Collaborative and Participatory Planning Approach

by Sofia Spyridonidou, Georgia Sismani, Eva Loukogeorgaki, Dimitra G. Vagiona, Hagit Ulanovsky and Daniel Madar

Energies 2021, 14(3), 551; https://doi.org/10.3390/en14030551 - 21 Jan 2021

Cited by 41 | Viewed by 4794

Abstract

In this work, an innovative sustainable spatial energy planning framework is developed on national scale for identifying and prioritizing appropriate, technically and economically feasible, environmentally sustainable as well as socially acceptable sites for the siting of large-scale onshore Wind Farms (WFs) and Photovoltaic [...] Read more.

In this work, an innovative sustainable spatial energy planning framework is developed on national scale for identifying and prioritizing appropriate, technically and economically feasible, environmentally sustainable as well as socially acceptable sites for the siting of large-scale onshore Wind Farms (WFs) and Photovoltaic Farms (PVFs) in Israel. The proposed holistic framework consists of distinctive steps allocated in two successive modules (the Planning and the Field Investigation module), and it covers all relevant dimensions of a sustainable siting analysis (economic, social, and environmental). It advances a collaborative and participatory planning approach by combining spatial planning tools (Geographic Information Systems (GIS)) and multi-criteria decision-making methods (e.g., Analytical Hierarchy Process (AHP)) with versatile participatory planning techniques in order to consider the opinion of three different participatory groups (public, experts, and renewable energy planners) within the site-selection processes. Moreover, it facilitates verification of GIS results by conducting appropriate field observations. Sites of high suitability, accepted by all participatory groups and field verified, form the final outcome of the proposed framework. The results illustrate the existence of high suitable sites for large-scale WFs’ and PVFs’ siting and, thus, the potential deployment of such projects towards the fulfillment of the Israeli energy targets in the near future. Full article

(This article belongs to the Special Issue GIS and Remote Sensing for Renewable Energy Assessment and Maps)

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23 pages, 682 KiB

Open AccessEditor’s ChoiceArticle

The Importance of Local Investments Co-Financed by the European Union in the Field of Renewable Energy Sources in Rural Areas of Poland

by Aldona Standar, Agnieszka Kozera and Łukasz Satoła

Energies 2021, 14(2), 450; https://doi.org/10.3390/en14020450 - 15 Jan 2021

Cited by 27 | Viewed by 3661

Abstract

Local investments for the development of renewable energy sources (RESs) constitute an important element of sustainable rural development. They are conducive to the social and economic development of the said areas, and improve the environmental values and living conditions of their inhabitants. However, [...] Read more.

Local investments for the development of renewable energy sources (RESs) constitute an important element of sustainable rural development. They are conducive to the social and economic development of the said areas, and improve the environmental values and living conditions of their inhabitants. However, such advancement in rural areas is not possible without adequate financial support, including the funds from the EU budget. Therefore, the main objective of the research is to assess the scale, scope and importance of local investments in renewable energy sources in rural areas of Poland in 2014–2020, cofinanced from EU funds. The study covered 1117 projects, whose beneficiaries were rural and urban–rural municipalities. Evaluation of the municipal investment activities in acquiring EU subsidies in the area of environmentally friendly energy was conducted using selected methods of descriptive statistics and the analysis of variance. Subsequently, with the use of logistic regression, the study identified the main socioeconomic, financial and environmental conditions of the investment activities of the local government entities in RES in rural areas. Empirical studies allowed for the positive verification of the research hypothesis, which assumed that “The highest investment activity in the field of local projects co-financed from EU funds, related to the development of RES in rural areas, may be attributed to municipalities performing primarily agricultural functions, located in Eastern Poland”. The municipalities’ own income potential and investment activity are of major importance for the acquisition of EU funds used in RES financing. Municipalities at a lower development level demonstrated a greater activity in accessing these funds. They view the development of RES as an opportunity for accelerated growth. Full article

(This article belongs to the Special Issue Energy Supply within Sustainable Agricultural Production: Challenges, Policies and Mechanisms)

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18 pages, 2889 KiB

Open AccessEditor’s ChoiceArticle

Effect of Thermal, Acoustic and Air Quality Perception Interactions on the Comfort and Satisfaction of People in Office Buildings

by Leonidas Bourikas, Stephanie Gauthier, Nicholas Khor Song En and Peiyao Xiong

Energies 2021, 14(2), 333; https://doi.org/10.3390/en14020333 - 9 Jan 2021

Cited by 33 | Viewed by 4977

Abstract

Current research on human comfort has identified a gap in the investigation of multi-domain perception interactions. There is a lack of understanding the interrelationships of different physio-socio-psychological factors and the manifestation of their contextual interactions into cross-modal comfort perception. In that direction, this [...] Read more.

Current research on human comfort has identified a gap in the investigation of multi-domain perception interactions. There is a lack of understanding the interrelationships of different physio-socio-psychological factors and the manifestation of their contextual interactions into cross-modal comfort perception. In that direction, this study used data from a post occupancy evaluation survey (n = 26), two longitudinal comfort studies (n = 1079 and n = 52) and concurrent measurements of indoor environmental quality factors (one building) to assess the effect of thermal, acoustic and air quality perception interactions on comfort and satisfaction of occupants in three mixed-mode university office buildings. The study concluded that thermal sensation (TSV) is associated with both air quality (ASV) and noise perception (NSV). The crossed effect of the interaction of air quality and noise perception on thermal sensation was not evident. The key finding was the significant correlation of operative temperature (T_op) with TSV as expected, but also with noise perception and overall acoustic comfort. Regarding the crossed main effects on thermal sensation, a significant effect was found for the interactions of (1) T_op and (2) sound pressure levels (SPL30) with air quality perception respectively. Most importantly, this study has highlighted the importance of air quality perception in achieving occupants’ comfort and satisfaction with office space. Full article

(This article belongs to the Special Issue Procedures and Methodologies for the Control and Improvement of Energy-Environmental Quality in Construction)

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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 38 | Viewed by 4870

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 49 | Viewed by 4656

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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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 60 | Viewed by 6481

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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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 63 | Viewed by 4633

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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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 23 | Viewed by 3531

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 76 | Viewed by 4749

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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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 40 | Viewed by 5910

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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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 25 | Viewed by 3417

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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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 17 | Viewed by 3666

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 15 | Viewed by 3380

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 29 | Viewed by 3424

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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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 15 | Viewed by 3615

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 10 | Viewed by 2179

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 45 | Viewed by 4893

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 24 | Viewed by 3464

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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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 9 | Viewed by 4277

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 45 | Viewed by 5609

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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