Energies

Article

21 pages, 2088 KiB

Open AccessEditor’s ChoiceArticle

Roadmap to a Sustainable Energy System: Is Uncertainty a Major Barrier to Investments for Building Energy Retrofit Projects in Wide City Compartments?

by Laura Gabrielli, Aurora Greta Ruggeri and Massimiliano Scarpa

Energies 2023, 16(11), 4261; https://doi.org/10.3390/en16114261 - 23 May 2023

Cited by 4 | Viewed by 1507

Abstract

Along the roadmap to a Sustainable Real Estate-Scape, energy retrofit campaigns on wide city compartments represent a pivotal task, where the importance of the collaboration between the public and private sectors is crucial. Energy retrofit programs on building assets are subject to multiple [...] Read more.

Along the roadmap to a Sustainable Real Estate-Scape, energy retrofit campaigns on wide city compartments represent a pivotal task, where the importance of the collaboration between the public and private sectors is crucial. Energy retrofit programs on building assets are subject to multiple uncertainty factors (e.g., climate, energy-economy forecasts, etc.) that act as a primary barrier to investment in this field. This paper aims to discuss risk management techniques to understand better how to deal with this kind of uncertainty. The research specifically addresses the techniques of sensitivity analysis and Monte Carlo simulation, focusing first on the phase of variables selection and their probability definition, including climatic, environmental, energy, economic, financial, and stochastic parameters. In this article, it is suggested to include correlation coefficients in the input variables of risk analysis, preferring the two-dimension Monte Carlo simulation to its simple version, since the results are more reliable when separating aleatory from epistemic uncertainty; thus, the results are more reliable. Moreover, it is seen how a sensitivity analysis based on percentile variations of the inputs provides a more accurate representation of risk if compared to the most common sensitivity analysis based on percentage deviations of the inputs. Conducting a sensitivity analysis using percentile variations gives realistic and reliable results, reflecting the tailored definition of uncertainty around the inputs on the basis of specific market analyses or historical series. Full article

(This article belongs to the Special Issue Development in Smart and Energy-Efficient Buildings and Renewable Energy Systems)

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36 pages, 26895 KiB

Open AccessEditor’s ChoiceArticle

Optimal Inverter Control Strategies for a PV Power Generation with Battery Storage System in Microgrid

by Md Jahidur Rahman, Tahar Tafticht, Mamadou Lamine Doumbia and Iqbal Messaïf

Energies 2023, 16(10), 4228; https://doi.org/10.3390/en16104228 - 21 May 2023

Cited by 2 | Viewed by 1995

Abstract

Power generation from Renewable Energy Sources (RESs) is unpredictable due to climate or weather changes. Therefore, more control strategies are required to maintain the proper power supply in the entire microgrid. This paper presents a simulation scheme utilizing a solar system instanced by [...] Read more.

Power generation from Renewable Energy Sources (RESs) is unpredictable due to climate or weather changes. Therefore, more control strategies are required to maintain the proper power supply in the entire microgrid. This paper presents a simulation scheme utilizing a solar system instanced by Photovoltaic (PV) panels coupled to the grid, loads, and an energy storage device. At first, modeling the PV panels cell and their operation were analyzed. The synthesis of the adaptive notch filter was designed to compensate for the input currents. The power converter’s/inverter’s efficiency and control facility allowed us to link the energy storage system with an electrical grid. Several simulations were accomplished consistently with nonlinear control techniques for the simple inverter, multi-variable filter, notch filter, and without a filter. Finally, the performances of the nonlinear controller with various filters were carried out to regulate the DC bus of the proposed grid. The advantage of these controllers is compensating the reactive power and harmonic currents to obtain a disturbance-free power network. The overall installations and simulations were established using the Matlab/Simulink software. Full article

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21 pages, 866 KiB

Open AccessEditor’s ChoiceArticle

Optimal Operation of CCHP System Combined Electric Vehicles Considering Seasons

by Junchao Cheng, Yongyi Huang, Hongjing He, Abdul Matin Ibrahimi and Tomonobu Senjyu

Energies 2023, 16(10), 4229; https://doi.org/10.3390/en16104229 - 21 May 2023

Cited by 3 | Viewed by 1292

Abstract

Energy shortage has always been a problem that the world needs to face. The combined cooling, heating, and power (CCHP) system, as a multi-level energy utilization system that can provide cooling, heating, and electric energy simultaneously, is considered to have good development prospects [...] Read more.

Energy shortage has always been a problem that the world needs to face. The combined cooling, heating, and power (CCHP) system, as a multi-level energy utilization system that can provide cooling, heating, and electric energy simultaneously, is considered to have good development prospects in alleviating energy problems. In addition, because of the rapid development of electric vehicles (EVs), using EVs as power supply devices has become a hot topic of research. In this paper, EVs are combined with the CCHP system as new power supply equipment, and the influence of the season on the user’s cooling, heating, and power demand is considered. Aiming at the minimum economic cost, the system is optimized by using the PSO algorithm in two operating modes: following electricity load (FEL) and following thermal load (FTL). The final results show that the participation of EVs can reduce costs in both operating modes, especially in FTL mode, which can reduce costs by 4.58%, 13.61%, 12.74%, and 3.57% in spring, summer, autumn, and winter, respectively. In addition, the FEL mode is more economical in spring and winter, and the FTL mode is more economical in summer and winter. In addition, the

C O_{2}

emissions in FEL mode are always less than in FTL mode. Full article

(This article belongs to the Special Issue Multicriteria Analysis for Energy Transition: A Route for Reaching Sustainable Development Goals)

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21 pages, 1336 KiB

Open AccessEditor’s ChoiceArticle

Multicriteria Optimisation of the Structure of a Hybrid Power Supply System for a Single-Family Housing Estate in Poland, Taking into Account Different Electromobility Development Scenarios

by Andrzej Tomczewski, Stanisław Mikulski, Adam Piotrowski, Sławomir Sowa and Krzysztof Wróbel

Energies 2023, 16(10), 4132; https://doi.org/10.3390/en16104132 - 16 May 2023

Cited by 1 | Viewed by 1141

Abstract

This article focuses on determining the optimum structure for a hybrid generation and storage system designed to power a single-family housing estate, taking into account the different number of electric vehicles in use and an assumed level of self-consumption of the generated energy. [...] Read more.

This article focuses on determining the optimum structure for a hybrid generation and storage system designed to power a single-family housing estate, taking into account the different number of electric vehicles in use and an assumed level of self-consumption of the generated energy. In terms of generation, two generation sections—wind and solar—and a lithium-ion container storage system will be taken into account. With regards to energy consumption, household load curves, determined on the basis of the tariff for residential consumers and modified by a random disturbance, will be taken into account, as well as the processes for charging electric cars with AC chargers, with power outputs ranging between 3.6 and 22 kW. Analyses were carried out for three locations in Poland—the Baltic Sea coast (good wind conditions), the Lublin Uplands (the best insolation in Poland) and the Carpathian foothills (poor wind and insolation conditions). The mathematical and numerical model of the system and the MOPSO (multiobjective particle swarm optimisation) algorithm were implemented in the Matlab environment. The results include Pareto fronts (three optimisation criteria: minimisation of energy storage capacity, minimisation of energy exchanged with the power grid and maximisation of the self-consumption rate) for the indicated locations and three electromobility development scenarios with determined NPVs (net present values) for a 20-year lifetime. The detailed results relate to the inclusion of an additional expert criterion in the form of a coupled payback period of no more than 10 years, a maximum NPV in the last year of operation and a self-consumption rate of at least 80%. The economic calculations take into account the decrease in PV installation capacity as a function of the year of operation, as well as changes in electricity and petrol prices and variations in energy prices at purchase and sale. Full article

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

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38 pages, 3618 KiB

Open AccessEditor’s ChoiceArticle

Why Does the PV Solar Power Plant Operate Ineffectively?

by Lina Alhmoud

Energies 2023, 16(10), 4074; https://doi.org/10.3390/en16104074 - 13 May 2023

Cited by 12 | Viewed by 4606

Abstract

Quality, reliability, and durability are the key features of photovoltaic (PV) solar system design, production, and operation. They are considered when manufacturing every cell and designing the entire system. Achieving these key features ensures that the PV solar system performs satisfactorily and offers [...] Read more.

Quality, reliability, and durability are the key features of photovoltaic (PV) solar system design, production, and operation. They are considered when manufacturing every cell and designing the entire system. Achieving these key features ensures that the PV solar system performs satisfactorily and offers years of trouble-free operation, even in adverse conditions. In each cell, the quality of the raw material should meet the quality standards. The fulfillment of the quality management system requires every part that goes into the PV solar system to undergo extensive testing in laboratories and environments to ensure it meets expectations. Hence, every MWh of electricity generated by the PV solar system is counted, the losses should be examined, and the PV system’s returns should be maximized. There are many types of losses in the PV solar system; these losses are identified and quantified based on knowledge and experience. They can be classified into two major blocks: optical and electrical losses. The optical losses include, but are not limited to, partial shading losses, far shading losses, near shading losses, incident angle modifier (IAM) losses, soiling losses, potential induced degradation (PID) losses, temperature losses, light-induced degradation (LID) losses, PV yearly degradation losses, array mismatch losses, and module quality losses. In addition, there are cable losses inside the PV solar power system, inverter losses, transformer losses, and transmission line losses. Thus, this work reviews the losses in the PV solar system in general and the 103 MWp grid-tied Al Quweira PV power plant/Aqaba, mainly using PVsyst software. The annual performance ratio (PR) is

79.5 %

, and the efficiency

(η)

under standard test conditions (STC) is

16.49 %

. The normalized production is 4.64 kWh/kWp/day, the array loss is 1.69 kWh/kWp/day, and the system loss is 0.18 kWh/kWp/day. Understanding factors that impact the PV system production losses is the key to obtaining an accurate production estimation. It enhances the annual energy and yield generated from the power plant. This review benefits investors, energy professionals, manufacturers, installers, and project developers by allowing them to maximize energy generation from PV solar systems and increase the number of solar irradiation incidents on PV modules. Full article

(This article belongs to the Special Issue Advances in Solar Systems and Energy Efficiency)

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22 pages, 7389 KiB

Open AccessEditor’s ChoiceArticle

Energy Management Strategies of Grid-Connected Microgrids under Different Reliability Conditions

by Mohammed Abdullah H. Alshehri, Youguang Guo and Gang Lei

Energies 2023, 16(9), 3951; https://doi.org/10.3390/en16093951 - 8 May 2023

Cited by 2 | Viewed by 1435

Abstract

The demand for a reliable, cheap and environmentally friendly source of energy makes the integration of renewable energy into power networks a global challenge. Furthermore, reliability, as one of the core elements of efficient and cost-effective energy management options, is still among the [...] Read more.

The demand for a reliable, cheap and environmentally friendly source of energy makes the integration of renewable energy into power networks a global challenge. Furthermore, reliability, as one of the core elements of efficient and cost-effective energy management options, is still among the dominant factors/techniques that receive more attention for realistic penetrations of renewable energy into the electricity grid. This paper proposes an efficient way of energy management for a grid-connected microgrid. The grid-connected microgrid used in the analysis consists of solar photovoltaic (P.V.) and battery. In this microgrid configuration, oftentimes, the output power might not be equal to the system demand; in this regard, it is expected that the mismatch between these output powers is not zero. However, to reduce the mismatch between demand and supply to be close to zero, this paper proposes strategies of increasing the rated power of solar, battery and grid separately and combining them with a view of finding the cheapest option among these strategies. The results have shown that the cost increment for different options is USD 280.792, 84.48 and 48.204 for storage, P.V. and grid, respectively. These have shown that the storage option is the most expansive option for improving P.V. grid-connected microgrids. This is followed immediately by the P.V. option, which is weather dependent. On the other hand, the grid option is the cheapest option for system reliability improvement. This paper is expected to be useful to both new researchers and experts who are working in energy management with an emphasis on the reliability aspect. Full article

(This article belongs to the Special Issue Power Management for Distributed Generators Integrated System)

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20 pages, 634 KiB

Open AccessEditor’s ChoiceArticle

Maximising Distribution Grid Utilisation by Optimising E-Car Charging Using Smart Meter Gateway Data

by André Ulrich, Sergej Baum, Ingo Stadler, Christian Hotz and Eberhard Waffenschmidt

Energies 2023, 16(9), 3790; https://doi.org/10.3390/en16093790 - 28 Apr 2023

Cited by 1 | Viewed by 1679

Abstract

The transition towards climate neutrality will result in an increase in electrical vehicles, as well as other electric loads, leading to higher loads on electrical distribution grids. This paper presents an optimisation algorithm that enables the integration of more loads into distribution grid [...] Read more.

The transition towards climate neutrality will result in an increase in electrical vehicles, as well as other electric loads, leading to higher loads on electrical distribution grids. This paper presents an optimisation algorithm that enables the integration of more loads into distribution grid infrastructure using information from smart meters and/or smart meter gateways. To achieve this, a mathematical programming formulation was developed and implemented. The algorithm determines the optimal charging schedule for all electric vehicles connected to the distribution grid, taking into account various criteria to avoid violating physical grid limitations and ensuring non-discriminatory charging of all electric vehicles on the grid while also optimising grid operation. Additionally, the expandability of the infrastructure and fail-safe operation are considered through the decentralisation of all components. Various scenarios are modelled and evaluated in a simulation environment. The results demonstrate that the developed optimisation algorithm allows for higher transformer loads compared to a P(U) control approach, without causing grid overload as observed in scenarios without optimisation or P(U) control. Full article

(This article belongs to the Special Issue Selected Papers from the SDEWES 2022 Conference on Sustainable Development of Energy, Water, and Environment Systems)

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28 pages, 12334 KiB

Open AccessEditor’s ChoiceArticle

Power Quality Analysis Based on Machine Learning Methods for Low-Voltage Electrical Distribution Lines

by Carlos Alberto Iturrino Garcia, Marco Bindi, Fabio Corti, Antonio Luchetta, Francesco Grasso, Libero Paolucci, Maria Cristina Piccirilli and Igor Aizenberg

Energies 2023, 16(9), 3627; https://doi.org/10.3390/en16093627 - 23 Apr 2023

Cited by 6 | Viewed by 3227

Abstract

The main objective of this paper is to propose two innovative monitoring methods for electrical disturbances in low-voltage networks. The two approaches present a focus on the classification of voltage signals in the frequency domain using machine learning techniques. The first technique proposed [...] Read more.

The main objective of this paper is to propose two innovative monitoring methods for electrical disturbances in low-voltage networks. The two approaches present a focus on the classification of voltage signals in the frequency domain using machine learning techniques. The first technique proposed here uses the Fourier transform (FT) of the voltage waveform and classifies the corresponding complex coefficients through a multilayered neural network with multivalued neurons (MLMVN). In this case, the classifier structure has three layers and a small number of neurons in the hidden layer. This allows complex-valued inputs to be processed without the need for pre-coding, thus reducing computational cost and keeping training time short. The second technique involves the use of the short-time Fourier transform (STFT) and a convolutional neural network (CNN) with 2D convolutions in each layer for feature extraction and dimensionality reduction. The voltage waveform perturbations taken into consideration are: voltage sag, voltage swell, harmonic pollution, voltage notch, and interruption. The comparison between the two proposed techniques is developed in two phases: initially, the simulated data used during the training phase are considered and, subsequently, various experimental measurements are processed, obtained both through an artificial disturbance generator and through a variable load. The two techniques represent an innovative approach to this problem and guarantee excellent classification results. Full article

(This article belongs to the Special Issue The Latest Advances in Power Quality Detection, Analysis, and Optimization)

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22 pages, 5568 KiB

Open AccessEditor’s ChoiceArticle

Formal Verification of the European Train Control System (ETCS) for Better Energy Efficiency Using a Timed and Asynchronous Model

by Andrzej Kochan, Wiktor B. Daszczuk, Waldemar Grabski and Juliusz Karolak

Energies 2023, 16(8), 3602; https://doi.org/10.3390/en16083602 - 21 Apr 2023

Cited by 3 | Viewed by 1935

Abstract

The ERTMS/ETCS is the newest automatic train protection system. This is a system that supports the driver in driving the train. It is currently being implemented throughout the European Union. This system’s latest specifications also provide additional functions to increase the energy efficiency [...] Read more.

The ERTMS/ETCS is the newest automatic train protection system. This is a system that supports the driver in driving the train. It is currently being implemented throughout the European Union. This system’s latest specifications also provide additional functions to increase the energy efficiency of train driving in the form of ATO (automatic train operation). These functions of the ETCS will be valuable, provided they operate without failure. To achieve errorless configuration of the ETCS, a methodology for automatic system verification using the IMDS (Integrated Model of Distributed Systems) formalism and the temporal tool Dedan was applied. The main contribution is asynchronous and timed verification, which appropriately models the distributed nature of the ETCS and allows the designer not only to analyze time dependencies but also to define the range of train velocities in which the operational scenario is valid. Additionally, the novelties of the presented verification methodology are the graphical design of the system components and automated verification freeing the designer from using textual design. We express the verified properties as observer automata rather than in temporal logic. Moreover, we check partial properties related to system fragments, which is crucial in distributed systems. This paper presents the verification of an example ETCS system application. The verification results are presented as sequence diagrams leading to a correct/incorrect final state. Full article

(This article belongs to the Special Issue Modeling of Quality, Reliability, and Exploitation for Power Supply Systems, ICT Systems, and Transportation Systems)

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23 pages, 7999 KiB

Open AccessEditor’s ChoiceArticle

Assessment of Power System Asset Dispatch under Different Local Energy Community Business Models

by Tarmo Korõtko, Freddy Plaum, Tobias Häring, Anna Mutule, Roberts Lazdins, Olegs Borščevskis, Argo Rosin and Paula Carroll

Energies 2023, 16(8), 3476; https://doi.org/10.3390/en16083476 - 16 Apr 2023

Cited by 6 | Viewed by 1871

Abstract

Community energy projects have gained popularity in recent years, and encouraging citizens to form local energy communities (LEC) is considered an effective tool for raising awareness about renewable energy. Since no single universal method exists for operating LECs, this study investigated the impact [...] Read more.

Community energy projects have gained popularity in recent years, and encouraging citizens to form local energy communities (LEC) is considered an effective tool for raising awareness about renewable energy. Since no single universal method exists for operating LECs, this study investigated the impact that different business models and asset dispatch methods have on LECs’ economic and energy-related indicators. We carried out a case study, which included the development, modelling, and simulation of seven scenarios using mixed-integer linear programming (MILP). To measure and compare the prospective performance of the LECs in each scenario, six key metrics were evaluated and assessed. The authors find that simple, rule-based control systems might be well suited for LECs with a limited number of controllable assets that aim to provide increased levels of self-consumption of up to 3%. We also conclude that when the LEC utilises an energy cooperative business model, the selected asset dispatch method provides only minor differences in LEC performance, while for prosumer communities, the importance of selecting a suitable asset dispatch method is higher. We also conclude that LECs have the potential to significantly increase their economic performance by more than 10% by acting as aggregators and providing grid services directly to system operators. Full article

(This article belongs to the Topic Modeling, Optimization, and Control of Energy Systems)

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19 pages, 1983 KiB

Open AccessEditor’s ChoiceArticle

Research and Optimization of Hybrid On-Board Energy Storage System of an Electric Locomotive for Quarry Rail Transport

by Sergey Goolak, Liliia Kondratieva, Ievgen Riabov, Vaidas Lukoševičius, Artūras Keršys and Rolandas Makaras

Energies 2023, 16(7), 3293; https://doi.org/10.3390/en16073293 - 6 Apr 2023

Cited by 4 | Viewed by 1917

Abstract

Operation modes of rolling stock at mining enterprises are considered and analyzed. The justification of the need to replace it with a modern specialized electric locomotive for quarry railway transport, equipped with an asynchronous traction electric drive and an on-board energy storage system, [...] Read more.

Operation modes of rolling stock at mining enterprises are considered and analyzed. The justification of the need to replace it with a modern specialized electric locomotive for quarry railway transport, equipped with an asynchronous traction electric drive and an on-board energy storage system, is presented. The determination of the parameters and structure of the on-board energy storage system, based on the condition of power compensation with limited power consumption from the traction network and ensuring the autonomous movement of the electric locomotive, is considered. This study was carried out by modeling the processes of energy exchange in the traction system of an electric locomotive. The use of lithium cells and supercapacitors in energy storage is considered. Variants of the hybridization of energy storage were studied from the standpoint of minimizing the weight, size, and cost indicators. It was established that reducing the mass of the energy storage device, which includes lithium cells and supercapacitors, leads to an increase in the cost of one kilowatt-hour of energy storage capacity, which reduces the attractiveness of capital expenditures for the creation of such an energy storage device. Hybridization of the energy storage device by combining lithium cells of different types practically does not improve its weight, size, and cost indicators. The recommended option is a storage capacity of energy based on LTO elements, for which it is necessary to select elements in order to minimize weight, size, and cost indicators. Full article

(This article belongs to the Special Issue Forecasting and Optimization in Transport Energy Management Systems)

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19 pages, 1291 KiB

Open AccessEditor’s ChoiceArticle

Analysing Grid-Level Effects of Photovoltaic Self-Consumption Using a Stochastic Bottom-up Model of Prosumer Systems

by Steffen Karalus, Benedikt Köpfer, Philipp Guthke, Sven Killinger and Elke Lorenz

Energies 2023, 16(7), 3059; https://doi.org/10.3390/en16073059 - 27 Mar 2023

Cited by 3 | Viewed by 2653

Abstract

Self-consumption of the energy generated by photovoltaics (PV) is playing an increasingly important role in the power grid. “Prosumer” systems consume part of the produced energy directly to meet the local demand, which reduces the feed-in into as well as the demand from [...] Read more.

Self-consumption of the energy generated by photovoltaics (PV) is playing an increasingly important role in the power grid. “Prosumer” systems consume part of the produced energy directly to meet the local demand, which reduces the feed-in into as well as the demand from the grid. In order to analyse the effects of PV self-consumption in the power grid, we introduce a stochastic bottom-up model of PV power generation and local consumption in the control area of the German transmission system operator TransnetBW. We set up a realistic portfolio of more than 100,000 PV/prosumer systems to generate representative time series of PV generation and consumption as a basis to derive self-consumption and feed-in. This model allows for the investigation of the time-dependent behaviour in detail for the full portfolio whereas measurements are presently only available as aggregated feed-in time series over a nonrepresentative subset of systems. We analyse the variation of self-consumption with PV generation and consumption at the portfolio level and its seasonal, weekly and diurnal cycles. Furthermore, we study a scenario of 100% prosumers as a limiting case for a situation without subsidized feed-in tariffs and local energy storage. Full article

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

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16 pages, 4808 KiB

Open AccessEditor’s ChoiceArticle

Lifetime Limitations in Multi-Service Battery Energy Storage Systems

by Mathilda Ohrelius, Magnus Berg, Rakel Wreland Lindström and Göran Lindbergh

Energies 2023, 16(7), 3003; https://doi.org/10.3390/en16073003 - 25 Mar 2023

Cited by 1 | Viewed by 2826

Abstract

A reliable power grid system based on renewable energy sources is a crucial step to restrict the climate crisis. Stationary battery energy storage systems (BESS) offer a great potential to repel power fluctuations in the grid at different timescales. However, for a reliable [...] Read more.

A reliable power grid system based on renewable energy sources is a crucial step to restrict the climate crisis. Stationary battery energy storage systems (BESS) offer a great potential to repel power fluctuations in the grid at different timescales. However, for a reliable operation and cost estimation, the degradation in the batteries needs to be understood. We present an accelerated battery degradation study, on single as well as multi-service applications, of NCM532/Gr lithium-ion battery cells. Frequency regulation (FR) was the least harmful for the battery, with an expected lifetime of 12 years, while peak shaving (PS) resulted in an expected lifetime of 8 years. The combined cycle (FRPS) accelerated the capacity loss, and degradation of the positive electrode was induced from the start of cycling, causing power limitations after only 870 equivalent full cycles (EFC). Tracking the 1C-rate discharge capacity was proven to be a good indication of the accelerated cell polarization, and it can serve as a useful method to evaluate the internal battery state of health (SOH). Full article

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

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31 pages, 16465 KiB

Open AccessEditor’s ChoiceArticle

Extensive Experimental Characterization with Kinetic Data for the Gasification Simulation of Solid Biofuels

by Maximilian Robert Heinrich, André Herrmann, Andy Gradel, Marco Klemm and Tobias Plessing

Energies 2023, 16(6), 2888; https://doi.org/10.3390/en16062888 - 21 Mar 2023

Cited by 1 | Viewed by 1580

Abstract

In this study, biomass–specific gasification data is experimentally collected for numerical simulations of fixed–bed reactors. Since biomass properties vary, it is crucial to have characteristic biomass data. Extensive data is collected to determine an appropriate description of specific biomass behavior, including basic data [...] Read more.

In this study, biomass–specific gasification data is experimentally collected for numerical simulations of fixed–bed reactors. Since biomass properties vary, it is crucial to have characteristic biomass data. Extensive data is collected to determine an appropriate description of specific biomass behavior, including basic data (e.g., heating value, size, densities, ultimate and total analysis etc.), biomass pyrolysis and heterogeneous gasification reaction data. Heterogeneous reactions were comparatively investigated in the forms of powder, particles, and a fixed–bed. The powder was investigated in depth with CO₂, O₂, and H₂O (gas fraction 5–20 vol.%; temperature CO₂, O₂ and H₂O, respectively, at 730–790 °C, 360–405 °C, 720–780 °C), while particle reactions and fixed–bed reaction were only studied with CO₂. A model description for a fixed–bed batch reactor was applied, modified, and compared to experimental fixed–bed batch reactor results. This study concludes that determining the appropriate characteristic particle size and parameters for the porous structure of specific biomass char is essential for simulation based on preliminary biomass characterization. Therefore, in future investigations, the description for biomass-specific differences between powder, single particles, and bulk of biomass char may be of greater focus, also taking into consideration O₂ and H₂O. Full article

(This article belongs to the Special Issue Pyrolysis and Gasification of Biomass and Waste II)

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21 pages, 10009 KiB

Open AccessEditor’s ChoiceArticle

Development and Verification of Novel Building Integrated Thermal Storage System Models

by Matthias Pazold, Jan Radon, Matthias Kersken, Hartwig Künzel, Florian Antretter and Herbert Sinnesbichler

Energies 2023, 16(6), 2889; https://doi.org/10.3390/en16062889 - 21 Mar 2023

Cited by 1 | Viewed by 1668

Abstract

In electrical grids with a high renewable percentage, weather conditions have a greater impact on power generation. This can lead to the overproduction of electricity during periods of substantial wind power generation, resulting in shutoffs of wind turbines. To reduce such shutoffs and [...] Read more.

In electrical grids with a high renewable percentage, weather conditions have a greater impact on power generation. This can lead to the overproduction of electricity during periods of substantial wind power generation, resulting in shutoffs of wind turbines. To reduce such shutoffs and to bridge periods of lower electricity production, three thermal energy storage systems (TESs) have been developed for space heating and domestic hot water. These include a water-based thermal system (WBTS), a thermally activated building system (TABS), and a high-temperature stone storage system (HTSS). The paper explains the development of computer models used to simulate the systems and their successful verification using field measurements. Target values to cover about 90% of building heating demand with excess electricity were found to be achievable, with performance ratios depending on storage size, particularly for WBTS and HTSS. The TABS’ storage capacity is limited by building geometry and the available inner ceilings and walls. Full article

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

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21 pages, 13827 KiB

Open AccessEditor’s ChoiceArticle

A Modified Decentralized Droop Control Method to Eliminate Battery Short-Term Operation in a Hybrid Supercapacitor/Battery Energy Storage System

by Pavlos Papageorgiou, Konstantinos Oureilidis, Anna Tsakiri and Georgios Christoforidis

Energies 2023, 16(6), 2858; https://doi.org/10.3390/en16062858 - 20 Mar 2023

Cited by 4 | Viewed by 4480

Abstract

Employment of a battery energy storage system to compensate for the generation-consumption mismatch is a vital element for a resilient microgrid. However, the frequent (i.e., short-term) cyclic activity and the abrupt current variations (i.e., high di/dt) have adverse effects on the energy-type battery’s [...] Read more.

Employment of a battery energy storage system to compensate for the generation-consumption mismatch is a vital element for a resilient microgrid. However, the frequent (i.e., short-term) cyclic activity and the abrupt current variations (i.e., high di/dt) have adverse effects on the energy-type battery’s lifespan. On the other hand, the power-type supercapacitor energy storage system (SCES) has almost zero lifetime degradation when it is subjected to irregular charging/discharging patterns. Therefore, the hybridization between them can reduce battery stress levels. This study proposes a droop control algorithm with multiple segments for a SCES/battery hybrid energy storage system (HESS) that is employed in a solar/wind DC microgrid. The presented control scheme is decentralized since it avoids the central controller (CC) and the communication links between the controllers of SCES and battery units. To eliminate the short-term cyclic operation of the battery, the SCES regulates the bus voltage inside a narrow zone with a droop curve that exploits all its available energy capacity. Inside this zone, the battery is kept inactive. As soon as the bus voltage deviates from this band, the SCES enters the idle mode, and the battery is triggered following a droop curve different for charging or discharging mode to stabilize the bus voltage. To evaluate the effectiveness of the proposed system over a battery-only system and a hybrid SCES/battery system controlled with the classical droop method, a comparative analysis under different scenarios is presented. Full article

(This article belongs to the Special Issue Energy Transition in the Mediterranean Area)

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23 pages, 3959 KiB

Open AccessEditor’s ChoiceArticle

An Experimental Study on the Quantitative and Qualitative Characteristics of Tar Formed during Ex Situ Coal Gasification

by Marian Wiatowski

Energies 2023, 16(6), 2777; https://doi.org/10.3390/en16062777 - 16 Mar 2023

Cited by 5 | Viewed by 2626

Abstract

Over the three-day gasification test of a large coal block with oxygen in atmospheric pressure conditions, the yield and composition of the tar collected was investigated. The tar was sampled approximately every 7 h into sorption tubes directly from the reactor outlet. Sand, [...] Read more.

Over the three-day gasification test of a large coal block with oxygen in atmospheric pressure conditions, the yield and composition of the tar collected was investigated. The tar was sampled approximately every 7 h into sorption tubes directly from the reactor outlet. Sand, with a moisture content of 11%, was used as an insulating material to simulate the environment of the gasified coal seam. Light aromatic hydrocarbons (BTEX), phenols, and polycyclic aromatic hydrocarbons (PAHs) were determined in the tar. The results that were obtained were recalculated into the concentrations of the individual components of the tar and its mass stream in the process gas. The residence time of the tar in the reactor, its molar mass, and the H/C ratio were also calculated. As the reaction progressed, the water that was contained in the wet sand started to react with the gasified coal, which significantly affected the composition and amount of the obtained process gas and the produced tar. Due to an increase in the amount of generated gases and steam, the residence time of the tar vapours in the reactor decreased as the gasification progressed, ranging from approximately 1 s at the beginning of the process to 0.35 s at the end. The obtained tar was characterised by a high average content of BTEX fractions at approximately 82.6%, PAHs at 14.7%, and phenols at 2.7%. Benzene was the dominant BTEX compound, with a concentration of 83.7%. The high content of the BTEX compounds, especially benzene, was a result of secondary processes taking place in the tar (hydrocracking and steam reforming), and as a result of which, in the presence of hydrogen and steam, the heavier components of the tar were transformed into lighter ones. The total yield of the tar from this UCG (underground coal gasification) process—calculated per 1 ton of gasified coal—was 1.8% (counted on the basis of the analysed tar composition). Comparing this result to the efficiency of the classic coking process, the tar yield was about three times lower. Full article

(This article belongs to the Special Issue Underground Coal Gasification: Clean Technology of the Coal Energy Conversion)

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11 pages, 2092 KiB

Open AccessEditor’s ChoiceArticle

Electrochemical Insight into the Use of Microbial Fuel Cells for Bioelectricity Generation and Wastewater Treatment

by Asif Nadeem Tabish, Iqra Farhat, Muneeb Irshad, Muhammad Asif Hussain, Muhammad Usman, Tariq Nawaz Chaudhary, Yasser Fouad, Sohaib Raza, Waqar Muhammad Ashraf and Jaroslaw Krzywanski

Energies 2023, 16(6), 2760; https://doi.org/10.3390/en16062760 - 16 Mar 2023

Cited by 3 | Viewed by 2337

Abstract

Microbial fuel cell (MFC) technology is anticipated to be a practical alternative to the activated sludge technique for treating domestic and industrial effluents. The relevant literature mainly focuses on developing the systems and materials for maximum power output, whereas understanding the fundamental electrochemical [...] Read more.

Microbial fuel cell (MFC) technology is anticipated to be a practical alternative to the activated sludge technique for treating domestic and industrial effluents. The relevant literature mainly focuses on developing the systems and materials for maximum power output, whereas understanding the fundamental electrochemical characteristics is inadequate. This experimental study uses a double-chamber MFC having graphite electrodes and an anion-exchange membrane to investigate the electrochemical process limitations and the potential of bioelectricity generation and dairy effluent treatment. The results revealed an 81% reduction in the chemical oxygen demand (COD) in 10 days of cell operation, with an initial COD loading of 4520 mg/L. The third day recorded the highest open circuit voltage of 396 mV, and the maximum power density of 36.39 mW/m² was achieved at a current density of 0.30 A/m². The electrochemical impedance spectroscopy analysis disclosed that the activation polarization of the aerated cathode was the primary factor causing the cell’s resistance, followed by the ohmic and anodic activation overpotentials. Full article

(This article belongs to the Special Issue Recent Advancements in Microbial Fuel Cells)

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30 pages, 6667 KiB

Open AccessEditor’s ChoiceArticle

Open-Source Energy, Entropy, and Exergy 0D Heat Release Model for Internal Combustion Engines

by Christopher Depcik, Jonathan Mattson and Shah Saud Alam

Energies 2023, 16(6), 2514; https://doi.org/10.3390/en16062514 - 7 Mar 2023

Cited by 1 | Viewed by 2282

Abstract

Internal combustion engines face increased market, societal, and governmental pressures to improve performance, requiring researchers to utilize modeling tools capable of a thorough analysis of engine performance. Heat release is a critical aspect of internal combustion engine diagnostic analysis, but is prone to [...] Read more.

Internal combustion engines face increased market, societal, and governmental pressures to improve performance, requiring researchers to utilize modeling tools capable of a thorough analysis of engine performance. Heat release is a critical aspect of internal combustion engine diagnostic analysis, but is prone to variability in modeling validity, particularly as engine operation is pushed further from conventional combustion regimes. To that end, this effort presents a comprehensive open-source, zero-dimensional equilibrium heat release model. This heat release analysis is based on a combined mass, energy, entropy, and exergy formulation that improves upon well-established efforts constructed around the ratio of specific heats. Furthermore, it incorporates combustion using an established chemical kinetics mechanism to endeavor to predict the global chemical species in the cylinder. Future efforts can augment and improve the chemical kinetics reactions for specific combustion conditions based on the radical pyrolysis of the fuel. In addition, the incorporation of theoretical calculations of energy and exergy based on the change in chemical species allows for cross-checking of combustion model validity. Full article

(This article belongs to the Special Issue Internal Combustion Engine Performance 2022)

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17 pages, 1972 KiB

Open AccessEditor’s ChoiceArticle

SGAM-Based Analysis for the Capacity Optimization of Smart Grids Utilizing e-Mobility: The Use Case of Booking a Charge Session

by Moisés Antón García, Ana Isabel Martínez García, Stylianos Karatzas, Athanasios Chassiakos and Olympia Ageli

Energies 2023, 16(5), 2489; https://doi.org/10.3390/en16052489 - 6 Mar 2023

Cited by 2 | Viewed by 1889

Abstract

The description of the functionality of a smart grid’s architectural concept, analyzing different Smart Grid (SG) scenarios without disrupting the smooth operation of the individual processes, is a major challenge. The field of smart energy grids has been increasing in complexity since there [...] Read more.

The description of the functionality of a smart grid’s architectural concept, analyzing different Smart Grid (SG) scenarios without disrupting the smooth operation of the individual processes, is a major challenge. The field of smart energy grids has been increasing in complexity since there are many stakeholder entities with diverse roles. Electric Vehicles (EVs) can transform the stress on the energy grid into an opportunity to act as a flexible asset. Smart charging through an external control system can have benefits for the energy sector, both in grid management and environmental terms. A suitable model for analyzing and visualizing smart grid use cases in a technology-neutral manner is required. This paper presents a flexible architecture for the potential implementation of electromobility as a distributed storage asset for the grid’s capacity optimization by applying the Use Case and Smart Grid Architecture Model (SGAM) methodologies. The use case scenario of booking a charge session through a mobile application, as part of the TwinERGY Horizon 2020 project, is deployed to structure the SGAM framework layers and investigate the applicability of the SGAM framework in the integration of electromobility as a distributed storage asset into electricity grids with the objective of enhanced flexibility and decarbonization. Full article

(This article belongs to the Special Issue Integration of Renewable Energy and Plug-In Electric Vehicles into Power Networks)

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26 pages, 3052 KiB

Open AccessEditor’s ChoiceArticle

Improving the Efficiency of Renewable Energy Assets by Optimizing the Matching of Supply and Demand Using a Smart Battery Scheduling Algorithm

by Philippe de Bekker, Sho Cremers, Sonam Norbu, David Flynn and Valentin Robu

Energies 2023, 16(5), 2425; https://doi.org/10.3390/en16052425 - 3 Mar 2023

Cited by 2 | Viewed by 3310

Abstract

Given the fundamental role of renewable energy assets in achieving global temperature control targets, new energy management methods are required to efficiently match intermittent renewable generation and demand. Based on analysing various designed cases, this paper explores a number of heuristics for a [...] Read more.

Given the fundamental role of renewable energy assets in achieving global temperature control targets, new energy management methods are required to efficiently match intermittent renewable generation and demand. Based on analysing various designed cases, this paper explores a number of heuristics for a smart battery scheduling algorithm that efficiently matches available power supply and demand. The core of improvement of the proposed smart battery scheduling algorithm is exploiting future knowledge, which can be realized by current state-of-the-art forecasting techniques, to effectively store and trade energy. The performance of the developed heuristic battery scheduling algorithm using forecast data of demands, generation, and energy prices is compared to a heuristic baseline algorithm, where decisions are made solely on the current state of the battery, demand, and generation. The battery scheduling algorithms are tested using real data from two large-scale smart energy trials in the UK, in addition to various types and levels of simulated uncertainty in forecasts. The results show that when using a battery to store generated energy, on average, the newly proposed algorithm outperforms the baseline algorithm, obtaining up to 20–60% more profit for the prosumer from their energy assets, in cases where the battery is optimally sized and high-quality forecasts are available. Crucially, the proposed algorithm generates greater profit than the baseline method even with large uncertainty on the forecast, showing the robustness of the proposed solution. On average, only 2–12% of profit is lost on generation and demand uncertainty compared to perfect forecasts. Furthermore, the performance of the proposed algorithm increases as the uncertainty decreases, showing great promise for the algorithm as the quality of forecasting keeps improving. Full article

(This article belongs to the Topic Energy Saving and Energy Efficiency Technologies)

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16 pages, 1659 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Voltage Control Market Integration: Technical and Regulatory Challenges for the Greek Electricity Market

by Marios-Charilaos Sousounis, Epameinondas (Nondas) Floros, Fotios-Konstantinos Paterakis, Christos Dikaiakos and Ioannis Moraitis

Energies 2023, 16(5), 2306; https://doi.org/10.3390/en16052306 - 27 Feb 2023

Viewed by 1524

Abstract

Stochastic power generation is the new reality in power system management. Voltage Control mechanisms based on physical assets of the power system are deemed inadequate and are not guaranteed to lead the energy transformation in a way that ensures system security as well [...] Read more.

Stochastic power generation is the new reality in power system management. Voltage Control mechanisms based on physical assets of the power system are deemed inadequate and are not guaranteed to lead the energy transformation in a way that ensures system security as well as cost-effective operation. Many countries that recently attained deregulated Balancing Market environments are in need of regulatory provisions and rigorous extension of electricity market mechanisms. On 1 November 2020, the Greek Electricity Market commenced operations conforming to the European Target Model. Apart from the innate difficulties a transformation such as this contains, more challenges occur as Greece is bound by European law to design market-based incentive mechanisms to remunerate Ancillary Services provided to the power system. This paper aims to examine some of the technical and regulatory aspects linked with—future—Transmission System Operator (TSO) and Distribution System Operator (DSO) cooperation in overcoming local transmission system problems concerning Voltage regulation. The interaction between localized Voltage Control Market (VCM) and the Balancing Market, the incorporation and competition of Distributed Energy Resources (DER) and Transmission Energy Resources (TER) within the VCM along with the TSO - DSO procedures and products standardization are the focus points of the present research paper. Full article

(This article belongs to the Special Issue Flexibility Integration and Decarbonisation Pathways)

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13 pages, 484 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Impact of Battery Storage on Power Flow and Economy in an Automated Transactive Energy Market

by Shida Zhang and Petr Musilek

Energies 2023, 16(5), 2251; https://doi.org/10.3390/en16052251 - 26 Feb 2023

Cited by 1 | Viewed by 1477

Abstract

This article explores the use of battery energy storage in a transactive energy approach for a heavily solar-penetrated community. We hypothesize that the efficient market interactions between independently acting, fully automated agents (some equipped with battery energy storage) can result in both bill [...] Read more.

This article explores the use of battery energy storage in a transactive energy approach for a heavily solar-penetrated community. We hypothesize that the efficient market interactions between independently acting, fully automated agents (some equipped with battery energy storage) can result in both bill savings and improvements in power flow, without explicitly optimizing for power flow ahead of time. A test setting of nine typical residential prosumers and one heavily loaded prosumer is used. The heavily loaded prosumer initially experiences multiple undervoltage violations, and a 13.5 kWh battery is installed to alleviate the problem. Two profile-shaping strategies are compared. The first scenario uses greedy control that maximizes self-sufficiency, while the second scenario uses a local market to enable energy trading between participants and a rule-based trading and management agent for control. The results show that the first scenario made minimal improvements to power flow, but the second scenario eliminated all occurrences of under-voltage violations. Furthermore, the total amount of energy from the grid is reduced by 24.3%, and the amount of energy injected into the grid is reduced by 39.2%. This results in lower bills for every participant and a bill reduction of 16.7% for the community as a whole. Full article

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16 pages, 1265 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Role of Fiscal Policy in G20 Countries in the Context of the Environmental Kuznets Curve Hypothesis

by Muhammad Mar’I, Mehdi Seraj and Turgut Tursoy

Energies 2023, 16(5), 2215; https://doi.org/10.3390/en16052215 - 24 Feb 2023

Cited by 6 | Viewed by 2337

Abstract

Fiscal policy is an essential tool that policymakers use for guiding the economy. Thus, the effects of fiscal policy may affect many aspects of our lives, including the impact of carbon dioxide (CO₂) emissions. This article investigates the role of fiscal [...] Read more.

Fiscal policy is an essential tool that policymakers use for guiding the economy. Thus, the effects of fiscal policy may affect many aspects of our lives, including the impact of carbon dioxide (CO₂) emissions. This article investigates the role of fiscal policy, in addition to gross domestic product (GDP), innovation, and financial development, in mitigating CO₂ emissions in the context of the Environmental Kuznets Curve theory in the Group of Twenty (G20) countries from 1995 to 2019. The study implied the autoregressive distributed lag of pooled mean group (ARDL-PMG) approach to analyze the suggested model. The results revealed the validity of the model for the G20 countries, as well as a long-run cointegration between the study variables. The results also showed that fiscal policy is associated positively with CO₂ emissions. Hence, we recommend reconsidering the applied financial policy, redirecting it to support clean energy projects, provide incentives for projects combating environmental degradation, and relying on environmentally friendly energy. Full article

(This article belongs to the Special Issue Economic Analysis and Policies for the Environment, Natural Resources and Energy)

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13 pages, 3115 KiB

Open AccessEditor’s ChoiceArticle

Risk Assessment of Offshore Wind Turbines Suction Bucket Foundation Subject to Multi-Hazard Events

by Duc-Vu Ngo, Young-Jin Kim and Dong-Hyawn Kim

Energies 2023, 16(5), 2184; https://doi.org/10.3390/en16052184 - 24 Feb 2023

Cited by 5 | Viewed by 2870

Abstract

For the offshore wind turbines (OWTs) located in a seismically active region, the occurrence of earthquakes combined with scour is a highly possible multi-hazard event. This study developed an alternative fragility analysis framework to assess the seismic performance of suction bucket-supported OWTs under [...] Read more.

For the offshore wind turbines (OWTs) located in a seismically active region, the occurrence of earthquakes combined with scour is a highly possible multi-hazard event. This study developed an alternative fragility analysis framework to assess the seismic performance of suction bucket-supported OWTs under the action of scour. First, the probabilistic approach was applied to calculate the occurrence probability of scour depth (SD) and earthquake events. Then, the possible combinations of these two events were considered in the analysis model to establish the fragility surface of the suction bucket foundation. Finally, by integrating the product of scour and earthquake hazard, as well as fragility curves, the suction bucket foundation failure probability was obtained. The developed framework provides a reliable approach to risk assessment for OWT-supporting structures in extreme event situations and can be applied to other complex natural hazards. Full article

(This article belongs to the Special Issue Numerical Analysis, Field Testing and Experimental Assessment of Offshore Wind Turbines 2023)

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22 pages, 1101 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Relationship between Energy Consumption and Economic Growth in the Baltic Countries’ Agriculture: A Non-Linear Framework

by Daiva Makutėnienė, Algirdas Justinas Staugaitis, Bernardas Vaznonis and Gunta Grīnberga-Zālīte

Energies 2023, 16(5), 2114; https://doi.org/10.3390/en16052114 - 22 Feb 2023

Cited by 1 | Viewed by 2097

Abstract

The development of a country’s economy is directly related to the use of energy in that country’s economic sectors. Therefore, the energy–environmental Kuznets curve (EEKC) is often used when analysing a country’s potential and challenges in sustainable development, green economy, and green growth. [...] Read more.

The development of a country’s economy is directly related to the use of energy in that country’s economic sectors. Therefore, the energy–environmental Kuznets curve (EEKC) is often used when analysing a country’s potential and challenges in sustainable development, green economy, and green growth. This hypothesis tests whether there is an inverse “U”-shaped relationship between energy use and economic growth and is especially important when analysing developing countries to assess if, at a certain point, energy use begins to drop, resulting in fewer greenhouse gas emissions, environmental degradation, and the consumption of fossil-based fuels. This study aims to examine the relationship between energy consumption and economic growth in the Baltic States from 1995 to 2019, with a focus on the agriculture sector. The study uses the non-linear autoregressive distributed lag (NARDL) model for individual and panel time series. Total energy use, as well as electricity use, is included in the study, whereas gross value added is employed as a measure of economic growth. Research data analysis reveals that energy use in all three Baltic countries stabilises as gross value added increases. However, there is insufficient evidence to show that after a certain point, energy use begins to drop; thus, the hypothesis for the inverse “U”-shaped energy–environmental Kuznets curve (EEKC) is rejected. Research results have important practical implications regarding countries’ policies toward energy, including the use of electricity and sustainable development. Full article

(This article belongs to the Special Issue Energy Consumption in the EU Countries II)

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16 pages, 294 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

AI and Energy Justice

by Merel Noorman, Brenda Espinosa Apráez and Saskia Lavrijssen

Energies 2023, 16(5), 2110; https://doi.org/10.3390/en16052110 - 22 Feb 2023

Cited by 6 | Viewed by 4211

Abstract

Artificial intelligence (AI) techniques are increasingly used to address problems in electricity systems that result from the growing supply of energy from dynamic renewable sources. Researchers have started experimenting with data-driven AI technologies to, amongst other uses, forecast energy usage, optimize cost-efficiency, monitor [...] Read more.

Artificial intelligence (AI) techniques are increasingly used to address problems in electricity systems that result from the growing supply of energy from dynamic renewable sources. Researchers have started experimenting with data-driven AI technologies to, amongst other uses, forecast energy usage, optimize cost-efficiency, monitor system health, and manage network congestion. These technologies are said to, on the one hand, empower consumers, increase transparency in pricing, and help maintain the affordability of electricity in the energy transition, while, on the other hand, they may decrease transparency, infringe on privacy, or lead to discrimination, to name a few concerns. One key concern is how AI will affect energy justice. Energy justice is a concept that has emerged predominantly in social science research to highlight that energy related decisions—in particular, as part of the energy transition—should produce just outcomes. The concept has been around for more than a decade, but research that investigates energy (in)justice in the context of digitalized and data-driven electricity systems is still rather scarce. In particular, there is a lack of scholarship focusing on the challenges and questions that arise from the use of AI technologies in the management of electricity systems. The central question of this paper is, therefore: what may be the implications of the use of AI in smart electricity systems from the perspective of energy justice, and what does this mean for the design and regulation of these technologies? Full article

(This article belongs to the Special Issue Social License for Digital Energy)

21 pages, 4942 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Environmental Impact Assessment of PEM Fuel Cell Combined Heat and Power Generation System for Residential Application Considering Cathode Catalyst Layer Degradation

by Shota Tochigi and Kiyoshi Dowaki

Energies 2023, 16(4), 1985; https://doi.org/10.3390/en16041985 - 16 Feb 2023

Cited by 6 | Viewed by 2527

Abstract

Recently, fuel cell combined heat and power systems (FC-CGSs) for residential applications have received increasing attention. The International Electrotechnical Commission has issued a technical specification (TS 62282-9-101) for environmental impact assessment procedures of FC-CGSs based on the life cycle assessment, which considers global [...] Read more.

Recently, fuel cell combined heat and power systems (FC-CGSs) for residential applications have received increasing attention. The International Electrotechnical Commission has issued a technical specification (TS 62282-9-101) for environmental impact assessment procedures of FC-CGSs based on the life cycle assessment, which considers global warming during the utilization stage and abiotic depletion during the manufacturing stage. In proton exchange membrane fuel cells (PEMFCs), platinum (Pt) used in the catalyst layer is a major contributor to abiotic depletion, and Pt loading affects power generation performance. In the present study, based on TS 62282-9-101, we evaluated the environmental impact of a 700 W scale PEMFC-CGS considering cathode catalyst degradation. Through Pt dissolution and Ostwald ripening modeling, the electrochemical surface area transition of the Pt catalyst was calculated. As a result of the 10-year evaluation, the daily power generation of the PEMFC-CGS decreased by 11% to 26%, and the annual global warming value increased by 5% due to the increased use of grid electricity. In addition, when Pt loading was varied between 0.2 mg/cm² and 0.4 mg/cm², the 10-year global warming values were reduced by 6.5% to 7.8% compared to the case without a FC-CGS. Full article

(This article belongs to the Special Issue Life Cycle Assessment of Energy and Environment)

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18 pages, 1543 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Technoeconomic Feasibility of Bioenergy Production from Wood Sawdust

by Peyman Alizadeh, Lope G. Tabil, Edmund Mupondwa, Xue Li and Duncan Cree

Energies 2023, 16(4), 1914; https://doi.org/10.3390/en16041914 - 15 Feb 2023

Cited by 10 | Viewed by 5466

Abstract

In this study, the technoeconomic feasibility of bioenergy production from sawdust under four different case scenarios is simulated and compared. These scenarios include: (1) heat and electricity generation from raw sawdust; (2) pellet production from sawdust; (3) and (4) integrated biorefinery approach for [...] Read more.

In this study, the technoeconomic feasibility of bioenergy production from sawdust under four different case scenarios is simulated and compared. These scenarios include: (1) heat and electricity generation from raw sawdust; (2) pellet production from sawdust; (3) and (4) integrated biorefinery approach for the simultaneous manufacturing of multiple products (steam-exploded and torrefied pellets) and co-products (furfural, hydroxy methyl furfural (HMF), acetic acid), along with heat and electricity generation. Economic assessments such as cost analysis, payback time (PBT), net present value (NPV) and internal rate of return (IRR) were determined for these scenarios. The results showed that the approach of producing torrefied pellets, furfural, and acetic acid, along with co-generated heat and electricity, in terms of multiproducts and profitability (NPV (at 7%): USD 38.29 M) was preferable over other alternatives. In terms of simplified technology and other economic indices (PBT: 2.49 year, IRR: 51.33%, and return on investment (ROI): 40.1%), the scenario for producing pellets from wood sawdust was more promising than others. If plant capacity was not a limiting factor, the optimal size for the combined heat and power (CHP) plant was between 250–300 kt for the main product. Additionally, untreated and treated pellet plants equipped with CHP had an optimal size of 150–200 kt of wood pellets per year. Full article

(This article belongs to the Topic Energy Economics and Sustainable Development)

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18 pages, 7567 KiB

Open AccessEditor’s ChoiceArticle

Load Evaluation for Tower Design of Large Floating Offshore Wind Turbine System According to Wave Conditions

by Hyeonjeong Ahn, Yoon-Jin Ha and Kyong-Hwan Kim

Energies 2023, 16(4), 1862; https://doi.org/10.3390/en16041862 - 13 Feb 2023

Cited by 4 | Viewed by 4994

Abstract

This study entailed a load evaluation for the tower design of a large floating offshore wind turbine system in accordance with the wave conditions. The target model includes the IEA 15 MW reference wind turbine and a semi-submersible VolturnUS-S reference floating offshore wind [...] Read more.

This study entailed a load evaluation for the tower design of a large floating offshore wind turbine system in accordance with the wave conditions. The target model includes the IEA 15 MW reference wind turbine and a semi-submersible VolturnUS-S reference floating offshore wind turbine platform from the University of Maine. The OpenFAST, which is an aero-hydro-servo-elastic fully coupled analysis tool, was used for load analysis. The DLC1.2 and 1.6 were used as the design load cases, and the environmental conditions suitable for the design load cases were cited in the VolturnUS-S platform report. Load evaluation was performed according to time series and FFT results. The findings of the study are as follows: first, in the correlation analysis, the tower-top deflection had the highest correlation, and this further affects nacelle acceleration. Second, the tower-base pitch moment increased with the significant wave height. However, the wave peak period increased until it matched the tower-top deflection frequency and decreased thereafter. Third, the comparison between the normal and severe sea state conditions revealed that the tower-base pitch moments for the two conditions are almost similar, despite the conditions wherein the wave spectral energy differs by a factor of 3.5. Fourth, the tower shape is changed while adjusting the diameter of the tower, and the tower-top and tower-base pitch moments are reviewed using a redesigned tower. Even if the mass is the same, adjusting the diameter of the tower reduces only the pitch moment. Full article

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19 pages, 1685 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Use of Magnetostrictive Actuators for Wave Energy Conversion with Improvised Structures

by Umesh A. Korde

Energies 2023, 16(4), 1835; https://doi.org/10.3390/en16041835 - 12 Feb 2023

Viewed by 1232

Abstract

This paper presents work on a wave energy device with an on-board power take-off based on a magnetostrictively actuated deformable structure. Such devices potentially could be used in low-cost, short-term expeditionary operations. The paper discusses an analytical model that describes the heave oscillations [...] Read more.

This paper presents work on a wave energy device with an on-board power take-off based on a magnetostrictively actuated deformable structure. Such devices potentially could be used in low-cost, short-term expeditionary operations. The paper discusses an analytical model that describes the heave oscillations of a buoy with two inclined, overhanging beams with magnetostrictive strips affixed to them. This work comprises the first steps toward an analytical model that would enable potential users to obtain quick power estimates at the planning stage. Here, the fully nonlinear magneto-mechanical-electrical constitutive relations are linearized about a desirable operating point, and a coupled dynamic model is derived using a variational formulation that includes buoy heave, flexural oscillations of the two beams, and the voltage response of the magnetostrictive strips. Energy conversion performance in wind-sea-dominated Pierson–Moskowitz spectra is found to be modest. However, present results also indicate that performance could be improved with suitable mechanical modifications. Full article

(This article belongs to the Special Issue Wave Energy: Theory, Methods, and Applications)

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21 pages, 24088 KiB

Open AccessEditor’s ChoiceArticle

Physical Modelling of Tidal Stream Turbine Wake Structures under Yaw Conditions

by Can Zhang, Jisheng Zhang, Athanasios Angeloudis, Yudi Zhou, Stephan C. Kramer and Matthew D. Piggott

Energies 2023, 16(4), 1742; https://doi.org/10.3390/en16041742 - 9 Feb 2023

Cited by 4 | Viewed by 1875

Abstract

Tidal stream turbines may operate under yawed conditions due to variability in ocean current directions. Insight into the wake structure of yawed turbines can be essential to ensure efficient tidal stream energy extraction, especially for turbine arrays where wake interactions emerge. We studied [...] Read more.

Tidal stream turbines may operate under yawed conditions due to variability in ocean current directions. Insight into the wake structure of yawed turbines can be essential to ensure efficient tidal stream energy extraction, especially for turbine arrays where wake interactions emerge. We studied experimentally the effects of turbines operating under varying yaw conditions. Two scenarios, including a single turbine and a set of two turbines in alignment, were configured and compared. The turbine thrust force results confirmed that an increasing yaw angle results in a decrease in the turbine streamwise force and an increase in the turbine spanwise force. The velocity distribution from the single turbine scenario showed that the wake deflection and velocity deficit recovery rate increased at a rate proportional to the yaw angle. The two-turbine scenario results indicated that the deployment of an upstream non-yawed turbine significantly limited the downstream wake steering (i.e., the wake area behind the downstream turbine). Interestingly, a yawed downstream turbine was seen to influence the steering of both the upstream and the downstream wakes. These systematically derived data could be regarded as useful references for the numerical modelling and optimisation of large arrays. Full article

(This article belongs to the Special Issue Tidal Energy: Latest Advances and Prospects of Tidal Current Turbine)

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16 pages, 6027 KiB

Open AccessEditor’s ChoiceArticle

Empirical Study of Stability and Fairness of Schemes for Benefit Distribution in Local Energy Communities

by Steffen Limmer

Energies 2023, 16(4), 1756; https://doi.org/10.3390/en16041756 - 9 Feb 2023

Cited by 3 | Viewed by 1712

Abstract

The concept of local energy communities is receiving increasing attention. However, the question of how to distribute the benefit of a community among its members is still open. It is commonly desired that the benefit distribution is fair and stable. While benefit distribution [...] Read more.

The concept of local energy communities is receiving increasing attention. However, the question of how to distribute the benefit of a community among its members is still open. It is commonly desired that the benefit distribution is fair and stable. While benefit distribution schemes such as the nucleolus, Shapley value and Shapley-core are known to perform well in terms of fairness and stability, studies have shown that none of them can guarantee full fairness and stability at the same time. However, the existing studies neglect the temporal component. Hence, in order to gain more insights into the stability and fairness of the three aforementioned distributions in practice, we investigate their performance over time in simulation experiments on real-world data from Australian households. In about 90% of the cases, the Shapley value yielded a reasonably stable distribution, while the nucleolus yielded a reasonably fair distribution in about 75% of the cases. Furthermore, the experiments show an impact of the community size on the stability and fairness of the investigated distributions. One can conclude that for small communities, the Shapley value is the best choice, but that the nucleolus and Shapley–core become more and more attractive with increasing size of the community. Full article

(This article belongs to the Special Issue Energy Transition: Decentralization, Electric Vehicles, and Local Energy Markets)

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12 pages, 1528 KiB

Open AccessEditor’s ChoiceArticle

A Robust Model for Portfolio Management of Microgrid Operator in the Balancing Market

by Meysam Khojasteh, Pedro Faria, Fernando Lezama and Zita Vale

Energies 2023, 16(4), 1700; https://doi.org/10.3390/en16041700 - 8 Feb 2023

Cited by 1 | Viewed by 1409

Abstract

The stochastic nature of renewable energy resources and consumption has the potential to threaten the balance between generation and consumption as well as to cause instability in power systems. The microgrid operators (MGOs) are financially responsible for compensating for the imbalance of power [...] Read more.

The stochastic nature of renewable energy resources and consumption has the potential to threaten the balance between generation and consumption as well as to cause instability in power systems. The microgrid operators (MGOs) are financially responsible for compensating for the imbalance of power within their portfolio. The imbalance of power can be supplied by rescheduling flexible resources or participating in the balancing market. This paper presents a robust optimization (RO)-based model to maintain the balance of a portfolio according to uncertainties in renewable power generation and consumption. Furthermore, load reduction (LR) and battery energy storage (BES) are considered flexible resources of the MGO on the consumption side. The model is formulated based on the minimax decision rule that determines the minimum cost of balancing based on the worst-case realizations of uncertain parameters. Through the strong duality theory and big-M theory, the proposed minimax model is transformed into a single-level linear maximization problem. The proposed model is tested on a six-node microgrid test system. The main contributions of the proposed model are presenting a robust model for portfolio management of MGO and using BES and LR to improve the flexibility of microgrid. Simulation results demonstrate that using LR and BES could decrease the balancing cost. However, the optimal portfolio management to compensate for the imbalance of power is highly dependent on the risk preferences of MGO. Full article

(This article belongs to the Special Issue Energy Transition: Decentralization, Electric Vehicles, and Local Energy Markets)

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20 pages, 6348 KiB

Open AccessEditor’s ChoiceArticle

Stability Impacts of an Alternate Voltage Controller (AVC) on Wind Turbines with Different Grid Strengths

by Dimitrios Dimitropoulos, Xiongfei Wang and Frede Blaabjerg

Energies 2023, 16(3), 1440; https://doi.org/10.3390/en16031440 - 1 Feb 2023

Cited by 2 | Viewed by 1961

Abstract

This paper studies the stability impact of the alternate voltage controller’s (AVC) low-pass filter (LPF) in a wind turbine’s grid-connected voltage source converter (VSC). A small-signal model of the grid-connected converter is designed with a grid-following synchronization control. More specifically, the non-linear state-space [...] Read more.

This paper studies the stability impact of the alternate voltage controller’s (AVC) low-pass filter (LPF) in a wind turbine’s grid-connected voltage source converter (VSC). A small-signal model of the grid-connected converter is designed with a grid-following synchronization control. More specifically, the non-linear state-space model of the grid-connected converter was developed, including the dynamics of both the inner and outer control loops of the converter, the dynamics of the elements of the electrical system, as well as the digital time delay. An eigenvalue-based stability analysis gives insight into the stability impacts of the outer-loop controllers. It is proven that the cutoff frequency of the AVC’s LPF affects the phase-locked loop (PLL) and AVC bandwidths of instability, as well as the corresponding critical oscillation frequencies. This phenomenon is observed in both weak and strong grids. Consequently, the small-signal stability regions of the PLL and AVC bandwidth can be identified for the range of the AVC’s LPF cutoff frequency under study. The stability regions of the PLL and AVC, which are obtained from the small-signal model, as well as the determined critical oscillation frequencies, are validated through time domain simulations and fast-Fourier transformation (FFT) analysis. Full article

(This article belongs to the Special Issue Wind Turbine 2023)

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37 pages, 7085 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

SWOT Analysis of Non-Technical and Technical Measures towards “(Nearly) Zero-Emission Stove Technologies”

by Gabriel Reichert and Christoph Schmidl

Energies 2023, 16(3), 1388; https://doi.org/10.3390/en16031388 - 30 Jan 2023

Cited by 2 | Viewed by 2333

Abstract

Firewood stoves are widespread and popular for renewable heat supply in Europe. Several new technological measures have been developed recently that aim at improving the appliance performance in terms of emissions and efficiency. In order to support the trend towards “(nearly) zero-emissions technologies”, [...] Read more.

Firewood stoves are widespread and popular for renewable heat supply in Europe. Several new technological measures have been developed recently that aim at improving the appliance performance in terms of emissions and efficiency. In order to support the trend towards “(nearly) zero-emissions technologies”, the objective of this study was to provide a profound overview of the most relevant technical primary and secondary measures for emission reduction and to analyze their functionality, the relevant framework conditions for their application and their costs. Since user behavior is essential for emission and efficiency performance, the state of knowledge about user behavior is summarized and the latest measures for its optimization are evaluated as non-technical primary measures. Primary and secondary measures were analyzed separately, but also potentially promising combinations of primary and secondary optimization were evaluated using SWOT analysis. The results showed that complementary application of primary and secondary measures will be necessary in order to achieve “(nearly) zero-emission technologies”. The paper is useful for manufacturers and provides them with guidance and recommendations for future developments. They can specifically select appropriate measures for their products and applications not only based on technical aspects, but also with a strong focus on user behavior and user comfort. Full article

(This article belongs to the Special Issue Biomass Conversion Technologies II)

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20 pages, 3479 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Economic and Energetic Assessment and Comparison of Solar Heating and Cooling Systems

by Boris Delač, Branimir Pavković and Vladimir Glažar

Energies 2023, 16(3), 1241; https://doi.org/10.3390/en16031241 - 23 Jan 2023

Cited by 1 | Viewed by 1596

Abstract

Solar heating and cooling (SHC) systems are currently attracting attention, especially in times of increasing energy prices and supply crises. In times of lower energy prices, absorption SHC systems were not competitive to compression cooling supported by photovoltaic (PV) modules due to the [...] Read more.

Solar heating and cooling (SHC) systems are currently attracting attention, especially in times of increasing energy prices and supply crises. In times of lower energy prices, absorption SHC systems were not competitive to compression cooling supported by photovoltaic (PV) modules due to the high investment costs and total energy efficiency. This paper aims to discuss the current changes in energy supply and energy prices in terms of the feasibility of the application of a small absorption SHC system in a mild Mediterranean climate. The existing hospital complex restaurant SHC system with evacuated tube solar collectors and a small single-stage absorption chiller was used as a reference system for extended analysis. Dynamic simulation models based on solar thermal collectors, PV modules, absorption chillers and air-to-water heat pumps were developed for reliable research and system comparison. The results showed that primary energy consumption in SHC systems designed to cover base energy load strongly depends on the additional energy source, e.g., boiler or heat pump. Absorption SHC systems can be price competitive to air-to-water heat pump (AWHP) systems with PV collectors only in the case of reduced investment costs and increased electricity price. To reach acceptable economic viability of the absorption SHC system, investment price should be at least equal to or lower than a comparable AWHP system. Full article

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29 pages, 15097 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Experimental and Theoretical Investigation of Single-Slope Passive Solar Still with Phase-Change Materials

by Ewelina Radomska, Łukasz Mika, Karol Sztekler, Wojciech Kalawa, Łukasz Lis, Kinga Pielichowska, Magdalena Szumera and Paweł Rutkowski

Energies 2023, 16(3), 1188; https://doi.org/10.3390/en16031188 - 21 Jan 2023

Cited by 4 | Viewed by 1631

Abstract

Many attempts are made worldwide to create cheap, efficient, and eco-friendly water desalination systems. Passive solar stills (SS) are considered to be such. This paper presents the results of the experimental and theoretical investigation of the effects of using phase-change materials (PCM) on [...] Read more.

Many attempts are made worldwide to create cheap, efficient, and eco-friendly water desalination systems. Passive solar stills (SS) are considered to be such. This paper presents the results of the experimental and theoretical investigation of the effects of using phase-change materials (PCM) on the performance of SS. The experiments were conducted for two paraffin waxes, as PCM and 1.0, 2.5, and 5.0 kg of PCM were used. The results of the experimental studies were used to validate a mathematical model, which was based on the energy balance ordinary differential equations. The equations were solved numerically since the approximate solutions obtained numerically are sufficient and relatively simple as compared to the exact analytical solutions. A theoretical analysis was then carried out and a novel and detailed dependence on the water evaporation rate as a function of water temperature and the difference between water and cover temperature was determined. It was also found that the productivity of the SS with PCM strongly depends on the operating conditions. For uniform initial temperatures of the SS, its productivity decreases with an increasing PCM-to-water mass ratio, and the maximum decrease is 10.8%. If the SS is not thermally insulated, the PCM can take the role of a thermal insulator and increase productivity by 1.1%, but there is an optimal PCM-to-water mass ratio. The greatest increase in productivity, by up to 47.1%, can be obtained when the PCM is heated outside the SS and inserted into the SS when the water temperature starts to decrease. In this case, the productivity increases with the increasing PCM-to-water mass ratio. These outcomes fill a knowledge gap caused by a lack of justification for why in some cases, the application of PCM fails to improve the productivity of SS. Full article

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

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19 pages, 3418 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of Increasing Renewable Power Penetration on the Long-Term Iberian Electricity Market Prices

by Pedro Leal, Rui Castro and Fernando Lopes

Energies 2023, 16(3), 1054; https://doi.org/10.3390/en16031054 - 18 Jan 2023

Cited by 2 | Viewed by 1983

Abstract

In recent years, there has been a significant increase in investment in renewable energy sources, leading to the decarbonization of the electricity sector. Accordingly, a key concern is the influence of this process on future electricity market prices, which are expected to decrease [...] Read more.

In recent years, there has been a significant increase in investment in renewable energy sources, leading to the decarbonization of the electricity sector. Accordingly, a key concern is the influence of this process on future electricity market prices, which are expected to decrease with the increasing generation of renewable power. This is important for both current and future investors, as it can affect profitability. To address these concerns, a long-term analysis is proposed here to examine the influence of the future electricity mix on Iberian electricity prices in 2030. In this study, we employed artificial intelligence forecasting models that incorporated the main electricity price-driven components of MIBEL, providing accurate predictions for the real operation of the market. These can be extrapolated into the future to predict electricity prices in a scenario with high renewable power penetration. The results, obtained considering a framework featuring an increase in the penetration of renewables into MIBEL of up to 80% in 2030, showed that electricity prices are expected to decrease by around 50% in 2030 when compared to 2019, and there will be a new pattern of electricity prices throughout the year due to the uneven distribution of renewable electricity. The study’s findings are relevant for ongoing research on the unique challenges of energy markets with high levels of renewable generation. Full article

(This article belongs to the Special Issue Coherent Security Planning for Power Systems)

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14 pages, 1704 KiB

Open AccessEditor’s ChoiceArticle

Life Cycle Assessment of Greenhouse Gas (GHG) and NOx Emissions of Power-to-H₂-to-Power Technology Integrated with Hydrogen-Fueled Gas Turbine

by Guohui Song, Qi Zhao, Baohua Shao, Hao Zhao, Hongyan Wang and Wenyi Tan

Energies 2023, 16(2), 977; https://doi.org/10.3390/en16020977 - 15 Jan 2023

Cited by 4 | Viewed by 3037

Abstract

Hydrogen is expected to play an important role in renewable power storage and the decarbonization of the power sector. In order to clarify the environmental impacts of power regenerated through hydrogen-fueled gas turbines, this work details a life cycle model of the greenhouse [...] Read more.

Hydrogen is expected to play an important role in renewable power storage and the decarbonization of the power sector. In order to clarify the environmental impacts of power regenerated through hydrogen-fueled gas turbines, this work details a life cycle model of the greenhouse gas (GHG) and NOx emissions of the power regenerated by power-to-H₂-to-power (PHP) technology integrated with a combined cycle gas turbine (CCGT). This work evaluates the influences of several variables on the life cycle of GHG and NOx emissions, including renewable power sources, hydrogen production efficiency, net CCGT efficiency, equivalent operating hours (EOH), and plant scale. The results show that renewable power sources, net CCGT efficiency, and hydrogen production efficiency are the dominant variables, while EOH and plant scale are the minor factors. The results point out the direction for performance improvement in the future. This work also quantifies the life cycle of GHG and NOx emissions of power regenerated under current and future scenarios. For hydro, photovoltaic (PV) and wind power, the life cycle of the GHG emissions of regenerated power varies from 8.8 to 366.1 g_CO2e/kWh and that of NOx emissions varies from 0.06 to 2.29 g/kWh. The power regenerated from hydro and wind power always has significant advantages over coal and gas power in terms of GHG and NOx emissions. The power regenerated from PV power has a small advantage over gas power in terms of GHG emissions, but does not have advantages regarding NOx emissions. Preference should be given to storing hydro and wind power, followed by PV power. For biomass power with or without CO₂ capture and storage (CCS), the life cycle of the GHG emissions of regenerated power ranges from 555.2 to 653.5 and from −2385.0 to −1814.4, respectively, in g_CO2e/kWh; meanwhile, the life cycle of NOx emissions ranges from 1.61 to 4.65 g/kWh, being greater than that of coal and gas power. Biomass power with CCS is the only power resource that can achieve a negative life cycle for GHG emissions. This work reveals that hydrogen-fueled gas turbines are an important, environmentally friendly technology. It also helps in decision making for grid operation and management. Full article

(This article belongs to the Special Issue Progress in Alternative Fuels for Future Electrical Power System)

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17 pages, 6612 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Design of a Repetitive Control for a Three-Phase Grid-Tied Converter under Distorted Grid Voltage Conditions

by Andrzej Straś, Bartłomiej Ufnalski and Arkadiusz Kaszewski

Energies 2023, 16(2), 754; https://doi.org/10.3390/en16020754 - 9 Jan 2023

Cited by 1 | Viewed by 1771

Abstract

The paper presents a design of repetitive control (RC) in the current control system of a three-phase grid-tied converter. The goal of the control system is to provide sinusoidal input filter currents under the conditions of distorted and asymmetrical grid voltage. A novel [...] Read more.

The paper presents a design of repetitive control (RC) in the current control system of a three-phase grid-tied converter. The goal of the control system is to provide sinusoidal input filter currents under the conditions of distorted and asymmetrical grid voltage. A novel design of the RC is presented, in which the repetitive part is not excited by sharp and non-periodic changes of the reference signal, but it enables high-quality performance under periodic disturbance conditions. In the proposed system. RC cooperates with a discrete state feedback controller. An innovative approach to tuning is proposed in which parameters of the repetitive, as well as the state feedback controller, are selected as a result of the optimization process with the use of a particle swarm algorithm. The proposed control system is verified experimentally on a laboratory test bench. The achieved results confirm the high-quality system performance. Full article

(This article belongs to the Special Issue Dynamic Modelling and Control in Multilevel Converters)

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11 pages, 3393 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Denitrification in Microbial Fuel Cells Using Granular Activated Carbon as an Effective Biocathode

by Anup Gurung, Bhim Sen Thapa, Seong-Yun Ko, Ebenezer Ashun, Umair Ali Toor and Sang-Eun Oh

Energies 2023, 16(2), 709; https://doi.org/10.3390/en16020709 - 7 Jan 2023

Cited by 7 | Viewed by 2180

Abstract

Nitrate (NO₃⁻-N) and nitrites (NO₂⁻-N) are common pollutants in various water bodies causing serious threats not only to aquatic, but also to animals and human beings. In this study, we developed a strategy for efficiently reducing nitrates [...] Read more.

Nitrate (NO₃⁻-N) and nitrites (NO₂⁻-N) are common pollutants in various water bodies causing serious threats not only to aquatic, but also to animals and human beings. In this study, we developed a strategy for efficiently reducing nitrates in microbial fuel cells (MFCs) powered by a granular activated carbon (GAC)-biocathode. GAC was developed by acclimatizing and enriching denitrifying bacteria under a redox potential (0.3 V) generated from MFCs. Thus, using the formed GAC-biocathode we continued to study their effect on denitrification with different cathode materials and circulation speeds in MFCs. The GAC-biocathode with its excellent capacitive property can actively reduce nitrate for over thirty days irrespective of the cathode material used. The stirring speed of GAC in the cathode showed a steady growth in potential generation from 0.25 V to 0.33 V. A rapid lag phase was observed when a new carbon cathode was used with enriched GAC. While a slow lag phase was seen when a stainless-steel cathode was replaced. These observations showed that effective storage and supply of electrons to the GAC plays a crucial role in the reduction process in MFCs. Electrochemical analysis of the GAC properties studied using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and zeta potential showed distinct properties with different abiotic and biocathode conditions. We found that the enrichment of electrotrophic bacteria on GAC facilitates the direct electron transfer in the cathode chamber for reducing NO₃⁻-N in MFCs as observed by scanning electron microscopy. Full article

(This article belongs to the Special Issue Distributed Storage in Power System: Technologies, Control and Management II)

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20 pages, 3828 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Simulating the Diffusion of Residential Rooftop Photovoltaic, Battery Storage Systems and Electric Cars in Italy. An Exploratory Study Combining a Discrete Choice and Agent-Based Modelling Approach

by Romeo Danielis, Mariangela Scorrano, Alessandro Massi Pavan and Nicola Blasuttigh

Energies 2023, 16(1), 557; https://doi.org/10.3390/en16010557 - 3 Jan 2023

Cited by 9 | Viewed by 2843

Abstract

Rooftop solar photovoltaic (PV) systems could significantly contribute to renewable energy production and reduce domestic energy costs. In Italy, as in other countries, the current incentives generate a modest annual increase after the generous fiscal incentives that kick-started the PV market in the [...] Read more.

Rooftop solar photovoltaic (PV) systems could significantly contribute to renewable energy production and reduce domestic energy costs. In Italy, as in other countries, the current incentives generate a modest annual increase after the generous fiscal incentives that kick-started the PV market in the 2008–2013 period. Several factors are, however, at play that can speed up the installation process, such as the improvements in PV technology at declining prices, the increased availability of battery-storage (BS) systems, the growing use of electric appliances, the uptake of electric cars, and the increased environmental awareness. We integrate two research methodologies, discrete choice modeling and agent-based modeling, to understand how these factors will influence households’ decisions regarding PV and BS installations and how agents interact in their socioeconomic environment. We predict that in Italy, given the preference structure of homeowners, the continuing decline in costs, and the social interaction, 40–45% of homeowners will have PV or PV and BS installed by 2030, thanks to the existing investment tax credit policy. Full article

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27 pages, 5531 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Declining Discount Rates for Energy Policy Investments in CEE EU Member Countries

by Rafał Buła and Monika Foltyn-Zarychta

Energies 2023, 16(1), 321; https://doi.org/10.3390/en16010321 - 28 Dec 2022

Cited by 4 | Viewed by 2276

Abstract

Energy policy investments are usually evaluated using a cost-benefit analysis (CBA), which requires an estimation of the social discount rate (SDR). The choice of SDR can be crucial for the outcome of the appraisal, as energy-related investments generate long-term impacts affecting climate change. [...] Read more.

Energy policy investments are usually evaluated using a cost-benefit analysis (CBA), which requires an estimation of the social discount rate (SDR). The choice of SDR can be crucial for the outcome of the appraisal, as energy-related investments generate long-term impacts affecting climate change. Once discounted, these impacts are highly sensitive to slight changes in the value of the SDR. Some countries (the UK and France) switched from a constant SDR to the declining rate scheme—a solution that limits the impact sensitivity. To our knowledge, none of the CEE countries apply DDR in CBA. While a constant SDR is a relatively well-established approach, declining SDRs are estimated to be used much less frequently, particularly for CEE EU member countries and energy policies. The rationale for the decline can rest on uncertainty over future discount rates, as shown by the approach developed by Weitzman and Gollier, which extends the classical Ramsey model. We applied this approach in our paper, as the Ramsey formula is the prevailing formula for EU countries’ SDR estimates. We estimated a flat SDR via the Ramsey formula with Gollier’s “precautionary term”, and next, we calculated Weitzman’s certainty equivalent rates for the 500-year horizon. Ramsey’s SDRs, obtained using consumption growth rates dating back to 1996, varied between 6.77% for Lithuania and 2.95% for Czechia and declined by 0.15% on average (Gollier’s term). Declining SDRs for the longest horizon dropped to approx. 0.5% (from 0.35% for Bulgaria to 0.67% for Poland), and the descent is deeper and faster when forward SDRs (following the UK Green Book approach) were considered (0.01% to 0.04%). The results are important for long-term policies regarding energy and climate change in CEE EU member countries, but they are still dependent on fossil fuels and experience an investment gap to fulfil EU climate goals. Full article

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

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20 pages, 2033 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Energy and Environmental Assessment of Cogeneration in Ceramic Tiles Industry

by Maria Alessandra Ancona, Lisa Branchini, Saverio Ottaviano, Maria Chiara Bignozzi, Benedetta Ferrari, Barbara Mazzanti, Marcello Salvio, Claudia Toro, Fabrizio Martini and Miriam Benedetti

Energies 2023, 16(1), 182; https://doi.org/10.3390/en16010182 - 24 Dec 2022

Cited by 5 | Viewed by 2348

Abstract

Ceramic tile manufacturing is a highly energy-intensive process. Concerns about carbon emissions and energy costs make energy management crucial for this sector, which holds a leading role in Italian industry. The paper discusses the energetic and environmental performance of cogeneration (CHP) in the [...] Read more.

Ceramic tile manufacturing is a highly energy-intensive process. Concerns about carbon emissions and energy costs make energy management crucial for this sector, which holds a leading role in Italian industry. The paper discusses the energetic and environmental performance of cogeneration (CHP) in the ceramic industry, where prime mover exhaust heat is supplied to a spray-dryer system, contributing to the satisfaction of the thermal demand and decreasing natural gas consumption. A thermodynamic model of a dryer unit, validated against real data, has been set-up to provide a detailed representation of the thermal fluxes involved in the process. Then, the thermal integration with two types of CHP prime movers of similar electric size (4 MW) is investigated. Energetic results show that the gas turbine can contribute up to 81% of dryer thermal consumption, whilst internal combustion engine contribution is limited to 26%. A methodology was ad-hoc defined for the environmental assessment of CHP, accounting for global (CO₂) and local (CO and NO_X) emissions. Results confirm that CHP units guarantee reduction of CO₂ and NO_X compared to separate generation, with maximum values equal to 81 g/kWh_th and 173 mg/kWh_th, respectively; CO emission is decreased only in the case of gas turbine operation, with savings equal to 185 mg/kWh_th. Full article

(This article belongs to the Special Issue High-Performance Cogeneration, Waste Heat Recovery and Environmental Protection Strategies)

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15 pages, 2634 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Design and Evaluation of a High Temperature Phase Change Material Carnot Battery

by Rhys Jacob and Ming Liu

Energies 2023, 16(1), 189; https://doi.org/10.3390/en16010189 - 24 Dec 2022

Cited by 3 | Viewed by 2403

Abstract

In the current study, a high temperature thermal storage system with a hybrid of phase change material and graphite as the storage materials is designed and evaluated as to its applicability for use as a utility-scale Carnot battery. The design includes an externally [...] Read more.

In the current study, a high temperature thermal storage system with a hybrid of phase change material and graphite as the storage materials is designed and evaluated as to its applicability for use as a utility-scale Carnot battery. The design includes an externally heated liquid sodium tank, which is used as the heat transfer fluid. This is used to charge and discharge the storage system consisting of a graphite storage medium sandwiched by two phase change materials. Finally, electrical generation is by way of a supercritical carbon dioxide Brayton cycle operated at 700 °C. Detailed modelling of these designs was conducted by way of a previously validated numerical model to predict performance metrics. Using the aforementioned designs, a preliminary cost estimate was undertaken to better determine applicability. From these results, it was found that while the graphite system was the most effective at storing energy, it was also the highest cost due to the high cost of graphite. In total, 18 storage tanks containing nearly 17,400 tons of storage material were required to store the 1200 MWh_t required to run the sCO₂ power block for 10 h. Under the study conditions, the cost of a PCM-based Carnot battery was estimated to be $476/kWh_e, comparable to other storage technologies. Furthermore, it was found that if the cost of the graphite and/or steel could be reduced, the cost of the system could be reduced to $321/kWh_e. Full article

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

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33 pages, 1217 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Renewable Energy-Based Energy-Efficient Off-Grid Base Stations for Heterogeneous Network

by Khondoker Ziaul Islam, Md. Sanwar Hossain, B. M. Ruhul Amin, G. M. Shafiullah and Ferdous Sohel

Energies 2023, 16(1), 169; https://doi.org/10.3390/en16010169 - 23 Dec 2022

Cited by 3 | Viewed by 2507

Abstract

The heterogeneous network (HetNet) is a specified cellular platform to tackle the rapidly growing anticipated data traffic. From a communications perspective, data loads can be mapped to energy loads that are generally placed on the operator networks. Meanwhile, renewable energy-aided networks offer to [...] Read more.

The heterogeneous network (HetNet) is a specified cellular platform to tackle the rapidly growing anticipated data traffic. From a communications perspective, data loads can be mapped to energy loads that are generally placed on the operator networks. Meanwhile, renewable energy-aided networks offer to curtailed fossil fuel consumption, so to reduce the environmental pollution. This paper proposes a renewable energy based power supply architecture for the off-grid HetNet using a novel energy sharing model. Solar photovoltaics (PV) along with sufficient energy storage devices are used for each macro, micro, pico, or femto base station (BS). Additionally, a biomass generator (BG) is used for macro and micro BSs. The collocated macro and micro BSs are connected through end-to-end resistive lines. A novel-weighted proportional-fair resource-scheduling algorithm with sleep mechanisms is proposed for non-real time (NRT) applications by trading-off the power consumption and communication delays. Furthermore, the proposed algorithm with an extended discontinuous reception (eDRX) and power saving mode (PSM) for narrowband internet of things (IoT) applications extends the battery lifetime for IoT devices. HOMER optimization software is used to perform optimal system architecture, economic, and carbon footprint analyses while the Monte-Carlo simulation tool is used for evaluating the throughput and energy efficiency performances. The proposed algorithms are validated through the practical data of the rural areas of Bangladesh from which it is evident that the proposed power supply architecture is energy-efficient, cost-effective, reliable, and eco-friendly. Full article

(This article belongs to the Special Issue Value Sharing within Renewable Energy Communities)

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17 pages, 2072 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Agnostic Battery Management System Capacity Estimation for Electric Vehicles

by Lisa Calearo, Charalampos Ziras, Andreas Thingvad and Mattia Marinelli

Energies 2022, 15(24), 9656; https://doi.org/10.3390/en15249656 - 19 Dec 2022

Cited by 7 | Viewed by 3228

Abstract

Battery degradation is a main concern for electric vehicle (EV) users, and a reliable capacity estimation is of major importance. Every EV battery management system (BMS) provides a variety of information, including measured current and voltage, and estimated capacity of the battery. However, [...] Read more.

Battery degradation is a main concern for electric vehicle (EV) users, and a reliable capacity estimation is of major importance. Every EV battery management system (BMS) provides a variety of information, including measured current and voltage, and estimated capacity of the battery. However, these estimations are not transparent and are manufacturer-specific, although measurement accuracy is unknown. This article uses extensive measurements from six diverse EVs to compare and assess capacity estimation with three different methods: (1) reading capacity estimation from the BMS through the central area network (CAN)-bus, (2) using an empirical capacity estimation (ECE) method with external current measurements, and (3) using the same method with measurements coming from the BMS. We show that the use of BMS current measurements provides consistent capacity estimation (a difference of approximately 1%) and can circumvent the need for costly experimental equipment and DC chargers. This data can simplify the ECE method only by using an on-board diagnostics port (OBDII) reader and an AC charger, as the car measures the current directly at the battery terminals. Full article

(This article belongs to the Special Issue Smart Electric Vehicle Charging Approaches for Demand Response)

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24 pages, 5778 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Solar Energy Powered Decentralized Smart-Grid for Sustainable Energy Supply in Low-Income Countries: Analysis Considering Climate Change Influences in Togo

by Kokou Amega, Yendoubé Laré, Ramchandra Bhandari, Yacouba Moumouni, Aklesso Y. G. Egbendewe, Windmanagda Sawadogo and Saidou Madougou

Energies 2022, 15(24), 9532; https://doi.org/10.3390/en15249532 - 15 Dec 2022

Cited by 2 | Viewed by 2044

Abstract

A smart and decentralized electrical system, powered by grid-connected renewable energy (RE) with a reliable storage system, has the potential to change the future socio-economic dynamics. Climate change may, however, affect the potential of RE and its related technologies. This study investigated the [...] Read more.

A smart and decentralized electrical system, powered by grid-connected renewable energy (RE) with a reliable storage system, has the potential to change the future socio-economic dynamics. Climate change may, however, affect the potential of RE and its related technologies. This study investigated the impact of climate change on photovoltaic cells’ temperature response and energy potential under two CO₂ emission scenarios, RCP2.6 and 8.5, for the near future (2024–2040) and mid-century (2041–2065) in Togo. An integrated Regional Climate Model version 4 (RegCM4) from the CORDEX-CORE initiative datasets has been used as input. The latter platform recorded various weather variables, such as solar irradiance, air temperature, wind speed and direction, and relative humidity. Results showed that PV cells’ temperature would likely rise over all five regions in the country and may trigger a decline in the PV potential under RCP2.6 and 8.5. However, the magnitude of the induced change, caused by the changing climate, depended on two major factors: (1) the PV technology and (2) geographical position. Results also revealed that these dissimilarities were more pronounced under RCP8.5 with the amorphous technology. It was further found that, nationally, the average cell temperature would have risen by 1 °C and 1.82 °C under RCP2.6 and 8.5, in that order, during the 2024–2065 period for a-Si technology. Finally, the PV potential would likely decrease, on average, by 0.23% for RCP2.6 and 0.4% for RCP8.5 for a-Si technology. Full article

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

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17 pages, 2233 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Coordinated Control of Electric Vehicles and PV Resources in an Unbalanced Power Distribution System

by Abdulrahman Almazroui and Salman Mohagheghi

Energies 2022, 15(24), 9324; https://doi.org/10.3390/en15249324 - 9 Dec 2022

Cited by 1 | Viewed by 1545

Abstract

Improving air quality, reducing greenhouse gas emissions, and achieving independence from fossil fuels have led most countries towards deploying solar photovoltaics (PV) in the power distribution grid and electrifying the transportation fleet. Internal combustion engine (ICE) vehicles are, in particular, one of the [...] Read more.

Improving air quality, reducing greenhouse gas emissions, and achieving independence from fossil fuels have led most countries towards deploying solar photovoltaics (PV) in the power distribution grid and electrifying the transportation fleet. Internal combustion engine (ICE) vehicles are, in particular, one of the main culprits of injecting greenhouse gas emissions into the atmosphere, making electric vehicles (EVs) an important tool in combating climate change. Despite their considerable environmental and economic benefits, the integration of PVs and EVs can introduce unique operational challenges for the power distribution grid. If not coordinated, high penetration of PVs and EVs can result in variety of power quality issues, such as instances of overvoltage and undervoltage, frequency fluctuations, and/or increased losses. This paper proposes a mixed-integer multi-objective nonlinear optimization model for optimal energy dispatch in a power distribution grid with high penetration of PV and EV resources. The model proposed here is an extension of the traditional voltage and var optimization (VVO) into a comprehensive and coordinated control of voltage, active power, and reactive power. A modified version of the IEEE 123-bus test distribution system is used to demonstrate the effectiveness of the proposed solution. Full article

(This article belongs to the Special Issue Power System Operation, Control and Stability)

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