CO₂ Capture and Enhanced Hydrogen Production Enabled by Low-Temperature Separation of PSA Tail Gas: A Detailed Exergy Analysis
Development of a Homogenized Finite Element Model for Pouch Lithium-Ion Battery Cells Considering Porosity and Pressure Sensitivity
Electricity Cost Savings in Energy-Intensive Companies: Optimization Framework and Case Study
A Composite Index for Tracking the Evolution towards Energy Transition at Urban Scale: The Turin Case Study
Predictive Energy Management of a Building-Integrated Microgrid: A Case Study

Journal Description

Energies

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

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Ei Compendex, RePEc, Inspec, CAPlus / SciFinder, and other databases.
Journal Rank: CiteScore - Q1 (Engineering (miscellaneous))
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 16.1 days after submission; acceptance to publication is undertaken in 3.3 days (median values for papers published in this journal in the second half of 2023).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Sections: published in 41 topical sections.
Testimonials: See what our editors and authors say about Energies.
Companion journals for Energies include: Fuels, Gases, Nanoenergy Advances and Solar.

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

Imprint Information Journal Flyer Open Access ISSN: 1996-1073

Latest Articles

16 pages, 3222 KiB

Open AccessArticle

Spray Characterization of Direct Hydrogen Injection as a Green Fuel with Lower Emissions

by Raul Payri, Ricardo Novella, Khodor I. Nasser and Oscar Bori-Fabra

Energies 2024, 17(10), 2405; https://doi.org/10.3390/en17102405 (registering DOI) - 16 May 2024

Abstract

A viable green energy source for heavy industries and transportation is hydrogen. The internal combustion engine (ICE), when powered by hydrogen, offers an economical and adaptable way to quickly decarbonize the transportation industry. In general, two techniques are used to inject hydrogen into the ICE combustion chamber: port injection and direct injection. The present work examined direct injection technology, highlighting the need to understand and manage hydrogen mixing within an ICE’s combustion chamber. Before combusting hydrogen, it is critical to study its propagation and mixture behavior just immediately before burning. For this purpose, the DI-CHG.2 direct injector model by BorgWarner was used. This injector operated at 35 barG and 20 barG as maximum and minimum upstream pressures, respectively; a 5.8 g/s flow rate; and a maximum tip nozzle temperature of 250 °C. Experiments were performed using a high-pressure and high-temperature visualization vessel available at our facility. The combustion mixture prior to burning (spray) was visually controlled by the single-pass high-speed Schlieren technique. Images were used to study the spray penetration (S) and spray volume (V). Several parameters were considered to perform the experiments, such as the injection pressure (P_inj), chamber temperature (T_ch), and the injection energizing time (T_inj). With pressure ratio and injection time being the parameters commonly used in jet characterization, the addition of temperature formed a more comprehensive group of parameters that should generally aid in the characterization of this type of gas jets as well as the understanding of the combined effect of the rate of injection on the overall outcome. It was observed that the increase in injection pressure (P_inj) increased the spray penetration depth and its calculated volume, as well as the amount of mass injected inside the chamber according to the ROI results; furthermore, it was also observed that with a pressure difference of 20 bar (the minimum required for the proper functioning of the injector used), cyclic variability increased. The variation in temperature inside the chamber had less of an impact on the spray shape and its penetration; instead, it determined the velocity at which the spray reached its maximum length. In addition, the injection energizing time had no effect on the spray penetration. Full article

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

12 pages, 4610 KiB

Open AccessArticle

Standby Power Reduction of Home Appliance by the i-HEMS System Using Supervised Learning Techniques

by Beungyong Park, Suh-hyun Kwon and Byoungchull Oh

Energies 2024, 17(10), 2404; https://doi.org/10.3390/en17102404 (registering DOI) - 16 May 2024

Abstract

Electricity consumption in homes is on the rise due to the increasing prevalence of home appliances and longer hours spent indoors. Home energy management systems (HEMSs) are emerging as a solution to reduce electricity consumption and efficiently manage power usage at home. In the past, numerous studies have been conducted on the management of electricity production and consumption through solar power. However, there are limited human-centered studies focusing on the user’s lifestyle. In this study, we propose an Intelligent Home Energy Management System (i-HEMS) and evaluate its energy-saving effectiveness through a demonstration in a standard house in Korea. The system utilizes an IoT environment, PID sensing, and behavioral pattern algorithms. We developed algorithms based on power usage monitoring data of home appliances and human body detection. These algorithms are used as the primary scheduling algorithm and a secondary algorithm for backup purposes. We explored the deep connection between power usage, environmental sensor data, and input schedule data based on Long Short-Term Memory network (LSTM) and developed an occupancy prediction algorithm. We analyzed the use of common home appliances (TV, computer, water purifier, microwave, washing machine, etc.) in a standard house and the power consumption reduction by the i-HEMS system. Through a total of six days of empirical experiments, before implementing i-HEMS, home appliances consumed 13,062 Wh. With i-HEMS, the total consumption was reduced to 10,434 Wh (a 20% reduction), with 9060 Wh attributed to home appliances and 1374 Wh to i-HEMS operation. Full article

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

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41 pages, 13475 KiB

Open AccessFeature PaperReview

New Advances in Materials, Applications, and Design Optimization of Thermocline Heat Storage: Comprehensive Review

by Yunshen Zhang, Yun Guo, Jiaao Zhu, Weijian Yuan and Feng Zhao

Energies 2024, 17(10), 2403; https://doi.org/10.3390/en17102403 (registering DOI) - 16 May 2024

Abstract

To achieve sustainable development goals and meet the demand for clean and efficient energy utilization, it is imperative to advance the penetration of renewable energy in various sectors. Energy storage systems can mitigate the intermittent issues of renewable energy and enhance the efficiency and economic viability of existing energy facilities. Among various energy storage technologies, thermocline heat storage (THS) has garnered widespread attention from researchers due to its stability and economic advantages. Currently, there are only a few review articles focusing on THS, and there is a gap in the literature regarding the optimization design of THS systems. Therefore, this paper provides a comprehensive review of the recent research progress in THS, elucidating its principles, thermal storage materials, applications, and optimization designs. The novelty of this work lies in the detailed classification and analysis of various optimization designs for THS, including tank shape, aspect ratio, inlet/outlet configuration, thermal energy storage materials arrangement, operating strategies, and numerical model optimization approaches. The limitations of existing research are also identified, and future perspectives are proposed, aiming to provide recommendations for THS research and contribute to the development and promotion of THS technology. Full article

(This article belongs to the Topic Energy Storage and Conversion: From Materials to Technologies)

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12 pages, 4008 KiB

Open AccessArticle

Analysis of the Flow Behavior and Pressure Fluctuation of a Pump Turbine with Splitter Blades in Part-Load Pump Mode

by Wei Xiao, Shaocheng Ren, Liu Chen, Bin Yan, Yilin Zhu and Yexiang Xiao

Energies 2024, 17(10), 2402; https://doi.org/10.3390/en17102402 (registering DOI) - 16 May 2024

Abstract

The internal flow of a pump turbine is unstable in part-load pump mode for small guide-vane openings, and the strong vibration caused by pressure pulsation is related to the safe and stable operation of the unit. A pump turbine with a six-splitter-blade runner was chosen for unsteady simulation analyses. A standard k-epsilon turbulence model was adopted to study the unsteady flow and pressure pulsation in part-load pump mode. The predicted results show that the flow in the draft tube and the runner with splitter blades was relatively stable and the flow of the blade-to-blade channel was symmetrical. When the inlet and outlet velocity distribution of the vanes was not uniform, a vortex began to form in the stay-vane domain. The reason for this vortex formation is explained, and it is pointed out that the existence of the vortex and backflow leads to uneven velocity distribution. The unsteady calculation results showed that the pressure-pulsation peak-to-peak amplitudes in the vaneless area and guide vanes were much higher than those of other monitor points because of rotor–stator interference between the rotating runner and the vanes. In addition, the pulsation characteristics of the monitor points at different circumferential positions in the vaneless region were quite different. In the vaneless area, the velocity gradient along the circumferential direction was very large, and there was a phenomenon of backflow. Also, the pressure pulsation was 0.2 times that of the runner rotational frequency, and the blade-passing frequency was a third-order frequency. At the outlet of the guide vane, the pressure pulsation was mainly of a low frequency with a complex vortex flow. Finally, the pressure pulsation began to decrease rapidly in the stay-vane region. Full article

(This article belongs to the Special Issue Recent Advances in Hydro-Mechanical Turbines: Powering the Future)

15 pages, 1157 KiB

Open AccessArticle

An Adaptive Virtual Inertial Control Strategy for DC Distribution Networks

by Junhua Xu, Weixun Liu and Guopeng He

Energies 2024, 17(10), 2401; https://doi.org/10.3390/en17102401 (registering DOI) - 16 May 2024

Abstract

The DC distribution network is a low-inertia system, which is very sensitive to load disturbance, system failure, and other factors. By adding virtual capacitance to the converter connected to the power supply, the virtual inertia of the DC power grid can be improved. Firstly, this paper proposes a strategy for adjusting virtual capacitance based on the voltage change rate to achieve adaptive control of virtual inertia, which enables the converter to quickly absorb or release energy during power fluctuations. Secondly, the adaptivity of the strategy is improved and the main control parameters in the proposed control method are qualitatively analyzed. Finally, the four-terminal photovoltaic storage DC distribution network system is constructed. Through Simulink, the adaptive virtual inertia control is incorporated on the battery side to simulate and validate the effectiveness of the strategy and the rationality of parameter analysis. The results show that this method can provide flexible and adjustable inertia support for DC grids and improve the voltage stability of DC grids. Full article

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

25 pages, 759 KiB

Open AccessReview

Reviewing Control Paradigms and Emerging Trends of Grid-Forming Inverters—A Comparative Study

by Khaliqur Rahman, Jun Hashimoto, Dai Orihara, Taha Selim Ustun, Kenji Otani, Hiroshi Kikusato and Yasuhiro Kodama

Energies 2024, 17(10), 2400; https://doi.org/10.3390/en17102400 (registering DOI) - 16 May 2024

Abstract

Grid-forming inverters (GFMs) have emerged as crucial components in modern power systems, facilitating the integration of renewable energy sources and enhancing grid stability. The significance of GFMs lies in their ability to autonomously establish grid voltage and frequency, enabling grids to form and improve system flexibility. Discussing control methods for grid-forming inverters is paramount due to their crucial role in shaping grid dynamics and ensuring reliable power delivery. This paper explores the fundamental and advanced control methods employed by GFMs, explaining their operational principles and performance characteristics. Basic control methods typically involve droop control, voltage and frequency regulation, and power-balancing techniques to maintain grid stability under varying operating conditions. Advanced control strategies encompass predictive control, model predictive control (MPC), and adaptive control, which influence advanced algorithms and real-time data for enhanced system responsiveness and efficiency. A detailed analysis and performance comparison of different control methods for GFM is presented, highlighting their strengths, limitations, and suitability for diverse grid environments. Through comprehensive studies, this research interprets the ability of various control strategies to mitigate grid disturbances, optimize power flow, and enhance overall system stability. Full article

(This article belongs to the Special Issue Challenges and Prospects of Grid Support in Grid-Forming Inverters)

16 pages, 1753 KiB

Open AccessArticle

Phase Distribution of Gas–Liquid Slug–Annular Flow in Horizontal Parallel Micro-Channels

by Yanchu Liu, Siqiang Jiang and Shuangfeng Wang

Energies 2024, 17(10), 2399; https://doi.org/10.3390/en17102399 (registering DOI) - 16 May 2024

Abstract

As a transitional flow pattern, slug–annular flow occurs over a wide range of operating conditions in micro-channels while its distribution in parallel micro-channels has not been well characterized. Herein, we conducted an experiment to study the phase distribution of slug–annular flow in parallel micro-channels. The test section consists of a header with a diameter of 0.48 mm and six branch channels with a diameter of 0.40 mm. Nitrogen and 0.03 wt% sodium dodecyl sulfate (SDS) solution were used as the test fluids. It was found that the phase distribution of the slug–annular flow was unstable and the duration of the varying process showed regularity with different inlet conditions. Increasing the liquid superficial velocity facilitated the liquid phase to flow into channels at the fore part of the header, while the channels at the rear part of the header were more supplied with liquid as the gas superficial velocity, volume fraction of gas, and volume flow rate increased. Furthermore, the results indicated that the channels located at the rear part of the header experienced a pronounced enhancement in the supply of both the liquid and gas phases, with the spacing between the branches increasing. A predictive correlation was formulated to ascertain the distribution of the liquid phase within slug–annular flow across parallel micro-channels. Full article

(This article belongs to the Special Issue Latest Advances In and Prospects of Multiphase Flow and Heat and Mass Transfer)

24 pages, 1976 KiB

Open AccessArticle

Strategic Model for Yellow Hydrogen Production Using the Metalog Family of Probability Distributions

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

Energies 2024, 17(10), 2398; https://doi.org/10.3390/en17102398 (registering DOI) - 16 May 2024

Abstract

Storing energy in hydrogen has been recognized by scientists as one of the most effective ways of storing energy for many reasons. The first of these reasons is the availability of technology for producing hydrogen from water using electrolytic methods. Another aspect is the availability of relatively cheap energy from renewable energy sources. Moreover, you can count on the availability of large amounts of this energy. The aim of this article is to support the decision-making processes related to the production of yellow hydrogen using a strategic model which exploits the metalog family of probability distributions. This model allows us to calculate, with accuracy regarding the probability distribution, the amount of energy produced by photovoltaic systems with a specific peak power. Using the model in question, it is possible to calculate the expected amount of electricity produced daily from the photovoltaic system and the corresponding amount of yellow hydrogen produced. Such a strategic model may be appropriate for renewable energy developers who build photovoltaic systems intended specifically for the production of yellow and green hydrogen. Based on our model, they can estimate the size of the photovoltaic system needed to produce the assumed hydrogen volume. The strategic model can also be adopted by producers of green and yellow hydrogen. Due to precise calculations, up to the probability distribution, the model allows us to calculate the probability of providing the required energy from a specific part of the energy mix. Full article

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

19 pages, 2976 KiB

Open AccessArticle

Long-Term Energy System Modelling for a Clean Energy Transition in Egypt’s Energy Sector

by Anna Gibson, Zen Makuch, Rudolf Yeganyan, Naomi Tan, Carla Cannone and Mark Howells

Energies 2024, 17(10), 2397; https://doi.org/10.3390/en17102397 (registering DOI) - 16 May 2024

Abstract

Egypt has the potential to generate a significant amount of energy from renewable technologies, in particular solar PV, concentrated solar power (CSP), and onshore and offshore wind. The energy sector is reliant on fossil fuels, particularly natural gas, for electricity production and is at risk of locking itself into a high carbon pathway. Globally, reducing greenhouse gas (GHG) emissions associated with national energy sectors is a target outlined in the UN’s Paris Agreement. To reduce carbon dioxide (CO₂) emissions associated with a higher dependence on fossil fuels, Egypt must consider upscaling renewable energy technologies (RETs) to achieve a clean energy transition (CET). This research modelled six scenarios using clicSAND for OSeMOSYS to identify the technologies and policy target improvements that are needed to upscale RETs within Egypt’s energy sector. The results showed that solar PV and onshore wind are key technologies to be upscaled to contribute towards Egypt’s CET. The optimal renewable target is the International Renewable Energy Agency’s (IRENA) target of 53% of electricity being sourced from RETs by 2030, which will cost USD 16.4 billion more up to 2035 than Egypt’s current Integrated Sustainable Energy Strategy (ISES) target of 42% by 2035; it also saves 732.0 MtCO₂ over the entire modelling period to 2070. Socio-economic barriers to this transition are considered, such as recent discoveries of natural gas reserves combined with a history of energy insecurity, political instability impacting investor confidence, and a lack of international climate funding. The paper concludes with policy recommendations that would enable Egypt to progress towards achieving a CET. Full article

(This article belongs to the Collection Energy Transition towards Carbon Neutrality)

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28 pages, 642 KiB

Open AccessArticle

European Climate Policy in the Context of the Problem of Methane Emissions from Coal Mines in Poland

by Bożena Gajdzik, Katarzyna Tobór-Osadnik, Radosław Wolniak and Wiesław Wes Grebski

Energies 2024, 17(10), 2396; https://doi.org/10.3390/en17102396 (registering DOI) - 16 May 2024

Abstract

This paper presents a thorough examination of methane capture from Polish coal mines, contextualized within the framework of the European Union’s (EU) climate policy objectives. Through a strategic analysis encompassing the interior of coal mines, the surrounding environment, and the macro environment, this study elucidates the complex dynamics involved in methane emissions and capture initiatives. The key findings include a declining trend in absolute methane emissions since 2008, despite fluctuations in coal extraction volumes, and a relatively stable level of methane capture exceeding 300 million m³/year since 2014. The analysis underscores the critical role of government support, both in terms of financial incentives and streamlined regulatory processes, to facilitate the integration of methane capture technologies into coal mining operations. Collaboration through partnerships and stakeholder engagement emerges as essential for overcoming resource competition and ensuring the long-term success of methane capture projects. This paper also highlights the economic and environmental opportunities presented by methane reserves, emphasizing the importance of investment in efficient extraction technologies. Despite these advancements, challenges persist, particularly regarding the low efficiency of current de-methanation technologies. Recommendations for modernization and technological innovation are proposed to enhance methane capture efficiency and utilization. Full article

(This article belongs to the Special Issue Renewable Energy Sources towards a Zero-Emission Economy)

22 pages, 819 KiB

Open AccessArticle

Short-to-Medium-Term Wind Power Forecasting through Enhanced Transformer and Improved EMD Integration

by Jiafei Huan, Li Deng, Yue Zhu, Shangguang Jiang and Fei Qi

Energies 2024, 17(10), 2395; https://doi.org/10.3390/en17102395 (registering DOI) - 16 May 2024

Abstract

Accurate wind power forecasting (WPF) is critical in optimizing grid operations and efficiently managing wind energy resources. Challenges arise from the inherent volatility and non-stationarity of wind data, particularly in short-to-medium-term WPF, which extends to longer forecast horizons. To address these challenges, this study introduces a novel model that integrates Improved Empirical Mode Decomposition (IEMD) with an enhanced Transformer called TransIEMD. TransIEMD begins by decomposing the wind speed into Intrinsic Mode Functions (IMFs) using IEMD, transforming the scalar wind speed into a vector form that enriches the input data to reveal hidden temporal dynamics. Each IMF is then processed with channel attention, embedding, and positional encoding to prepare inputs for an enhanced Transformer. The Direct Embedding Module (DEM) provides an alternative viewpoint on the input data. The distinctive perspectives of IEMD and DEM offer interaction through cross-attention within the encoder, significantly enhancing the ability to capture dynamic wind patterns. By combining cross-attention and self-attention within the encoder–decoder structure, TransIEMD demonstrates enhanced proficiency in detecting and leveraging long-range dependencies and dynamic wind patterns, improving the forecasting precision. Extensive evaluations on a publicly available dataset from the National Renewable Energy Laboratory (NREL) demonstrate that TransIEMD significantly improves the forecasting accuracy across multiple horizons of 4, 8, 16, and 24 h. Specifically, at the 24 h forecast horizon, TransIEMD achieves reductions in the normalized mean absolute error and root mean square error of 4.24% and 4.37%, respectively, compared to the traditional Transformer. These results confirm the efficacy of integrating IEMD with attention mechanisms to enhance the accuracy of WPF. Full article

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

14 pages, 2706 KiB

Open AccessArticle

Methodology for Selecting a Location for a Photovoltaic Farm on the Example of Poland

by Katarzyna Stala-Szlugaj, Piotr Olczak, Jaroslaw Kulpa and Maciej Soltysik

Energies 2024, 17(10), 2394; https://doi.org/10.3390/en17102394 (registering DOI) - 16 May 2024

Abstract

As the LCOE for photovoltaics has decreased several times, it is once again gaining popularity. The intensification of the development of PV installations is contributing to the duck curve phenomenon in an increasing number of countries and, consequently, affecting current electricity prices. Decisions on new investments in large-scale PV sources are driven by potential economic and environmental effects, and these, in turn, are subject to locational considerations, both as to the country and its region. In calculating the economic impact of locating a 1 MWp PV farm, it was assumed that the electricity generated by the farm would be fed into the national grid, and that the life of the PV farm would be 20 years. Poland was considered as an example country for the placement of a photovoltaic farm. The authors of this paper proposed that the main verification parameter is the availability of connection capacities to feed the produced electricity into the country’s electricity grid. The methodology proposed by the authors for the selection of the location of a PV farm consists of four steps: step (i) identification and selection of the administrative division of a given country; step (ii) verification of available connection capacities; step (iii) (two stages) verification of other factors related to the location of the PV farm (e.g., information on land availability and the distance of the land from the substation), and analysis of productivity at each potential location and electricity prices achieved on the power exchange; step (iv) economic analysis of the investment—analyses of PV farm energy productivity in monetary terms on an annual basis, cost analysis (CAPEX, OPEX) and evaluation of economic efficiency (DPP, NPV, IRR). The greatest impact on the economic efficiency of a PV project is shown by the value of land (as part of CAPEX), which is specific to a given location, and revenues from energy sales, which are pretty similar for all locations. Full article

(This article belongs to the Special Issue Energy Transformation from the Perspectives of the Individual Citizen and the Market)

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18 pages, 1627 KiB

Open AccessArticle

Effect of Biochar on Anaerobic Co-Digestion of Untreated Sewage Sludge with Municipal Organic Waste under Mesophilic Conditions

by Joisleen Ramírez, Euclides Deago and Arthur Mc Carty James Rivas

Energies 2024, 17(10), 2393; https://doi.org/10.3390/en17102393 (registering DOI) - 16 May 2024

Abstract

Anaerobic digestion (AD) is a biological process that occurs in the limited presence of oxygen. This process involves various difficulties during the operation, such as acidification and increased concentration of volatile fatty acids, which can inhibit methane production. Therefore, in this work, the impact of biochar on the co-digestion of untreated sludge and residual biomass under mesophilic conditions was studied. For the production of biochar, the gasification process was used at different temperatures: 759 °C (BL), 798 °C (BM), and 888 °C (BH). This biochar was added in concentrations of 0 g/L, 3.33 g/L, and 6.67 g/L at the beginning of the co-digestion process. The results showed that a concentration of 6.67 g/L with BH biochar increased the PBM by 18% compared to the control sample and reduced the chemical oxygen demand (COD) by 88%. In addition, there was a reduction of volatile fatty acids (VFA) of 42.75%. Furthermore, FTIR analysis demonstrated that biochar has appropriate functional groups for this process. These data suggest a good interaction of biochar with the mixture of sludge and municipal waste, indicating that biochar can improve the anaerobic co-digestion of untreated sludge and municipal waste. Full article

(This article belongs to the Section A4: Bio-Energy)

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19 pages, 3930 KiB

Open AccessArticle

Enhancing Probabilistic Solar PV Forecasting: Integrating the NB-DST Method with Deterministic Models

by Tawsif Ahmad, Ning Zhou, Ziang Zhang and Wenyuan Tang

Energies 2024, 17(10), 2392; https://doi.org/10.3390/en17102392 (registering DOI) - 16 May 2024

Abstract

Accurate quantification of uncertainty in solar photovoltaic (PV) generation forecasts is imperative for the efficient and reliable operation of the power grid. In this paper, a data-driven non-parametric probabilistic method based on the Naïve Bayes (NB) classification algorithm and Dempster–Shafer theory (DST) of evidence is proposed for day-ahead probabilistic PV power forecasting. This NB-DST method extends traditional deterministic solar PV forecasting methods by quantifying the uncertainty of their forecasts by estimating the cumulative distribution functions (CDFs) of their forecast errors and forecast variables. The statistical performance of this method is compared with the analog ensemble method and the persistence ensemble method under three different weather conditions using real-world data. The study results reveal that the proposed NB-DST method coupled with an artificial neural network model outperforms the other methods in that its estimated CDFs have lower spread, higher reliability, and sharper probabilistic forecasts with better accuracy. Full article

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

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23 pages, 1789 KiB

Open AccessArticle

Active Planning for Virtual Microgrids with Demand-Side and Distributed Energy Resources

by Lechuan Piao, Fei Xue, Shaofeng Lu, Lin Jiang, Bing Han and Xu Xu

Energies 2024, 17(10), 2391; https://doi.org/10.3390/en17102391 (registering DOI) - 16 May 2024

Abstract

In this paper, the notion of a cohesive and self-sufficient grid is proposed. Based on a cohesive and self-sufficient virtual microgrid, an active distribution network is optimally planned, and an optimal configuration of demand-side resources, distributed generations, and energy storage systems are generated. To cope with stochastic uncertainty from forecast error in wind speed and load, flexibility reserves are needed. In this paper, the supply relation between flexibility and uncertainty is quantified and integrated in an innovative index which is defined as cohesion. The optimization objectives are a minimized operational cost and system net-ability cohesion as well as self-sufficiency, which is defined as the abilities both to supply local load and to deal with potential uncertainty. After testing the optimal configuration in the PG&E 69 bus system, it is found that with a more cohesive VM partition, the self-sufficiency of VMs is also increased. Also, a case study on uncertainty-caused system imbalance is carried out to show how flexibility resources are utilized in real-time operational balance. Full article

(This article belongs to the Special Issue Optimizing Power Demand-Side Resources for Grid Security, Energy Efficiency, and Environmental Sustainability)

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19 pages, 2537 KiB

Open AccessArticle

Energy Efficiency Analysis of Waste-to-Energy Plants in Poland

by Marian Banaś, Tadeusz Pająk, Jakub Bator, Wojciech Wróbel and Józef Ciuła

Energies 2024, 17(10), 2390; https://doi.org/10.3390/en17102390 - 16 May 2024

Abstract

The issue of enhancing energy recovery efficiency is a key concern within the European Union’s climate protection efforts. In particular, it applies to all processes and plants for the harvesting, gathering, and conversion of energy. The abandonment of fossil fuels in favour of alternative energy sources, and the increasing of energy efficiency and its recovery, is now a widely accepted direction of energy development. This study focuses on facilities that recover and process energy from municipal waste left after recycling processes, known as waste-to-energy (WtE) plants. These plants’ energy recovery efficiency is governed by the R1 Formula in EU countries. This report is based on an analysis of four years of operational data from selected Polish municipal waste incinerators, supplemented by a discussion of various studies on energy recovery efficiency. The primary objective of this report is to evaluate the effectiveness of these plants in contributing to sustainable waste management and energy recovery. The main effect of the developed report is the set of results of the energy recovery efficiency factor values, determined based on the R1 formula valid in the EU legislation, tabulated and graphically illustrated, and calculated for five selected Polish waste-to-energy plants. The presented results, with their graphical interpretation, discussion, and conclusions, provide insights into several factors influencing the value of the R1 efficiency factor. They can be a valuable contribution to operators of waste-to-energy plants, especially those operating in countries outside the EU. Full article

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

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20 pages, 605 KiB

Open AccessReview

A Review on the Heat-Source Tower Heat Pump Systems in China

by Xiangyu Yao, Rong Feng and Xiuzhen Li

Energies 2024, 17(10), 2389; https://doi.org/10.3390/en17102389 - 16 May 2024

Abstract

Based on air-, water-, and ground-source heat pump systems, a novel type of heat pump system, named the heat-source tower heat pump system (HSTHPS), has recently been developed in the southern area of China. The HSTHPS overcomes the evaporator frosting problems of the air-source heat pump system (ASHPS) when the ambient temperature is lower, and it avoids the geological condition constraints of the water- and ground-source heat pump systems. However, studies on the HSTHPS are insufficient, thereby limiting its development and applications. Thus, the present review provides a detailed literature review on the advancements of HSTHPSs in China, including the HSTHPS operation principle, heat-source tower (HST) structure, heat and mass transfer characteristics, HSTHPS performance, antifreeze solution use, and antifreeze solution regeneration. Studies on the heat and mass transfer characteristics of HSTs are sufficient for guiding the application. Regarding open systems, the solution drifting to the air needs to resolved, and future studies need to focus on structure optimization for heat exchangers in closed systems. Moreover, advanced defrosting technology should be applied to closed-type HSTs, and a suitable operation strategy for HSTHPSs should be developed. Future priorities should involve integrating HSTHPSs with additional renewable energy in order to achieve continuous, stable, and efficient heating in winter based on the characteristics of local climate and renewable energy. Full article

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

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28 pages, 2664 KiB

Open AccessArticle

Getting Ready for Multi-Vendor and Multi-Terminal HVDC Technology

by Jaqueline Cabañas Ramos, Marc Moritz, Nico Klötzl, Ceciel Nieuwenhout, William Leon Garcia, Ilka Jahn, Dimitar Kolichev and Antonello Monti

Energies 2024, 17(10), 2388; https://doi.org/10.3390/en17102388 - 16 May 2024

Abstract

Interoperable multi-vendor High-Voltage Direct-Current (HVDC) grids are a key enabler for the integration of renewable energy (in particular offshore wind) and its transmission over longer distances to consumers. However, most HVDC systems today are single-vendor and point-to-point. Various technical and non-technical aspects need to be considered, for example, (real-time) testing, legal aspects (intellectual property and regulation), and the multi-vendor interoperability process. This paper presents findings from the READY4DC project, which is a larger and open European effort involving diverse stakeholders, including HVDC manufacturers, transmission system operators, wind developers, academia, and research institutes. It summarizes key technical recommendations, emphasizing comprehensive interaction studies and the development of a structured legal framework to facilitate the development and operation of a multi-vendor, multi-terminal HVDC grid. The READY4DC project highlights the need for increased harmonization, transparent communication among stakeholders, and future-oriented research to ensure the robustness and interoperability of interconnected grids. Collaborative efforts are key for addressing technical complexities and advancing the deployment of multi-vendor multi-terminal HVDC technology. Full article

(This article belongs to the Section F1: Electrical Power System)

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19 pages, 2520 KiB

Open AccessArticle

Sensorless Model Predictive Control of Permanent Magnet Synchronous Motors Using an Unscented Kalman Filter

by Dariusz Janiszewski

Energies 2024, 17(10), 2387; https://doi.org/10.3390/en17102387 - 16 May 2024

Abstract

This paper deals with the application of the Model Predictive Control (MPC) algorithm to the sensorless control of a Permanent Magnet Synchronous Motor (PMSM). The proposed estimation strategy, based on the unscented Kalman filter (UKF), uses only the measurement of the motor current for the online estimation of speed, rotor position and load torque. Information about the system state is fed into the MPC algorithm. The results verify the effectiveness and applicability of the proposed sensorless control technique. To demonstrate its real-world applicability, implementation in low-speed direct drive astronomy telescope mount systems is investigated. The outcomes of the implementation are thoroughly examined, leading to insightful conclusions drawn from the observed results. Through rigorous theoretical analysis and extensive simulation studies, this paper establishes a solid foundation for the proposed sensorless control technique. The results obtained from simulation studies and real-world applications underscore the efficacy and versatility of the proposed approach, offering valuable insights for the advancement of sensorless control strategies in motor applications. The main aim of this work is to demonstrate and validate the practical feasibility of combining two complex techniques, establishing that such an integration is not only possible but also effective in achieving the desired objectives. Full article

(This article belongs to the Special Issue Advanced Control in Power Electronics, Drives and Generators)

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27 pages, 1468 KiB

Open AccessArticle

Policy Assessment for Energy Transition to Zero- and Low-Emission Technologies in Pickup Trucks: Evidence from Mexico

by Julieth Stefany Garcia, Laura Milena Cárdenas, Jose Daniel Morcillo and Carlos Jaime Franco

Energies 2024, 17(10), 2386; https://doi.org/10.3390/en17102386 - 15 May 2024

Abstract

The transport sector is under scrutiny because of its significant greenhouse gas emissions. Essential strategies, particularly the adoption of zero- and low-emission vehicles powered by electricity, are crucial for mitigating emissions in road transport. Pickups, which are integral to Mexico’s fleet, contribute to such emissions. Thus, implementing effective policies targeting pickups is vital for reducing air pollution and aligning with Mexico’s decarbonization objectives. This paper presents a simulation model based on system dynamics to represent the adoption process of zero- and low-emission vehicles, with a focus on pickups and utilizing data from the Mexican case. Three policy evaluation scenarios are proposed based on the simulation model: business as usual; disincentives for zero- and low-emission vehicles; and incentives for unconventional vehicles. One of the most significant findings from this study is that even in a scenario with a greater number of vehicles in circulation, if the technology is fully electric, the environmental impact in terms of emissions is lower. Additionally, a comprehensive sensitivity analysis spanning a wide spectrum is undertaken through an extensive computational process, yielding multiple policy scenarios. The analysis indicates that to achieve a maximal reduction in the country’s emissions, promoting solely hybrid electric vehicles and plug-in hybrid electric vehicles is advisable, whereas internal combustion engines, vehicular natural gas, and battery electric vehicles should be discouraged. Full article

(This article belongs to the Special Issue Energy Management Systems of Electric Vehicles: New Trends and Dynamic Futures)

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