Energies

27 pages, 8210 KiB

Open AccessArticle

Estimation of Wind Conditions in the Offshore Direction Using Multiple Numerical Models and In Situ Observations

by Mizuki Konagaya, Teruo Ohsawa, Yuki Itoshima, Masaki Kambayashi, Edouard Leonard, Eric Tromeur, Takeshi Misaki, Erika Shintaku, Ryuzo Araki and Kohei Hamada

Energies 2025, 18(11), 3000; https://doi.org/10.3390/en18113000 - 5 Jun 2025

Viewed by 260

Abstract

This study aims to estimate nearshore wind conditions using multiple numerical models and evaluate their accuracy at heights relevant to offshore wind turbines. An intensive observation campaign was conducted from December 2021 to February 2022 at Mutsu Ogawara Port, Japan. The observed data [...] Read more.

This study aims to estimate nearshore wind conditions using multiple numerical models and evaluate their accuracy at heights relevant to offshore wind turbines. An intensive observation campaign was conducted from December 2021 to February 2022 at Mutsu Ogawara Port, Japan. The observed data were used to validate the accuracy of numerical models (mesoscale, computational fluid dynamics (CFD), and linear models) to estimate wind conditions and investigate thermal environments, including atmospheric stability. The results demonstrated that the accuracy of period-averaged wind speed estimation in the offshore direction improved significantly when using an offshore observation point as a reference, with biases within ±2.5% up to 5 km offshore for all models. However, the accuracy of vertical shear estimation varies widely among models, with several models overestimating vertical shear, particularly in the sea wind sector. The mesoscale model, which accounts for spatiotemporal variations in atmospheric stability, consistently achieves high estimation accuracy. In contrast, standalone CFD models, which typically assume neutral atmospheric stability, are difficult to estimate accurately. Nonetheless, incorporating specific atmospheric stability conditions into the CFD models significantly enhanced their accuracy. These findings underscore the importance of atmospheric stability when estimating offshore wind conditions, particularly in nearshore areas. Full article

(This article belongs to the Special Issue Computational and Experimental Fluid Dynamics for Wind Energy)

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24 pages, 5238 KiB

Open AccessArticle

Investigation of Wake Expansion for Spanwise Arranged Turbines in the Offshore Wind Farm by Large Eddy Simulation

by Zhichang Liang, Jingjing Zhang, Xinru Guo and Haixiao Liu

Energies 2025, 18(11), 2999; https://doi.org/10.3390/en18112999 - 5 Jun 2025

Viewed by 216

Abstract

The issue of wind turbine wake effects in the offshore environment has become increasingly important with the development of offshore wind farms. The problem of wake dispersion from turbines plays a crucial role in evaluating the wake velocity deficit and solving the optimization [...] Read more.

The issue of wind turbine wake effects in the offshore environment has become increasingly important with the development of offshore wind farms. The problem of wake dispersion from turbines plays a crucial role in evaluating the wake velocity deficit and solving the optimization problem of wind farms. This study focuses on the wake expansion of spanwise arranged turbines using Large Eddy Simulation (LES). Firstly, numerical models are compared with the data from previous studies to validate their accuracy. Secondly, the study analyses wake structures for varying lateral spacings in spanwise turbine configurations using the actuator line model (ALM). Lastly, by comparing the predictions of wake expansion between existing models, a modified model considering added turbulence is proposed and then validated using LES data, significantly enhancing accuracy for predicting the wake width under different array spacings in the wind farm. Full article

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

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18 pages, 8919 KiB

Open AccessArticle

Model Reference Adaptive Sensorless Control of Variable-Speed Pumped Storage Doubly Fed Induction Machine Under Reversible Operations

by Zhi Zheng, Ziqiang Man, Shuxin Tan, Wei Yan, Yu Lu, Jie Tian, Weiqun Liu and Xu Wang

Energies 2025, 18(11), 2998; https://doi.org/10.3390/en18112998 - 5 Jun 2025

Viewed by 165

Abstract

The sensorless control of doubly fed induction machine (DFIM) rotor magnetic flux based on a model reference adaptive system (MRAS) is proposed to improve the reliability of a large-scale variable-speed pumped storage (VSPS) system and reduce operation and maintenance costs. The existing sensorless [...] Read more.

The sensorless control of doubly fed induction machine (DFIM) rotor magnetic flux based on a model reference adaptive system (MRAS) is proposed to improve the reliability of a large-scale variable-speed pumped storage (VSPS) system and reduce operation and maintenance costs. The existing sensorless control of doubly fed induction machines (DFIMs) is mostly focused on generator operation, making it difficult to apply to the VSPS system. The proposed strategy realizes the reversible operations of the VSPS through the design of an adaptive law under variable operating conditions, eliminating mechanical sensors, and possessing the characteristics of simple implementation and accurate identification. The mathematical model of the DFIM in a VSPS system is constructed, and an MRAS vector control strategy based on stator voltage orientation is established. The rotor angle and speed under reversible operating conditions are effectively identified by dynamically adjusting the angle error between the rotor flux reference model and the adaptive model to approach zero. Subsequently, comparative analysis with the closed-loop direct detection method verifies the advantages of the proposed strategy. The proposed control method can accurately identify rotor position and speed in the pumping and power generation conditions of the VSPS system and it demonstrates robust adaptability. Full article

(This article belongs to the Special Issue Advanced Control Strategies for Multiphase Induction Generators: Design, Optimization, and Application 2024)

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16 pages, 1256 KiB

Open AccessArticle

A Study on CO₂ Emission Reduction Using Operating Internal Combustion Engine Vehicles (ICEVs) and Electric Vehicles (EVs) for Rental Vehicles, Focusing on South Korea

by Soongil Kwon and Yoon-Seong Chang

Energies 2025, 18(11), 2997; https://doi.org/10.3390/en18112997 - 5 Jun 2025

Viewed by 203

Abstract

Regarding the goals for achieving carbon neutrality by 2025, the transportation sector is one of the main causes of various environmental burdens, such as greenhouse gas (GHG) emissions and resource depletion, so reducing the environmental impact of the automobile industry is important. Although [...] Read more.

Regarding the goals for achieving carbon neutrality by 2025, the transportation sector is one of the main causes of various environmental burdens, such as greenhouse gas (GHG) emissions and resource depletion, so reducing the environmental impact of the automobile industry is important. Although many countries are conducting numerous studies on the environmental impact of electric vehicles, they are limited to each country’s vehicles and models, and are limited to the production and process stages. In this study, we compared and analyzed the carbon reductions in electric and internal combustion engine vehicles during the operation stage for the most commonly used mid-sized rental vehicles in South Korea. The research results confirmed a reduction effect of approximately 1 MtCO₂-eq per year based on approximately 570,000 vehicles, and, if applied to all passenger vehicles nationwide, an average annual reduction effect of approximately 36 MtCO₂ can be expected. This figure corresponds to a reduction of approximately 30% in domestic transportation sector carbon emissions in 2024. This study is expected to have potential as a strategic indicator to start with, tailorable to the characteristics of each country’s transportation sector’s decarbonization processes. Full article

(This article belongs to the Section B3: Carbon Emission and Utilization)

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13 pages, 1125 KiB

Open AccessArticle

Oxidative Pyrolysis of Typical Volatile Model Compounds Under Low Oxygen Equivalence Ratios During Oxidative Pyrolysis of Biomass

by Liying Wang, Dan Lin, Dongjing Liu, Xing Xie, Shihong Zhang and Bin Li

Energies 2025, 18(11), 2996; https://doi.org/10.3390/en18112996 - 5 Jun 2025

Viewed by 196

Abstract

This study aims to investigate the oxidative pyrolysis of biomass volatiles with a particular focus on the formation of liquid products. Furfural, hydroxyacetone, and 3,4-dimethoxybenzaldehyde were chosen as volatile model compounds. The impacts of the oxygen equivalence ratio (ER, 0–15%) and temperature (400–500 [...] Read more.

This study aims to investigate the oxidative pyrolysis of biomass volatiles with a particular focus on the formation of liquid products. Furfural, hydroxyacetone, and 3,4-dimethoxybenzaldehyde were chosen as volatile model compounds. The impacts of the oxygen equivalence ratio (ER, 0–15%) and temperature (400–500 °C) on the product composition and distribution were examined using a two-stage quartz-tube reactor. The results showed that volatile pyrolysis was limited at the lower temperature of 400 °C even with oxygen introduction, while it could be significantly promoted at 500 °C as illustrated by the observed great decrease in the GC-MS peak areas of the volatile compounds especially under an oxidative atmosphere. For instance, the peak area of 3,4-dimethoxybenzaldehyde at 500 °C under an ER of 4% was only ~9% of that at 400 °C. Oxygen introduction enhanced the volatile decomposition with the formation of mainly permanent gases (although not given in the study) rather than liquid products, but distinct impacts were obtained for varied volatile compounds possibly due to their different chemical structures and autoignition temperatures. From the perspective of liquid product formation, furfural would undergo the cleavage of C-C/C-O bonds to form linear intermediates and subsequent aromatization to generate aromatics (benzene and benzofuran). The presence of oxygen could enhance the oxidative destruction of the C-C/C-O bonds and the removal of O from the molecules to form simple aromatics such as benzene, phenol, and toluene. Hydroxyacetone mainly underwent C-C/C-O cleavage that was further enhanced in the presence of oxygen; the resultant intermediates would recombine to generate acetoin and 2,3-pentanedione. A higher ER would directly oxidize the alcoholic hydroxyl group (-OH) into an aldehyde group (-CHO) to form methyl glyoxal, while 3,4-dimethoxybenzaldehyde mainly underwent cleavage and recombination of bonds connected with the benzene ring including aldehyde group (-CHO), C_Ar-O, C_Methoxy-O bonds, thus forming 1,2-dimethoxybenzene, toluene, and 3-hydroxybenzadehyde. This study provides more fundamental insights into the homogeneous oxidation of volatiles during the oxidative fast pyrolysis of biomass, facilitating the deployment of this technology. Full article

(This article belongs to the Special Issue Advanced Energy Technologies and Energy Savings: Low Emissions and High Efficiency)

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25 pages, 4443 KiB

Open AccessArticle

Experimental Investigation of the Influence of Climatic Conditions and Vehicle Dynamics on the Thermal Management System of a Fuel Cell Electric Vehicle

by Yannick Heynen, Ralf Liedtke, Michael Schier and Florian Heckert

Energies 2025, 18(11), 2995; https://doi.org/10.3390/en18112995 - 5 Jun 2025

Viewed by 182

Abstract

In this study, the cooling performance of fuel cell electric vehicles (FCEVs) with regard to thermal derating is investigated. Particularly in hot climate conditions, low operating temperature of the fuel cell stack and hence low temperature difference to the environment can result in [...] Read more.

In this study, the cooling performance of fuel cell electric vehicles (FCEVs) with regard to thermal derating is investigated. Particularly in hot climate conditions, low operating temperature of the fuel cell stack and hence low temperature difference to the environment can result in thermal derating of the fuel cell stack. Experimental investigations on a production vehicle with a fuel cell drive (Hyundai Nexo) are conducted to analyze the influence of climatic boundary conditions and a dynamic driving scenario on the thermal management system of the vehicle. Therefore, a new method based on energy balances is introduced to indirectly measure the average cooling air velocity at the cooling module. The results indicate that the two high-power radiator fans effectively maintain a high cooling airflow between a vehicle speed of approximately 30 and 100

k m / h

, leading to efficient heat rejection at the cooling module largely independent of vehicle speed. Furthermore, this study reveals that the efficiency of the fuel cell system is notably affected by ambient air temperature, attributed to the load on the electric air compressor (EAC) as well as on cooling system components like cooling pump and radiator fans. However, at the stack level, balance of plant (BoP) components demonstrate the ability to ensure ambient temperature-independent performance, likely due to reliable humidification control up to 45 °C. Additionally, a new method for determining thermal derating of FCEVs on roller dynamometer tests is presented. A real-world uphill drive under ambient temperatures exceeding 40 °C demonstrates derating occurring in 6.3% of the time, although a worst case with an aged stack and high payload is not investigated in this study. Finally, a time constant of 50

s

is found to be suitable to correlate the average fuel cell stack power with a coolant temperature at the stack inlet, which gives information on the thermal inertia of the system observed and can be used for future simulation studies. Full article

(This article belongs to the Section J: Thermal Management)

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24 pages, 3715 KiB

Open AccessArticle

Analysis of Renewable Energy Absorption Potential via Security-Constrained Power System Production Simulation

by Zhihui Feng, Yaozhong Zhang, Jiaqi Liu, Tao Wang, Ping Cai and Lixiong Xu

Energies 2025, 18(11), 2994; https://doi.org/10.3390/en18112994 - 5 Jun 2025

Viewed by 176

Abstract

The increasing penetration of renewable energy sources presents significant challenges for power system stability and operation. Accurately assessing renewable energy absorption capacity is essential to ensuring grid reliability while maximizing renewable integration. This paper proposes a security-constrained sequential production simulation (SPS) framework, which [...] Read more.

The increasing penetration of renewable energy sources presents significant challenges for power system stability and operation. Accurately assessing renewable energy absorption capacity is essential to ensuring grid reliability while maximizing renewable integration. This paper proposes a security-constrained sequential production simulation (SPS) framework, which incorporates grid voltage and frequency support constraints to provide a more realistic evaluation of renewable energy absorption capability. Additionally, hierarchical clustering (HC) based on dynamic time warping (DTW) and min-max linkage is employed for temporal aggregation (TA), significantly reducing computational complexity while preserving key system characteristics. A case study on the IEEE 39-bus system, integrating wind and photovoltaic generation alongside high-voltage direct current (HVDC) transmission, demonstrates the effectiveness of the proposed approach. The results show that the security-constrained SPS successfully prevents overvoltage and frequency deviations by bringing additional conventional units online. The study also highlights that increasing grid demand, both locally and through HVDC export, enhances renewable energy absorption, though adequate grid support remains crucial. Full article

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28 pages, 6191 KiB

Open AccessArticle

The Environmental Dimension of Sustainable Development in Relation to the Transition from Brown to Green Energy—A Case Study of Poland from 2005 to 2023

by Mateusz Ciski and Krzysztof Rząsa

Energies 2025, 18(11), 2993; https://doi.org/10.3390/en18112993 - 5 Jun 2025

Viewed by 283

Abstract

The transition of the energy sector to green energy is one of the priorities of sustainable development, serving as an important instrument for balancing economic growth and environmental protection. The purpose of this article is to analyze the relationship between the share of [...] Read more.

The transition of the energy sector to green energy is one of the priorities of sustainable development, serving as an important instrument for balancing economic growth and environmental protection. The purpose of this article is to analyze the relationship between the share of renewable energy in total electricity production and the Environmental Dimension of Sustainable Development in the voivodeships of Poland during the years 2005–2023. To avoid difficulties in interpreting the statistical model—arising from challenges in determining the precise nature of the relationship between individual explanatory variables and the dependent variable—a collinearity test (using the Variance Inflation Factor, VIF, in three stages) was conducted. The relationship was examined using various statistical methods, including Pearson’s linear correlation and linear regression. Additionally, to visualize the local variation in this relationship, a spatial variation study was carried out using Geographic Information System (GIS) tools, supported by a series of bivariate choropleth maps. The results may suggest a positive impact of an increase in the share of electricity production from renewable energy sources on the state of the environment; however, this finding requires further, more detailed research. Full article

(This article belongs to the Special Issue Challenges, Trends and Forecasting of Sustainable and Renewable Energy Systems: 2nd Edition)

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19 pages, 2782 KiB

Open AccessArticle

Numerical Study of the Condenser of a Small CO₂ Refrigeration Unit Operating Under Supercritical Conditions

by Piotr Szymczak, Piotr Bogusław Jasiński and Marcin Łęcki

Energies 2025, 18(11), 2992; https://doi.org/10.3390/en18112992 - 5 Jun 2025

Viewed by 152

Abstract

The paper presents a numerical analysis of a tube-in-tube condenser of a small refrigeration system. One of the challenges in designing such units is to reduce their dimensions while maintaining the highest possible cooling capacity, so the research presented here focuses on the [...] Read more.

The paper presents a numerical analysis of a tube-in-tube condenser of a small refrigeration system. One of the challenges in designing such units is to reduce their dimensions while maintaining the highest possible cooling capacity, so the research presented here focuses on the search for and impact of the appropriate flow conditions of these two fluids on condenser performance. The refrigerant is supercritical CO₂, which is cooled by water. Thermal-flow simulations were performed for eight CO₂ inlet velocities in the range of 1–8 m/s, and four cooling water velocities of 0.5–2 m/s. The main parameters of the exchanger operation were analyzed: heat transfer coefficient, Nusselt number, overall heat transfer coefficient, and friction factor, which were compared with selected correlations. The results showed that the condenser achieves the highest power for the highest water velocities (2 m/s) and CO₂ (8 m/s), i.e., over 1000 W, which corresponds to a heat flux on the tube surface of approx. 2.6 × 10⁵ W/m² and a heat transfer coefficient of approx. 4700 W/m²K. One of the most important conclusions is the discovery of a significant effect of water velocity on heat transfer from the CO₂ side—an increase in water velocity from 0.5 m/s to 2 m/s results in an increase in the heat transfer coefficient sCO₂ by over 60%, with the same Re number. The implication of this study is to show the possibility of adjusting and selecting condenser parameters over a wide range of capacities, just by changing the fluid velocity. Full article

(This article belongs to the Special Issue Advances in Supercritical Carbon Dioxide Cycle)

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26 pages, 3431 KiB

Open AccessArticle

Integrated Production and Multi-Market Optimization of Biomethane in Germany: A Two-Step Linear Programming Approach

by Milad Rousta, Joshua Güsewell and Ludger Eltrop

Energies 2025, 18(11), 2991; https://doi.org/10.3390/en18112991 - 5 Jun 2025

Viewed by 165

Abstract

From the perspective of biogas plant (BGP) operators, it is highly challenging to make a profitable decision on optimal biomethane production and allocation across interconnected markets. The aim of this study is to analyze the dynamics of biomethane markets, develop the gas allocation [...] Read more.

From the perspective of biogas plant (BGP) operators, it is highly challenging to make a profitable decision on optimal biomethane production and allocation across interconnected markets. The aim of this study is to analyze the dynamics of biomethane markets, develop the gas allocation portfolio (GAP) for BGPs, investigate the impact of GHG quota price on the market dynamics and substrate mix consumption, and evaluate the profitability of the biomethane market system under various demand-based scenarios. A two-step optimization approach based on linear programming is adopted. Firstly, the optimized substrate mix and corresponding GAP are determined for all BGPs. Secondly, by leveraging the options flexibility created by the interconnected nature of biomethane markets, the BGPs’ GAP is further developed. Through an in-depth sensitivity analysis, the effects of GHG quota price variations on the market dynamics are assessed. The results indicate that integrated production, obtained by implementing the improved GAP across all BGPs, maximizes the profitability of the system. At higher quota prices, the consumption of manure, residuals, and grass is encouraged, while the use of energy crops declines. Furthermore, higher quota prices lead to a substantial increase in biomethane price in the EEG market, highlighting the need for further governmental support for biomethane CHP units. The anticipated competition between hydrogen and biomethane to achieve a greater share in the heating sector could pose risks to long-term investments in biomethane. The system achieves its highest profitability, a total contribution margin of EUR 2254.8 million, under the Transport Biofuels Expansion scenario. Generally, policies and regulations that raise the quota price (e.g., the 36. BImSchV) or promote biomethane demand in the heating sector (e.g., the GEG) can provide both economic and ecological benefits to the system. Full article

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

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17 pages, 4736 KiB

Open AccessArticle

Station-Aggregator Response Resource Trading Mechanism Considering Energy–Power Coupling of Response Capability

by Haiqing Gan, Wenjun Ruan, Xiaodong Yuan, Xize Jiao, Mingshen Wang and Yi Pan

Energies 2025, 18(11), 2990; https://doi.org/10.3390/en18112990 - 5 Jun 2025

Viewed by 145

Abstract

China’s electric vehicle (EV) fleet has reached 30 million, and the effective utilization of their charging and discharging capabilities can provide substantial regulation support to restore supply–demand balance. A prerequisite to achieving this benefit is the proper estimation and utilization of the regulation [...] Read more.

China’s electric vehicle (EV) fleet has reached 30 million, and the effective utilization of their charging and discharging capabilities can provide substantial regulation support to restore supply–demand balance. A prerequisite to achieving this benefit is the proper estimation and utilization of the regulation potential inherent in EVs. This paper focuses on charging stations and introduces a station-aggregator response resource trading mechanism considering energy–power coupling of response capability. First, the response capacity of charging stations is estimated from both energy and power perspectives. Next, trading behavior models are developed separately for charging stations and aggregators. Finally, a joint resource trading mechanism based on a Stackelberg game is proposed to coordinate responses between these entities. Simulation results validate the effectiveness of the proposed estimation method and the economic advantages of the trading mechanism, thereby realizing a win–win outcome. Full article

(This article belongs to the Special Issue Advanced Control Systems for Power Electronics, Smart Grids, and Renewable Energy Integration)

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24 pages, 8887 KiB

Open AccessArticle

Investigating the Effect of Thermal Pretreatment on Chalcopyrite Grinding for Comminution Energy Reduction

by Kaveh Asgari and Qingqing Huang

Energies 2025, 18(11), 2989; https://doi.org/10.3390/en18112989 - 5 Jun 2025

Viewed by 207

Abstract

This study investigates the effect of thermal pretreatment on the grindability and energy efficiency of chalcopyrite ore using a ball mill, employing Box–Behnken design and statistical analysis to optimize key grinding parameters. The research utilized scanning electron microscopy (SEM), X-ray diffraction (XRD), and [...] Read more.

This study investigates the effect of thermal pretreatment on the grindability and energy efficiency of chalcopyrite ore using a ball mill, employing Box–Behnken design and statistical analysis to optimize key grinding parameters. The research utilized scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) to assess the structural changes in the ore after pretreatment at 300 °C and 600 °C. These analyses revealed significant modifications in the chalcopyrite structure, including reduced crystallinity, formation of new phases (such as oxides), and the development of microcracks, which contributed to improved grinding performance. Statistical analysis of the results showed that thermal pretreatment reduced specific energy consumption by approximately 10% and enhanced the particle size reduction (P80). The Box–Behnken design was used to optimize the mill speed and ball filling ratio, further improving energy efficiency. Results showed that reducing the mill speed decreased energy consumption while maintaining an optimal P80, whereas increasing the ball filling ratio reduced energy usage but resulted in a coarser product. Overall, this study demonstrated that thermal pretreatment, combined with optimized milling parameters through statistical design, can significantly enhance energy efficiency and grinding performance in chalcopyrite ore processing, offering practical solutions for industrial mineral processing. Full article

(This article belongs to the Special Issue Clean Utilization and Conversion Technologies of Coal)

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15 pages, 2320 KiB

Open AccessArticle

A Comparative Analysis of Solar Thermal and Photovoltaic Systems with Heat-Pump Integration in a New-Build House Under Controlled Conditions

by Christopher Tsang, Ljubomir Jankovic, William Swan, Richard Fitton and Grant Henshaw

Energies 2025, 18(11), 2988; https://doi.org/10.3390/en18112988 - 5 Jun 2025

Viewed by 206

Abstract

This study investigates the relative benefits of solar thermal (ST) and photovoltaic (PV) systems integrated with air-source heat pumps for domestic hot water production in newly built residential buildings. Using calibrated DesignBuilder simulations of “The Future Home” located in Energy House 2.0, an [...] Read more.

This study investigates the relative benefits of solar thermal (ST) and photovoltaic (PV) systems integrated with air-source heat pumps for domestic hot water production in newly built residential buildings. Using calibrated DesignBuilder simulations of “The Future Home” located in Energy House 2.0, an environmental chamber, the study analyzes energy performance and carbon emissions for eight scenarios: (1) baseline heat pump only, (2) heat pump with 4 m² PV panels, (3) heat pump with 4 m² ST panels, (4) heat pump with 2 m² PV + 2 m² ST panels, and (5–8) variants with increased hot water demand. While ST systems directly heat water through thermal energy transfer, PV systems contribute to water heating indirectly by providing electricity to power the heat pump. The results show that the ST system provides 964.6 kWh of thermal energy annually, increasing to 1528 kWh with enhanced hot water demand, while a similarly sized PV system generates 532.5 kWh of electricity. The research reveals that Standard Assessment Procedure methodology’s fixed hot water demand assumptions could significantly underpredict solar thermal benefits, potentially discouraging UK house builders from adopting this technology. Full article

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

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34 pages, 416 KiB

Open AccessArticle

Energy Poverty in Poland: Drivers, Measurement and National Policy

by Justyna Przywojska, Aldona Podgórniak-Krzykacz, Magdalena Kalisiak-Mędelska and Izabela Rącka

Energies 2025, 18(11), 2987; https://doi.org/10.3390/en18112987 - 5 Jun 2025

Viewed by 202

Abstract

The aim of this paper is to diagnose the extent of energy poverty in Poland and identify the instruments used in the public sector at the national level to address this challenge. In the theoretical part of the paper, we will review the [...] Read more.

The aim of this paper is to diagnose the extent of energy poverty in Poland and identify the instruments used in the public sector at the national level to address this challenge. In the theoretical part of the paper, we will review the literature related to the definition of the concept of energy poverty and the classification and measurement methodology of this phenomenon. In the research part, we will analyze the extent of the energy poverty phenomenon in Poland, review the Polish energy policy, and identify and characterize the instruments for tackling energy poverty in Poland implemented within the framework of national government programs. According to official statistics in Poland, depending on the adopted method of measuring energy poverty, in 2019, it affected between 4.2% and 15.4% of the population (the average across four indicators was 9% of the population). Our analyses confirmed the presence of energy poverty in Poland, which is a consequence of high energy prices and low energy efficiency of buildings. Energy poverty primarily affects people with the lowest incomes. Those particularly vulnerable are homeowners, especially residents of rural areas. The analysis of national strategies showed that although energy poverty is recognized at the government level, it is not a priority for the Polish government. There is a lack of a detailed diagnosis of energy poverty and a comprehensive, dedicated program for its reduction. Poland’s energy policy focuses primarily on limiting emissions and improving energy efficiency in buildings, which leads to the marginalization of the energy poverty issue. Full article

(This article belongs to the Special Issue Challenges and Opportunities for Energy Economics and Policy—2nd Edition)

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21 pages, 6358 KiB

Open AccessArticle

Experimental Study and Performance Analysis of a Recuperative Supercritical CO₂ Brayton Cycle

by Shucheng Zhang, Juntao Ke, Min Liu, Pingjian Ming and Guopeng Yu

Energies 2025, 18(11), 2986; https://doi.org/10.3390/en18112986 - 5 Jun 2025

Viewed by 174

Abstract

To investigate the operational characteristics of the supercritical carbon dioxide (S-CO₂) Brayton cycle and enhance its applicability in practical operating conditions for micro-scale reactors, an experimental platform for a recuperative S-CO₂ Brayton cycle is constructed and investigated. Several controllable operational [...] Read more.

To investigate the operational characteristics of the supercritical carbon dioxide (S-CO₂) Brayton cycle and enhance its applicability in practical operating conditions for micro-scale reactors, an experimental platform for a recuperative S-CO₂ Brayton cycle is constructed and investigated. Several controllable operational parameters, including compressor pump frequency, expansion valve opening, and electric heating power, each intrinsically linked to the thermal characteristics of its corresponding equipment, as well as the cooling water flow rate, are systematically adjusted and analyzed. Experimental results demonstrate that the cooling water flow rate has a significantly greater impact on the temperature and pressure of the cycle system compared to other operational parameters. Based on these findings, steady-state experiments are conducted within a pressure range of 8 MPa to 15 MPa and a temperature range of 70 °C to 150 °C. It is observed that the heat exchange capacity of the recuperator decreases as the cooling water flow rate is reduced, suggesting that sufficient cooling efficiency is required to maximize the recuperative function. Under the condition of a maximum system temperature of 150 °C, the isentropic efficiency of the expansion valve decreases with an increase in the inlet pressure of the valve. However, the overall thermal efficiency of the cycle system requires further calculation and assessment following the optimization of the experimental platform. The result of validation of experimental results is less than 20%. The findings presented in this study offer essential data that encompass the potential operational conditions of the CO₂ Brayton cycle section applicable to small-scale reactors, thereby providing a valuable reference for the design and operation of practical cycle systems. Full article

(This article belongs to the Special Issue Supercritical CO₂ Power Cycles)

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26 pages, 3712 KiB

Open AccessArticle

Production and Optimisation of Oxygenated Biofuel Blend Components via the Ethanolysis of Lignocellulosic Biomass: A Response Surface Methodology

by Mohamad A. Nahil, Omar Aboelazayem, Scott Wiseman, Neel Herar, Valerie Dupont, Ali Alazzawi, Alison S. Tomlin and Andrew B. Ross

Energies 2025, 18(11), 2985; https://doi.org/10.3390/en18112985 - 5 Jun 2025

Viewed by 226

Abstract

In this study, a response surface methodology (RSM) using a central composite design (CCD) was implemented to investigate the influence of process variables on ethyl levulinate (EL) production from the ethanolysis of waste corn cob samples, using sulphuric acid as a catalyst. The [...] Read more.

In this study, a response surface methodology (RSM) using a central composite design (CCD) was implemented to investigate the influence of process variables on ethyl levulinate (EL) production from the ethanolysis of waste corn cob samples, using sulphuric acid as a catalyst. The effects of four independent variables, namely, the temperature (A), the corn cob content (B), corn cob/H₂SO₄ mass ratio (C) and the reaction time (D) on the yields of EL (Y₁), diethyl ether (DEE) (Y₂) and solid residue (Y₃) were explored. Using multiple regression analysis, the experimental results were fitted to quadratic polynomial models. The predicted yields based on the fitted models were well within the experimental uncertainties. Optimum conditions for maximising the EL yield were found to be 176 °C, 14.6 wt. %, 21:1 and 6.75 h for A to D, respectively. A moderate-to-high EL yield (29.2%) from corn cob was achieved in optimised conditions, a result comparable to those obtained from model C₆ carbohydrate compounds. Side products were also produced, including diethyl ether, furfural, levulinic acid, 5-hydroxymethyl furfural, ethyl acetate, ethyl formate and water. Total unknown losses of only 5.69% were reported after material balancing. The results suggest that lignocellulosic waste such as corn cob can be used as a potential feedstock for the production of ethyl levulinate by direct acid-catalysed ethanolysis, but that the treatment of side products will need to be considered. Full article

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

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13 pages, 1451 KiB

Open AccessArticle

Study on the Optimization and Improvement of Control Strategies for Modular Multilevel Converter High Voltage Direct Current Connected to Weak Alternative Current Systems

by Wankai Yang, Guoliang Zhao and Dongming Han

Energies 2025, 18(11), 2984; https://doi.org/10.3390/en18112984 - 5 Jun 2025

Viewed by 149

Abstract

To address the stability problem related to grid-connected modular multilevel converter high voltage direct current (MMC HVDC) connected to weak alternative current (AC) systems, the short-circuit ratio (SCR) that affects the stability of the system was analyzed first. Short-circuit ratios with SCR values [...] Read more.

To address the stability problem related to grid-connected modular multilevel converter high voltage direct current (MMC HVDC) connected to weak alternative current (AC) systems, the short-circuit ratio (SCR) that affects the stability of the system was analyzed first. Short-circuit ratios with SCR values greater than 1.3 were obtained, and the system could still operate stably. By applying the theoretical equations of classical circuits, it has been theoretically proven that for the constant active power and constant AC voltage control modes on the weak system side, after the flexible direct current enters the weak system mode, the power must be reduced to ensure the stable operation of the system. Combined with the actual situation of the north channel of the Chongqing–Hubei back-to-back MMC HVDC project, which is connected to the weak system mode, measures such as the optimization of the control mode and the improvement of control functions in the weak system mode were proposed, and simulation calculations and real time digital simulator (RTDS) simulation verifications were carried out. These control strategies have been applied to the Chongqing–Hubei MMC HVDC project, and on-site verification tests have been conducted to ensure stable operation in the weak system mode. Full article

(This article belongs to the Special Issue Planning, Operation, and Control of New Power Systems)

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14 pages, 2902 KiB

Open AccessArticle

A Cost-Effective and Reliable Junction-Box–Integrated Rapid Shutdown System for BIPV Applications

by Joon-Young Jeon, Minkook Kim, Myungwoo Son, Ju-Hee Kim, Young-Dal Lee and Yong-Hyun Kim

Energies 2025, 18(11), 2983; https://doi.org/10.3390/en18112983 - 5 Jun 2025

Viewed by 215

Abstract

In response to fire safety risks associated with photovoltaic (PV) systems and evolving rapid shutdown requirements, this paper proposes a cost-effective and reliable rapid shutdown solution integrated directly into the PV module junction box. The system employs analog circuitry triggered by an external [...] Read more.

In response to fire safety risks associated with photovoltaic (PV) systems and evolving rapid shutdown requirements, this paper proposes a cost-effective and reliable rapid shutdown solution integrated directly into the PV module junction box. The system employs analog circuitry triggered by an external pulse-width modulation (PWM) signal, with optocoupler isolation and a controlled short-circuit method to rapidly reduce the module output voltage. Simulation and experimental results confirm that the output voltage is reduced to approximately 2 V within 280 ms, satisfying the U.S. National Electrical Code (NEC) 690.12 requirements. This junction-box–integrated approach eliminates the complexity of conventional module-level power electronics (MLPE) systems and offers a highly practical alternative for building-integrated photovoltaic (BIPV) applications where partial shading is minimal. Full article

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

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17 pages, 931 KiB

Open AccessArticle

Optimal Reactive Power Dispatch Planning Considering Voltage Deviation Minimization in Power Systems

by Orlando Álvarez, Diego Carrión and Manuel Jaramillo

Energies 2025, 18(11), 2982; https://doi.org/10.3390/en18112982 - 5 Jun 2025

Viewed by 190

Abstract

Transmission lines in electrical power systems are studied and analyzed to improve the electrical system’s safety, stability, and optimal operation. Past research has proposed various optimization methods to address the problem of active and reactive power; however, they do not consider the voltage [...] Read more.

Transmission lines in electrical power systems are studied and analyzed to improve the electrical system’s safety, stability, and optimal operation. Past research has proposed various optimization methods to address the problem of active and reactive power; however, they do not consider the voltage at the nodes, which causes losses in the system. By proposing a reduction in voltage at the nodes of the electrical system, it is possible to minimize voltage variation in the system using mixed integer nonlinear programming. The proposed methodology was tested on the IEEE 30-bus test system, where the objective function was modeled and simulated independently to test the results achieved through an AC OPF and reducing energy loss in the system. One of the most important investments was to demonstrate that the proposed methodology reduces voltage deviation at the system nodes, effectively confirming and maintaining lower active and reactive power production losses, resulting in a new type of energy planning that effectively benefits the electrical system voltage. Full article

(This article belongs to the Special Issue Simulation and Analysis of Electrical Power Systems)

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21 pages, 938 KiB

Open AccessArticle

Thermodynamic and Process Modeling of CO₂ Chemical Absorption Process Using Aqueous Monoethanolamine and Enzymatic Potassium Carbonate Solvents: Validation and Comparative Analysis

by Anthoula Plakia, Christina Papaioannou and Panagiotis Grammelis

Energies 2025, 18(11), 2981; https://doi.org/10.3390/en18112981 - 5 Jun 2025

Viewed by 240

Abstract

Carbon dioxide is a major contributor to global warming, with chemical absorption using aqueous monoethanolamine (MEA) being the most widespread technology for CO₂ capture. However, due to the limitations of MEA, alternative solvents should be examined. In this work, CO₂ capture [...] Read more.

Carbon dioxide is a major contributor to global warming, with chemical absorption using aqueous monoethanolamine (MEA) being the most widespread technology for CO₂ capture. However, due to the limitations of MEA, alternative solvents should be examined. In this work, CO₂ capture using potassium carbonate promoted by the enzyme carbonic anhydrase is compared to the conventional aqueous MEA solvent. For that purpose, models for both solvents are developed, focusing on accurate thermodynamic modeling of the mixtures and simulation of the processes. As a first step, the thermodynamic modeling of CO₂-H₂O-MEA and CO₂-H₂O-K₂CO₃ mixtures is examined. Parameters of the electrolyte non-random two-liquid (eNRTL) model in Aspen Plus V11 are updated through regression against binary and ternary solubility and heat capacity experimental data. The regression results are satisfactory. Afterwards, the updated eNRTL is applied to the development of rate-based process models, which are validated against experimental results from pilot plants presented in the literature to ensure their accuracy. Finally, the two solvents are compared, with enzymatic potassium carbonate emerging as a promising alternative to MEA for CO₂ capture. At optimized conditions and an 85% capture efficiency, the reboiler duties are 3.5 MJ/kg for enzymatic potassium carbonate and 4.2 MJ/kg CO₂ for MEA. Full article

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

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23 pages, 933 KiB

Open AccessReview

Characterising Non-Intentional Supraharmonic Emissions from Inverters in Power Grids: Review and Challenges

by Kasun Peiris, Sean Elphick and Duane Robinson

Energies 2025, 18(11), 2980; https://doi.org/10.3390/en18112980 - 5 Jun 2025

Viewed by 270

Abstract

Supraharmonic emissions, referred to as voltage/current waveform distortions in the 2–150 kHz range, have been identified as an emerging power quality concern. With the increased number of non-linear devices connected to the power grid, such as photovoltaic inverter systems, supraharmonic disturbances are expected [...] Read more.

Supraharmonic emissions, referred to as voltage/current waveform distortions in the 2–150 kHz range, have been identified as an emerging power quality concern. With the increased number of non-linear devices connected to the power grid, such as photovoltaic inverter systems, supraharmonic disturbances are expected to increase. Despite being a source of supraharmonic emissions, power electronic equipment has become a ubiquitous technology due to recent advancements. Similarly, researchers around the world have started studying these emissions; however, complete systematic knowledge concerning supraharmonic emissions is yet to be achieved. This paper uniquely delves into characterising emissions using existing knowledge, significantly improving the understanding of their complex micro-level interactions and highlighting emerging challenges. The paper presents a comprehensive summary integrating existing studies on supraharmonic emissions in five key areas: emissions, propagation and attenuation, measurement techniques, modelling and simulation, and mitigation. Full article

(This article belongs to the Special Issue Advances in Power Converters and Inverters)

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32 pages, 2378 KiB

Open AccessReview

Pyrolysis Process, Reactors, Products, and Applications: A Review

by Prakhar Talwar, Mariana Alzate Agudelo and Sonil Nanda

Energies 2025, 18(11), 2979; https://doi.org/10.3390/en18112979 - 5 Jun 2025

Viewed by 291

Abstract

With the rapid growth of the global population, increasing per capita energy demands, and waste generation, the need for innovative strategies to mitigate greenhouse gas emissions and effective waste management has become paramount. Pyrolysis, a thermochemical conversion process, facilitates the transformation of diverse [...] Read more.

With the rapid growth of the global population, increasing per capita energy demands, and waste generation, the need for innovative strategies to mitigate greenhouse gas emissions and effective waste management has become paramount. Pyrolysis, a thermochemical conversion process, facilitates the transformation of diverse biomass feedstocks, including agricultural biomass, forestry waste, and other carbonaceous wastes, into valuable biofuels such as bio-oil, biochar, and producer gas. The article reviews the benefits of pyrolysis as an effective and scalable technique for biofuel production from waste biomass. The review describes the different types of pyrolysis processes, such as slow, intermediate, fast, and catalytic, focusing on the effects of process parameters like temperature, heating rate, and residence time on biofuel yields and properties. The review also highlights the configurations and operating principles of different reactors used for pyrolysis, such as fixed bed, fluidized bed, entrained flow, plasma system, and microwaves. The review examines the factors affecting reactor performance, including energy consumption and feedstock attributes while highlighting the necessity of optimizing these systems to improve sustainability and economic feasibility in pyrolysis processes. The diverse value-added applications of biochar, bio-oil, and producer gas obtained from biomass pyrolysis are also discussed. Full article

(This article belongs to the Collection Bio-Energy Reviews)

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16 pages, 2501 KiB

Open AccessArticle

Long-Term Use of Nuclear Energy from the Aspect of Economy and Greenhouse Gas Emissions

by Dinka Lale and Dubravko Pevec

Energies 2025, 18(11), 2978; https://doi.org/10.3390/en18112978 - 5 Jun 2025

Viewed by 197

Abstract

Conventional sources of electricity are limited and they pollute the Earth, so it is necessary to think about an additional source of electricity in the future. Nuclear power is one of the options. Two scenarios using different shares of nuclear power in the [...] Read more.

Conventional sources of electricity are limited and they pollute the Earth, so it is necessary to think about an additional source of electricity in the future. Nuclear power is one of the options. Two scenarios using different shares of nuclear power in the future are described in this paper. Scenario 1 describes a moderate increase in nuclear energy use in the future, but with a tendency for a larger increase over 2050. Scenario 2 describes a significant increase in nuclear energy until 2100. Both scenarios are divided into three sub-scenarios (total six) in which the use of different nuclear technologies is analyzed (conventional liquid water reactors, fast breeder reactors and molten salt reactors using thorium as nuclear fuel). In all scenarios, the phase-out of fossil fuel power plants is assumed. One part of the power system is covered by nuclear power plants, and the remaining part is covered by renewable energy power plants. After 2050, an increasing share of the electricity system will be taken over by RES power plants. Nuclear fuel stocks are also analyzed. It is calculated that currently known nuclear fuel stocks are sufficient to meet the needs in all six scenarios. The carbon dioxide emissions saved due to nuclear energy use instead of conventional energy power plants are calculated. The CO_2eq emission savings for Scenario 1 is 87.4% of the recommended emission savings under the IPCC. The CO_2eq emission savings for Scenario 2 is more than sufficient. A calculation of the economic profitability of nuclear energy use is made in relation to fossil power plants and renewable energy power plants. According to calculations, nuclear energy is profitable compared to other energy sources. Nuclear energy use is positive from all the mentioned aspects. Full article

(This article belongs to the Collection Feature Papers in Energy, Environment and Well-Being)

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21 pages, 1493 KiB

Open AccessArticle

An Assistive System for Thermal Power Plant Management

by Aleksa Stojic, Goran Kvascev and Zeljko Djurovic

Energies 2025, 18(11), 2977; https://doi.org/10.3390/en18112977 - 5 Jun 2025

Viewed by 181

Abstract

The estimation of available active power in coal-fired thermal power plant units involves considerable complexity and remains a critical task for plant operators. To avoid compromising system stability, operators often operate the thermal unit below its full capacity. To address this issue, the [...] Read more.

The estimation of available active power in coal-fired thermal power plant units involves considerable complexity and remains a critical task for plant operators. To avoid compromising system stability, operators often operate the thermal unit below its full capacity. To address this issue, the aim of this paper is to facilitate the process of estimating the maximum active electrical power by applying an assistive system based on ANFIS (Adaptive Neuro-Fuzzy Inference System), a method that combines the strengths of neural networks and fuzzy logic. Since the generated electric energy is directly linked to the amount of thermal energy produced, the analysis is focused on the boiler combustion process. It has been shown that the key factors in this process are the coal mills and their achievable capacity, as well as the calorific value of coal. Therefore, the proposed assistive system is based on the estimation of the available capacity of each active mill, which is then combined with the estimated calorific value of the coal to determine the achievable active electrical power of the unit. The conducted analysis and experiments confirm the validity of this approach. Full article

(This article belongs to the Special Issue Energy, Electrical and Power Engineering: 4th Edition)

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19 pages, 2900 KiB

Open AccessArticle

Energy Management and Edge-Driven Trading in Fractal-Structured Microgrids: A Machine Learning Approach

by Mostafa Pasandideh, Jason Kurz and Mark Apperley

Energies 2025, 18(11), 2976; https://doi.org/10.3390/en18112976 - 5 Jun 2025

Viewed by 230

Abstract

The integration of renewable energy into residential microgrids presents significant challenges due to solar generation intermittency and variability in household electricity demand. Traditional forecasting methods, reliant on historical data, fail to adapt effectively in dynamic scenarios, leading to inefficient energy management. This paper [...] Read more.

The integration of renewable energy into residential microgrids presents significant challenges due to solar generation intermittency and variability in household electricity demand. Traditional forecasting methods, reliant on historical data, fail to adapt effectively in dynamic scenarios, leading to inefficient energy management. This paper introduces a novel adaptive energy management framework that integrates streaming machine learning (SML) with a hierarchical fractal microgrid architecture to deliver precise real-time electricity demand forecasts for a residential community. Leveraging incremental learning capabilities, the proposed model continuously updates, achieving robust predictive performance with mean absolute errors (MAE) across individual households and the community of less than 10% of typical hourly consumption values. Three battery-sizing scenarios are analytically evaluated: centralised battery, uniformly distributed batteries, and a hybrid model of uniformly distributed batteries plus an optimised central battery. Predictive adaptive management significantly reduced cumulative grid usage compared to traditional methods, with a 20% reduction in energy deficit events, and optimised battery cycling frequency extending battery lifecycle. Furthermore, the adaptive framework conceptually aligns with digital twin methodologies, facilitating real-time operational adjustments. The findings provide critical insights into sustainable, decentralised microgrid management, emphasising improved operational efficiency, enhanced battery longevity, reduced grid dependence, and robust renewable energy utilisation. Full article

(This article belongs to the Special Issue Novel Energy Management Approaches in Microgrid Systems)

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17 pages, 3660 KiB

Open AccessArticle

Ensemble of Artificial Neural Networks for Seasonal Forecasting of Wind Speed in Eastern Canada

by Pia Leminski, Enzo Pinheiro and Taha B. M. J. Ouarda

Energies 2025, 18(11), 2975; https://doi.org/10.3390/en18112975 - 5 Jun 2025

Viewed by 250

Abstract

Efficient utilization of wind energy resources, including advances in weather and seasonal forecasting and climate projections, is imperative for the sustainable progress of wind power generation. Although temperature and precipitation data receive considerable attention in interannual variability and seasonal forecasting studies, there is [...] Read more.

Efficient utilization of wind energy resources, including advances in weather and seasonal forecasting and climate projections, is imperative for the sustainable progress of wind power generation. Although temperature and precipitation data receive considerable attention in interannual variability and seasonal forecasting studies, there is a notable gap in exploring correlations between climate indices and wind speeds. This paper proposes the use of an ensemble of artificial neural networks to forecast wind speeds based on climate oscillation indices and assesses its performance. An initial examination indicates a correlation signal between the climate indices and wind speeds of ERA5 for the selected case study in eastern Canada. Forecasts are made for the season April–May–June (AMJ) and are based on most correlated climate indices of preceding seasons. A pointwise forecast is conducted with a 20-member ensemble, which is verified by leave-on-out cross-validation. The results obtained are analyzed in terms of root mean squared error, bias, and skill score, and they show competitive performance with state-of-the-art numerical wind predictions from SEAS5, outperforming them in several regions. A relatively simple model with a single unit in the hidden layer and a regularization rate of

10^{- 2}

provides promising results, especially in areas with a higher number of indices considered. This study adds to global efforts to enable more accurate forecasting by introducing a novel approach. Full article

(This article belongs to the Special Issue New Progress in Electricity Demand Forecasting)

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19 pages, 2174 KiB

Open AccessArticle

Multi-Objective Time-Domain Coupled Feasible Region Construction Method for Virtual Power Plant Considering Global Stability

by Li Guo, Guiyuan Xue, Zheng Xu, Huixiang Li, Jiacheng Li and Xun Dou

Energies 2025, 18(11), 2974; https://doi.org/10.3390/en18112974 - 4 Jun 2025

Viewed by 232

Abstract

Constructing a new power system with renewable energy as the main component requires an in-depth exploration of the regulation potential of massive, distributed flexibility resources within distribution networks. This approach aims to enhance the grid’s balancing capabilities. Virtual Power Plants can effectively aggregate [...] Read more.

Constructing a new power system with renewable energy as the main component requires an in-depth exploration of the regulation potential of massive, distributed flexibility resources within distribution networks. This approach aims to enhance the grid’s balancing capabilities. Virtual Power Plants can effectively aggregate flexibility resources, but the massive scale and heterogeneous nature of distributed resources pose challenges in assessing the regulation capabilities of the aggregated entity. In this paper, a feasible region solution model for Virtual Power Plants is established based on the vertex search method. Furthermore, by introducing the principles of Lyapunov stability analysis, a multi-objective time–domain coupled feasible region construction method for VPPs with global stability considerations is proposed. Through case study analysis, the boundaries of the VPP’s regulation capability and the time–neighborhood feasible regions characterized by the proposed method exhibit better full-time output stability and are more aligned with practical needs. Full article

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26 pages, 4704 KiB

Open AccessArticle

Two-Layer Optimal Dispatch of Distribution Grids Considering Resilient Resources and New Energy Consumption During Cold Wave Weather

by Lu Shen, Xing Luo, Wenlu Ji, Jinxi Yuan and Chong Wang

Energies 2025, 18(11), 2973; https://doi.org/10.3390/en18112973 - 4 Jun 2025

Viewed by 166

Abstract

Within the context of global warming, the frequent occurrence of extreme weather may lead to problems, such as a sharp decrease in new energy output, insufficient system backups, and an increase in the amount of energy consumed by users, resulting in large-scale power [...] Read more.

Within the context of global warming, the frequent occurrence of extreme weather may lead to problems, such as a sharp decrease in new energy output, insufficient system backups, and an increase in the amount of energy consumed by users, resulting in large-scale power shortages within the grid for a short period of time. With the increase in the numbers of electric vehicles (EVs) and microgrids (MGs), which are resilient resources, the ability of a system to participate in demand response (DR) is further improved, which may make up for short-term power shortages. In this paper, we first propose a charging and discharging model for EVs during the onset of a cold wave, and then perform load forecasting for EVs during cold wave weather based on user behavioral characteristics. Secondly, in order to accurately portray the flexible regulation capability of microgrids with massively flexible resource access, this paper adopts the convex packet fitting expression based on MGFOR to characterize the flexible regulation capability of MGs. Then, the Conditional Value at Risk (CVaR) is used to quantify the uncertainty of wind and solar power generation, and a two-layer model with the objective of minimizing the operation cost in the upper layer and maximizing the rate of new energy consumption in the lower layer is proposed and solved using Karush–Kuhn–Tucker (KKT) conditions. Finally, the proposed method is verified through examples to ensure the economic operation of the system and improve the new energy consumption rate of the system. Full article

(This article belongs to the Special Issue Impacts of Distributed Energy Resources on Power Systems)

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17 pages, 2496 KiB

Open AccessArticle

High-Precision Experimental Data for Thermal Model Validation of Flat-Plate Hybrid Water PV/T Collectors

by Fahad Maoulida, Rabah Djedjig, Mourad Rahim, Mohamed Aboudou Kassim and Mohammed El Ganaoui

Energies 2025, 18(11), 2972; https://doi.org/10.3390/en18112972 - 4 Jun 2025

Viewed by 536

Abstract

An experimental setup was developed, incorporating a monitored DualSun^® photovoltaic–thermal (PV/T) panel and a weather station to continuously record real-time climatic conditions. This setup enables an hour-by-hour comparison between the actual performance observed under real-world conditions and the predictions generated by the [...] Read more.

An experimental setup was developed, incorporating a monitored DualSun^® photovoltaic–thermal (PV/T) panel and a weather station to continuously record real-time climatic conditions. This setup enables an hour-by-hour comparison between the actual performance observed under real-world conditions and the predictions generated by the thermal model. The generated dataset was used to evaluate a thermal model derived from the literature, comparing its predictions with measured data. The model adopts a quasi-steady-state, one-dimensional approach based on heat balance equations applied to both the photovoltaic cells and the heat transfer fluid. Conducted during the summer of 2022, the experiment provides valuable insights into the accuracy of the literature-based thermal model under summer meteorological conditions. The results show a good correlation between the experimental data and the model’s predictions. The average deviation observed for the outlet fluid temperature is 0.1 °C during the day and 1.3 °C at night. Consequently, the findings underscore the model’s effectiveness for evaluating daytime performance, while also pointing out its limitations for nighttime predictions, especially when hybrid PV/T collectors are used for applications such as nighttime free cooling. Full article

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

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20 pages, 1715 KiB

Open AccessArticle

Theoretical Performance Study of a Novel Diffusion Absorption Heat Transformer Driven by a Jet Pump

by Shikuan Wang, Zhaojie Wu, Shaoqiu Jiang, Yuncheng Li and Hongtao Gao

Energies 2025, 18(11), 2971; https://doi.org/10.3390/en18112971 - 4 Jun 2025

Viewed by 142

Abstract

A diffusion absorption heat transformer is a completely thermally driven heat upgrading technology with significant application potential in low-grade thermal energy recovery. However, existing diffusion absorption heat transformers have problems such as complex circulation processes, limited solution flow rates, and insufficient stability due [...] Read more.

A diffusion absorption heat transformer is a completely thermally driven heat upgrading technology with significant application potential in low-grade thermal energy recovery. However, existing diffusion absorption heat transformers have problems such as complex circulation processes, limited solution flow rates, and insufficient stability due to their reliance on bubble pumps. A jet pump was proposed for application in a diffusion absorption heat transformer cycle to replace the bubble pumps in the original diffusion absorption heat transformer cycle. In the novel cycle, without electricity consumption, the diffusant gas was used as the primary flow of the jet pump to transport the solution, and the diffusion generation of the refrigerant was realized in the jet pump for more efficient and stable thermal energy upgrading. The performance of the novel cycle with H₂O/LiBr/C₅H₁₀ or H₂O/HCOOK/C₅H₁₀ as working fluids was analyzed based on a constructed theoretical model validated by numerical simulation. It was found that the performance of the jet pump was sensitive to the generator temperature and the pressure difference of the cycle. Increasing the temperature of the jet pump and reducing the temperature of the absorber were conducive to improving the COP. As a potential absorbent substitute for LiBr, HCOOK also led to slightly better performance in most cases. Full article

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Energies, Volume 18, Issue 11 (June-1 2025) – 331 articles

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