Energies

19 pages, 1046 KB

Open AccessReview

Dynamic Modeling of Circulating Fluidized Bed Power Plants for Flexible Operation: Progress, Challenges and Future

by Xiannan Hu, Haowen Wu, Ruiqi Bai, Tong Wang, Tuo Zhou, Man Zhang and Hairui Yang

Energies 2026, 19(17), 3953; https://doi.org/10.3390/en19173953 (registering DOI) - 22 Aug 2026

The increasing penetration of renewable energy has significantly intensified the demand for flexible operation of thermal power plants, making dynamic simulation an essential tool for understanding transient behaviors and developing advanced operational strategies for circulating fluidized bed (CFB) power plants. This review critically [...] Read more.

The increasing penetration of renewable energy has significantly intensified the demand for flexible operation of thermal power plants, making dynamic simulation an essential tool for understanding transient behaviors and developing advanced operational strategies for circulating fluidized bed (CFB) power plants. This review critically examines the existing dynamic modeling approaches for industrial-scale CFB power plants, with particular emphasis on their applicability to flexibility studies. Existing CFB flue-gas side models are systematically classified into three categories: 3D physics-based CFD models, behavioral/data-driven models, and semi-empirical mechanistic models. Their characteristics are critically compared in terms of spatial and temporal scales, empirical dependence, model generality, computational and implementation burden, and applicability to CFB flexibility studies. Dynamic modeling of the steam–water cycle is also reviewed, showing that it has reached a relatively mature stage owing to well-established thermo-hydraulic theories and standardized modeling platforms. The current research bottleneck is therefore identified as the dynamic coupling between the flue-gas side and the steam–water cycle for integrated CFB whole-plant simulation. Based on the comparative analysis, semi-empirical mechanistic models are identified as a particularly suitable framework for industrial-scale CFB flexibility studies requiring minute-to-hour transient simulation, physical interpretability, and whole-plant coupling. Finally, future research directions are discussed, highlighting how integrated dynamic models can support CFB flexibility-enhancement technologies and the development of new-generation coal-fired power plants. Full article

(This article belongs to the Section B2: Clean Energy)

21 pages, 1205 KB

Open AccessArticle

A Levelized Comparison of Low-Load NG RCCI Combustion with Different Pilot Fuels at Constant Combustion Phasing

by Hariraja Thothadri, Kalyan Kumar Srinivasan and Sundar Rajan Krishnan

Energies 2026, 19(17), 3952; https://doi.org/10.3390/en19173952 (registering DOI) - 22 Aug 2026

Abstract

Reactivity-controlled compression ignition (RCCI) enhances engine performance while mitigating the diesel soot–NO_x tradeoff. In this work, natural gas (NG) RCCI combustion was investigated on a heavy-duty single-cylinder research engine with three different pilot fuels: diesel, an 80/20 (% v/v) [...] Read more.

Reactivity-controlled compression ignition (RCCI) enhances engine performance while mitigating the diesel soot–NO_x tradeoff. In this work, natural gas (NG) RCCI combustion was investigated on a heavy-duty single-cylinder research engine with three different pilot fuels: diesel, an 80/20 (% v/v) blend of n-butanol and diesel (80B20D), and dipropyl oxymethylene ether (P1P). The experiments were performed at a constant speed of 1339 rev/min, a fixed load (IMEP_g = 5 bar), and 1.5 bar boost pressure. Initially, NG RCCI combustion was studied under identical operating conditions, and subsequently with constant combustion phasing (CA50) for all pilot fuel–NG combinations for a levelized comparison. The results revealed that CA50 profoundly impacted the efficiency and unburned hydrocarbon (HC) emissions for all pilot fuels. Maintaining an optimal CA50 of 363 ± 1 CAD, high fuel conversion efficiencies (~40%) and HC emission reductions (~38–49%) were achieved across pilot fuels. The pilot fuel reactivity significantly affected combustion and emissions. The apparent heat release histories transformed from a two-stage to a single-stage Gaussian profile at a much-retarded start of injection (SOI~30 bTDC) for 80B20D-NG compared to diesel–NG and P1P-NG (40 bTDC), leading to significantly lower NO_x emissions. More advanced SOIs and lower NO_x emissions were possible with diesel–NG and P1P-NG compared to 80B20D-NG. Full article

(This article belongs to the Special Issue Internal Combustion Engines in the Energy Transition: Efficiency, Control, and Sustainable Fuels)

27 pages, 5980 KB

Open AccessArticle

Combustion Phasing, Performance and Emissions of a Single-Cylinder Diesel Engine with Intake Manifold Hydrogen Addition Under Varying Load and Speed

by Karlis Amatnieks, Ruslans Smigins, Tomasz Skrzek, Jonas Matijošius and Aivars Birkavs

Energies 2026, 19(17), 3951; https://doi.org/10.3390/en19173951 (registering DOI) - 22 Aug 2026

Abstract

The addition of hydrogen to diesel engines is increasingly being seen as a promising interim solution to reduce fossil fuel consumption and carbon emissions without changing the basic architecture of the compression-ignition engine. This study experimentally evaluated the effect of hydrogen addition on [...] Read more.

The addition of hydrogen to diesel engines is increasingly being seen as a promising interim solution to reduce fossil fuel consumption and carbon emissions without changing the basic architecture of the compression-ignition engine. This study experimentally evaluated the effect of hydrogen addition on the combustion, performance and emissions characteristics of a single-cylinder AVL 5402 Common Rail diesel engine when hydrogen was supplied via the intake manifold and diesel injection parameters were kept constant. The tests were performed at engine speeds of 1200, 1500, 2000 and 2500 min⁻¹ and loads of 5, 10, 15, 20 and 25 Nm, using a hydrogen mass replacement level of up to 10%. It was found that the addition of hydrogen in many modes increased the maximum cylinder pressure, accelerated the pressure rise, brought the pressure peak earlier and increased engine power, especially at higher loads and speeds. At the same time, fuel consumption decreased in all modes, and CO₂ emissions decreased by 3–22.7%. However, it was found that the addition of hydrogen usually increased NOx emissions; in some modes, it increased particulate and hydrocarbon emissions and extended the total combustion duration due to the reduced oxygen concentration and the formation of a richer mixture. The results showed that the effect of hydrogen on the operation of a diesel engine is strongly dependent on the load and speed; therefore, the benefits of its application can be achieved only under carefully coordinated operating conditions that ensure a favorable compromise between combustion intensification, fuel economy and emission control. Full article

► Show Figures

Figure 1

38 pages, 2906 KB

Open AccessReview

On the Methodological Harmonization of the Life Cycle Assessment of Woody Biomass-to-Energy Conversion Pathways—A Review

by Baibhaw Kumar and Heriberto Cabezas

Energies 2026, 19(17), 3950; https://doi.org/10.3390/en19173950 (registering DOI) - 22 Aug 2026

Abstract

Woody biomass is often promoted as a low-carbon energy source in global decarbonization efforts. However, LCA (life cycle assessment) evaluations of woody biomass-to-energy systems show very different environmental performance. Variations in technology and methodology across investigations can cause these inconsistencies. This review paper [...] Read more.

Woody biomass is often promoted as a low-carbon energy source in global decarbonization efforts. However, LCA (life cycle assessment) evaluations of woody biomass-to-energy systems show very different environmental performance. Variations in technology and methodology across investigations can cause these inconsistencies. This review paper analyzes methodologies of LCAs of woody biomass conversion routes such as combustion, combined heat and power, gasification, pyrolysis, torrefaction-assisted systems, and new bioenergy with carbon capture configurations. A systematic literature review was conducted using Scopus, SpringerLink, and ScienceDirect, identifying 4272 records, of which 98 studies were retained for detailed analysis following the application of defined inclusion and exclusion criteria. Functional unit selection, from biomass mass per unit to power or heat per unit, is highly variable, affecting comparability. Forest carbon stock fluctuations, infrastructure, and end-of-life treatment are inconsistently included in cradle-to-grave system boundaries. Static GWP100 methods are often used in biogenic carbon removal without considering temporal carbon dynamics. The importance of pretreatment steps like drying, pelletizing, and torrefaction cannot be overstated, even though they have a direct impact on the quality of the fuel, the efficiency of transportation, and the effectiveness of the conversion process downstream. The large range of stated emission levels for comparable technologies is further influenced by logistics assumptions, plant scale, and allocation mechanisms in cogeneration systems. The review synthesizes these methodological differences and proposes a harmonization methodology to increase woody biomass LCA transparency and comparability. By identifying important sources of outcome variability, this study helps policymakers, project developers, and industry stakeholders evaluate biomass energy investments and bring clarity to environmental decisions. Full article

(This article belongs to the Special Issue Integrated Techno‑Economic and Life Cycle Assessment of Energy Carriers and Systems)

► Show Figures

Figure 1

34 pages, 3942 KB

Open AccessArticle

Perfect-Foresight Flow-Rate Control of a Photovoltaic–Thermal Collector for Thermochemical Storage: An Exergy Upper Bound

by Suratsavadee Koonlaboon Korkua, Krit Funsian, Choosak Rittiphet, Mohammad Faridun Naim Tajuddin, Santanu Kumar Dash and Kamon Thinsurat

Energies 2026, 19(17), 3949; https://doi.org/10.3390/en19173949 (registering DOI) - 22 Aug 2026

Abstract

Photovoltaic–thermal (PVT) collectors coupled to thermochemical energy storage (TCES) can turn intermittent low-grade solar heat into a dispatchable service, but solar intermittency poses a closed-loop control problem. A companion study established the feedback-only lower bound: a 937 kJ accumulated exergy-delivery-deficit benchmark under optimally [...] Read more.

Photovoltaic–thermal (PVT) collectors coupled to thermochemical energy storage (TCES) can turn intermittent low-grade solar heat into a dispatchable service, but solar intermittency poses a closed-loop control problem. A companion study established the feedback-only lower bound: a 937 kJ accumulated exergy-delivery-deficit benchmark under optimally tuned proportional–integral–derivative (PID) flow control. The corresponding upper bound is quantified here by means of a deliberately idealised search-based predictive controller that, at each 10 s step, enumerates 51 candidate pump rates, predicts the reactor-inlet temperature by a single forward-Euler step, and is granted perfect future irradiance. On the experimentally validated shared plant (matched to the companion baseline), against an optimally tuned PID, the perfect-foresight advantage is marginal: +0.96% daily exergy on synthetic days and +0.07–0.24% on two measured Walailak University monsoon days, all controllers tracking within 6–13 K on the measured days. Under tropical-monsoon irradiance, the 95 °C desorption setpoint is rarely sustained, so the delivered exergy is nearly controller-independent: the perfect-foresight upper bound lies just above the feedback-only lower bound, and together the two results bracket the exergy envelope available to any flow-rate controller of this system. A horizon sweep localises the bottleneck to internal-model fidelity, not anticipation depth. The eight-node plant is validated against measured module temperature (root-mean-square error 3.5 °C, coefficient of determination R² = 0.89) and a copper-tube PVT prototype (1.5 °C; peak hot water up to 79 °C). The central contribution is therefore a rigorously defined, experimentally grounded upper bound showing that, at this scale and latitude, deployability rather than anticipation is the effective design lever. Full article

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

39 pages, 17897 KB

Open AccessArticle

Multi-Objective Optimization of a Hydrogen-Coupled Integrated Energy System with Cascade Waste-Heat Utilization for Low-Carbon Industrial Parks

by Hongyue Deng, Huizhen Wan, Xu Li, Jia Xu, Chuanchao Zhao, Jiying Liu and Bo Gao

Energies 2026, 19(17), 3948; https://doi.org/10.3390/en19173948 (registering DOI) - 22 Aug 2026

Abstract

Continuous carbon anode roasting in industrial parks requires a stable high-temperature heat supply and remains highly dependent on grid electricity and natural gas. However, existing energy-system studies rarely coordinate hydrogen production and storage, volumetric hydrogen blending, and temperature-graded waste-heat recovery under continuous production [...] Read more.

Continuous carbon anode roasting in industrial parks requires a stable high-temperature heat supply and remains highly dependent on grid electricity and natural gas. However, existing energy-system studies rarely coordinate hydrogen production and storage, volumetric hydrogen blending, and temperature-graded waste-heat recovery under continuous production constraints. To address this gap, this study proposes an electricity–heat–gas–hydrogen integrated energy system for carbon anode industrial parks and develops a 24 h multi-objective scheduling model. The model coordinates heat demands at different temperature levels with hourly electricity and hydrogen flows, using surplus photovoltaic power to produce hydrogen for later high-load periods. The selected scheme achieves a daily volumetric hydrogen-blending ratio of 10.79%, with an operating cost of 82,985.75 CNY and carbon emissions of 54,371.53 kg. Relative to an otherwise equivalent non-hydrogen configuration, hydrogen coupling provides additional reductions of 7.2% in operating cost and 2.3% in carbon emissions. Compared with a basic conventional configuration, operating cost and carbon emissions decrease by 27.9% and 26.0%, respectively. Cascade recovery also increases the daily waste-heat utilization rate by approximately 30 percentage points. These results show that the proposed scheduling framework can coordinate hydrogen utilization and graded waste-heat recovery while maintaining continuous carbon anode production. Full article

(This article belongs to the Special Issue Next-Generation Thermo-Electro-Hydrogen Solutions: Hybrid Intelligence for Integrated Energy Systems)

24 pages, 1197 KB

Open AccessArticle

Techno-Economic Comparison of Data Center Cooling Using Magnetic Bearing Chillers and Aquifer Thermal Energy Storage

by Apurva Malpure, Andrew Stumpf, Upasana Pandey, Yu-Feng Lin and Craig Bradshaw

Energies 2026, 19(17), 3947; https://doi.org/10.3390/en19173947 (registering DOI) - 22 Aug 2026

Abstract

Data centers are large and rapidly growing electricity consumers, and cooling systems account for a substantial share of their energy demand. A key contribution of this study is a climate-sensitive, hourly techno-economic comparison of three data-center cooling configurations under consistent operating assumptions: a [...] Read more.

Data centers are large and rapidly growing electricity consumers, and cooling systems account for a substantial share of their energy demand. A key contribution of this study is a climate-sensitive, hourly techno-economic comparison of three data-center cooling configurations under consistent operating assumptions: a conventional water-cooled centrifugal chiller baseline, a magnetic bearing chiller (MBC) system, and an MBC system integrated with aquifer thermal energy storage (ATES). The comparison is performed for Phoenix, Arizona, and Fairbanks, Alaska, which represent substantially different cooling climates in the U.S. Hourly simulations use identical information technology (IT) load profiles, identical aggregate installed chiller capacity represented by two 4058 kW chiller units, common water-side economizer controls, and site-specific weather and electricity tariffs. Results show that the MBC system reduces annual cooling-system electricity consumption from 1169.4 to 957.4 MWh in Phoenix (18.1%) and from 361.6 to 319.4 MWh in Fairbanks (11.7%). Peak cooling-system electrical demand decreases by 119.4 kW in Phoenix and 71.6 kW in Fairbanks. Relative to the centrifugal baseline, the MBC case gives a 5.8-year simple payback in Phoenix but is not economically attractive in Fairbanks under the assumed tariff. The MBC-only case gives the lowest annual cooling electricity use in both climates. The MBC+ATES case is treated only as a screening-level, discharge-assisted cold-storage scenario rather than a full techno-economic assessment of seasonal ATES, and no site-specific hydrogeological feasibility assessment is performed. Under the assumed O&M cost structure, MBC+ATES gives a higher discounted value of savings than MBC-only, but this economic result is not caused by additional cooling-electricity savings relative to MBC-only. The MBC+ATES case also has a longer payback period because of its higher capital cost. These results show that the value of advanced cooling configurations depends on climate, free-cooling availability, electricity pricing, storage assumptions, and economic assumptions within the modeling framework considered in this study. Full article

(This article belongs to the Special Issue Technological and Economical Aspects of Geothermal Power Plants and Heat Pumps)

22 pages, 1629 KB

Open AccessArticle

Anaerobic Co-Digestion of Gerbera Flower Residues, Non-Marketable Apples and Pig Slurry: Biochemical Methane Potential, Synergistic Effects and Kinetic Modelling

by Miguel Nogueira, Mariana R. Popich, Carla C. Sousa and Rita Fragoso

Energies 2026, 19(17), 3946; https://doi.org/10.3390/en19173946 (registering DOI) - 22 Aug 2026

Abstract

Floricultural residues represent a substantial and largely unvalorised organic stream in Europe, yet their anaerobic digestion has received limited attention. This study benchmarked the biochemical methane potential and degradation kinetics of Gerbera spp. flower residues (FRs), non-marketable apples (AW) and pig slurry (PS) [...] Read more.

Floricultural residues represent a substantial and largely unvalorised organic stream in Europe, yet their anaerobic digestion has received limited attention. This study benchmarked the biochemical methane potential and degradation kinetics of Gerbera spp. flower residues (FRs), non-marketable apples (AW) and pig slurry (PS) under mesophilic batch conditions in mono-digestion and in five co-digestion mixtures. Mono-digestion yielded 362.5 ± 4.1 mL_CH4·g_VS⁻¹ for FR, constrained by lignocellulosic recalcitrance and a high extractive content, and 320.9 ± 39.2 mL_CH4·g_VS⁻¹ for AW, whose dispersion reflects the heterogeneity of non-marketable fruit; PS yielded 437.7 ± 2.6 mL_CH4·g_VS⁻¹ and supplied the alkalinity that both plant residues lacked. The highest yield was obtained for the ternary mixture COAD_5 (0.30 PS, 0.45 AW, 0.25 FR on a VS basis), reaching 472.8 ± 8.6 mL_CH4·g_VS⁻¹. This corresponds to a 29.1% increase over the theoretical additive potential (synergy index: 1.29 ± 0.07) and a gain of 8.0% over pig slurry mono-digestion. Once uncertainties were propagated, demonstrable synergy was confined to COAD_5 and to the binary mixture COAD_4. All treatments remained stable, with final pH between 7.40 and 7.86 and VFA-to-alkalinity ratios below 0.11. Kinetic modelling distinguished two regimes: first-order behaviour for the hydrolysis-limited and slurry-dominated substrates, and Modified Gompertz behaviour for the sugar-rich mixtures. Applied to the project site, these yields correspond to a preliminary gross scenario of the order of 481,000 Nm³ CH₄·yr⁻¹. The results establish that floricultural residues can be integrated into livestock-based anaerobic digestion without compromising process stability. Full article

(This article belongs to the Special Issue Environmental Biotechnologies for Bioenergy from Waste Valorization)

► Show Figures

Figure 1

14 pages, 8066 KB

Open AccessArticle

Fast Adaptive Reactive-Power Compensation Control for Renewable Power Plants Considering Dynamic Active-Power–Voltage Coupling

by Jiacheng Li, Chang Ye, Menghan Xiao, Xun Xu, Yuqi Ao, Qixiang Huang and Yuwei Gui

Energies 2026, 19(17), 3945; https://doi.org/10.3390/en19173945 (registering DOI) - 22 Aug 2026

Abstract

Renewable power plants connected to low-system-strength grids are increasingly dominated by inverter-based resources (IBRs). Their point of common coupling (PCC) voltage is therefore shaped not only by reactive-power support but also by active-power ramps, network impedance, short-circuit capacity, and converter limits. Conventional Q-V [...] Read more.

Renewable power plants connected to low-system-strength grids are increasingly dominated by inverter-based resources (IBRs). Their point of common coupling (PCC) voltage is therefore shaped not only by reactive-power support but also by active-power ramps, network impedance, short-circuit capacity, and converter limits. Conventional Q-V droop control, fixed power-factor control, Volt/VAR control, and fixed active-power/reactive-power (P/Q) decoupling schemes often absorb active-power excursions into the voltage error, which can drive excessive reactive-power injection during fault clearing, post-fault power recovery, and phase-angle disturbances. Here, an active-power–voltage-coupling-aware reactive-power compensation (APVQ-RC) method is proposed for plant-level voltage control. The method estimates local P-V and Q-V voltage sensitivities online, reconstructs an effective voltage error, and produces a capacity-constrained reactive-power reference through smooth coupling activation. The reduced-order evaluation includes estimator conditioning, excitation screening, sensitivity-estimation error and empirical 95% estimator-error intervals, sensitivity to the smoothing factor and window length, measurement noise, converter capability saturation, and computational timing. Under P-V-coupled transients, APVQ-RC reduces voltage overshoot and reactive-power compensation energy while retaining Q-V-like support during voltage-sag-dominated events. Compared with the best scanned fixed P/Q baseline, it reduces overshoot, reactive-power compensation energy, and reactive-power peak by 42.03%, 60.35%, and 8.90%, respectively; the representative single-step calculation time is 0.0188 ms within a 1 ms control cycle. These results indicate millisecond-scale plant-level feasibility within the reduced model, while electromagnetic-transient, hardware-in-the-loop, and field validation remain necessary before deployment. Full article

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

► Show Figures

Figure 1

27 pages, 2126 KB

Open AccessArticle

Process Stability, Methane Yield, and Microbial Community Structure in Two-Stage Co-Digestion of Plant and Animal Substrates Using Real-World Feedstock from an Agricultural Biogas Plant

by Daria Sławczyk, Beata Bień, Przemysław Liczbiński, Estera Baor and Anna Grobelak

Energies 2026, 19(17), 3944; https://doi.org/10.3390/en19173944 (registering DOI) - 22 Aug 2026

Abstract

In the context of the global shift toward sustainable energy systems and circular economy strategies, anaerobic digestion is a well-established biotechnology for the valorisation of organic residues, the production of biogas as a renewable energy carrier, and the generation of nutrient-rich digestate. This [...] Read more.

In the context of the global shift toward sustainable energy systems and circular economy strategies, anaerobic digestion is a well-established biotechnology for the valorisation of organic residues, the production of biogas as a renewable energy carrier, and the generation of nutrient-rich digestate. This study aimed to evaluate the stability and methane yield of a two-stage co-digestion process using a substrate mixture developed based on the actual feedstock composition of a full-scale agricultural biogas plant. The daily feed mixture consisted of maize silage (8.2%), sugar beet pulp (4.9%), cellulose pulp (6.6%), distillery stillage (38.6%), corn syrup (6.4%), cattle slurry (22.5%) and sterilised animal by-products (12.8%). Digestate was recirculated separately as part of the reactor operation. Laboratory-scale experiments were conducted in a two-stage anaerobic digestion system operated at 42 °C and 50 °C. The physicochemical properties of the substrates and digestate were determined, biogas quantity and composition were monitored, and the microbial community structure was assessed using 16S rRNA gene amplicon sequencing. The process remained stable throughout the experimental period, with pH values ranging from 8.23 to 8.53, alkalinity between 2600 and 2940 mg CaCO₃/dm³, and a VFAs/alkalinity ratio of 0.17–0.93. Despite ammonium nitrogen concentrations reaching 4346 mg N-NH₄⁺/L, no clear concurrent reduction in gas or methane production was observed. Methane accounted for approximately 70–80% of the biogas produced. The overall specific methane yield reached 346.4 NL CH₄ kg⁻¹ VS added. 16S rRNA gene amplicon sequencing revealed a diverse microbial community containing taxa previously associated with hydrolysis, fermentation and syntrophic interactions, including Proteiniphilum and Syntrophaceticus. The results demonstrate stable process performance and methane production in this site-specific laboratory-scale case study based on the feedstock composition and process configuration of a full-scale agricultural biogas plant. Full article

(This article belongs to the Special Issue Waste to Bioenergy: New Technologies and Applications)

► Show Figures

Figure 1

33 pages, 2732 KB

Open AccessArticle

AC-Screened Robust Restoration of Weather-Stressed PV–Storage–EV Distribution Networks via Graph Learning and Multi-Agent Control

by Jicheng Wei, Sipei Sun, Liang Zhang, Yu Wang, Liang Feng and Xueshen Zhao

Energies 2026, 19(17), 3943; https://doi.org/10.3390/en19173943 (registering DOI) - 22 Aug 2026

Abstract

Extreme weather couples spatially correlated component damage with photovoltaic (PV) derating, changing electric-vehicle (EV) demand, repair delay, and time-varying network topology. This paper develops a coordinated restoration architecture for multi-area feeders containing PV, battery energy storage, and charging stations. Its weather-facing layer constructs [...] Read more.

Extreme weather couples spatially correlated component damage with photovoltaic (PV) derating, changing electric-vehicle (EV) demand, repair delay, and time-varying network topology. This paper develops a coordinated restoration architecture for multi-area feeders containing PV, battery energy storage, and charging stations. Its weather-facing layer constructs joint outage-risk, renewable-error, charging-demand, and voltage-vulnerability descriptors. Those descriptors parameterize a two-stage mixed-integer second-order-cone program with a finite-support optimal-transport ambiguity set that remains well defined for discontinuous mixed-integer recourse. Regional actor–critic agents propose five-minute corrections around the hourly robust schedule; constrained projection, non-linear AC power-flow screening, emergency fallback, and margin-tightened re-optimization retain the authority to accept or reject each proposal. The evaluation uses public 33-node and 123-node feeders together with synthetic 240-node and 850-node stress networks. A pre-fit manifest allocates 240 records to training, 80 to validation, and 320 to final testing, while aggregate operational outcomes cover 50 random streams. Within this controlled benchmark, accepted schedules restore 93.6% of critical-load energy (SD 2.1 percentage points), serve 96.7% of total demand (SD 1.8 percentage points), retain 82–86% of EV service across hazard classes, and reduce the modeled 24 h objective by 25.8% relative to deterministic dispatch. The full pipeline records two to four candidate-stage voltage-limit events by hazard, and 4.9% of candidates undergo tightened re-optimization before accepted schedules reach zero reported AC voltage-limit violations. Between-method comparisons are descriptive and unpaired; the larger synthetic cases are structural stress tests rather than feeder-transfer tests. Full article

(This article belongs to the Topic Toward Smart and Sustainable Energy Systems Enabled by Artificial Intelligence, Optimization, and Resilience)

► Show Figures

Figure 1

15 pages, 2042 KB

Open AccessArticle

Blasingame Production Decline Model of CO₂ Miscible Flooding in the Tight Oil Reservoirs with Stress Sensitivity

by Jianchao Shi, Yuzhe Shi, Wenhao Duan, Peng Song, Xiaodong Chen, Yizhuo Yang, Handan Zhang, Xinjiu Rao, Jing Ma and Xinwei Liao

Energies 2026, 19(17), 3942; https://doi.org/10.3390/en19173942 (registering DOI) - 22 Aug 2026

Abstract

For tight oil reservoirs, analyzing the characteristics of the Blasingame production decline curves of production wells under CO₂ flooding can effectively evaluate the development performance of CO₂ miscible flooding. However, tight oil reservoirs exhibit stress-sensitive effects, which degrade the reliability of [...] Read more.

For tight oil reservoirs, analyzing the characteristics of the Blasingame production decline curves of production wells under CO₂ flooding can effectively evaluate the development performance of CO₂ miscible flooding. However, tight oil reservoirs exhibit stress-sensitive effects, which degrade the reliability of interpretation results. Currently, there are few production decline analysis models for CO₂ miscible flooding that consider stress sensitivity. Based on the flow theory of three-region composite reservoirs, a physical model for CO₂ miscible flooding considering stress-sensitive effects was designed, and a mathematical model was established to obtain the characteristics of the Blasingame curve. The results show that the production decline analysis model for CO₂ miscible flooding is divided into six flow stages; the stress-sensitive effect causes the entire Blasingame curve to shift downwards; the mobility ratio and storativity ratio have a significant impact on the entire flow process of CO₂ miscible flooding. The proposed production decline analysis model provides a potential method for estimating the effective front radii of the crude oil region and the transition region, together with other equivalent flow parameters, from production data. Full article

(This article belongs to the Special Issue Advances in Carbon Dioxide (CO₂) Enhanced Oil Recovery (EOR) and Carbon Capture and Storage (CCS))

► Show Figures

Figure 1

68 pages, 24222 KB

Open AccessArticle

Collaborative Optimization of Numerical Empowerment-Driven Campus IES Public Services Considering Elderly-Oriented Renovation

by Xiao-Jing Zhao, Xiao Du, Rui-Nan Zha, Ze-Qi Li and Zhi-Feng Liu

Energies 2026, 19(16), 3941; https://doi.org/10.3390/en19163941 - 21 Aug 2026

Abstract

With the continued advancement of low-carbon campus transformation and the increasing penetration of renewable energy, campus integrated energy systems have become key infrastructure for green campus development. However, the highly random nature of student behavior causes dynamic fluctuations in electricity, heating, and cooling [...] Read more.

With the continued advancement of low-carbon campus transformation and the increasing penetration of renewable energy, campus integrated energy systems have become key infrastructure for green campus development. However, the highly random nature of student behavior causes dynamic fluctuations in electricity, heating, and cooling loads, creating major challenges for real-time supply-demand balance and economic system scheduling. To address this problem, this paper takes student behavior uncertainty as the core disturbance factor and proposes a flexible architecture-driven autonomous adaptation and multi-energy complementary optimization strategy. A closed-loop operation paradigm of signal–response–complementarity–regulation is established, in which dynamic electricity price signals, comfort-oriented guidance, and campus functional energy-zone division are combined to form a multi-level autonomous response chain. To improve solution efficiency, the electromagnetic wave propagation algorithm is further enhanced, and a Multi-Objective Electromagnetic Wave Propagation Algorithm (MEMWPA) is developed. Wave-impedance matching and energy-flux-density feedback mechanisms are introduced to strengthen convergence performance in complex multi-objective optimization problems. Comparative case studies show that the proposed strategy can effectively smooth the net load curve, reduce the campus peak load by 26.73%, and increase the load factor by 14.533 percentage points, thereby improving both operational flexibility and energy efficiency. Full article

(This article belongs to the Special Issue Next-Generation Smart Energy Systems for Sustainable and Decarbonized Energy Infrastructures)

► Show Figures

Figure 1

34 pages, 2711 KB

Open AccessArticle

A Modified 2-DoF Wave Buoy with an Embedded Tunable Magnetic-Spring Electromagnetic Energy Harvester: Concept, Dynamic Modeling and Numerical Analysis

by Joanna Bijak and Tomasz Trawiński

Energies 2026, 19(16), 3940; https://doi.org/10.3390/en19163940 - 21 Aug 2026

Abstract

This paper presents a modified two-degree-of-freedom wave buoy with an embedded tunable magnetic-spring electromagnetic energy harvester. The proposed device is modeled as a branched kinematic chain composed of a rotational–rotational buoy mechanism and a rotational–prismatic harvester branch sharing the first revolute joint. Two [...] Read more.

This paper presents a modified two-degree-of-freedom wave buoy with an embedded tunable magnetic-spring electromagnetic energy harvester. The proposed device is modeled as a branched kinematic chain composed of a rotational–rotational buoy mechanism and a rotational–prismatic harvester branch sharing the first revolute joint. Two harvester orientations are considered and compared. The mathematical model is formulated using homogeneous transformations, velocity Jacobians and Lagrange equations. Particular attention is paid to the structure of the inertia matrix and to the way in which its inverse transmits generalized forces between the rotational coordinates and the translational motion of the moving magnet. The model is implemented in MATLAB/Simulink R2024b and evaluated under free-response, regular-wave, and bidirectional frequency-sweep excitation scenarios. Under regular-wave excitation, Config. 1 produces approximately 19.3 and 2.98 times greater average load power than Config. 2 for moving-assembly masses of 5 g and 268 g, respectively. The frequency-sweep results show that the preferred harvester orientation depends on the excitation frequency and moving-assembly mass. No resolved sweep-direction dependence is observed for 5 g, whereas for 268 g the identified hysteresis intervals are approximately 0.53 rad/s for Config. 2 and 0.64 rad/s for Config. 1. These results provide design guidelines for selecting the harvester orientation and moving mass in compact wave-excited buoy systems. Full article

► Show Figures

Graphical abstract

24 pages, 1857 KB

Open AccessArticle

An Enhanced Lightweight YOLOv11 Algorithm for Real-Time Detection of High-Voltage Line Insulators

by Abdil Karakan

Energies 2026, 19(16), 3939; https://doi.org/10.3390/en19163939 - 21 Aug 2026

Abstract

UAV-based insulator detection is challenging because insulators often occupy small regions of aerial images and appear against complex backgrounds, while subtle local features may be lost during feature extraction and down-sampling. Moreover, practical UAV and edge-device applications require efficient models with limited computational [...] Read more.

UAV-based insulator detection is challenging because insulators often occupy small regions of aerial images and appear against complex backgrounds, while subtle local features may be lost during feature extraction and down-sampling. Moreover, practical UAV and edge-device applications require efficient models with limited computational and memory demands. This study proposes an optimized lightweight YOLOv11n model for high-voltage transmission-line insulator detection. The architecture integrates C3k2MBNV2 to reduce model complexity, SCDown to preserve spatial information during down-sampling, and C3k2WTDC to enhance multi-frequency feature representation. A diverse dataset containing 5750 insulator images acquired under different environmental conditions, viewing angles, and backgrounds was used for evaluation. Experimental results show that the proposed model reduces the parameter count from 6.20 M to 3.26 M and computational complexity from 20.5 to 12.7 GFLOPs, corresponding to reductions of 47.4% and 38.0%, respectively. Meanwhile, precision increases from 91.3% to 93.8%, recall from 73.4% to 75.2%, mAP50 from 71.2% to 73.9%, and mAP50–95 from 65.6% to 67.3%. These results demonstrate an improved accuracy–efficiency trade-off, supporting real-time insulator detection in resource-constrained UAV and edge-device applications. Full article

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

37 pages, 2528 KB

Open AccessArticle

Power and Fatigue–Load Assessment of Static Wake Steering in a Floating Wind Farm with 15 MW Turbines

by Majid Ebrahimi, Federico Bellini, Alessandro Fontanella, Sara Muggiasca and Marco Belloli

Energies 2026, 19(16), 3938; https://doi.org/10.3390/en19163938 - 21 Aug 2026

Abstract

Static wake steering can increase wind-farm power production, but its application to floating offshore wind farms requires assessment of the coupled wake, platform, structural, and station-keeping response. This study evaluates whether power-maximizing static yaw setpoints identified using the steady, control-oriented FLORIS model retain [...] Read more.

Static wake steering can increase wind-farm power production, but its application to floating offshore wind farms requires assessment of the coupled wake, platform, structural, and station-keeping response. This study evaluates whether power-maximizing static yaw setpoints identified using the steady, control-oriented FLORIS model retain their benefit when transferred without re-optimization to a coupled FAST.Farm floating wind-farm model. The reference farm comprises four IEA Wind 15 MW turbines mounted on VolturnUS-S semi-submersible platforms. Greedy and static wake-steering operations are compared at three below-rated wind speeds, three sea states, and five matched turbulent-inflow realizations, resulting in 90 farm-level FAST.Farm simulations. Wake behavior is characterized through wake-center deflection, meandering, and velocity-deficit profiles, while turbine and mooring fatigue responses are evaluated using paired damage-equivalent-load statistics. Static wake steering increases mean farm power under all nine investigated wind–wave conditions. The gains are approximately 5.1–

5.2 %

at

7 m s^{- 1}

,

5.0

–

5.1 %

at

8 m s^{- 1}

, and

4.0

–

4.2 %

at

9 m s^{- 1}

, with all paired

95 %

confidence intervals remaining above zero. The gain results from a power redistribution in which the intentionally yawed upstream turbine incurs a local loss that is exceeded by the combined recovery of the downstream turbines. The fatigue response is strongly component- and turbine-dependent. The paired farm-mean blade-root DEL decreases by

0.82

–

2.24 %

, whereas the tower-base DEL increases by

0.76

–

2.78 %

, and the FairTen1 response generally increases by

0.88

–

2.92 %

. The farm-mean yaw-bearing response is mixed, ranging from a

1.15 %

reduction to a

4.32 %

increase. Turbine-level analysis reveals larger localized penalties, reaching approximately

10.4 %

for the yaw-bearing DEL and

12.8 %

for FairTen1. Spectral analysis associates the yaw-bearing response with yaw-induced aerodynamic and structural excitation, while the tower-base response is strongly influenced by low-frequency wave–platform dynamics. A complementary FLORIS sensitivity analysis demonstrates that the optimized aerodynamic benefit depends strongly on wind direction, spacing, wind speed, and turbulence intensity. For a Tampen-derived 11-turbine layout, resource weighting over the modeled 4–

13 m s^{- 1}

interval produces an annual energy-contribution increase of

3.653 GWh {year}^{- 1}

, or

0.921 %

. These results provide numerical evidence that static wake steering can retain a positive power benefit in a coupled floating wind-farm environment, but controller assessment must include turbine- and component-specific dynamic loads rather than farm power alone. Full article

(This article belongs to the Special Issue Latest Challenges in Modelling and Control of Wind Turbines: Aerodynamics, Structural Dynamics, Hydrodynamics and Inflow Effects)

30 pages, 15637 KB

Open AccessArticle

Segmented Finite Line Source Analysis of Mid-Deep UBHE with Geothermal Gradient and Stratification

by Zhigang Shi, Zheng Xu, Lin Zhang, Shiwei Xia, Chaozheng Wang, Jin Tu and Peng He

Energies 2026, 19(16), 3937; https://doi.org/10.3390/en19163937 - 21 Aug 2026

Abstract

This study develops an analytical model for a mid-deep U-shaped borehole heat exchanger (UBHE) based on the segmented finite line source method, integrating geothermal gradient, five-layer geological stratification, and groundwater seepage within a unified framework. The injection, horizontal, and extraction sections are represented [...] Read more.

This study develops an analytical model for a mid-deep U-shaped borehole heat exchanger (UBHE) based on the segmented finite line source method, integrating geothermal gradient, five-layer geological stratification, and groundwater seepage within a unified framework. The injection, horizontal, and extraction sections are represented by independent local coordinates and coupled through the position- and time-dependent unit-length heat-transfer rate

q_{l} (s_{n}, t)

. Validation against the benchmark results of Bao et al. yields a mean absolute error of 0.87 °C and a mean relative error of 1.6%. Numerical-independence tests identify a 1 h time step and 100/50 m vertical/horizontal segment lengths as the adopted settings, and the iterative residual reaches 10⁻⁴ °C within eight iterations for the representative case. In a homogeneous, no-seepage limiting case, the model agrees with the classical finite line-source solution with an MAE of 0.012 °C and a maximum relative-error magnitude of 0.41%. The extraction-well fluid-temperature peak occurs at 600–800 m depth, whereas the local heat-transfer direction changes near 1600 m. For the investigated 2500–650–2500 m geometry, the highest cycle-averaged outlet temperature is obtained at an insulation length of 1600 m. Sensitivity analyses further quantify the effects of seepage velocity, equivalent thermal conductivity, geothermal gradient, and the validation insulation-length assumption. Full article

► Show Figures

Figure 1

50 pages, 5585 KB

Open AccessArticle

An Integrated Stochastic Decision-Support Framework: Hybrid Commercialization of Marginal Dry Gas Wells

by Juan Rogelio Rodríguez-Velázquez, Omar Gustavo Alvarado-Mancilla, Eduardo Morales-Sánchez, Jonás Velasco-Álvarez, Rubén Vázquez-Medina and Daniel Aguilar-Torres

Energies 2026, 19(16), 3936; https://doi.org/10.3390/en19163936 - 21 Aug 2026

Abstract

Natural gas production from mature fields is progressively shifting toward low-rate wells operating near their economic limit, creating challenges for long-term asset management. This study proposes an integrated stochastic decision-support framework combining Arps decline curve analysis, a calibrated Schwartz Type-I mean-reverting jump-diffusion model, [...] Read more.

Natural gas production from mature fields is progressively shifting toward low-rate wells operating near their economic limit, creating challenges for long-term asset management. This study proposes an integrated stochastic decision-support framework combining Arps decline curve analysis, a calibrated Schwartz Type-I mean-reverting jump-diffusion model, Monte Carlo simulation, and Bellman dynamic programming to optimize marginal dry gas well management. The framework evaluates pipeline commercialization and a hybrid strategy integrating on-site electricity generation, while incorporating monetized environmental externalities associated with CO₂ emissions from gas combustion and potential post-abandonment CH₄ emissions. Application to the Mareógrafo 100 well in Mexico shows that the environmentally adjusted Bellman policy yields a mean NPV of USD 34.84 thousand, exceeding the comparable pipeline-only and hybrid strategies. Internalizing environmental costs reduces the mean optimal NPV by 46.6% relative to the economic-only formulation, while the mean abandonment time is approximately 200 days. Sensitivity analysis identifies electricity price, natural gas price, and pipeline distance as the dominant profitability drivers. The proposed framework provides a transferable methodology for jointly evaluating commercialization, environmental externalities, and abandonment decisions in mature dry gas fields under uncertainty. Full article

► Show Figures

Figure 1

27 pages, 1410 KB

Open AccessArticle

From Prediction to Decision: A Unified Dual-Stage LLM-Driven Framework for Intelligent Energy Management with Unstructured Information

by Yong Chen, Guo Chen and Fang Yao

Energies 2026, 19(16), 3935; https://doi.org/10.3390/en19163935 - 21 Aug 2026

Abstract

Modern energy systems, including those supporting transportation electrification, are increasingly exposed to volatile market conditions and external events. Effective decision-making therefore requires the integration of structured operational data with unstructured contextual information. Existing studies on Large Language Model (LLM)-assisted energy systems have mainly [...] Read more.

Modern energy systems, including those supporting transportation electrification, are increasingly exposed to volatile market conditions and external events. Effective decision-making therefore requires the integration of structured operational data with unstructured contextual information. Existing studies on Large Language Model (LLM)-assisted energy systems have mainly applied LLMs to individual tasks such as forecasting, scheduling, or decision support, while forecasting and control are typically treated separately. As a result, semantic information extracted from external events is not consistently propagated from market prediction to operational decision-making. This paper proposes a unified dual-stage framework in which the LLM functions as a shared semantic information processor, converting raw event data into structured representations used by both forecasting and control modules. In the forecasting stage, these representations improve price prediction under non-stationary conditions. In the control stage, the same information provides an event-aware contextual action prior for reinforcement learning-based energy management. This design allows external event information to inform both future-state estimation and subsequent control decisions, establishing a consistent connection between prediction and decision-making. The framework is evaluated using real-world electricity market data and a battery energy management environment. The results show that the proposed framework achieves the highest average cumulative reward among the evaluated methods while maintaining greater robustness than the forecasting-only LLM configuration. Overall, this work demonstrates the benefit of consistently propagating structured semantic information across forecasting and control and provides a viable approach to event-aware intelligent energy management, with potential extensions to multi-energy transportation systems and electrified mobility applications. Full article

(This article belongs to the Topic Intelligent Modeling, Predictive Control, and Decision-Making for Multi-Energy Transportation Systems)

Journal Description

Energies

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI