Search Results (4,214)

Phenolic aerogels, owing to their low density, high char yield, large specific surface area, and well-defined three-dimensional topological networks, hold considerable promise for applications in extreme thermal protection and multifunctional material systems. The sol–gel process, a cornerstone methodology for constructing the three-dimensional nanoporous architecture of these materials, critically governs the resulting microstructural topology and macroscopic performance through its reaction kinetics, phase-separation behavior, and drying dynamics. This review systematically surveys recent advances in the sol–gel synthesis of phenolic aerogels, focusing on the polycondensation mechanisms operative under acidic and basic catalytic conditions, nucleation-and-growth kinetics, and strategies for tailoring multiscale pore structures. It further provides a comparative analysis of interfacial regulation mechanisms for capillary-stress elimination across supercritical drying, freeze-drying, and ambient-pressure drying routes. We also dissect the structure–property relationships underpinning Knudsen-effect-mediated gaseous thermal insulation, multi-scale hybrid network toughening, and inorganic phase-transition-induced in situ ceramization for thermal protection, demonstrating the synergistic optimization of thermal insulation, structural load-bearing, and ablation resistance. Finally, we summarise current applications in extreme thermal protection, environmental adsorption, electromagnetic interference shielding, and electrochemical energy storage and highlight future directions towards green, scalable manufacturing and intelligent materials design. Full article

Hybrid solar–thermal energy harvesting systems are an important advancement in renewable energy technology, enabling simultaneous production of electrical power and useful thermal energy within a single compact platform. However, their performance is often limited by poor heat transfer and inefficient mass transport of working fluids, leading to photovoltaic thermal degradation and significant exergy losses. This study aims to optimize heat and mass transport processes in a hybrid solar–thermal mechanical system to enhance energy recovery and ensure long-term operational reliability. A three-dimensional numerical model based on the finite volume method (FVM) was developed using the governing equations of continuity, momentum, and energy conservation. A Multi-Objective Genetic Algorithm (MOGA) was employed to determine optimal microchannel geometries by analyzing variable cross-section effects on flow behavior and thermal boundary layer disruption. At the Reynolds number of 2000, the optimized configuration increases the average Nusselt number by 43.5% compared to a smooth channel. Consequently, the photovoltaic operating temperature decreases by 12.6 °C, improving electrical efficiency by 9.3%. The system achieves a maximum thermal efficiency and net energy gain of 76.8%, while maintaining an acceptable 16.3% increase in pumping power. The results confirm that optimizing mass transport is essential for effective thermal regulation and improved energy conversion performance, providing a strong foundation for high-efficiency solar collector design. Full article

Large-scale renewable energy bases with high penetration of renewable energy are facing increasing challenges related to renewable energy curtailment. Concentrated solar power plants with thermal energy storage can provide dispatchable power output, while electric heaters offer a promising pathway for converting surplus renewable electricity into useful thermal energy. In this study, a photovoltaic–wind turbine–electric heater–concentrated solar power integrated energy system with a fixed CSP-EH configuration is investigated. The electric heater is introduced as the key electrical-thermal coupling device, which recovers otherwise curtailed photovoltaic and wind power and injects the converted thermal energy into the heat transfer fluid loop of the concentrated solar power plant. A mixed-integer linear programming model is developed to optimize the coordinated scheduling and evaluate different PV/wind capacity mixes under fixed CSP and electric-heater capacities. Results show that, under the fixed capacities of 100 MW concentrated solar power and 150 MW electric heater, the PV/wind capacity mix of 500 MW photovoltaic and 400 MW wind power achieves the best overall performance among the studied cases. Under different typical-day conditions, the electric heater recovers surplus renewable electricity, with recovery rates ranging from 16.06% to 20.21%. The proposed electric heater–concentrated solar power coupling mechanism transforms curtailed renewable electricity into dispatchable thermal energy, thereby reducing renewable energy curtailment, enhancing thermal-side flexibility, and improving the operating revenue of large-scale renewable energy bases under the studied PV/wind capacity-mix scenarios. Full article

Geothermal energy and underground thermal storage (UTES) are vital to the low-carbon energy transition, yet their optimization is bottlenecked by multi-scale heterogeneity, coupled thermal–hydraulic–mechanical–chemical (THMC) processes, and the high computational cost of full-physics simulations. This review systematically evaluates machine learning (ML) as a foundational paradigm for overcoming these computational and scale-bridging challenges. We categorize current advances into three key functional roles. First, data-driven upscaling directly maps pore-scale features to macro-scale effective properties, replacing traditional empirical homogenization. Second, deep surrogate models mimic high-fidelity THMC simulations at a fraction of the computational cost, enabling real-time prediction and uncertainty quantification. Third, physics-informed digital twins integrate real-time sensor streams with cloud architectures for dynamic reservoir management. Furthermore, we address the generalization limits of purely data-driven approaches, highlighting physics-informed machine learning (PIML) and hybrid architectures that embed conservation laws as strict constraints. Finally, we outline future pathways toward multimodal data fusion and edge-cloud deployment, marking a shift from static offline modeling to dynamic, physics-safeguarded real-time reservoir optimization. Full article

This study evaluates a disturbance-informed, planning-level workflow for assessing steady-state feeder performance and post-disturbance frequency security in renewable-rich distribution networks. The workflow links feeder operation in DIgSILENT PowerFactory to reduced-order frequency-security screening in OpenModelica and PSAT, with Pandapower used as an independent steady-state cross-check. The IEEE 33-bus feeder includes distributed photovoltaic units, DFIG-based wind generation, and a grid-forming battery energy storage system (BESS). Hourly feeder time-series results are used to identify renewable-output deficits, and each deficit is converted from MW to the common 10 MVA dynamic-system base before being applied as a conservative step disturbance. The steady-state validation gives a maximum voltage mismatch of 0.0155 pu, within the adopted 2% screening limit. The cross-tool frequency benchmark shows close agreement for nadir and settling time, while RoCoF is interpreted conservatively because of its sensitivity to numerical differentiation and event implementation. As renewable penetration increases from 0% to 100%, the minimum bus voltage remains close to 1.0 pu (0.9999–0.9991 pu), the maximum bus voltage rises from 1.0295 pu to 1.0826 pu, and feeder losses increase from 0.0246 MW to 0.1531 MW. The 24 h assessment gives a maximum daily voltage of 1.0755 pu at 100% penetration, while loading remains below thermal limits. For the corrected 75% severe event (0.3048 MW; −0.0305 pu on the 10 MVA base), the 2 MW droop-plus-FFR case improves the nadir from 49.9695 Hz without support to 49.9924 Hz. Voltage therefore becomes the earliest binding screening constraint from 50% penetration onward, whereas thermal loading and supported frequency nadir remain non-binding under the studied conditions. Full article

The large-scale integration of photovoltaic generation into distribution grids has introduced significant operational challenges, including voltage excursions, reverse power flows, and increased variability. Battery energy storage systems (BESSs) offer a versatile solution by providing coordinated active- and reactive-power support. However, their scheduling in active distribution networks is challenging because of the non-convex alternating-current (AC) power-flow equations, the nondifferentiability of battery-degradation modeling, and uncertainty in renewable generation and demand. This paper proposes a two-stage methodology for the day-ahead operation of BESSs in ADNs. In the first stage, parallel particle swarm optimization (PPSO) determines the hourly active- and reactive-power schedules of the BESS units. In the second stage, a matrix-based multi-period AC power flow based on successive approximations evaluates the schedules and verifies voltage, thermal, converter-capability, and state-of-charge (SoC) constraints. A rainflow-counting degradation model is incorporated into the objective function to account for cycling and calendar aging costs. The methodology is assessed through ablation analyses comparing active-power-only and coordinated P–Q dispatches, degradation-unaware and degradation-aware scheduling, and serial and parallel PSO implementations. It is validated on modified 33-, 69-, and 136-node systems under deterministic and uncertainty-based operating conditions, including 100 demand and PV-generation scenarios. PPSO is compared with parallel versions of the adaptive Jaya algorithm (AJAYA), genetic algorithm (GA), multi-verse optimizer (MVO), salp swarm algorithm (SSA), grey wolf optimizer (GWO), and vortex search algorithm (VSA), using operating-cost reduction, computational time, solution variability, feasibility indicators, BESS lifetime, and weekly cost analysis. Additionally, exact one-sided Wilcoxon signed-rank tests with Holm adjustment are used to assess the statistical significance of the economic differences between PPSO and the benchmark methods. Results show that PPSO provides the lowest or most competitive operating costs and the shortest computational time in the evaluated cases, while all network and storage constraints remain satisfied. Full article

The European Union’s climate policy promotes waste incineration as an alternative to landfilling. However, the continuous nature of waste generation, combined with seasonal variability in energy demand, leads to a mismatch between heat production and consumption in waste-to-energy systems. Seasonal Borehole Thermal Energy Storage (BTES) systems are one option for mitigating this mismatch. The aim of this study was to develop a theoretical geological model of a BTES-type storage system located in the Carpathian Foredeep and to simulate its multi-year operation using the FEFLOW numerical modeling software. The model represents an initial assessment of system performance under assumed geological and operational conditions and has not yet been validated against field measurements. Two operating scenarios were analyzed. In the 1st scenario, both heat injection and heat extraction from the storage system occurred through Borehole Heat Exchangers (BHEs) located in the center of the storage system. In the 2nd scenario, heat extraction is initiated through heat exchangers located in the outermost zone of the BTES field. The analysis focused on the temperature of the circulating working fluid in the U-tubes and on variations in heat transfer rate during injection and extraction cycles. The energy performance of the system was evaluated for both configurations. The results showed that the reversed-flow operating strategy provided a higher thermal energy recovery ratio and more favorable long-term thermal performance than the center-to-center flow configuration, indicating the potential feasibility of BTES operation under the assumed Carpathian Foredeep conditions. Full article

With the rapid transition of the global energy structure, large-scale clean energy integration has become a major trend in power system development. Nevertheless, the intermittency and stochastic fluctuation of renewable power generation threaten the secure operation of power systems. With high power density and millisecond-level response capability, supercapacitors act as key technical support for frequency stabilization and grid frequency fluctuation suppression. This paper reviews research advances in the application of supercapacitors to power system frequency regulation. It presents the classification and energy storage mechanisms of supercapacitors, analyzes their technical advantages in frequency regulation, and summarizes key research progress involving control strategies, topologies and capacity optimization schemes. Three typical application scenarios are illustrated: standalone frequency regulation, coordinated thermal-storage frequency regulation, and auxiliary frequency regulation for renewable power plants. Considering future requirements for frequency regulation, potential research directions are put forward to provide references for follow-up related studies. Full article

This study directly compares a photovoltaic (PV)-powered vapor-compression chiller with a solar-thermal-driven absorption chiller for localized cooling of the tomato crop zone in a 1536 m² smart greenhouse under a hot-arid climate. The principal contribution is a controlled system-level comparison of two solar-cooling pathways under the same greenhouse load, solar-aperture area, terminal equipment, rated cooling capacity, and crop-zone temperature-control constraints. The previously validated greenhouse model was transitioned from EnergyPlus 8.9 to Version 23.1, after which the two alternative plants were connected to the same base model. Base-case annual simulations produced nearly identical chiller cooling energy (1669.3 and 1668.9 MWh) and was only 4 and 5 h above 28 °C. The PV-powered system required 101.6 MWh of net grid electricity, whereas the absorption system used 202.3 MWh of electricity and 253.2 MWh of natural gas and achieved an 84.23% solar fraction. Static operational primary energy was 331.2 and 912.7 MWhPE, respectively; HSDH28 was 0.50 and 0.81 °C·h; and peak grid import was 113.46 and 63.61 kW. The absorption case additionally required 10,103.6 m³/yr of cooling-tower makeup water. Storage/EMS sensitivity changed the absorption solar fraction from 58.17% to 88.30% and natural-gas use from 187.7 to 674.0 MWh/yr without materially changing cooling service. Matched 50–100 W/m² daytime latent-load sensitivity increased annual cooling by 14.7–28.8%. At the 100 W/m² bound, HSDH28 increased to 49.32 °C·h for PV and 8.06 °C·h for absorption, while the principal energy–infrastructure trade-off remained: static primary energy was 712.4 versus 1354.2 MWhPE and peak grid import was 137.46 versus 63.96 kW. A bounded hourly primary-energy-factor stress test did not reverse the technology ranking, and balanced TOPSIS scores were 0.766 for PV and 0.234 for absorption. The results show that PV vapor compression minimizes operational primary energy and cooling-water use, whereas solar-thermal absorption reduces electrical peak demand and shows greater thermal-control resilience at the highest tested latent-load bound. Full article

Efficient interfacial thermal transport in two-dimensional heterostructures is essential for improving heat dissipation and operational stability in next-generation energy conversion and energy electronic devices. Here, nonequilibrium molecular dynamics simulations are employed to investigate the thermal transport behaviors of WSSe/MoS₂ and WSSe/MoSe₂ lateral heterostructures. Unlike the commonly assumed flat interface, both heterostructures spontaneously form an intrinsically curved interface after relaxation, introducing a unique structural feature for phonon transport. The armchair interface exhibits higher interfacial thermal conductance than the zigzag counterpart due to stronger phonon coupling. Furthermore, external strain can effectively regulate thermal transport through the competition between interface flattening and phonon scattering, while increasing temperature enhances thermal conductance by activating low-frequency phonons. In contrast, vacancy defects also significantly suppress heat transfer by disrupting interfacial bonding. This work reveals the critical role of intrinsic interface curvature in phonon-mediated thermal transport and provides a new strategy for designing high-performance thermal management materials based on Janus heterostructures for advanced energy conversion and storage technologies. Full article

Solar-assisted thermochemical cycles can convert intermittent solar energy into storable chemical fuels. Within the European SULPHURREAL project, elemental sulfur is investigated as a long-term energy-storage medium in a cycle based on H₂SO₄, S, and SO₂. This work investigates an indirect magnesium-mediated route for the disproportionation of SO₂. The proposed cycle consists of three steps: aqueous reaction of SO₂ with MgO to form sparingly soluble MgSO₃; thermal decomposition of MgSO₃ through competing pathways producing elemental sulfur, MgSO₄, MgO, and SO₂; and high-temperature decomposition of MgSO₄ to regenerate MgO and produce sulfur oxides and oxygen. All three steps were experimentally investigated using laboratory-scale reactors, thermogravimetric analysis, X-ray diffraction, ion chromatography, and calorimetric measurements. The sulfur yield was approximately 25% of the theoretical maximum, corresponding to 8.3% relative to the initial SO₂ amount. Complete MgSO₄ conversion was achieved after 90 min at 1100 °C, at which temperature the SO₂-forming pathway accounted for approximately 87% of the gaseous sulfur products. The experimental results were used to establish a preliminary mass and energy balance for the closed-loop process. The calculated gross heat requirement was 5349 kJ mol⁻¹ of sulfur, corresponding to an energy efficiency of 5.5% when heat recovery was not considered. These results demonstrate the technical feasibility of the proposed magnesium-mediated route and provide a quantitative basis for its further development, identifying sulfur selectivity, high-temperature sulfate decomposition, quantitative product recovery, and heat integration as the main priorities for process optimisation. Full article

As the global energy sector and maritime industry transition toward carbon neutrality, Carnot batteries have emerged as a critical technology for flexible, long-duration energy management. Carnot batteries, which operate on a Power-to-Heat-to-Power principle, present a highly promising alternative to conventional electrochemical batteries. The present study provides a review of Carnot battery architectures, systematically evaluating their thermodynamic cycles, working fluids, Thermal Energy Storage media and key turbomachinery components. A comparative assessment of the current literature illustrates that system selection requires balancing round-trip efficiency, Energy Storage Density and Technology Readiness Level. According to the findings of the present study, high-temperature Brayton cycles offer robust baseline efficiencies of 60–80% whereas subcritical Rankine cycles benefit from commercial maturity and can achieve efficiencies exceeding 200% when integrated with cryogenic heat sinks like LNG. It should be clarified that efficiency values exceeding 100% represent “Apparent Round-Trip-Efficiencies (RTE)” resulting from the thermodynamic contribution of external exergy streams, such as LNG cryogenic cold, rather than standalone cycle efficiencies, which are strictly below 100%. In addition, volumetric energy density varies drastically based on the physical phase of the storage medium, scaling from under 1 kWh/m³ for unpressurized water to over 385 kWh/m³ for advanced thermochemical systems. Although most configurations currently remain in the prototyping phase, the technology holds transformative potential for the maritime sector. Carnot batteries can deliver a self-contained, zero-emission electrical power supply to cover the vessel’s electrical load requirements during harbor stays and transit within Emission Control Areas (ECAs) by dynamically capturing and storing shipboard waste heat during open sea transit. Full article

Solar-driven interfacial evaporation (SDIE) represents a highly promising technology for decentralized desalination and wastewater treatment, yet its practical industrial deployment is severely constrained by the intrinsic intermittency of natural solar irradiance and nocturnal salt crystallization. To smooth energy fluctuations and achieve all-weather, continuous freshwater output, integrating solid–liquid phase change materials (SLPCMs) into SDIE has evolved into a system-level paradigm shift driven by advanced spatiotemporal thermal-mass management. This review systematically summarizes recent breakthroughs in micro-to-macro structural engineering for phase-change-coupled SDIE systems. Spatially, advanced microscopic encapsulation strategies such as 3D matrices, core–shell architectures, and solid–solid transitions eradicate molten PCM leakage and reconstruct heat transfer networks, while macroscopic configurations involving sandwich structures and 3D directional channels realize functional zoning to maximize thermal localization. Temporally, the controlled nocturnal release of stored latent heat establishes a cross-timeline energy relay, sustaining dark evaporation and activating interfacial hydrodynamics via Marangoni convection and thermophoretic diffusion to prevent salt clogging under extreme conditions. Furthermore, cross-disciplinary integrations for water-electricity co-generation, targeted resource recovery, and environmental remediation are comprehensively discussed. Finally, critical engineering challenges regarding scalability, cost-effectiveness, and condensation system integration are addressed, offering forward-looking perspectives on coupling thermal storage with physical catalysis to transcend classical thermodynamic limits. Full article

Maintaining the rheological performance of wormlike micellar fluids at elevated temperatures remains challenging. Conventional viscoelastic surfactant (VES) systems may undergo thermally induced micellar scission and loss of gel-like viscoelasticity at elevated temperatures. In this study, we investigate the size-dependent reinforcement of long-chain C22⁺ wormlike micellar systems by silica nanoparticles under a temperature-ramp protocol reaching 160 °C. Under the applied temperature-ramp protocol, the formulation containing 0.10 wt% of 15 nm SiO₂ nanoparticles exhibited the highest measured rheological response among the tested formulations, retaining an apparent viscosity of approximately 210 mPa·s and a plateau storage modulus of approximately 18.5 Pa during the 20 min isothermal holding period at 160 °C, compared with a plateau storage modulus of approximately 11 Pa for the corresponding VES system. At equal nanoparticle mass loading, the 15 nm particles produced approximately 18% and 6% higher G′ and G″, respectively, than the 500 nm particles. The rheological results, together with qualitative electrokinetic measurements after dilution, are consistent with nanoparticle-surfactant association that may promote micellar entanglement and network reinforcement. The nanoparticle-enhanced viscoelastic surfactant (N-EVES) formulation reduced the acid-rock reaction rate to approximately 25% of that measured for conventional HCl while showing an apparent effective H⁺ diffusion coefficient of the same order. Scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDS) detected Si- and N-containing species on the treated carbonate surface, suggesting that surface adsorption or deposition may contribute to reaction retardation. Parallel dual-core flooding under a permeability contrast of approximately 13 showed fluid redistribution toward the low-permeability core. Based on the axial wormhole penetration length obtained from the CT reconstruction, the normalized axial wormhole penetration fraction of the low-permeability core was approximately 70% for the 0.10 wt% formulation. These results provide experimental evidence of nanoparticle-size-dependent rheological reinforcement, acid-rock reaction retardation, and core-scale flow redistribution under strongly acidic and high-temperature conditions. Full article

With the acceleration of the global energy transition, hydrogen is increasingly considered a potential energy carrier for renewable-energy integration, large-scale energy storage, and industrial decarbonization. Proton exchange membrane (PEM) water electrolysis is well suited to variable renewable power because of its fast load response, wide operating range, and compact system structure. However, most existing studies focus on steady-state performance, materials, or model-based analysis, while system-level experimental data on the dynamic behavior of industrial-scale PEM water electrolysis systems remain limited. In this study, the dynamic performance of a 50 kW-class PEM water electrolysis system was experimentally investigated under stepwise load changes, pressure variation, and cold-start conditions. The responses of voltage, temperature, pressure, hydrogen-in-oxygen (HTO), oxygen-in-hydrogen (OTH), and system energy consumption were analyzed. The voltage followed current step changes within seconds, indicating a fast electrical response. In contrast, the thermal response was much slower, and the system required approximately 34 min to approach the rated thermal condition from a cold start. The gas-composition measurements exhibited minute-scale response delays and gradual settling after changes in operating conditions. When the operating pressure increased from 1.2 MPa to 2.9 MPa, the HTO content increased from 0.383% to 0.545%. When the current increased from 300 A to 1200 A, the OTH content decreased from 1001.77 ppm to 5.86 ppm. Energy-flow analysis showed that the total system power consumption under full-load operation was 69.7 kW, including the electrolyzer-related part and balance-of-plant consumption. These results clarify the different response time scales of electrical, thermal, and gas-composition variables in a 50 kW-class PEM water electrolysis system and provide experimental support for dynamic operation under variable renewable power input. Full article