Search Results (420)

To tackle the intermittency of renewable energy and realize the repurposing of abandoned oil and gas wells, this study proposes a compressed air energy storage (CAES)-based cogeneration system integrated with geothermal energy and abandoned oil and gas wells, and conducts a five-dimensional comprehensive analysis covering exergy, exergoeconomic, exergoenvironmental, economic and environmental performance. The optimal operating parameters are determined as air compressed to 200 bar, an ORC turbine inlet pressure of 16 bar and an inlet temperature of 110 °C. The system’s annual total power generation is 2,971,416.5 kWh during low-power daytime operation, and 20,131,785 kWh during high-power nighttime operation. Compared with conventional CAES systems, the proposed system reduces total exergy destruction by 4121.35 kW and increases exergy efficiency from 48.49% to 63.38%. Coolers, geothermal heat exchangers and compressors are the main sources of exergy destruction cost and capital investment, while COM1, HE1 and HOT1 are the key components causing environmental impacts. The system realizes cogeneration of power, hydrogen and pure water, with a static payback period of about 5.4 years and significantly reduced TEWI value at elevated turbine inlet pressure. This system achieves multi-objective synergies in energy efficiency, economy and environment, providing a feasible scheme for the green repurposing of abandoned oil and gas wells and cascaded utilization of renewable energy. Full article

Urban heat stress is intensifying under climate change, particularly in outdoor public spaces where conventional mechanical cooling is impractical. This study develops a climate-driven, system-level numerical framework to evaluate the pre-deployment feasibility of modular, solar-powered spray cooling canopies across 110 cities in Türkiye. Hourly Typical Meteorological Year (TMYx) weather files, representing a single typical year constructed from 2009 to 2023 source data, are used to estimate photovoltaic (PV) energy yield, electrical load, feasible misting duration, water demand, and PV-to-load autonomy under summer daytime conditions. The misting operation is governed by a rule-based adaptive control strategy based on air temperature, relative humidity, and plane-of-array irradiance. To support transferable comparison, the cities are classified into six summer climate-archetype zones using k-means clustering of standardized climate variables, including temperature, humidity, irradiance, wind speed, and summer precipitation. Results show that evaporative cooling feasibility is governed primarily by humidity rather than temperature alone. Hot–Dry Inland cities exhibit the longest mean misting duration (501.90 h) and highest water demand (30,152 L per module), but the lowest PV-to-load autonomy ratio (1.55) because of high pump-driven electrical demand. In contrast, Humid Black Sea cities show minimal misting duration (11.43 h) and water use (465 L per module), but the highest autonomy ratio (39.68) due to very limited system activation. Thus, high autonomy does not necessarily indicate high cooling usefulness. The proposed framework provides a reproducible screening tool for identifying where PV-powered spray cooling canopies are climatically suitable, where water and PV sizing become limiting, and where alternative outdoor heat-mitigation strategies may be more appropriate. Full article

Wittichenite (Cu₃BiS₃) was synthesized by mechanical alloying (MA) followed by hot pressing (HP), and its phase evolution, thermal stability, charge transport behavior, and thermoelectric performance were systematically examined. X-ray diffraction analysis of the MA powders revealed broadened diffraction peaks, indicating reduced crystallinity and refined crystallite size. After HP consolidation, a well-defined single-phase orthorhombic wittichenite structure was obtained. These results demonstrate that the mechanically induced solid-state synthesis was effectively initiated during MA and subsequently completed through crystallization, defect relaxation, and densification during HP. The MA–HP processed specimens exhibited high relative densities of 94–98% of the theoretical value and a homogeneous microstructure without detectable compositional segregation or grain-boundary enrichment, confirming the formation of a structurally and chemically stable single-phase bulk material. Thermal analysis identified a reversible polymorphic phase transition from P2₁2₁2₁ to Pnma at low temperature, followed by structural relaxation and the onset of partial decomposition at higher temperatures, indicating that Cu₃BiS₃ retains structural integrity below 700 K, which defines the relevant operating window for thermoelectric evaluation. The samples exhibited p-type semiconducting behavior, with electrical conductivity increasing with temperature due to thermally activated hole transport and showing an additional enhancement across the structural transition region. The Seebeck coefficient remained positive over the entire temperature range and decreased gradually with increasing temperature, consistent with semiconductor transport characteristics. The thermal conductivity remained low at 0.30–0.38 W·m⁻¹·K⁻¹, with a negligible electronic contribution, confirming that heat transport is dominated by lattice phonon scattering. As a result of the combined increase in electrical conductivity and intrinsically low thermal conductivity, the dimensionless figure of merit (ZT) increased continuously with temperature and reached 0.17 at 673 K. These results demonstrate that the MA–HP route provides an effective and scalable strategy for producing phase-pure Cu₃BiS₃ with controlled microstructure and reproducible thermoelectric performance. Full article

Hot forging of Ti-6Al-4V is extensively utilized in the manufacture of orthopedic implants; however, the coupled influence of strain rate and temperature on ductile damage evolution during the forging of femoral stems remains insufficiently quantified. In this study, a finite element framework is developed to analyze and optimize the hot forging process, incorporating strain rate- and temperature-dependent plasticity, as well as the Johnson–Cook damage criterion. Mesh convergence is established, and the assumption of quasi-adiabatic conditions is substantiated via Péclet number analysis. A full factorial design is implemented by varying the ram velocity (0.1–0.5 m/s) and initial billet temperature (850–950 °C) to evaluate the forging load, stress triaxiality, equivalent plastic strain, and damage accumulation. Results indicate that process kinetics govern the mechanical response: increasing the ram velocity enhances strain-rate hardening, resulting in higher peak loads, while explicitly reducing stress triaxiality and suppressing ductile damage evolution. Conversely, temperature exhibits a secondary influence within the investigated domain. Validation of the damage criterion confirms safe operating windows, identifying low-velocity forging as a high-risk condition for localized defect formation. These findings provide practical guidelines for the strain-rate-based optimization of thermomechanical processing parameters for Ti-6Al-4V femoral stems. Full article

In hybrid rolling bearings operating under extreme high-temperature and high-load conditions, steel rolling elements are prone to early failure, which has accelerated the widespread adoption of ceramic materials. To address the limitations of conventional studies, which have focused mainly on macroscopic wear parameters while neglecting subsurface failure mechanisms and the relationship among sintering process, microstructure, and fatigue performance, this work systematically compares the tribological behavior of Si₃N₄ ceramic balls fabricated by high-pressure electric resistance hot-pressing (REHP) and B₄C ceramic balls prepared by conventional hot pressing (HP) against 52100 steel counterparts. The central innovation of this study lies in clarifying, based on Hertzian contact theory and Lundberg-Palmgren life theory, that subsurface orthogonal shear stress, rather than surface compressive stress, is the fundamental driving force for contact fatigue failure of ceramic balls. In addition, two distinct damage evolution modes are revealed: B₄C exhibits early-stage brittle fracture and large-scale spalling, whereas REHP-Si₃N₄ is characterized by microcrack initiation and slow crack propagation. Moreover, the intrinsic mechanism by which the REHP process significantly enhances the contact fatigue life of ceramics is elucidated; namely, it refines grain size, eliminates residual porosity, and increases densification. The results show that, under the same high-load conditions, the mass loss of REHP-Si₃N₄ ceramic balls is only 35.7% of that of HP-B₄C, while the service life is extended by 20%. This work provides a key theoretical basis for ceramic material selection and sintering process optimization in high-performance hybrid bearings. Full article

To address the thermal management challenges of electric vehicle power batteries under complex operating conditions, this study proposes a biomimetic honeycomb-shaped liquid cooling plate and conducts a systematic analysis of its cooling performance along with machine learning-based prediction for CTP lithium iron phosphate battery packs. A fluid–solid coupling numerical model was developed using ANSYS Fluent, employing the control variable method to investigate the effects of coolant flow rate (0.2–4.2 m/s), coolant inlet temperature (5–32 °C), ambient temperature (15–39 °C), and battery heating power (1000–5500 W/m³) on the maximum battery temperature. Simulation results demonstrate that the honeycomb structure leverages its hexagonal channel geometry and large specific surface area to achieve rapid and uniform heat transfer, with no localized hot spots observed across all operating conditions. The maximum battery temperature exhibits a marginal decreasing trend as coolant flow rate increases, with 1.4 m/s approaching the optimal flow rate; it rises approximately linearly with elevated inlet temperature, ambient temperature, and heating power—each 3 °C increase in inlet or ambient temperature raises the maximum temperature by approximately 1.98 °C and 3 °C, respectively, while a 500 W/m³ increase in heating power corresponds to an approximately 2.8 °C rise. Under standard conditions (heating power: 3000 W/m³; inlet temperature ≤23 °C; ambient temperature ≤27 °C), the maximum battery temperature remains below 45 °C; high-heating (≥3500 W/m³) or high-temperature (≥30 °C) scenarios require coordinated control strategies. Furthermore, based on simulation data, seven machine learning models—BPNN, GA-BP, PSO-BP, SVM, RBFNN, RF, and LSTM—were constructed and evaluated for their performance in predicting the maximum temperature of battery packs. The results showed that the LSTM model achieved the highest prediction accuracy on the validation set, with RMSE, MAE, MAPE, and R² values of 0.8068, 0.6891, 1.5653%, and 0.9865, respectively, while models such as SVM and RBFNN exhibited severe overfitting. This study validated the engineering effectiveness of the honeycomb structure liquid cooling plate and identified LSTM as the optimal model for predicting battery pack maximum temperature, providing a theoretical foundation and data support for the structural design and intelligent control of power battery thermal management systems. Full article

Substation buildings must achieve energy conservation and carbon reduction, and thereby realize sustainable development, by optimizing envelope structures and adopting systematic design, all while meeting the operational demands of high-precision electrical equipment. This research takes a typical substation building (including switchgear building, main control building, and guard room) in a hot-summer and warm-winter zone as a case study to evaluate the effects of building thermal performance on building energy use. The building cooling load and the energy-saving rate of the air conditioning system are selected as key evaluation metrics. Using building cooling load and energy-saving rate as core indicators, energy simulation software is employed to analyze the thermal parameters of the building envelope of the switchgear building and the main control building. The influence of operational parameters, such as air conditioning setpoint temperature and internal heat gains, on the building cooling load is also investigated in order to explore design solutions that achieve sustainable development. Results indicate that the cooling load per unit area of the switchgear building is significantly higher than that of the main control building. Among the factors analyzed, the air conditioning setpoint temperature has the most substantial impact on the cooling load; increasing it by just 1 °C can reduce the load by 7–8%. When the optimal values of each factor are adopted, the energy-saving rates of the switchgear building and the main control communication building can reach 32.09% and 24.08%, respectively. This research aims to provide valuable references for determining appropriate building thermal performance parameters and operational settings for fully outdoor 220 kV substation buildings in hot-summer and warm-winter zones, thereby contributing to the sustainable development of buildings. Full article

On-site hydrogen refueling stations (HRS) face significant operational challenges due to the stochastic nature of hydrogen demand, creating a severe supply–demand mismatch. Under traditional pressure-based hysteresis control, this volatility forces Proton Exchange Membrane (PEM) electrolyzers into frequent start–stop cycles, accelerating degradation and reducing efficiency. In response, this study introduces an automated control framework integrating macroscopic gas-state modeling with deep-learning-based demand prediction. First, a real-gas thermodynamic model was established. Monte Carlo simulations of 100 random filling scenarios identified a robust design benchmark of 4.5 kg per vehicle. A low filling stability coefficient (5.02%) confirmed that individual thermodynamic fluctuations are negligible, validating a traffic-flow-driven demand approach. Next, a deep Long Short-Term Memory (LSTM) network was developed to forecast short-term demand. Trained on an 8784 h dataset exhibiting “double-peak” traffic patterns, the model achieved high precision on the unseen test set, yielding a Root Mean Square Error (RMSE) of 6.75 kg and a normalized RMSE (nRMSE) of 0.0987, explaining 82% of the demand variance. Finally, an LSTM-informed demand-following control strategy was formulated to enable proactive, thermally bounded operation alongside a novel “Hot Standby” mechanism. Maintaining a minimal 3.0 kg/h holding current during idle periods sustains stack temperatures above 60 °C, effectively mitigating thermal stress. Comparative simulations over 1464 h demonstrated that the proposed framework reduces detrimental cold start–stop cycles by 98.4% (from 61 to 1) and suppresses power output fluctuations by 40.7% compared to the traditional baseline. These results confirm that data-driven control significantly enhances operational stability, facilitates grid integration, and extends core equipment service life. Full article

Climate change alters not only the availability of solar radiation, but also the thermal, humidity, and cloudiness conditions under which solar energy systems operate. However, limited attention has been paid to the simultaneous comparison of photovoltaic and solar thermal responses using a common hourly climate-based framework under Central European conditions. This study evaluates long-term climate-driven changes in the operating conditions of photovoltaic (PV) panels and solar thermal collectors across five Slovak locations representing contrasting local climatic and topographic settings. Hourly ERA5-Land data for 1985–2024 were used to derive climatic indicators, photovoltaic operating indicators, and solar thermal performance indicators. The analysis combined long-term Mann–Kendall and Sen’s slope trend assessment with a comparison between the reference period 1985–1994 and the recent period 2015–2024. The results show that mean air temperature increased by 1.50–1.69 °C, global horizontal irradiance by 3.24–5.66%, and high-irradiance hours increased substantially across all sites. Photovoltaic yield increased by 2.21–4.52%, but this improvement was accompanied by higher PV cell temperature, more hot operating hours, and increased temperature losses. Solar thermal collectors showed a stronger relative response, with useful thermal gains increasing by 7.27–12.33% at 35 °C and by 9.00–15.73% at 50 °C. The Relative Solar Thermal Gain Advantage was positive at all locations, indicating that recent climatic conditions favored solar thermal gain more strongly than PV yield under the applied assumptions. The findings demonstrate that recent climatic data should be used in solar-system design and that photovoltaic and solar thermal technologies require separate interpretation because they respond differently to warming and changing radiation conditions. Full article

This paper presents a case study demonstrating the operation of a 50 kVA three-phase variable-speed diesel generator at a Spanish Antarctic research base, located in an area of special ecological and environmental value, under conditions of extreme humidity and temperature. It verifies the fuel savings achieved through the use of variable-speed technology compared to standard, constant-speed generators. Furthermore, given that the price of fuel is significantly higher due to the high cost and complexity of transporting it to the base, the fuel savings at the base represent a huge logistical advantage, quite apart, of course, from the environmental benefits of such savings. A key feature of the equipment presented is that it has a system for recovering waste heat from the combustion engine, which, when integrated into the base’s hot water system, is used to increase the domestic hot water capacity, adding value to the machine whilst also delivering fuel savings. Full article

Buildings in warm–humid and hot–arid coastal climates experience continuous cooling demand due to high solar radiation, humidity, and extended cooling seasons. Reducing operational energy use and carbon emissions through improved early-stage design is therefore essential. This study investigates a simulation-based evolutionary optimization framework to evaluate energy-efficient design strategies for residential buildings across representative warm–humid and hot–arid climates. A prototype residential building was modeled in DesignBuilder using EnergyPlus and evaluated across four locations: Singapore, Miami, Rio de Janeiro, and Jeddah. Key variables included the window-to-wall ratio, glazing type, wall and roof constructions, cooling setpoint, and HVAC system configuration. An evolutionary search process based on the NSGA-II algorithm was applied to systematically explore high-performing building configurations using energy use intensity (EUI) and operational carbon indicators. The results indicate a consistent tendency toward boundary values within the defined parameter ranges. The window-to-wall ratios consistently approached the minimum tested value (20%), while the cooling setpoints approached the upper bound (26 °C) within the defined parameter ranges. This behavior highlights the influence of solar gains and operational temperature settings on cooling demand. Low-emissivity glazing and insulated envelope assemblies were frequently associated with improved performance. Miami achieved the lowest EUI among the high-performing configurations (75.08 kWh/m²·yr; 27.55 kgCO₂/m²·yr), while other locations showed higher demand due to climatic conditions. These findings emphasize the importance of parameter range selection and demonstrate the effectiveness of simulation-based evolutionary search methods in identifying high-performing configurations within defined constraints. Full article

Addressing issues such as corrosion and the eccentric wear of metal tubing strings, low heating efficiency, and high operation and maintenance costs of lifting systems in heavy-oil extraction, core equipment comprising carbon-fiber-reinforced PEEK (Polyetheretherketone) multi-layer composite continuous tubing has been developed. This equipment integrates an embedded cable-laying system and an intelligent regulation module, establishing a rodless oil-extraction technology system suitable for heavy-oil reservoirs. This article systematically describes the process structure, preparation principle, core characteristics, and key parameters of this composite continuous tubing. By deriving an equivalent thermal-resistance model for the multi-layer structure and an unsteady-state heat-transfer equation, precise regulation of the wellbore temperature field is achieved. Combined with field tests at Well A in Jinghe Oilfield, the tubing’s effectiveness in reducing viscosity, increasing production, saving energy, and extending the operational cycle in heavy-oil extraction is verified. The results show that the carbon-fiber-reinforced PEEK composite continuous tubing possesses characteristics such as high strength, strong corrosion resistance, low friction, and high thermal insulation. When paired with a viscosity–temperature coupling regulation algorithm, the heating efficiency is improved by 40% compared to traditional electric heating rods. The efficiency ranges from 37% to 43% when the formation thermal conductivity fluctuates by ±20%. Field applications have achieved a 230% increase in daily oil production, a 30% reduction in system energy consumption, and an extension of the hot washing cycle to over 180 days. The development of this tubing breaks through the technical bottleneck of traditional metal tubing, providing a new material solution for the efficient and intelligent development of heavy-oil extraction, and has broad promotional value. Full article

In hot and humid regions, urban underground utility tunnels are susceptible to high temperature and humidity due to moist inlet air, cable heat dissipation, and limited ventilation jointly affecting the internal environment. To address this issue, an alternating ventilation strategy, in which fan operation is periodically reversed to switch between air supply and exhaust, is proposed. Compared to conventional mechanical ventilation, this strategy overcomes the constraints of unidirectional airflow and mitigates thermal and humidity stratification, with low retrofit requirements and good adaptability. Ventilation performance was evaluated using non-guarantee rates for temperature and relative humidity, i.e., the ratio of the number of measurement points where the temperature/relative humidity exceeds 40 °C/65% to the total number of measurement points in the utility tunnel (TNGR and RHNGR), non-uniformity coefficients (K_T and K_RH), and mean temperature (T_m). The alternating mode outperformed the conventional mode, reducing TNGR by 6.0% and Tm by 0.3 °C while improving temperature and humidity distributions and lowering cable temperatures. Although the reduction in T_m appears modest, it is practically meaningful because it helps weaken thermal stratification and local overheating, improves cable operating conditions, and may reduce the need for high-airflow operation when tunnel temperatures approach the permissible limit. Response surface methodology was further used to optimize the alternating ventilation parameters, indicating that the recommended fan commutation frequency is 2 under different inlet air temperatures. CFD validation confirmed the effectiveness of the optimized scheme. At an inlet air temperature of 35 °C, KRH decreased from 11.9% to 11.0% and Tm decreased from 37.5 °C to 36.9 °C. Full article

Brominated flame retardants (BFRs) are widely used in automotive polymers and electronic components, yet vehicles remain an under-characterized and potentially high-exposure microenvironment, particularly in hot climates. This study provides the first comprehensive assessment of BFR occurrence, sources, and exposure risks in vehicle dust from Saudi Arabia, addressing a critical regional data gap. This study systematically investigates the occurrence, compositional patterns, sources, and human exposure risks of polybrominated diphenyl ethers (PBDEs) and selected alternative BFRs in dust from 80 vehicles (domestic cars and taxis; model years 2015–2022) operating in Jeddah, Saudi Arabia. Dust samples were collected using a standardized vacuuming protocol, extracted and cleaned using solvent extraction and silica SPE, and analyzed via GC–NCI–MS. Both legacy PBDE congeners and emerging alternatives (including DBDPE and TBB) were consistently detected, with BDE-209 dominating the overall BFR burden with mean concentrations of 6560 ng/g in domestic vehicles and 5454 ng/g in taxis, with maximum values reaching 220,860 ng/g. Lower-brominated PBDEs occurred at substantially lower concentrations, reflecting the ongoing global transition away from Penta- and Octa-BDE formulations. Taxis exhibited generally higher concentrations than domestic vehicles, likely due to prolonged occupancy, increased usage intensity, and enhanced dust resuspension dynamics. Multivariate analysis (PCA and correlation) revealed two distinct source categories: (i) legacy Penta-BDE-related congeners associated with polyurethane foam and textile materials and (ii) high-brominated PBDEs and DBDPE linked to hard plastics and electronic components. Human exposure assessment demonstrated that dust ingestion is the dominant exposure pathway, while dermal and inhalation routes contribute minimally. Non-carcinogenic hazard indices (HI) were well below unity for all compounds (HI < 1.67 × 10⁻⁶), and incremental lifetime cancer risks (ILCR) for BDE-209 remained within or near accepted risk thresholds (7.52 × 10⁻⁶–1.04 × 10⁻⁵), although occupational exposure among taxi drivers was consistently higher. Overall, the results demonstrate that modern vehicle cabins act as significant microenvironments for chronic BFR exposure, particularly under high-temperature conditions. Despite generally low estimated risks, the combined effects of chemical persistence, bioaccumulation potential, and mixture toxicity—amplified by extreme in-cabin temperatures—highlight vehicles as overlooked yet significant exposure environments. These findings provide the first comprehensive dataset for the Arabian Peninsula and emphasize the need for climate-sensitive exposure assessment, safer material design, and targeted mitigation strategies in vehicle interiors. Full article

Passive thermoregulatory textiles, operating without external energy input, play a crucial role in maintaining the human body within the thermal comfort zone. However, integrating autonomous environmental adaptability with superior wearing comfort into a single textile remains a challenge. In this work, inspired by the autonomous actuation of water lilies, we proposed an intelligent strategy to fabricate thermoregulatory textiles that dynamically adapted to ambient temperature fluctuations, driven by a bidirectional shape memory polymer (SMP). To concurrently achieve robust thermal adaptability and human-body-compatible softness, a crosslinked polyethylene glycol–butyl acrylate (PEG-BA) bidirectional SMP network was engineered. The PEG phase, featuring a broad crystal size distribution, provided the dynamic skeleton for thermally induced actuation, while the incorporation of the BA component tuned the intrinsic softness to match conventional soft textiles. Consequently, the synthesized PEG-BA network exhibited an exceptional bidirectional shape memory effect with a reversible strain of 15.5%, while maintaining high macroscopic softness comparable to that of human skin. By integrating this bidirectional polymer into a garment to form adaptive vents, the smart textile demonstrated the capability to significantly elevate human thermal comfort. Specifically, the vents autonomously open in hot environments to accelerate heat dissipation and close in cool environments to suppress heat loss. Given its exceptional personal thermoregulatory performance and wearing compliance, this proposed strategy exhibits considerable potential for maintaining optimal human comfort against fluctuating environmental conditions. Full article