International Journal of Energy Research最新文献

The need to mitigate environmental pollution and conserve the environment has led to the rapid expansion of renewable energy sources (RESs) and wind farms (WFs) in power systems. Thus, the involvement of WFs in frequency control and raising the frequency nadir (FN) under transient conditions of the system will be highly significant and indispensable. This research presents a proposal to enhance the system frequency by utilizing WFs and restoring the speed of the wind turbine (WT) rotor using the doubly fed induction generator (DFIG) while avoiding frequency second dip (FSD). In this design, once the disturbance and decrease in the system frequency are identified, the new power reference is incorporated into the maximum power point tracking (MPPT) characteristic as a function of two parameters, the changes in system frequency and the speed of the WT rotor, taking into account the torque limit. During frequency support, the frequency change parameter increases, while the rotor speed parameter decreases. This results in a smaller decline rate of the reference power, so that the electrical power goes below the mechanical power with a smooth gradient, not a step-wise manner. As a result, the rotor speed is restored fast without FSD. Another benefit is that the MPPT characteristic qualities are maintained during the frequency support, as the new reference value is incorporated into the MPPT characteristic. The MATLAB simulation results of the test system demonstrate that the proposed design successfully enhances the system’s frequency without inducing a FSD. Additionally, it effectively and rapidly restores the rotor speed.

Global climate change has intensified the search for renewable energy sources. Solar power is a cost-effective option for electricity generation. Accurate energy forecasting is crucial for efficient planning. While various techniques have been introduced for energy forecasting, transformer-based models are effective for capturing long-range dependencies in data. This study proposes N hours-ahead solar irradiance forecasting framework based on variational mode decomposition (VMD) for handling meteorological data and a modified temporal fusion transformer (TFT) for forecasting solar irradiance. The proposed model decomposes raw solar irradiance sequences into intrinsic mode functions (IMFs) using VMD and optimizes the TFT using a variable screening network and a gated recurrent unit (GRU)-based encoder–decoder. Our study specifically targets the 1-h as well as different forecasting horizons for solar irradiance. The resulting deep learning model offers insights, including the prioritization of solar irradiance subsequences and an analysis of various forecasting window sizes. An empirical study shows that our proposed method has achieved high performance compared to other time series models, such as artificial neural network (ANN), long short-term memory (LSTM), CNN–LSTM, CNN–LSTM with temporal attention (CNN–LSTM-t), transformer, and the original TFT model.

This study presents a novel micro-combustor (MC) design called micro-trapped vortex combustor (MTVC) for micro-thermophotovoltaic (MTPV) devices used in small-scale electricity generation. Traditional MC designs struggle to operate efficiently under ultra-lean regimes due to flame quenching, limiting their performance. The proposed MTVC incorporates the trapped vortex concept, inspired by aeronautical applications, to improve thermal performance and stability under ultra-lean conditions. Numerical simulations, using the Navier–Stokes and energy equations for laminar and reactive flow, are conducted to compare the MTVC with conventional micro-backward-step combustors (MBSCs) under hydrogen (H₂)–air mixture combustion. The study focuses on key performance parameters such as temperature distribution, heat recirculation, flame shape, flow topology, radiative power and emissions. The results show that the MTVC can operate at an ultra-lean equivalence ratio of Φ = 0.5, while the MBSC experiences flame quenching below Φ = 0.7. The MTVC design achieves up to 26.51% higher radiative power and a 36% improvement in energy conversion efficiency compared to traditional combustor designs. Additionally, the MTVC produces 43% less nitrogen oxides (NOx) emissions, demonstrating its potential for both higher efficiency and reduced environmental impact in portable power applications.

Storing hydrogen in metals has received much attention due to the advantages of this approach for safely storing. It is a promising method of storing hydrogen and eliminates the challenges associated with storing hydrogen gas at high pressure, which includes material durability, tank safety, and overall weight. Much work has been done for the past decade to bring this approach closer to wide-scale application. However, much experimental research is needed to improve the volumetric and gravimetric capacity, hydrogen adsorption/desorption kinetics, material life cycle, and reaction thermodynamics of potential materials for hydrogen storage. Other important properties to consider are transient performance, the regeneration process of spent storage materials, effective adsorption temperature associated with activation energy, induced pore sizes in materials, increasing pore volume and surface area, and materials densification. In recent years, this solid-state storage has progressed at conditions close to normal atmospheric pressure and temperature, with metal hydrides (MHs) emerging as a promising option. Their high storage density per unit volume, volume storage capabilities, and their ability to reverse the process while maintaining stability have qualified the MHs for low-pressure storage and fulfilling the hydrogen storing requirements. However, understanding the principles of kinetics and thermodynamics is crucial for understanding the reactions of MHs as they absorb and release hydrogen. This review evaluates the current hydrogen storage methods, the different types of MHs, their thermodynamics and kinetics, as well as their applications and challenges. For the advancement of further research in this field of study, suggestions for future work and studies are also provided.

A comprehensive probe was conducted to compare the impact of postdeposition annealing at 700°C in different ambient of nitrogen–oxygen–nitrogen (NON), forming gas–oxygen–forming gas (FGOFG), and argon–oxygen–argon (ArOAr) on the passivating characteristics of thulium oxide (Tm₂O₃) on the silicon (Si) substrate. The nitrogen ions have been incorporated in Tm₂O₃ passivation layers after annealing in NON and FGOFG ambient, of which NON ambient has impeded the growth of silicon oxide (SiO₂) interfacial layer (3.258 nm). Although a thicker SiO₂ interfacial layer (4.026 nm) was formed after annealing in FGOFG ambient, the attainment of the highest k value (16.8) indicated that the existence of hydrogen ions has assisted the improvement in the overall k value of Tm₂O₃ passivation layers. Furthermore, the capacitance–voltage characteristic revealed that the FGOFG ambient was effective in reducing the effective oxide charge (1.32 × 10¹² cm⁻²), while NON ambient was effective in passivating the slow trap density (STD) (3.20 × 10¹¹ cm⁻²). The Terman, Hill–Coleman, and high–low frequency methods have demonstrated the acquisition of the best interface quality during annealing in FGOFG ambient. As a result, the FGOFG annealing process has led to the maximum breakdown electric field of 4.03 MV/cm and the minimum leakage current density for the Tm₂O₃ passivation layer.

To meet the stringent requirements of high heat transfer performance and lightweight nature for aerospace heat storage equipment (HSE), this paper incorporates fins into the phase change material (PCM) and conducts an optimization design through experiment and simulation. Utilizing n-eicosane for heat storage and aluminum alloy 6061 as the fin material, the objective is to devise an HSE for high-power heating elements, ensuring that the hot end temperature remains below 50°C and the weight is within 3.5 kg during the operational period. Heat sources of 50 and 100 W are, respectively, employed for experimental testing. The experiments reveal that when the heating power is 100 W, the temperature in the heat concentration region ascends to 43.2°C after a heating duration of 1900 s; in the scenario where the heating power is 50 W, the maximum temperature reaches 38.0°C after 3800 s of heating. The discrepancy between the simulation results and the experimental outcome is within 5%, thereby attesting to the relatively high accuracy of the simulation. Simulations were carried out with the thickness and number of fins as variables to analyze the heat transfer performance and weight of the HSE. The results show that within the research range, as the fin thickness increases, the overall heat transfer effect is enhanced. When the fin thickness increases at equal intervals between 1.0 and 3.0 mm, except for 3.0 mm, the hot end temperature of the HSE gradually decreases, and the weight also increases with the increase of the fin thickness. With the increase in the number of fins, the hot end temperature decreases, and the decrease in the hot end temperature is particularly significant at 13 fins. Considering the comprehensive influence of heat transfer performance, hot end temperature, and weight in this HSE, the structure with a fin thickness of 2.0 mm and 13 fins is the best. The volume ratio of the PCM in the HSE is between 0.55 and 0.60. According to the optimization results, an HSE with a total weight of 3.33 kg is processed. After using the optimized HSE with a heating power of 50 W continuously applied for 10,000 s, the hot end temperature is 42.17°C, which is 6.9°C lower than that of the HSE without fins, and the melting rate is increased by 46%. After a heating power of 100 W is continuously applied for 4000 s, the hot end temperature is 48.16°C, which is 13.2°C lower than that of the HSE without fins, and the melting rate is increased by 71%. In addition, the heat transfer performance of the HSE has been analyzed, and the change law of the heat transfer performance during the melting process of the PCM was found. This study will provide guiding ideas and reference significance for the research and development of enhancing heat transfer and lightweight of high-power HSE in aerospace.

In this study, mixtures of high-octane gasoline–biodiesel (GB) rating from 0% to 20%, denoted as GB00-GB10-GB20, were chosen to be experimented under simulated gasoline compression ignition (GCI) engine inside a constant volume combustion chamber (CVCC) before making comparisons about spray and combustion characteristics. While typical data of the nonvaporization spray characteristics: spray penetration length, spray cone angle, and spray evolution were collected by varying 40–90 MPa of injection pressure at 15 kg/m³ ambient gas density, data representing combustion characteristics, namely the ignition delay, flame development, and heat release rate (HRR) were illustrated under 90 MPa injection pressure, same ambient gas density, and temperature variation of 900–1000 K. Although the fuel mixture spray development trends followed a similar pattern, GB10 and GB20 had an averagely 6.25%–7.7% faster impingement velocity than that of GB00 except for the lowest considered injection pressure. Additionally, the ignition delay reductions were recognized for both GB10 and GB20, with the duration dropping from 1.09 to 1.06 ms and 0.96 to 0.79 ms, respectively. The results for spray and combustion characteristics under GCI engine condition-like showed a close relationship, offering valuable insights for simulation, spray, combustion, and ANN modeling, thereby supporting the development and application of GCI engines.

A new molten salt reactor (MSR) design has been developed aiming for long-term operation and high safety. In order to enhance the integrity and economy of the system during the long-term operation, pumps were removed from the primary system, and the fuel salt flow was developed by natural circulation. In terms of thermal–fluidic, the natural circulation operation without a pump increases the reactor safety and resistance to accidents. The normal operation feasibility of the reactor was evaluated with the multiphysics analysis conducted with the Generalized Nuclear Foam (GeN-Foam) code. It was shown that the reactor can maintain stable power under a fixed heat exchanger outlet temperature condition. To increase the natural circulation, the active core region was designed to have a simple cylindrical shape, which induced a stagnation zone with slow velocity near the side wall. Due to the slow velocity, the stagnation zone has a substantially high temperature, and a flow guide was introduced to mitigate the stagnation effect. The impact of the flow guide was evaluated, including the reactivity feedback and delayed neutron precursor drift effect. The results highlight the importance of analyzing the flow distribution within the core in an MSR and demonstrate the effectiveness of the guide structure in ensuring stable core flow.

Air-breathing proton exchange membrane fuel cells (AB-PEMFCs) utilize ambient air for oxygen and cooling, making them suitable for small-scale applications. However, the absence of auxiliary systems presents considerable challenges in water and thermal management, which are crucial for ensuring optimal performance and durability. Poor management can lead to issues like membrane dehydration or cathode flooding. This deficiency subsequently impacts the affordability and longevity of AB-PEMFCs, both of which are critical considerations in the commercialization process. This review highlights the importance of water-thermal transport processes in enhancing efficiency and durability. While much research has focused on airflow’s role in thermal regulation, internal factors such as current density have received less attention. It is recommended to prioritize the coupling of water and thermal management in future studies, employing strategies like AI-driven optimization to accelerate the commercialization of AB-PEMFCs.

Energy crisis and wastewater treatment are critical global issues. In this study, a novel separator was made by boiling cotton rope with solutions of various salts and their concentrations. It was then employed in a dual-chamber microbial fuel cell (MFC) to treat municipal wastewater collected from 25 Area Wah Cantt, Punjab, Pakistan. Batch scale experiments were carried out to evaluate the effect of various variables, that is, different salts (NaCl, KCl, and MgCl₂) and their concentrations (0.2, 0.5, and 1 M) used in separator, wastewater volume (50, 500, and 1000 mL), and aluminum mesh thickness (0.6, 0.8, and 1 mm) on MFC performance in terms of current generation and wastewater treatment for 7 days. Analysis of collected wastewater showed that among the six studied physicochemical parameters, only two, that is, biological oxygen demand (BOD) and chemical oxygen demand (COD) were above the permissible limits of National Environmental Quality Standards (NEQS). Results after MFC experiments showed that separator containing 0.5 M NaCl produced a significantly (p < 0.05) high current of 68.16 µA as compared to the other studied salts and their concentrations, whereas COD and BOD were reduced up to 124.15 and 62.12 mg L⁻¹, respectively. A wastewater volume of 1000 mL generated a significantly (p < 0.05) high current of 83.41 µA compared to the other studied volumes, where COD and BOD residual values were 123.25 and 59.56 mg L⁻¹, respectively. An aluminum mesh thickness of 1 mm produced a significantly (p < 0.05) high current of 103 µA, while 120.89 and 68.93 mg L⁻¹ were achieved COD and BOD values, respectively. It was concluded that MFC performance was enhanced with an increase in wastewater volume and mesh thickness. Therefore, it is recommended that further pilot-scale continuous studies be carried out to implement this research on a larger scale.