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International Journal of Energy Research is dedicated to providing a multidisciplinary, unique platform for researchers, scientists, engineers, technology developers, planners, and policy makers to present research results and findings in a compelling manner on novel energy systems and applications.
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More articlesChina’s Potential for Trade in Renewable Energy Products in RCEP Countries: A Gravity Model Analysis
China’s renewable energy products have an important place in international trade, and the conclusion of the RCEP agreement can create favourable external conditions for China’s renewable energy product exports. This paper measures the export potential of China’s renewable energy products to other RCEP countries through a trade gravity model. The results show that (1) the GDP of the importing and exporting countries, the energy consumption of the importing countries, and the particulate emissions damage significantly enhance China’s renewable energy product exports; (2) among the RCEP countries, China has a greater potential to export renewable energy products to five countries in 2020, which are mainly located in East and Southeast Asia; and (3) from a dynamic perspective, China’s renewable energy trade potential is increasing, while in the Oceania region it is weakening, while trade links to Southeast Asian countries are developing in a more mature direction. Based on the above research, this paper puts forward corresponding policy recommendations.
Performance Simulation of a Coal-Fired Power Plant Integrated with S-CO2 Brayton Cycle for Operational Flexibility Enhancement
In this study, a coal-fired power plant with an integrated S-CO2 cycle is proposed to improve the system operational flexibility. To optimize the performance, a control strategy of variable load regulation is proposed. First, a dynamic mathematical model of the system is established based on the conservation of mass and energy principles, and then, dynamic verification of the model is carried out. In order to evaluate the performance of the proposed system, an exergy analysis is performed on the S-CO2 cycle, indicating that the exergy loss rate of the heater in the cycle is the highest. Finally, the dynamic performance of the system is simulated, and the dynamic response of the power generation load is analyzed. In addition, the system is evaluated based on the performance indicator of the flexibility of the power generation. It was found that the proposed system in this paper has a large load ramp rate which can quickly follow the load response. Meanwhile, compared with load downregulation, the system has greater potential for load upregulation.
One-Pot Synthesis of Biodiesel from Acid Oil Using a Switchable Solvent, 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU), as a Bifunctional Catalyst
Biodiesel is a promising alternative to petrodiesel, but its production from acid oils retains several technical challenges. Therefore, this study developed a new approach involving 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed one-pot reaction (simultaneous esterification-transesterification) to produce biodiesel with enhanced reaction efficiency. The reaction was performed under water removal conditions and optimized using response surface methodology to maximize the biodiesel yield. The optimal conditions for the one-pot reaction had a reaction time of 2.73 h, temperature of 143°C, methanol:oil molar ratio of 24.3 : 1, and DBU loading of 30.1%. Under the optimal conditions, maximum total biodiesel of 97.1% was obtained. DBU could be repeatedly used for at least 5 cycles to yield over 91% biodiesel. This study suggests that DBU efficiently catalyzed esterification and transesterification simultaneously and the DBU-catalyzed one-pot reaction is an efficient method for biodiesel production from high-free-fatty acid oils.
Fault Detection and Classification to Design a Protection Scheme for Utility Grid with High Penetration of Wind and Solar Energy
This paper designed a protection scheme for utility grid with high share of renewable energy (RE) generated from wind energy and solar energy plants. This is based on extraction of features from the current using Stockwell transform (ST), Hilbert transform (HT), and alienation coefficient. A Stockwell index (SI) is designed by extracting current features using ST, a Hilbert index (HI) is designed by extracting current features using HT, and an alienation index (AI) is designed by extracting current features using an alienation coefficient. A fault index (FI) is formulated by multiplying the SI, HI, AI, and WF (weight factor). This FI is implemented for fault detection. Fault classification is achieved considering number of fault phases and ground fault index (GFI). This GFI is designed by processing zero sequence currents applying ST. GFI effectively identifies the ground involved during event of a fault. A designed protection scheme is effective to identify faults in the scenario of high RE share and during various cases of study which includes the variations of fault impedance, different fault occurrence angles (FOA), fault incident at different nodes, and noisy condition. This protection scheme effectively discriminates the fault events from the operational events such as feeder operation, load, and capacitor switching. Performance of hybrid protection method formulated in this paper is better relative to alienation coefficient-based protection scheme (ACPS) reported in literature. The ACPS has maximum error and mean error of fault detection equal to 9.54% and 5.99%, respectively, which is relatively high compared to the respective values for the proposed method which are 1.89% and 0.978%, respectively. ACPS is effective for detecting the fault events in noise level of 30 dB SNR (signal-to-noise ratio) whereas the proposed method effectively identifies the faults in the high noise scenario of 20 dB SNR.
Research on Characteristics of Hydrogen Dynamic Leakage and Combustion at High Pressure
Hydrogen is promoted as an alternative energy given the global energy shortage and environmental pollution. A scientific basis can be provided for the safe use and emergency treatment of hydrogen based on hydrogen leakage and combustion behavior. This study examined the stagnation parameters of dynamic hydrogen leakage and flame propagation in turbulent jets under normal temperatures and high pressure. Based on van der Waals’ equation of state for gas, a theoretical model for completely predicting stagnation parameters, outlet gas velocity, and flow rate changes in the process of high-pressure hydrogen leakage could be proposed, and the calculation result of this model was compared with the experimental result, with an error within ±10%. The progression and propagation of the flame in turbulent jets after ignition were recorded using the background-oriented schlieren image technology, and the propagation speed of flame from the ignition position downward and upward was calculated. Moreover, the influence of initial pressure, nozzle diameter, and ignition position on the flame propagation process and propagation speed was analyzed.
Enhanced Antimony Sulfide Sb2S3 Nanobars Solar Cell Performance with Doped PCDTBT Polymer
In this paper, antimony sulfide (Sb2S3) nanobars were prepared via a facile poly[N-9-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2,1,3-benzothiadiazole) (PCDTBT) organic polymer-assisted hydrothermal method. The impact of PCDTBT polymer concentration on the crystal structure, shape, optical, and electrical characteristics of Sb2S3 nanobars and thin films was studied. Analysis by X-ray diffraction indicated that raising the PCDTBT concentration caused the low-crystalline structure of the Sb2S3 nanobars to transform into a polycrystalline structure. In addition, the sample had a unique Sb2S3 (orthorhombic) crystalline phase, and the crystal size increased from 32 nm to 42.6 nm. Analysis of the data revealed that the Sb2S3 nanobars had a relatively high absorption coefficient (∼105 cm−1) in the visible spectrum, with band gap values ranging from 1.71 to 1.89 eV. At a high polymer concentration, the surface morphology and grain development were enhanced, and the chemical composition analysis peaks indicate a 2 : 3 atomic ratio for Sb : S. Transmission electron microscopy (TEM) micrograph examinations demonstrate the appearance of the produced Sb2S3, which is bar-like and made of nanobars with a typical width of 200–300 nm and confirm the crystallinity of the nanobars. The optimized Sb2S3 device has a power conversion efficiency (PCE) of 5.11%, a short-circuit current density of 16.5 mA/cm2, an open-circuit voltage of 456 mV, and a fill factor of 66.62% under AM1.5G illumination. It was observed that PCDTBT has a significant role in the creation of Sb2S3 nanobars and thin films.