• Energy Research
• 2021-2025close
• engineering and technology close
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Due to the uncertainty and fluctuation of distributed generation (DG) and load, the operation of active distribution network (ADN) is affected by multi-dimension factors which are described by massive operation scenarios. Efficient and accurate screening of severely restricted scenarios (SRSs) has become a new challenge in ADN planning. In this paper, a novel bi-level coordinated planning model which combines the short-time-scale operation problem with the long-time-scale planning problem is proposed. At the upper level, the demand response (DR) resource, an effective non-component planning resource characterized by low capacity price, high energy price, and short contract term, is co-optimized with the configuration of lines and energy storage systems (ESSs) to achieve the economic trade-off between the investment cost and the operation cost under SRSs. At the lower level, with the planning scheme obtained from the upper level, massive operation problems are optimized to minimize the daily operation cost; and the SRSs are provided to the upper level through a shadow-price-based scenario screening method, which simulates the planning information (i.e., the restricted degrees of operation scenarios) feedback process from ADN operators to ADN planners. Case studies on a 62-node distribution system in Jianshan New District, Zhejiang Province, China, illustrate the effectiveness of the proposed bi-level coordinated planning model considering DR resources and SRSs.

AbstractDC microgrids (DCMGs) integrate and coordinate various DC distribution generation units including various renewable energy sources and battery storage systems, and have been used in satellites, the International Space Station, telecom power stations, computer power supplies, electric aircraft, and electric ships. However, the presence of constant power loads (CPLs) can cause instability in DCMGs. Thus, this paper reviews the stabilization techniques that can resolve instability caused by CPLs, as well as various parameters of CPLs, such as bandwidth, and the frequency of the CPLs that can stabilize the DCMGs. It also discusses recent trends and future work in finding stability limits using the parameters of CPLs. It should be useful for directing research towards appropriate mathematical and experimental approaches for the stability of DCMGs with CPLs.

AbstractThe current study investigates different methods to minimize the drag coefficient (CD) without ignoring the safety factor related to the stability of a vehicle, i.e., the lift coefficient (CL). The study was carried out by employing an SUV car analyzed numerically using one of the CFD software, Ansys. Four different models such as realizable k–ε, standard k–ω, shear stress transport k–ω, and Reynolds stress model (RSM). The considered models have been validated with experimental data and found in good agreement. The considered inlet velocity varies from 28 to 40 m/s, the results showed that the drag coefficient and the stability are both improved by applying a modification on the roof of the considered car.

AbstractNowadays, engineers and researchers have deeply perceived the application of nano-scale materials and the associated emerging technology so-called nanotechnology (NT) not only to address the existing challenges in all sciences but also to reshape the future of entire industrial world. Recently, NT has been taken into consideration tremendously for energy applications in both conventional and green types of energies. Particularly in the oil and gas industry (OGI) as the current primary energy source, NT implementation has attracted enormous attentions by researchers and companies due to increasing numerous articles that have been published every year. In this review article, an up-to-date benefits of NT applications in OGI including upstream, midstream, and downstream were highlighted. Besides, the main challenges in oil and gas fields have been discussed to show the potential of NT to overcome the obstacles. Finally, outcomes of several studies were traced in higher efficiency to demonstrate NT application in all OGI sections, and the field trials were summarized as well.

Abstract Since 1992, the United Nations Framework Convention on Climate Change (UNFCCC), the global governing apparatus of climate planning, has privileged the sovereignty of territorial states. Contemporary political geographical scholarship has since called into question the coherency of the state as a unitary entity and as the sole legitimate arbiter of international politics. This article extends these contributions to planetary climate change adaptation. Through discourse analysis and the multi-scalar institutional and political history of climate planning, this article examines how normative discursive parameters enact prevailing political dynamics that script material futures. Drawing on recent climate planning reports of Palestine and Israel, this article investigates how state discourses operate within an asymmetric geopolitical context where issues of territoriality, sovereignty, and statecraft remain fractured and contested. Climate planning in Israel/Palestine exposes two key institutional constraints of climate governance. First, technical-managerial principles prescribe ahistorical adaptation measures that inadequately address inherently political constraints. Second, the elision of political-economic and historical-cultural contingencies in favor of a universalizing geophysical representation of climate change elides the systemic production of differentiated vulnerability. Consequential of an anachronistic politics of recognition within the UNFCCC, the conditions of climate governance may ultimately embolden the asymmetric status quo. I conclude by highlighting the spatial manifestations (both material and symbolic) of Israeli sovereign violence and the chronic indeterminacy of Palestinian territoriality produced by discursive climate futures.

Abstract Compared with AC systems, HVDC systems are more flexible and potentially contribute to enhancing system resilience. Currently, three types of HVDC technologies, LCC‐HVDC (Line‐commutated Current‐sourced Converters, LCC), VSC‐HVDC (Voltage Sourced Converter, VSC), and MMC‐HVDC (Modular‐Multilevel‐Converter, MMC), are applied in practical projects. All types of HVDC systems can be applied to stabilize the system frequency of AC power systems and facilitate system recovery after extreme natural events. The operation characteristics, methods, and control strategies of different HVDC technologies for facilitating system operation are reviewed herein; it is indicated that HVDC technology is an effective solution for enhancing system resilience. Renewable resources, energy storage systems, and demand response devices can be coordinated well with HVDC systems. The frequency and voltage regulation ability of power systems and the black start ability can be enhanced by introducing HVDC systems into power systems. Several isolated AC power systems can be connected to HVDC systems. These AC systems can interact with other AC systems through HVDC systems by conforming to their operational characteristics and constraints. The resilience of these AC systems can be enhanced by these interactions. Additionally, related operation methods and control strategies will also be reviewed.

In order to obtain the full impedance characteristics of a lithium-ion capacitor as a function of temperature, the authors proposed the use of dynamic electrochemical impedance spectroscopy. Impedance tests were carried out under wide range of dynamic temperature changes for lithium-ion supercapacitors. Significant differences in electrochemical processes were observed as a result of working temperature. Moreover, the quality of fitting of the equivalent circuits most frequently used in impedance analysis of lithium-ion capacitors was discussed. The proposed methodology allows for a comprehensive characterization of the performance of these devices and provides key information for their optimization in wide range of operations.

The integration of distributed renewable energy (DRE) into grid is experiencing significant growth. Due to its intermittent characteristics, DRE have several impacts on system operation. This integration does not only influence the distribution network, but also it affects the transmission network. This paper analyzes the impact of increased penetration of distributed renewable energy specifically the PV generation on static voltage stability of transmission network and helps to find the maximum allowable capacity of DRE penetration. DRE integration with different weather conditions is studied in this paper. Voltage Collapse Proximity Index (VCPI) is used to evaluate the voltage stability of the system. Simulations are carried out on IEEE-39 bus test system using Power system analysis toolbox (PSAT). It can be concluded that the integration of high level of DRE into the grid affects the voltage stability, and it may lead to voltage collapse. The analysis results can be used to provide guidance for the allowable percentage of DRE integration.