Optimal utilization of frequency ancillary services in modern power systems

The widespread global adoption of wind energy sources has established a significant presence in the existing power grid. However, the massive integration of intermittent wind energy poses forecasting errors, prompting the need for supplementary reserves from conventional energy sources with increased operational expenses and carbon emissions. Hence, to facilitate the seamless operation of large-scale wind-integrated power grids, it is imperative to harness the potential of renewable energy sources and leverage flexible loads to deliver power-balancing services. In this research, dynamic real-time power dispatch strategies have been developed for the Automatic Generation Control (AGC) system to integrate the reserve capacities of conventional generation units and wind power plants and utilize the demand response capabilities of flexible loads for power balancing services. A comprehensive power system grid model was developed in DigSilent PowerFactory software, consisting of coal-based energy systems, wind energy systems, gas turbines, and cold storage units as flexible loads. The study is divided into different case studies to assess the impact of each scenario on system operation in mitigating the forecasting errors of wind power plants. Further, a comparative analysis was performed to illustrate the effectiveness of each case study. The analysis showed that Case Study III, where reserves are provided by coal energy systems and cold storage units, yielded the highest reduction in Positive Regulation (PR) and Negative Regulation (NR) errors, at 89.0% and 94.15%, respectively. Conversely, Case Study IV demonstrated the least reduction in errors, with 67.82% in PR and 78.41% in NR. However, it indicates that reserves can be supplied from wind energy systems and flexible loads without the support of conventional power plants

Enhancing Grid Operation with Electric Vehicle Integration in Automatic Generation Control

Wind energy has been recognized as a clean energy source with significant potential for reducing carbon emissions. However, its inherent variability poses substantial challenges for power system operators due to its unpredictable nature. As a result, there is an increased dependence on conventional generation sources to uphold the power system balance, resulting in elevated operational costs and an upsurge in carbon emissions. Hence, an urgent need exists for alternative solutions that can reduce the burden on traditional generating units and optimize the utilization of reserves from non-fossil fuel technologies. Meanwhile, vehicle-to-grid (V2G) technology integration has emerged as a remedial approach to rectify power capacity shortages during grid operations, enhancing stability and reliability. This research focuses on harnessing electric vehicle (EV) storage capacity to compensate for power deficiencies caused by forecasting errors in large-scale wind energy-based power systems. A real-time dynamic power dispatch strategy is developed for the automatic generation control (AGC) system to integrate EVs and utilize their reserves optimally to reduce reliance on conventional power plants and increase system security. The results obtained from this study emphasize the significant prospects associated with the fusion of EVs and traditional power plants, offering a highly effective solution for mitigating real-time power imbalances in large-scale wind energy-based power systems

Towards low-dimensional hole systems in Be-doped GaAs nanowires

GaAs was central to the development of quantum devices but is rarely used for nanowire-based quantum devices with InAs, InSb and SiGe instead taking the leading role. p-type GaAs nanowires offer a path to studying strongly-confined 0D and 1D hole systems with strong spin-orbit effects, motivating our development of nanowire transistors featuring Be-doped p-type GaAs nanowires, AuBe alloy contacts and patterned local gate electrodes towards making nanowire-based quantum hole devices. We report on nanowire transistors with traditional substrate back-gates and EBL-defined metal/oxide top-gates produced using GaAs nanowires with three different Be-doping densities and various AuBe contact processing recipes. We show that contact annealing only brings small improvements for the moderately-doped devices under conditions of lower anneal temperature and short anneal time. We only obtain good transistor performance for moderate doping, with conduction freezing out at low temperature for lowly-doped nanowires and inability to reach a clear off-state under gating for the highly-doped nanowires. Our best devices give on-state conductivity 95 nS, off-state conductivity 2 pS, on-off ratio ~$10^{4}$, and sub-threshold slope 50 mV/dec at T = 4 K. Lastly, we made a device featuring a moderately-doped nanowire with annealed contacts and multiple top-gates. Top-gate sweeps show a plateau in the sub-threshold region that is reproducible in separate cool-downs and indicative of possible conductance quantization highlighting the potential for future quantum device studies in this material system

Factors affecting consumers preferences on fast food items in Bangladesh

This article was published in Journal of Applied Business Research (JABR) [© 2010 Journal of Applied Business Research (JABR)] and the definite version is available at : http://cluteinstitute.com/ojs/index.php/JABR/article/view/313/303 The article website is at: http://www.cluteinstitute.com/journals/journal-of-applied-business-research-jabr/ DOI: http://dx.doi.org/10.19030/jabr.v26i4.313Fast food industry is a high growing sector of Bangladesh. It is concerned with the tastes and habits of the people. The food-taking habit especially in fast food segment has been changing very fast over last decade among the people of Dhaka - the capital city of Bangladesh. The reasons could be attributed by the increase of awareness, growth of education, development of information technology, and expansion of television channels and print media in Bangladesh. Hence, this paper aims at identifying the preference factors of fast food consumers living in Dhaka city. This study was conducted among the university students who usually eat fast food at their leisure time. To conduct the study, a total of 250 respondents were interviewed with a structured questionnaire. Both descriptive and inferential statistics were used in analyzing the data. Multivariate analysis technique like factor analysis was performed to identify the preference factors of the fast food student-consumers of Bangladesh. Multiple regressions were run to identify the relationship between the factors identified and the overall preference of the consumers. Results show that the consumers give most importance on brand reputation of the food item followed by nearness to receive and accessibility, similarity of taste with previous experience, cost and quality of the food, discount and taste, cleanliness and hygiene, salesmanship and decoration, fat and cholesterol level, and self-service factors. This study suggests that the brand reputation, nearness and accessibility, similarity in taste, and cost and quality relationship should be emphasized to improve the attraction of the university students towards the fast food items in Bangladesh.Publishe

Drying techniques differentially affect bark beetle weight change

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