The scientific objective of this study is to demonstrate how a hybrid photovoltaic-grid-generator microsystem responds under transient regime to varying loads and grid disconnection/reconnection. The object of the research was realized by acquiring the electrical magnitudes from the three PV systems (25 kW, 40 kW, and 60 kW) connected to the grid and the consumer (on-grid), during the technological process where the load fluctuated uncontrollably. Similar recordings were also made for the transient regime caused by the grid disconnection, diesel generator activation (450 kVA), its synchronization with PV systems, power supply to receivers, and grid voltage restoration after diesel generator shutdown. Analysis of the data focused on power supply continuity, voltage stability, and frequency variations. Findings indicated that on-grid photovoltaic systems had a 7.9% maximum voltage deviation from the standard value (230 V) and a frequency variation within ±1%. In the transient period caused by the grid disconnection and reconnection, a brief period with supply interruption was noted. This study contributes to the understanding of hybrid system behavior during transient regimes.
The economic viability of a photovoltaic (PV) installation depends on regulations regarding administrative, technical and economic conditions associated with self-consumption and the sale of surplus production. Royal Decree (RD) 244/2019 is the Spanish legislation of reference for this case study, in which we analyse and compare PV installation offers by key suppliers. The proposals are not optimal in RD 244/2019 terms and appear not to fully contemplate power generation losses and seem to shift a representative percentage of consumption to the production period. In our case study of a residential dwelling, the best option corresponds to a 5 kWp installation with surplus sale to the market, with a payback period of 18 years and CO2 emission reductions of 1026 kg/year. Demand-side management offers a potential improvement of 6%–21.8%. Based on the increase in electricity prices since 2020, the best option offers savings of up to €1507.74 and amortization in 4.24 years. Considering costs and savings, sale to the market could be considered as the only feasible regulatory mechanism for managing surpluses, accompanied by measures to facilitate administrative procedures and guarantees for end users.
This study aims to explore the perceptions of the Scholarship of Teaching and Learning (SoTL) of primary and secondary school teachers in C City, China, as well as the challenges they face in developing these abilities. Through narrative inquiry involving five current teachers, the research collected their personal experiences in the development of teaching and academic abilities, with data gathered through semi-structured interviews. The findings reveal that teachers are primarily driven by external forces, professional identity, personal growth, and the need to improve teaching quality in their efforts to enhance teaching and academic abilities. However, they also encounter challenges such as teaching pressures, time management difficulties, insufficient school support, and declining energy. To overcome these obstacles, teachers have adopted strategies such as time management, task allocation, and cognitive enhancement. The study concludes by recommending that through the combined efforts of teachers, schools, and society, a strong professional belief system should be established, and a supportive environment should be created to collaboratively promote the development of teaching and academic abilities among primary and secondary school teachers, thereby fostering their professional growth.
A Dream of Splendor (Menghua lu) TV series brings to life the Song’s (960–1279) prosperity, especially women’s business. So, this paper analyzes how and why women ran shops like teahouses or taverns.
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