Empirical analysis on Shanxi electric energy efficiency by DEA model

AbstractElectric energy generation from falling droplets has seen a hundred-fold rise in efficiency over the past few years. However, even these newest devices can only extract a small portion of the droplet energy. In this paper, we theoretically investigate the contributions of hydrodynamic and electric losses in limiting the efficiency of droplet electricity generators (DEG). We restrict our analysis to cases where the droplet contacts the electrode at maximum spread, which was observed to maximize the DEG efficiency. Herein, the electro-mechanical energy conversion occurs during the recoil that immediately follows droplet impact. We then identify three limits on existing droplet electric generators: (i) the impingement velocity is limited in order to maintain the droplet integrity; (ii) much of droplet mechanical energy is squandered in overcoming viscous shear force with the substrate; (iii) insufficient electrical charge of the substrate. Of all these effects, we found that up to 83% of the total energy available was lost by viscous dissipation during spreading. Minimizing this loss by using cascaded DEG devices to reduce the droplet kinetic energy may increase future devices efficiency beyond 10%.

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Analysis on the Operational Efficiency of Urban Commercial Banks in Guangdong-Hong Kong-Macao Greater Bay Area -Empirical Analysis Based on DEA Model and Malmquist Index-

Korean-Chinese Social Science Studies ◽

10.36527/kcsss.19.3.9 ◽

2021 ◽

Vol 19 (3) ◽

pp. 162-184

Author(s):

Dan Zhang ◽

Xu Jin ◽

Sang Do Park

Keyword(s):

Hong Kong ◽

Empirical Analysis ◽

Commercial Banks ◽

Malmquist Index ◽

Operational Efficiency ◽

Dea Model ◽

Bay Area

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Study of power transformer loading in rural power supply systems

Safety and Reliability of Power Industry ◽

10.24223/1999-5555-2020-13-4-282-289 ◽

2021 ◽

Vol 13 (4) ◽

pp. 282-289

Author(s):

I. V. Naumov ◽

D. N. Karamov ◽

A. N. Tretyakov ◽

M. A. Yakupova ◽

E. S. Fedorinovа

Keyword(s):

Energy Efficiency ◽

Power Supply ◽

Rural Areas ◽

Power Transformer ◽

Electric Energy ◽

Power Transformers ◽

Electric Networks ◽

Load Factors ◽

Optimal Load ◽

Supply Systems

The purpose of this study is to study the effect of loading power transformers (PT) in their continuous use on their energy efficiency on a real-life example of existing rural electric networks. It is noted that the vast majority of PT in rural areas have a very low load factor, which leads to an increase in specific losses of electric energy when this is transmitted to various consumers. It is planned to optimize the existing synchronized power supply systems in rural areas by creating new power supply projects in such a way as to integrate existing power sources and ensure the most efficient loading of power transformers for the subsequent transfer of these systems to isolated ones that receive power from distributed generation facilities. As an example, we use data from an electric grid company on loading power transformers in one of the districts of the Irkutsk region. Issues related to the determination of electric energy losses in rural PT at different numerical values of their load factors are considered. A computing device was developed using modern programming tools in the MATLAB system, which has been used to calculate and plot the dependence of power losses in transformers of various capacities on the actual and recommended load factors, as well as the dependence of specific losses during the transit of 1 kVA of power through a power transformer at the actual, recommended and optimal load factors. The analysis of specific losses of electric energy at the actual, recommended and optimal load factors of PT is made. Based on the analysis, the intervals of optimal load factors for different rated power of PT of rural distribution electric networks are proposed. It is noted that to increase the energy efficiency of PT, it is necessary to reduce idling losses by increasing the load of these transformers, which can be achieved by reducing the number of transformers while changing the configuration of 0.38 kV distribution networks.

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