摘要 :
The rapid growth of the world economy,the day-to-day development of science and technology,and the continuing progress of living standards in modern society have indeed caused an increase in the need for energy.The widespread usag...
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The rapid growth of the world economy,the day-to-day development of science and technology,and the continuing progress of living standards in modern society have indeed caused an increase in the need for energy.The widespread usage of fossil fuels to meet global energy needs generates thousands of tons of carbon dioxide(CO2)and other pollutants yearly,accelerating global warming and causing significant climate change.Renewable energy sources such as wind,solar,and geothermal energy are viable alternatives to fossil fuels to reduce serious environmental risks.To integrate and distribute energy supply,these renewable energies require effective,advanced,and highly efficient electrochemical energy storage devices.The demand for energy storage devices,for example,lithium/sodium-ion batteries(LIBs/NIBs)for hybrid electric vehicles(HEVs)and autonomous electrical appliances,has increased rapidly over the past decade due to their high power density,long cycle life,extraordinary coulombic efficiencies,minimal memory effects,and environmental friendliness.The typical components of LIBs and NIBs batteries are electrodes(cathode and anode),electrolytes,and a microporous separator.
Microporous membrane separators(MMS)are at the heart of rechargeable LIBs and NIBs because they prevent short circuits and serve as a channel for ion transport during charge-discharge operations.Despite being an inactive section of the battery,the membrane separator''s structure and properties have a significant impact on the battery''s safety,electrochemical performance,and reusability.Regardless of the abundance of commercially available separators,their thermal stability and service life severely limit the battery''s efficiency and reliability.Although no ideal separator can still provide optimal electrochemical performance,and safety under all operating conditions,most efforts to find alternatives to polyethylene(PE)separators have failed because they are still preferable to other separators when all criteria are evaluated.Polyethylene-based membrane separators are favourable for LIBs and NIBs batteries but suffer from inherent hydrophobic behaviour that permits poor electrolyte absorption,and low thermal stability causes an inevitable dimensional shrinkage at high temperatures.Continuous efforts have been made to modify PE separators to increase safety and improve electrochemical performance.In this thesis,we overview the state-of-the-art fundamental requirements and properties of ideal separators for LIBs and NIBs.Correspondingly,in-depth descriptions of the fabrication and development of hybrid composite separators based on porous polyethylene(PE)membranes for rechargeable lithium-ion(Li-ion)andsodium-ion(Na-ion)batteries are provided.
Finally,a novel PE-based membrane modified with a hybrid organic-inorganic coating layer for lithium-/sodium-metal(LMBs/NMBs)batteries is fabricated.The advanced separator is developed by incorporating heat-resistant boehmite(BH)and multipolar self-polymerizing dopamine(DA)into biaxially oriented poly(ethylene)via a facile and in-situ solvent methodology with the help of corona discharge activation and pre-treatment.The advanced separator can promote rapid electrolyte absorption,accelerate Li+/Na+ transference without sacrificing the macrostructure and physiochemical properties of the matrix,and endow excellent dimensional stability(～0％)at temperatures higher than 140℃.LMB cells(Li ‖LiFePO4)employing the hybrid separator endow outstanding life span stability and excellent capacity retention of approximately～88 ％ after 500 cycles at a C-rate of(1C).And the hybrid separator can also operate stably under the sodium metal battery system.This work presents an efficient and scalable strategy for constructing safe,long-life next-generation batteries.
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摘要 :
Micro grids are being another creating innovation operation in two particular methods of activity,in particular,the grid-connected mode and the self-governing(or islanded)mode.On the move from the utility-grid associated mode to t...
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Micro grids are being another creating innovation operation in two particular methods of activity,in particular,the grid-connected mode and the self-governing(or islanded)mode.On the move from the utility-grid associated mode to the independent mode,the frequency of a micro-grid can be truly influenced because of unbalance between power generated and power request and right then and there,micro-sources may react gradually to dispose of this unbalancing circumstance.To fathom this interference and to work the micro grid relentlessly,some quick reaction storage system frameworks,in particular Battery Energy Storage Systems(BESSs)are required.
Integration of Renewable Energy Sources into the Conventional Power plants have been a necessity of today's World to satisfy the heavy demand and to promote the pollution-free environment.Converters play a vital role in controlling the output of these RES's and convert the D.C output power of RES's into A.C usable power.While these converters had gained a huge popularity due to its fast and controllable output power,at the same time it has disconnected the grid frequency from the generator's rotor.This means no control over the grid frequency changes as the generator is unable to provide inertial response,Primary frequency response,and Damping response to the system.
All large generating plant,and groups of smaller generators(such as wind farms),are normally required to have capability to participate in frequency control by supplying an increase in power if frequency drops below,and a decrease in power if frequency increases above a nominal frequency.This is achieved by operation at less than maximum available output in order to provide ability to regulate power production upwards.Generators which do not operate to provide this governor type response will normally still need to provide a high frequency response where active power is gradually reduced above a certain frequency.During low frequency no increase in active power is required,in fact an allowed reduction in power is specified to account for technology dependent characteristics of output power verses frequency for certain types of plant.
Rise in Wind power plants have seen a large growth in recent years.High integration of these Renewable energy sources has greatly influenced today's power system stability.When concerned about the stability,two variables carry a great importance,one is the frequency and the other is the voltage.This thesis will focus on frequency stability.With rise in the Renewable energy sources like Wind farms,and Photovoltaics,there is as equal decrement in the system inertia,and the primary frequency response.These two responses are the most reliable controls in any power system.
This thesis has investigated how the Battery Energy storage system can be a feasible option to the frequency disturbances in a weak distribution grid.Also,ANN proved to be the effective solution to the problem of sizing of BESS for the modem standalone power systems.The investigation was carried on MATLAB by creating a weak distribution grid with a high penetration of Wind power plant.The active output power of BESS was controlled to mimic the IR,PFR,and Damping response as with the CPP.Frequency responses were compared with and without the BESS,which demonstrated the significance of initial responses to the frequency disturbances in a power system.Furthermore,ANN architecture used to determine the size of BESS for standalone grid is compared with the analytical calculations presented in literature,and the results shows that the size of BESS predicted by our trained neural network can effectively change the frequency to its allowable limits.
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