http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
다공성 전극의 압축률이 레독스흐름전지의 성능에 미치는 영향
정승훈 ( Seunghun Jung ),정대인 ( Daein Jeong ) 한국액체미립화학회 2016 한국액체미립화학회 학술강연회 논문집 Vol.2016 No.-
Research on renewable energy such as solar, wind, and hydropower is being accelerated to resolve environmental problem and fossil fuel depletion problem. Most of renewable energies, however, have a limitation such that they cannot immediately respond to the power load because of their irregular power production. To compensate this problem, energy storage systems (EES) is indispensable. Redox flow batteries (RFB) have attracted attention as a strong candidate for future ESS in recent years. RFBs produce or store electric energy in liquid electrolyte by means of electrochemical reaction in electrodes where redox couples react together (see Fig. 1). According to the redox couple, there are several types of RFBs such as Zinc/Bromine RFB, All-vanadium RFB, Fe/Cr RFB. Among them, allvanadium redox flow battery (VRFB) is considered to be closest to commercialization. VRFB uses vanadium ions in both electrolytes (in the negative electrolyte: V<sup>2+</sup>,V<sup>3+</sup> in the positive electrolyte:VO<sup>2+</sup>, VO<sup>+</sup>). Because same reactant (vanadium) is used in both electrodes, VRFB can easily recover its performance even though the electrolyte is contaminated by reactant crossover. Furthermore, VRFB can sustain very long operational life time because it does not require catalyst in electrodes. In the present study, the compression effect of porous electrodes on the performance of VRFB is computationally investigated. To predict the performance and physico-chemical behavior of VRFB, multi-dimensional, computational models are developed. Several battery design parameters such as cross-sectional area of the flow inlet, the electrode porosity, reaction area of electrode, ionic and electronic conductivity are influenced by electrode compression, which results in mass transport, electric resistance and flow characteristics of VRFB. The present multi-dimensional VRFB model is composed of four coupled partial differential equations, which are simultaneously solved by means of computational fluid dynamics technique. Preliminary charging and discharging performance of a unit VRFB is presented in figure 2 when the carbon-felt electrodes (4mm thickness and 0.95 of porosity) are compressed from 0% to 50%. Basic observation reveals that increasing the compression ratio leads to large ionic resistance of electrodes, which results in lower capacity utilization through this study. Also, higher compression ratio causes large pressure gradient in thru-electrode direction. This pressure gradient brings about severe convective crossover of vanadium ions through the membrane.
다공성 전극의 압축률이 레독스흐름전지의 성능에 미치는 영향에 대한 수치해석적 연구
정대인 ( Daein Jeong ),정승훈 ( Seunghun Jung ) 한국액체미립화학회 2017 한국액체미립화학회지 Vol.22 No.2
When designing a redox flow battery system, compression of battery stack is required to prevent leakage of electrolyte and to reduce contact resistance between cell components. In addition, stack compression leads to deformation of the porous carbon electrode, which results in lower porosity and smaller cross-sectional area for electrolyte flow. In this paper, we inves-tigate the effects of electrode compression on the cell performance by applying multi-dimensional, transient model of all-vanadium redox flow battery (VRFB). Simulation result reveals that large compression leads to greater pressure drop through-out the electrodes, which requires large pumping power to circulate electrolyte while lowered ohmic resistance results in bet-ter power capability of the battery. Also, cell compression results in imbalance between anolyte and catholyte and convective crossover of vanadium ions through the separator due to large pressure difference between negative and positive electrodes. Although it is predicted that the battery power is quickly improved due to the reduced ohmic resistance, the capacity decay of the battery is accelerated in the long term operation when the battery cell is compressed. Therefore, it is important to opti-mize the battery performance by taking trade-off between power and capacity when designing VRFB system.