PDF Publication Title:
Text from PDF Page: 062
and are valid for a single electrode [73]: Rdist=bρ1+ρ2+b ρ1ρ2 3 3(ρ1 +ρ2) (3.54) (3.55) (3.56) 3.6. Electrochemical Impedance Spectroscopy Rct = ART AtnFi0 Rfd= AaRT 1 Atfgn2F 2 cRedDRed + 1 cOxDOx To model the impedance of flow cells, the porous impedance of the electrodes is paired in series with a resistor (to represent the resistance from membrane, contacts, etc.) and an inductor (to represent the inductance from cell cables). In the case of a full cell confi- guration, the analysis becomes quite complicated due to the large number of parameters involved. The impedance of one electrolyte at a time can instead be investigated by using a one-container symmetric cell configuration. Sun et al. [72] and Pezeshki et al. [73] used this method to study the V2+/V3+ redox reaction in symmetric vanadium flow cells. Considering a symmetric configuration where the porous impedance of each electrode is equal, the total cell impedance is modelled according to Equation 3.57. The corresponding equivalent circuit diagram is shown in Figure 3.18. Zcell,model = 2 × Zp(ω) + Rs + jωL (3.57) L Rs TL TL Figure 3.18: Schematic of the equivalent circuit used to model symmetric flow cells. Each TL element represents the transmission line model presented in Figure 3.16. 3.6.3 Modelling Once a proper model has been selected for the studied system, the model equations are fitted to the experimentally obtained data. This is generally done through a complex non-linear least squares (CNLS) minimisation algorithm, which involves minimising the sum of squared residuals between experimental data and model. The objective function is presented in Equation 3.58 [67]: N S(p) = i=1 Zdata − Zmodel(p)2 i,Re i,Re wi,Re + Zdata − Zmodel(p)2 i,Im i,Im (3.58) wi,Im where Zi is the real (Re) or imaginary (Im) part of either the experimental data or model, p is the set of free model parameters to be optimised, and wi is the weighting factor. The minimisation process is often carried out using the iterative Levenberg–Marquardt algorithm [67], which must be supplied with a set of initial values for the free model parameters. The algorithm works best if values close to the best fit values are passed, as the iteration process can get stuck in a local minimum far from the global minimum. 41PDF Image | Organic Redox Flow Batteries 2023
PDF Search Title:
Organic Redox Flow Batteries 2023Original File Name Searched:
PhD_thesis_final_dorhoff_4_.pdfDIY PDF Search: Google It | Yahoo | Bing
Salgenx Redox Flow Battery Technology: Salt water flow battery technology with low cost and great energy density that can be used for power storage and thermal storage. Let us de-risk your production using our license. Our aqueous flow battery is less cost than Tesla Megapack and available faster. Redox flow battery. No membrane needed like with Vanadium, or Bromine. Salgenx flow battery
CONTACT TEL: 608-238-6001 Email: greg@salgenx.com (Standard Web Page)