PDF Publication Title:
Text from PDF Page: 028
The publ1shed spectra of var10US chrom1um spec1es are shown in figure 30. Spectra of the chrom1um Redox solutions were measured during several charge and discharge cycles by plac1ng the flow cell of the spectrophotometer 1n llne w1th the chromium reservoir. These spectra were analyzed by using a curve resolver to determ1ne the amounts of hexahydrate and pentahydrate. Three examples of the curves are shown in figure 31. In f1gure 31(a) the spectrum of a solution dur1ng charge is shown at 71 percent state of charge. No pentahydrate is present at this p01nt, having been depleted at about 55 percent state of charge. F1gure 31(b) shows the spectrum at 88 percent state of charge, where the charging was terminated. Figure 31(c) shows the spectrum during d1scharge, at 70 percent state of charge. Compar1son with f1gure 31(a) at the same state of charge shows that the peaks are higher and shifted toward longer wavelengths as a result of the pentahydrate being pro- duced in the discharge reaction, rather than the hexahydrate. These data prove, as expected, that the observed color changes and voltage changes are indeed due to the chromium (III) pentahydrate being depleted first on charging the cell and being produced f1rst on discharge. The observed composition changes are summarized in figure 32. Summary. - Cyclic voltammetry has been used successfully to develop acceptance cr1teria for chromium electrodes. Over 200 electrodes have been tested. Results 1n laboratory cells and full-size slngle cells and stacks are in accord with the cyclic voltammetry results. Spectrophotometric and CYCllC voltammetry stud1es have conf1rmed the expectat10ns that the cause of slow charging behavi~2 and open-circuit voltage hY~5eresis is the depletion of [Cr(H20)5Cl] ,leaving [Cr(H20)6] ,which 1S reduced more slowly and accompan1ed by greater hydrogen evolution. For the system to be charged at a more rapid rate, either a better catalyst for the reduction of the hexahydrate or a catalyst for the more rapld equll1bration of the hexahydrate and pentahydrate must be found. Work will be carrled out in this direct10n during the comlng year. F1gure 33 dlsplays the major milestones associated with this activity. Single-Cell and Stack Performance Background Continuous flow of the reactant Solutlons is one of the inherent fea- tures of the NASA Redox energy storage system. Assoc1ated with this con- tlnuous flow are pressure drop losses, both in the cells composlng the Redox stack and in the associated plumbing between the stack and storage tanks. Pumping requirements are a dlrect parasit1c energy loss to the Redox system Slnce cont1nuous flow 1S necessary throughout the charge and d1scharge por- t10ns of a cycle. The larger the pressure drop in a specific system, the larger the pumping requlrements. Another character1stic, shunt currents, also represents a parasit1c energy loss to the system. Shunt currents are caused by electrolytic paths in the fluid between cells at different poten- tials in a Redox stack. They are manlfested as a self-discharge mechanism 25PDF Image | NASA Redox Storage System Development Project 1980
PDF Search Title:
NASA Redox Storage System Development Project 1980Original File Name Searched:
19830006412.pdfDIY PDF Search: Google It | Yahoo | Bing
Salgenx Redox Flow Battery Technology: Power up your energy storage game with Salgenx Salt Water Battery. With its advanced technology, the flow battery provides reliable, scalable, and sustainable energy storage for utility-scale projects. Upgrade to a Salgenx flow battery today and take control of your energy future.
CONTACT TEL: 608-238-6001 Email: greg@salgenx.com (Standard Web Page)