Handbook of Energy Storage for Transmission or ... - W2agz.com
Handbook of Energy Storage for Transmission or ... - W2agz.com
Handbook of Energy Storage for Transmission or ... - W2agz.com
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EPRI Proprietary Licensed Material<br />
Regenesys Electricity <strong>St<strong>or</strong>age</strong> Technology<br />
sulfide solution at the negatives in discharge dissolves in excess sodium sulfide that is present to<br />
<strong>f<strong>or</strong></strong>m sodium polysulfide. The bromine produced at the positives in charge dissolves in excess<br />
sodium bromide to <strong>f<strong>or</strong></strong>m sodium tribromide. Unlike the situation in zinc/bromide batteries, the<br />
bromine active material remains in solution in the tribromide ion <strong>f<strong>or</strong></strong>m until it is consumed by the<br />
discharge reaction at the positives. Note also that the electrolyte <strong>f<strong>or</strong></strong> the positive electrodes is<br />
relatively inexpensive, and that used in the negative <strong>com</strong>partments <strong>of</strong> the cells is very<br />
inexpensive. A block diagram <strong>of</strong> a Regenesys energy st<strong>or</strong>age plant is shown in Figure 1. 1<br />
Figure 1<br />
Flow Schematic <strong>of</strong> Regenesys Electricity <strong>St<strong>or</strong>age</strong> System<br />
The cation-exchange membranes that are a vital part <strong>of</strong> the electrochemical operability <strong>of</strong><br />
Regenesys batteries serve to separate the differing electrolytes in the positive and negative<br />
<strong>com</strong>partments <strong>of</strong> each cell, yet provide a path <strong>f<strong>or</strong></strong> the passage <strong>of</strong> sodium ions. A rupture <strong>of</strong> a<br />
membrane in one <strong>of</strong> the cells will allow the electrolyte in the positive <strong>com</strong>partments and that in<br />
the negative <strong>com</strong>partments to mix together. This mixing is undesirable, so the Innogy<br />
technology based on this chemistry includes measures to detect and isolate any membrane<br />
ruptures. Even when operating properly, no membrane is 100% effective, <strong>of</strong> course, so the<br />
coulombic efficiency <strong>of</strong> Regenesys cells is typically 99%, and some material can pass from one<br />
side <strong>of</strong> the membranes to the other, thereby causing a build up <strong>of</strong> a sodium sulfate in the<br />
1 Unless otherwise noted, all figures, diagrams and photos in this chapter are credited to Innogy/Regenesys<br />
Technologies, Ltd., which <strong>or</strong>ganization retains the copyright thereto. These graphics were downloaded from<br />
www.regenesys.<strong>com</strong>, and this acknowledgment is included in the current document as required as a condition <strong>of</strong><br />
downloading and reproduction. There is no mention that specific auth<strong>or</strong>ity to reproduce these graphics is required.<br />
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