Handbook of Energy Storage for Transmission or ... - W2agz.com

EPRI Proprietary Licensed Material
Regenesys Electricity Storage Technology
Figure 5
Artists Rendition of 10MW/100MWh Regenesys Energy Storage Plant
Regenesys cell stacks consist of bipolar electrode plates spaced and held by insulating polymer
frames, see Figure 2, above. These frames also serve to manifold and distribute the electrolyte
into the cell compartments, which are separated by pieces of membrane material. Innogy uses a
proprietary sealing arrangement between the frames to prevent electrolyte leakage between cell
compartments and out of the stack. As can be seen in Figure 4, the frames holding the electrodes
and the membranes are held together with thick end plates and tie bars, items which are not used
in the United States by Powercell or ZBB, developers of zinc/bromine battery technologies. In
the Innogy approach to a 12MW Regenesys plant, 1200 cell-stacks (100kW each) are arranged in
a parallel and series array for a plant DC voltage of ~3000V. Shunt currents can flow in the
hydraulically-parallel flow channels of cells in electrical series, with these shunt currents being
limited in all flow batteries by using flow channels that are long enough and narrow enough to
provide an effective limiting resistance. However, extra pumping power losses are thereby
introduced that must be balanced with the reduction in shunt current losses than can be effected.
Shunt current and pumping power losses are thus limited to 5-10% in Regenesys ES plants by
suitable arrangements in the plumbing from the two electrolyte tanks to the individual cells of
the cell-stacks.
Plant-wide tanks, rather than modularized units, were used in the design for a variety of reasons,
including the necessity to remove, via a processing unit based on conventional chemical
engineering technology, the sodium sulfate that builds up at a rate of 250-300lbs per day (for a
12MW plant) in the negative electrolyte. Innogy indicates that such considerations also place a
limit, for the next several years at least, on the minimum size plant that can be economically
considered (nominally 100MWh/10MW).
As a result of all the above considerations, the characteristics expected for 100MWh/10MW
Regenesys plant engineered according to the Innogy design approach are as follows:
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