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

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Technology Description
Introduction
The Regenesys electricity storage system of RWE’s subsidiary Innogy (formerly National
Power) of the United Kingdom is a flow battery, i.e., a battery in which one or more of the
reactants or products is stored in a tank (or tanks) external to the battery cells and is passed with
a pump from the tank(s) to the electrode(s) in the cells. Other flow batteries that are under
development include those based on the zinc/bromine and vanadium redox chemistries.
Flow batteries have a number of inherent advantages including:
• Of being easily thermally managed, so that life and performance can be maximized;
• Of being amenable to use of bipolar cell-stack arrangements, so that the costs for highvoltage,
multi-cell batteries can be minimized;
• Of being less affected by overcharge, overdischarge and partial state-of-charge cycling, as
compared to most other batteries, so that they can be used in applications of interest to
electric utilities without life degradation;
• Of having a means to chemically manage the electrolyte(s) for the entire battery, so that, for
example, individual cell watering, as is required for flooded lead acid or nickel cadmium
cells, is not required.
Counterbalancing these advantages are some disadvantages that result from using flowing
electrolytes, and the pumps that are required to effect the flow, as follows:
• The pumps and plumbing add complexity and cost to the battery;
• Flow batteries are more prone to leakage than other systems, because of the plumbing that is
obviously required;
• They have extra, non-electrochemical components that may occasionally need repair; this
implies that there could be additional maintenance costs to affect any required repairs to the
auxiliary equipment, as compared to batteries without such auxiliary equipment.
• They have lower than desirable efficiency, because of the energy consumed to provide the
flowing electrolytes; thus operating costs may be higher for flow batteries than for batteries
based on more conventional chemistries.