Environmental Engineering Reference
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VR batteries are only considered where versatility is important, such as the inte-
gration of renewable resources.
4.5.1.2 Cost of VR fl ow battery
There are two costs associated with fl ow batteries: the power cost (kW), and the
energy cost (kWh), as they are independent of each other. The power cost for VR
batteries is $1828/kW, and the energy cost is $300/kWh to $1000/kWh, depending
on system design [ 3 ].
4.5.1.3 Disadvantages of VR fl ow battery
VR batteries have the lowest power density and require the most cells (each cell
has a voltage of 1.2 V) in order to obtain the same power output as other fl ow bat-
teries. For smaller-scale energy applications, VR batteries are very complicated in
relation to conventional batteries, as they require much more parts (such as pumps,
sensors, control units) while providing similar characteristics. Consequently,
when deciding between a fl ow battery and a conventional battery, a decision must
be made between a simple but constrained device (conventional battery), and a
complex but versatile device (fl ow battery).
4.5.1.4 Future of VR fl ow battery
VR batteries have a lot of potential due to their unique versatility, specifi cally their
MW power and storage capacity potential. However, the commercial immaturity
of VR batteries needs to be changed to prove it is a viable option in the future.
4.5.2 PSB fl ow battery
PSB batteries operate very similarly to VR batteries. The unit is made up of the
same components; a cell stack, electrolyte tank system, control system and a PCS
(see Fig. 11). The electrolytes used within PSB fl ow batteries are sodium bromide
as the positive electrolyte, and sodium polysulphide as the negative electrolyte.
Figure 11: Polysulphide bromide fl ow battery [ 3 ].
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