Zinc–Bromine Flow Batteries
With all the hype and fanfare surrounding the release of the Tesla Powerwall the average energy storage consumer could be forgiven for thinking lithium-ion batteries and Powerwall are the only game in town for solar storage, yes there are other battery manufactures and battery types, one of these is the Zinc–bromine flow battery.
Zinc–bromine flow batteries are a type of hybrid flow battery. Zinc bromide is stored in two tanks, when the battery is charged or discharged the solutions (electrolytes) are pumped through a reactor stack and back into the tanks. One tank stores the electrolyte for the positive electrode and the other tank is the negative.
The main characteristics of zinc bromine batteries
- High energy density relative to lead–acid batteries.
- Capable of 100% daily discharge.
- No shelf life limitations as zinc–bromine batteries are non-perishable.
- Scalable capacities.
Redflow Flow Batteries
In Australia the leading manufacturer of zinc-bromide flow batteries is a company named Redflow. Redflow's head office is located in Seventeen Mile Rocks, Brisbane with global offices in the USA and Europe.
One example of Redflow's product is the ZCell Flow Battery pictured below.
Redflow ZCell Characteristics
- Type - Zinc-bromide flow.
- Can be used off-grid.
- 30000 kilowatt-hours or 10 year warranty.
- Operating temp 15℃ to 50℃.
- Weight 240kg.
- 3.0 kilowatts continuous power.
- 10 kilowatt-hours usable storage capacity.
- 10 kilowatt-hours nominal storage capacity.
ZCell Sustained Storage Capacity
A ZCell battery can be completely discharged every day without any loss of recharge capability which is in contrast to other battery types such as lithium-ion, and has an expected service life of around 14 years.
Disadvantages of Zinc-bromide batteries.
- Lower efficiency compared to lithium-ion batteries.
- For maintenance reasons a full discharge and shut down is required every week.
- Need to be installed outdoors.
- Much larger and heavier than other battery types.
- Power output can be lower per kWh of storage than some lithium-ion batteries.