Battery energy storage sites are a crucial part of the transition away from carbon intensive fossil fuels. The electricity grid cannot store electricity, only transmit it. It is therefore crucial to ensure that there is a constant balance of supply to demand: too much supply, and the network gets damaged; too little, there are power cuts.
Historically, fossil-fuel power stations were good at maintaining this balance as the capacity of power generated was predictable and could be controlled. The supply of electricity generated by solar and wind, by contrast, is less predictable.
Batteries help keep the electricity network stable because they export electricity when there is not enough supply and import electricity when there is too much supply.
Battery storage sites typically need to be next to large existing electrical infrastructure such as sub-stations and power stations.