Energy Storage Systems (BESS) – Frequency Response

What is system frequency?

System frequency is a constantly changing variable consisting of the real time balance between system demand and total generation. If demand is greater than generation, the frequency falls while if generation is greater than demand, the frequency rises.

Within the UK, the National Grid has a licence obligation to keep frequency within the limits specified in the ‘Electricity Supply Regulations’, i.e. ±1% of nominal system frequency (50.00Hz). National Grid must therefore ensure that sufficient generation and / or demand is held in automatic readiness to manage all credible circumstances that might result in the frequency exceeding the limits.

UK frequency

Monitoring of UK Frequency showing fluctuations


What do Energy Storage Systems have to do with Frequency?

Energy Storage Systems can be used by the National Grid to increase the frequency (i.e. when events such as power stations going offline occur). Battery energy storage systems can respond very quickly to requests from the Grid, which is critical as this needs to occur in less than 2 seconds. The other Frequency Response systems in place are not as quick as they involve power generators increasing their output, which although relatively quick (i.e. minutes) is not quick enough.


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