Flexibility response triggered by drop in grid frequency to 49.59Hz
Image: Getty

Flexibility providers called on by National Grid ESO jumped into action in response to grid frequency falling to 49.59Hz.

Last Thursday saw a drop in grid frequency that resulted in frequency responses from storage assets, with the event peaking at 8:53am. The system price hit £98/MWh at 9:15am, triple the £30.40/MWh it was previously sitting at.

Whilst 49.59Hz is within National Grid ESO’s 49.5-50.5Hz limit, frequency did fall out of its normal operating target of remaining within 0.2Hz of 50Hz.

A graph illustrating the drop in frequency. Image: Social Energy

A graph illustrating the drop in frequency. Image: Social Energy

Social Energy’s batteries were called upon by the System Operator during the event, which Stephen Day, Chief Technical Officer at Social Energy, said was significant due to the frequency response coming from residential batteries.

“Traditionally, these kinds of services would be provided by industrial and commercial customers with fairly big plants, either loads that can be turned on and off or backup generators that can be turned on.

“In this case it was batteries in people’s homes that were essentially providing the same service. So that means that homeowners can start to benefit from the kind of payments that would otherwise go to other providers of these services,” Day continued.

Energy aggregator Limejump said a battery facility was called upon during the event, as well as pumped-storage hydroelectric assets Dinorwig Power Station and Cruachan Power Station..

A similar drop in frequency occurred last month due to the French interconnector tripping, causing grid frequency to fall to 49.63Hz.

National Grid ESO confirmed that this latest frequency drop was not due to an interconnector tripping but did not provide any further information.

System prices also spiked at the end of June, hitting £375MW/h for over an hour due to a run on coal generation units.