As complex as the modern energy system can get, the ultimate goal of system operators remains the same: keep the lights on.

When the transmission network first came to be, this was achieved through a series of electricity generators spinning at fifty rotations per second (50Hz). This meant local networks were required to synchronise at 50Hz to connect up and form the national transmission network.

All the systems that have followed – from household appliances to industrial machinery – are dependent on this power running smoothly. Too much supply and the grid electricity frequency will rise, potentially causing short circuits. Too much demand, on the other hand, will lower the frequency and cause systems failure.

Keeping this balance within tight tolerances is, therefore, key to successful operations. It’s also increasingly being achieved using energy storage to support the network. Without this help, network operators may resort to blackouts in local areas to prevent the whole network falling over.

On Monday 22 November, Gore Street’s Drumkee and Mullavilly energy storage stepped in to prevent such an incident after measuring a fall in grid frequency. The combined electricity system of the Republic of Ireland and Northern Ireland operates within normal operating limits of 49.9Hz to 50.1Hz and, on this particular day, our energy storage stepped in to maintain stability after measuring a drop below the trigger threshold of 49.8Hz.