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Use of Balancing Mechanism doubles as COVID-19 highlights imperfect system

Image: Andy Beecroft.

Image: Andy Beecroft.

The Balancing Mechanism (BM) was used twice as much throughout April and May 2020 as the previous year, due to the impact of COVID-19.

Over the two months 7.1TWh of actions were accepted on the BM, more than double the 3.3TWh in April and May 2019, according to Cornwall Insight.

This was driven by the record low demand caused by the COVID-19 lockdown over the past few months. In particular, bank holiday weekends during May has sent demand tanking as renewables such as solar have posted record high generation.

Lee Drummee, analyst at Cornwall Insight, said that many of the actions in the BM have been taken not to balance demand however, but to manage an imperfect system.

“For example, the ESO is frequently required to turn down the output from Scottish generators on windy days due to insufficient transmission capacity to transport the electricity south.

“On similar days, with high levels of asynchronous generation and low demand levels, the ESO also needs to ramp up output from synchronous generators (typically CCGT plant). By doing this the ESO maintains adequate levels of system inertia, preventing large and speedy deviations in frequency.”

Image: Cornwall Insight.
Image: Cornwall Insight.

But there is no doubt demand has impacted the system, with National Grid ESO calling on a host of tools in its toolbox to tackle such periods alongside the BM. This includes the operator's new Downward Flexibility Management service, which has been brought in to reduce embedded generation during periods of low demand.

Additionally, an urgent Grid Code modification was approved ahead of the second bank holiday in May to avoid the threat to the grid of low demand, however it was not used over the weekend.

With renewables hitting new generation records, such as solar, which reached a peak of 9.68GW at around 12:30 on Monday 20 April 2020, breaking the all-time peak generation record and meeting almost 30% of UK electricity demand. The BM along with other tools have been key for the stability of the grid during the lockdown period.

“The increase in offer volumes alongside higher bid volumes during this low demand period indicates that more significant volumes of actions are being taken to resolve other system issues too.

“May 2020 saw 0.28TWh of wind generation turned down on the BM compared to 0.06TWh in the same month of 2019. While an increase in installed wind capacity has predominantly seen a rise in activity, accepted volumes have been exacerbated in recent months with demand at historic lows.

“It will be interesting to see how the easing of lockdown restrictions impacts activity in the BM going forwards, or if the operational challenges will remain at current levels.”

The lockdown period has been hailed by many as a taste of the future, showing how we can manage a grid dominated by renewable generation. However, many suppliers are concerned at the surging cost of balancing, with Balancing Services Use of System (BSUoS) costs predicted to be £500 million higher than normal for this period.

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