The interim report[1] published by National Grid ESO into the cause, response and impact of the widespread blackout on the 9 August gives a very clear account of the mechanics of what happened. Overall the message given is that, within the operating parameters that had been set, the system worked as intended. The unexpected impacts were largely the consequence of how some consumer assets, such as Thameslink trains, responded to the frequency drop.

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It would be wrong, however, to conclude that there are few lessons to be learnt from the blackout or that the UK’s energy resilience couldn’t be improved.

As Churchill said, “no crisis should go to waste”, so let’s hope the blackout acts as a further catalyst for innovation and collaboration as we think again about energy resilience. The blackout should be a prompt for a more holistic review of how the UK energy system operates, how it is changing, and what can be done to make it smarter and better equipped to handle the unexpected.

The good news is that there is already a lot of work in progress across the ESO, distribution networks, and supply chain companies looking at these issues. Good examples can be found on the Electricity Networks Association’s (ENA) website and the National Grid ESO Stability Pathfinder[2] programme.

The list below gives our starter-for-ten of some of the areas that have been identified by Regen and our members with high potential for fresh ideas and innovation to improve grid resilience:

  • Should we have more frequency response capacity on standby? There is, of course, a cost trade-off here but at first sight, it looks as if we are running the electricity network on a very tight frequency margin. The blackout showed the impact of two plants coming offline plus the knock-on impact of another 500 MW of embedded generation. Given that the cost of Frequency Response (FR) contracts have plummeted, a short-term expedient would be to increase the provision of FR services.


  • Smarter frequency response and inertia measurement. There is scope to improve the way FR is provided in relation to the mix of generation and demand at any point in time and, crucially, the amount of system inertia. Accurately measuring system inertia has been on the innovation agenda for some time[3]. In fact, the UK is leading in this area, and it is positive that the ESO has now signed contracts for software development and a partnership with GE.[4]


  • The importance of inertia. There appear to be lots of potential solutions to provide new forms of digital and synthetic inertia (see for example report by Everoze[5]) and plenty of pilot projects both in the UK and elsewhere. The opportunity for storage and renewable energy assets to provide their own inertia should be explored and the UK should definitely put itself in a leadership position in this field.


  • Supporting the deployment of battery storage. Battery storage, because of its rapid response capability, can provide a range of energy system services. As our previous blog[6] highlighted, there are now over 150 consented battery projects (of over 3.5 GW capacity) which are currently stuck in the development pipeline because of revenue uncertainty. We are not suggesting that all of these projects be built but unlocking this pipeline should be a priority for policymakers and the ESO.


  • Harnessing the potential of rapid response assets. Regen and our energy storage partners have been pushing for some time that the full potential of battery storage should be harnessed. For example, rather than just increasing the capacity of assets dedicated to providing an FR service would it be possible to make better use of storage assets that may be available outside the terms of an FR contract. These bridging assets could provide very fast response services to recover frequency on the electricity network until other generating assets can be brought on-line. Is there a case for a “non-standby network stability service”? In other words, a new service whereby assets are not required to be on stand-by but have an agreement place that, if they are available, they can (automatically) be called upon to provide fast response services at a certain frequency trigger. Such a service could be called upon when front-line FR fails to ensure frequency stability before a Low Frequency Demand Disconnection (LFDD) process is instigated.


  • Making embedded generation more resilient. The interim report highlights that 500 MW of embedded generation dropped out of the system adding to the frequency excursion. The reason that so much embedded generation took itself off-line is probably due to the Loss of Mains (LoM) tolerance settings used on sites which, if they were commissioned before February 2018, have a relatively narrow frequency tolerance. This potentially makes the loss of embedded generation on the system a significant escalating factor to any frequency drop event. New engineering standards (G99[7]) have been introduced to remedy this situation, but existing embedded generation needs to be addressed. Network operators have been working on this issue[8], but more needs to be done to accelerate this process in order to improve the resilience of embedded generation to frequency changes.


  • Smarter Low Frequency Demand Disconnection. The interim report highlights that the LFDD process worked as anticipated, removing circa 5% of demand from the networks in response to the low frequency trigger. It does seem from the outside that the LFDD process, although very rarely used, could be improved. Could there be a more tailored and surgical response? Are the LFDD processes for allocation and identifying protected sites robust? Could the process to bring the networks back online be accelerated or better prioritised?

These are just some of the ideas we have listed. No doubt there are other areas of the energy system that could also be reviewed and plenty of other ideas coming forward that could be exploited.

We would very much welcome comments from our members, and others, on what areas of innovation could add to energy resilience. In our role managing the Electricity Storage Network, we are engaging closely with the ESO as to whether batteries and other storage technologies could play a greater role in system security.


Regen is a not for profit centre of energy expertise and market insight whose mission is to transform the world’s energy systems for a low carbon future.

The ESN was established in 2008 as the UK industry group dedicated to electricity storage. It includes a broad range of electricity storage technologies and members, such as electricity storage manufacturers and suppliers, developers of projects, users, electricity network operators, consultants, academic institutions, and research organisations.

The ESN is managed by Regen.

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[1] Power cut 9 August 2019 interim report

[2] National Grid ESO Stability Pathfinder

[3] National Grid has had a number of innovation projects in this area and in a world first managed to accurately measure system inertia in 2016

[4] Contract signed with Reactive Technologies ( and a recent announcement that it will work with GE (


[6] Regen

[7] Engineering Recommendation G99

[8] See ENA

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