First introduced in October 2020, Dynamic Containment (DC) is a post-fault rapid response mechanism that attempts to smooth instability within electricity systems and, more broadly, the national grid.
It was developed by the National Grid Electricity System Operator (NGESO) as a means of phasing out their slower, monthly-tendered Firm Frequency Response (FFR) service. As one of the fastest services in the world, DC ensures that the frequency of the power network operates within one per cent of 50Hz, 24-hours a day. Low DC is employed in re-instating this frequency when current fluctuations have forced it below the optimum, and high DC enables the converse.
Maintaining the 50Hz target is crucial to ensuring the effective functioning of the UK’s energy distribution - it’s the frequency at which all UK appliances, electrical equipment, homes and businesses operate. If the supply of electricity exceeds its demand, this frequency will rise; and if demand exceeds supply, it will fall.
Frequency changes can also be a direct consequence of physical problems such as power line faults or generator failures. These sudden, system-based complications trigger particularly abrupt fluctuations in frequency, subsequently resulting in significant energy disruptions across the UK. DC aims to reverse these imbalances, with DC providers injecting power during large drops in frequency.
With the growing development and integration of renewable energy into the grid, the likelihood of unequal supply/demand-induced fluctuations are increasing. Renewables are non-synchronous; they usually rely on unpredictable generation sources (such as wind or solar) that subsequently result in intermittent energy production and supply.
Previously, thermal power acted as a steady shock absorber for sudden frequency changes; but, as the proportion of the energy mix that is made up of decentralised renewable power increases, the portion of inbuilt system inertia will fall. This means that the speed and capacity at which frequency response can take place must be particularly streamlined.
Currently, the NGESO requires that response time is less than a second, and is active when frequency moves outside of the ± 0.2Hz operational limits. DC facilitates future changes in the energy supply mix by directly combatting the heightened fluctuations in frequency that renewable grid integration entails. As such, it has a huge role in enabling the safe and effective transition of the UK national grid towards zero carbon energy sourcing.
Battery Energy Storage Systems (BESS) are particularly useful in managing frequency response, as their flexibility and speed enable a more stable utilisation of renewable energy in DC. Infact, many posit that DC will actually drive investment into battery energy storage; as renewable growth continues, its contribution towards DC is likely to become more significant.
Batteries effectively act as synthetic inertia; when significant frequency disturbances occur, they offer a reliable means of restoring stability. According to a lead developer at LCP Enact, such storage "continued to achieve high revenue streams of £21.5 million through the Dynamic Containment market in July".
Indeed, NGESO have committed to further unlocking revenue stacking for battery assets through the Balancing Mechanism in an attempt to incentivise investment into BESS. Here, value stacking allows BESS to earn revenue through both engagement in DC and through the Wholesale and Balancing markets, with optimisers often opting for the latter when DC volume requirements drop.
However, it is worth noting that some older battery assets struggle to act effectively as a DC participant. Essentially, the previous FFR service had less stringent technical requirements, and so the national switch to DC, whilst certainly being vital for long-term grid development, is not without some short-term difficulties regarding BESS. Indeed, the pre-qualification tests for becoming a DC provider are widely regarded as the strictest criteria of any service in which batteries can participate.
Regardless, it is evident that BESS have a huge role to play in ensuring the continued integration of renewable energy into the grid, and the necessary maintenance of stability through their participation with DC.
DC is an integral part of the UK’s national grid. It enables rapid response to the detrimental fluctuations in frequency caused by physical problems and supply/demand disequilibria. As investment and development in renewable energy generation continue to increase, DC will have an even more important role to play in managing these fluctuations.
Already, the grid is moving away from the inertia traditionally supplied by thermal power, and is instead utilising DC to embrace and manage the less stable provision of renewable energy. More specifically, BESS has demonstrated the value of renewable energy storage, and offers a viable solution for ensuring complete DC efficacy alongside revenue generation.
