As large-scale power plants shut down and more intermittent renewables come online in the UK, an efficient frequency response service will prove to be increasingly crucial to maintaining a stable electricity network. Now, a joint project between National Grid and renewable energy firm Renewable Energy Systems (RES) will mark the first time battery energy storage systems are to be used to balance the grid on a sub-second basis. It is expected that the storage systems will provide a dynamic frequency response service in sub-second timescales.
Cost effective frequency response
The parties have signed a four year contract that will see RES provide a 20MW of frequency response from battery storage. This is a new service which will help National Grid in performing its system balancing role, which increasingly requires innovation and the use of new technologies. The services delivered by RES’ battery storage systems will provide cost effective frequency response to the grid within one second of the detection of a frequency deviation. The battery storage systems will be fully operational within 18 months.
RES and National Grid have been working together to design this innovative service since 2014; work which has been a forerunner to National Grid’s upcoming tender for 200MW of Enhanced Frequency Response. National Grid Electricity Transmission is aiming for a frequency that achieves 100% active power output at 1 second (or less) of registering a frequency deviation. This is in contrast with existing frequency response services of Primary and High which have timescales of 10 seconds, and Secondary which has timescales of 30 seconds. This is a new service that is being developed to improve management of the system frequency pre-fault, i.e. to maintain the system frequency closer to 50Hz under normal operation.
National Grid is looking to procure a volume of enhanced frequency response through a tendering exercise, which is currently being held.
Successful bidders will receive four year contracts, which National Grid believes strikes a balance between risk and reward for those looking to own and operate assets, which in the main are likely to be batteries. However, the auction is technology-neutral. Interconnectors, other forms of energy storage and even aggregated domestic batteries will not be prevented from making a bid, provided they meet the 1MW minimum requirement, can connect to grid’s systems and have the relevant data.
National Grid is also set to broaden the scope of Enhanced Frequency Response so that its definition also covers primary and secondary response. While the system operator originally mooted a 9 second minimum response duration, that may now be extended. National Grid says it may also develop in parallel another service for short duration, fast-response characteristics for post-fault frequency control.
As the price of battery energy storage has fallen in line with gigawatt scale deployment in the stationary energy storage and electric vehicle fields, such services are now reducing electricity costs for consumers across global markets. RES has already commissioned six similar projects in the US.
Fast acting frequency response
According to Adam Sims, Senior Account Manager at National Grid, this is the first time that battery storage will be used to provide such fast-acting frequency response service to the national transmission network in Great Britain. He adds: “This innovative technology will enable us to respond to frequency issues in under a second, helping to maintain the integrity of the grid. This service and the forthcoming Enhanced Frequency Response service will support the network as we transition to a generation mix with greater levels of low cost renewable energy.”
John Prendergast, Energy Storage Manager at RES, said:“We’re delighted to be working with National Grid on this contract. RES has previously pioneered the delivery of very fast frequency services in Canada and is one of the largest providers of such services in the USA. Now, developing this innovative service with National Grid is a major step in the development of RES’ UK energy storage business.”
He continues: “Energy storage can play a large role in supporting the UK’s transition to a secure, low carbon, low cost energy system. We believe that this contract will play an important role in demonstrating this and will encourage policy makers and regulators to accelerate the removal of barriers to wider deployment of energy storage in the UK.”