In November 2023, National Grid ESO opened a proposal for a Grid Code change: ‘GC0166: Introducing new Balancing Programme Parameters for Limited Duration Assets’.
This change aims to enable enhanced data communication between storage assets and the control room. It is the mechanism behind ‘new energy storage parameters’ - one of the key improvements under the Open Balancing Platform programme of improvements, which aims to effectively end the ‘15-minute rule’.
But what will this mean for battery operators and how could it enable longer battery dispatches in the Balancing Mechanism?
Currently, the ‘15-minute rule’ limits batteries to short dispatches in the Balancing Mechanism
The Grid Code defines data flows between grid-connected assets and the control room. Currently, this standard does not include provisions for storage assets to communicate their state of charge or energy availability to the control room.
When dispatching these assets, the control room instead uses a workaround - using an asset’s Maximum Import Limit (MIL) or Maximum Export Limit (MEL).
The Grid Code defines these values as the maximum amount of power an asset can import or export at any point in time. Batteries instead use this existing value to communicate how much power they could import or export for a period of 15-minutes.
This way, the control room is able to dispatch assets for short lengths of time and be confident that they will be able to deliver within their state of charge constraints. The control room has no visibility of availability beyond this timeframe, so currently doesn’t dispatch batteries for longer periods. Batteries do redeclare their MEL and MIL values which makes it possible to receive dispatch extensions. In practice these rarely happen.
ESO is proposing two potential solutions to enable longer dispatches
The current Grid Code change proposal doesn’t specify how the ESO will technically enable longer dispatches. This is something that it is actively working on and, so far, two different approaches have been proposed:
1. Reading state of charge data directly from an asset’s SCADA system
In the first approach, asset operators would provide ESO with a data feed from the monitoring systems of their batteries. A maximum and minimum state of charge could also be specified, to stay within cell warranty conditions, for example.
ESO could then use this state of charge data to infer availability for bids and offers. However, this would require the control room to model assumptions around efficiency, capacity (which may be derated as a result of state of charge or temperature) and other factors.
2. Enabling operators to declare their Maximum Deliverable Bid (MDB) and Maximum Deliverable Offer (MDO) volumes
Alternatively, the ESO could modify the Grid Code to allow battery operators to declare the total amount of energy they have available for bids and offers.
For example, a 50 MWh battery charged to 25 MWh could declare an MDB and MDO of 25 MWh.
The control room would update these values if it dispatched the battery in the Balancing Mechanism. If the battery was dispatched for a 5 MWh offer, its MDO would be updated to 20 MWh and its MDB to 30 MWh.
Capacity contracted in frequency response services would decrease either MDB or MDO, depending on the direction of the service. Operators must reserve volume to deliver on these contracts if required.
If the battery contracted 40 MW capacity in Dynamic Containment High, it would need to reserve 10 MWh of energy - enough to deliver this service for 15 minutes. Its MDB would decrease to 20 MWh, while its MDO would remain unchanged.
Finally, charging or discharging would also change MDO and MDB values. If the battery fully charged in the wholesale market, the operator would change its MDO to 50 MWh and its MDB to 0 MWh.
Stakeholder engagement is ongoing - have your say
ESO has been actively consulting on the approach to be taken through its ‘Balancing Transformation - Storage Stakeholder Group’. So far, the group has discussed the technological requirements of each approach how availability can be modelled from state of charge, and how availability can be planned over the longer term.
A working group has now been put together that will define the approach for the Grid Code modification process. This group will release a consultation on the proposed approach in April. Following this, it is expected that industry consultation will take place in July. This is a chance for battery operators to shape the format of the Grid Code change.
A draft modification report is expected by the start of September. This will be implemented 10 working days after Ofgem’s approval.
Overall, the potential impact of these changes is significant. We have previously shown that increasing the maximum dispatch length of batteries increases the volume of dispatches they can compete for from 24% to 69% of total volumes. As part of the wider Open Balancing Platform, this could increase lifetime battery revenues by up to 20%.