Batteries in Great Britain have been getting bigger, with the average rated power of installed systems increasing by 70% since 2019. Currently, the largest batteries are 100 MW. The first 1 GW systems are due to come online by the start of 2027.
However, ramp rate restrictions, market-moving impacts, and differences in Balancing Mechanism utilization could all mean that operations and revenues for these batteries will differ from those of batteries currently in operation.
Currently, no operational batteries are subject to these restrictions. In this article, we have used data from current pumped storage hydro assets, as well as our forecast, to estimate how revenues might compare for large batteries.
Batteries in Great Britain have been getting larger
On average, batteries in Great Britain have been getting larger - both by rated power (MW) and energy capacity (MWh).
Falling Capex and saturating frequency response markets have been driving the trend towards longer-duration, higher energy capacity systems. However, economies of scale have driven the trend towards higher rated power.
Project costs associated with securing land rights and financing don’t scale as quickly with project size, meaning larger projects are cheaper per MW. Planning permission in particular can be a driving factor. Projects larger than 50 MW classified as nationally significant infrastructure, going through a separate and expensive planning process. This means that developers look to maximize the size of the battery to offset these flat costs.
Ramp rate restrictions limit the trading flexibility of larger batteries
Physically, batteries can ramp nearly instantaneously. A 300 MW battery selling power for 30 minutes could export at full power across the settlement period to discharge 150 MWh. However, the Balancing and Settlement Code (BSC) enforces artificial ramp rate restrictions on large generators to ensure grid stability.
The BSC restricts batteries to ramping at 50 MW per minute for changes in power above 300 MW. This means that over a 30-minute period, a 1 GW battery could only discharge at full power for 2 minutes. For changes above 1 GW, a lower ramp rate of 40 MW per minute applies.