Experience with Commercial Stability Service Provision of the UK Blackhillock Large Scale Grid-forming BESS

UK. Operational since March 2025, the 1st project stage with 200 MW/400 MWh represents the UK’s first deployment of a large-scale private asset that beyond the typical BESS functions additionally provides commercial, firm, zero-carbon inertia and short-circuit level (SCL) services directly to the transmission system under a commercial contract and in compliance with the world-first minimum technical standard for grid-forming capability (GC0137).

SP2 tender results demonstrate that BESS can deliver firm inertia and SCL for lower cost compared to synchronous condenser or hybrid technology, if the procurement framework is open for novel technology, rewards firm service provision and facilitates service stacking. The paper highlights the importance of an adequate plant design, with appropriate controls and components for competitive delivery of firm, instantaneous grid-forming services on top of other services and for meeting contractual obligations. The full site performance of the

Blackhillock GFM BESS is validated based on real events in the UK power system, including a generator loss event and an unbalanced fault. This is done through a comparison of real measurements during commercial operation with corresponding results of electromagnetic transient (EMT) simulations and theoretical calculations. The results demonstrate very accurate matching with the specified and expected performance.

The results underline the high maturity level of multi-purpose GFM BESS technology for provision of advanced commercial stability services and prove the effectiveness of demandoriented, technology-neutral, market-based methods for cost-efficient power system planning.

This successful practical experience could pave the way for fast adoption in other power systems to efficiently support and accelerate the transition to net-zero.