Adding more inertia in the UK

15 March 2023

NG ESO Stability Pathfinder: a further update

Above: Synchronous condenser at Rassau, South Wales (photo: Quinbrook)

In February 2023, Quinbrook Infrastructure Partners (a “specialist investment manager focused exclusively on the infrastructure needed to drive the energy transition”, with a portfolio that includes Flexitricity and Habitat Energy) announced start of construction on four new synchronous compensators (aka synchronous condensers) in Scotland.

Each syncomp project will benefit from long term, index linked revenues under Phase 2 of National Grid ESO’s Stability Pathfinder programme. Quinbrook is working with Welsh Power (WP Grid Services) on the projects, which are located near Gretna, Neilston, Rothienorman and Thurso, respectively.

Stability Pathfinder Phase 2 saw the awarding (in April 2022) of ten contracts (totalling £323 million) to four companies (Statkraft, TINZ Programme 1 ProjectCo 3, Zenobe¯, and WP Grid Services) for provision of inertia (6.75 GW.s) and short circuit levels (11.55 GVA) in Scotland (see MPS, June 2022, p37).

Zenobe¯ has recently announced financial close and start of work at Blackhillock on the first 200 MW/400 MWh of a 300 MW/600 MWh grid forming battery storage system, one of three battery projects it is implementing in Scotland as part of Stability Pathfinder Phase 2. Key suppliers for Blackhillock, said to be the first facility in the world “to deliver stability services using a transmission-connected battery”, include Wa¨rtsila¨, H&MV, SMA Solar Technology AG and GE Grid Solutions, with funding from a £235m long-term debt facility from five banks (described as the ”largest project finance facility for battery storage ever to be arranged in Europe”).

NG ESO Stability Pathfinder Phase 1 concluded in January 2020 with the award of contracts for the provision to the GB grid of a total of 12.5 GW.s of inertia over a six year period, at a cost of £328 million (see MPS Jan/Feb 2022. pp 20-21 and April 2020, p21).

In November 2022, NG ESO announced the conclusion of the Stability Pathfinder Phase 3 tender process with the awarding to six companies of contracts worth a total of £1.3 billion for supply of inertia (17 084 MW.s) and short circuit level (some 8720 MVA) across England and Wales. See table.

The contracts “represent a cost benefit of £14.9 billion between 2025 and 2035”, NG ESO estimates, and will contribute to long-term stability for the grid, helping reduce carbon intensity, enabling the ESO to operate the network with zero-carbon by 2025 and set up the UK to deliver a net-zero electricity system from 2035.

Stability services are currently mainly provided by synchronous generation, such as fossil fuel power stations, which provide stability outputs alongside power generation. Contracts placed as part of the Stability Pathfinder initiative will help deliver alternative methods of producing inertia, short circuit level and dynamic reactive power, says NG ESO.

Quinbrook says it has been working with its development partner Welsh Power since early 2021 on its two Phase 3 projects, Sellindge (near Ashford) and Cilfynydd (north of Cardiff), “when suitable site locations were identified that could provide appreciable benefit to National Grid.”

Quinbrook’s first synchronous condenser, at Rassau, Wales, also developed with Welsh Power, has been in operation since February 2022. Quinbrook notes that it was the only non- utility sponsored project to secure a contract in Stability Pathfinder Phase 1 (the other successful contenders in Phase 1 being Drax, Statkraft, Triton and Uniper).

Quinbrook says it has now amassed the largest portfolio of privately owned synchronous condensers in the UK.

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