Fiddler’s Ferry battery electrical buildings installed

RSK Group businesses have installed prefabricated electrical buildings at SSE Renewables’ Fiddler’s Ferry battery project near Warrington, completing a defined construction package for the 150MW/300MWh installation. AJ Engineering & Construction Services and Northern Engineering & Welding Co (NEWCo) supplied two auxiliary transformer buildings, a portable relay room and a steel-framed switch room. The buildings are in position; the electrical equipment they are designed to accommodate has not yet been fully fitted out.

The development occupies part of the former Fiddler’s Ferry coal-fired power station and is being delivered by OCU Energy and battery supplier Fluence. RSK’s 9 November update concerns the enclosures and structural work, rather than commissioning of the energy storage equipment or an energised connection. OCU is due to begin internal equipment installation after the buildings have been handed over.

AJ Engineering and NEWCo made the two auxiliary transformer enclosures and the relay room as steel modules, installing their cladding before transport to the site. RSK says the kiosks were ready for installation within six weeks. Prefabrication allows the structural and weatherproofing work to be undertaken away from the live construction area, reducing the number of trades that have to work simultaneously around electrical and civil packages.

The switch room was built differently, as a structural steel portal frame with insulated cladding. Acies, another RSK business, designed structural connections for the frame, while AJ Engineering undertook modelling and fabrication. The term “connection design” in this part of the work refers to joints within the building structure; it should not be confused with design or approval of the project’s electrical grid connection.

Once fitted out, the kiosks will accommodate apparatus such as relays, switchgear, communications and control panels. Those systems support fault detection, switching, supervision and the safe separation of circuits during maintenance or abnormal operation. The November update does not include a final protection schedule or confirm that the switching and control apparatus is operational. Accordingly, the construction milestone is the installation of the structures, not completion of a working substation.

SSE gives the battery a 150MW power rating and 300MWh of storage capacity. The first figure describes its rated power output; the second describes the quantity of energy available over time. Dividing the nominal energy figure by the power rating gives a two-hour duration at full rated output, before allowance for operating constraints and conversion losses. SSE estimates that this could meet the equivalent peak demand of up to 250,000 homes for as much as two hours.

The project will be able to absorb electricity when charging and export it when dispatched, subject to its network connection and operating arrangements. Such operation depends on coordinated battery controls, power conversion systems, transformers, protection and communications. Even after the electrical rooms are equipped, completion of the mechanical and electrical installation will be followed by testing and integration before commercial operation can begin.

OCU’s published project scope identifies a new 275kV National Grid connection, a 275/33kV main transformer rated at 140/180MVA, air-insulated switchgear, and high- and low-voltage electrical infrastructure. It also lists the installation of 472 battery units, 44 inverters and 22 medium-voltage skids. These figures describe the overall balance-of-plant contract, not items newly installed by RSK in November. OCU identifies fixed network outage windows as a constraint on the sequencing of work and eventual energisation.

SSE took the investment decision to construct the project in December 2023, and building work began in early 2024. The former power station ceased generating in March 2020 and its cooling towers were demolished in 2023. Reusing part of the former generation estate for storage retains an electricity infrastructure function at a site previously associated with conventional power production, although the new battery has a different operating role from the retired coal plant.

Construction therefore involves separate structural, electrical and network-interface sequences. The steel kiosks can reduce on-site building work, but the equipment inside them must still be installed and tested alongside the wider battery plant. Network protection and communication arrangements will also have to operate correctly with the National Grid interface before power can be imported or exported.

RSK identifies internal fit-out by OCU as the next step and gives 2027 as the expected operational year. SSE’s live project page confirms that construction is continuing, without committing to a more precise commissioning date. The prefabricated buildings are a completed component of the project, while the electrical system they will house and the wider battery remain in development.