Europe's largest vanadium flow battery delivered to East Sussex

What happened

In May 2026 Invinity Energy Systems confirmed it had completed delivery of a 20.7MWh vanadium flow battery system to the Copwood VFB Energy Hub in East Sussex — set to be Europe's largest vanadium flow battery once it enters service later in 2026. The installation comprises 90 individual battery units paired with a 3MW solar array, and can store enough electricity to meet the daily needs of around 3,000 homes.

Delivery was staged: the first 40 units were installed by 16 December 2025, with the remaining batteries and the solar array following in early 2026. The project is supported under the government's Longer Duration Energy Storage (LODES) demonstration programme, run by the Department for Energy Security and Net Zero. Invinity itself counts the UK's National Wealth Fund among its shareholders, and its technology has been selected for multiple bids under Ofgem's cap-and-floor support scheme for long-duration storage.

The technology

Vanadium flow batteries store energy in a water-based vanadium electrolyte held in tanks, rather than in solid electrode cells. The practical consequences distinguish them from the lithium-ion systems that dominate grid storage. The electrolyte is aqueous and carries no fire risk — a point of growing interest to planners and insurers as battery sites multiply near towns.

The chemistry is built for endurance: Invinity designs its systems for decades of heavy-duty cycling, meaning the battery can charge and discharge daily without the degradation that erodes lithium-ion capacity. And the architecture suits longer durations, discharging for hours at a time.

The trade-off is energy density. Flow batteries are physically larger for the same stored energy, which confines them to sites where land is available and rules them out of vehicles — but matters little for a fixed installation like Copwood.

The intended operation is straightforward energy shifting: charge from the co-located solar array and the grid when renewable output is high, discharge into the evening peak. Jonathan Marren, Invinity's chief executive, describes long-duration storage as "the missing piece that turns intermittent wind and solar into reliable, on-demand power".

The industrial story is as notable as the electrochemical one. Invinity assembles its batteries in Motherwell and Bathgate in Scotland, where it also runs research and development and customer support. Copwood is thus a UK-manufactured storage asset deployed on the UK grid — a rarity in a market supplied overwhelmingly by imported lithium-ion cells.

Why it matters for UK & Ireland

Great Britain's storage build-out to date has been dominated by lithium-ion batteries discharging for one to two hours. As wind and solar shares rise, the system increasingly needs storage that can shift energy across longer periods, and the government has built a policy architecture, the LODES demonstration programme and Ofgem's cap-and-floor scheme, specifically to bring long-duration technologies to market. Copwood is that policy taking physical form: a first-of-scale demonstration intended to generate the operating record on which commercial financing of larger projects depends.

The fire-safety characteristics carry their own planning significance. Battery storage applications have met growing local scrutiny; a non-flammable chemistry removes one of the most common grounds of objection, which may prove a genuine siting advantage in densely settled areas of southern England — and in Ireland, where grid-scale storage is also expanding.

There is also a supply-chain argument. A domestic manufacturer in Motherwell and Bathgate, part-owned by the National Wealth Fund and winning UK deployments, is precisely the pattern industrial strategy is meant to produce. Whether it can scale against lithium-ion's cost curve is the unresolved question.

What to watch

Grid connection and commercial operation later in 2026 is the immediate milestone — delivery is complete, but Europe's-largest status is only earned when the system is in service. After that, the performance data: round-trip efficiency, availability and daily cycling behaviour at 20.7MWh scale will be closely read by investors weighing flow batteries against lithium-ion. Finally, the fate of Invinity's cap-and-floor bids under Ofgem's scheme will indicate whether Copwood is a one-off demonstration or the first of a fleet.