IN Brief:
- Zenobē has reached financial close on the 200MW/800MWh Coalburn battery storage project in South Lanarkshire.
- The project is the first four-hour duration battery connected to the UK transmission network to reach financial close.
- Commercial operation is expected in 2028, with Drax managing trading through a tolling contract.
Zenobē has reached financial close on its 200MW/800MWh Coalburn battery energy storage system in South Lanarkshire, advancing one of the UK’s most substantial four-hour transmission-scale storage projects.
The project is the first four-hour duration battery connected to the UK transmission network to reach financial close. Preparatory works have begun, construction is scheduled to start in July, and commercial operation is expected in 2028.
Coalburn will operate at a maximum import and export capacity of 200MW with 800MWh of storage. The asset can also operate at different power and duration settings, including 100MW for up to eight hours or 50MW for up to 16 hours. That flexibility gives the project a broader operating profile than a fixed four-hour dispatch block.
Canadian Solar’s e-STORAGE business will supply the battery systems, while Omexom will deliver the balance-of-plant works. Drax Group will manage commercial trading of the asset through a tolling contract, integrating Coalburn into wider power-market and grid-stability services.
The financing package has been secured from Landesbank Baden-Württemberg, ABN AMRO, Mizuho, and Siemens Financial Services. The lenders also participated in Zenobē’s 400MW Eccles battery project, adding continuity to the company’s financing route for large-scale storage assets in Great Britain.
The UK battery market is moving into a more demanding phase. Early projects were often shorter-duration assets targeting fast-response services and trading opportunities. Larger projects now need to demonstrate grid relevance, revenue resilience, connection credibility, and deliverability through a period of market reform.
That financing discipline is visible across other UK and European storage projects, where investors are placing greater weight on duration, connection route, revenue structure, optimisation arrangements, and long-term operating risk. Coalburn’s progress shows that large assets with credible partners and structured revenue models can still secure capital despite connection reform and market uncertainty.
The tolling agreement with Drax is central to the project’s commercial structure. Under a tolling model, the asset owner retains responsibility for construction, maintenance, and availability, while the offtaker secures dispatch rights or operational control under defined terms. For storage assets, this can give lenders more predictable revenue exposure than a purely merchant project.
Drax’s role places Coalburn inside a wider flexible generation and storage portfolio. Batteries, pumped storage, optimisation platforms, and dispatchable assets are increasingly being assembled to respond to price volatility, balancing requirements, and grid stability needs. Storage is no longer treated only as a standalone trading asset.
Coalburn’s four-hour duration sits in an important part of the market. The UK’s long-duration energy storage support scheme has focused on assets with durations of eight hours or more, while much of the near-term battery market remains closer to two-hour duration. Four-hour batteries sit between those categories, offering deeper shifting than standard short-duration systems while remaining inside lithium-ion project economics that lenders already understand.
In Scotland, the operating case is tied closely to wind integration and transmission constraints. High renewable output in the north can exceed the network’s ability to move power south, leading to curtailment and constraint costs. Batteries cannot replace major transmission reinforcement, but strategically located transmission-connected storage can absorb electricity during surplus periods and support system operation when demand and network conditions change.
The ability to operate Coalburn at lower power for longer periods adds useful flexibility. A 200MW four-hour dispatch may suit evening peaks or market opportunities, while 100MW over eight hours could support longer balancing needs. The commercial value of those operating modes will depend on market prices, grid requirements, and dispatch strategy once the asset is commissioned.
Connection reform remains part of the background. Battery developers have faced uncertainty as the queue is reshaped and projects are assessed against readiness and system need. Coalburn’s progress to financial close indicates that projects with credible connection pathways, strong delivery partners, and structured revenue arrangements remain capable of moving forward.
Scotland is becoming a major storage investment region because of its wind resource, grid constraints, high-voltage infrastructure, and need for flexibility. Construction delivery, grid connection, commissioning, and long-term operation will now determine whether Coalburn becomes a reference project for the next wave of four-hour transmission storage.
