IN Brief:
- Frontier Power has acquired two Scottish long-duration energy storage projects from Apatura Energy.
- The Ayr and Busby schemes total 350MW and 2.8GWh of proposed storage capacity.
- The projects are planned around Eos Z3 zinc hybrid cathode battery technology.
Frontier Power has acquired two long-duration energy storage projects in Scotland from Apatura Energy, adding proposed zinc-based capacity to its UK storage pipeline.
The projects are the 200MW/1,600MWh Ayr battery energy storage system in Ayrshire and the 150MW/1,200MWh Busby project in East Renfrewshire. Together, they would provide 350MW of power capacity and 2.8GWh of storage capacity. Apatura will remain involved in the development of the schemes alongside Frontier until commercial operation.
The projects are planned around the Z3 technology platform developed by Eos Energy Enterprises. Eos develops zinc hybrid cathode batteries for long-duration applications, where multi-hour discharge, safety characteristics, and supply-chain differentiation form part of the commercial case.
Frontier Power has been building a long-duration storage platform in the UK, including work with Cerberus Capital Management and previous collaboration with Eos. The company has also highlighted interest in Ofgem’s cap-and-floor mechanism for long-duration energy storage, a regulated support model designed to help finance assets whose system value may not be fully captured through merchant revenues.
The acquisition adds weight to a UK LDES market that is moving beyond early-stage policy discussion. Lithium-ion battery storage has grown quickly, especially in one-hour and two-hour configurations serving frequency response, balancing, trading, and flexibility markets. Longer-duration assets are now being developed to manage deeper renewable variability, reduce curtailment, and support adequacy over longer periods.
Eight-hour projects such as Ayr and Busby occupy a different operational category from short-duration batteries. They can shift larger blocks of electricity across longer periods, absorbing surplus wind output and discharging into evening peaks or lower-generation windows. Their value depends on wholesale-price spreads, balancing needs, grid constraints, capacity-market revenue, and the structure of regulated support.
Zinc-based storage introduces technology diversification into a UK pipeline still heavily dominated by lithium-ion systems. Long-duration procurement is drawing interest in flow batteries, compressed air, pumped hydro, thermal storage, hydrogen-linked systems, and alternative battery chemistries. Each has a different profile across duration, response speed, efficiency, degradation, safety, footprint, and supply-chain exposure.
Scotland is a logical location for long-duration storage because of its renewable-generation profile and transmission constraints. Large volumes of wind generation are located north of major demand centres, and constraint costs can rise when the network cannot move power south. Storage near constrained generation can absorb surplus output, although its effectiveness depends on connection location, charging behaviour, dispatch rules, and local network conditions.
Storage is also expanding across smaller industrial and commercial settings, although the use case changes by scale. A 1.1MWh industrial installation delivered for AJW Group, detailed in coverage of the Sopoco battery project, was built around site resilience, solar self-consumption, and energy cost control. Utility-scale LDES assets such as Ayr and Busby are aimed instead at system flexibility, renewables integration, and longer-duration balancing.
The cap-and-floor mechanism is likely to shape the investment case for projects of this type. A floor can reduce downside risk and support financing, while a cap can return upside to consumers when revenues exceed an agreed threshold. The approach has already been used for interconnectors and is now being adapted for long-duration storage.
Engineering delivery will extend well beyond the battery chemistry. Long-duration projects require high-voltage connection design, transformers, power conversion systems, protection studies, fire and safety planning, civil engineering, grid-code compliance, control systems, and long-term maintenance planning. As duration increases, the balance between energy capacity, power capacity, footprint, and dispatch strategy becomes more influential.
Frontier’s acquisition indicates a maturing UK storage market in which short-duration batteries are no longer the only reference point. Fast-response assets helped prove the commercial role of grid-scale storage. The next phase will test whether longer-duration technologies can be financed, connected, and operated as core assets within a renewables-heavy power system.
