Airengy and European chemicals producer Nobian have agreed to assess the development of a compressed-air energy storage project using an existing salt cavern in Denmark.
The proposed compressed air power plant, or CAPP, could provide up to 2.5 gigawatt-hours of storage capacity, with electricity-generation output expected to range from 3 MW to 10 MW.
The partnership remains at the feasibility stage. Airengy and Nobian will examine the project's technical requirements, regulatory pathway and commercial case before deciding whether to proceed with construction.
Existing Salt Cavern Could Become a Long-Duration Storage Asset
Compressed-air energy storage systems use electricity to compress air, which is then stored underground. When additional electricity is required, the air is released and used to generate power.
Salt caverns are among the geological structures being considered for this type of storage because they can provide large underground volumes without requiring the construction of above-ground battery facilities of a comparable energy capacity.
Under the agreement, Nobian will remain responsible for the cavern and retain its operating license. Its role will cover permitting, regulatory processes, supporting infrastructure, stakeholder engagement and communication with the local community.
Airengy will lead the design of the AirBattery system, including the compression and electricity-generation equipment. The feasibility work will assess how the equipment could connect with the existing cavern and the surrounding energy infrastructure.
The proposed balance between storage capacity and generation output indicates that the site is being considered for extended discharge periods rather than short bursts of grid support. The final operating profile will depend on technical studies, grid requirements and the project's commercial structure.
Long-duration energy storage is receiving increased attention as European electricity markets add more wind and solar generation. Unlike short-duration batteries, systems designed to store energy for longer periods could help manage extended gaps between renewable generation and electricity demand.
A Danish CAPP could absorb electricity when renewable output is high and release it when supply falls or demand rises. This type of operation may also support grid congestion management and reduce exposure to periods of extreme wholesale price volatility.
Commercial Viability Will Shape Airengy's European Expansion
The Denmark proposal forms part of Airengy's wider European project pipeline. The company has also announced compressed-air storage partnerships involving sites in England, Romania and Germany.
Its development strategy includes smaller plants with planned outputs of about 1 MW to 1.5 MW in England and Romania, alongside larger projects in markets such as Denmark.
Working with Nobian gives Airengy access to an existing cavern operator with experience in salt production, solution mining and underground infrastructure. For Nobian, the assessment provides an opportunity to examine whether its cavern assets could support electricity storage as European energy systems become more dependent on variable renewable generation.
Several hurdles remain as the project will need to meet technical and safety requirements, secure permits, confirm grid connections and demonstrate that expected market revenues can support its development and operation.
Long-duration storage projects also depend on electricity-market frameworks that place sufficient value on flexibility, capacity, reliability and grid services. Without dependable revenue mechanisms, large-scale projects can struggle to reach a final investment decision even when the underlying technology is viable.
Airengy is separately evaluating potential applications for its compressed-air platform in electricity-intensive industries, including data centers. Growth in digital infrastructure is increasing demand for power systems capable of supporting reliability over longer periods, although individual opportunities will depend on site requirements and energy-market conditions.
The Danish agreement does not yet represent a construction commitment. It does, however, provide both companies with a framework for determining whether an existing salt cavern can be converted into a commercially workable long-duration energy storage facility.
