You can’t build a flexible grid without flexible thinking

Europe is committed to making rapid progress toward decarbonisation goals and building a foundation for long-term energy independence and security, all while keeping up with growing demand and without sacrificing stability and safety – or creating an excessive cost burden for European communities.

To get it right, the EU must build flexibility – "the ability of an electricity system to adjust to the variability of generation and consumption patterns and to grid availability, across relevant market timeframes” – into the grid. 

While the definitions surrounding system flexibility are still a work in progress, early signs point to an overly narrow vision, especially as it relates to long duration energy storage (LDES) technologies.

For example, Spain’s 2023 National Energy and Climate Plan (NECP) targets 18GW of storage by 2030, with a 487% increase from current levels. Yet, most procurement and subsidies under the Strategic Project for the Recovery and Economic Transformation of Renewable Energies, Renewable Hydrogen and Storage (PERTE ERHA) favour lithium-ion and pumped hydro, while more promising LDES technologies face market design barriers – such as lack of contracted revenue confidence and missing grid service markets.

Spain is not alone in this, with others including Italy advancing policies that are locking in dominant technologies such as lithium-ion batteries and pumped hydro energy storage at the expense of less well-established (but potentially invaluable) alternatives. 

Elsewhere, concern over 'Dunkelflaute', extended periods of low solar and wind generation, can lead to an over emphasis on ultra-long-duration storage solutions without considering other issues and other challenges. As a case in point, Germany has developed a draft procurement policy that proposes 72-hour discharge duration. Unfortunately, the storage technology solutions for these rare events are not optimised for the daily and intra-day fluctuations, that a mix of other storage duration technologies are positioned to manage.

These examples illustrate how Europe’s energy planners are, ironically, embedding layers of inflexibility into their flexibility policies.

The good news is that a course correction is still possible, if Europe’s leaders act now. As a starting point, we offer four recommendations that must be considered by policy makers and energy planners to support the future safeguarding of Europe’s energy flexibility and security.

1. Provide investment signals for LDES by setting procurement targets with 8+ hour mandates: Develop and embrace a storage definition and procurement strategy that accounts for an integrated system of short-, long-, and ultra-long-duration solutions.
2. Invest in intra-day flexibility, not just rare extreme events: Direct planning authorities to explicitly model intra-day and multi-day storage needs in national grid development plans, with clear capacity ranges and time horizons. Storage scenarios should reflect future load shapes, high renewables penetration and electrification trends across sectors.
3. Broaden the lens on energy storage technology options: Require that national grid operators and regulatory agencies design procurement frameworks that include duration-specific targets (e.g. 1–8 hours, 8–24 hours, 24+ hours) and remain technology-neutral within each band. Include criteria that assess lifecycle costs, flexibility, siting, and resilience – not only round-trip efficiency or technology readiness level.
4. Create investable business models for LDES energy storage technologies that are needed as the grid evolves but require an out-of-market commercial pathway: Implement a schedule of public tenders specifically targeting LDES (i.e. 8+ hour duration requirement) with target volumes and clear eligibility criteria. Structure these support mechanisms to accommodate a range of risk profiles, technology types, and project timelines.

Europe stands at a pivotal moment in its energy transition – one where the ambition to decarbonise and secure energy independence must be matched by a willingness to rethink entrenched approaches. By embracing a broader, more inclusive vision of system flexibility and recognising the value of diverse energy storage technologies, policymakers can unlock solutions that are both cost-effective and resilient.

The path forward demands bold leadership, targeted investmen, and a commitment to innovative and emerging technologies that reflects the complexity of tomorrow’s grid. As Ember Energy recently wrote: “Flexibility is the brain that keeps [a clean power system] running smoothly.” 

By rethinking the engrained assumptions that are shaping today’s policy decisions, Europe can achieve the true flexibility needed to accelerate its progress and meet its own ambitious goals for the benefit of all.

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About the author

About Hydrostor

Hydrostor is a global leader in long-duration energy storage, delivering utility-scale solutions using its patented advanced compressed air energy storage (A-CAES) technology. With offices in Toronto, Denver, Melbourne and Adelaide, Hydrostor is progressing a 7GW pipeline of projects globally that provide zero emission, flexible and durable storage to support grid reliability and renewable energy integration.

Read more about these insights in Hydrostor’s white paper, “From Ambition to Action: Embedding Long Duration Storage in European Energy Strategy”