The expansion of renewable energy is an irreversible global trend. Yet solar and wind power inherently carry intermittency. When the sun sets or the wind stops, electricity supply is cut off, and seasonal supply-demand imbalances lead to grid instability. Until now, batteries and pumped hydro storage have filled this gap, but 'lithium-based storage devices face limits in cost, lifespan, and safety', while pumped hydro has geographic constraints that make it inapplicable everywhere. This is why new solutions for long-duration or even 'seasonal storage' are needed. The emerging alternative is 'Geochemical Energy Storage (GES)'.

The U.S.-based startup 'Quidnet Energy' is a pioneer in this field, developing GES technology with commercialization targeted for 2025. The principle is simple yet powerful: inject water at high pressure into underground rock reservoirs, store it, and release it back to generate electricity when needed. Thanks to the cycle of electricity-pressure-hydropower, it is possible to 'store energy with almost no loss for up to six months'—a major advantage over existing short-term storage technologies.

Quidnet Energy is running several demonstration projects in Texas and California. For example, in 2023, a pilot plant in Texas succeeded in a 1MW-scale power storage and release test, proving that seasonal electricity storage is feasible in practice. The U.S. Department of Energy (DOE) has selected this project as a core model in its Long Duration Energy Storage (LDES) program.

Existing compressed air energy storage (CAES) or pumped hydro systems require large-scale topographical conditions, making deployment difficult. GES, however, 'operates stably under medium temperature and pressure'. Based on hydroxide reactions, it balances pressure and heat to preserve energy for long durations, with fewer issues of structural degradation or leakage.

This feature has been validated not only in laboratory studies but also in the field. In a Texas demonstration project, Quidnet Energy successfully stored and released power stably for over 90 days—clear proof of differentiation from short-term, battery-based energy storage systems (ESS). In this sense, 'seasonal-scale storage' is becoming a reality.

The most notable advantage of GES is its cost structure. By using abundant resources such as water and rock, it avoids reliance on scarce metals like lithium, cobalt, or nickel, whose supply chains are unstable. Unlike sulfur or methanol-based auxiliary resources, it does not require additional input materials, further lowering risks.

In comparison, the installation cost of lithium ESS is around '\$300–400/kWh', whereas Quidnet Energy projects that GES technology could fall 'below \$100/kWh'. Factoring in maintenance costs, some analyses suggest up to 70% cost savings compared to lithium ESS in the long run.

From an environmental perspective, the benefits are also significant. GES avoids the ecological destruction associated with mining or refining rare metals and uses existing underground rock structures, reducing the need for massive civil engineering projects. Thus, it fulfills the three conditions of 'low cost, high efficiency, and environmental friendliness' simultaneously.

The impact of GES goes far beyond the introduction of a new storage device.

* 'Removing the bottleneck for renewable expansion': By addressing intermittency in wind and solar, it stabilizes the grid. For example, surplus summer electricity can be stored and used for winter heating demand, enabling seasonal energy balancing.

* 'Strengthening sustainability': By reducing dependence on scarce metals and using abundant resources like water and rock, it builds a resource-circulating energy model.

* 'Restructuring the industry': The emergence of a new competitor alongside batteries could reshape the ESS market. In fact, renewable energy companies in the U.S. and Europe are already expressing investment interest in GES projects, suggesting that market structures could be redefined.

GES is gaining attention not only in the U.S. but also in Europe. The European Union (EU) announced plans to increase renewable energy to 45% by 2030, but without long-duration storage, grid instability is unavoidable. Energy firms in Germany and France are benchmarking Quidnet Energy’s model and are initiating underground reservoir storage projects.

Korea, too, has ambitious renewable energy expansion goals but faces limitations in land and geography for pumped hydro or large-scale battery projects. As such, GES models that utilize underground rock formations could be highly applicable in Korea, particularly in coastal rock regions along the East and South Seas.

As GES approaches commercialization, several hurdles remain:

1. 'Scaling up demonstrations': Thus far, projects have been at the MW scale. It remains to be proven whether the same performance holds at hundreds of MW or GW scales.

2. 'Lifespan and durability': Seasonal storage has been demonstrated, but whether it can endure thousands of charge-discharge cycles required by the grid remains uncertain.

3. 'Optimizing cost structures': While raw materials are cheap, the initial costs of electrolyte synthesis and compression facilities remain high. Large-scale deployment and supply chain optimization will be necessary.

4. 'Regulations and safety certification': To be deployed in commercial grids, GES must pass international safety certifications and national energy regulations. This is the biggest barrier to transitioning from lab-scale results to commercial reliability.

The significance of GES lies not only in being a cheaper storage technology but also in offering a 'gateway to a 100% renewable society'. For instance, surplus solar power in summer could be stored and used for winter heating needs, or wind intermittency could be balanced across seasons.

While still at an early stage, the model presented by Quidnet Energy demonstrates the potential to satisfy the three conditions of 'low cost, high efficiency, and long duration' simultaneously. Within the next decade, if this technology is commercialized, humanity could take a major step toward an era of 'electricity available anytime'—a true renewable energy society.

Nature Communications, 2025, “Intermediate-temperature K-Na/S battery with stable performance enabled by new electrolyte design,” Columbia University Engineering