Hydrogen Storage
The process is simple:
Electricity is used to produce hydrogen through electrolysis. During charging, electricity splits water into hydrogen and oxygen. Hydrogen is compressed or otherwise prepared for storage. During discharge, stored hydrogen is converted back into electricity, including through hydrogen-capable gas turbines or other power conversion technologies.
Hydrogen storage differs from many other LDES technologies because it can provide flexibility over very long timescales, including weekly, monthly and seasonal storage.
Main configurations:
Compressed hydrogen storage in above-ground tanks: Hydrogen is compressed and stored in high-pressure vessels. Compressors increase the hydrogen pressure before storage, and pressure-reduction equipment prepares it for later use. This configuration is modular and can be located close to electrolysers, industrial consumers or power-generation plants. However, because hydrogen has a low volumetric energy density, pressurised tanks are generally better suited to smaller storage quantities and shorter storage periods than large-scale seasonal energy storage.
Underground hydrogen storage in salt caverns: Salt caverns are created by dissolving underground salt formations and removing the resulting brine. Hydrogen is compressed and injected into the cavern through a well. When the hydrogen is needed, it is withdrawn and processed. Salt-cavern storage is particularly relevant for large-scale and potentially seasonal flexibility.
Hydrogen storage in depleted gas fields: Depleted natural-gas reservoirs can potentially be repurposed for hydrogen storage. Hydrogen is compressed and injected into porous reservoir rock located beneath an impermeable caprock.
Why is hydrogen storage important to support the Energy Transition?
Hydrogen storage can provide large-scale flexibility over days, weeks or potentially seasons. Renewable electricity can be converted into hydrogen when wind and solar generation is abundant, stored, and used later when energy demand is higher or renewable generation is lower.
When hydrogen storage forms part of a hydrogen-to-power system, the stored hydrogen can be converted back into dispatchable electricity through a hydrogen-capable gas turbine or other power-generation technology. This can help maintain security of supply during prolonged periods of low wind and solar generation.
Hydrogen storage offers:
- Very long-duration and seasonal energy storage.
- The potential to store large quantities of renewable energy.
- Different storage configurations for different volumes and durations.
- Support for security of supply during prolonged renewable-generation shortages.
- Potential applications in renewable energy shifting, backup capacity and dispatchable power generation.
- An important role for compressors during hydrogen injection and withdrawal, and for hydrogen-capable gas turbines during power reconversion.