Enhancing Underground Hydrogen Storage in Andalusia through Saline Caves

The deployment of green hydrogen production in Andalucia is progressing rapidly, bolstered by multimillion euro investments aimed at positioning the region as a key player in the clean energy sector. Currently, the regional government reports that around 6200 million euros have been mobilised across various projects, with the Green Hydrogen Valley in Huelva at the forefront, covering the entire value chain from production to commercialisation. Yet, an essential aspect remains under development storage capacity.

Innovative storage solutions, especially underground infrastructure, are gaining momentum. The University of Seville and the Andalucian Industry Research and Cooperation Association (AICIA) are conducting studies to identify optimal subterranean locations, particularly saline caves, for storing hydrogen. This approach addresses one of the main technical challenges of hydrogen deployment its low density and complex storage requirements, especially in large quantities.

Underground salt caverns offer a promising solution due to their ability to accommodate large volumes and their favourable geological characteristics. The research involves detailed territorial mapping to identify sites near strategic transport hubs, such as ports along the Mediterranean and major routes planned for hydrogen pipelines. For example, the northern region of Jerez de la Frontera has been pinpointed as an ideal location, given its proximity to the Port of Algeciras and the Green Hydrogen Valley in Palos de la Frontera.

The typical saline cavern for hydrogen storage would have a capacity of approximately 500,000 cubic metres. The process involves injecting water into the cavern to dissolve the salt, creating a brine, then injecting hydrogen once the structure is secure. The construction requires specific conditions being located away from urban areas or military zones and close to existing natural gas and hydrogen infrastructure to ensure economic viability and integration into the energy network.

One of the major hurdles in producing green hydrogen is water availability. The project in Andalucia proposes using seawater—requiring eight cubic metres of water per cubic metre of salt dissolved—to address this challenge sustainably. This approach leverages proximity to the coast, allowing seawater to be pumped directly into the caverns, with the brine being returned to the sea, reducing waste and minimising environmental impact.

While initial concerns focus on water use, industry experts emphasise that water requirements for green hydrogen are significantly lower compared to fossil fuel based processes. Analyses suggest that the use of seawater for salt dissolution is sustainable, especially when combined with recycling and localised management. Moreover, reconverting decommissioned thermal power plants into hydrogen infrastructure presents an additional opportunity for Andalucia to accelerate its decarbonisation efforts, optimising existing industrial assets in the transition to renewable energy