ALJARAFE PROJECT

ALJARAFE PROJECT

First Underground Green Hydrogen Storage Facility in Spain

The global energy system’s transition towards a carbon-free economy has placed green hydrogen at the core of European decarbonization strategies. Its role as an energy carrier is essential for the gradual substitution of fossil fuels and for strengthening energy autonomy.

In this context, Trinity Energy Storage is leading the development of the Aljarafe Project, a pioneering initiative aimed at converting the former natural gas fields of San Juan, Palancares, and La Cerca—located 20 km from Seville—into Spain’s first underground green hydrogen storage facility, with commissioning expected by 2030.

Thanks to its excellent geological conditions for underground storage and its strategic location—adjacent to the future hydrogen backbone and situated in a region with major green hydrogen production projects—the Aljarafe Project stands out as an ideal candidate to become the first operational green hydrogen storage site in Spain.

From Natural Gas Production to Renewable Energy Storage

The Aljarafe Project entails the conversion of the Marismas C-1 and Rebujena Hydrocarbon Exploitation Concessions into a regulated hydrogen storage concession. The now-depleted reservoirs have a proven storage capacity, supported by five years of injection/withdrawal testing and by technical studies conducted by Geostock and NSAI—both internationally recognized entities in underground storage.

Over the past four years, the project's technical feasibility has been assessed through two R&D initiatives—UNDERGY and UES365—funded by CDTI under the Misiones Ciencia e Innovación programme. These projects have confirmed the excellent geological characteristics of the site for the underground storage of green hydrogen.

This groundwork has enabled Trinity to include Aljarafe in EUH2STARS, the largest European research project on hydrogen storage in depleted fields. The project is demonstrating the technical and economic feasibility of large-scale underground hydrogen storage systems. It is funded with €20 million from the European Union under Horizon Europe 2023 and includes major industrial partners such as RAG, SHELL, and HGS.

Existing Infrastructure, Energy Security, and Industrial Leadership

The existing gas infrastructure remains fully operational and is connected to the transmission network (Palancares Pipeline – F.06). Thanks to funding from the Horizon Europe – EUH2STARS project, basic engineering for the hydrogen storage system and the design of future monitoring networks are currently underway.

The forthcoming inclusion of the Aljarafe Project in the European Union’s list of Projects of Common Interest (PCI) will consolidate its strategic role in ensuring energy supply security and enabling the efficient integration of intermittent renewable energies. Through this, Trinity Energy Storage positions itself as a key operator in the management of resilient and secure energy infrastructure aligned with European climate objectives.

Operational Capacity and Contribution to the Energy System

The Aljarafe Project will make a tangible contribution to the stability and flexibility of the Spanish national energy system. Its operational capacity will enable the storage of green hydrogen during periods of high renewable generation and its release when demand requires it, promoting a dynamic balance between supply and demand. This functionality positions Aljarafe as a key vector for seasonal energy management, providing resilience, efficiency, and structural support to the energy transition.

The Operational Capacity and Storable Energy in the form of Green Hydrogen are in line with ongoing projects in Europe and the United States.

A Flagship Project for the Spanish Hydrogen Strategy

The Aljarafe Project represents a strategic opportunity to position Spain as a European leader in green hydrogen storage technologies, contributing decisively to national goals in decarbonization, energy sovereignty, and sustainable industrial development.