Geothermal Energy and Data Centres in Spain: An Exploratory Framework for Sustainable and Efficient Digital Infrastructures

The rapid expansion of data centres poses challenges for energy planning and urban resilience. This study presents a reproducible, exploratory multi-criteria framework (Tier-0) to assess the suitability of geothermal energy for siting data centres across Spain’s 17 regions. Five dimensions were normalised on a 0–2 scale: geothermal resource (shallow; medium/high enthalpy), electrical and digital infrastructure, data centre demand, climate exposure, and territorial/social constraints, and integrated into two composite indices: GS_index (shallow) and GA_index (medium/high enthalpy or EGS). The indices were equally weighted and represented by terciles of the index scores. The results show that the GS_index ranges between 0.6–1.4 and GA_index between 0.8–1.6. Aragon, Asturias, and Cantabria are located in the upper tercile for GS; Aragon and Cantabria for GA, while Asturias (GS) and the Canary Islands (GA) illustrate cases of specialisation. Shallow geothermal energy depends less on resource availability, which is widely distributed, than on infrastructure and climate exposure (both with r ≈ 0.54 relative to GS). By contrast, deep resource availability is decisive for GA (ρ ≈ 0.53), reinforced by infrastructure and demand. The framework aligns with European decarbonisation and digitalisation strategies and contributes to the design of smart and resilient cities through evidence-based planning of critical infrastructure. Its limitations, such as regional scale, discrete normalisation, and aggregated social metrics, should be addressed in future research with higher spatial resolution and technical validations.