A major challenge in accelerating the energy transition across the Mediterranean region is identifying locations where innovative energy solutions can be most effectively implemented. Within the STORM project, the University of Campania Luigi Vanvitelli leads the development of an advanced zonation framework designed to support the deployment of Seasonal Thermal Energy Storage (STES) systems across Mediterranean contexts.
The framework aims to produce a scientifically robust suitability map of the Mediterranean region by integrating climatic, geological, energy demand, and technological data within a Geographic Information System (GIS)-based decision-support platform. This approach enables the identification of areas with the highest potential for seasonal thermal energy storage applications and supports informed planning and design processes.
Why a GIS-Based Zonation Approach?
The performance of STES systems is highly dependent on local conditions (climate, geology, energy demands and heating/cooling technologies). To address these factors, STORM developed a data-driven zonation methodology capable of translating complex spatial datasets into practical information for planners, engineers, policymakers, and stakeholders.
The framework was implemented using QGIS, a leading open-source GIS platform. QGIS enables the integration of raster and vector data, the generation of thematic maps, and the analysis of spatial relationships among multiple variables.
Climate Indicators: Understanding Thermal Needs
Climate is a key factor of seasonal thermal storage performance. Three indicators were considered:
- annual Heating Degree Days (HDD);
- annual Cooling Degree Days (CDD);
- annual Average Solar Global Horizontal Irradiation (GHI).
HDD and CDD quantify annual heating and cooling requirements, respectively, providing a comprehensive representation of thermal/cooling loads. GHI was included because solar energy serves as the primary charging source for seasonal storage systems coupled with solar thermal technologies.
The climatic datasets were obtained from internationally recognized sources, including Global Solar Atlas (https://globalsolaratlas.info/map) and DegreeDays.net (https://www.degreedays.net/). Spatial processing and interpolation techniques were applied to generate consistent climate layers across all countries involved in the STORM project.
Geological Indicators: Assessing the Subsurface Potential
Subsurface conditions directly affect the feasibility and efficiency of underground thermal energy storage. Geological analysis focused on three parameters:
- average soil thermal conductivity (W/mK);
- average soil density (kg/m3);
- average soil volumetric heat capacity (MJ/m³K).
Thermal conductivity reflects the ability of soil to transfer heat by conduction, while volumetric heat capacity represents the amount of thermal energy that can be stored within a given volume. These parameters were derived using the Global Lithological Map (GLiM), developed by the University of Hamburg (https://www.geo.uni-hamburg.de/en/geologie/forschung/aquatische-geochemie/glim.html), combined with representative thermal properties obtained from scientific literature.
The resulting geological layers identify areas where subsurface conditions are most favorable for thermal storage processes.
Energy Demand Indicators
This section incorporates indicators representing building energy demands estimated by combining climatic conditions with representative features of regional building stocks.
Two indicators were considered:
- average annual heating energy demand (kWh/m²);
- average annual cooling energy demand (kWh/m²).
These variables constitute essential inputs for sizing seasonal storage systems, determining storage capacities, and defining charging/discharging cycles. The assessment methodology was adapted from established scientific literature to reflect Mediterranean conditions.
Heating and Cooling Technologies
The distribution of existing heating and cooling technologies is particularly relevant because it determines opportunities for integrating STES solutions.
Country-specific analyses were conducted for Italy, Spain, Cyprus, Jordan, and Lebanon using official statistics, reports from national/international organizations, together with peer-reviewed scientific literature. This technological mapping provides a realistic representation of current energy infrastructures and highlights potential pathways for STES integration.
Supporting Decision-Making and System Design
The Mediterranean zonation framework forms the basis of a broader digital decision-support ecosystem that will be integrated into the STORM digital platform.
By combining climate, geology, energy demand, and technological information, the framework enables preliminary assessments of STES potential across the Mediterranean region. The resulting maps support site selection, identify opportunities and constraints, and provide essential inputs for subsequent numerical simulations and system design activities. Ultimately, the framework reduces uncertainty during early project development stages and facilitates the deployment of efficient, resilient, and sustainable thermal energy systems throughout the Mediterranean basin.
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