Aquifer Thermal Energy Storage (ATES) systems are a promising solution for sustainable energy storage, leveraging underground aquifers to store and retrieve thermal energy for heating and cooling. As the global energy sector faces rising energy demands, climate change, and the depletion of fossil fuels, transitioning to renewable energy sources is imperative. ATES systems contribute to these efforts by reducing greenhouse gas (GHG) emissions and improving energy efficiency. This review uses the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) methodology as a systematic approach to collect and analyze relevant literature. It highlights trends, gaps, and advancements in ATES systems, focusing on simulation methods, environmental impacts, and economic feasibility. Tools like MODFLOW, FEFLOW, and COMSOL Multiphysics are emphasized for optimizing design and system performance. Europe is identified as a continent with the most favorable predispositions for ATES implementation due to its diverse and abundant aquifer systems, strong policy frameworks supporting renewable energy, and advancements in subsurface energy technologies.

This study presents a structured evaluation of key factors influencing the design of shallow geothermal (SG) hybrid heating and cooling systems in the Danube Region. As part of the Danube GeoHeCo project, a criteria catalogue was developed using the Analytic Hierarchy Process (AHP) to support the creation of an IT decision support tool. Through expert-based pairwise comparisons and eigenvalue analysis, the relative weights of technical, geological, socioeconomic, and environmental criteria were derived. Results show that thermal demand, drilling costs, and hydrogeological site characteristics are the most influential parameters. The final ranked list of twenty sub-criteria provides a basis for prioritizing input data and optimizing early-stage system design. This framework supports more efficient project planning, targeted data collection, and the development of robust shallow geothermal hybrid solutions aligned with regional energy transition goals.