Open Access

Niklas Scholliers, Max Ohagen, Lukas Seib, Laura Belzner, Liselotte Schebek, Ingo Sass, Clemens Rohde

• High-Temperature Aquifer Thermal Energy Storage (HT-ATES) offers large-scale, low-cost seasonal heat storage, enabling surplus-heat utilization and improving the environmental performance of district heating networks (DHNs). However, prospective dynamic scenario assessments of integrating HT-ATES into transitioning DHNs are scarce. We evaluate the environmental-economic performance of evolving HT-ATES capacity at three candidate sites in Mannheim's third-generation DHN as the system transitions toward renewable heat supply. A generalized multi-model framework combines geological subsurface characterization and thermo-hydraulic simulation with dynamic life-cycle assessment and life-cycle costing across future DHN technology configurationsHigh-Temperature Aquifer Thermal Energy Storage (HT-ATES) offers large-scale, low-cost seasonal heat storage, enabling surplus-heat utilization and improving the environmental performance of district heating networks (DHNs). However, prospective dynamic scenario assessments of integrating HT-ATES into transitioning DHNs are scarce. We evaluate the environmental-economic performance of evolving HT-ATES capacity at three candidate sites in Mannheim's third-generation DHN as the system transitions toward renewable heat supply. A generalized multi-model framework combines geological subsurface characterization and thermo-hydraulic simulation with dynamic life-cycle assessment and life-cycle costing across future DHN technology configurations and global development pathways. HT-ATES integration is benchmarked against no-integration and evaluated using eco-efficiency metrics. Over 30 years, the best-performing site under a middle-of-the-road pathway achieves net savings of 142 kt CO2e, 808 MEUR in avoided external damage costs, and 116 kEUR in internal cost savings. Across scenarios, net savings range from 107 to 395 kt CO2e and 644 - 4441 MEUR in avoided external damage costs, while internal costs range from 0.12 MEUR in savings to a 9.5 MEUR net increase. Site-to-site differences are modest; results are driven primarily by consequential modeling choices and scenario assumptions regarding DHN technologies, energy costs, and background inventories. Economic outcomes are sensitive to discount rate, heat-pump cost and lifetime, and displaced heating technologies. Overall, the case study indicates substantial emission reductions and large avoided external damage costs, but limited economic life-cycle viability for decarbonizing DHNs. While results are network- and scenario specific, the methodology provides a transferable framework for integrated HT-ATES evaluation across subsurface settings and DHNs.…