GEO.MAT – Efficiency increase of geothermal energy systems with heat pumps

Austrian thermal spas are energy‑intensive facilities: 60–70% of their heat demand is used to keep pool water warm. At the same time, geothermal thermal water is often discharged as splashing water at about 30°C without using its remaining energy. GEO.MAT targets this untapped potential and develops practical pathways for decarbonising thermal spas.

The project plans, simulates and implements integrated measures at two demonstration sites (Sonnentherme Lutzmannsburg and H2O Hotel‑Therme Bad Waltersdorf) plus a transfer site (Reduce Bad Tatzmannsdorf): (1) recovery of waste heat sources such as splashing water (~30°C), ventilation/AC cooling water and drinking‑water cooling; (2) cascaded heat pump systems and optimised heat exchangers for low pool supply temperatures; (3) thermal storages and the use of pools as flexibility elements for peak shaving and load shifting.

At the core is a digital energy management system combining data‑ or model‑predictive control (DPC/MPC). A Python‑based dynamic optimisation model (incl. MILP) supports component sizing and load‑point‑optimised operation of heat pumps, storages and grid connections (e.g., bidirectional district heating/cooling coupling). First potential studies indicate substantial savings from waste‑heat recovery and efficiency measures—the two demonstrator concepts targets annual CO₂ reductions on the order of 1.200 t to 2,000 t. The outcomes will be consolidated into replicable integration concepts and a roadmap to speed up roll‑out to further spas in Austria and Central Europe.