Sustainable Cascade Utilization of Low-Temperature Geothermal Resources for Electricity and Ultra-Low-Temperature District Heating

This study evaluates the sustainable cascade utilization of low-temperature geothermal resources (LTGR, <۹۰°C) for co-generating electricity and supplying ultra-low-temperature district heating (ULTDH). Using geothermal water from the C-PIG-۱ well in Poland's Podhale Basin (۸۲°C, ۵۱.۲۲ kg/s), thermodynamic models were developed using NIST REFPROP to compare Organic Rankine Cycle (ORC) and Kalina Cycle performance. The cascade system prioritizes electricity generation, followed by ULT DH supply (۵۰-۶۰°C). Results show the Kalina Cycle outperforms ORC, delivering ۴۳۲ kW gross power, ۶.۶% efficiency, and ۱.۷۳ GWh/year of electricity under full-flow conditions. ORC with R۱۳۴a yields ۲۳۴ kW and ۷.۵% efficiency. Annual CO۲ emissions are reduced by ۶۹۲ tons compared to natural gas-based grid electricity and heating. Demand variability was modeled using an Artificial Neural Network (ANN), revealing ramp rates within ±۰.۰۲ (۹۸% of cycles), manageable via thermal buffering. Capacity factors range from ۵۸-۶۰%, confirming high reliability. This work presents the first integrated cascade + ULT DH + ANN demand forecasting model for Polish sedimentary basins, offering a scalable framework for sustainable geothermal deployment in Central Europe.

Keywords:

Low-temperature geothermal , ORC , Kalina Cycle , cascade utilization , ultra-low-temperature district heating , CO۲ reduction , Poland , ANN forecasting