Thermo-economic comparison of CO2 and water as a heat carrier for long-distance heat transport from geothermal sources: A Bavarian case study

Deep geothermal energy has tremendous potential for decarbonizing the heating sector. However, one common obstacle can be the mismatch between geologically attractive regions in the countryside and urban areas with a high heat demand density, which are therefore attractive for district heating systems. In the last years, an increasing number of regions consider the transport of geothermal heat into urban clusters. One example of such a region is the South German Molasse Basin in Upper Bavaria. However, such heat transport pipelines come along with massive upfront investment costs due to the required large pipe diameter and insulation thickness. While the classic concept foresees the use of water as a heat carrier in such long-distance heat transportation pipelines, CO2 can be an attractive alternative. This study investigates the thermo-economic performance of CO2 as a heat transport carrier for a potential long-distance heat transmission pipeline with a length of 20 km, which could connect a planned geothermal project in the South of Munich with the existing district heating network of Munich. The results of the base case scenario demonstrate that for both heat carrier options water and CO2 rather low LCOH for the transport of the heat can be achieved. •A Bavarian case study for long-distance heat transport has been analysed.•CO2 and water-based systems LCOH are compared to identify the most attractive one.•The cost of the system appears to be dominated by the heat exchangers cost.•The LCOHs of the solutions are comparable but CO2 -based system is more flexible.