Linking geothermal district heating with Direct Air Capture

Achieving net-zero emissions and combating climate change necessitate the adoption of negative emission technologies. Direct Air Capture (DAC), which removes CO2 directly from ambient air, shows great promise but requires significant energy, particularly in the form of heat. Geothermal doublets are traditionally used to supply heat for district heating networks, which operate at lower temperatures than those required for DAC. This study explores integrating geothermal heat from a doublet with DAC using a heat pump, while repurposing waste heat from the DAC process to support district heating. We propose multiple operational configurations for this system and conduct a life cycle emissions analysis, demonstrating the potential to capture tens to hundreds of thousands of tonnes of CO2 over its lifetime. The results show that higher geothermal fluid temperatures and flow rates substantially lower the cost per tonne of CO2 captured. Conversely, higher fluid temperatures combined with lower flow rates reduce overall system costs. These findings highlight the critical role of optimal subsurface conditions in maximizing system efficiency.