The potential of CO2-Plume Geothermal (CPG) Systems for CO2 component manufacturers: opportunities and development needs

Abstract

Subsurface reservoirs play an important role in decarbonizing the energy sector, be it through geothermal energy production or carbon capture and storage (CCS). In recent years, there has been an increasing interest in CO2-Plume Geothermal (CPG) systems, which combine CCS with geothermal, using CO2 instead of water as a subsurface heat and pressure energy carrier. As explained later in the paper, applying CO2 as a subsurface working fluid can be more efficient than water as it has a higher mobility (inverse kinematic viscosity) and as its large thermal expansion coefficient results in a thermosiphon effect that reduces the pumping power required. CO2 can also directly be utilized in a turbine for power generation. Furthermore, since CPG systems are added to full-scale CO2 Capture and Sequestration operations, all of the initially injected CO2 is ultimately stored. CPG therefore constitutes of both CO2 Capture Utilization as well as Storage. This paper assesses the huge technical potential of the CPG technology, identifying a potentially highly relevant market for CO2 equipment manufacturers and discusses the current research demand, based on the current state of the art of CO2 equipment. Both temperature and pressure levels are significantly lower than CO2 turbine designs investigated and proposed so far for other applications, such as waste heat recovery. Together with CPG-specific requirements, due to produced fluid impurities, it becomes evident that significant further development efforts are still necessary regarding future commercial CPG CO2 turbines.