Paving the way for CO2-Plume Geothermal (CPG) systems: A perspective on the CO2 surface equipment
Christopher Schifflechner, Jasper de Reus, Sebastian Schuster, Andreas Corpancho Villasana, Dieter Brillert, Martin O. Saar, H. Spliethoff
Abstract
Subsurface reservoirs play an important role in decarbonizing the energy sector, be it through geothermal energy production or carbon capture and storage. In recent years, there has been an increasing interest in CO2-Plume Geothermal systems, which combine carbon sequestration with geothermal, using CO2 instead of water as a subsurface heat and pressure energy carrier. Since CO2-Plume Geothermal systems are added to full-scale CO2 Capture and Sequestration operations, all of the initially injected CO2 is ultimately stored. CO2-Plume Geothermal, therefore constitutes of both CO2 Capture Utilization as well as Storage. This paper assesses the huge technical potential of this 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. For a depth of 5 km, a typical one-stage radial turbine design might have a rotational speed of 23’000 rpm to 42’000 rpm and an impeller diameter between 96 mm to 155 mm. Together with technology-specific requirements, due to produced fluid impurities, it becomes evident that significant further development efforts are still necessary.