CO2-Plume Geothermal (CPG): the technology

CO2-Plume Geothermal (CPG) uses the advantages of CO2 as a geothermal working fluid to extract geothermal heat from naturally permeable reservoirs at ~2–5 km depth. Benefiting from increased mass flow due to its lower dynamic viscosity, the utilization of CO2 doubles to triples the geothermal energy extraction compared to brine. As CO2 is reinjected once the heat is extracted, all CO2 is permanently stored subsurface. Thereby, CPG turns CCS into true CCUS (Carbon Capture, Utilization and Storage)

Figure 1. Schematic of the CPG technology. After Randolph and Saar (2011), Adams et al. (2015, 2021), Garapati et al. (2015) and Fleming et al. (2020):

Since its inception in 2010 by Martin Saar and his team, the technology has secured 5 million USD in funding, resulting in patents and over 16 peer-reviewed publications.

Key CPG Publications

The Market for CO2 equipment for CPG

C. Schifflechner, J. de Reus, S. Schuster, A. C. Villasana, D. Brillert, M.O. Saar, H. Spliethoff,
‘”Paving the way for CO2-Plume Geothermal (CPG) systems: A perspective on the CO2 surface equipment”, Energy, ISSN 0360-5442, 2024, [Download PDF]

How, with the addition of a “shallow” reservoir, CPG can be used to store energy.

Fleming, Adams, Bielicki, Kuehn, Saar, Flexible CO2-Plume Geothermal (CPG-F): Using Geologically Stored CO2 to Provide Dispatchable Power and Energy Storage, Energy Conversion and Management, 253/115082, 2022. [Download PDF]

When liquid loading may occur in CPG production wells and how to avoid it.

Ezekiel, Adams, Ebigbo, Numerical analysis and optimization of the performance of CO2-Plume Geothermal (CPG) production wells and implications for electric power generation, Geothermics, 98/102270, 2022. [Download PDF]

Parameter sensitivity study on CPG power output performance.

Ezekiel, Kumbhat, Ebigbo, Adams, Saar, Sensitivity of Reservoir and Operational Parameters on the Energy Extraction Performance of Combined CO2-EGR–CPG Systems, Energies, 14/6122, 2021. [Download PDF]

Reservoir heat depletion during CPG and CPG parameter analysis and reservoir cooling, where the well design is varied.

Adams, Vogler, Kuehn, Bielicki, Garapati, Saar, Heat Depletion in Sedimentary Basins and its Effect on the Design and Electric Power Output of CO2 Plume Geothermal (CPG) Systems, Renewable Energy, 172, pp. 1393-1403, 2021. [Download PDF]

When to use geothermal systems in general and in particular CPG as a preheater.

Garapati, Adams, Fleming, Kuehn, Saar, Combining brine or CO2 geothermal preheating with low-temperature waste heat: A higher-efficiency hybrid geothermal power system, Journal of CO2 Utilization, 42, 2020. [Download PDF]

CCS and CPG after EOR.

Hefny, Qin, Saar, and A. Ebigbo, Synchrotron-based pore-network modeling of two-phase flow in Nubian Sandstone and implications for capillary trapping of carbon dioxide, International Journal of Greenhouse Gas Control, 103/1031642, 2020. [Download PDF]

How exothermic exsolution of water from CO2 in the CPG production well can significantly increase CPG-based power generation.

Fleming, Adams, Kuehn, Bielicki, Saar, Increased Power Generation due to Exothermic Water Exsolution in CO2 Plume Geothermal (CPG) Power Plants, Geothermics, 88/101865, 2020. [Download PDF]

Adding CPG after EGR.

Ezekiel, J., A. Ebigbo, B. M. Adams, and M. O. Saar, Combining natural gas recovery and CO2-based geothermal energy extraction for electric power generation, Applied Energy, 269/115012, 2020. [Download PDF]

How different (subsurface) fluid properties affect power generation and how to calculate the properties of geothermal working fluids.

Walsh, Garapati, Leal, Saar, Calculating thermophysical fluid properties during geothermal energy production with NESS and Reaktoro, Geothermics, 70, pp. 146-154, 2017. [Download PDF]

Calculating electric power output from thermal output for CPG systems and comparing it also to indirect systems such as ORCs.

Adams, Kuehn, Bielicki, Randolph, Saar, A comparison of electric power output of CO2 Plume Geothermal (CPG) and brine geothermal systems for varying reservoir conditions, Applied Energy, 140, pp. 365-377, 2015. [Download PDF]

CO2-limited CPG systems –> How much CO2 is needed. Use of horizontal wells and brine displacement by CO2.

Garapati, Randolph, Saar, Brine displacement by CO2, energy extraction rates, and lifespan of a CO2-limited CO2-Plume Geothermal (CPG) system with a horizontal production well, Geothermics, 55, pp. 182-194, 2015. [Download PDF]

CO2-thermosiphon effect in CPG.

Adams, Kuehn, Bielicki, Randolph, Saar, On the importance of the thermosiphon effect in CPG (CO2-Plume geothermal) power systems, Energy, 69, pp. 409-418, 2014. [Download PDF]

Main first CPG publication. Comparing thermal power output of CPG to CO2-EGS and to hydrothermal.

Randolph, J.B., and M.O. Saar, Combining geothermal energy capture with geologic carbon dioxide sequestration, Geophysical Research Letters, 38, L10401, 2011. [Download PDF]

CPG Consortium

Following extensive theoretical research, the next step is demonstrating CPG in the field. For this reason, a CPG Consortium has been formed in March, 2023. Leveraging the synergies of an end-to-end integrated academic and industry consortium, CPG systems can be investigated and efficiently field-demonstrated at reduced individual partner cost.

The objective of the CPG consortium is to demonstrate the potential and technical feasibility of commercial-scale CPG to enable Final Investment Decisions (FIDs) on subsequent commercial scale projects.

In Phase I of the consortium, a CPG field demonstration is prepared to demonstrate the technical feasibility of CPG. We are investigating both the overall CPG potential, using our in-house techno-economic simulator, as well as detailed site evaluation studies for candidate field demonstrations. We also investigate facility and equipment optimization opportunities and CO2 processing requirements. Following this two-year Phase I, the consortium will select the optimal site and field demonstration concept to execute during the subsequent Phase II of the consortium.

Consortium Partners

Highlights

Chair

Project Manager

Prof. Dr. Martin O. Saar

Jasper de Reus

Senior Researchers

Dr. Maren Brehme

Dr. Xiang-Zhao Kong

Dr. Mahmoud Hefny

Postdocs

Dr. Tsubasa Onishi

Process Engineers

Daniel Pokras

Doctoral Students

Kevin P. Hau

Serhat Küçük

Nicolas Rangel Jurado

Contact:

ETH Zurich
Institute of Geophysics
Geothermal Energy and Geofluids

Sonneggstrasse 5
8092 Zurich
Switzerland

Email
adereus(at)ethz.ch

CO2-Plume Geothermal (CPG): the technology

Key CPG Publications

CPG Consortium

Highlights

Benefits of CPG for CSS: CO2GeoNet Open Forum and EGU

CPG Consortium welcomes Holcim as partner

CPG Consortium welcomes Petrobras

TANGO techno-economic simulator milestone achieved

CPG consortium has started on March 2023

CPG Consortium Research Team