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AKE: Arbeitskreis Energie

AKE 1: Renewable Energy - Biomass, Geothermal Energy and CO₂-Sequestration

AKE 1.2: Invited Talk

Monday, March 7, 2016, 10:00–10:30, H3

Combined CO₂-storage and geothermal energy extraction: potential and options — •Martin O. Saar — ETH Zurich, Switzerland

Using carbon dioxide (CO₂) as the geothermal energy extraction fluid has several advantages over water such as 1) the energy conversion efficiency to electricity is typically twice that of water, 2) valuable water resources are protected, and 3) the system results in permanent geologic CO₂ sequestration, a key method to mitigate global climate change. The result is a high-efficiency CO₂-sequestering geothermal power plant with a negative carbon footprint that can operate in regions with relatively low geothermal heat flow and/or low reservoir permeabilities. As a result, this technology expands the geothermal resource base, while making carbon capture and storage (CCS) more economically competitive. Furthermore, such a renewable, geothermal power plant may be combined with other unconventional geothermal technologies such as auxiliary heating of geothermally preheated geofluids. Potential challenges of CO₂-geothermal systems include ensuring caprock integrity, CO₂ availability, and general public acceptance of underground CO₂storage technologies.

In this presentation, I will address the potential of, and various options for, CO₂-based and other unconventional geothermal systems, particularly for relatively low subsurface heat flow conditions as those that exist throughout Germany. I will also point out the challenges of CO₂-based geothermal energy extraction and provide some examples of research addressing those challenges.