A Hybrid Geothermal Energy Conversion Technology - A Potential Solution for Production of Electricity from Shallow Geothermal Resources

Nagasree Garapati, Benjamin M. Adams, Jeffrey M. Bielicki, Philipp Schaedle, Jimmy B. Randolph, Thomas H. Kuehn, Martin O. Saar

Research output: Contribution to journalConference articlepeer-review

10 Scopus citations

Abstract

Geothermal energy has been successfully employed in Switzerland for more than a century for direct use but presently there is no electricity being produced from geothermal sources. After the nuclear power plant catastrophe in Fukushima, Japan, the Swiss Federal Assembly decided to gradually phase out the Swiss nuclear energy program. Deep geothermal energy is a potential resource for clean and nearly CO2-free electricity production that can supplant nuclear power in Switzerland and worldwide. Deep geothermal resources often require enhancement of the permeability of hot-dry rock at significant depths (4-6 km), which can induce seismicity. The geothermal power projects in the Cities of Basel and St. Gallen, Switzerland, were suspended due to earthquakes that occurred during hydraulic stimulation and drilling, respectively. Here we present an alternative unconventional geothermal energy utilization approach that uses shallower, lower-temperature, naturally permeable regions, that drastically reduce drilling costs and induced seismicity. This approach uses geothermal heat to supplement a secondary energy source. Thus this hybrid approach may enable utilization of geothermal energy in many regions in Switzerland and elsewhere, that otherwise could not be used for geothermal electricity generation. In this work, we determine the net power output, energy conversion efficiencies, and economics of these hybrid power plants, where the geothermal power plant is actually a CO2-based plant. Parameters varied include geothermal reservoir depth (2.5-4.5 km) and turbine inlet temperature (100-220 °C) after auxiliary heating. We find that hybrid power plants outperform two individual, i.e., stand-alone geothermal and waste-heat power plants, where moderate geothermal energy is available. Furthermore, such hybrid power plants are more economical than separate power plants.

Original languageEnglish (US)
Pages (from-to)7107-7117
Number of pages11
JournalEnergy Procedia
Volume114
DOIs
StatePublished - 2017
Event13th International Conference on Greenhouse Gas Control Technologies, GHGT 2016 - Lausanne, Switzerland
Duration: Nov 14 2016Nov 18 2016

Bibliographical note

Funding Information:
This work was supported in part by a Sustainable Energy Pathways (SEP) grant from the U.S. National Science Foundation (NSF) under Grant Number SEP-1230691. Martin Saar additionally thanks the Werner Siemens Foundation for their endowment of the Geothermal Energy and Geofluids Chair at ETH-Zurich (ETHZ). Any opinions, findings, conclusions, and/or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF, ETHZ, or the Werner Siemens Foundation.

Keywords

  • CO Plume Geothermal (CPG) energy
  • auxiliary heating
  • carbon capture utilization and sequestration (CCUS)
  • hybrid system

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