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Heat Mining Company LLC (HMC)

Geothermal energy offers clean, consistent, reliable electric power with no need for grid-scale energy storage, unlike wind and solar renewable power alternatives. However, geothermal development has lagged that of wind and solar and has considerable room for growth. Rapid implementation of new technologies is critical if geothermal is to play a part in the effort to address global warming and aid the world in moving to cleaner, renewable energy sources. Heat Mining Company LLC (HMC) provides a patent pending technology, carbon dioxide plume geothermal (CPG), that could support the rapid expansion of geothermal energy utilization by extracting geothermal heat from naturally porous, permeable geologic formations using carbon dioxide as the working heat exchange fluid.

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© Saar & Randolph

HMC’s proprietary CPG technology has the potential to enhance the feasibility and viability of carbon capture and storage (CCS) technology by offsetting or eliminating much of the cost of CCS through the generation of electricity by geothermal heat capture. CCS is the capture of carbon dioxide gas at the smoke stack or prior to the burning of fossil fuels such as coal. Captured CCS is then liquidified and pumped deep into the earth for permanent storage.

HMC’s proprietary technology was developed at the University of Minnesota in the Geofluids group, led by Dr. Martin Saar. Unlike traditional geothermal energy production which uses water as it working fluid for heat transfer, our technology, called carbon dioxide plume geothermal (CPG), utilizes stored supercritical carbon dioxide as its working fluid. Supercritical carbon dioxide (sCO2) is carbon dioxide gas which has been placed under pressure which turns the gas into a liquid. This liquid can then be handled in a manner similar to water for injection into deep storage reservoirs.

There are four distinct advantages for using CO2 as a working fluid.

First, CO2 is far more efficient as a heat transfer medium. This means CO2 is capable of producing commercially viable electrical energy at lower temperatures, at lower cost and in far more locations than tradition enhanced geothermal systems (EGS.)
• Direct CPG power system, T = 100 °C, P = 250 bar, k = 5x10-14 m2: 11.8% energy conversion efficiency.
  – Same formation but water/brine binary system: 3.4% efficiency.
• Direct CPG power system, T = 125 °C, P = 250 bar, k = 2.5x10-14 m2: 12.7% efficiency.
  – Same formation but water/brine binary system: 4.0% efficiency.
Second, CO2 mobility (density divided by dynamic viscosity) is significantly greater than H2O mobility:
  – Greater fluid flow and heat extraction from a reservoir.
  – Thermosiphon potential eliminates subsurface pumping requirements and improves efficiency.
  – Lower temperature and less permeable formations can be utilized than are viable with water, greatly increasing potential area of use.
Third, CPG provides a baseload renewable electricity source with greater than atmospheric operating pressure, requires a smaller equipment footprint than water-based facilities and is capable of operating at below water freezing temperatures.
Fourth, CO2 is a readily available, disposable commodity which when used reduces CO2 atmospheric release while preserving water resources.

For a map of some of the CCS sites around the world click this link:

Scottish Carbon Capture and Storage 



Our ultimate goal is to make CPG available around the world as the foremost method to reduce carbon emissions while building a lasting source of green electrical energy.