Closed Loop, Dry Rock Geothermal System for Permanent Military Bases

Geothermal energy is globally ubiquitous but its use is limited to hydrothermal (hot water) resources where high temperature rock is close to the earth’s surface (e.g. Iceland). But, drill deep enough anywhere and there is the heat needed to drive turbines to create electricity.  However, the high cost per kilowatt generated outside hydrothermal geography, is the clear barrier to utilization of this nearly unlimited energy resource.   Geothermal upfront capital cost is geology and geographic dependent and is usually higher than the cost of wind and solar. Ninety nine percent of geothermal energy produced today comes from hydrothermal resources that are only viable on 2% of the earth’s surface.  The remaining geothermal resources are in hot dry rock (HDR).  Although there has been significant investment to develop technologies for HDR reservoirs, field results have not yet proven them to be cost efficient.  Sage Geosystems has developed two proprietary technologies which allows us to harvest enough heat from one well to generate up to 10MW of electricity without drilling long, deep and expensive horizontal sections.  Sage has overcome the biggest barrier to success for past HDR systems, the low thermal conductivity of rock, with our proprietary HeatRoot technology. HeatRoot relies on increasing the effective thermal conductivity of a formation by creating hydraulic fracture(s) that grow downward several thousand feet. The resulting fractures act as chimneys funneling deep heat resources to our downhole heat exchanger at the bottom of the well via natural convection.  More efficient heat harvesting is achieved with a helical downhole heat exchanger that forces a working fluid to flow in a spiral fashion through the well bore and thus increases effective energy transfer from the formation to drive flash turbines at surface to generate electricity. Engineering and implementation of these technologies in the field requires optimization of multiple parameters. Our Phase 1 request is for developing multi-physics models using advanced commercial simulators like Comsol or Ansys and their calibration to match existing experimental and field results. The main challenges in using FEA and CFD simulations is solving transient heat transfer problems with up to 10^5 scale differences.  For the case of natural convection in fractures the challenge is also correctly modelling natural convection as a function of fracture size, opening and rheological properties of the slurry.  The main deliverables of the Phase 1 will be simplified numerical models validated against published data, which will be crucial for large scale deployment of these technologies. Sage will extensively collaborate with the Bureau of Economic Geology at the University of Texas. BEG researchers spearhead basic and applied research projects in energy resources and economics.