The multi-functionality of geologically sequestered carbon dioxide: From geothermal energy extraction to renewable energy storage. Martin O.

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1 The multi-functionality of geologically sequestered carbon dioxide: From geothermal energy extraction to renewable energy storage Midwest Groundwater Conference, Oct. 2, 2012 Martin O. Saar Associate A i P Professor f Gibson Chair of Hydrogeology and Geofluids Department of Earth Sciences University of Minnesota (Chi f S (Chief Scientific i tifi Offi Officer off H Heatt Mi Mining i C Company LLC) Collaborators / co-pis / Students / Postdocs/ Industry - Jimmy Randolph, Stuart Walsh, Scott Alexander, Bill Seyfried Jr., Jr Harvey Thorleifson, Thorleifson Joe Myre, Myre P.-H. Kao, Ryan Toot, Ben Tutolo, Xiang-Zhao Kong (GEO, UMN) - Tom Kuehn, Ben Adams, Andy Mevissen (ME, UMN) - Melisa Pollak, Jeff Bielicki (Humphrey Institute, UMN) - Steven Taff, Nathan Paine (Applied Economics, UMN) - Karsten Pruess, Stefan Finsterle (LBNL + on SAB of HMC) - William Gosnold (UND + on SAB of HMC) - Russ Straate, Leza Besemann, Clay Parker (OTC, UMN) - Ken Carpenter, Jimmy Randolph (HMC)

2 Why geothermal energy? Out of sight out of mind Wind and solar get all the publicity it because we can see their effects more easily: On SAFL s home page Solar power plant in Mohave desert

3 Why geothermal energy? Effects of geothermal power can be seen as they are driving some of Earth s most energy-intensive processes over local to global scales: Mantle convection Earthquakes ( ) Mountain formation modified from S. Rost, 2008 movie from Nasa Himalayas photo from Nasa Volcanism Geysers Black smoker Himalayas photo from USGS Brantley (1983) Photo from NOAA

4 Where does Earth s Heat come from? 1) Gravitational Compression (formation of Earth) 2) Accretion (Impacting of extraterrestrial objects) 3) Radioactive decay of unstable elements 4) Latent heat of crystallization (Ni, Fe in outer core) Core Temperature > 4000 C

5 Global heat flow areally weighted global mean: 87 mw/m 2 mean: 65 mw/m 2 mean: 101 mw/m 2 heat flow (mw/m 2 ) Pollack et al., Rev. Geophys., 1993

6 Earth s Total Geothermal Power Surface area of Earth: 5x10 14 m 2 Multiply by areally weighted mean global heat flow of 87 mw/m 2 to get: Global Mean Geothermal Power = 4.4*10 13 Watts = 44 Tera Watts [TW]

7 Global Heat Flow Uneven Geothermal Power Distribution mean continental mean global mean oceanic C/km Pollack et al., Rev. Geophys., 1993

8 U.S. Heat Flow Blackwell et al., s 40s 50s 60s 70s 80s 90s mw/m

9 Focusing of otherwise diffusive heat flow from the Earth 1) due to localized tectonic and/or magmatic activity. 2) due to groundwater flow collecting diffusive heat and discharging it at hot springs. hot springs mountain, volcano cold springs basin, graben hot springs Ring of fire heat USGS Earth s mantle or magmatic intrusion

10 Thus geothermal regions arise and are classified as: a) low-temperature: <90 C (<194 F) b) moderate temperature: C ( F) c) high temperature: >150 C (>300 F) Temperature influences use options:

11 Temperature influences use options: F C 32 ice boiling Low Temp. Moderate Temp. High Temp. heat pumps direct use electricity use soil or groundwater as a heat source/sink [installation of 10,000 to 40,000 systems/year] heat buildings,green houses, factories, etc. [470 MW heats ~40,000 houses] ~2200 MW in U.S.A. [~4 large nuclear power plants] Renewable energy ranks: 1) Hydroelectric 2) Biomass 3) Geothermal 4) Solar 5) Wind

12 F C 32 ice boiling Low Temp. Moderate Temp. High Temp. heat pumps direct use electricity Source: Geothermal Research Council (GRC)

13 F C 32 ice boiling Low Temp. Moderate Temp. High Temp. heat pumps direct use electricity New Zealand Examples Japan Long Valley Caldera, CA Geysers, CA

14 U.S. Geothermal Provinces electricity direct use heat pumps Source: UURI & GRC

15 U.S. Geothermal Provinces Three conditions must be met for geothermal electricity production: 1) High subsurface temperatures 2) Large amount of geothermally heated fluid 3) High porosity and permeability reservoir With water as the working fluid: not much water hot dry rock Enhanced Geothermal Systems (EGS) Figure: GRC

16 Enhanced/Engineered Geothermal Systems (EGS) EGS hot, dry rock Problems: - induced seismicity - small reservoir - difficult to induce water circulation - loss of water hydrofractured reservoir Both figures from GRC

17 CO 2 Plume Geothermal (CPG) Carbon Dioxide Plume Geothermal (CPG) technology: Developed at the University of Minnesota (UMN) by Drs. Martin Saar, Jimmy Randolph, and Thomas Kuehn UMN filed for CPG patents in March, 2009 (U.S. and International), ti U.S. patent t allowed July 2012; Additional patents for CPG EOR applications filed in 2012 Heat Mining Company LLC (UMN Startup) has been granted an exclusive, worldwide license to CPG Randolph and Saar, 2011

18 CPG Projects Geoscience: - CO2 injection, storage, and production (reservoir scale) - heat transfer, heat depletion, pressure evolution (reservoir scale) - fluid-mineral reactions and permeability field changes (pore-scale) Mechanical Engineering: - power conversion (direct/indirect), co-production of district heat - fluid preconditioning (after subsurface and before turbine) - fluid pre-reinjection conditioning (before compression) Applied Economics: - cost and revenue for various scenarios (CO2 costs/revenue, electricity price variations, energy storage, incentives, etc.) Policy: - evaluation of different policies in different countries/states - effects of regulations, policies, laws, etc. - GIS modeling of geoscience, ME, AE, policy, grid, CO2 pipelines, etc. Commercialization - Office for Technology Commercialization at UMN patenting, startup: - Heat Mining Company LLC (granted exclusive worldwide license)

19 Res servoir r water-based reservoir geothermal (the classic approach) natural geothermal system (no CO 2 usage and thus not as efficient + no CCS) Water CO 2 Reservoir caprock reservoir Our proposed system: CO 2 -plume geothermal (CPG) system in a natural high- porosity, high-permeability reservoir with overlaying caprock at moderate depths of 1-4 km. significant CO 2 sequestration University of Minnesota (patent filed 2010) H 2 O CO 2 EG GS loss of water, (no CO 2 usage and thus not as efficient + no CCS) water-based EGS (has been proposed and partially implemented before) Enhanced Geothermal Systems (EGS) small CO 2 storage Hydraulic fracturing of hot, dry rock at great depths (causes earthquakes several projects stopped) CO 2 -based EGS (has been proposed before)

20 Res servoir r water-based reservoir geothermal (the classic approach) natural geothermal system (no CO 2 usage and thus not as efficient + no CCS) Water CO 2 Reservoir caprock reservoir Our proposed system: CO 2 -plume geothermal (CPG) system in a natural high- porosity, high-permeability reservoir with overlaying caprock at moderate depths of 1-4 km. significant CO 2 sequestration University of Minnesota (patent filed 2010) H 2 O CO 2 EG GS loss of water, (no CO 2 usage and thus not as efficient + no CCS) water-based EGS (has been proposed and partially implemented before) Enhanced Geothermal Systems (EGS) small CO 2 storage Hydraulic fracturing of hot, dry rock at great depths (causes earthquakes several projects stopped) CO 2 -based EGS (has been proposed before)

21 Proposed here: CO 2 Plume Geothermal (CPG) Motivation: large-scale l geologic CO 2 sequestration ti is creating significant fluid reservoirs U.S.: 500 large coal-fired power plants, 5,000 natural gas power plants, ethanol plants, industry, etc. (DOE 2009)

22 The CO 2 sequestering geothermal power plant (Saar, Randolph, and Kuehn, University of Minnesota, patent filed 2009) CO 2 -Plume Geothermal (CPG) Concept CO 2 injection as part of CO 2 sequestration in deep saline aquifers or into hydrocarbon reservoirs for enhanced oil recovery (EOR). or hydrocarbons (e.g., oil, natural gas)

23 Why use CO 2 for geothermal energy capture? - Vigorous CO 2 thermosyphon - Greater fluid flow and heat extraction from a reservoir CO 2 mobility >> H 2 O mobility Density more T-dependent for CO 2 than for H 2O ~20 o C Fluid density profiles ~100 o C Water (2.5km) Water (1 km) CO 2 (2.5 km) CO 2 (1 km) Randolph and Saar, 2011

24 Why use CO 2 for geothermal energy capture? Availability, disposable commodity (reduces CO 2 atmospheric release, preserves water resources) Provides a baseload or peak renewable electricity source CO 2 mobility (density divided by dynamic viscosity) is significantly greater than H 2O mobility: Greater fluid flow and heat extraction from a reservoir. Thermosyphon 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. Geothermal power plant benefits: Higher efficiency power systems versus water/brine. Greater-than-atmospheric operating pressure. Smaller equipment footprint than water-based facilities. Capable of operating at below water freezing temperatures.

25 CPG model description 2-part modeling process: initial reservoir and well-pattern description with TOUGH2, then massive exploration of parameter space and risk assessment modeling with GSC code. One code informs the other. TOUGH2 with ECO2N module Components: CO 2, H 2 O and (optional) NaCl Five-spot well pattern 36 grid blocks, 70.7m by 70.7m by 305m each 707m from injection to production well Only 1/8 th of fdomain need dbe modeled Map view 500 m m Injection Production o Randolph and Saar, 2011

26 CPG-Base Case Model description Initial conditions For a given model, all pore space assumed occupied CO 2 (CO 2 displacement of H 2 O not considered) Reservoir temperature = 100 O C Reservoir pressure = 250 bar (approx. 2.5 km deep formation) Boundary conditions No-fluid-flow boundaries Semi-analytic conductive heat exchange with over and underlying confining beds Injection/production conditions 20 bar pressure difference between injection/production wells 20 O C pure CO 2 injected and produced at rate determined by pressure gradient between wells

27 Pressure-enthalpy diagram for CO CPG 2 ure, MPa Pressu Geothermal heating Pressurize Expansion (turbine) Heat Rejection (Cooling Tower) 2

28 Mass Flowrate Effects Minimal Parasitic Losses Electricity Product ion Per We ell [kwe] Formation T = 100 o C, P = 250 bar, permeability = 5x10-14 m Formation T = 100 o C, P = 250 bar Mass Flowrate [kg/s] Brine Net Brine Pumping Power Brine Gross CO 2 Indirect CO 2 Direct

29 Power Production with Energent CO 2 Turbine CO 2 vs Brine Electrical Energy Production, with Energent Projections Single Well Flow Rate = 80 kg/s, Permeability = 5 x m Elec ctricity Prod duction [kw We] Time [years] Indirect Brine [80 kg/s] Direct CO2 [80 kg/s], Energent

30 Energent, 2012 Higher efficiency power system than water, 76 to 85% depending on T,P. Smaller equipment footprint than water-based facilities. Capable of operating at below water freezing temperatures.

31 Examples Energy conversion efficiency T = 100 o C, P = 250 bar, k = 5x10-14 m 2 Direct CPG power system: 11.8% energy conversion efficiency. Same formation but water/brine binary system: 2.8% efficiency. T = 125 o C, P = 250 bar, k = 5x10-14 m 2 Direct CPG power system: 14.0% efficiency. Same formation but water/brine binary system: 8.1% efficiency. Thank you.

32 Expansion of the geothermal resource base Results of CPG simulations: i CO 2 mass flow rates through sedimentary geothermal aquifers are 47to59timesthoseofHO times those of 2 CPG heat mining rates are 2.3 to 2.9 times those of conventional H 2 O-based reservoir geothermal CPG heat mining rates are 4.3 to 5.7 times those of H 2 O-based EGS Randolph and Saar, 2011