Sustainable and Scalable Geothermal Energy Connecting thermodynamic, environmental and economic criteria

Sustainable and Scalable Geothermal Energy Connecting thermodynamic, environmental and economic criteria Jefferson Tester Cornell Energy Institute and Atkinson Center for a Sustainable Future Cornell University, Ithaca, NY 14853, USA West Virginia Geothermal Conference Marshall Univeristy Flatwoods, West Virginia May 22, 2012

Sustainable and Scalable Geothermal Energy Connecting thermodynamic, environmental and economic criteria How geothermal is used today Characteristics and extent of geothermal resources How geothermal energy is extracted Environmental impacts and benefits Sustainability of geothermal systems Economics issues facing growth of geothermal

Exploring our options for long term sustainability Making good choices requires comprehensive analysis and assessment

Choosing Among Options so where is geothermal? Global Energy Inventory -today and tomorrow hydro limit (0.7 TW) wind theoretical limit all class 3 (5.1 m/s 10 m above ground) (2.1 TW) nuclear... 8000 new nuclear power plants (8 TW) renewable (0.29) nuclear (0.83) hydro (0.29) biomass (1.21) coal (2.96) biomass... 1.28 10 13 m 2 20% earth's surface all cultivatable land used for biomass (7-10 TW) gas (2.70) oil (4.52)

The Geothermal Option perhaps the least understood and most undervalued Accessible Pressure Temperature Domain of Earth s Geosphere Geothermal energy in use today

Utilization of Geothermal Energy 1. For Electricity -- as a source of thermal energy for base load electricity 2. For Heating -- direct use of the thermal energy in district heating or industrial processes 3. For Geothermal Heat Pumps as a source or sink of moderate temperature energy in heating and cooling applications

Geothermal systems common characteristics and limitations An accessible, sufficiently high temperature rock mass underground Connected well system with ability for water to circulate through the rock mass to extract energy Production of hot water or steam at a sufficient rate and for long enough period of time to justify financial investment Means of directly utilizing or converting the thermal energy to electricity Hydrothermal Reservoirs

Today there are over 11,000 MWe on-line worldwide In USA 3100 MWe on-line + 800 MWe under construction A.S. Batchelor, 2005; Bertani,2008; GEA, 2009; and IPCC 2010 But, the US has 1,000,000 MWe of capacity and consumes about 100 EJ of primary energy per year

How can geothermal become a major supplier of primary energy in the United States? Three key underlying questions Thermodynamics Does our use of primary energy today properly address its thermodynamic potential? Sustainability -- What are the requirements for a sustainable EGS reservoir -- environmental impacts and benefits, reservoir productivity, lifetime, and renewablility/recoverability? Economics - What will it take for Geothermal (both EGS and hydrothermal) to achieve its market potential as national resource for primary energy?

Lessons from thermodynamics -- exergy and availability -- Conversion of geothermal heat into electricity is limited by its relatively low source temperatures - 150 to 250 o C Most Geothermal Resources

Options for converting geothermal heat into electricity Organic binary cycle Steam flashing cycle Trilateral supercritical vapor cycle

The Thermal Spectrum of U.S. Energy Use Energy consumed as a function of utilization temperature About 25% of US energy use occurs at temperatures < 100 o C and most of it comes from burning natural gas and oil With electrical losses by J.W. Tester, D.B. Fox and D. Sutter, Cornell University 2010

Iceland s transformation utilized geothermal for both electricity and heat! In Iceland today more than 95% of all heating needs are provided by geothermal energy Figure 1 - Cloud of smoke from space heating by coal over Reykjavik in the 1940 (Sturludóttir, 2007). Figure 2 - Clear day in modern Reykjavik (Stone, 2006).

Geothermal has enabled Iceland s transformation In 50 years Iceland has transformed itself from a country 100% dependent on imported oil to a renewable energy supply based on geothermal and hydro >95% of all heating provided by geothermal district heating >20% of electricity from geothermal remainder from hydro 2 world scale aluminum plants powered by geothermal Currently evolving its transport system to hydrogen/hybrid/electric systems based on high efficiency geothermal electricity Condensers and cooling towers, The Geysers, being fitted with direct contact condensers developed at NREL The Blue Lagoon in Iceland

How can geothermal become a major supplier of primary energy in the United States? Three key underlying questions Thermodynamics Does our use of primary energy today properly address its thermodynamic potential? Sustainability -- What are the requirements for a sustainable EGS reservoir -- environmental impacts and benefits, accessability, reservoir productivity, lifetime, and renewablility/recoverability? Economics - What will it take for Geothermal (both EGS and hydrothermal) to achieve its market potential as national resource for primary energy?

Environmental impacts and benefits Water use will require effective control and management, especially in arid regions Land use small footprint compared to alternatives Induced seismicity must be monitored and managed Low emissions, carbon-free base load energy No storage or backup generation needed Adaptable for district heating and co-gen / CHP applications

Environmental impacts and benefits Water use will require effective control and management, especially in arid regions Land use small footprint compared to alternatives Induced seismicity must be monitored and managed Low emissions, carbon-free base load energy No storage or backup generation needed Adaptable for district heating and co-gen / CHP applications

The footprint of geothermal power developments is small Source - The Future of Geothermal Energy, MIT report (2006)

Accessibility to stored thermal energy needed -- a efficient mine or farm energy stored in rock 14 million EJ stored to 10 km compared to 100 EJ/yr of primary energy used Blackwell and Richards, SMU 2007 May 28, 2012 J.W. Tester, B. Anderson, K. Beckers, D.B. Fox, M.Z. Lukawski 19

A range of resource types and grades within the geothermal continuum Three critical ingredients for successful heat mining 1. sufficient temperature at reasonable depth 2. sufficient permeability 3. sufficient hot water or steam 6

Enhanced/Engineered Geothermal Systems (EGS) could provide a pathway to universal heat mining EGS defined broadly as engineered reservoirs that have been stimulated to emulate the production properties of high grade commercial hydrothermal resources.

The Future of Geothermal Energy Transitioning from Today s Hydrothermal Systems to Tomorrow s Engineered Geothermal Systems (EGS) -- Primary goal: to provide an independent and comprehensive evaluation of EGS as a major US primary energy supplier -- Secondary goal: to provide a framework for informing policy makers of what R&D support and policies are needed for EGS to have a major impact An MIT led study by an 18- member international panel Full report available at http://www1.eere.energy.gov/geothermal/ future_geothermal.html

30+ Year History of EGS Research Cooper Basin (Australia) Newberry EGS Demonstration (USA) Future US EGS Program EGS CORE KNOWLEDGE BASE Soultz (EU) Basel (Swiss) Fenton Hill (USA) Coso & Desert Peak (USA) Hijiori & Ogachi (Japan) Landau, et al (Germany) Rosemanowes (UK)

Developing stimulation methods to create a well-connected reservoir The critical challenge technically is how to engineer the system to emulate the productivity of a good hydrothermal reservoir Connectivity is achieved between injection and production wells by hydraulic pressurization and fracturing snap shot of microseismic events during hydraulic fracturing at Soultz from Roy Baria

R&D focused on developing technology to create reservoirs that emulate high-grade, hydrothermal systems 30+ years of field testing at Fenton Hill, Los Alamos US project Rosemanowes, Cornwall, UK Project Hijori, et al, Japanese Project Soultz, France EU Project Cooper Basin, Australia Project, et al. ~3000 m has resulted in much progress and many lessons learned EGS Reservvoir at Soultz, France from Baria, et al. directional drilling to depths of 5+ km & 300+ o C diagnostics and models for characterizing size and thermal hydraulic behavior of EGS reservoirs hydraulically stimulate large >1km 3 regions of rock established injection/production well connectivity within a factor of 2 to 3 of commercial levels controlled/manageable water losses manageable induced seismic and subsidence effects net heat extraction achieved

Renewability of Geothermal Energy Sustainable operation of geothermal reservoirs? Renewable capacity (Axelsson et al., IGA News, 2001) Sustainable capacity (Sanyal, World Geothermal Congress, 2005) Sustainability compared to fossil fuels? 10-100 years versus 100 million years http://www.solarpowerwindenergy.org May 28, 2012 J.W. Tester, B. Anderson, K. Beckers, D.B. Fox, M.Z. Lukawski 26

Idealized single fracture model only rock conduction Θ( x, z, t) = T ( x, z, t) T T r,0 T w,0 w,0 = x + βz erf 2 αt Critical m parameter A β = m A 2k c r p, w L Carslaw, H.S. and Jaeger, J.C. (1959) Only a small fraction the reservoir s Wunder and Murphy (1978) Los Alamos Report thermal energy is extracted Production 30 years extraction m A = 8 10 6 kg 2 m s Θ(x,z,t) (-) Injection May 28, 2012 J.W. Tester, B. Anderson, K. Beckers, D.B. Fox, M.Z. Lukawski 27

Operation Strategies to Increase Sustainability Depleted Recovered Fully Charged (recharging) Depleted Fully Charged (recharging) Depleted Fully Charged (recharging) May 28, 2012 J.W. Tester, B. Anderson, K. Beckers, D.B. Fox, M.Z. Lukawski 28

Mathematical Model First Recovery Phase Show movies!! Θ(x,z,t) (-) Θ(x,z,t) (-) Animation of analytic solution (MATLAB) 150 years recovery after 30 years extraction at m = 8 10 A 6 U = 1.33 10 kg 2 m s 4 m s May 28, 2012 D. Sutter, D.B. Fox, B.J. Anderson, D.L. Koch, P. Rudolf von Rohr, J.W. Tester 29

How can geothermal become a major supplier of primary energy in the United States? Three key underlying questions Thermodynamics Does our use of primary energy today properly address its thermodynamic potential? Sustainability -- What are the requirements for a sustainable EGS reservoir -- environmental impacts and benefits, reservoir productivity, lifetime, and renewablility/recoverability? Economics - What will it take for Geothermal (both EGS and hydrothermal) to achieve its market potential as national resource for primary energy?

Economic tradeoffs for EGS depend on grade! 100 Drilling and Reservoir Stimulation Power Plant 80 % of Total Cost 60 40 20 0 High Grade Hydrothermal (<3 km) Mid-Grade EGS (3-6 km) Low Grade EGS (6-10 km) As EGS resource quality decreases, drilling and stimulation costs dominate

Drilling Costs Actual and Predicted Actual oil and gas well costs JAS database Actual geothermal well costs MIT and Sandia databases Livesay WellCost Lite model EGS well predictions +/- 25% Advanced drilling technologies cases1-3 NB normalization to 2004 $ using MIT drilling cost index

What will it take for lower grade EGS and hydrothermal to achieve its market potential as national resource for primary energy? From Blackwell and Richards (June, 2007)

A range of resource types and grades within the geothermal continuum Ithaca Three critical ingredients for successful heat mining 1. sufficient temperature at reasonable depth 2. sufficient permeability 3. sufficient hot water or steam Iceland 6

250 200 EGS electricity in a low gradient region not competitive today 6 km depth 223.4 Today's drilling technology with 20 kg/s flow rate Today's drilling technology with 80 kg/s flow rate Advanced drilling technology with 80 kg/s flow rate LEC /kwh 150 100 50 64.3 32.3 6 km depth 41.1 6 km depth 4 km depth 18.0 12.9 13.2 7.6 6.3 4.1 5.3 4.3 0 20 C/km 40 C/km 60 C/km 80 C/km Average Temperature Gradient Leads you to direct use and district heating

Direct-use geothermal is able to capitalize on low-t resource T = 110, 130, 150 C at 2.5, 3.0, 3.5 km (40 C/km) 3.4, 4.0, 4.7 km (30 C/km) Assuming $300/kW th for heat exchangers and piping Doublets (1 injector, 1 producer) 2004 US$ and 2 (2004 US$) 500 m separation 7-inch diameter Debt/equity rates 5%, 10%, 15% 20-year project life Assume 80 kg/s in producer Complete redrilling every 5-10 years Economic modeling for utilization of low-grade geothermal

Drilling costs in 2009 versus 2004

Economic Advantage of Direct-Use Geothermal 30 C/km Geothermal Gradient T = 110, 130, 150 C at 3.3, 4.0, 4.7 km Total costs include redrilling the reservoir 2004 US$ Drilling Costs/well $4.5, $6.0, $6.8 million 2x2004 US$ Drilling Costs/well $9.0, $12.0, $13.6 million 2004 Drilling Costs 2X2004 Drilling Costs Electricity Production ( /kwh) T (oc) 5% 10% 15% 150 15 24 34 130 27 45 62 5/18/2012 NYMEX $2.72/MMBtu 110 103 169 233 T (oc) 5% 10% 15% 150 21 36 50 130 39 67 93 110 147 250 347 2004 Drilling Costs 2X2004 Drilling Costs District Heating ($/MMBtu) T (oc) 5% 10% 15% 150 2.13 3.06 4.12 130 2.44 3.33 4.44 110 2.90 3.75 4.95 T (oc) 5% 10% 15% 150 3.24 4.88 6.72 130 3.53 5.26 7.21 110 3.98 5.85 7.96

Summary of major findings 1. Large, indigenous, accessible base load power resource 14,000,000 EJ of stored thermal energy accessible with today s technologies. Key point -- extractable amount of energy that could be recovered is not limited by resource size or availability 2. Fits portfolio of sustainable renewable energy options - EGS complements the existing portfolio and does not hamper the growth of solar, biomass, and wind in their most appropriate domains. 3. Scalable and environmentally friendly EGS plants have small foot prints and low emissions and manageable seismicity carbon free and their modularity makes them easily scalable from large size plants. 4. Technically feasible -- Major elements of the technology to capture and extract EGS are in place. Key remaining issue is to establish inter-well connectivity at commercial production rates only a factor of 2 to 3 greater than current levels. 5. Economic projections favorable for high grade areas now with a credible learning path to provide competitive energy from mid- and low-grade resources 6. Demonstration costs modest -- an investment of 700 million (2012$) over 10 years would demonstrate EGS technology at a commercial scale at several US field sites to reduce risks for private investment and enable the development of 100,000 MWe. 7. Supporting research costs reasonable about $50 million/yr (2012$) needed for!0 years --low in comparison to what other large impact US alternative energy programs will need to have the same impact on supply.

Recommended path for enabling 100,000 MW from EGS by 2050 in the U.S. Invest a total of about $1200 million for demonstration and deployment assistance and for research and development over 10 years For large scale geothermal deployment Support site specific resource assessment Support 4 to 5 field EGS demonstrations at commercial-scale production rates in different geologic settings over a range of EGS grades Maintain vigorous R&D effort on subsurface science and geo-engineering, drilling, reservoir stimulation, energy conversion, and systems analysis for EGS Less than the price of one clean coal plant!

Thank you Questions?