Chuck Kutscher

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Geothermal Power Potential
Energy and Climate Mini-Workshop November 3, 2008

• Chuck Kutscher
• National Renewable Energy Laboratory

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Geothermal in the Energy Portfolio Net
Generation 2006
Source EIA Annual Energy Review 2007
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U.S. Renewable Energy Electric Capacity
Sources Chalk, AWEA, IEA, NREL, EIA, GEA
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Geothermal Resources
Volcanic
Hydrothermal
Magma
Geopressured
Hot water
Wells
Enhanced Geothermal System
Hot granite
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Carbon Benefits
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Advantages of Geothermal Energy

• Environmentally sound
• Resources last the life of the plant
• High plant availability (over 95)
• Provides steady base load power
• Relatively low cost (5 to 8 cents per kWh)

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Todays Status

• 8,000 MW generated in 21 countries
• In U.S. 3,000 MWe installed, 4,000 MWe under
  development
• DOE funding 21 companies 43 million over 4 years
  for EGS projects
• Cost 5-8/kWh with no PTC
• Capacity factor typically gt 90, base load power

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Hydrothermal Resource
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Geothermal Power Plants
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Plant Type vs. Temperature
Flash steam
175oC (350oF)
Binary cycle
90oC (195oF)
0oC 32oF)
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Plant Costs
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Favorable Geothermal Areasand Known Systems
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Geographic Distribution of Hydrothermal Resources
Identified Geothermal Resources
Undiscovered Resources
USGS, 2008
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U.S. Hydrothermal Electric Power Potential
Williams, et al., USGS Fact Sheet, Assessment of
Moderate- and High-Temperature Geothermal
Resources of the United States, September 2008
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Geothermal Domains
Hydrothermal
Fluid Content
Permeability
Water Injection Required
Fracturing Required
Note System must have fluid content,
permeability, and heat to be potentially viable.
This combination can be natural (Hydrothermal) or
created in an enhanced geothermal system.
Enhanced Geothermal System
Hot Dry Rock (HDR) Fracturing and water
injection required
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Geographic Distribution of EGS
USGS, 2008
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EGS ResourceTemperatures at 6 km Depth
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EGS Steps
Source NREL
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The U.S. Enhanced Geothermal System Resource
Source MIT Study- The Future of Geothermal
Energy
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MIT EGS Supply Curve 10 of U.S. Capacity by
Mid-Century
MIT EGS model predictions with todays drilling
and plant costs and mature reservoir technology
at 80 kg/s per production well
2004 US
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EGS Challenges
Geologic variability and uncertainty make the
technical challenges of EGS very different from
other renewable energy sources.

• Technical
• Site selection - regional exploration techniques
  for EGS
• Creating EGS under various geologic environments
• achieving low flow impedance
• achieving sufficiently large sustainable
  reservoir without short circuiting (80 kg/s at
  200C)
• minimizing water loss
• microseismicity
• Few EGS field experiments yet conducted
  worldwide only 25 kg/s achieved at Soultz

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EGS Challenges

• Economic
• Exploration cost and risk
• Drilling, completion and reservoir stimulation
  costs
• Capital cost of surface facilities
• No commercial EGS site for benchmarking
• Commercialization
• Validating EGS technology requires high risk
  field experiments in a variety of geologic
  settings
• Limited Federal RD funding

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U.S. EGS Electric Power Potential
Williams, et al., USGS Fact Sheet, Assessment of
Moderate- and High-Temperature Geothermal
Resources of the United States, September 2008
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ASES Study Supply Curve
Hydrothermal 27 GW Sedimentary EGS 25
GW Co-produced fluids 44 GW Basement EGS 4
GW
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Geothermal Power Savings

• 50,000 MW by 2030
• 25 existing resources, 25 expanded, 50 from
  oil gas wells
• 5 to 10 /kWh

Carbon Savings 83 MtC/yr