Geothermal Energy: Harnessing the Heat Beneath Your Feet

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Geothermal EnergyHarnessing the Heat
BeneathYour Feet
Carol J. Bruton John Ziagos Lawrence Livermore
National Laboratory Ken Wedel Tracy Independent
School District Science on Saturday Feb. 9,
2008
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What You Will Learn

• What is geothermal energy?
• Where does it come from?
• How is it used today?
• Geothermal energy in the U.S. and California
• Environmental benefits
• The future of geothermal energy

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Clues! Volcanoes, geysers, hot springs
Kilauea, Hawaii
Mount St Helens
Credit Joel Renner, DOE, Office of Geothermal
Technologies
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What is geothermal energys source?

• Radioactive decaygenerates heat
• uranium (238U, 235U)
• thorium (232Th)
• potassium (40K)

• Heat of formation
• Extraterrestrialimpacts
• Gravitational contraction

Geothermal Education Office, Tiburon, CA
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Natural radioactivity
Demonstration No. 1
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Geothermal Education Office, Tiburon, CA
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Temperatures at depth reflect the geothermal
resource
3.5 km/2.2 mi
6.5 km/4 mi
10 km/6.2 mi
Source MIT, The Future of Geothermal Energy, 2006
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The Earths surface is made of tectonic plates
that move
Ring of Fire
Geothermal Education Office, Tiburon, CA
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Hottest known geothermal regions are located at
plate boundaries
Geothermal energy utilization world-wide9100
MW, 25 countries, 60 million people
Geothermal Education Office, Tiburon, CA
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Subduction and spreading bring heat to the
surface
Spreading Center
Continental Plate
Plate
Oceanic
Subducting
Convection
Geothermal Education Office, Tiburon, CA
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Demonstration No. 2
Convection
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Convection and conduction distribute Earths heat
in the crust
Source Dickson and Fanelli, International
Geothermal Association
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Required components of a geothermal reservoir
Geothermal Reservoir
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Demonstration No. 3
Geothermal reservoir
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The ideal geothermal reservoir
Geothermal Education Office, Tiburon, CA
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We access high temperatures and permeable
fractures by drilling
Geothermal Education Office, Tiburon, CA
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Flash steam power plant
Steam
Turbine
Generator
Flash Tank
Electricity
Condensed Steam (Water)
Separated Water
Hot Water
Geothermal Education Office, Tiburon, CA
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Geothermal turbines convert thermal to
electrical energy
Turbine converts heat into mechanical (rotation)
energy
Generator converts mechanical energy (rotation)
into electricity
Geothermal Education Office, Tiburon, CA
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Demonstration No. 4
Conversion ofthermal to electrical energy
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Binary cycle power plant
Geothermal Education Office, Tiburon, CA
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Demonstration No. 5
Heat exchanger
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The challenge Finding the hidden resource
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Using satellites to examinethe Earths surface

• Surface deformation may result from subsurface
  stresses which create fractures
• InSAR (synthetic aperture radar interferometry)
  detects surface deformation

Bill Foxall, PI
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Demonstration No. 6
Stress creates fractures
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Engineering a geothermal reservoir
Enhanced Geothermal Systems
Permeability
Water
Geothermal Reservoir
Mining thermal energy from hot, dry rock
Source Duffield and Sass, 2004
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Fluid flow changes fracture permeability
Jeff Roberts, PI
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U.S. geothermal resource baseEnough for over
100,000 years

• We now use
• 2800 MWe electric
• 3700 MWt thermal

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Direct use of geothermal heat

• Displaces about 1.6M barrels of oil annually in
  the U.S.
• Agriculture
• Aquaculture
• Balneology (hot springs, bathing)
• District heating

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Geothermal heat pumps are used for heating and
cooling all over the U.S.

• One typical homesheat pump systemis equal in
  greenhousegas reduction to
• Taking two cars off the road
• Planting an acre of trees

Dept. of Energy
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U.S consumes more geothermal energy than wind and
solar energy
Data source EIA
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California dominates geothermal energy
utilization in the U.S.

• Geothermal energy supplies 5 of Californias
  electricity
• Lots more potential!

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Demonstration No. 7
Geothermal Education Office, Tiburon, CA
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Environmental benefits of displacing fossil fuels
Geothermal Education Office, Tiburon, CA
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Geothermal energy Clean, green and renewable

• Steam, not smoke!

• 90-95 fewer greenhouse gas emissions than coal

Geothermal Education Office, Tiburon, CA
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THE END
Thank You!