Geothermal Energy

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Geothermal Energy

• Production, Problems, and Possibilities
• Jessica Lindberg Kozarek
• April 23, 2001

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Geothermal EnergyA Renewable Resource.


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Sources of Geothermal Electricity
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Availability of Geothermal Energy
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Geothermal Power Plant
Dry Steam Units 5 and 6 at The Geysers, California
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Three Types Geothermal Power Plants in Use.

• Dry Steam Power Plant
• Flash Steam Power Plant
• Binary Cycle Power Plant

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Dry Steam Power Plant

• Oldest, first built in Lardello, Italy in 1904.
• Uses steam reservoirs (High T)
• Emits only steam and trace gases.

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Flash Steam Power Plant

• Originated in New Zealand.
• T gt 400 oF.
• Uses High Temperature and Pressure Water
  Reservoirs.
• Emits only steam and trace gases.

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Binary Cycle Power Plant

• T lt 400 oF
• Closed Loop
• Almost no emissions.

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Production

• Cost is upfront
• 2000 per installed kWh
• Well Drilling and Pipeline Construction
• Resource analysis of drilling information
• Power plant design
• Operating Costs
• 0.015-0.045 per kWh
• Availability of 90 of the time increases cost.

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Problems

• Fluid rock chemistry and reservoir
  characteristics difficult to simulate.
• Acid content in water.
• Dissolved salts and gases modify properties of
  steam.
• In water-dominated systems, steam must be
  separated to produce electricity.
• Cold injection water can produce major problems
  if it reaches production well.

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Problems, cont.

•  Increased seismic activity with exploitation of
  geothermal reservoirs.
•  Cheap oil and natural gas prices.
•  Resource depletion.
•  Damage and changes to natural tourist
  attractions.
• High cost of drilling.

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Geothermal vs. Fossil Fuels

• Less Emissions
• Less Area
• More Availability (time)
• Less Transportation
• Less Availability (geographic)

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Geothermal Emissions

• Geothermal Plants Emit
• 70 less SOx
• 33 less NOx
• 20 of greenhouse gases

• This prevents the emission of
• 22 million tons CO2 per year
• 200,000 tons SO2 per year
• 110,000 tons PM per year

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Area

• Advanced directional or slant drilling minimizes
  impact on land.
• Several wells can be drilled from one pad.
• Typically 400m2 per gigawatt over 30 yrs.
• 1-8 acres/MW for geothermal vs. 5-10 acres/MW for
  nuclear and 19 acres/MW for coal.

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Availability

• Geothermal plants 95
• Coal plants 60-70
• This results in a higher cost
• but enables the plant to charge
• more during peak times.

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Possibilities

• Recovery and Recycling of byproducts.
• Biological Treatment for disposal of Geothermal
  Sludge.
• Wastewater recycling.
• Chemical Tracers for reservoir understanding.
• Use of hot dry rock for electricity generation.
• Use of deeper wells and magma for electricity
  generation.

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Recovery and Recycling

• H2S is separated and used for sulfuric acid
  production.
• Metals such as zinc are recovered and sold for
  profit.
• Silica from microbial processes can be recycled
  as concrete filler.

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Biological Treatment of Geothermal Sludge

• Biological treatment can be used for
• Solubilization and removal of of many metals
  including radionuclides.
• Selective removal of a few metals.
• Concentration of metals.
• Recovery of metals.
• Recovery of Salts.
• Water can be used for reinjection/irrigation.

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Wastewater RecyclingSanta Rosa California
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Chemical Tracers

• Provide an insight into the pathways that
  reinjected fluid will take in the geothermal
  reservoir.
• Must be stable enough to endure weeks to years of
  geothermal testing.
• Are usually non-toxic, and non-radioactive to
  avoid groundwater contamination.

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Hot Dry Rock and Magma

• These resources are being examined in other
  countries.
• Hot Dry Rock has actually been used to produce
  electricity, but the technology is limited.
• Drilling techniques are not yet advanced enough
  to utilize magma energy.

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Future for Geothermal Energy

• Clean power for developing countries.
• More geothermal power production in the western
  U.S.
• through programs such as Geopowering the West.
• Even cleaner production through better technology
  
• and understanding of geothermal reservoirs,
  recycling,
• and reinjection.