Geothermal Energy
Production, Problems, and
Possibilities
Jessica Lindberg Kozarek
April 23, 2001
Geothermal Energy
A “Renewable” Resource.
Sources of Geothermal
Electricity
Availability of Geothermal
Energy
Geothermal Power Plant
Dry Steam
Units 5 and 6 at The Geysers, California
Three Types Geothermal
Power Plants in Use.

Dry Steam Power Plant

Flash Steam Power Plant

Binary Cycle Power Plant
Dry Steam Power Plant
Oldest,
first built in
Lardello, Italy in 1904.
Uses
steam reservoirs
(High T)
Emits
only steam and
trace gases.
Flash Steam Power Plant
Originated
Zealand.
T
in New
> 400 oF.
Uses
High Temperature
and Pressure Water
Reservoirs.
Emits
only steam and
trace gases.
Binary Cycle Power Plant
T
< 400 oF
Closed
Loop
Almost
no emissions.
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.
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.
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.
Geothermal vs. Fossil Fuels
Less Emissions
 Less Area
 More Availability (time)
 Less Transportation
 Less Availability (geographic)

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
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.

Availability
 Geothermal plants ~ 95%+
 Coal plants ~ 60-70+%
This results in a higher cost
but enables the plant to charge
more during peak times.
Possibilities




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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.
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.

Biological Treatment of
Geothermal Sludge

Biological treatment can be used for:





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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.
Wastewater Recycling
Santa Rosa California
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 nonradioactive to avoid groundwater
contamination.

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.

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.