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A Brief Introduction to Geothermal Energy and its

Utilization for Electric Power Generation

G. W. HuttrerOAS Consultant

Michela MilettoOAS Staff

Thermal means

GEO =

THERMAL =

The Earth

Crust

M Mantle

Outer Core

Inner Core

Temperatures in the Earth

2,000

4,000

6,000

4,000 C

6,000 C

Temperaturesin degrees C

Depth inKilometers

Plate Boundaries

“Ring of Fire”

Plate Tectonic Processes

Spreading Center

Oceanic Plate Subducting

Convection

Continental Plate

ConvectionCells

Rising MagmaSpreading Center

Volcanoes (as in the Caribbean)

Mt. KilueaHawaii

Magma

PermeableReservoirRocks

Geothermal Exploration Surveys

• Satellite imagery and aerial photography

• Volcanological studies

• Geologic and structural mapping

• Geochemical surveys

• Geophysical surveys

• Temperature gradient hole drilling

Geochemistry

GeophysicsGeology

Thermal Gradient Measuring

Thermal Gradient Drill

Sample Temperature Gradient Data

500

1000

1500

2000

3000

Depth/Ft

Bottom holetemperature265˚C (509˚F)

50 100 150 200 250

500

1000

1500

2000

2500

3000

Depth (Feet)

Temp. (C)

Deep Well Drill

Well Test in Progress

ProductionWell

InjectionWell

Flash Tanks

Turbine-GeneratorPower Plant &Cooling Towers

Dry Steam Power PlantTurbine Generator

SteamCondensedSteam(Water)

Electricity

Flash Steam Power Plant

Separated Water

Steam

CondensedSteam(Water)

HotWater

Turbine Generator

FlashTank Electricity

Binary Cycle Power PlantBinary Vapor Generator

Electricity

Binary Liquid

Heat Exchanger

CooledWater

HotWater

ProductionWell

InjectionWell

Heat Exchanger

Turbine Generator

CO2 Emissions Comparison(lbs/MW-hr)

Source EIA 1998; Bloomfield and Moore 1999

Geothermal

NaturalGas

Oil

Coal2000

0

1500

1000

500

Benefits of Geothermal Power• Provides clean and safe energy using little land

• Is renewable and sustainable

• Generates continuous, reliable “baseload” power

• Conserves fossil fuels and contributes to diversity in energy sources

• Avoids importing and benefits local economies

• Offers modular, incremental development andvillage power to remote sites