Geothermal Energy, Tapping the Earth’s Internal Heat

Kalyn SmithEmily Hoffman

2nd period

Goals of Geothermal Energy

• Heat and cool buildings• Produce electricity• Help mitigate global warming if widely

deployed in place of fossil fuels

A geothermal energy planthttp://www.treehugger.com/geothermal-power-plant-i01.jpg

Potential to the World

• Very high efficiency

• Moderate net energy at accessible sites

• Lower CO2 emissions than fossil fuels

http://www.treehugger.com/files/2008/06/geothermal-energy-doe-90-million-investment.php

Potential to the World

• Low cost at favorable sites

• Low land use and disturbance

• Moderate environmental impact

http://www.wateryear2003.org/en/ev.php-URL_ID=4930&URL_DO=DO_TOPIC&URL_SECTION=201.html

How is Geothermal Energy Generated?

• Temperatures hotter than the sun’s surface are continuously produced inside the earth by a slow decay of radioactive particles

• People around the world use geothermal energy to produce electricity and heat their homes by digging deep wells and pumping the heated water or steam to the surface

Where is geothermal energy found?

• Geothermal reservoirs• Volcanoes• Fumaroles• Hot springs• Geysers

http://www.terrapass.com/images/blogposts/volcano.jpg

Most geothermal energy…

• Is found along major plate boundaries where earthquakes and volcanoes are concentrated

• The Ring of Fire• The most common method that scientists use

to find geothermal reservoirs is drilling a well and testing the temperature deep underground.

The Ring of Fire

http://upload.wikimedia.org/wikipedia/commons/0/09/Pacific_Ring_of_Fire.png

The United States and Geothermal Energy

• Most of the geothermal reservoirs in the U.S. are located in the western states and Hawaii.

• California generates the most electricity from geothermal energy.• "The Geysers" dry steam reservoir in northern California is the

largest known dry steam field in the world and has been producing electricity since 1960.

• The U.S. leads the world in electricity generation with geothermal power.

• 7 states have geothermal power plants• In 2008 U.S. geothermal power plants produced 0.4% of total

electricity in the United States.

Geothermal energy in the U.S.

Uses of Geothermal Energy

• Direct use and district heating systems

• Electricity generation power plant – Require water or steam at very high temperatures

(300 F – 700 F)• Geothermal heat pumps– use stable ground or water temperatures near the

Earth's surface to control building temperatures above ground.

Direct use of geothermal energy

• Use hot water from springs/reservoirs near the surface

• District heating systems are a common way to heat buildings using geothermal energy, which is accomplished by piping hot water near the earth’s surface directly into buildings for heat

• Industrial applications of geothermal energy include food dehydration, gold mining, and milk pasteurizing

Geothermal power plants• Use hydrothermal resources that have two common

ingredients: water and heat. • Require high temperatures (300 F – 700 F) hydrothermal

resources that may either come from dry steam wells or hot water wells

• These resources can be used by drilling deep wells and pumping the steam or hot water to the surface

• The wells are 1 – 2 miles deep• There are three types of geothermal power plants: dry

steam plants, flash steam plants, and binary cycle power plants

Dry steam plants

• Use steam piped directly from a geothermal reservoir to turn the generator turbines

http://www1.eere.energy.gov/geothermal/images/drysteam.gif

Flash Steam Plants

• Takes high pressure hot water from deep inside the earth and converts it to steam to drive the generator turbines

• When the steam cools it condenses into water and is injected into the earth to be used over and over again.

• Most geothermal plants are flash steam plants

http://www.alchemydes.com/samples/flashsteam_chart.gif

Binary cycle power plants

• Transfers the heat from geothermal hot water to another liquid.

• The heat causes the second liquid to turn to steam which is used to drive a generator turbine.

http://www.digtheheat.com/geothermalpics/binary_plant.gif

Energy efficient and cost effective• According to the

EPA are the most energy efficient, cost effective, and environmentally clean systems for temperature control

http://homeimprovement.resourcesforattorneys.com/images/geothermal_heat_pumps.jpg

Geothermal energy and the environment

• Geothermal power plants do not burn fuel to generate electricity so their emission levels are very low

• Release less that 1% of carbon dioxide emissions of a fossil fuel plant

• Use scrubber systems to clean the air of hydrogen sulfide

• Emits 97% less acid rain-causing sulfur compounds than fossil fuel plants

Geothermal energy plant piping

http://www.teara.govt.nz/files/p5432chh.jpg

Disadvantages

• Hard to find a suitable location due to the large area that the geothermal piping consumes

• It is possible for an extraction site to suddenly stop producing steam

• Harmful gases can escape from deep within the earth

• The initial cost and design is costly

BIBLIOGRAPHY

• http://tonto.eia.doe.gov/kids/energy.cfm?page=geothermal_home-basics-k.cfm

• http://www.energyquest.ca.gov/story/chapter11.html

• http://www.energy-consumers-edge.com/pros_and_cons_of_geothermal_energy.html