Geo Thermal Power:
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Alternative Energy
WHAT IS GEOTHERMAL ENERGY?
The word geothermal comes from the Greek words geo (earth) and therme (heat). So,
geothermal energy is heat from within the earth. We can use the steam and hot water
produced inside the earth to heat buildings or generate electricity. Geothermal energy is a
renewable energy source because the water is replenished by rainfall and the heat is
continuously produced inside the earth.
ENERGY INSIDE THE EARTH
Geothermal energy is generated in the earth's core, about 4,000 miles below the surface.
Temperatures hotter than the sun's surface are continuously produced inside the earth by
the slow decay of radioactive particles, a process that happens in all rocks. The earth has
a number of different layers:
The core itself has two layers: a solid iron core and an outer core made of very hot melted
rock, called magma.
The mantle which surrounds the core and is about 1,800 miles thick. It is made up of
magma and rock.
The crust is the outermost layer of the earth, the land that forms the continents and ocean
floors. It can be three to five miles thick under the oceans and 15 to 35 miles thick on the
continents.
The earth's crust is broken into pieces called plates. Magma comes close to the earth's
surface near the edges of these plates. This is where volcanoes occur. The lava that
erupts from volcanoes is partly magma. Deep underground, the rocks and water absorb
the heat from this magma. The temperature of the rocks and water get hotter and hotter as
you go deeper underground.
People around the world use geothermal energy to heat their homes and to produce
electricity by digging deep wells and pumping the heated underground water or steam to
the surface. Or, we can make use of the stable temperatures near the surface of the earth
to heat and cool buildings. (See Uses of Geothermal Energy below.)
WHERE IS GEOTHERMAL ENERGY FOUND ?
Most geothermal reservoirs are deep underground with no visible clues showing above
ground.
Geothermal energy can sometimes find its way to the surface in the form of:
volcanoes and fumaroles (holes where volcanic gases are released)
hot springs and
geysers.
The most active geothermal resources are usually found along major plate boundaries
where earthquakes and volcanoes are concentrated. Most of the geothermal activity in the
world occurs in an area called the Ring of Fire. This area rims the Pacific Ocean.
When magma comes close to the surface it heats ground water found trapped in porous
rock or water running along fractured rock surfaces and faults. Such hydrothermal
resources have two common ingredients: water (hydro) and heat (thermal). Naturally
occurring large areas of hydrothermal resources are called geothermal reservoirs.
Geologists use different methods to look for geothermal reservoirs. Drilling a well and
testing the temperature deep underground is the only way to be sure a geothermal
reservoir really exists.
Most of the geothermal reservoirs in the United States are located in the western states,
Alaska, and Hawaii. California is the state that 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. The field has been producing electricity since 1960.
USES OF GEOTHERMAL ENERGY
Some applications of geothermal energy use the earth's temperatures near the surface,
while others require drilling miles into the earth. The three main uses of geothermal energy
are:
1) Direct Use and District Heating Systems which use hot water from springs or reservoirs
near the surface.
2) Electricity generation in a power plant requires water or steam at very high temperature
(300 to 700 degrees Fahrenheit). Geothermal power plants are generally built where
geothermal reservoirs are located within a mile or two of the surface.
3) 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
The direct use of hot water as an energy source has been happening since ancient times.
The Romans, Chinese, and Native Americans used hot mineral springs for bathing,
cooking and heating. Today, many hot springs are still used for bathing, and many people
believe the hot, mineral-rich waters have natural healing powers.
After bathing, the most common direct use of geothermal energy is for heating buildings
through district heating systems. Hot water near the earth's surface can be piped directly
into buildings and industries for heat. A district heating system provides heat for 95
percent of the buildings in Reykjavik, Iceland. Examples of other direct uses include:
growing crops, and drying lumber, fruits, and vegetables.
GEOTHERMAL POWER PLANTS
Geothermal power plants use hydrothermal resources which have two common
ingredients: water (hydro) and heat (thermal). Geothermal plants require high temperature
(300 to 700 degrees Fahrenheit) hydrothermal resources that may come from either dry
steam wells or hot water wells. We can use these resources by drilling wells into the earth
and piping the steam or hot water to the surface. Geothermal wells are one to two miles
deep.
The United States generates more geothermal electricity than any other country but the
amount of electricity it produces is less than 1 percent of electricity produced in United
States. Only four states have geothermal power plants:
California - has 33 geothermal power plants that produce almost 90 percent of the nation's
geothermal electricity.
Nevada - has 15 geothermal power plants.
Hawaii and Utah - each have one geothermal plant
There are three basic types of geothermal power plants:
Dry steam plants - use steam piped directly from a geothermal reservoir to turn the
generator turbines. The first geothermal power plant was built in 1904 in Tuscany, Italy at a
place where natural steam was erupting from the earth.
Flash steam plants - take high-pressure hot water from deep inside the earth and convert
it to steam to drive the generator turbines. When the steam cools, it condenses to water
and is injected back into the ground to be used over and over again. Most geothermal
power plants are flash plants.
Binary power plants - transfer 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.
GEOTHERMAL HEAT PUMPS
While temperatures above ground change a lot from day to day and season to season,
temperatures in the upper 10 feet of the Earth's surface hold nearly constant between 50
and 60 degrees Fahrenheit. For most areas, this means that soil temperatures are usually
warmer than the air in winter and cooler than the air in summer. Geothermal heat pumps
use the Earth's constant temperatures to heat and cool buildings. They transfer heat from
the ground (or water) into buildings in winter and reverse the process in the summer.
According to the U.S. Environmental Protection Agency (EPA), geothermal heat pumps are
the most energy-efficient, environmentally clean, and cost-effective systems for
temperature control. Although, most homes still use traditional furnaces and air
conditioners, geothermal heat pumps are becoming more popular. In recent years, the U.S.
Department of Energy along with the EPA have partnered with industry to promote the use
of geothermal heat pumps.
GEOTHERMAL ENERGY AND THE ENVIRONMENT
The environmental impact of geothermal energy depends on how it is being used.
Direct use and heating applications have almost no negative impact on the environment.
Geothermal power plants do not burn fuel to generate electricity, so their emission levels
are very low. They release about 1 to 3 percent of the carbon dioxide emissions of a fossil
fuel plant. Geothermal plants use scrubber systems to clean the air of hydrogen sulfide
that is naturally found in the steam and hot water. Geothermal plants emit 97 percent less
acid rain - causing sulfur compounds than are emitted by fossil fuel plants. After the steam
and water from a geothermal reservoir have been used, they are injected back into the
earth.
Geothermal features in national parks, such as geysers and fumaroles in Yellowstone
National Park, are protected by law, to prevent the land from being disturbed.
Last Revised: July 2007
Sources: Adapted from the National Energy Education Development Project, Intermediate
Energy Infobook, 2006.
Energy Information Administration, Electric Power Annual 2005.
Office of Geothermal Technologies, U.S. Department of Energy, "Geothermal Heat Pumps
Make Sense for Homeowners," DOE/GO-10098-651, April 1999.
The word geothermal comes from the Greek words geo (earth) and therme (heat). So,
geothermal energy is heat from within the earth. We can use the steam and hot water
produced inside the earth to heat buildings or generate electricity. Geothermal energy is a
renewable energy source because the water is replenished by rainfall and the heat is
continuously produced inside the earth.
ENERGY INSIDE THE EARTH
Geothermal energy is generated in the earth's core, about 4,000 miles below the surface.
Temperatures hotter than the sun's surface are continuously produced inside the earth by
the slow decay of radioactive particles, a process that happens in all rocks. The earth has
a number of different layers:
The core itself has two layers: a solid iron core and an outer core made of very hot melted
rock, called magma.
The mantle which surrounds the core and is about 1,800 miles thick. It is made up of
magma and rock.
The crust is the outermost layer of the earth, the land that forms the continents and ocean
floors. It can be three to five miles thick under the oceans and 15 to 35 miles thick on the
continents.
The earth's crust is broken into pieces called plates. Magma comes close to the earth's
surface near the edges of these plates. This is where volcanoes occur. The lava that
erupts from volcanoes is partly magma. Deep underground, the rocks and water absorb
the heat from this magma. The temperature of the rocks and water get hotter and hotter as
you go deeper underground.
People around the world use geothermal energy to heat their homes and to produce
electricity by digging deep wells and pumping the heated underground water or steam to
the surface. Or, we can make use of the stable temperatures near the surface of the earth
to heat and cool buildings. (See Uses of Geothermal Energy below.)
WHERE IS GEOTHERMAL ENERGY FOUND ?
Most geothermal reservoirs are deep underground with no visible clues showing above
ground.
Geothermal energy can sometimes find its way to the surface in the form of:
volcanoes and fumaroles (holes where volcanic gases are released)
hot springs and
geysers.
The most active geothermal resources are usually found along major plate boundaries
where earthquakes and volcanoes are concentrated. Most of the geothermal activity in the
world occurs in an area called the Ring of Fire. This area rims the Pacific Ocean.
When magma comes close to the surface it heats ground water found trapped in porous
rock or water running along fractured rock surfaces and faults. Such hydrothermal
resources have two common ingredients: water (hydro) and heat (thermal). Naturally
occurring large areas of hydrothermal resources are called geothermal reservoirs.
Geologists use different methods to look for geothermal reservoirs. Drilling a well and
testing the temperature deep underground is the only way to be sure a geothermal
reservoir really exists.
Most of the geothermal reservoirs in the United States are located in the western states,
Alaska, and Hawaii. California is the state that 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. The field has been producing electricity since 1960.
USES OF GEOTHERMAL ENERGY
Some applications of geothermal energy use the earth's temperatures near the surface,
while others require drilling miles into the earth. The three main uses of geothermal energy
are:
1) Direct Use and District Heating Systems which use hot water from springs or reservoirs
near the surface.
2) Electricity generation in a power plant requires water or steam at very high temperature
(300 to 700 degrees Fahrenheit). Geothermal power plants are generally built where
geothermal reservoirs are located within a mile or two of the surface.
3) 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
The direct use of hot water as an energy source has been happening since ancient times.
The Romans, Chinese, and Native Americans used hot mineral springs for bathing,
cooking and heating. Today, many hot springs are still used for bathing, and many people
believe the hot, mineral-rich waters have natural healing powers.
After bathing, the most common direct use of geothermal energy is for heating buildings
through district heating systems. Hot water near the earth's surface can be piped directly
into buildings and industries for heat. A district heating system provides heat for 95
percent of the buildings in Reykjavik, Iceland. Examples of other direct uses include:
growing crops, and drying lumber, fruits, and vegetables.
GEOTHERMAL POWER PLANTS
Geothermal power plants use hydrothermal resources which have two common
ingredients: water (hydro) and heat (thermal). Geothermal plants require high temperature
(300 to 700 degrees Fahrenheit) hydrothermal resources that may come from either dry
steam wells or hot water wells. We can use these resources by drilling wells into the earth
and piping the steam or hot water to the surface. Geothermal wells are one to two miles
deep.
The United States generates more geothermal electricity than any other country but the
amount of electricity it produces is less than 1 percent of electricity produced in United
States. Only four states have geothermal power plants:
California - has 33 geothermal power plants that produce almost 90 percent of the nation's
geothermal electricity.
Nevada - has 15 geothermal power plants.
Hawaii and Utah - each have one geothermal plant
There are three basic types of geothermal power plants:
Dry steam plants - use steam piped directly from a geothermal reservoir to turn the
generator turbines. The first geothermal power plant was built in 1904 in Tuscany, Italy at a
place where natural steam was erupting from the earth.
Flash steam plants - take high-pressure hot water from deep inside the earth and convert
it to steam to drive the generator turbines. When the steam cools, it condenses to water
and is injected back into the ground to be used over and over again. Most geothermal
power plants are flash plants.
Binary power plants - transfer 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.
GEOTHERMAL HEAT PUMPS
While temperatures above ground change a lot from day to day and season to season,
temperatures in the upper 10 feet of the Earth's surface hold nearly constant between 50
and 60 degrees Fahrenheit. For most areas, this means that soil temperatures are usually
warmer than the air in winter and cooler than the air in summer. Geothermal heat pumps
use the Earth's constant temperatures to heat and cool buildings. They transfer heat from
the ground (or water) into buildings in winter and reverse the process in the summer.
According to the U.S. Environmental Protection Agency (EPA), geothermal heat pumps are
the most energy-efficient, environmentally clean, and cost-effective systems for
temperature control. Although, most homes still use traditional furnaces and air
conditioners, geothermal heat pumps are becoming more popular. In recent years, the U.S.
Department of Energy along with the EPA have partnered with industry to promote the use
of geothermal heat pumps.
GEOTHERMAL ENERGY AND THE ENVIRONMENT
The environmental impact of geothermal energy depends on how it is being used.
Direct use and heating applications have almost no negative impact on the environment.
Geothermal power plants do not burn fuel to generate electricity, so their emission levels
are very low. They release about 1 to 3 percent of the carbon dioxide emissions of a fossil
fuel plant. Geothermal plants use scrubber systems to clean the air of hydrogen sulfide
that is naturally found in the steam and hot water. Geothermal plants emit 97 percent less
acid rain - causing sulfur compounds than are emitted by fossil fuel plants. After the steam
and water from a geothermal reservoir have been used, they are injected back into the
earth.
Geothermal features in national parks, such as geysers and fumaroles in Yellowstone
National Park, are protected by law, to prevent the land from being disturbed.
Last Revised: July 2007
Sources: Adapted from the National Energy Education Development Project, Intermediate
Energy Infobook, 2006.
Energy Information Administration, Electric Power Annual 2005.
Office of Geothermal Technologies, U.S. Department of Energy, "Geothermal Heat Pumps
Make Sense for Homeowners," DOE/GO-10098-651, April 1999.
The Earth is a Giant Power Plant
Nevada Geothermal Power
Inc.: GeothermEx Report
Supports Increased
Mega-Watt Capacity for the
Initial Blue Mountain
Geothermal Power Plant
Inc.: GeothermEx Report
Supports Increased
Mega-Watt Capacity for the
Initial Blue Mountain
Geothermal Power Plant
Geothermal in the News
Copyright 2008 Harold R Muxlow
Myths and Facts about Geothermal
Myth: Geothermal energy is still new and experimental.
Fact: Geothermal energy has been used to generate electricity since 1904. Today, the
US has nearly 2,800 MW of geothermal electricity connected to the grid that generates a
yearly average of 15 billion kilowatt hours of power. That’s comparable to burning about
25 million barrels of oil or 6 million short tons of coal per year.
Myth: Geothermal power plants emit smoke.
Fact: The visible plumes seen rising from geothermal power plants are actually water
vapor emissions, not smoke. No combustion of fuels occurs to produce electricity at a
geothermal facility.
Myth: Extraction and injection of geothermal brines contaminates drinking water.
Fact: No contamination of groundwater has ever occurred as a result of geothermal
activity.
Myth: Geothermal energy is still new and experimental.
Fact: Geothermal energy has been used to generate electricity since 1904. Today, the
US has nearly 2,800 MW of geothermal electricity connected to the grid that generates a
yearly average of 15 billion kilowatt hours of power. That’s comparable to burning about
25 million barrels of oil or 6 million short tons of coal per year.
Myth: Geothermal power plants emit smoke.
Fact: The visible plumes seen rising from geothermal power plants are actually water
vapor emissions, not smoke. No combustion of fuels occurs to produce electricity at a
geothermal facility.
Myth: Extraction and injection of geothermal brines contaminates drinking water.
Fact: No contamination of groundwater has ever occurred as a result of geothermal
activity.