RMS Objective 13: Identify geothermal energy as a renewable energy source, and give examples of places where geothermal energy is being used.
Geothermal energy is the natural heat of the Earth.
Heat flows outward from Earth's interior. The crust insulates us from Earth's interior heat. The mantle is semi-molten, the outer core is liquid and the inner core is solid.
The deeper you go, the hotter it gets (in Fahrenheit and miles).
Earth's crust is broken into huge plates that move apart or push together at about the rate our fingernails grow. Convection of semi-molten rock in the upper mantle helps drive plate tectonics.
New crust forms along mid-ocean spreading centers and continental rift zones. When plates meet, one can slide beneath another. Plumes of magma rise from the edges of sinking plates.
Thinned or fractured crust allows magma to rise to the surface as lava. Most magma doesn't reach the surface but heats large regions of underground rock.
Rainwater can seep down faults and fractured rocks for miles. After being heated, it can return to the surface as steam or hot water.
This steaming ground is in the Philippines.
When hot water and steam reach the surface, they can form fumaroles, hot springs, mud pots and other interesting phenomena.
When the rising hot water and steam is trapped in permeable and porous rocks under a layer of impermeable rock, it can form a geothermal reservoir.
A geothermal reservoir is a powerful source of energy!
Many areas have accessible geothermal resources, especially countries along the circum-Pacific "Ring of Fire," spreading centers, continental rift zones and other hot spots.
These and other methods are used.
Exploration commonly begins with analysis of satellite images and aerial photographs.
Volcanoes are obvious indications of underground heat, this volcano, Mt. Mayon in the Albay province of the Philippines erupted in 1999.
Geologists explore volcanic regions to find the most likely areas for further study, like this steaming hillside in Nicaragua.
Geologic landforms and fault structures are mapped in the region. �This view overlooks Basin and Range terrain East of the Sierra Nevadas.
Rocks are examined up close.
Geologic maps like this one are created, showing rock type and ages in different colors.
Data from electrical, magnetic, chemical and seismic surveys is gathered in the field.
The data obtained in the field are displayed in various ways and analyzed.
Geologists and drillers study the data to decide whether to recommend drilling. Geothermal reservoirs suitable for commercial use can only be discovered by drilling.
First, a small- diameter "temperature gradient hole" is drilled (some only 200' deep, some over 4000 feet deep) with a truck-mounted rig to determine the temperatures and underground rock types.
Production-sized wells require large drill rigs like these and can cost as much as a million dollars or more to drill. Geothermal wells can be drilled over two miles deep.
Natural steam from the production wells power the turbine generator. The steam is condensed by evaporation in the cooling tower and pumped down an injection well to sustain production.
Like all steam turbine generators, the force of steam is used to spin the turbine blades which spin the generator, producing electricity. But with geothermal energy, no fuels are burned.
Those white plumes you see at geothermal power plants are steam (water vapor). Geothermal plants do not burn fuel or produce smoke.
Geothermal power plants are clean and are operating successfully in sensitive environments.
The first modern geothermal power plants were also built in Lardello, Italy. They were destroyed in World War II and rebuilt. Today after 90 years, the Lardello field is still producing.
The first geothermal power plants in the U.S. were built in 1962 at The Geysers dry steam field, in northern California. It is still the largest producing geothermal field in the world.
This power plant provides about 25% of the electricity used on the Big Island of Hawaii.
Geothermal power has many local and global benefits.
The fastest growth in US geothermal capacity was from 1980 to 1990, following enactment of federal laws that compelled utilities to purchase electricity from independent power producers.
People who live in these areas are receiving electricity from geothermal power plants.
Producing electricity is a relatively new use of geothermal energy. People have used Earth's natural hot water directly since the dawn of humankind.
This historical drawing depicts Native Americans using hot springs at what is now Calistoga, California. Some tribes considered hot springs to be neutral territory where no wars were allowed.
Use of hot springs by Maoris of New Zealand for cooking and other purposes extends into modern times.
Modern day Beppu Japan uses geothermal water and heat in buildings and factories and has 4,000 hot springs and bathing facilities that attract 12 million tourists a year.
Bathing in hot pools like these at Hot Creek, Mammoth Lakes, California, has been practiced throughout history. Be careful -- people and animals have been burned badly in unfamiliar pools.
Since Roman times, we have piped the hot water into pools to better control the temperature. These are photos of outdoor and indoor pool and spa bathing in Japan, the US, and Europe.
This small greenhouse is heated with geothermal water. Plants grow faster and larger when they have additional heat available.
In several western US states, many long greenhouses are built and heated with geothermal water. This one is in New Mexico.
Geothermal water is also used to speed the growth of fish. These are growing in a geothermally heated hatchery at Mammoth Lakes, California.
This net full of fish was grown in geothermally heated waters in California's Imperial Valley.
Closeup of a prawn grown in a research project with geothermally heated water at the GeoHeat Center, Oregon Institute of Technology.
These alligators are grown in geothermally heated water in Idaho.
Geothermal water is also used for industrial uses, like drying lumber or food products. This plant in Brady, Nevada, provides dried onions to Burger King.
Pipes of geothermal water can be installed under sidewalks and roads to keep them from icing over in winter, like this sidewalk in Klamath Falls, Oregon.
In some places, geothermal water is piped from wells to heat single homes or whole residential or commercial districts. This truck-mounted drill rig is drilling a well for use in Klamath Falls, Oregon.
This photo of Reykjavik, Iceland, was taken in 1932, when buildings were all heated by burning of (imported) fossil fuels.
Today, about 95% of the buildings in Reykjavik are heated with geothermal water. Reykjavik is now one of the cleanest cities in the world.
The first geothermal district heating system in the US was built in Boise, Idaho. Today, Boise's capital and city buildings are heated with a geothermal district heating system.
The areas in orange and red are where with today's technology, we can find and use geothermal reservoirs.
Geothermal heat pumps can be used almost everywhere in the world, without a geothermal reservoir. The insulating properties of the earth, just below our feet, can keep us warm or cool.
In a poll, over 95% of people who had installed a geothermal heat pump said they would recommend it and would do it again.
The entire U.S. (and most other areas of the world) are suitable for geothermal heat pumps. In the U.S., geothermal reservoirs occur primarily in western states.
It is of critical importance that we use energy sources that are easy on the environment.
Our modern world relies more and more on electricity -- to run our simplest household appliances, to keep businesses humming, to operate our computers and to light the night.
We rely on abundant, affordable energy. We must conserve, use energy more efficiently, and diversify our energy resource base.
Today, coal provides 55% of the U.S. electricity supply and the U.S. imports more than half of the oil it consumes. The burning of fossil fuels cannot be sustained.
Much air pollution is caused by burning of fossil fuels. The costs of pollution include health effects like rising rates of asthma, especially in children and especially in cities.
Currently we are using primarily fossil fuels.
What will be the consequences if our growing energy needs are also met by fossil fuels?
You can choose clean renewable energy from wind, solar, small hydropower and geothermal resources.
Discussion Questions
What is Geothermal Energy?
Geothermal Energy is energy from heat inside the Earth.
The centre of the Earth is around 6000 degress Celsius - hot enough to melt rock. Even a few kilometres down, the temperature can be over 250 degrees Celsius.
In general, the temperature rises one degree Celsius for every 36 meters you go down.
In volcanic areas, molten rock can be very close to the surface.
Geothermal energy has been used for thousands of years in some countries for cooking and heating.
The name "geothermal" comes from two Greek words: "geo" means "Earth" and "thermal" means "heat".
Summary:
How does Geothermal Energy Work?
Hot rocks underground heat water to produce steam. �We drill holes down to the hot region, steam comes up, is purified and used to drive turbines, which drive electric generators. There may be natural "groundwater" in the hot rocks anyway, or we may need to drill more holes and pump water down to them.
What are the advantages to using Geothermal Energy?
What are the disadvantages to using Geothermal Energy?
�You need hot rocks of a suitable type, at a depth where we can drill down to them. �The type of rock above is also important, it must be of a type that we can easily drill through. ��
Is Geothermal Energy Renewable?
Yes!
Geothermal energy is renewable. �The energy keeps on coming, as long as we don't pump too much cold water down and cool the rocks too much.
Geothermal power means getting __________ from hot __________ underground. This is __________ , as long as we don't take too much energy out. �Hot __________ comes up out of the hole we've drilled, and usually "flashes" into __________ which we can purify and use to drive turbines, which drive generators to make __________ . �At some sites we have to __________ water down, at others the hot water comes up anyway. Sometimes poisonous __________ come up too.�Geothermal power can be __________ , because there needs to be the right type of __________ , at a suitable __________ , where we can __________ down to it.
drill electricity gases heat pump
renewable rock water
rocks steam temperature unreliable
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