In the land where Etruscans bathed in natural hot springs almost 3,500 years ago, warm geothermal water has been in use for centuries, treating skin diseases, offering relaxation, heating buildings, producing useful chemicals like borax, and growing plants. But Italy’s greatest geothermal claim to fame is the development of the world’s first geothermally-driven electrical power plant in Larderello. Opened in 1904, the plant was producing 132 megawatts by the 1940s. Even when the power plants were destroyed in World War II, the geothermal reservoir remained and so the energy source was not lost. Soon the power plants were rebuilt, and today the area produces enough clean geothermal electricity for over a half a million lucky Italians.

From the first power plant in Larderello, Italy, to the state-of-the-art facilities found all over the world today, geothermal plants use natural hot water and steam from the earth to run turbine generators. Technological advances are making this a cost-effective resource. Expect to see its increased use in the near future, especially in the geothermally active western United States, Indonesia, and other “hot spots” around the Pacific.

Where are all the toxins coming from? Power plants, factories, and transportation vehicles are the obvious big culprits. But there are other contributors too: wood stoves, fossil fuel-burning furnaces, paints, dry cleaners, and (surprise!) bakeries (due to the fermentation process). It’s time we get to work ridding ourselves of these hazardous emissions. A good place to start is by using (whenever we can) energy sources which don’t pollute, including geothermal energy.


A Perfect Union

Heat and water. A match made in heaven. Or-in this case-earth.

First, there’s the heat. Natural heat generates deep in the earth, where it is actually hot enough to melt rock. This molten rock, called magma, flows up towards the surface of the earth, and – like a giant mobile furnace – heats other nearby rock.

Now comes the water. Seeping far below earth’s surface, huge amounts of rainwater can get trapped in porous rock (rock filled with many holes). If the water-filled rock is hot, it becomes a “reservoir” of steamy hot water – “carrier” of earth’s internal heat. It might surface as a powerful geyser or an inviting hot spring. Or it might stay right where it is. Then, if a well is drilled into it, up comes the steam and hot water, bringing us clean energy from the earth.

Geothermal Power Plants-


Geothermal power plants provide electricity without pollution.

AIR – Geothermal power plants leave the air clean, because they do not burn fossil fuels. They generate no nitrogen oxides, only a minuscule amount of sulfur, and less than 5% of the carbon dioxide emitted by coal-fired plants. And “binary” geothermal plants have no emissions at all.

WATER – After doing its job in the power plant, cooled geothermal water is safely returned through an “injection” well into the geothermal reservoir below. The geothermal water never mixes with other groundwater.

LAND – Land areas for geothermal plants are smaller, per megawatt, than for other types of power plants. Better still, the land around a geothermal plant can be used for other purposes, such as livestock grazing. Drilling for geothermal water is far easier on the environment than mining for coal or drilling for oil – no mine shafts, tunnels, open pits, waste heaps or oil spills. And fuel does not have to be transported: a geothermal plant literally sits on top of its fuel source.

Geothermal Resources have:



Around the world, geothermal resources are delivering clean electrical power. In the U.S. alone, geothermal’s power-generating capacity is already 2,800 megawatts, the equivalent of burning 60 million barrels of oil each year. Worldwide, about 6,000 megawatts of electricity are “currently” being generated from geothermal resources in 21 countries. The method used by different geothermal power plants varies-depending on the temperature and other characteristics of its geothermal water or steam-but all geothermal plants use basically the same process: the hot water (usually 250 degrees F – 600 degrees F) and/or steam is brought up to the surface through a well and piped right into the power plant to provide the force that spins the turbine.


Geothermal water is being used all around the globe, replacing or supplementing the need for conventional energy sources. Ranging in temperature from 70 degrees F to over 200 degrees F, hot water from the earth bathes and soothes humans, helps grow poinsettias and cucumbers in greenhouses while snow drifts pile up outside, cajoles alligators and fish into growing faster, dries onions and wood, washes wool, and provides space heating the world over. Space heating, both for individual buildings and even for entire districts of buildings, is the most common and oldest direct use besides bathing. Here, geothermal water is run through a heat exchanger to heat clean city water, and then returned to the geothermal reservoir where it heats up to be used again.


Earth heat is used worldwide to warm or cool buildings. In the U.S. alone, the temperature inside over 100,000 homes and offices is kept comfortable by energy-saving geothermal heat pumps (GHPs). GHPs rely on the relatively constant temperature of the earth (around 55 degrees F) just a few yards below the surface. GHPs circulate water or other fluid through many lengths of closed-loop piping, buried either horizontally or vertically underground. With the help of a heat exchanger, the fluid “extracts” earth’s heat and transfers it into a building during cold weather; and, by switching it into “reverse,” removes heat from a building during hot weather and deposits it into the earth. GHPs use very little electricity and are very easy on the environment.


Do Try This at Home


Hold a small mirror (with a handle or tongs for safety) above a lit candle or a kerosene or oil lamp. Soot and condensed water will form on the mirror. The soot is carbon, such as is produced by the burning of fossil fuels.

Hold a mirror above a source of steam (e.g., teapot, vaporizer.) Only condensed water will form.


Most electricity is made by burning fuel to boil water, making steam to turn turbines. Geothermal steam is a natural resource which can turn turbines. Discuss environmental implications of this demonstration in relation to energy sources.

SAFETY TIPS: Wear a hot mitt. Don’t hold the mirror too long over the heat, or it may slip due to moisture. Wash/dry the mirror before/ between demonstrations.


Ask Arthur

Q. I’ve heard that we could be using a lot more geothermal energy if we make a greater investment in research and development. Is this true?

J.B., H.S. Junior, Hawaii.

A. Great question! That rumor is right on! Today, electric power from geothermal energy faces stiff competition from cheaper power generated from natural gas. So, one of the main ways to increase geothermal usage is to reduce its cost. The way to cut the cost is to improve the technology. And the way to improve the technology is through research and development (R&D.)

You will be pleased to learn that the geothermal industry, in partnership with the U.S. Government, is pursuing R&D to cut the costs of making electric power from hydrothermal (hot water) geothermal reservoirs. Active projects include:

onew methods for exploration to find geothermal resources hidden beneath the ground surface;

oadvanced technology for drilling in the hard, hot rock formations that are typical of geothermal reservoirs;

obetter ways of managing the production of geothermal fluids to achieve the greatest energy recovery; and,

oengineering improvements for geothermal power plants, so that they can make more power at a lower cost.

Also, there are enormous amounts of geothermal energy stored in rock formations that contain no water (”hot dry rock”) and in liquid magma deep within the earth’s crust. Scientists and engineers have developed ways to recover this energy, but these ways are not yet cheap enough for use. Further R&D is need to bring down costs, but these unconventional geothermal resources hold a bright promise for the future.


Steam Press is published annually by the Geothermal Education Office, a non-profit organization partially funded by the U.S. Department of Energy. Contributions are appreciated and deductible to the extent allowed by law. Tax ID#68-0234213. Geothermal Education Office, 664 Hilary Drive, Tiburon, CA 94920, 1-800-866-4GEO. All materials appearing in Steam Press may be reproduced only with permission. Copyright 1995.


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