E ALL WANT TO LIVE, GO TO SCHOOL, AND WORK IN BUILDINGS THAT ARE
warm or cool enough. We want lighting in our homes and electricity
for computers and other electronics. The energy needed to do these things
comes mostly from fossil fuels—coal, oil, and natural gas—which are extracted
from the Earth. Burning these fuels releases carbon dioxide and other greenhouse
gases into the atmosphere. The buildup of greenhouse gases, which trap heat and
increase the Earth’s temperature, can significantly alter the Earth’s climate.
But there are also efficient sources of energy that are not expensive and do not pollute the environment. Solar and wind power are increasingly being used, and they are environmentally friendly.
The main downside is that they require plenty of sun or wind. But another source of energy, which
is clean, efficient, and available 24 hours per day, all-year-round, may be an even better alternative
in some areas. This energy comes from inside the Earth. So why isn’t it more widely used?
Tapping the Earth’s energy
The Earth’s internal energy is contained in rocks and fluids beneath the Earth’s crust. As long as
the Earth’s core stays hot—which is expected for the next 5 billion years—this source of energy,
called geothermal energy, will not run out,
unlike coal and oil. So, power plants that
extract and distribute geothermal energy can
work all day and night, every day, regardless
of the weather.
Also, geothermal energy is better for the
environment than fossil fuels, which release
greenhouses gases, such as carbon dioxide.
In contrast, the geothermal power plants that
are currently in operation produce less than
1% of the amount of carbon dioxide released
by fossil-fuel power plants and little to none of
the other polluting gases.
Another advantage of geothermal energy is
that it can be cheaper than energy generated
from fossil fuels; it can also be tapped locally,
reducing dependence on foreign oil.
The first U.S. commercial geothermal power
plant opened at The Geysers in California in
1960. Since then, more geothermal power
plants have been built there, making The Geysers the largest geothermal development in
Three items are required for
a geothermal system: a heat
source, permeability, and water.
The heat is supplied by the Earth’s interior.
Most of this energy remains below the Earth’s
crust, heating nearby rock and water—
sometimes to levels as hot as 700 °F.
When water is heated by the Earth’s energy,
it can be trapped in permeable and porous
rocks under a layer of impermeable rock,
forming a geothermal reservoir. This hot geothermal water can erupt on the surface as hot
springs or geysers, but most of the time, it
In the case of hot springs or geysers, the
hot water is relatively easy to extract. But
when it is trapped deep underground, the hot
water needs to be found first, and then a well
is dug, often at a depth of up to one mile.
Steam from this hot water is then used to
produce electricity. The steam is fed to a turbine, where it passes through multiple rows
of blades (Fig. 1). As the steam impacts the
blades, it imparts some of its kinetic energy to
the blades. The steam turbine drives a generator, which uses electromagnets to convert the
kinetic energy into electrical energy.
After the steam is used, it condenses into
liquid water. This used water can be recycled
Figure 1. How a geothermal power plant works: (1) Hot water is pumped from deep underground through
a well under high pressure; ( 2) When the water reaches the surface, the pressure drops, which causes
the water to turn into steam; ( 3) The steam spins a turbine, which is connected to a generator that
produces electricity; ( 4) The steam cools off in a cooling tower and condenses back to water; and
( 5) The cooled water is pumped back into the Earth. R S G
Geothermal Power Plant
well Hot water
Turbine Generator 3
By Chris Eboch