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Exploring Energy
Science Texts for Close Reading
Geothermal Energy
How is electricity generated at a geothermal power plant? Well, it is often a lot like how electricity is
generated at a coal-fired power plant, but with one key difference. In both cases, water is heated into
steam, which turns a turbine connected to a generator. The generator converts the mechanical energy
of the spinning turbine into electrical energy that can be transmitted to homes and buildings through
transmission lines.
In a coal power plant, burning coal supplies the energy to heat the water. This process releases carbon
dioxide—a powerful greenhouse gas that contributes to global warming and climate change—and other
pollutants that can be harmful to the environment and human health into the atmosphere. But in a
geothermal power plant, this energy comes from heat that is already present below the Earth’s surface.
Geothermal energy is a good energy option in places where there is hot magma close to the Earth’s surface
that naturally heats water in the ground into steam. In such places, geothermal energy is a constant and
reliable source of energy.
Compared to coal and other fossil fuels, geothermal energy releases much less carbon dioxide into the
atmosphere1 and produces much less pollution. But geothermal energy isn’t a good option everywhere.
The best places for geothermal energy production are where there is a heat source, like magma, close
to the Earth’s surface, as well as a constant supply of water in the ground that can be heated into steam.
Some water can be pumped back into the ground after it is used, but some of it evaporates into the
atmosphere, so over time the water in the ground often needs to be replenished. During a drought, this
can be an issue. Also, there is evidence that the pumping of water into and out of the ground associated
with geothermal power can generate small earthquakes2.
With geothermal energy, there is no fuel cost, since the fuel is naturally-occurring magma. However,
upfront costs associated with building a new geothermal power plant and drilling wells to access the steam
underground can be high3.
1 National Renewable Energy Laboratory: Energy Analysis
2 University of California, Santa Cruz Newscenter: Geothermal power facility induces earthquakes, study finds
3 Geothermal Energy Association
Thermal energy Mechanical energy Electrical energy
