tidal energy. Factors in favor of using more tidal energy include that it is
environmentally friendly, in comparison to other forms of power produc-
tion, and the cost of maintenance and operation is low. The tidal energy is
essentially free for the taking if it can be captured. Underwater tidal
fences would have less impact on the environment, as they do not require
flooding a basin to generate power.
Tidal energy and the environment
There is only one major environmental concern associated with tidal
energy. It has to do with a possible ecological disturbance. The use of
dams or barrages may create disturbances to the surrounding ecological
environment.
Geothermal Energy
Geothermal energy is heat from the earth. Geo means “earth,” and
thermal relates to heat. The heat from the earth’s core continuously flows
outward. It is conducted by the surrounding rock known as mantle. The
mantle becomes molten and is then known as magma. Magma is located
miles beneath the earth’s surface. Heat from magma is trapped under-
ground. Sometimes, magma erupts from the earth in a volcano.
Underground water turns to steam when it comes near this molten rock.
Great amounts of steam are produced from the earth. The high pressure
from the steam is used to turn turbines connected to generators. The
generators then produce electricity. The production of electricity is the
greatest use of geothermal energy. The United States leads the world in
installed capacity of geothermal plants. Further development of
geo thermal energy for electrical generation is limited to locations where
the heated steam is close enough to the earth’s surface in order to make it
economically recoverable.
How a geothermal heat pump works
Heat pumps are another application of the use of geothermal energy.
They are used extensively for residential heating and cooling. The
geo thermal heat pump is based on the fact that ground temperature
remains an approximate 55°F. A geothermal heat pump system includes
pipes buried in the shallow ground and located near a home. Water flows
through the pipes and conducts heat from the ground for transfer into the
home. If the water enters the home at 55°F and that heat can be captured,
Chapter 5
110
Sluice gates
Barrage
Estuary floor
Low water mark
Basin
High water mark
Sea
Turbine
Figure 5-13. Tidal power can
be generated by allowing the
incoming tide to be
impounded behind a dam
(called a barrage). As the tide
recedes on the seaward side
of the barrage, the trapped
water is allowed to flow out,
rotating a turbine to generate
electricity.
Tidal fence: A
barrier intended to
prevent the power
of tides from
escaping back into
the ocean.
Geothermal energy:
Heat from the
earth.
Mantle: Rock that
conducts heat
coming from the
earth’s core.
Magma: Molten
rock located miles
beneath the earth’s
surface.
Heat pump: An
application of the
use of geothermal
energy for residen-
tial heating and
cooling. A system
of these pumps
consists of pipes
buried in the
shallow ground
and located near a
home. Water flows
through the pipes
and conducts heat
from the ground
for transfer into the
home.