Geothermal & Ocean Energy
Geothermal Energy
•  Beneath the earth’s surface
lies hot, molten rock
•  The energy it contains is
called geothermal or earth
energy
Uses:
•  Geothermal power
plants use the earth’s
natural heat to vaporise
water or an organic medium
•  This creates steam which
powers a turbine to generate
electricity
Geothermal Heat Plants
•  Require lower temperatures
and the heated water is
used directly
•  Near the source the heat
.can be used directly to
heat homes, buildings and
hot water supplies
Ocean Energy:
Wave, Current &
Tidal
•  Surfers use the
kinetic energy of
waves to push them
onto the shore
•  The kinetic and
potential energy in
waves can be used to
generate electricity
•  Wave-power
machines use the
vertical displacement
of the waves to produce
electricity
Wave Energy
•  A structure interacts
with incoming waves,
converting this energy to
electricity through a
hydraulic, mechanical
or pneumatic power
take-off system
•  Structure is kept in
position by a
mooring system or
placed directly on
seabed/seashore
•  Power is transmitted to
shore by a
sub-sea cable
Ocean Currents
Caused mainly by:
•  The rise and fall of
the tides
•  Regional differences
in temperature
•  Salinity and
•  The Coriolis effect
due to the rotation of
the earth
The motion of the
ocean
Tidal Currents
•  Caused by the rise
and fall of tides
resulting from
gravitational
interactions between
earth, moon and sun
•  Tidal currents occur
close to the shoreline
•  Kinetic energy in
currents are converted
in the same way that a
wind turbine extracts
energy from the wind,
using open-flow rotors
Generating
Electricity
•  Tidal power harnessed
by constructing a dam or
barrage across an
estuary or bay with a
suitable tidal range
•  Gates in barrage allow
incoming tide to build
up in basin behind it
•  Gates then close so that
when tide flows out the
water can be
channelled through
turbines to generate
electricity
Tidal Barrages
•  Tidal barrages
have been built
across estuaries in
France, Canada
and China
•  High cost and
environmental
objections have
limited this
technology’s
expansion