What is Tidal Energy?
Tidal energy is a form of hydropower that converts the
energy of the tides into electricity or other useful forms of
power. The tide is created by the gravitational effect of the
sun and the moon on the earth. Tidal energy is therefore a
predictable form of renewable energy, which can be
harnessed in two forms:
Basic physics of tides
•Gravitational pull of the sun
and moon and the pull of the
centrifugal force of rotation
of the earth-moon system.
•When a landmass lines up
with the earth-moon
system, the water around it
is at high tide.
•When a landmass is at 90 ͦ
to the earth-moon system,
the water around it is at
There are two high tides and two
low tides during each period of
rotation of the earth.
Spring and Neap tides depend on
the orientation of the sun, moon,
and the earth.
▫ High spring tides occur when the
sun and moon line up with the
earth. This occurs whether they
are either on same or opposite
▫ Low neap tides occur when the
sun and moon line up at 90 ͦ to
Flood Currents: currents moving in
the direction of the coast.
Ebb Currents: the current receding
from the coast
Tidal Range is the vertical difference between the high tide
and the succeeding low tide. Tides are the rise and fall of sea
levels caused by the combined effects of the gravitational
forces exerted by the moon and the sun and the rotation of
the Earth. The tidal range is not constant, but changes
depending on the relative positions of the Earth, sun and
moon. Barrages and lagoons use this potential energy
component of the tide to generate energy
Tidal Stream is the flow of water as the tide ebbs and floods,
and manifests itself as tidal current. Tidal stream devices seek
to extract energy from this kinetic movement of water, much
as wind turbines extract energy from the movement of air.
The sea currents created by movement of the tides are often
magnified where water is forced to flow through narrow
channels or around headlands. There are a number of
locations around the coastline of the UK where the tidal
stream resource is high, and it is in
these areas where early technology
developments are taking place to
explore the prospect of realizing the
Although not yet widely used, tidal power has potential for
future electricity generation. Tides are more predictable than
wind energy and solar power. Among sources of renewable
energy, tidal power has traditionally suffered from relatively
high cost and limited availability of sites with sufficiently high
tidal ranges or flow velocities, thus constricting its total
availability. However, many recent
and improvements, both in
design indicate that the total
availability of tidal power
maybe much higher than
previously assumed, and that
economic and environmental
costs may be brought down to
The Rance Tidal Power Station is the world's first tidal power
station and also the world's second biggest tidal power
station. The facility is located on the estuary of the Rance
River, in Brittany, France. Opened on the 26th November
1966, it is currently operated by Électricité de France.
The Annapolis Royal Generating Station is a 20 MW tidal power
station located on the Annapolis River immediately upstream
from the town of Annapolis Royal, Nova Scotia, Canada. It is
the only tidal generating station in North America. The
generating station harnesses the tidal difference created by
the large tides in the Annapolis Basin, a sub-basin of the Bay
of Fundy. Opened in 1984, the Annapolis Royal Generating
Station was constructed by Nova Scotia Power Corporation.
Tidal power issues
Tidal power can have effects on marine life. The turbines can
accidentally kill swimming sea life with the rotating blades.
Some fish may no longer utilize the area if they were
threatened with a constant rotating object.
Salt water causes corrosion in metal parts. It can be difficult
to maintain tidal stream generators due to their size and
depth in the water. Mechanical fluids, such as lubricants, can
leak out, which may be harmful to the marine life nearby.
Proper maintenance can minimize the amount of harmful
chemicals that may enter the environment