Tidal power is a form of hydropower.
Exploits the rise and fall in sea levels due
to the tides, or the movement of water
caused by tidal currents.
Although not widely used, tidal power has
potential for energy generation and is
more predictable than wind power.
Tidal energy is not a new concept.
Energy in this form was used to grind
grains since 11th century in France and
Tidal Stream Systems:
These make use of the kinetic energy
of moving water to power turbines.
Barrage tidal power:
This type uses the potential energy
from the difference in height between
high and low tides.
A relatively new technology.
Tidal stream generators draw energy from
currents in the same way as wind turbines.
Water, being 832 times denser than air,
provides significant power from one generator.
As in wind power, location of the plant is
Tidal Stream Systems need to be
located in areas with fast currents where
natural flows are concentrated between
Examples of such sites include entrance to
bays and rivers, around rocky points,
headlands, or between islands.
Potential sites suggested include
Channel Islands in UK, Strait of Gibraltar,
East River in NYC, Cook Strait in NZ,
Vancouver island in Canada.
The picture shows rotors in Harland and
Wolff, Belfast, before installation in
An artist s impression of the 40 MW Pentland Firth design at adepth of
60m and a 20m rotor for power generation
Alongside is a hybrid image of
Marine Current Turbines existing
SeaFlow 300kW proto type
turbine which was the world s
first offshore tidal turbine and
was installed off Lynmouth,
Devon in May 2003.
An emerging tidal stream
technology is the shrouded tidal turbine
enclosed in a Venturi shaped shroud or
duct producing a sub atmosphere of low
pressure behind the turbine, allowing the
turbine to operate at higher efficiency and
typically 3 4 times higher power output
than a turbine of the same size in free
Tidal stream systems are low cost
compared to barrage and fence types.
The set-up cost for such systems is not
as high as that for barrage types.
Also the efficiency of the turbines can
be increased using shrouded turbines.
This method involves building a barrage over a
The barrage turbines generate as water flows
in and out of the estuary.
These systems are similar to a hydro dam that
produces Static Head or pressure head. When
the water level outside of the basin or lagoon
changes relative to the water level inside, the
turbines are able to produce power.
La Rance- a Barrage type Tidal Power
Plant in France
The power can be generated using either
of Ebb Generation (Outflow generation),
Flood Generation, Pumping, Two- basin
The placement of a barrage into an
estuary has a considerable effect on the
water inside the basin and on the
ecosystem. Many governments have
been reluctant in recent times to grant
approval for tidal barrages.
The impacts can be listed as
Changes in Turbidity, Salinity,
accumulation of sediments at the estuary
and increase in fish mortality.
These type of tidal plants have high
capital cost and a very low running cost.
As a result a tidal power scheme may not
produce returns for many years.
CON LUSION S:
A tidal power scheme is a long-term
source of electricity. It is important to
realize its full potential so that
Many countries have initiated tidal power
schemes in bay areas and in seas.
In India tidal power projects are being
developed in Gulf of Kutch and the Gulf of
It is the conversion of wind energy into
useful form of energy, like electricity
using wind turbines.
Wind power is used in large scale wind
farms for national electrical grids as well
as in small individual turbines for
providing electricity to rural residences or
It is estimated that there is 50-100 times
more wind energy than plant biomass
energy available on Earth.
The power in the wind can be extracted
by allowing it to blow past moving wings
that exert torque on a rotor. The amount
of power transferred is directly
proportional to the density of the air, the
area swept out by the rotor, and the cube
of the wind speed.
As a general rule, wind generators are
practical where the average wind speed
is 10 mph (16 km/h or 4.5 m/s) or
greater. Usually sites are pre-selected on
basis of a wind atlas, and validated with
Thus, Metrology plays an important role
in turbine placement.
Onshore turbine installations in hilly or
mountainous regions tend to be on
ridgelines generally three kilometers or
more inland from the nearest shoreline.
This is done to exploit the so-called
An on shore installation in Tamil Nadu, India.
Offshore wind development zones are
generally considered to be ten kilometers
or more from land.
Offshore wind turbines are less obtrusive
than turbines on land, as their apparent
size and noise can be mitigated by
An Offshore installation near Copenhagen
Near Shore Installations:
Near-Shore turbine installations are
generally considered to be inside a zone
that is on land within three kilometers of a
shoreline or on water within ten
kilometers of land.
These areas tend to be windy and are
good sites for turbine installation,
because a primary source of wind is
convection caused by the differential
heating and cooling of land and sea over
the cycle of day and night.
Wind turbines might also be flown in
high speed winds at altitude, although no
such systems currently exist in the
Asia s largest wind park in Satara district of Maharashtra with 201 MW on
installation, commissioned by Suzlon Energy in 2001
Wind power can be generated for a grid
as well for single customers.
Small Wind is defined as wind generation
systems with capacities of 100 kW or
less and are usually used to power
homes, farms, and small businesses.
These systems help to reduce or
eliminate electricity bills, to avoid the
unpredictability of natural gas prices, or
simply to generate clean power.
Growth and Cost trends:
Due to the exponential rise
in usage of wind energy
worldwide the wind energy
costs are reduced. However
installation costs have risen
A key issue debated about wind
power is its ability to scale to meet a
substantial portion of the world's energy
There are significant economic, technical,
and ecological issues about the large-
scale use of wind power that may limit its
ability to replace other forms of energy
Economics and feasibility:
Without the tax incentives (also know
as subsidies) almost no wind power
installation is economically feasible at
Intermittency and Variability:
Electricity generated from wind power
can be highly variable at several different
timescales: from hour to hour, daily, and
This variability can present substantial
challenges to incorporating large amounts of
wind power into a grid system, since to
maintain grid stability, energy supply and
demand must remain in balance.
There is an inverse relationship with wind
speed and peak demand of electricity.
The intermittency of wind seldom creates
problems when using wind power at low to
moderate penetration levels (though such
intermittency has caused problems for grid
stability in Denmark and Germany, where
penetration is greatest
Variability of wind output creates a
challenge to integrating high levels of
wind into energy grids based on existing
It is related to variability but
It is the short term (hourly or daily)
Because of its variable nature, wind
energy forecasting presents a challenge.
Wind energy is the best option available
in alternate energy sources.
India ranks 4th in world in terms of wind
According to 2006 data India has an
installed wind power capacity of
6270 MW. (Global Wind Energy Council
Wind Energy, as estimated is more than
surplus for present day human needs.
However the problems in areas of
intermittency, grid management,
predictability, energy storage, safety of
wildlife and others must be addressed to
realize its full potential.
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