Brief description of wind power

1. Wind Power Fundamentals:
1st Wind Energy Systems
– Ancient Civilization in the Near East / Persia
– Vertical-Axis Wind-Mill: sails connected to a vertical shaft connected
to a grinding stone for milling
Wind in the Middle Ages
– Post Mill Introduced in Northern Europe
– Horizontal-Axis Wind-Mill: sails connected to a horizontal shaft on a
tower encasing gears and axles for translating horizontal into rotational
motion for translating horizontal into rotational motion
Wind in 19th century US
– Wind-rose horizontal-axis water-pumping wind-mills found
throughout rural America
1888: Charles Brush builds first large-size wind electricity ( generation
turbine (17 m diameter wind rose configuration, 12 kW generator)
1890s: Lewis Electric Company of New York sells generators to retro-fit
onto existing wind mills
1920s-1950s: P ll rope er-t 2&3 type 2 & 3-blade horizontal-axis wind
electricity conversion systems (WECS)
1940s – 1960s: Rural Electrification in US and Europe leads to decline
in WECS use
Wind – Atmospheric air in motion

2. Energy source
Solar radiation differentially absorbed by earth surface converted
through convective processes due to temperature differences to air
motion
Spatial Scales
Planetary scale: global circulation
Synoptic scale: weather systems
Meso scale: local topographic or thermally induced circulations
Micro scale: urban topography
Wind energy is the kinetic energy that is present in moving air. The
amount of potential energy depends mainly on wind speed, but is also
affected slightly by the density of the air, which is determined by the
air temperature, barometric pressure and altitude.
For any wind turbine, the power and energy output increases
dramatically as the wind speed increases. Therefore, the most
cost-effective wind turbines are located in the windiest areas. Wind
speed is affected by the local terrain and increases with height above
the ground, so wind turbines are usually mounted on tall towers.
Application of wind energy:
1- Mechanical application: mainly (water pumping) Multi-blade
windmill used for water pumping
2- Electricity generation:
Wind turbines vary in size and type. They are commercially available for
electricity generation.
Size of wind turbines (400 Watt-5 MW)
How do wind turbines make electricity?

3. The wind turns the blades, which spin a shaft, which connects to a
generator and makes electricity.
Wind turbine types:
1- Vertical axis wind turbine (i.e. Darius wind turbine)
Advantages of vertical wind turbines
Vertical wind turbines are easier to maintain because most of their
moving parts are located near the ground. This is due to the vertical
wind turbine’s shape. The airfoils or rotor blades are connected by
arms to a shaft that sits on a bearing and drives a generator below,
usually by first connecting to a gearbox. As the rotor blades are vertical,
a yaw device is not needed, reducing the need for this bearing and its
cost. Vertical wind turbines have a higher airfoil pitch angle, giving
improved aerodynamics while decreasing drag at low and high
pressures.
Disadvantages of vertical wind turbines
There may be a height limitation to how tall a vertical wind turbine can
be built and how much swept area it can have. Most VAWTS need to be
installed on a relatively flat piece of land and some sites could be too
steep for them while available to HAWTs. VAWTs that use guy wires to
hold it in place create serious problems for the bottom bearing as all
the weight of the rotor is on it and the guy wires increase downward
thrust in wind gusts. Solving this problem requires a superstructure to
hold in place the top bearing that also can share the weight of the
rotor.

4. 2- Horizontal axis wind turbine (HAWT):
Advantages of horizontal wind turbines
In the horizontal wind turbine, the blades are to the side of the turbine's
centre of gravity, helping stability. They have the ability to wing warp,
which gives the turbine blades the best angle of attack. Allowing the
angle of attack to be remotely adjusted gives greater control, so the
turbine collects the maximum amount

5. of wind energy for the time of day and season. The blades also have the
ability to pitch the rotor blades in a storm, to minimize damage. Tall
towers allow access to stronger wind in sites with wind sheer. In some
wind sheer sites, every ten meters up, the wind speed can increase by
20% and the power output by 34%. Tall towers also allow placement on
uneven land or in offshore locations. These can be placed in forests
above the treeline. Most are self-starting. The horizontal wind turbines
can be cheaper because of higher production volume, larger sizes and, in
general, higher capacity factors and efficiencies.
Disadvantages of horizontal wind turbines
HAWTs have difficulty operating in near ground, turbulent winds
because their yaw and blade bearings need smoother, more laminar
wind flows. The tall towers and long blades (up to 180 feet long) are
difficult to transport on sea and land. Transportation can now account
for 20% of equipment costs. Tall HAWTs are difficult to install, needing
very tall and expensive cranes and skilled operators. The supply of
HAWTs is less than demand and between 2004 and 2006, turbine prices
increased up to 60%. At the end of 2006, all major manufacturers were
booked up with orders through 2008. The Federal Aviation
Administration (USA) has raised concerns about tall HAWTs' effects on
radar in proximity to air force bases. Height can be a safety hazard for
low-altitude aircraft. Offshore towers can be a navigation problem.

6. Downwind variants suffer from fatigue and structural failure caused by
turbulence.
Wind Turbine Glossary
Anemometer: Measures the wind speed and transmits wind speed data
to the controller.
Blades: Most turbines have either two or three blades. Wind blowing
over the blades causes the blades to "lift" and rotate.

7. Brake: A disc brake which can be applied mechanically, electrically, or
hydraulically to stop the rotor in
emergencies.
Controller: The controller starts up the machine at wind speeds of
about 8 to 16 miles per hour (mph) and shuts off the machine at about
65 mph. Turbines cannot operate at wind speeds above about 65 mph
because their generators could overheat.
Gear box: Gears connect the low-speed shaft to the high-speed shaft
and increase the rotational speeds from about 30 to 60 rotations per
minute (rpm) to about 1200 to 1500 rpm, the rotational speed required
by most generators to produce electricity. The gear box is a costly (and
heavy) part of the wind turbine and engineers are exploring
"direct-drive" generators that operate at lower rotational speeds and
don't need gear boxes.
Generator: Usually an off-the-shelf induction generator that produces
60-cycle AC electricity.
High-speed shaft: Drives the generator.
Low-speed shaft: The rotor turns the low-speed shaft at about 30 to 60
rotations per minute.
Nacelle: The rotor attaches to the nacelle, which sits atop the tower and
includes the gear box, low- and high-speed shafts, generator, controller,
and brake. A cover protects the components inside the nacelle. Some
nacelles are large enough for a technician to stand inside while working.

8. Pitch: Blades are turned, or pitched, out of the wind to keep the rotor
from turning in winds that are too high or too low to produce
electricity.
Rotor: The blades and the hub together are called the rotor.
Tower: Towers are made from tubular steel (shown here) or steel
lattice. Because wind speed increases with height, taller towers
enable turbines to capture more energy and generate more
electricity.
Wind direction: This is an "upwind" turbine, so-called because it
operates facing into the wind. Other turbines are designed to run
"downwind", facing away from the wind.
Wind vane: Measures wind direction and communicates with the yaw
drive to orient the turbine properly with respect to the wind.
Yaw drive: Upwind turbines face into the wind; the yaw drive is used
to keep the rotor facing into the wind as the wind direction changes.
Downwind turbines don't require a yaw drive, the wind blows the
rotor downwind.
Yaw motor: Powers the yaw drive.
The benefits of wind energy
Wind energy is an ideal renewable energy because:

It is a pollution-free, infinitely sustainable form of energy.

It doesn’t require fuel.

It doesn’t create greenhouse gasses.

It doesn’t produce toxic or radioactive waste.

9. Wind Energy & the Environment
Wind is a clean fuel; wind power plants (also called wind farms)
produce no air or water pollution because no fuel is burned to
generate electricity.
Drawbacks of Wind Machines
The most serious environmental drawbacks to wind machines may be
their negative effect on wild bird populations and the visual impact on
the landscape. To some, the glistening blades of windmills on the
horizon are an eyesore; to others, they're a beautiful alternative to
conventional power plants.
Introduction to Wind Energy
Wind Turbine
Wind turbines have been around for over a century. Engineers began
attempting to harness wind energy to generate electricity after the
invention of the electric generator in the 1830s. In 1887 and 1888, wind
power was produced in the United Kingdom and the United States, but
modern wind power is thought to have been invented in Denmark,
where horizontal-axis wind turbines were installed in 1891 and a
22.8-meter wind turbine was put into service in 1897.
The wind is generally used to generate electricity by using the KE (kinetic
energy) created by air in motion. Wind turbines or wind energy
conversion systems convert this into electrical energy. The blades of a
turbine are first struck by the wind, which causes them to rotate and
transform the turbine connected to them. By moving a shaft connected
to a generator and thereby generating electrical energy by
electromagnetism, kinetic energy is converted to rotational energy. The
size of the turbine and the length of its blades determine the amount of
power that can be harvested from the wind. The output is proportional

10. to the rotor's dimensions and the wind speed's cube. Wind power
capacity increases by a factor of eight as wind speed doubles, according
to theory.
Types of Wind Turbines
Wind turbines come in a variety of sizes. The blade length is the most
important factor in deciding how much electricity a wind turbine will
produce. Small wind turbines that will power a single home can generate
up to 10 kilowatts of electricity (kW). Wind turbines with
electricity-generating capacities of up to kilowatts (10 megawatts) are
currently in use, and larger turbines are being built. Large turbines are
often clustered together to form wind power plants, also known as wind
farms, which provide electricity to grids. Wind turbines can be divided
into two categories:
1. Horizontal-axis turbines
2. Vertical-axis turbines
Horizontal-axis Turbines
Horizontal-axis turbines have three blades, which are similar to
aeroplane propellers. The main horizontal-axis turbines have blades that
are more than 100 feet long and are as tall as 20-story buildings. More
electricity is produced by taller turbines with longer blades. Almost all
wind turbines in operation today are horizontal-axis turbines.
Vertical-axis Turbines
Blades are connected to the top and bottom of a vertical rotor in
vertical-axis turbines. The Darrieus wind turbine, named after the French
engineer Georges Darrieus, who patented the concept in 1931,
resembles a massive two-bladed egg beater. The vertical-axis turbine
can be 100 feet tall and 50 feet wide in some models. Since vertical-axis
wind turbines do not work as well as horizontal-axis turbines, they are
rarely used today.

11. Use of Wind Energy
 Wind energy is a cost-effective alternative. After the production tax
credit, the land-based utility-scale wind is one of the cheapest
energy sources available today, costing 1–2 cents per kilowatt-hour.
Wind energy mitigates the market volatility that fuel prices bring to
conventional sources of energy since its power is sold at a fixed price
for a long period of time and its fuel is free.
 Wind will create jobs. The wind industry in the United States
employs over 1 lakh people, and wind turbine technician is one of
the fastest-growing occupations in the nation. The wind can sustain
more than 6 lakh jobs in manufacturing, installation, maintenance,
and supporting services by 2050, according to the Wind Vision
Report.
 It's an environmentally friendly fuel source. Wind energy does not
pollute the environment in the same way that power plants that
burn fossil fuels, such as coal or natural gas do, emitting particulate
matter, nitrogen oxides, and sulphur dioxide, which cause public
health issues and economic losses. Wind turbines do not emit any
pollutants into the atmosphere that cause acid rain, smog, or
greenhouse gases.
 The wind is a renewable energy source that can be used in the home.
The wind supply in the United States is plentiful and unrestricted.
Wind power capacity in the United States has increased at a rate of
15% per year over the last ten years, making it the country's largest
renewable energy source.
 It is sustainable. Wind is a form of solar energy. Winds are caused by
the sun's heating of the atmosphere, the Earth's rotation, and the
irregularities on its surface. The energy generated by the sun and the
wind can be harnessed to send power through the grid for as long as
the sun shines and the wind blows.
 On existing farms or ranches, wind turbines may be built. This has a
significant economic impact in rural areas, where the majority of the
best wind sites are located. Farmers and ranchers will continue to
use the property because wind turbines only take up a small portion
of it. For the use of the property, wind power plant owners pay rent

12. to the farmer or rancher, providing additional revenue to the
landowner.
Challenges of Wind Power
 On a cost basis, the wind power must also compete with traditional
generation sources. Even though the cost of wind power has fallen
significantly in recent decades, wind projects must be able to
compete economically with the least costly source of energy, and
some areas might not be windy enough to be cost-effective.
 Strong land-based wind sites are commonly found in remote areas,
far from the cities that demand electricity. To get the electricity from
the wind farm to the city, transmission lines must be installed.
Building only a few of the already-proposed transmission lines, on
the other hand, could drastically reduce the costs of expanding wind
energy.
 Wind energy production may not be the most cost-effective use of
land. Alternative uses for land that may be more valuable than
power generation must compete with land appropriate for wind
turbine installation.
 Turbines have the potential to pollute the environment with noise
and odour. While wind power plants have a lower environmental
impact than traditional power plants, there is concern about the
noise produced by the turbine blades and the visual impact on the
landscape.
 Wind turbines have the potential to damage local wildlife. Birds have
been destroyed by flying into turbine blades that are spinning. The
majority of these issues have been addressed or significantly
reduced as a result of technological advancements or proper wind
plant placement. Wind turbine blades have also killed bats, and
research is currently underway to develop and strengthen ways to
mitigate the effect of wind turbines on these animals. Wind projects,
like all energy sources, have the potential to alter the ecosystem on
which they are installed, potentially reducing the habitat's suitability
for some species.

13. Windmills
A windmill is a mechanism that uses the kinetic energy of the wind to
produce mechanical energy. The windmill's blades spin in a clockwise
direction at all times. Daniel Halladay of the United States built the first
windmill in the year 1854.
Types of Windmills
There are two types of windmills depending upon the axis of rotation:
1. Vertical axis windmills
2. Horizontal axis windmills
 Post mill
 Smock mill
 Tower mill
 Fan mill
Components of Windmill
The following are the parts of a windmill:
 Blades: These are the most important parts of the windmill since
they regulate the rotor speed.
 Rotor: A propeller is also known as a rotor.
 Anemometer: An anemometer is a device that measures wind speed.
 Tower: The support structure that holds the blades and propeller
together is known as the tower.

14. Working of Windmills
After a lot of trial and error, the number of blades on the windmill was
calculated. Three blades were discovered to be the most effective, so
every windmill has three blades. Windmills get their energy from the
wind. When the blades come into contact with the wind, they travel in
such a way that the shaft begins to spin, producing electricity.
Mechanical energy is converted into electrical energy by the generator.
Use of Windmills
The main aim of a windmill is to transform wind energy into electrical
energy, and once that energy is produced, it can be used in the following
ways:
1. To pump groundwater.
2. Oil extraction from the seeds.
3. The grains are milled.
Conclusion
Turbines are a relatively new form of wind-energy technology. The
turbine, unlike the windmill, is only used as a stand-alone device when
only small amounts of wind energy are needed. Small-scale
multi-megawatt wind farms and large-scale multi-megawatt wind farms
are more common. Wind farms are increasingly popular on ridges, open
pastures, and plains, as well as offshore wind farms in the ocean, as
demand for renewable energy and wind power increases. Modern wind
turbines are much more sophisticated than mills. They have big blades
attached to the base, which makes them identical. A gearbox and a
generator are located within the turbine. The horizontal-axis turbine,
which has a few longer blades that resemble an aeroplane propeller, is
the most well-known. The vertical-axis turbine, on the other hand, is a
lesser-known form with shorter and wider blades

15. WHAT IS A WIND TURBINE?
The concept of harnessing wind energy to generate mechanical power
goes back for millennia. As early as 5000 B.C., Egyptians used wind
energy to propel boats along the Nile River. American colonists relied on
windmills to grind grain, pump water and cut wood at sawmills. Today’s
wind turbines are the windmill’s modern equivalent -- converting the
kinetic energy in wind into clean, renewable electricity.
HOW DOES A WIND TURBINE WORK?
The majority of wind turbines consist of three blades mounted to a
tower made from tubular steel. There are less common varieties with
two blades, or with concrete or steel lattice towers. At 100 feet or more
above the ground, the tower allows the turbine to take advantage of
faster wind speeds found at higher altitudes.
Turbines catch the wind's energy with their propeller-like blades,
which act much like an airplane wing. When the wind blows, a pocket of
low-pressure air forms on one side of the blade. The low-pressure air
pocket then pulls the blade toward it, causing the rotor to turn. This is
called lift. The force of the lift is much stronger than the wind's force
against the front side of the blade, which is called drag. The combination
of lift and drag causes the rotor to spin like a propeller.
A series of gears increase the rotation of the rotor from about 18
revolutions a minute to roughly 1,800 revolutions per minute -- a speed
that allows the turbine’s generator to produce AC electricity.
A streamlined enclosure called a nacelle houses key turbine components
-- usually including the gears, rotor and generator -- are found within a
housing called the nacelle. Sitting atop the turbine tower, some nacelles
are large enough for a helicopter to land on.
Another key component is the turbine’s controller, that keeps the rotor
speeds from exceeding 55 mph to avoid damage by high winds. An
anemometer continuously measures wind speed and transmits the data
to the controller. A brake, also housed in the nacelle, stops the rotor
mechanically, electrically or hydraulically in emergencies. Explore the
interactive graphic above to learn more about the mechanics of wind
turbines.

16. TYPES OF WIND TURBINES
There are two basic types of wind turbines: those with a horizontal axis,
and those with a a vertical axis.
The majority of wind turbines have a horizontal axis: a propeller-style
design with blades that rotate around a horizontal axis. Horizontal axis
turbines are either upwind (the wind hits the blades before the tower)
or downwind (the wind hits the tower before the blades). Upwind
turbines also include a yaw drive and motor -- components that turns
the nacelle to keep the rotor facing the wind when its direction changes.
While there are several manufacturers of vertical axis wind turbines,
they have not penetrated the utility scale market (100 kW capacity and
larger) to the same degree as horizontal access turbines. Vertical axis
turbines fall into two main designs:
 Drag-based, or Savonius, turbines generally have rotors with solid
vanes that rotate about a vertical axis.
 Lift-based, or Darrieus, turbines have a tall, vertical airfoil style
(some appear to have an eggbeater shape). The Windspire is a
type of lift-based turbine that is undergoing independent testing
at the National Renewable Energy Laboratory's National Wind
Technology Center.
WIND TURBINE APPLICATIONS
Wind Turbines are used in a variety of applications – from harnessing
offshore wind resources to generating electricity for a single home:
 Large wind turbines, most often used by utilities to provide power
to a grid, range from 100 kilowatts to several megawatts. These
utility-scale turbines are often grouped together in wind farms to
produce large amounts of electricity. Wind farms can consist of a
few or hundreds of turbines, providing enough power for tens of
thousands of homes.
 Small wind turbines, up to 100 kilowatts, are typically close to
where the generated electricity will be used, for example, near
homes, telecommunications dishes or water pumping stations.
Small turbines are sometimes connected to diesel generators,
batteries and photovoltaic systems. These systems are called

17. hybrid wind systems and are typically used in remote, off-grid
locations, where a connection to the utility grid is not available.
 Offshore wind turbines are used in many countries to harness the
energy of strong, consistent winds found off of coastlines. The
technical resource potential of the winds above U.S. coastal
waters is enough to provide more than 4,000 gigawatts of
electricity, or approximately four times the generating capacity of
the current U.S. electric power system. Although not all of these
resources will be developed, this represents a major opportunity
to provide power to highly populated coastal cities. To take
advantage of America’s vast offshore wind resources, the
Department is investing in three offshore wind demonstration
projects designed to deploy offshore wind systems in federal and
state waters by 2017.
FUTURE OF WIND TURBINES
To ensure future growth of the U.S. wind industry, the Energy
Department’s Wind Program works with industry partners to improve
the reliability and efficiency of wind turbine technology, while also
reducing costs. The program’s research efforts have helped to increase
the average capacity factor (a measure of power plant productivity) from
22 percent for wind turbines installed before 1998 to more than 32
percent for turbines installed between 2006 and 2012. Wind energy
costs have been reduced from more than 55 cents per kilowatt-hour
(kWh) in 1980 to under 6 cents/kWh today in areas with good wind
resources.
Wind turbines offer a unique opportunity to harness energy in areas
where our country's populations need it most. This includes offshore
wind's potential to provide power to population centers near coastlines,
and land-based wind's ability to deliver electricity to rural communities
with few other local sources of low carbon power.
The Energy Department continues working to deploy wind power in new
areas on land and at sea and ensuring the stable, secure integration of
this power into our nation's electrical grid.

18. Define the Working of a Wind Turbine
From massive wind farms that generate kilowatts of electricity each day
to a single vertical axis wind turbine at the farmhouse, all work on the
same principle of current alternative production. Turbines attached to
the blades are placed high above the ground, and most of them have
three blades attached to them. When the wind blows, these blades
move, and a pocket of low-pressure air forms one side of the blade. This
low pressure pulls the blade towards it, making the rotor turn. This
phenomenon is known as a lift in wind power turbines. The force that
the lift puts on the blade is much stronger than the force put by the
wind against the other side of the blade, known as drag. The perfect
combination of drag and lift causes the rotor to propel at a much faster
speed.
Inside Wind Power Turbines
Now let's talk about what's inside the wind power turbines. Inside a
wind turbine, we have a series of gears that increase the rotor's rotation
from above 18 revolutions a minute to roughly 1800 revolutions per
minute. These 1800 revolutions cause the turbine to generate
alternating current electricity. All the turbine components are stored in
one location, which is called a nacelle, and it includes all the gears,
rotors, and generators. You might be surprised to know that, but some
turbines have such a massive nacelle that even a helicopter can land on
them.
Different Types of Wind Turbines
Two different forms make the wind power plants of wind turbines, and
we will explain each of them in this section.

19. Horizontal-axis Turbines
If you look at the horizontal-axis turbines, you will see they are more like
an airplane propeller and have three blades in them. The largest air
turbine stands tall at the height of a 20 story building, and the blades are
100 feet long. Nearly all the wind power turbines which you see today
are horizontal-axis turbines.
Vertical-axis Turbines
These turbines have blades that are attached at the top and the bottom
of the vertical rotor. The most common type of vertical wind turbine is
the Darrieus wind turbine, named after the engineer who invented it. If
you look at this turbine from a distance, it will look like a massive
two-bladed egg beater. Some of the vertical-axis turbines are 100 feet
tall, and others could be 50 feet depending on the location in which they
are installed. In the modern age, there are only a few places where you
can find a vertical-axis turbine making electricity as electricity
production is low. They do not perform as well and efficiently as
horizontal-axis turbines.
Use of Wind Energy
 The first and the foremost use of wind energy is to generate clean
electricity with big and small wind turbines.
 The second is transportation; for many years, people were using sails
to travel the world; before there were diesel engines to make the
ships move, humans took the assistance of wind energy to traverse
the sea. On the other hand, modern shipping companies are
researching ways to use wind energy for their transportation as it is a
free and clean form of energy.
 Wind energy is also used for wind sports, such as windsurfing, land
sailing, kitesurfing, etc.

20. Conclusion
Now you know how wind generators produce electricity and the
different types of wind power turbines. Wind power is not something
new, and as a civilization, we have been harnessing it for our users for
quite a few centuries now. In the next ten years, wind energy will be
more efficient, and more wind farms will be set up to take advantage of
a renewable resource.
What is wind energy? How is wind energy used to produce electricity?
How much electric power is generated in India using wind energy?
Let us first know what wind energy is.
Wind power, often known as wind energy, is the utilization of wind
turbines to generate mechanical power, which is then used to turn
electric generators to generate electricity. When opposed to burning
fossil fuels, wind power is a popular sustainable, renewable energy
source that has a significantly lower environmental impact.
Lets see how it's produced: The sun's uneven heating of the atmosphere,
differences in the earth's surface, and the earth's rotation all contribute
to wind. Wind turbines work by revolving propeller-like blades around a
rotor to convert wind energy into electricity. The rotor rotates an
electric generator, which rotates the driving shaft. Wind speed, air
density, and swept area are three important elements that influence
how much energy a turbine can extract from the wind.
In the fiscal year 2017-18, wind power accounted for over of India's total
installed power generation capacity, generating 28,604 million Kwh
(MU), or nearly of total electricity generation.
Apart from generating electricity wind energy has many other uses:
Other uses of wind energy are in transportation, sports like wind surfing,
kite flying, some boats ,etc. it is also used for pumping water and
production of food in some cases.
Note:
We have only looked at the pros of wind energy There are a few cons
also, let's look at a few cons. Noise and visual pollution occur on a
regular basis and The blades of a wind turbine are quite massive and
rotate at very high speeds, which has certain negative environmental

21. consequences. Unfortunately, species that fly into them, such as birds
and bats, can be harmed or killed. Wind farms can potentially damage
natural habitats of local species if they are not built in a sustainable way.
What is wind energy? Mention its two advantages.
Wind energy is the electrical energy obtained from harnessing the wind
with windmills or wind turbines. Wind power or wind energy is
described as the process of using blowing wind in order to generate the
mechanical power through wind turbines to turn electric generators and
traditionally to do other work, such as milling or pumping. The
mechanical power produced by the turbines can be used for specific
tasks, such as grinding grain or pumping water. An electrical generator
can convert this mechanical power into electricity.
Wind farms or wind parks are also called wind power stations. The
turbines in a wind farm are connected directly to the electric power
transmission network. Wind turbines give variable power which is
consistent from year to year but varies greatly over short time scales.
Therefore, wind energy must be used with other energy sources or
storage to give reliable supply.
Advantages of using Wind energy:
1. Wind power is cost effective: Land based utility scale wind is one of
the lowest priced renewable energy sources available today. It only costs
between four and six cents per kilowatt-hour, depending upon the wind
resource and project financing of a particular project.
2. Clean fuel source: Wind energy is a clean and pure energy source.
Wind energy does not pollute the air like other energy sources which
rely on combustion of fossil fuels such as coal or natural gas. Also, wind
energy does not emit dangerous gases such as nitrogen oxide and
sulphur dioxide.
Note: Wind energy is the cheapest available form of new electricity
generation at present. Wind power sources are more expensive than
power from old established power plants, but are cost competitive with
any new power plant. Wind energy mitigates the price uncertainty that
fuel costs add to traditional sources.

22. What is Windmill?
A windmill is a big structure also called a mechanical device that
transforms wind energy into electrical energy. It is a big structure that
contains sails mounted on a rotating shaft.; these rotating sails help
transform wind’s kinetic energy into electricity.
These sails make an angle so that when they rotate, the force of the
wind against them is divided into the two following components:
 One in the plane of sails, and
 Another imparts rotation
Windmills are prime movers that have replaced humans as a source of
power and in this article, you will learn to make this device.
What is Windmill and How it Works?
Windmill has been a useful source of power from last many years, even
during the World War-I, windmills maker produced 10,000 farm
windmills each year for water-pumping.
At present, windmills are used for electricity generation, and this
electricity generation is possible because of the blades that are
constructed by the concept of aerodynamic analysis and the other
performance-enhancing equipment.
Working Principle
A windmill is a big structure contains sails that are attached by a fixed
rotating shaft, as you can see in the image below. The rotating shaft
rotates these blades that help convert the kinetic energy of wind into
electricity.

23. Now, let’s understand its basic working:
When a blowing wind forces the blades, these rotating blades generate
electricity because of the generator attached to the windmill. Do you
know how blowing wind turns a wing?
If we closely look at the cross-section of the blade, it has a lot many
airfoils on the surface.
The concept of an airfoil is simple. Whenever there is a pressure
difference between the two surfaces, an upward force acts on the blade,
which is a dynamic lift.
Since all the blades have airfoils, in this way, a lift generates in all the
three blades, which makes these wind turbine blades turn, as we
encounter with the windmills in the farm.
Relative Velocity of Wind Turbines
Just like moving trains, wind turbines also experience the wind
relatively. So the relative velocity of the wind is given by the following
formula:
VRELATIVE = VWIND - VBLADE
So, the relative velocity is the difference between the velocity of the
wind and that of a blade. So that’s why blades are tilted in such a way
that they align to the relative wind speed.
Now, as the blade velocity increases to the tip, the relative velocity
becomes more inclined towards the tip, which means a continuous twist
is given to the blade from the root to tip.
Since due to low mechanical strength and wind noise, the blades don’t
rotate and give high rpm with a generator.

24. How to Gain Maximum Speed in a Windmill?
Now, what we do is, we connect a gearbox before the generator, which
helps achieve a high-speed ratio of 1: 90 (cut-off speed of 80 kmph). A
brake is also fitted in a nacelle that helps tackle the wind arrest during
windy conditions. Consecutively, the electricity generated is transferred
to the transformer filled at the base of the windmill.
This is how a windmill works. Now, we will learn about the types of
windmills.
Types of Windmills
There are various types of windmills, so let’s understand their types
one-by-one:
Post mill
Smock mill
Fan mill
Tower mill
Use of Windmill
Windmills have a mounted wind turbine that captures most energy
and performs various tasks that have replaced human beings as a source
of power. They are used in the following places:
They are used for pumping water,
For grinding grains, and
Generating electricity.

25. Explain the principle of working on a windmill.
To begin with the principle of working of a windmill, first we need to
know what this device is called a windmill. A windmill is a device that
uses vanes called sails or blades to transform wind power into rotational
energy, primarily to mill grain (gristmills), but the concept is often
applied to windpumps, wind turbines and other applications. A wind
turbine is a specially developed windmill-like device to produce
electricity. They can be seen as the next step in the windmill’s
development.
The words "wind energy" and "wind power" both describe the
mechanism by which the wind is used to produce electricity or
mechanical power.
On a simple idea, wind turbines run. The energy in the wind spins a rotor
across two to three propeller-like blades. The rotor is attached to the
main shaft, which generates electricity by rotating a generator. Kinetic
energy in the atmosphere is turned into mechanical electricity by wind
turbines. For basic activities (such as grinding grain or pumping water),
this mechanical power can be used or a generator can turn this
mechanical power into electricity.
To absorb the most electricity, wind turbines are installed on a pole.
They will take advantage of quicker and less turbulent wind at 100 feet
( 3030 metres) or more above ground. Wind turbines can be used to
generate energy for a single home or house, or for more distributed
delivery of electricity, they can be connected to an electricity grid.
Note: It is important to note that windmills provide extra edge over
other forms of energy as they require renewable resources to provide
energy i.e. air or wind. However, if in any region where the strength of
air or wind is low, then windmills cannot operate at optimum level. This
is the drawback of windmills.

26. Renewable Energy
What is Renewable Energy
Renewable energy, as the name suggests is an energy which can be
renewed or replenished. It is often referred to as 'clean energy' because
it is less harmful to the environment as compared to non-renewable
energy. Renewable energy is obtained from natural resources and
processes that are constantly replenished. Whenever a question raises
that what is renewable energy, we can simply say that it is the energy
obtained from the resources which constantly renew themselves, hence
it is available in sufficient amounts for our use such that it won't finish
no matter how much we use it. Sunlight and wind energy can be taken
as an example. These resources keep flourishing even if their availability
is dependent on time and weather respectively.
Renewable Energy Definition
It is the type of energy obtained from the resources which do not
deplete or replenish themselves within a human's lifetime. It is opposite
to the energy obtained from depleting fossil fuels.
Renewable Energy Resources
These are those resources which produce renewable energy. They are
mostly present in nature. To the question 'what are renewable energy
sources', we can say that a renewable source is a natural resource that
either through natural reproduction or other recurring processes
replenishes the depleted or consumed amount of resource within a
finite time interval on the human time scale. Solar, wind, biomass,
geothermal and water(hydro) are major renewable resources.
Types of Renewable Energy
Here are some major renewable energy examples.
1) Solar Energy
Solar energy is the energy obtained from the sun. The radiant light and
heat energy is harnessed by solar collectors. The sun's energy can be
captured to generate electricity or heat through a system of panels or
mirrors.

27. Solar, or photovoltaic, cells convert sunlight directly into electricity while
solar thermal collectors use heat-absorbing panels and a series of
attached circulation tubes to heat water or buildings.
2) Wind Energy
Wind power or wind energy makes the use of wind to provide the
mechanical power to electric generators through wind turbines so that
they can do operations like milling or pumping. The wind hits two or
more propeller-like blades around a rotor. This rotor is connected to the
main shaft connected to the generator so that when the rotor moves it
moves shaft in turn, hence electricity is produced as generator operates.
These turbines are installed mostly in high altitude areas.
3) Geothermal Energy
Earth has its own thermal energy stored in it. The energy that is
generated from the thermal energy stored in the earth is called
geothermal energy. Hot springs and volcanoes are used to capture the
heat energy and this heat is directly used by industries for heating the
water and other purposes.
4) Hydropower
Hydropower or hydroelectricity is the energy generated by the use of
water. Dams and reservoirs are constructed on flowing water which uses
the kinetic energy of the water to run turbines and in turn, generate
electricity. Hydropower is also generated by making use of tides known
as tidal energy. Also, energy from the surface of ocean waves is used to
produce electricity known as wave energy.
5) Bioenergy
Bioenergy is derived from biomass which is organic waste of animals and
plants. Biomass contains stored chemical energy. It is burnt to produce
bioenergy. It may be converted to biofuel and then used or it can
directly be used to produce heat through combustion. The heat
generated from combustion is used to run generators to produce
electricity.

28. What are the limitations of obtaining energy from wind?
Energy can be classified into two categories depending on their sources.
(i) Renewable energy
(ii) Non-renewable energy
Wind is a renewable energy as it comes from natural sources or
processes that are constantly replenished.Another example of
renewable energy is solar energy.Coal, oil, and natural gas are the
non-renewable sources of energy. They are also called fossil fuels as
they are products of plants that lived thousands of years ago.We always
observe the wind is winding. Then one can think why not this wind can
provide sufficient energy to use it in different sectors such as energy
sources for the future generation.But due to the limitation, we are not
able to obtain the energy from the wind.
These limitations are:
1) The wind has limited speed which lessened the resultant kinetic
energy of the wind energy.
2) The speed of the wind is not constant. So the inconsistency in speed is
not suitable for getting stable energy. It can not be controlled.
3) Production of wind energy is a long-term process i.e. it requires a long
time to get a significant amount of energy.
4) To produce wind energy, we require a large area to make wind farms.
Consuming a large place affects the surroundings.
5) It also increases the production cost.
6) If wind speed is low we can not get sufficient energy.
7) Wind energy depends on change in season or weather. We can not
always use wind energy.
Additional information:
Wind energy converts the kinetic energy of wind into mechanical
power.The overall impact of wind energy is minor compared to other
energies such as solar energy.
Note:Students can be confused between different kinds of energy
sources.Students should understand there are so many advantages to
using renewable energy sources. But they also have so many
disadvantages. So, we can not completely depend on renewable energy
sources.

29. Importance of Renewable Energy
The importance of renewable energy lies in the need for renewable
energy over the conventional form of energy. Some important points are
given below.
1) Renewable energy is a source of clean, inexhaustible energy.
2) It is pollution-free as it doesn't produce any greenhouse gas and
polluting emissions which are otherwise produced in case
non-renewable sources.
3) The costs for renewable energy is also falling at a sustainable rate
opposite to the rate trend of fossil fuels.
4) It reduces energy dependence on fossil fuels.
5) It can be easily generated because renewable sources are mostly
present all around, there is no non-availability issue.
6) Both economically and environmentally, renewable technologies are
becoming competitive to conventional sources of energies.
Uses of Renewable Energy
1) The major use of all renewable energies is to generate electricity. In
2018, 26.2 percent of global electricity requirements was fulfilled by
renewable energy which is expected to rise up to 45 percent by 2040.
2) Solar energy can be directly used for heating and lighting homes, for
hot water heating, solar cooling etc.
3) Biomass is also used to heat buildings and provide heat in industries.
It is also used as a fuel when converted to liquid biofuel.
What are the Disadvantages of Renewable Energy?
 Higher upfront cost is the biggest disadvantage renewable energy
holds. It includes capital cost, upfront building or land cost,
installation cost etc.

30.  Intermittency is another factor. Renewable resources aren't present
24×7 and whole year round which is not the case in fossil fuels.
 Because they are not always available they need to be stored which
again is a bit difficult and expensive as well.
 Renewable energy also has geographical limitations. You need to
have a large farmhouse or open land to install a wind turbine or solar
energy system for their significant use. All geographies aren't
suitable for renewable technologies.
Wind Power
Wind power or wind energy describes the process by which the wind is
used to generate mechanical power or electricity. Wind turbines convert
the kinetic energy in the wind into mechanical power. This mechanical
power can be used for specific tasks (such as grinding grain or pumping
water), or can be converted into electricity by a generator.
You can learn how wind turbines make electricity and see an illustration
of the components inside a wind turbine, or view a wind power
animation that shows how moving air rotates a wind turbine’s blades
and how the internal components work to produce electricity.
Wind Turbine Sizes and Applications
Wind turbines can provide energy for onsite use as well as for export for
sale. The energy needs will determine the size of the turbine.
Wind turbine economics are maximized when the project size is
designed to match the energy needs of the load while also monetizing
economies of scale and equipment track record. Residential onsite
energy use requires a small turbine (typically less than 10 kilowatts (kW))
that can generate the amount of power that the home requires for daily
operation. Midsize machines can produce enough energy to match
larger commercial onsite loads. Utility-scale machines that maximize

31. generation for the site infrastructure footprint and cost are best suited
for utility-scale projects.
Regardless of project size, projects connected to the electrical grid will
require utility approvals and may require grid impact studies before
construction can begin.
Residential-Scale Onsite Energy Use (<10 kW)
Residential, small turbines produce about as much energy as a home
requires. Because these turbines are generally installed on shorter
towers, you need to get a site evaluation in order to determine where to
site the project to ensure it will perform as designed. These wind
turbines are purchased with cash, so while return on investment can be
important to consider, it is not always the deciding factor of whether a
project goes forward. Many states provide incentives for this class of
machine. Residential-scale wind turbines typically do not warrant a
detailed onsite resource assessment.
Small Commercial-Scale Onsite Energy Use (10-50 kW)
This class of wind turbine produces more power than the average house
consumes but can be well suited for small businesses; farms; ranches;
facilities such as schools, office buildings, or part of a campus; or a public
load such as a hospital. This turbine class typically incorporates a higher
level of machine sophistication, resulting in greater efficiency and power
production but also requiring increased maintenance. These turbines,
however, typically require less maintenance than larger machines. This
class of machine can cost as much as a house and is the smallest project
size that might be financed, which would require a lender review.
Projects of this size may also trigger the need for onsite resource
assessment, but often projects can move forward by using nearby
measurements and experienced siting and project modeling.
Commercial Onsite Energy Use (50-250 kW)
This wind turbine class produces commercial quantities of power and
can be well matched with campuses, larger facilities, communities, and
larger municipal public loads. This wind turbine class shares many
technical and operational attributes of utility-scale machines and is often
installed on towers that require special permits and coordination with

32. other regulatory organizations or agencies. These turbines often
represent a substantial capital investment and thus require corporate or
institutional approvals. It is not unusual for facility managers to partner
with financial players while developing projects of this size. These
projects require experienced and detailed project modeling using onsite
or nearby wind resource data.
Large Commercial or Industrial Energy Use (500 kW-1.5 MW)
This wind turbine class is at the top end of the midsize machines and is
well suited for communities and very large onsite industrial loads and
can even form the basis of small wind farms in certain situations. This
machine class is typically indistinguishable from utility-scale turbines on
a technology basis. The towers often exceed 200 feet, which need to be
fitted with obstruction lighting. Projects of this size warrant community
involvement and endorsement or approval at all levels. This class, except
in very unusual situations, is typically financed through commercial
lenders with their own due-diligence requirements and therefore
require feasibility studies and onsite resource assessment campaigns.
Utility-Scale Energy Use (1.5-7.5 MW)
Utility-scale wind turbines, while also occasionally installed at the point
of use, are generally installed in large groups producing energy for sale.
These are highly efficient, state-of-the-art wind turbines that operate
with exceptionally high availability rates and generate cost-competitive
electricity at power plant scales. These large turbines have rotors
measuring more than 250 feet in diameter and are installed on tall
towers that require aviation obstruction notification and lighting.
Because of their size and the scale of the installations, utility-scale wind
turbines require environmental, utility, and public coordination at the
highest levels. Utility-scale wind farms require exacting resource
assessments, legal and financial due diligence, utility integration, and
financing typical of very large capital investments installations, such as
airports.

33. Wind Energy Formula
Wind energy is a kind of solar energy. Wind energy describes the process
by which wind is used to produce electricity. The wind turbines convert
the kinetic energy present in the wind to mechanical power.
Wind energy is a renewable source of energy that determines the total
power in the wind. The wind turbines which convert kinetic energy to
mechanical power, wherein the mechanical power is converted into
electricity which acts as a useful source.
The wind energy formula is given by,
Where,
P = power,
ρ = air density,
A = swept area of blades given by
where r is the radius of the blades.
V = velocity of the wind.
Example 1
Determine the power in the wind if the wind speed is 20 m/s and blade
length is 50 m.
Solution:
Given:
Wind speed v = 20 m/s,
Blade length l = 50 m,
Air density ρ = 1.23 kg/m.
The area is given by,
A = π × 2500

34. = 7850 m
The wind power formula is given as,
P = 38622 W
Example 2
A wind turbine travels with the speed is 10 m/s and has a blade length of
20 m. Determine wind power.
Solution:
Given:
Wind speed v =10 m/s,
Blade length l = 20 m,
air density ρ = 1.23 kg/m3,
area ,
= π × 400
= 1256
The wind power formula is given as,
= 0.5 × 1.23 × 1256 × 1000
P = 772440 W.

35. Non-conventional Sources of Energy
Renewable energy sources, often known as non-conventional energy,
are sources that are renewed by natural processes on a continual basis.
Solar energy, wind energy, bio-energy (bio-fuels cultivated sustainably),
hydropower, and other sustainable energy sources are some
examples.
A renewable energy system transforms energy from the sun, wind,
falling water, sea waves, geothermal heat, or biomass into heat or
electricity that humans can utilize. The majority of renewable energy
originates from the sun and wind, either directly or indirectly, and can
never be depleted, which is why it is termed renewable.
However, traditional energy sources such as coal, oil, and natural gas
provide the majority of the world’s energy. Non-renewable energy
sources are the word used to describe these fuels. Despite the fact that
the accessible amount of these fuels is enormous, they are finite and
will, in theory, ‘run out’ at some point in the future.
Why is it necessary to use non-conventional energy sources?
With rising energy use, the population is becoming increasingly reliant
on fossil fuels such as coal, oil, and gas. Because the prices of gas and
oil continue to rise with each passing day, it is necessary to guarantee
future energy supplies. As a result, we must employ more and more
renewable energy sources. The government of India has established a
distinct department called the “Department of non-conventional
sources of energy” for the effective exploitation of non-conventional
sources.
Some advantages of Non-conventional energy sources:
 They are renewable in nature.
 They produce little or no pollution as compared to traditional
energy sources.
 They require little maintenance.
 They are a long-term cost-effective choice.

36. Some disadvantages of Non-conventional energy sources:
 The initial setup cost is greater.
 Energy cannot be taken 24/7, year-round, because certain days
will be windier than others, and the sun will shine. stronger on other
days.
 Energy must be stored. Geographical locations might be difficult
to navigate.
Non-conventional Sources of Energy
1. Solar Energy
Since prehistoric times, solar energy has been the most easily available
and free source of energy. Every year, solar energy estimated to be
equivalent to approximately 15,000 times the world’s annual
commercial energy consumption reaches the planet. For 300 to 330
days per year, India receives solar energy in the range of 5 to 7
kWh/m2. This energy is enough to run a 20-megawatt solar power
plant per square kilometer of land.
The NTPC project would have nearly twice the capacity of Rajasthan’s
Bhadla solar park, which is presently the country’s largest
single-location solar power plant. By 2032, NTPC hopes to have built 60
GW (gigawatts) of renewable energy capacity.
“Longer-term benefits will come from the development of affordable,
unlimited, and clean solar energy technologies,” the International
Energy Agency declared in 2011. It would strengthen countries’ energy
security by depending on an abundant, limitless, and mostly
import-free supply. It boosts sustainability, decreases pollution, cut
climate change mitigation costs, and keep fossil fuel prices lower than
they would be otherwise. These benefits are widespread. As a result,
the increased expenses of early deployment incentives should be
viewed as learning expenditures that must be carefully spent and

37. equitably shared “. Australia has the highest amount of solar power in
the world, accounting for 9.9% of total electricity demand in 2020.
Solar thermal devices are utilized in residential and industrial solar
water heaters, air warmers, solar cookers, and solar dryers.
a) Solar water heaters:
It comprises a thin, flat, rectangular box installed on the roof of a
building or residence with a transparent cover towards the sun. Small
tubes go through the box, carrying the fluid to be heated, which might
be water or another fluid like an antifreeze solution. The tubes are
connected to a heat-absorbing absorber plate, which is coated with
specific coatings. Heat is generated in the collector and transferred to
the fluid flowing through the tubes.
The most efficient, but also the most expensive, form of hot water solar
collector is the evacuated tube collector. Glass or metal tubes with a
vacuum are used in these collectors, allowing them to work in colder
areas.
b) Solar cooker:
A solar cooker is a device that cooks using sun energy, reducing the
need for fossil fuels, wood, and electricity to a considerable amount.
However, it can only be used to augment cooking fuel, not to
completely replace it. It is a basic cooking device that is suitable for
home use throughout most of the year, with the exception of the
monsoon season, overcast days, and the winter months. Solar cookers
in a box: In India, the box solar cookers with a single reflecting mirror
are the most common. These cookers have become quite popular in
rural regions where women spend a significant amount of time
gathering firewood.
c) Solar Photovoltaic (PV):
Using the photoelectric effect, a photovoltaic system transforms light
into electrical direct current (DC). Solar PV has grown into a
multibillion-dollar, fast-growing business that is continuing to increase
its cost-effectiveness and, together with CSP, has the highest promise
of any renewable technology. Lenses or mirrors, as well as tracking
systems, are used in concentrated solar power (CSP) systems to focus a
wide region of sunlight into a tiny beam. Concentrated solar power
facilities were first produced commercially in the 1980s.

38. The technical name for solar electric is photovoltaic. Photo is short for
“light,” while voltaic is short for “electric.” PV cells are typically
constructed of silicon, a material that releases electrons spontaneously
when exposed to light. The amount of electrons emitted by silicon cells
is proportional to the amount of light shining on it. The silicon cell is
encased in a metal grid that guides electrons along a route to produce
an electric current. This current is directed into a wire that connects to
a battery or a DC device. One cell typically produces 1.5 watts of
electricity. Individual cells are linked to make a solar panel or module
with a power output of 3 to 110 watts. Solar panels may be linked in
series and parallel to form a solar array that can produce as much
power as space allows. Modules are typically intended to provide 12
volts of power. The peak Watt production of PV modules is measured
at solar noon on a clear day.
d) Pumps for Solar Water:
The pump in a solar water pumping system is powered by a
solar-powered motor rather than traditional energy taken from the
utility grid. A solar array placed on a platform and a motor-pump set
compatible with the photovoltaic array make up an SPV water pumping
system. It transforms solar energy into electricity, which is then utilized
to power the motor-pump system. Water is drawn from an open well, a
bore well, a stream, a pond, or a canal via the pumping system.
2. Wind Energy
Wind energy is the process of harnessing wind power to generate
electricity. The wind’s kinetic energy is transformed into electrical
energy. Because of the earth’s curvature, various parts of the
atmosphere are heated to varying degrees when solar radiation enters
the atmosphere. The equator receives the most heat, while the poles
receive the least.
Winds are created as air moves from warmer to colder locations, and it
is these airflows that are captured in windmills and wind turbines to
generate electricity. Wind power is not a new discovery; it has been
utilized for millennia in the form of conventional windmills – for
grinding maize, pumping water, and sailing ships. With improved

39. technology, wind power can now be used to create energy on a bigger
scale.
With a potential of 20,000 MW, India has been identified as one of the
most attractive countries for wind power development. As of
September 2001, the world’s total installed capacity of wind power
generators was 23270 MW. Germany has 8100 MW, Spain has 3175
MW, the United States has 4240 MW, Denmark has 2417 MW, and
India has 1426 MW. As a result, India is ranked fifth in the world for
wind energy generation. Tamil Nadu has 39 wind potential stations,
Gujarat has 36, Andhra Pradesh has 30, Maharashtra has 27, Karnataka
has 26, Kerala has 16, Lakshadweep has 8, Rajasthan has 7, Madhya
Pradesh has 7, Orissa has 7, West Bengal has 2, Andaman Nicobar has 1
and Uttar Pradesh has 1. Seven of the 208 eligible stations had a wind
power density of greater than 500 Watts/m2.
3. Biomass Power
Biomass is a renewable energy source made up of carbon-based waste
from human and natural activity. It comes from a variety of places,
including wood industry by-products, agricultural crops, forest raw
material, domestic trash, and so on. Biomass does not emit carbon
dioxide into the atmosphere since it absorbs the same amount of
carbon throughout its growth as it emits when burned. It has the
benefit of being able to generate energy using the same equipment
that is now used to burn fossil fuels.
Biomass is a significant source of energy and, after coal, oil, and natural
gas, the most important fuel on the planet. Bio-energy, in the form of
biogas, is anticipated to become one of the most important energy
sources for worldwide sustainable development. Biomass, in the form
of Biogas, has a better energy efficiency than direct burning.
Biogas is a clean and efficient fuel made from cow dung, human waste,
or any other biological substance that has been fermented
anaerobically. The biogas contains 55-60% methane and the remainder
is mostly carbon dioxide. Biogas is a non-toxic fuel that may be used for
cooking and lighting. The by-product can be used as high-quality
manure.

40. Biomass fuels make for roughly a third of the country’s overall fuel use.
It is the primary source of energy for over 90% of rural families and
around 15% of urban households. Energy and manure are produced
using solely local resources, such as cow dung and other organic wastes.
As a result, biogas plants are low-cost energy sources in rural regions.
4. Hydropower
The commencement of the industrial revolution was driven by the
potential energy of falling water, which was collected and transformed
to mechanical energy by waterwheels.
Rivers and streams were dammed and mills were erected wherever
there was enough head or change in elevation. A turbine spins because
water under pressure flows through it. The Turbine is linked to a
generator, which generates power.
The potential of small hydropower in India is estimated to be over
10,000 MW. By the end of March 1999, India has installed a total of
183.45 MW of small hydro projects. Small hydropower plants with a
capacity of 3 MW have been erected separately, while a 148 MW
project is now being built.
5. Ocean and Tidal Energy
a) Tidal Energy:
The building of a barrage across an estuary to prevent the incoming and
outgoing tides is required for tidal power generation. As with
hydroelectric dams, the head of water is utilized to drive turbines that
create energy from the raised water in the basin.
Barrages can be built to generate power on the ebb, flood, or both
sides of the river. The tidal range can range from 4.5 to 12.4 meters
depending on the location. For cost-effective operation and adequate
head of water for the turbines, a tidal range of at least 7 m is necessary.
b) Ocean Power:
Oceans encompass more than 70% of the Earth’s surface, making them
the biggest solar collectors on the planet. Ocean energy is derived from
water waves, tides, and thermal energy (heat) stored in the ocean. The

41. sun warms the topwater far more than the deep ocean water, storing
thermal energy in the process.
6. Geothermal Energy
It is a type of energy that comes from the earth. It is trapped in the
Earth’s crust at a depth of 10 km in the form of hot springs, geysers,
and other natural phenomena. About 250 hot springs with
temperatures ranging from 90 to 130 degrees Celsius have been
discovered in areas like Puga Valley in Ladakh, Manikaran in Himachal
Pradesh, and Tattapani in Chhattisgarh, indicating that India’s
geothermal potential is largely found along the Himalayas. The National
Aerospace Laboratory in Bangalore has established a pilot project near
Manikaran for research and development as well as data collection in
order to construct larger geothermal power plants.
India boasts the world’s largest renewable energy programs. In India’s
villages and towns, a variety of renewable energy solutions have been
created and utilized. In 1992, the Ministry of Non-Conventional Energy
Sources (MNES) was established to oversee all aspects of
non-conventional and renewable energy. The government of India also
established the Renewable Energy Development Agency Limited (IREDA)
to assist and give financial assistance for renewable energy projects in
the form of subsidies and low-interest loans.
Any country’s long-term economic success and progress are
inextricably linked to the development and security of its energy
sectors. In light of conventional energy sources’ finite and limited
reserves, as well as their environmental effect, a strong focus should be
placed on the development of non-conventional energy sectors and
their efficient usage for the benefit and advancement of society. Such
efforts would also aid in the creation of a large number of job
possibilities at all levels, particularly in rural regions. As a result, for
emerging countries, mainstreaming non-conventional and renewable
energy technology is becoming increasingly important. The
non-conventional and renewable energy industries in India have a lot of
room for growth. India is the only country with a dedicated ministry for

42. non-conventional energy sources. India has the world’s biggest
decentralized solar energy program, the world’s second-largest biogas
and improved stove program, and the world’s fifth-largest wind energy
program.
Wind Energy
A turbine converts the kinetic energy of the wind to useful mechanical
energy. This energy could be used in mechanical form or turn generator
turbines and provide electricity. Just like in the hydropower systems,
wind energy is harnessed through conversion of the wind kinetic energy
to mechanical energy.
The wind turbines are largely classified into two types- Horizontal Axis
Wind Turbines and Vertical Axis Wind Turbines. Large areas installed
with wind turbines, that is, wind farms are increasingly emerging today.
Wind Characteristics
There are general characteristics of wind while others are more specific
to the site. Some of the site specific characteristics include −
Mean wind speed − This estimates the annual wind yield though it does
not give the distributions.
Wind speed distribution − There are three aspects namely annual,
diurnal and seasonal characteristics. Understanding the wind speed
variations and the spread is necessary when choosing a site.
Turbulance − This is the chaotic movement of wind in unpredictable
patterns. Turbulance results from continuously changing properties of
wind motion that impact on energy production and fatigue on blades.
Long term fluctuation − Irregular wind causes unpredictable energy
supply. Before a wind turbine is set, the area should be studied for a
constant wind flux.

43. Distribution of wind direction − This is more significant in positioning of
the blades especially for horizontal axis types.
Wind shear − Shear is change in wind direction, speed or the height at which
the maximum velocity occurs.
Wind Speed Patterns
Wind patterns are important and are often analyzed using a wind spectrum.
A high value of the wind spectrum represents a large change in the wind
speed at the given time interval. If represented on a graph, the peaks depict
turbulences that occur with time.
Wind speed distribution
There are three distributions −
Diurnal − Caused by the difference between temperatures during the day and
at night.
Depressions − Occur with four-day intervals along the coastal region.
Annual − Distribution is latitude dependent.
Wind Energy - Basic Theory
To understand wind energy, we subscribe to the theory of conservation
of mass and conservation of energy. A duct shown below is assumed to
represent wind flowing in and out of the blades of the turbine.

44. The velocity Va is assumed to be the average of V1 and V2. Kinetic
energy at the mouth of the tube is given by −
KE = 1/2 mV2
KE of energy changed = 1/2 mV12 - 1/2 mV22
1/2 m(V12 - V22)
Since m = p.A.Va then KE change, Pk = 1/2 p.A.Va (V12 - V22)
On further simplification, the estimated wind energy is give as −
KE, pk = 0.5925 * 1/2pAV13
Blade Element Theory
The blade element theory assumes that the flow at a given part of a
wind turbine blade does not affect the adjacent parts. This subdivision
on the blade is called annulus. The momentum is calculated for
each annulus. All the resultant values are then summed up to represent
the blade and hence the entire propeller.
On each annulus, an equally distributed velocity is assumed to have
been induced.
Dynamic Matching
The dynamic inflow model was incorporated to improve the estimations
by the Blade Element and Momentum theory. The basic dynamic in flow
theory concept helps estimate the effect of blade turbulence. The
swept area is given a dynamic state to help in deriving estimate mean
velocity.
The BEM theory gives estimates only at steady wind but it is obvious
that turbulences must occur. However, this is accounted for by the
basic dynamic inflow model to provide a more realistic estimate.
Wind energy produced, especially in the horizontal axis type, is known
to be the product of tip speed, the total number of blades used and the
lift-to-drag ratio of the side with an aerofoil. The readjustment to a new
steady state of equilibrium is well explained by the Dynamic Inflow
Method (DIM).

45. Dynamic Inflow Method
DIM is also known as dynamic wake theory and is based on the induced
flow, which is normally not steady. It calculates the inflow vertical to
the rotor taking into consideration its effect on the dynamic flow.
This simply takes into consideration the wake effect or simply the
velocity of the air vertically aligned with the rotors caused by the
turning of the blades. It however assumes the tangential velocity to be
steady. This is referred to as the Wake effect and its drag lowers the
efficiency of a wind turbine.
Electricity Generation
The kinetic energy in wind is converted to electricity by wind turbines.
They use the ancient concept used in windmills though with inherent
technology, such as sensors, to detect wind direction. Some wind
turbines have braking system to halt in case of strong winds to protect
the rotor and blades from damage.
There are gears connected to the rotor shaft to accelerate the blades to
a speed suitable for the generator. Inside the generator,
electromagnetic induction (the basic method of conversion from
mechanical energy to electricity) occurs. The shaft rotates a cylindrical
magnet against an electric wire coil.
All electricity from the turbines in a wind power station is assimilated to
a grid system and converted to a high voltage. This is actually the
conventional technique of transmitting electricity in the grid system.
Large surface-tipped blades are needed although this should be
determined by the noise that results from wide blades. A wind farm
may have up to 100 generators, which will result in more noise.

46. Wind Energy - Wind Turbine Types
There are two broad classifications of wind turbines −
 Horizontal Axis Wind Turbines (HAWT)
 Vertical Axis Wind Turbines (VAWT)
Let’s discuss these two types of wind turbines in a little detail.
Horizontal Axis Wind Turbines
These are windmill-like turbines with the top of the shaft pointing
towards the wind direction. Since they have to be pointed towards the
wind, smaller turbines are directed by wind vanes mounted on the
structure. Larger turbines have wind sensors with servo to turn the
turbines.
They are also fitted with gear-boxes to accelerate the slow rotation to
make it strong enough for the generator turbines. The blades are stiff
enough to avoid breaking or bending due to the turning moment of the
wind.
This type is mounted on a tower; hence they experience high velocity
winds. They are slightly bent to reduce the sweep area. A lower sweep
area reduces resistance, which may cause fatigue and failure.
Vertical Axis Wind Turbines
The main root is mounted on the vertical shaft. This eliminates the
difficulties associated with horizontal wind turbines. The subtypes
include −
Darius Wind Turbine
This is also known as the egg-beater turbine and resembles a huge egg
beater. It is efficient but may have more down times and hence less
reliable. To improve on solidity (blade area over rotor area) three or
more blades should be used.

47. Savonious Wind Turbine
These types have a greater reliability than Darius turbines. The problem
is that they cannot be mounted on top of towers. Therefore, they are
exposed to turbulent and irregular wind patterns. Since they are
drag-type of turbines they are less efficient compared to the HAWT. The
advantage is that they are able to withstand extreme turbulence.
Most VAWT cannot self-start and require external energy to give them a
jolt. For optimal performance, VAWTs should be mounted on roof-tops.
The roof channels the wind into the blades.