green engineering systems

University JNTU Kakinada

Regulation R 16

Year III Year

Semester II Semester

Teaching Classes 3+1

Credits 3

Name of the Faculty Singuru Rajesh

Unit II – Wind Energy

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Green Engineering Systems

UNIT-2: WIND ENERGY

SYLLABUS

Sources and potentials, horizontal and vertical axis, wind mills, performance characteristics, betzcriteria, types of winds, wind data measurement

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Ancient Windmill in Iran

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WIND Energy

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The wind is a by-product of solar energy. Approximately 2% of the sun's

energy reaching the earth is converted into wind energy.

The surface of the earth heats and cools unevenly, creating atmospheric

pressure zones that make air flow from high-to low-pressure areas.

The wind has played an important role in the history of human

civilization.

The first true windmill, a machine with vanes attached to an axis to

produce circular motion, may have been built as early as 2000 B.C.

Water Pumping Windmill

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WIND Energy

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These too were used for milling grain. It was not until a few

hundred years later that windmills were modified to pump water

Until the diesel engine came along, many transcontinental rail routes

in the U.S. depended on large multi-vane windmills to pump water

for steam locomotives.

They are best suited for pumping ground water in small quantities

to livestock water tanks. These wind turbines provided electricity

to farms

Farm windmills

Water Pumping Windmill

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WIND Energy

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A typical modern windmill looks as shown in the following figure.

Because it is invisible, it is not easily measured without special

instruments.

Wind velocity is affected by the trees, buildings, hills and valleys

around us.

Wind is a diffuse energy source that cannot be contained or stored for use

elsewhere or at another time.

In India Tamil Nadu, Maharashtra, Karnataka, Rajasthan and Gujarat

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In India states having

potential of wind

energy are:

Tamilnadu,

Maharashtra,

Karnataka,

Andhra Pradesh

Rajasthan and Gujarat

Classification of Wind Mills

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Wind turbines are classified into two general types:

1. Horizontal axis

2. Vertical axis.

Horizontal axis machine has its blades rotating on an

axis parallel to the ground.

Vertical axis machine has its blades rotating on an axis

perpendicular to the ground.

Classification of Wind Mills

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Horizontal Axis Wind Turbines

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Horizontal axis machine has its blades rotating on an axis parallel to the

ground.

This is the most common wind turbine design.

In addition to being parallel to the ground, the axis of blade rotation is

parallel to the wind flow.

Some machines are designed to operate in an upwind mode, with the blades

upwind of the tower.

In this case, a tail vane is usually used to keep the blades facing into the

wind.

Horizontal Axis Wind Turbines

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Some very large wind turbines use a motor-driven mechanism that turns

the machine in response to a wind direction sensor mounted on the tower.

Commonly found horizontal axis wind mills are

1. Aero-turbine mill with 35% efficiency

2. Farm mills with 15% efficiency

Farm mills Aero-turbine mill

Vertical Axis Wind Turbines

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Vertical axis machine has its blades rotating on an axis perpendicular

to the ground.

Although vertical axis wind turbines have existed for centuries, they are

not as common as their horizontal counterparts.

The main reason for this is that they do not take advantage of the

higher wind speeds at higher elevations above the ground as well as

horizontal axis turbines.

Vertical Axis Wind Turbines

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The basic vertical axis designs are the

• Savonius, which uses scoops to catch the wind & the

efficiency of 30%.

• Darrieus, which has curved blades & efficiency of 35%,

• Giromill or H-Darrieeus which has straight blades &

efficiency of 35%

Vertical Axis Wind Turbines

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Vertical Axis Wind Turbines

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A vertical axis machine need not be oriented with respect to

wind direction.

Because the shaft is vertical, the transmission and generator

can be mounted at ground level allowing easier servicing

and a lighter weight, lower cost tower.

Although vertical axis wind turbines have these advantages,

their designs are not as efficient at collecting energy from

the wind as are the horizontal machine designs.

Components of Wind Turbine

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Components

1. Rotor

2. Blades

3. Hub

4. Main Rotating Shaft

5. Gear Box System

6. Generator

7. Housing

8. Anemometer

9. Pitching System

10.Yaw system

11.Tower

12.Grid Connection

13.Cables and

14.Foundation

Components of Wind Turbines

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Working of Wind Turbines

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Horizontal Axis Wind Turbines

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Specifications of Large Wind Machine, India

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Rated Capacity 2.1 MW

Rotor Diameter 88m

Hub Height 80m

Cut-in wind Speed 3-4m/s

Cut-out Speed 25m/s

Number of blades 3

Power control Active blade pitching

Generator Type Asynchronous

Location Pune

Working of Wind Turbines

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Types of Wind

Types of winds

1. Planetary winds or Permanent Winds

2. Periodic Winds

3. Local Winds

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Types of Wind

1. Planetary winds or Permanent Winds

These winds blow from high pressure belts to low pressure belts in the same direction throughout the year.

They blow over vast area of continents and Oceans.

1. Easterlies

2. Westerlies

3. Polar Easterlies

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Types of Wind

2. Periodic Winds

The direction of these winds changes with the change of seasons.

Monsoon winds are the important periodic winds

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Types of Wind

3. Local Winds

These winds are winds that affect the local weather on a small scale

• Land and Sea Breezes

• Mountain and Valley Breezes

• Hot Winds

• Cold Winds

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Wind Data

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Measurements of Wind Speed are made by using Anemometers.

The wind velocity at any location usually varies rapidly and continuously, the variation being irregular

both in terms of period and amplitude.

It is observed that there are turbulent fluctuations occurring continuously with occasional gusts causing

peaks and valley.

The no of hours in a month or in a year when the wind speed lies in a certain range.

This information can also be computed from hourly wind speed data.

Betz Criteria

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Betz's law indicates the maximum power that can be extracted from the wind,

independent of the design of a wind turbine in open flow.

According to Betz's law, no turbine can capture more than 16/27 (59.3%) of the kinetic

energy in wind.

The factor 16/27 (0.593) is known as Betz's coefficient.

Practical utility-scale wind turbines achieve at peak 75% to 80% of the Betz limit.

Betz Criteria

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It is the flow of air over the blades and through the rotor area

that makes a wind turbine function. The wind turbine extracts

energy by slowing the wind down.

The theoretical maximum amount of energy in the wind that

can be collected by a wind turbine's rotor is approximately

59.3%.This value is known as the Betz limit.

If the blades were 100% efficient, a wind turbine would not

work because the air, having given up all its energy, would

entirely stop.

Betz Criteria

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If all of the energy coming from wind movement through a turbine were extracted as useful

energy, the wind speed afterwards would drop to zero.

If the wind stopped moving at the exit of the turbine, then no more fresh wind could get in; it

would be blocked.

In order to keep the wind moving through the turbine, there has to be some wind movement,

however small, on the other side with some wind speed greater than zero.

Betz's law shows that as air flows through a certain area, and as wind speed slows from losing

energy to extraction from a turbine, the airflow must distribute to a wider area.

As a result, geometry limits any turbine efficiency to a maximum of 59.3%.

Thank You

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SINGURU RAJESHM.Tech (MD), PGDEEM, B.Tech (ME)

Assistant ProfessorRaghu Engineering College(Autonomous)

Dakamarri, Bhimunipatnam Mandal, Visakapatnam Dist, Andhra Pradesh