Wind energy

1. Ramgarh Engineering College
Green Energy Technology (EE614 )
6th Semester, Electrical Engineering
Arunabha Datta
Assistant Professor
Dept. of Electrical Engineering
Ramgarh Engineering College

2. DETAILED SYLLABUS
Module I: Introduction (4 Lectures)
• Basics of energy, conventional energy sources, fossil fuels
limitations, renewable energy sources, advantages and
limitations, global energy scenario, energy scenario of India,
new technologies (hydrogen energy, fuel cells, bio fuels).
Module II: Solar Energy (12 Lectures)
• Theory of solar cells, solar cell materials, I-V characteristics of
solar cell, PV module, PV array, MPPT, PV systems, Stand
alone and grid connected PV systems, storage, PV based water
pumping, solar radiation and its measurement, flat plate
collectors and their materials, applications and performance,
solar thermal power plants, limitations.

3. Module III: Wind Energy (10 Lectures)
• Wind power and its sources, site selection, power in the wind, impact of
tower height, classification of wind turbine and rotors, wind energy
extraction, betz’z limit, wind characteristics, performance and limitations
of wind energy conversion systems.
Module IV: Biomass and Geothermal energy (5 Lectures)
• Availability of biomass and its conversion theory, types of biomass,
gasification, biogas plant, biomass cogeneration, resources of geothermal
energy, thermodynamics of geo-thermal energy conversion, geothermal
power generation, environmental considerations.
Module V: Tidal, Wave and Ocean energy (6 Lectures)
• Introduction to tidal energy, tidal characteristics, tidal power plant, tidal
power development in India, introduction to wave energy, factors
affecting wave energy, principles of wave energy plant, OTEC,
applications of OTEC.

4. Module VI: Emerging technologies for power generation (5 Lectures)
• Fuel cells, Principle of working of various types of fuel cells and their
working, performance and limitations, future potential of fuel cells,
emergence of hydrogen, cost analysis of hydrogen production, hydrogen
storage.
Suggested Readings:
[1] Non-Conventional Energy Resources, D.S. Chauhan, New Age
International Pvt Ltd., 2006.
[2] D. P. Kothari, Rakesh Ranjan, Renewable Energy Sources and Emerging
Technologies, PHI, India,2011.
[3] Solar Cells: Operating principles, Technology and Systems Applications,
Martin Green, UNSW, Australia, 1997
[4] S. P. Sukhatme, Solar Energy, TMH, India. 2008.

5. Suggested Readings:
[5] Introduction to Wind Energy Systems: Basics, Technology and
Operation (Green Energy and Technology), by Hermann-josef Wagner,
ISBN: 9783642020223, Publisher: Springer, September 2009.
[6] Biofuels - Securing the Planet's Future Energy Needs, Edited by A
Demirbas Springer 2009
[7] Fuel Cells: The Sourcebook - New Edition 2004 Escovale 2004.
Reference Books:
[1] John Twiden and Tony Weir, Renewable Energy Resources, BSP
Publications, 2006.
[2] Renewable Energy, Third Edition, Bent Sorensen, Academic Press
August 2004
[3] Wind Energy Explained: Theory, Design and Application, by J. F.
Manwell, ISBN: 9780470015001, Publisher: John Wiley & Sons,
Publication Date: February 2010 .
[4] L.L. Freris, Wind Energy Conversion Systems, Prentice Hall, 1990.

6. Wind Energy
• Wind energy is the kinetic energy associated with movement
of large masses of air.
• These motions result from uneven heating of atmosphere by
the sun, creating temperature, density and pressure differences.
• Wind energy is harnessed as mechanical energy with the help
of wind turbine.
• The mechanical energy thus obtained can either be used as
such to operate farm appliances, water pumping, etc.,
• or converted to electric power and used locally or fed to a grid.
• A generator coupled to wind turbine is known as aero-
generator.

7. Major factors that have led to accelerated
development of the wind power are as follows:
(i) Availability of high-strength fiber composites for constructing
large low cost rotor blades
(ii) Falling prices of power electronics
(iii) Variable speed operation of electrical generators to capture
maximum energy
(iv) Improved plant operation, pushing the availability up to 95
per cent
(v) Economy of scale, as the turbines and plants are getting larger
in size
(vi) Accumulated field experience (the learning curve effect)
improving the capacity factor
(vii) Short energy payback (or energy recovery) period of about
one year

8. ORIGIN OF WINDS
• Global (or Planetary) Winds
• Local Winds
• Two major forces determine the speed and direction of
wind on global basis.
1. Primary force for global winds is developed due to
differential heating of earth at equator and Polar
Regions.
2. Spinning of earth about its axis produces Coriolis force,
which is responsible for deviation of air currents towards
west.

9. Global circulation of wind

10. Local Winds
• Localized uneven heating is responsible for local winds. Local
winds are produced due to two mechanisms:
1. The first is differential heating of land surface and water
bodies due to solar radiation.
2. The second mechanism of local winds is differential heating
of slope on the hillsides and that of low lands. The slope
heats up during the day and cools down during night more
rapidly than the low land.

11. Factors Affecting the Distribution of Wind Energy on
the Surface of Earth
(i) On planetary level, great mountain massifs influence the circulation of air
currents.
(ii) Surface roughness or friction, owing to the resistance that different
elements of the earth’s surface offer to air circulation affects the nature of
wind. Hills, trees, buildings and similar obstructions impair streamline airflow.
Turbulence results and the wind velocity in a horizontal direction get markedly
reduced. Therefore, wind speed is quite high at seashore.
(iii) Climatic disturbances such as downdraught from thunderclouds and
precipitation, etc., also affect the local winds.
(iv) Wind speed also increase while passing through narrow mountain gaps,
where it gets channeled.

12. NATURE OF WINDS
• The behavior and structure of the wind varies from site to site
depending on the general climate of the region, the physical
geometry of the locality, the surface condition of the terrain
around the site and various other factors.
• Rapid fluctuations in the wind velocity over a wide range of
frequencies and amplitudes, due to turbulence caused by
mechanical mixing of lower layers of atmosphere by surface
roughness are commonly known as gusts.
• The Beaufort scale is an empirical measure that relates wind
speed to observed conditions at sea or on land. Its full name is
the Beaufort wind force scale.

14. Site selection
A suitable site should preferably have some of the following features:
1. No tall obstructions for some distance (about 3 km) in the upwind direction
(i.e. the direction of incoming wind) and also as low a roughness as possible
in the same direction
2. A wide and open view, i.e. open plain, open shoreline or offshore locations
3. Top of smooth well-rounded hill with gentle slopes (about 1:3 or less) on a
flat plain
4. An island in a lake or the sea
5. A narrow, mountain gap through which wind is channeled
6. The site should be reasonably close to power grid
7. The soil conditions must be such that building of foundations of the turbines
and transport of road construction material loaded on heavy trucks must be
feasible
8. If there are already wind turbines in the area, their production results are an
excellent guide to local wind conditions.

15. Impact of tower height
• The rate of change of wind speed with height is called wind shear.
• The lower layers of the air retard those above them, resulting in change in mean
wind speed with height, until the shear forces are reduced to zero. This height is
called the gradient height.
• The layer of air from ground to gradient height is known as planetary
boundary layer
• The planetary boundary layer mainly consists of
• surface layer
• Ekman layer
• In the surface layer the variation of shear stress can be neglected and mean
wind speed with height can be represented
• by Prandtl logarithmic law model: 𝑈𝑧 = 𝑉 𝑙𝑛
𝑧−𝑑
𝑧0
• Where, V is characteristic speed, d is zero plane displacement, its magnitude is
a little less than the height of local obstructions,
• 𝑧0 is roughness length, (𝑧0 + d) is the height of local obstructions.

16. Impact of tower height

17. Estimation of Wind Energy at a Site
• Power in Wind
• If uo is the speed of free wind in unperturbed state, the volume of air
column passing through an area A per unit time is given by Auo.
• If ρ is the density of air, the air mass flow rate, through area A, is given as,
ρAuo.
• Power (Po) available in wind, is equal to kinetic energy rate associated
with the mass of moving air, i.e.: 𝑃0 =
1
2
𝜌𝐴𝑢𝑜 𝑢𝑜
2
• Power (Po) available in wind per unit area:
𝑃𝑜
𝐴
=
1
2
𝜌𝑢𝑜
3

18. Classification of wind turbine
• Wind turbines are broadly classified into two categories.
• Horizontal Axis Wind Turbine (HAWT)
• Vertical Axis Wind Turbine (VAWT).
Wind turbines Characteristics

19. • HAWTs have emerged as
the most successful type
of turbines.
• These are being used. for
commercial energy
generation in many parts
of the world.
• Most commonly, they
have three blades and
operate "upwind," with
the turbine pivoting at the
top of the tower so the
blades face into the wind.

20. • Vertical-axis wind
turbines come in several
varieties, including the
eggbeater-style Darrieus
model, named after its
French inventor.
• These turbines are
omnidirectional, meaning
they don’t need to be
adjusted to point into the
wind to operate.

24. Characteristics of various types of rotors

25. Betz model

26. Vertical Axis Wind Turbine (VAWT)

27. Vertical Axis Wind Turbine (VAWT)

28. Darrieus wind turbine

29. Advantages of Vertical Axis Turbines
(i) it can accept wind from any direction without adjustment, which avoids the
cost and complexity of yaw orientation system,
(ii) gearing and generators, etc., are located at ground level, which simplifies
the design of tower, the installation and subsequent inspection and
maintenance
(iii) also they are less costly as compared to HAWTs.
Disadvantages of Vertical Axis Turbines
(i) many vertical axis machines have suffered from fatigue arising from numerous
natural resonances in the structure,
(ii) rotational torque from the wind varies periodically within each cycle, and thus
unwanted power periodicities appear at the output,
(iii) it normally requires guy ropes attached to the top for support, which
could limit its applications particularly for offshore sites,
(iv) it is noisier than HAWT,
(v) as wind speed increases significantly with height, for the same tower
height HAWT captures more power than VAWT

30. WIND ENERGY CONVERSION SYSTEMS (WECS)

31. WIND ENERGY CONVERSION SYSTEMS (WECS)
DC Generator
Synchronous Generator
Induction Generator
• Based on the generator drive, two schemes
have been developed for the operation
of WECS:
(i) fixed speed drive scheme
(ii) variable speed drive scheme.

32. Wind–Diesel hybrid system

33. combined wind and solar energy system

34. APPLICATION OF WIND ENERGY CONVERSION
SYSTEMS (WECS)
• Pumping Application
• Direct Heating Application
• Electric Generation Application

35. ENVIRONMENTALASPECTS
Main environmental concerns are:
1. Indirect Energy Use and Emissions
2. Bird Life
3. Noise
4. Visual Impact
5. Telecommunication Interference
6. Safety
7. Effects on Ecosystem