Renewable energy can be obtained from natural flows of energy like sunlight and wind. Wind energy is extracted from kinetic wind power using wind turbines. Most common wind turbines are horizontal axis wind turbines (HAWT) that have three blades attached to a central hub to capture the energy of the wind and power an electrical generator. HAWTs are the most widespread in use today. Vertical axis wind turbines (VAWT) also exist but are less common as they do not take advantage of higher wind speeds at higher elevations like HAWTs.

2. RENEWABLE ENERGY
DEFINATION:
Energy obtained from natural and persistent flows
of energy occurring in the immediate environment
Such energy may also be called Green Energy or
Sustainable Energy.
EXAMPLE:
• Solar energy.
• Wind energy.

3. The Wind Energy Resource
 The wind is an abundant, free, clean,
sustainable and environmentally-friendly
renewable energy source. It has served the
human civilization for many centuries by
propelling ships and driving windmills to grind
grain and pump water, and nowadays also for
electrical power production (Johnson, 2006).
 Wind energy is extracted from kinetic wind
power.

4. History of Wind Uses
Wind as source of energy has been in use by
humans for many centuries
Following are the ways :
 About 5000 years ago used by Egyptians
as sailing ships and boats .
 The first windmill machines were also used
around 2000 years B.C., in ancient Babylon
and China,

5. WIND TURBINE
Most wind turbines (WT) are machines built to convert the
containing power in the wind into electricity.
 Classification according to interaction of their blades with the
wind by :
Aerodynamic forces
1. Drag force
2. Lift force
3. Combination of Drag force and lift force
 Classification according to orientation of rotor:
• Horizontal Axis
Wind Turbine(HAWT)
• Vertical Axis
Wind Turbine (VAWT)

6. HAWT’s with three blades attached to a central hub as it is the
most widespread in the wind power industry and in use today. The
blades and the hub form the rotor (the main element to capture
energy), which are connected to an electrical generator. When the
wind blows, the rotor turns and the generator produces alternating
current (AC) electricity.
HORIZONTAL AXIS WIND
TURBINE

28. VERTICAL AXIS WIND TURBINE

30.  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

31.  The lift blade design employs the same
principle that enables airplanes, kites and
birds to fly. The blade is essentially an
airfoil, or wing. When air flows past the
blade, a wind speed and pressure
differential is created between the upper
and lower blade surfaces. The pressure at
the lower surface is greater and thus acts
to "lift" the blade. When blades are
attached to a central axis, like a wind
turbine rotor, the lift is translated into
rotational motion. Lift-powered wind
turbines have much higher rotational
speeds than drag types and therefore are
well suited for electricity generation.

32.  For the drag design, the wind
literally pushes the blades out
of the way. Drag powered wind
turbines are characterized by
slower rotational speeds and
high torque capabilities. They
are useful for the pumping,
sawing or grinding work that
Dutch, farm and similar "work-
horse" windmills perform. For
example, a farm-type windmill
must develop high torque at
start-up in order to pump, or lift,
water from a deep well.

33.  Cup Anemometer
 Savonius Rotor
 Darrieus Rotor
 Musgrove Rotor
 Evans Rotor

34.  The dominant force is Drag force in cup
anemometer. There is linear relationship
between rotor and wind.

35.  The driving force is principally Drag .
 There are two or three curved sheets.
 Large solidity large torque.

36.  The driving force is principally Lift force.
 It consist two or three thin curved blades.
 Stress on blades alomg there length


37.  The driving force is principally Lift force .
 The blades are vertical for normal power
generation.

38.  The driving force is principally Lift force .
 In this rotor also blades are in curved form.

42.  The property called “solidity” is important in turbine (and
compressor) design.
 Solidity is defined as the fraction of the swept area that
is occupied by a working blade.
 A farmers windmill is a high-solidity device, while a
single blade rotor, illustrated earlier, is a low solidity
device.
 An efficient turbine must interact with as much of the
wind passing through the swept area as possible.
 As the solidity decreases, the rotor speed must increase
for this to happen.
 Therefore, as the number of blades decrease, the required
speed for maximum efficiency must increase.

43.  The generator and gearbox can be placed
on the ground
 The structure is usually simpler.
 You do not need a yaw (pointing)
mechanism to turn the rotor against the
wind.
 These are easier for hobbyists to build – little
detailed knowledge of aerodynamics is
needed for simple designs.

44.  These structures are low to the ground, where wind
speeds are lowest.
 The overall efficiency is much lower than horizontal
axis machines.
 Most vertical axis machines are not self starting.
 Many vertical axis machines require guy wires
which greatly increase the structural footprint.
 Maintenance is usually more difficult.
 For example, replacement of the generator typically
requires disassembly of the entire machine.