- VANITA N. THAKKAR
MECHANICAL ENGINEERING DEPARTMENT,
BABARIA INSTITUTE OF TECHNOLOGY,
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• Wind energy is a large
• Global wind power
potential : about
11,000 GW (about 5
times the global
• In India :
• gross potential :
• technical potential
: 2,8375 MW. Distribution of wind power potential in
India (wind power density in W/m2.)
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India : 5th in the world based on the installed
wind power capacity,
India produces : about 2 billion kWh per year
from wind with the average utilization factor of
1175 hours per year.
Cost of energy from wind is about Rs.4 to 5 per
kWh in India.
India has also started exporting 1 MW capacity
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Wind is an indirect solar energy source.
Its characteristics :
◦ It is environmentally clean source of
◦ It is a dilute source of energy.
◦ It is perennially available.
◦ Its availability is unpredictable.
◦ Data are available about its availability
pattern around the day for different
months of the year.
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The machine that converts kinetic energy in
the wind into usable form of mechanical
energy (usually shaft power).
Wind machines are typically used for
mechanical applications like water pumping,
grinding, woodcutting, or for AC or DC
power generation in grid connected or
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Study of wind machines is called Molinology.
It cuts across various fields including:
◦ Machine Design,
◦ Structural Design,
◦ Materials Technology,
◦ Power Engineering,
◦ Reliability Engineering,
◦ Instrumentation and Controls Engineering.
Three bladed propeller deign has evolved as the
commercial Wind Energy Conversion System
today. Designs of 225 kW, 450 kW, 650 kW or 1
MW are installed commercially in India.
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Design and performance details of a typical 1 MW
unit installed by Suzlon :
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Power developed by the wind machine
is mainly affected by :
◦ wind speed, u,
◦ area swept by the rotor, AS,
◦ density of air, ρ,
◦ rotational speed of the machine, Ω,
◦ radius of the rotor, R,
◦ number of blades, B
◦ total blade area.
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Power developed is also affected by :
Lift and drag characteristics of the blade
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By Dimensional Analysis parameters for
characterizing wind machines are identified :
Coefficient of Performance, CP = P / (½ ρ AS u3)
P = Power output at rotor shaft (W)
AS = Area swept by the machine (m2)
ρ = Air density (kg/m3)
u = Undisturbed wind speed (m/s)
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Tip speed ratio, λ = R Ω / u
R = Rotor radius (m),
Ω = rotational speed of the rotor
Solidity, σ = blade area / AS
= (average chord x blade length
x number of blades) / AS
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Effect of solidity (range 0.03 to 1) :
• Torque increases as solidity increases
• Wake in the downwind flow increases as
• Maximum power decreases as wake increases
Hence, maximum power decreases as solidity
Effect of tip speed ratio :
Tip speed ratio increases as solidity decreases
Maximum power increases as tip speed ratio
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Wind machines can be broadly classified
according to the axis of mounting into
Horizontal Axis Wind Machines and Vertical
Axis Wind Machines.
Majority of the machines built in the modern
wind energy applications are horizontal axis