Wind Power Fundamentals

Wind Power Fundamentals

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Description: Wind Power Wind Power Fundamentals:- Origin of Wind:Wind Atmospheric air in motion 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. Efficiency in Extracting Wind Power:- Betz Limit & Power Coefficient: Power Coefficient, Cp, is the ratio of power extracted by the turbine to the total contained in the wind resource Cp = P to the total contained in the wind resource Cp=PT/PW.

 
Author: Alex Kalmikov, Katherine Dykes, Kathy Araujo (Fellow) | Visits: 894 | Page Views: 1472
Domain:  Green Tech Category: Wind/Water/Geo 
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Contents:
Wind Power
Fundamentals
Presented by:
Alex Kalmikov and Katherine Dykes
With contributions from:
Kathy Araujo
PhD Candidates, MIT Mechanical
Engineering, Engineering Systems and
Urban Pl
U b Planning
i
MIT Wind Energy Group &
Renewable Energy Projects in Action
Email: wind@mit.edu

Overview
History of Wind Power
Wind Physics Basics
Wind Power Fundamentals
Technology Overview
Beyond the Science and Technology
What’s underway @ MIT

Wind Power in History …

Brief History – Early Systems
Harvesting wind power isn’t exactly a new
idea – sailing ships, wind-mills, wind-pumps
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
– P t Mill I t d
Post
Introduced i N th
d in Northern E
Europe
– Horizontal-Axis Wind-Mill: sails connected to a
horizontal shaft on a tower encasing gears and axles
for translating horizontal into rotational motion

Wind in 19th century US
– Wind-rose horizontal-axis water-pumping wind-mills
g
found throughout rural America
Torrey, Volta (1976) Wind-Catchers: American Windmills of Yesterday and Tomorrow. Stephen Green Press, Vermont.
Righter, Robert (1996) Wind Energy in America. University of Oklahoma Press, Oklahoma.

Brief History - Rise of Wind Powered Electricity
1888: Charles Brush builds first large-size wind
yg
(17
electricity generation turbine ( 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: Propeller-type 2 & 3-blade
1920s 1950s: P
ll t
3 bl d
horizontal-axis wind electricity conversion
systems (WECS)

1940s – 1960s: Rural Electrification in US and
Europe leads to decline in WECS use

Torrey, Volta (1976) Wind-Catchers: American Windmills of Yesterday and Tomorrow. Stephen Green Press, Vermont.
Righter, Robert (1996) Wind Energy in America. University of Oklahoma Press, Oklahoma.

Brief History –

Modern Era

Key attributes of this period:





Scale increase
Commercialization
Competitiveness
Grid integration

Catalyst for progress: OPEC Crisis (1970s)
• Economics
• Energy independence
• Environmental benefits

Turbine Standardization:
3-blade Upwind
Horizontal-Axis
on a monopole tower

Source for Graphic: Steve Connors, MIT Energy Initiative

Wind Physics Basics …

Origin of Wind
Wind – Atmospheric air
in motion
Energy source
Solar radiation differentially
absorbed b earth surface
b b d by
th
f
converted through convective
processes due to temperature
differences to air motion
Spatial Scales
p
Planetary scale: global circulation
Synoptic scale: weather systems
Meso scale: l
M
l local t
l topographic or
hi
thermally induced circulations
Micro scale: urban topography

Source for Graphic: NASA / GSFC

Wind types
• Planetary circulations:
– Jet stream
– Trade winds
– Polar jets
• Geostrophic winds
• Thermal winds
• Gradient winds









Katabatic / Anabatic winds – topographic winds
Bora / Foehn / Chinook – downslope wind storms
Sea Breeze / Land Breeze
Convective storms / Downdrafts
Hurricanes/ Typhoons
Tornadoes
Gusts / Dust devils / Microbursts
Nocturnal Jets

• Atmospheric Waves

Wind Resource Availability and Variability

Source: Steve Connors, MIT Energy Initiative

Source for Wind Map Graphics: AWS Truewind and 3Tier

Fundamentals of Wind Power …
Wind Power Fundamentals …

Fundamental Equation of Wind Power

– Wi d P
Wind Power d
depends on:
d
• amount of air (volume)
• speed of air (velocity)
• mass of air (density)
flowing through the area of interest (flux)

A
v

– Kinetic Energy definition:
• KE = ½ * m * v 2

&
m=

– Power is KE per unit time:

&
• P = ½ * m * v2

dm
mass flux
dt
d

– Fluid mechanics gives mass flow rate
(density * volume flux):
• dm/dt = ρ* A * v
– Thus:
• P = ½ * ρ * A * v3

• Power ~ cube of velocity
• Power ~ air density
• Power ~ rotor swept area A= πr 2

Efficiency in Extracting Wind Power
Betz Limit & Power Coefficient:
• Power Coefficient, Cp, is the ratio of power extracted by the turbine
to the total contained in the wind resource Cp = PT/PW
• Turbine power output
PT = ½ * ρ * A * v 3 * Cp
• The Betz Limit is the maximal possible Cp = 16/27
• 59% efficiency is the BEST a conventional wind turbine can do in
extracting power from the wind

Power Curve of Wind Turbine
Capacity Factor (CF):
• The fraction of the year the turbine generator is operating at
rated (peak) power
Capacity Factor = Average Output / Peak Output ≈ 30%

• CF is based on both the characteristics of the turbine and the
site characteristics (typically 0.3 or above for a good site)
Power Curve of 1500 kW Turbine

Wind Frequency Distribution
0.12
0.1
0.08
0.06
0.04
0.02
0
<