AE/ME Wind Engineering
Module 1.2
Lakshmi Sankar
lsankar@ae.gatech.edu
OVERVIEW
• In the previous module 1.1, you leaned about
the course objectives, topics to be covered, and
the deliverables (assignments)
• In this module, we will first review the history of
the wind turbines
• We will also learn some basic terminology
associated with wind turbines
• We will also discuss what factors go into
choosing sites where you may build/deploy your
own wind turbines or farms.
– We will conduct this discussion through case studies.
History of Wind Turbines
http://www1.eere.energy.gov/windandhydro/wind_history.html
• Technology is old, in some respects!
– Wind was used to propel sail boats as early as 5000
BC in Egypt.
– Chinese used wind energy to pump water by as early
as 200 BC
– Persians used wind energy about the same time to
grid grain
• By the 11th century, people in the middle east
were using wind mills for food production
• Traders and crusaders carried the ideas to
Europe.
History of Wind Turbines
(Continued..)
• Dutch were looking for ways of draining lakes and marshes.
– Wind turbines became very popular.
• The technology spread to US when settler brought these ideas to
America.
• Industrialization (use of coal to generate steam) brought a decline in
the use of wind energy.
• Steam engines replaced wind mills for pumping water and producing
electricity.
• Rural electrification began in the 1930s.
• Wind turbines had to make their case economically!
– Their popularity rose and fell with the availability and cost of alternative
forms of energy production.
– Oil crisis in the 1970s and energy crisis during the past decade has
brought wind energy’s potential as a clean, renewable, sustainable,
energy source,
Wind Power's Beginnings
(1000 B.C. - 1300 A.D.)
• Persians used the drag of
the blades (i.e.
aerodynamic force along
the direction of the wind)
to generate rotation of the
blades.
• Struts connected the sails
to central shaft.
– Grinding stone was
attached to the central
shaft.
• Only one half of the
turbine was useful at any
instance in time.
Early Designs
http://www.telosnet.com/wind/early.html
Lift vs Drag
• The aerodynamic force along the direction of the
wind is called drag
– Early wind turbines used drag to generate the torque.
• The aerodynamic force normal to the wind
direction is called lift.
– For a properly designed blade (or airfoil) lfit to drag
ratio may be 100 to 1!
• Dutch began using lift force rather than drag to
turn the rotor.
• Over the past 500 years, the design has evolved
through analysis and experimentation.
Use of Drag to Produce Torque
Pelton Wheel uses this
concept
Wind
Drag Force
Use of Lift forces for Torque Production
L
D
Lsinf
Wr
f
Dcosf
Vwind - Vinduced
Propulsive force = Lsinf - Dcosf
 V induced 
V
 L  wind
D

Ωr


Wind Turbine History in the US
•
During the 19th century wind mills were
used to pump water.
–
–
•
Eray designs used wood as the
material and had a paddle like shapes.
–
•
–
•
Drag force was used.
Later designs used steal blades which
could be shaped to produce lift forces.
–
•
Rotor diameter reached 20 meters.
Water was used to operate steam
engines,
The blades spun fast, requiring gears
to reduce the angular velocity.
Mechanisms were developed for
folding blades in case of high winds.
In 1888, electricity was produced using
the wind turbine shown on the lower
right by Charles F. Brush.
By 1910s, coal and oil fired steam
plants became popular, and the use of
wind turbines became less common.
Installed Wind Power Generation (in MW)
http://www.windenergyinstitute.com/installed.html
Rank County
2005
2006
2007
1
Germany
18,415
20,622
22,247
2
United States
9,149
11,603
16,818
3
Spain
10,028
11,615
15,145
4
India
4,430
6,270
8,000
5
China
1,260
2,604
6,050
6
Denmark (& Faeroe Islands)
3,136
3,140
3,129
7
Italy
1,718
2,123
2,726
8
France
757
1,567
2,454
9
United Kingdom
1,332
1,963
2,389
10
Portugal
1,022
1,716
2,150
11
Canada
683
1,459
1,856
12
Netherlands
1,219
1,560
1,747
Basic Terminology
• Vertical Axis (or
Darrieus) Wind
Turbines vs.
Horizontal Axis Wind
Turbines
– We will study HAWTs
in this course.
Terminology (Continued)
http://www.energybible.com/wind_energy/glossary.html
• Availability Factor
– The percentage of time that a wind turbine is able to
operate and is not out commission due to
maintenance or repairs.
• Capacity Factor
– A measure of the productivity of a wind turbine,
calculated by the amount of power that a wind turbine
produces over a set period of time, divided by the
amount of power that would have been produced if
the turbine had been running at full capacity during
that same time interval.
Terminology (Continued)
• Rotor
– Comprises the spinning parts of a wind turbine, including the turbine
blades and the hub.
• Hub
– The central part of the wind turbine, which supports the turbine blades
on the outside and connects to the low-speed rotor shaft inside the
nacelle.
• Root Cutout
– The percentage of the rotor blade radius that is cut out in the middle of
the rotor disk to make room for the hub and the arms that attach the
blades to the shaft.
• Nacelle
– The structure at the top of the wind turbine tower just behind (or in some
cases, in front of) the wind turbine blades that houses the key
components of the wind turbine, including the rotor shaft, gearbox, and
generator.
Parts of a Wind Turbine
• Turbine controller
is connected to the
rotor.
• Converter
controller,
connected to
converters and
main circuit
breaker, is needed
to control the
output voltage and
power
Wind Power Classification
http://www.awea.org/faq/basicwr.html
Wind Power Class
Wind Speed m/sec
(mph)
Power
density
W/m^2 at
50 m
Wind Speed
height
m/sec (mph)
1 <100
<4.4 (9.8)
<200
2 100 - 150
4.4 (9.8)/5.1 (11.5)
5.6 (12.5)/6.4
200 - 300 (14.3)
5.1 (11.5)/5.6 (12.5)
6.4 (14.3)/7.0
300 - 400 (15.7)
5.6 (12.5)/6.0 (13.4)
7.0 (15.7)/7.5
400 - 500 (16.8)
5 250 - 300
6.0 (13.4)/6.4 (14.3)
7.5 (16.8)/8.0
500 - 600 (17.9)
6 300 - 400
6.4 (14.3)/7.0 (15.7)
8.0 (17.9)/8.8
600 - 800 (19.7)
7 >400
>7.0 (15.7)
>800
Power density W/m^2 at 0 m
height
3 150 - 200
4 200 - 250
<5.6 (12.5)
>8.8 (19.7)
The following slides are from a
Presentation in 2002 by
American Wind Energy
Association
Wind Power is Ready
Clean Energy
Technology for Our
Economy and
Environment
American Wind Energy Association, 2002
Image courtesy of NEG Micon
Wind Power Market
Overview
Ancient Resource Meets
Century Technology
st
21
Wind Turbines:
Power for a House or City
Ready to Become a Significant
Power Source
coal
coal
petroleum
petroleum
natural gas
natural gas
nuclear
nuclear
hydro
hydro
other renewables
other renewables
wind
wind
Wind currently produces less than
1% of the nation’s power.
Source: Energy Information Agency
Wind could
generate
6% of
nation’s
electricity
by 2020.
Wind is Growing Worldwide
United States
5000
00
20
97
19
94
19
91
19
88
0
19
5. India: 1507 MW
Europe
10000
85
4. Denmark: 2492 MW
Rest of World
15000
19
3. Spain: 3195 MW
20000
82
2. U.S.: 4260 MW
25000
19
1. Germany: 8754 MW
Source: AWEA’s Global Market Report
Wind Taking Off in the U.S.
•
•
•
•
U.S. installed nearly 1,700 MW in 2001
Wind power capacity grew by 66%
Over 4,265 MW now installed
Expecting over 2,500 of new capacity in
2002-2003 combined
Source: AWEA’s U.S. Projects Database
United States Wind Power Capacity (MW)
Washington
180.2
Montana
0.1
Oregon
156.9
Wyoming
140.6
North
Dakota
1.3
South
Dakota
2.9
Nebraska
3.5
Utah
0.2
Colorado
61.2
Minnesota
322.7
Michigan
2.4
Massachusetts
1.0
New York
48.2
Iowa
324.3
Pennsylvania
34.5
Tennessee
2.0
New Mexico
1.3
Source:
AWEA’s
U.S.
Projects
Database
Texas
1,095.5
Alaska
0.9
Hawaii
1.6
Maine
0.1
Vermont
6.0
Wisconsin
53.0
Kansas
113.7
California
1,715.9
New Hampshire
0.1
4,270 MW as of 07/31/02
Washington
180
Wisconsin
30
New York
Minnesota
30
218
Oregon
132
Main
Areas of
Growth in
2001
Iowa
82
Pennsylvania
24
Kansas
112
1,697 MW added in 2001
Texas
915
Source: AWEA’s U.S. Projects
Database
U.S. Wind Power Capacity Growth
*Source: AWEA’s U.S.
Projects Database
Wind Power Economics
Cost Nosedive Driving Wind’s
Success
38 cents/kWh
$0.40
$0.30
$0.20
2.5-3.5 cents/kWh
$0.10
$0.00
1980
1984
1988
1991
1995
2000
2005
Levelized cost at excellent wind sites in nominal dollars, not
including tax credit
Wind Power Cost of Energy
Components
Cost (¢/kWh) = (Capital Recovery Cost + O&M) /
kWh/year
– Capital Recovery = Debt and Equity Cost
– O&M Cost = Turbine design, operating
environment
– kWh/year = Wind Resource
Capital Costs
• Revenue Streams
– Commodity Power Sale: $30-$45/MWh
– Production Tax Credit: $18/MWh
– “Green Credit”: New Market, Values Vary
• Debt/equity ratios close to 50%/50%
– Increased debt/equity ratios can significantly
increase return
Long-Term Debt
• Better loan terms with longer-term
power purchase agreement (PPA)
• Loan terms up to 22 years, determined
largely by PPA
Equity Considerations
• Return requirements vary with risk
– Perceived risk of wind projects may be larger than
real risk
• Returns evaluated after tax credit
– Wind energy projects can expect return in low
teens (10% to 15%)
Turbine Technology Constantly
Improving
•
•
•
•
Larger turbines
Specialized blade design
Power electronics
Computer modeling produces more efficient
design
• Manufacturing improvements
How big is a
2.0 MW wind
turbine?
This picture shows a
Vestas V-80 2.0-MW
wind turbine
superimposed on a
Boeing 747 JUMBO JET
Construction Cost Elements
Financing & Legal
Fees
3%
Development
Activity
4%
Interconnect/
Subsation
4%
Interest During
Construction
4%
Towers
(tubular steel)
10%
Construction
22%
Design &
Engineering
2%
Land
Transportation
2%
Turbines, FOB
USA
49%
Technology Improvements
Leads to Better Reliability
100
% Available
• Drastic
improvements
since mid-80’s
• Manufacturers
report availability
data of over 95%
80
60
40
20
0
1981
'83
'85
'90
'98 Year
Improved Capacity Factor
• Capacity Factors Above
35% at Good Wind
Sites
– Performance
Improvements due to:
– Better siting
– Larger turbines/energy
capture
– Technology Advances
– Higher reliability
Examples: Project
Performance (Year 2000)
Big Spring, Texas
•37% CF in first 9 months
Springview, Nebraska
•36% CF in first 9 months
Bottom Line
20 Years of Wind Technology Development
1981
1985
1990
1996
1999
2000
Rotor (Meter)
10
17
27
40
50
71
KW
25
100
225
550
750
1650
$65
$165
$300
$580
$730
$1300
$2,600
$1,650
$1,333
$1,050
$950
$790
21%
25%
28%
31%
33%
39%
MWh produced
over 15 years
675
3300
8250
22,200
33,000
84,000
Amortized cost
of turbine per
unit of energy
9.6
5
3.6
2.6
2.2
1.5
Total Cost
Cost/kw
Capacity
Factor
Economy of
scale reduces
price per kw of
capacity
Technology
improvements
yield more energy
bang for the buck
Combined, they
dramatically reduce
turbine price per unit
of energy produced
Benefits of Wind Power
Advantages of Wind Power
• Environmental
• Resource Diversity &
Conservation
• Cost Stability
• Economic Development
Benefits of Wind Power
Environmental
•
•
•
•
No air pollution
No greenhouse gasses
Does not pollute water with mercury
No water needed for operations
Electricity Production is Primary
Source of Industrial Air Pollution
Sulfur Dioxide
70%
Carbon Dioxide
34%
Nitrous Oxides
33%
Particulate Matter
28%
Toxic Heavy Metals
23%
0%
20%
40%
60%
Percentage of U.S. Emissions
Source: Northwest Foundation, 12/97
80%
Benefits of Wind Power
Economic Development
• Expanding Wind Power
development brings jobs to
rural communities
• Increased tax revenue
• Purchase of goods &
services
Benefits of Wind Power
Economic Development
Case Study: Lake Benton, MN
$2,000 per 750-kW turbine
in revenue to farmers
Up to 150 construction, 28
ongoing O&M jobs
Added $700,000 to local tax
base
Benefits of Wind Power
Fuel Diversity
• Domestic energy
source
• Inexhaustible supply
• Small, dispersed
design reduces
supply risk
Benefits of Wind Power
Cost Stability
• Flat-rate pricing can
offer hedge against
fuel price volatility
risk
• Electricity is
inflation-proof
Wind Project Siting
• Winds
Siting a Wind Farm
– Minimum class 4 desired for utility-scale wind farm (>7 m/s
at hub height)
• Transmission
– Distance, voltage excess capacity
• Permit approval
– Land-use compatibility
– Public acceptance
– Visual, noise, and bird impacts are biggest concern
• Land area
– Economies of scale in construction
– Number of landowners
Power in the Wind
(W/m2)
= 1/2 x air density x swept rotor area x (wind speed)3
A
V3

Density = P/(RxT)
P - pressure (Pa)
R - specific gas constant (287 J/kgK)
T - air temperature (K)
kg/m3
Area =  r2
m2
Instantaneous Speed
(not mean speed)
m/s
Perceived Market Barriers
• Siting
– Avian
– Noise
– Aesthetics
• Intermittent Fuel
Source
Actual Market Barriers
• Transmission constraints
• Financing
• Operational characteristics different from
conventional fuel sources
Wind Characteristics Relevant
to Transmission System
•
•
•
•
•
Intermittent output
Generally remote location
Small project size
Short/flexible development time
Low capacity factor
Wind Development Issues
Transmission Grid Operating Rules
• What wind wants:
–
–
–
–
–
Liquid, transparent spot market for imbalance settlements
Near real time, flexible scheduling protocols
Robust secondary markets in transmission rights (“flexible firm”)
Postage stamp pricing allocated to load (or volumetric pricing)
Statistical determination of conformance to load shape to set value
• What wind gets:
– System designed exclusively to transport firm, fixed
blocks/commodity strips
– Rigid advance scheduling protocols/onerous imbalance charges
– License plate pricing allocated to incremental generation
– Grid balkanization/rate pancaking
Wind Development Issues
Transmission Expansion
• What wind wants:
– Pro-active regional planning with political buy-in.
– Programmatic expansion focused on shared goals.
– Public infrastructure financing repaid through user fees.
• What wind gets:
– Reactive, piecemeal gridlock decoupled from political process.
– Project specific expansion focused on immediate needs of existing
players.
– Uncertain capacity rights as sole rate recovery mechanism.
Consequences of Wind
Characteristics
• Remote location and low capacity factor = higher
transmission investment per unit output
• Small project size and quick development time =
planning mismatch with transmission investment
• Intermittent output can = higher system operating
costs if systems/protocols not designed properly
Federal and State Policies to
Promote Wind Power
Production Tax Credit
• Lowers price of electricity to make it
more accessible to customers
• Currently provides credit of 1.8¢ per
kWh
• Industry needs long-term extension to
encourage investment
Renewable Portfolio Standard
• Requirement that U.S. suppliers get 10% of
supply from renewable sources by 2020
• Texas example shows how RPS can enable
green power markets to flourish by creating a
supply of reasonably-priced renewable
energy
• Can create incentives to solve transmission
issues
Standard Market Design &
Interconnection
• Wind is “square peg in a round hole”
– Intermittent
– Site-specific, often rural
– Small, with short construction lead time
• SMD & Interconnection NOPRs designed to
make markets more efficient, which could
make a big difference in cost and availability
of wind power
Clean Air Act
• Expect to see amendment to the Clean Air
Act before 2004 elections
• Without set-asides or direct allocation for
renewables, would strip wind projects of
ability to claim emissions reductions
• Output based compliance that includes NOx,
SO2 and CO2 could add revenue stream of
0.4 - 0.5 cents per kWh
Small Turbine Incentives
• 30% Investment
Tax Credit
• Net metering
State Incentives
•
•
•
•
State renewable portfolio standards
Public Benefits Funds
Electricity source disclosure
Government procurement
Green Power Market
Green Power Market
• Places a monetary value on environmental
benefits
• Raises visibility of renewable power &
promotes customer awareness
• Usually small scale, short-term contracts
Premium prices
Different Ways to Buy
• Green Pricing
– Regulated utility offers customers choice to
support wind power construction
• Green Marketing
– In competitive market, customers empowered to
choose service providers that contract to purchase
renewables
• Green Tags
– environmental attributes divorced from energy
Competitive Green Market
• Has encouraged about 25 MW in CA & PA
to date
• Will encourage more than 75 MW in PA in
next two years
Green Pricing
• Has encouraged over 15 new wind
projects to serve green pricing market
• Smaller projects
• Spread throughout the U.S. – raises
visibility of wind power
Small Wind Turbine Market
Development
Programs for small wind
development
• Buy-down programs
• Exemptions from sales, property tax
• Standardized zoning requirements
Buy-down programs
• CA renewables fund refunds 50% of the cost
of a renewable system
– CA sales account for over half of the small wind
turbine market
• MA buy-down program refunds 10% capped
at $100
– does not appreciably affect the market
Property / Sales Tax
• Property or sales tax exemption offered in
several states
• Programs to affect initial purchase price work
best
• Net metering programs (equalizing kWh costs
paid and received by residential generators)
do not seem to drive purchasing decisions
Future Trends in
Wind Power
Expectiations for Future Growth
• 2,500 MW new added by end of 2003
• 20,000 total installed by 2010
• 6% of electricity supply by 2020
= 100,000 MW of wind power
installed by 2020
Wind Energy
“U.S. Proven & Probable Reserves”
Nameplate MW
Region
On-Line
In
Development
Developable in
Reserve
@$2 natural gas
West
@$4 natural gas
2,254
2,750
35,000
200,000
900
500
400
350,000
90
330
500
7,000
Texas
1,016
300
---
40,000
South
2
20
100
600
4,262
4,000
36,000
600,000
Midwest
East
Total
Future Cost Reductions
• Financing Strategies
• Manufacturing Economy of Scale
• Better Sites and “Tuning” Turbines for
Site Conditions
• Technology Improvements
Future Technology
Developments
• Application Specific Turbines
– Offshore
– Limited land/resource areas
– Transportation or construction
limitations
– Low wind resource
– Cold climates
®Middelgruden.dk
www.AWEA.org
Windmail@awea.org
American Wind Energy Association
122 C St, NW, Suite 380
Washington, DC 20001