1

Energy and Environment

Short Course, Washington University

Wind Basics

Dr. David A. Peters

January 2014

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Dr. David A. Peters

McDonnell Douglas Professor

of Engineering

Dept. of Mechanical Engineering

& Materials Science

Washington University in St. Louis

3

Prerequisite: Differential Equations

Text: Wind Energy Explained, Theory, Design and Application

by J. F. Manwell, Second Edition, J. G. McGowan and

A. L. Rogers, John Wiley & Sons, Ltd, (UK).

Grading: Attendance, reports, quizzes

Contact Information: 935-4337, dap@me.wustl.edu

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Taxonomy and Current Market

Self study: Text (pp. 8-10)

Primarily Horizontal Axis Wind Turbines (HAWT)

Upwind Downwind

Upwind and downwind turbines (p.3)

5

Horizontal Axis Windturbine (HAWT)

Current market ~ almost all are HAWTs

with two or three blades.

Three-blade machines are being slightly

favored. (Number of blades and other

design issues ~ to be treated later.)

Some machines now at 7 MW

(100,000 60-watt light bulbs).

HAWT and its Components

6

(p. 4)

From aerodynamics considerations almost

all towers of current utility HAWTs have a

circular cross section

7

8

9

Nacelle

10

11

National Capacity Growth

The slight drop-off from 2008’s record 8,503 MW was the result of the credit crisis that hit project financing hard

and the devaluation of the production tax credit (i.e., corporations were not making profits and so they had no need

for the tax credits) Project activity picked up after the first half of the one year.

Source: US Department of Energy

Year Net Capacity

Additions

Cumulative

Capacity

1981-1933 240 240

1984-1986 982 1,222

1987-1989 181 1,403

1990-1992 181 1,584

1993-1995 119 1,703

1996 1 1,704

1997 8 1,712

1998 142 1,854

1999 659 2,472

2000 67 2,539

2001 1,692 4,231

2002 456 4,687

2003 1,662 6,349

2004 374 6,723

2005 2,424 9,147

2006 2,427 11,574

2007 5,333 16,907

2008 8,503 25,410

2009 6,988 32,398

2010 7,869 40,267

2011 6,649 46,916

2012 13,091 60,007

12

Ca

pa

city (

MW

)

The slight drop-off from 2008’s record 8,545 MW was the result of

the credit crisis that hit project financing hard and the devaluation of

the production tax credit (i.e., corporations were not making profits

and so they had no need for the tax credits) Project activity picked

up after the first half of the next year.

Private communication: Carl Levesque , AWEA , December 7, 2009

Ca

pa

city (

MW

)

0

10000

20000

30000

40000

50000

60000

70000

Net Capacity Additions

Cumulative Capactiy

13

Insta

lled c

ap

acity [M

W]

0

10000

20000

30000

40000

50000

60000

70000 Cumulative Capacity

Cumulative Capacity

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A time line of Wind Machine Milestones

( Based on Sustainable Energy, Choosing Among Options, J.W. Tester

et al. , MIT press, Cambridge, MA, 2005)

~ 400 Reference to wind-driven Buddhist prayer wheels

1200-1850 Golden age of windmills in western Europe, totaling perhaps 10,000 in England, 18,000 in Germany, 9,000 in Holland, and 50,000 overall

1850-1930 Heyday of the small multi-blade wind machine in the US Midwest—as many as six million units installed

1933 Krasnovsky builds a 100 KW wind machine in the Russian Crimea, near Yalta

1973 The oil energy crisis inspires new interest in alternative energy sources

1974-1980 US Federal Large Wind Turbine Program

1976 US Energy Research and Development Administration (ERDA) small wind machine development program

1981-2009 Wind Turbine Boom-Bust-Green Energy era

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Dutch Windmill

US Farm Windmill

Buddhist Prayer Wheels

16

1981-1993 Wind turbine boom in California: more than 12,000 units installed.

1985,1986 US and California tax credits for wind projects expire, respectively.

1991 First commercial offshore wind farm, Vindeby, Denmark.

1996 Kenetech Windpower (US Windpower), largest US and world manufacturer, declares bankruptcy, [assets sold to Enron Wind, then acquired by GE Wind].

1990-2000 Megawattage of installations in Europe grows at ~20%/year

1998-1999 European manufacturers open wind turbine factories in US and China.

2004 RE-Power (Germany) 5 MW, 126m-dia HAWT (now 7 MW).

2007 US Department of Energy (DOE) announces goal and program to further WT development. (details to follow).

2008-2014 US and European Wind booms.

WORLD WIND POWER CAPACITY GROWTH

17

capacity [

MW

]

Year

18

World’s Energy Resources

(2011)

19

Sun-Sentinel, August 26, 2007

In a recent report, the DOE said the

nation’s wind-power capacity increased by

27 percent in 2006, and that the United

States had the fastest-growing wind-power

capacity in the world in 2005 and 2006. Still,

despite wind farms now operating in 36

states, wind accounts for less than 1

percent of the U.S. power supply.

[Now up to 3.5%.]

20

2008 - 2014

Green Energy Era

WT boom times all over the world Europe, US, India,

China, Australia, New Zealand

In the US, unprecedented federal and state government

support to further WT development (tax credit, research

funding, development grants and loans to industries)

Emergence of WT- technician training programs through

community colleges

By end of 2012, U.S. had 60,000 MW installed power,

which is 3.8% of U.S. total. [Could be 20% by 2030,

25% by 2035, 30% by 2050.]

21

December 14, 2009 (Wall Street Journal)

DOE Outpaces Venture in Cleantech Investments

The federal government through DOE, has taken a large

role in the shaping of the clean energy sector. DOE plans

to either lend or grant more than $40 billion to companies

working on clean technology and, to that end, in the first

nine months of 2009, the agency has allocated $ 13 billion

to business developing everything from electric vehicle

and the batteries that power them, to wind turbines and

solar panels. In comparison, venture capital firms have

invested $ 2.68 million in clean energy technology in the

same period of time.

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COMPARISON OF WIND CAPACITY

WITH MISSOURI POWER PLANTS

Wind: 60,000 Megawatts in U.S.––2012

Present Power Plants in Missouri

Labadie Coal Fired Plant: 2,400 MW

(U.S. wind = 25 Labadies)

Callaway Nuclear Plant: 1,100 MW

(U.S. wind = 55 Callaways)

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COMPARISON OF INSTALLATION

COSTS FOR VARIOUS POWER PLANTS

Coal: $2,500/installed max. KW

Nuclear: $2,000/installed max. KW

Wind: $3,500/installed max. KW

Photo-Voltaic:

$6,000/installed max. KW

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COMPARISON OF POWER GENERATION

COSTS FOR VARIOUS POWER PLANTS

Coal: 4.8 – 5.5 ¢/kw-hr

Nuclear: 11.1 – 14.5 ¢/kw-hr

Wind: 4.0 – 6.0 ¢/kw-hr

Photo-Voltaic: 15.0 – 30.0 ¢/kw-hr

Gas: 3.9 – 4.4 ¢/kw-hr

Geothermal: 4.5 – 30.0 ¢/kw-hr

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Wind Turbine Pioneers

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Palmer Cosslett Putnam

The first to demonstrate the development of large wind

turbines and related applications to electricity grid, some

ten years before the rural electrical program.

Putman collaborated with Morgan Smith Company ( a

water turbine manufacturer in Pennsylvania) and with a

public service company In October 1941, the wind

turbine was installed on a hill of the state in Vermont

(Grandpa’s Knob).

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Smith-Putman WT

53.3 m Rotor Dia

2 Stainless Steel blades with rotor flapping hinges

1.25 MW Rated Power

35.6 m Tower height

Operated for 4 years (1941-1945) and “fed electricity into

the utility grid of central Vermont Public Service Co.”

Generated 1250 kW of electrical power.

1945 rotor blade fracture due to lack of preventive

repair lack of funding, wartime

28

Putman Investigated large diameter (175-225 ft

or 53.3 – 68.5 m) wind turbines ; his results

(1942) are “remarkable when compared with

currently prevailing opinions.”

Text p.16 , last paragraph, “In the United States,

the most significant early large turbine was the

Smith Putman machine , built at Grandpa’s Knob

in Vermont in the late 1930 (1941?)

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“In 1939 the directors of the S. Morgan Smith

Company, manufacturers of hydraulic turbines,

decided to explore the possibilities of large-scale

wind turbines as an additional source of power,

and as a means of diversifying their product. To

harness the power in the wind on a large scale

required a knowledge of the habit of the wind,

about which science had little to say to us. To

enter the field would require basic research.”

(Foreward, Putman Power of the Wind, G. W. Koeppl,

von Nostrand Rheinhold, 1982, Part 1(2nd Edition)) 30

“In six years of design and testing

of the 175-foot, 1250-kilowatt

experimental unit on Grandpa’s Knob

near Rutland Vermont, in winds up to

115 miles per hour, we have satisfied

ourselves that Putman’s ideas are

practical . . .”

31

November, 1946

(Foreword, Ibid)

In 1939, based on 1937 prices

Estimate: (Ten 1500 kW units)

Estimate :$ 190 /kW

Affordable: $125 /kW

Abandoned!

(Putman Power of the Wind, Ibid.)

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33

(see text, p16)

34

U = U (wind velocity)

(details to follow)

U = Assumed uniform, m/s

P = Available Power based on U

An air mass moving toward a HAWT

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(Nm)

(Kg/s)

Power (Nm/s or Watt)

mass

power density

=1

2𝜌 𝑈 3

d( )

Three Wind Speeds

36

(p.51)

=13 m/s)

37

(p.51)

38

Our wind turbine

P, kW

4 15

250

25

U (m/s)

39

An example

4 8

15

24

U (m/s)

12 Hours

4 8

30

24 12 Hours

U (m/s)

Site (A)

Site (B)

40

4 8

15

24

U (m/s)

12 Hours

4 8

30

24 12 Hours

U (m/s)

Site (B)

Our turbine P, kW

4 15

250

25

U (m/s)

Site (A)

41

In one day, our turbine in site A will give

250 x 24 = 6000 kWh

And in site B it will give 0 (zero) units of

energy!

42

43

For later reference

"1/𝜆”

44

45

γ

MODERN ADVANCES

46

47

RE Model (October 2004)

Design

Technical Data

Rated Power 5,000 kW

Cut-in Wind Speed 3.5 m/s

Rated Wind Speed 13 m/s

Cut-Out Wind Speed

Offshore Version 30 m/s

Onshore Version 25 m/s

Rotor/Hub height

Diameter 126 m

Height 120 m

Speed Range, normal

operation

approx. 7-12 rpm

Mass

Rotor approx. 120 t

Nacelle (without rotor) approx. 290 t

48

49

50

Energy Units

51

52

53

U.S. Customary SI (metric)

1 ft.lb (energy) 1.356 J

1 ft. lb/s (power) 4.448 kg.m/s

1 hp 745.7 W

54

A future of considerable promise

(Federal and State incentives)

120 m

Rated rapacity: 50 kW 300 kW 759kW 1000 kW 2000 kW 5000 kW 5000 k W Washington Post- 2010

Rotor diameter: 15m 34 m 48 m 60 m 72 m 112 m 126 m Monument 120 -150 m?

Tower Height: 25 m 40 m 60 m 70m 80 m 100m 120 m 170 m

(Based on Fig. 1.15, p.18)

Dynamic

Power

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𝑅𝑜𝑡𝑜𝑟 𝐶𝑝 ≤ .45

Bearings

𝜂 = .996

Gearbox

𝜂 = .972 Generator

𝜂 = .965

Wind power Mechanical efficinecy (including drive train efficiency)

Frequency

Converter

𝜂 = .975

Harmonic

filters

𝜂 = .983

Transformer

𝜂 = .981

𝜂𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑 ≈ 40%

𝜂 = .934

Grid

Electrical efficinecy

Mechanical – Electrical Conversion Chain Efficiency

(based on “wind turbines” Erich Hau, Springer, 2006)

𝜂 = .94

Examples

56

Power in the wind and power

delivered to an electrical grid

57

58

Power = Power delivered to the grid

COP = overall efficiency

59

If not stated otherwise

≈ 40 %

Cp≤ 45%

Some Aspects of Construction

and Maintenance

60

Transportation of a tower-based

section for the Repower 5 MW Machine

61

Offshore wind turbine with helicopter supply platform in the

Horns Rev wind farm

(Vestas)

62

63

Hub and blade junction at end of turbine nacelle.

Human subject demonstrates size of the device.

Fig 12.6. Image credit: Ellie Weyer.

Appears in F. Vanek & L. Albright (2008), Energy Systems Engineering:

Evaluation & Implementation, p.336. Used with permission.

Access to the turbine nacelle via doorway and stairwell inside the tower

Fig 12.7. Image credit: Ellie Weyer.

Appears in F. Vanek & L. Albright (2008), Energy Systems Engineering:

Evaluation & Implementation, p.336. Used with permission.

65

Some Aspects of Air Density,

Mean Wind at Tower Height

66

(m)

67

68

69

Revisiting Mean Wind Velocity U

70

(p. 39)

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72

HIGH-ALTITUDE TETHERED WIND TURBINES

73

74

Wind speed variation with Height

varies with elevation, time of day, season, nature of

terrain, wind speed, temperature.

(“a highly variable quantity.”, p.46)

(2.36)

p. 46

75

1/7 0.3

5.58 5.85 6.95

P/A (W/m2) 106.4 122.6 205.6

% increase over 10 m 39.0 62.2 168.5

(p. 47) , = 1.225 kg/m3

*

* α = 1/7 is widely used

elevation

76

Example

an appreciable increase.

Tower height (z) is a very important parameter.

Increasing z is not straightforward!

Concluding Remarks on WE

and its Development

77

Sustainable Energy Development

We accept the well-known definition of

Brundtland, Chairman, World Commission of

Environment and Development :

Our Common Future, Oxford University Press,

New York, 1987.

“…development that meets the needs of the

present without compromising the ability of

future generations to meet their own needs.”

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With the current and expected tax credits -- for directly

harnessing wind energy and reducing “greenhouse gas”

emissions -- electrical energy generation through wind

farms is the best candidate in providing at least 25% of

U.S. electricity by 2035.

Remarks :

- Large diameter (> 100 m) wind turbines have been

successfully developed on both offshore and on-land wind

farms (e.g. REpower 5 MW , 126m dia)

- Denmark generated 20% of its electricity by

harnessing wind energy in 2005. By 2012, the percentage

was up to 30%. This percentage has been steadily

increasing.

79

80

Even among the green-energy options, WE is the most deserving

Wind Out of Their Sails Opposition to a project off Cape Cod poses big questions

for offshore wind farms in the U.S.

“For nations such as Denmark, Germany, and the Netherlands, which depend

on wind power to supply an increasingly large fraction of their electricity

demand, the high winds in shallow waters offshore have become an attractive

resource. Indeed, according to the European Wind Energy Association, a trade

group based in Brussels, there is more than 600 megawatts of offshore wind

turbine capacity around Europe, including a 166 MW from off the southern

coast of Denmark.”

“The situation in the United States is quite different. At present, there are no

offshore wind farms and, unlike the sustained European commitment to wind

power, support from federal and state governments is much like the wind itself:

periodic and unreliable. Thanks to the frequently shifting tax and regulatory

environment, wind turbines are generally built in quick bursts. For instance,

2,424 MW of wind power capacity was built in 2005, but only 372 MW the year

before.” Ref. ASME Mechanical Engineering, vol. 128 , No.6 , June 2006

81

82

National Capacity Growth

The slight drop-off from 2008’s record 8,503 MW was the result of the credit crisis that hit project financing hard

and the devaluation of the production tax credit (i.e., corporations were not making profits and so they had no need

for the tax credits) Project activity picked up after the first half of the one year.

Source: US Department of Energy

Year Net Capacity

Additions

Cumulative

Capacity

1981-1933 240 240

1984-1986 982 1,222

1987-1989 181 1,403

1990-1992 181 1,584

1993-1995 119 1,703

1996 1 1,704

1997 8 1,712

1998 142 1,854

1999 659 2,472

2000 67 2,539

2001 1,692 4,231

2002 456 4,687

2003 1,662 6,349

2004 374 6,723

2005 2,424 9,147

2006 2,427 11,574

2007 5,333 16,907

2008 8,503 25,410

2009 6,988 32,398

2010 7,869 40,267

2011 6,649 46,916

2012 13,091 60,007

This wind farm off Nysted in southern Denmark supplies as much as 166

MW of electricity. European countries are planning to add much more

offshore wind capacity in the coming decade.

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Top. Story Dec. 4. 2009

Cape Wind, National Grid to Get to

Work on Power Contract

National Grid and Cape Wind have agreed to enter into negotiations for a long-

term power purchase agreement (PPA) under which the utility would purchase

the electricity generated at Cape Wind's proposed offshore wind energy project

off the coast of Massachusetts. Governor Deval Patrick (D) said this week

The announcement is a major milestone for the high-profile project, which could

be the first offshore wind farm in U.S. Securing a PPA is critical for financing

the proposed wind farm in Nantucket Sound, the governor's office noted.

84

(Sun- Sentinel)

Wash U in St. Louis conducted basic

research on WT since the mid 70’s to 2001

85

Conclusions

By 2035 or 50, wind energy could supply at least 25 % –

30% of the U.S. electrical needs, a feat already

achieved by Denmark.

A much improved exploitation of offshore sites is a must

to achieve this feat.

Wind Farms on land as well as offshore with large wind

turbines (diameter ≥ 125 m) offer considerable promise.

For those turbines, the current predictive capabilities for

modeling turbulence, wake, turbine-to-turbine

interference and dynamic stall merit significant

improvements.

86

ASME Mechanical Engineering

Vol. 132, No 1 January 2010

Engineering to meet electricity needs is

shaping up as a big job, with plenty of

openings.

By Jack Thornton

87

ASME Mechanical Engineering

Vol. 132, No 1 January 2010 Eye-opening statistics were offered by Jeffrey S. Nelson. Head of

the Energy and Infrastructure Future Group at Sandia National

Laboratories in Albuquerque, N.M.:

World energy demand will double between now and 2030. That’s

only 20 years, half the span of an engineering career.

The amount of clean U.S. energy need by 2050 just to stabilize CO2

is 10 trillion watts. This is about ten times the Department of Energy’s

estimate of today’s total installed U.S. generating capacity.

Achieving these numbers will require a broad mix of energy sources,

including renewable, biofuels, and possibly fusion. Nelson said,

pointing out that all of these will require big, costly, and intensive

engineering and scientific programs.

88

ASME Mechanical Engineering

Vol. 132, No 1 January 2010

Another researcher in the power industry, Gary

Golden, senior project manager at the Electric

Power Research Institute, certainly sees

shortage. “ If you crunch all the numbers, the

power industry has about 10 percent of the

engineers we need,”

Nelson and Golden were keynote speakers at the

2009- July ASME Power Conference.

89

This lecture is dedicated to the memory of

Prof. Kurt Hohenemser (1906-2001)

90