AE/ME Wind Engineering Module 1.2 Lakshmi Sankar lsankar@ae.gatech.edu.

AE/ME Wind EngineeringModule 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 Turbineshttp://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 Designshttp://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

Wind Drag Force

Pelton Wheel uses this concept

Use of Lift forces for Torque ProductionUse of Lift forces for Torque Production

L

D

Vwind - Vinduced

LsinDcos

r

Propulsive force = Lsin - Dcos

DΩr

VVL inducedwind

Wind Turbine History in the US• During the 19th century wind mills were

used to pump water.– Rotor diameter reached 20 meters.– Water was used to operate steam

engines,• 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.

– 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 Classificationhttp://www.awea.org/faq/basicwr.html

Wind Power ClassPower density W/m^2 at 0 m height

Wind Speed m/sec (mph)

Power density W/m^2 at 50 m height

Wind Speed m/sec (mph)

1 <100 <4.4 (9.8) <200 <5.6 (12.5)

2 100 - 150 4.4 (9.8)/5.1 (11.5) 200 - 300 5.6 (12.5)/6.4 (14.3)

3 150 - 200 5.1 (11.5)/5.6 (12.5) 300 - 400 6.4 (14.3)/7.0 (15.7)

4 200 - 250 5.6 (12.5)/6.0 (13.4) 400 - 500 7.0 (15.7)/7.5 (16.8)

5 250 - 300 6.0 (13.4)/6.4 (14.3) 500 - 600 7.5 (16.8)/8.0 (17.9)

6 300 - 400 6.4 (14.3)/7.0 (15.7) 600 - 800 8.0 (17.9)/8.8 (19.7)

7 >400 >7.0 (15.7) >800 >8.8 (19.7)

The following slides are from a Presentation in 2002 byAmerican 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 21st Century Technology

Wind Turbines:Power for a House or City

Ready to Become a Significant Power Source

Wind could generate 6% of nation’s electricity by 2020.

Wind currently produces less than 1% of the nation’s power. Source: Energy Information Agency

Wind is Growing Worldwide

0

5000

10000

15000

20000

25000

Rest of World

Europe

United States

Source: AWEA’s Global Market Report

1. Germany: 8754 MW

2. U.S.: 4260 MW

3. Spain: 3195 MW

4. Denmark: 2492 MW

5. India: 1507 MW

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)

4,270 MW as of 07/31/02

Alaska0.9

California1,715.9

Colorado61.2

Hawaii1.6

Iowa324.3

Kansas113.7

Maine0.1

New Hampshire0.1

Massachusetts1.0

Michigan2.4

Minnesota322.7

Montana0.1

Nebraska3.5

New Mexico1.3

New York48.2

North Dakota

1.3Oregon156.9

Pennsylvania34.5

Tennessee2.0

Texas1,095.5

Utah0.2

Vermont6.0

Wisconsin53.0

Wyoming140.6

Washington180.2

South Dakota

2.9

Source: AWEA’s U.S. Projects Database

1,697 MW added in 2001

Kansas112

Wisconsin30

Pennsylvania24

New York30Oregon

132

Washington180

Iowa82

Minnesota218

Texas915

Main Areas of Growth in 2001

Source: AWEA’s U.S. Projects Database

U.S. Wind Power Capacity Growth

*Source: AWEA’s U.S. Projects Database

Wind Power Economics

$0.00

$0.10

$0.20

$0.30

$0.40

1980 1984 1988 1991 1995 2000 2005

38 cents/kWh

Cost Nosedive Driving Wind’s Success

2.5-3.5 cents/kWh

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

59.6

80

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

Turbines, FOB USA49%

Construction22%

Towers (tubular steel)

10%

Interest During Construction

4%

Interconnect/Subsation

4%

Land Transportation

2%Development

Activity4%

Design & Engineering

2%

Financing & Legal Fees3%

Technology Improvements Leads to Better Reliability

• Drastic improvements since mid-80’s

• Manufacturers report availability data of over 95%

1981 '83 '85 '90 '98

% A

vail

able

Year0

20

40

60

80

100

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

Total Cost $65 $165 $300 $580 $730 $1300

Cost/kw $2,600 $1,650 $1,333 $1,050 $950 $790

Capacity Factor

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

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 PowerEnvironmental

• 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

Source: Northwest Foundation, 12/97

23%

28%

33%

34%

70%

0% 20% 40% 60% 80%

Toxic Heavy Metals

Particulate Matter

Nitrous Oxides

Carbon Dioxide

Sulfur Dioxide

Percentage of U.S. Emissions

Benefits of Wind PowerEconomic Development

• Expanding Wind Power development brings jobs to rural communities

• Increased tax revenue • Purchase of goods &

services

Benefits of Wind PowerEconomic 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 PowerFuel Diversity

• Domestic energy source

• Inexhaustible supply• Small, dispersed

design reduces supply risk

Benefits of Wind PowerCost Stability

• Flat-rate pricing can offer hedge against fuel price volatility risk

• Electricity is inflation-proof

Wind Project Siting

Siting a Wind Farm• Winds

– 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)

Density = P/(RxT) P - pressure (Pa) R - specific gas constant (287 J/kgK) T - air temperature (K)

= 1/2 x air density x swept rotor area x (wind speed)3

A V3

Area = r2 Instantaneous Speed(not mean speed)

kg/m3 m2 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 IssuesTransmission 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 IssuesTransmission 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 @$4 natural gas

West 2,254 2,750 35,000 200,000

Midwest 900 500 400 350,000

East 90 330 500 7,000

Texas 1,016 300 --- 40,000

South 2 20 100 600

Total 4,262 4,000 36,000 600,000

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