Dr Jehad Yamin

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1 A.D. ◦ Hero of Alexandria uses a wind machine to power an organ

~ 400 A.D. ◦ Wind driven Buddhist prayer wheels

1200 to 1850 ◦ Golden era of windmills in western Europe – 50,000◦ 9,000 in Holland; 10,000 in England; 18,000 in Germany

1850’s◦ Multiblade turbines for water pumping made and marketed in U.S.

1882 ◦ Thomas Edison commissions first commercial electric generating stations in

NYC and London 1900

◦ Competition from alternative energy sources reduces windmill population to fewer than 10,000

1850 – 1930◦ Heyday of the small multiblade turbines in the US midwast

As many as 6,000,000 units installed 1936+

◦ US Rural Electrification Administration extends the grid to most formerly isolated rural sites Grid electricity rapidly displaces multiblade turbine uses

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Source: American Wind Energy Association

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Environmental Economic Development Fuel Diversity & Conservation Cost Stability

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No air pollution No greenhouse gasses Does not pollute water with mercury No water needed for operations

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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

Electric power is a primary source of industrial air pollution

Expanding Wind Power development brings jobs to rural communities

Increased tax revenue Purchase of goods & services

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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

Domestic energy source Inexhaustible supply Small, dispersed design

◦ reduces supply risk

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Flat-rate pricing ◦ hedge against fuel price volatility risk

Wind electricity is inflation-proof

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The re-emergence of the wind as a significant source of the world's energy must rank as one

of the significant developments of the late 20th century. The advent of the steam engine, followed by the appearance

of other technologies for converting fossil fuels to useful energy, would seem to have forever relegated to insignificance the role of the wind in energy generation.

In fact, by the mid 1950s that appeared to be what had already happened.

By the late 1960s, however, the first signs of a reversal could be discerned, and by the early

1990s it was becoming apparent that a fundamental reversal was underway.

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To understand what was happening, it is necessary to consider five main factors.

Need An emerging awareness of the finiteness of the earth's fossil fuel reserves as well as of the

adverse effects of burning those fuels for energy had caused many people to look for alternatives

Potential (Availability) Wind exists everywhere on the earth, and in some places with considerable energy density. Wind

had been widely used in the past, for mechanical power as well as transportation.

Technological Capacity In particular, there had been developments in other fields, which, when applied to wind turbines,

could revolutionize they way they could be used.

Political Will

Vision of new way of utilization

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A wind turbine, is a machine which converts the power in the wind into electricity.

This is in contrast to a ‘windmill’, which is a machine which converts the wind’s power into mechanical power.

As electricity generators, wind turbines are connected to some electrical network.

These networks include battery charging circuits, residential scale power systems, isolated or island networks, and large utility grids.

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Today, the most common design of wind turbine, is the horizontal axis wind turbine (HAWT).

That is, the axis of rotation is parallel to the ground.

HAWT rotors are usually classified according to The rotor orientation (upwind or downwind of the

tower), Hub design (rigid or teetering), Rotor control (pitch vs. stall), Number of blades (usually two or thee blades),

and How they are aligned with the wind (free yaw or

active yaw).

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The principal subsystems of a typical horizontal axis wind turbine include:

The rotor, consisting of the blades and the supporting hub

The drive train, which includes the rotating parts of the wind turbine (exclusive of the rotor); it usually consists of shafts, gearbox, coupling, a mechanical brake, and the generator

The nacelle and main frame, including wind turbine housing, bedplate, and the yaw system

The tower and the foundation The machine controls The balance of the electrical system, including cables,

switchgear, transformers, and possibly electronic power converters

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A wind turbine usually has the following components:

Rotor consisting of the hub and blades of the turbine. Most turbines have rotors with three blades and a few designs with two blades.

Nacelle that houses the main components of the wind turbine, such as the controller, gearbox, generator, and shafts.

Shafts including the low speed and high speed shafts connected to the rotating components.

Gear box to convert the low rotational speed of the rotor into a higher speed for the electric generator.

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Generator that converts the mechanical energy from the wind turbine’s rotation into electrical energy.

Yaw system responsible for the orientation of the wind turbine rotor towards the wind.

Mechanical brake used to hold the turbine at rest for maintenance..

Anemometer for measuring the wind speed. Tower usually made of tubular steel and is 60 to 100

meters high. Power electronic converter used to adjust the

electrical output of the wind turbine (must be used with grid connected WECS).

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The power output of a wind turbine varies with wind speed and every wind turbine has a characteristic power performance curve.

With such a curve it is possible to predict the energy production of a wind turbine without considering the technical details of its various components.

The power curve gives the electrical power output as a function of the hub height wind speed.

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The performance of a given wind turbine generator can be related to three key points on the velocity scale:

Cut-in speed: the minimum wind speed at which the machine will deliver useful power

Rated wind speed: the wind speed at which the rated power (generally the maximum power output of the electrical generator) is reached

Cut-out speed: the maximum wind speed at which the turbine is allowed to deliver power (usually limited by engineering design and safety constraints)

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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

Wind Speed◦ Wind energy increases with the cube of the wind speed◦ 10% increase in wind speed translates into 30% more

electricity◦ 2X the wind speed translates into 8X the electricity

Height◦ Wind energy increases with height to the 1/7 power◦ 2X the height translates into 10.4% more electricity

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Air density◦ Wind energy increases proportionally with air density◦ Humid climates have greater air density than dry climates◦ Lower elevations have greater air density than higher elevations◦ Wind energy in Denver about 6% less than at sea level

Blade swept area◦ Wind energy increases proportionally with swept area of the

blades Blades are shaped like airplane wings

◦ 10% increase in swept diameter translates into 21% greater swept area

◦ Longest blades up to 413 feet in diameter Resulting in 600 foot total height

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Theoretical maximum energy extraction from wind = 16/27 = 59.3%

Undisturbed wind velocity reduced by 1/3 Albert Betz (1928)

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This picture shows a Vestas V-80 2.0-MW wind turbine superimposed on a Boeing 747 JUMBO JET

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2003 1.8 MW

350’

2000 850 kW

265’

2006 5 MW 600’

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1. Hub controller 11. Blade bearing2. Pitch cylinder 12. Blade3. Main shaft 13. Rotor lock system4. Oil cooler 14. Hydraulic unit5. Gearbox 15. Machine foundation6. Top Controller 16. Yaw gears7. Parking Break 17. Generator8. Service crane 18. Ultra-sonic sensors9. Transformer 19. Meteorological gauges10. Blade Hub

Nacelle Components

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Larger turbines Specialized blade design Power electronics Computer modeling

◦ produces more efficient design Manufacturing improvements

Drastic improvements since mid-80’s Manufacturers report availability data of

over 95%

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1981 '83 '85 '90 '98

% A

vail

able

Year0

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60

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100

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Wind PowerClass

10 m (33 ft) 50 m (164 ft)

Speed m/s (mph)

Speed m/s (mph)

10 0

4.4 (9.8) 5.6 (12.5)2 5.1 (11.5) 6.4 (14.3)3 5.6 (12.5) 7.0 (15.7)4 6.0 (13.4) 7.5 (16.8)5 6.4 (14.3) 8.0 (17.9)6 7.0 (15.7) 8.8 (19.7)7 9.4 (21.1) 11.9 (26.6)

Wind speed is for standard sea-level conditions. To maintain the same power density, speed

increases 3%/1000 m (5%/5000 ft) elevation.

Winds◦Minimum class 4 desired for utility-scale wind farm (>7

m/s at hub height)Transmission

◦Distance, voltage excess capacityPermit approval

◦Land-use compatibility◦Public acceptance◦Visual, noise, and bird impacts are biggest concern

Land area◦Economies of scale in construction◦Number of landowners

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Siting◦Avian◦Noise◦Aesthetics

Intermittent source of powerTransmission constraintsOperational characteristics different from

conventional fuel sourcesFinancing

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Pros◦Small project size◦Short/flexible development time ◦Dispatchability

Cons◦Generally remote location ◦Grid connectivity -- lack of transmission capability ◦Intermittent output

Only When the wind blows (night? Day?)◦Low capacity factor◦Predicting the wind -- we’re getting better

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Birds of Prey (hawks, owls, golden eagles) in jeopardy Altamont Pass – News Update – from Sept 22

◦shut down all the turbines for at least two months each winter◦eliminate the 100 most lethal turbines◦Replace all before permits expire in 13 years

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Remote location and low capacity factorHigher transmission investment per unit output

Small project size and quick development time

Planning mismatch with transmission investmentIntermittent output

Higher system operating costs if systems and protocols not designed properly

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Key Design Parameters◦Mean wind speed at hub height◦Capacity factor

Start with 100% Subtract time when wind speed less than optimumSubtract time due to scheduled maintenanceSubtract time due to unscheduled maintenanceSubtract production losses

Dirty blades, shut down due to high windsTypically 33% at a Class 4 wind site

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Financing Terms◦Interest rate

LIBOR + 150 basis points◦Loan term

Up to 15 years

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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

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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%

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Capacity factor◦Start with 100% ◦Subtract time when wind speed < optimum◦Subtract time due to scheduled maintenance◦Subtract time due to unscheduled maintenance◦Subtract production losses

Dirty blades, shut down due to high winds◦Typically 33% at a Class 4 wind site

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Performance Improvements due to :◦Better siting◦Larger turbines/energy capture◦Technology Advances◦Higher reliability

Capacity factors > 35% at good sitesExamples (Year 2000)

◦Big Spring, Texas 37% CF in first 9 months◦Springview, Nebraska

36% CF in first 9 months

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Key parameter◦Distance from grid interconnect

≈350,000$/mile for overhead transmission lines

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Example◦200 MW wind farm

Fixed costs - $1.23M/MW◦Class 4 wind site

33% capacity factor◦10 miles to grid◦6%/15 year financing

100% financed◦20 year project life

Determine Cost of Energy - COE

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Total Capital Costs◦$246M + (10 x $350K) = $249.5M

Total Annual Energy Production◦200 MW x 1000 x 365 x 24 x 0.33 = 578,160,000 kWh

Total Energy Production◦578,160,000 x 20 = 11,563,200,000 kWh

Capital Costs/kWh◦3.3¢/kWh

Operating Costs/kWh◦1.6¢/kWh

Cost of Energy – New Facilities◦Wind – 4.9¢/kWh◦Coal – 3.7¢/kWh◦Natural gas – 7.0¢/kWh

@12$/MMBtu

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Key parameters◦Wind resource◦Zoning/Public Approval/Land Lease ◦Power purchase agreements◦Connectivity to the grid◦Financing◦Tax incentives

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Wind resource◦Absolutely vital to determine finances

Wind is the fuel◦Requires historical wind data

Daily and hourly detail◦Install metrological towers

Preferably at projected turbine hub heightMultiple towers across proposed site◦Multiyear data reduces financial risk

Correlate long term offsite data to support short term onsite data

Local NWS metrological station

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69Source: Garrad Hassan America, Inc.

Zoning/Public Approval/Land Lease ◦Obtain local and state governmental approvals

Often includes Environmental Impact StudiesImpact to wetlands, birds (especially raptors)

NIMBY componentView sheds

◦Negotiate lease arrangements with ranchers, farmers, Native American tribes, etc.

Annual payments per turbine or production based

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Power Purchase Agreements (PPA)◦Must have upfront financial commitment from utility◦15 to 20 year time frames◦Utility agrees to purchase wind energy at a set rate

e.g. 4.3¢/kWh◦Financial stability/credit rating of utility important aspect

of obtaining wind farm financingPPA only as good as the creditworthiness of the uitilityUtility goes bankrupt – you’re in trouble

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Connectivity to the grid◦Obtain approvals to tie to the grid

Obtain from grid operators – WAPA, BPA, California ISO

◦Power fluctuations stress the gridEspecially since the grid is operating near max

capacity

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Financing◦Once all components are settled…

Wind resourceZoning/Public Approval/Land LeasePower Purchase Agreements (PPA)Connectivity to the gridTurbine procurementConstruction costs◦…Take the deal to get financed

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74Source: Hogan & Hartson, LLP

Small developers utilize a “partnership flip”◦Put the deal together◦Sell it to a large wind owner

e.g. Florida Power & Light, AEP, Shell Wind Energy, PPM – Scottish Power

Shell and PPM jointly own Lamar wind farm◦Large wind owner assumes ownership and builds

the wind farm

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Federal government subsidizes wind farm development in three ways

◦1.9/ ¢kWh production tax credit33.5% subsidy◦5 year depreciation schedule

29.8% subsidy◦Depreciation bonus

2.6% subsidy

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Small developers can’t fully use federal tax credits or accelerated depreciation

◦They don’t have a sufficient tax liability◦Example

A 200 MW wind farm can generate a $12.6M tax credit/year

Small developers don’t have sufficient access to credit to finance a $200M+

project

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1.9¢/kWh Production Tax Credit◦First 10 years for producing wind generated electricity◦Wind farm must be producing by 12/31/07◦PTC has been on again/off again since 1992◦Results in inconsistent wind farm development

PTC in place – aggressive developmentPTC lapses – little or no development

The PTC puts wind energy on par with coal and significantly less than natural gas

◦When natural gas > $8.00/MMBtuCurrent prices: $10 – $15/MMBtu

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Renewable Portfolio Standard◦21 States have them◦Colorado’s Amendment 37

Passed by voters November 20043% of generation from 2007 - 20105% of generation from 2011 - 201410% of generation by 2015 and beyond◦4% of renewable generation from solar PV◦96% of renewable generation from wind, small

hydro and biomass◦Small utilities can opt out of program

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You subsidize wind energy when produced by another utility

◦CU pays $0.006/kWh to Community EnergyTo power the UMC, Wardenburg and the Recreation Center

◦Community Energy uses these funds to subsidize wind energy at wind farms in Lamar and in the upper Midwest

◦Although CU isn’t getting the electrons from these wind farms, it is in effect buying wind energy

◦The three new buildings (Business, Law, and Atlas) will also be powered by wind energy

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82Source: American Wind Energy Association

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20,000 total turbines installed by 20106% of electricity supply by 2020

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100,000 MW of wind power installed by 2020

Financing StrategiesManufacturing

Economy of ScaleBetter Sites and

“Tuning” Turbines for Site Conditions

Technology Improvements

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Application Specific Turbines◦Offshore◦Limited land/resource areas◦Transportation or construction limitations◦Low wind resource◦Cold climates

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•1.5 - 6 MW per turbine•60-120 m hub height•5 km from shore, 30 m deep ideal•Gravity foundation, pole, or tripod formation•Shaft can act as artificial reef•Drawbacks- T&D losses (underground cables lead to shore) and visual eye sore

Pumped hydroelectric◦Georgetown facility – Completed 1967◦Two reservoirs separated by 1000 vertical feet◦Pump water uphill at night or when wind energy production exceeds

demand◦Flow water downhill through hydroelectric turbines during the day or

when wind energy production is less than demand◦About 70 - 80% round trip efficiency◦Raises cost of wind energy by 25%◦Difficult to find, obtain government approval and build new facilities

Compressed Air Energy Storage◦Using wind power to compress air in underground storage caverns

Salt domes, empty natural gas reservoirs◦Costly, inefficient

Hydrogen storage◦Use wind power to electrolyze water into hydrogen◦Store hydrogen for use later in fuel cells◦50% losses in energy from wind to hydrogen and hydrogen to electricity◦25% round trip efficiency◦Raises cost of wind energy by 4X

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Best wind sites distant from ◦population centers◦major grid connections

Wind variability ◦Can mitigate if forecasting improves

Non-firm power◦Debate on how much backup generation is required

NIMBY component◦Cape Wind project met with strong resistance by Cape

Cod residentsLimited offshore sites

◦Sea floor drops off rapidly on east and west coastsNorth Sea essentially a large lake

Intermittent federal tax incentives

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