JEE4360 – Energy Alternatives

• Wind Technologies • Assignment – Due • Quiz / Project Presentation

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Introduction

• Energy source: wind = solar energy converted to kinetic energy • Terminology – Distinction between “mill” and “turbine” – Two basic types: • Horizontal Axis (HAWT) • Vertical Axis Wind Turbine (VAWT) • Modern turbine depends on – Aerospace technology – Modern materials engineering – Sophisticated fluid mechanics – Precise electronic controls

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1 Madison , Madison, NY Source: www.photosfromonhigh.com

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Wind Power Basics

• Resource 72TW commercially viable globally

• Capital $2M / MW as of 3-2009 • 20% to 40%

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2 Wind Business in Year 2003 Source: American Wind Energy Association, http://www.awea.org/news/news040310glo.html

Top five wind Total MW Top five wind Total Growth energy installed energy MW by markets in markets, end of 2003 worldwide 2003

Germany 2,645 Germany 14,609 22% USA 1,687 USA 6,374 36% Spain 1,377 Spain 6,202 29% India 408 Denmark 3,110 -- Austria 276 India 2,110 -- WORLD 8133 -- 39,294 21% Wind Technologies 5

World 59,000 to 158,000 MW

Wind MW Installed

40,000 35,000 30,000 25,000 20,000 15,000 10,000 5,000 0 2005 2006 2007 2008 2009 United States 9,149 11,603 16,819 25,170 35,159 Germany 18,428 20,622 22,247 23,903 25,777 China 1,266 2,599 5,912 12,210 25,104 Spain 10,028 11,630 15,145 16,740 19,149 India 4,430 6,270 7,850 9,587 10,925

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3 Growth in US Wind Energy 1980-2003 Source: Spera (1994), Figure 4-28, and AWEA

• Wind energy outpaced expectations in late 90s early 2000s • For comparison, capacity (2000) was 322,000 GW

7000

6000 ] W M

[ 5000

y t i c

a 4000

p Actual a c

Trend

e 3000 v i t a l

u 2000 m u

C 1000

0 1980 1985 1990 1995 2002 2003

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Figure 12-5. Main parts of a utility-scale wind turbine

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Operating Requirements for HAWTs

• Start, stop, and control output during operation • Assisted startup: use turbine as motor • Change pitch during operation to modulate power • Stopping function: – “loss of load” emergency – Winds above design speed – Can also shed wind at high wind speeds • “Solidity” of blades: area of blades relative to total swept area

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5 Figure 12-11. Power curve for 1.5-MW turbine for wind speeds from 0 to 21 m/s, with extraction efficiency

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Modeling Aerodynamic Behavior of Wind Turbines • Levels of modeling: – Actuator Disc Model (idealized rotor with infinite number of blades) – Strip Theory (Incorporate blade geometry) – Computational fluid dynamics model (outside of scope of course)

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6 Diagram of airstream flow through an actuator disk

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Introduction to Strip Theory

• Related to propeller theory, which works in reverse (i.e. putting energy into air) • Also known as blade element theory – i.e. divide blade into elements, analyze separately • Blade element approximation is satisfactory for HAWT analysis – Expanding wake means shed vortices outside of rotor diameter – Unlike air or water propellers

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7 Tip Speed Ratio and Advance Ratio • TSR “”:  = R/U where –  is rotation speed in rad/s – R is swept area radius (length of blade) in m – U is free wind speed in m/s • Advance Ratio J: J = 1 / 

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Rotor power coefficient CPr as function of tip speed ratio

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8 Winds and forces acting on a cross section of a turbine blade, showing angle of attack 

between midline of cross section and relative wind velocity Vr.

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Variables used in analysis of blade element in annular ring

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9 Relationship between angle of attack , pitch , and wind angle .

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Economics of Wind

• Choice of site using wind data • Land requirements • Cost elements: – Installed capital cost: turbines + balance of system: roads, cables, substations, etc – Operation & maintenance (~2% of cap charge) – Insurance, royalties, land rentals (~ 0.5%) – Balance of system costs ~ 20% of total capital costs for on-shore systems • Other factors e.g. – Volatility of price gives wind a market advantage – Proximity to transmission line – Air quality permitting not required (advantage over fossil fuels) Wind Technologies 20

10 Net value of wind park investment in constant dollars for MARR in range 3 to 7%.

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Land Requirements for Large-Scale Wind Production • Suppose we replace 500 average coal plants = 1 trillion kwhr/yr (100 million US avg. homes) • Take Fenner site as standard: – $1.5 M per turbine – 7 turbines per sq mi – 4.4 M kwhr per turbine per year • Number of turbines required: 230,000 – Compare: goal of 230,000 MW installed in Europe by 2020 • Area required: 33,000 sq mi (21% of North & South Dakota combined) • Cost: approx $350 billion

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11 Layout Considerations for Wind Parks • Each turbine must have enough space around the post to rotate in any direction • Turbines in a line perpendicular to prevailing wind must have 2x rotor radius space to avoid collisions • Turbines along line of prevailing wind must have 5x to 10x rotor radius to avoid negative effects of turbulence

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Using Software to Optimize Wind Farm Layout • Data requirements – Topographical data – Wind data – Technology characteristics of turbines • Given number of devices, terrain, wind, optimizes location to maximize output

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