wind energy

EE4511 Sustainable Energy Systems

Panida Jirutitijaroen Department of Electrical and Computer Engineering

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Lecture 8: Wind Energy I 05/03/2013

About Me

Hi! My name is Panida Jirutitijaroen.

I joined ECE, NUS as an Assistant Professor since 2008.

Here is my contact information.

Office: E2-03-19.

Email: [email protected]

http://www.ece.nus.edu.sg/stfpage/elejp/

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Assessment

2nd Test 15% Wednesday April 3rd 6-7PM @ LT 1.

In-class discussion 10% To be announced.

Final 50% Cumulative.

Closed book.

Calculator is allowed.

You can bring in one page note (A4-size), two-sided, with your own handwriting.

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Syllabus

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Date Topics

05/03/13 Wind Energy I: Wind turbine types and characteristics

06/03/13 1st Mid-term test, 6-7pm @ LT1

07/03/13 Wind Energy II: Power in the wind, wind turbine generator and control

12/03/13 Wind Energy III: Wind turbine performance and its environmental impact

14/03/13 Tutorial on wind energy

19/03/13 System Integration issues I: Overview of Energy System. Secure, economic, and reliable operation

21/03/13 System Integration issues II: Power quality and reliability in operation and planning, Issues with renewable energy sources

26/03/13 Economics of distributed resources I: Utility rate structure, Energy economics

28/03/13 Economics of distributed resources II: Combined Heat and Power, Integrated Resources

Planning, Demand Side Management.

02/04/13 Tutorial on system integrations and economics

03/04/13 2nd Mid-term test, 6-7pm @ LT1

04/04/13 In-class group discussion: Cape Wind Controversy the 1st Off-Shore Wind Farm in the US

09/04/13 In-class group discussion- Role play @ Engineering Auditorium

11/04/13 In-class group discussion- Presentation @ Engineering Auditorium

Reference

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Topics Chapter

Wind Power Systems

Types of wind turbine generator, power in the wind

Wind turbine generator, speed control

Average power in the wind and energy estimates

Wind turbine performance calculation

6.1-6.5

6.6-6.7

6.8-6.9

6.10

System integration of renewable energy sources

Power quality

Basic operation and planning, screening curve

2.7-2.8

3.9-3.10

Economics of distributed resources

Utility rate structure, energy economics, supply

curves

Energy conservation, combined heat and power,

distributed benefit

Integrated resource planning and demand side

management

Wind turbine economics.

5.1-5.3

5.4-5.7

5.8

6.11-6.12

Additional Reference

Wind Turbine Technology Fundamental Concepts of Wind Turbine Engineering

Chapter 2 Introduction to Modern Wind Turbines.

Downloadable from NUS library.

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Outline

Introduction to wind power

Wind resources

On-shore VS Off-shore

Types of wind turbines

Vertical-Axis Wind turbines

Horizontal-Axis Wind turbines

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INTRODUCTION TO WIND POWER

History of wind energy

Wind resources around the world

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Worlds First Wind Turbine

Vejen, Denmark. Built in 1891 by Dane Poul

La Cour. He was an inventor and a

high school teacher back then.

This is the first wind turbine to generate electricity, which was used to electrolyze water, producing hydrogen for gas lights in the school house. Source: http://www.poullacour.dk/engelsk/menu.htm

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History of US Wind Energy

In 1888, the first use of large windmill to generate electricity is in Cleveland, Ohio. Rotor diameter was 17meters. The windmill produced 12 kW.

1930s and 1940s, small wind system used in rural areas. Grandpas Knob in Vermont,1941, 1250kW,

175-ft diameter, failed in 1945.

As utility grid expanded and become more reliable, electricity price declined.

Wind energy popularity fluctuates with the price of fossil fuels. After World War II, oil prices declined so as

the wind energy popularity. Oil crisis in the 1970s stimulated worldwide

interest in wind turbine generators.

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Grandpas knob

Source: http://www.telosnet.com/wind/early.html

Top 10 Wind Capacity in 2011

Source: GWEC Global Wind Report, Annual market update 2011

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Approximate Wind Penetration

Source: 2011 Wind technologies market report, US DOE

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EU Wind Penetration

Source: EWEA 2011 European statistics, February 2012.

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Total Wind Power Installation in EU

Source: EWEA 2011 European statistics, February 2012.

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Cumulative Wind Capacity in USA

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Wind Power Plant Locations

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source: http://www.ashden.org/wind

Onshore Wind Power Station

Offshore Wind Power Station

source: http://www.nrdc.org

Onshore Wind Farms

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Alta Wind Energy Center ("AWEC") is located in Tehachapi, CA has installed capacity of 1,320 MW, of which 1,020 MW are currently in operation. As of 2012, it is the largest wind farm in the United States.

Offshore Wind Farms

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Denmark Off-shore wind farms

Large Offshore Wind Farms in Europe

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Source: http://www.awstruepower.com

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Source: http://www.awstruepower.com

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Source: NREL

Offshore Wind Farms in the USA

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According to 2011 Wind technologies market report, US DOE, no offshore wind farm has been commissioned in the US. We will study social, environmental, and economical impacts of offshore wind farms in in-class discussion (10% CA).

TYPES OF WIND TURBINES

Horizontal axis wind turbines

Vertical axis wind turbines

Inside wind turbine

On shore VS Off shore technologies

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Wind Power Systems

Terminology

Wind-driven generator

Wind generator

Wind turbine

Wind-turbine generator (WTG)

Wind energy conversion system (WECS)

Types of Wind Turbines

Horizontal axis wind turbines

Vertical axis wind turbines

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Wind Turbines: How It Works

Source: US DOE Energy 101: Wind Turbines

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Horizontal Axis Wind Turbines

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Upwind HAWT Downwind HAWT

Principal Subsystems of HAWTs

Rotor Rotor blades, rotor hub that capture kinetic energy from wind.

Power train Mechanical and electrical components to convert mechanical

power received from rotor hub to electrical power.

Nacelle structure Steel structure enclosing the power train.

Tower Raise rotor and power train to a specified elevation.

Ground equipment station Interface HAWTs with electric utility.

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Inside Wind Turbines

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Source: http://www.alternative-energy-news.info

Rotor Blades

Made from glass-fiber composites, steel. View of cross-section of a composite wind turbine blade. Aerodynamic design. Similar to airplane wing.

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How Rotor Turns

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Source: http://green-energy-center.blogspot.com/2008/07/wind-turbine-blade-design-designing.html Air moving over top of airfoil has more

distance to travel Air pressure on top is lower than that under airfoil create Lift!

source: http://www.free-online-private-pilot-ground-school.com/aerodynamics.html

Angle of Attack

Angle of attack improves lift. It should be set at the maximum lift-to-drag force ratio.

Too high angle of attack can cause stall. Wind on top of the airfoil no longer attach to the surface Drag force also reduce the effect of lift force and slow down the rotor.

This means that we can control the speed of wind turbine by controlling the angle of attack. Decrease angle of attack decrease lift-to-drag ratio (pitch control) Increase angle of attack decrease lift-to-drag ratio (stalling)

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Lift force

Drag force

Lift force

Drag force

Lift force

Drag force

Net Aerodynamic Force on Blade

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Relative wind due to blade motion

Resulting wind source: http://www.gurit.com

Rotor Speed Along the Blade

For a constant rotational speed, the speed of the rotor along the blade is proportional to the distance from the hub.

The nearer to the tip (further from the hub), the stronger the apparent wind is.

Blade must be twisted to keep the angles right to maximize the lift-to-drag force ratio.

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source: http://www.gurit.com

Number of Blades

Multi-blade windmill need high starting torque and low wind speed for continuous water pumping function.

As rpm increases, turbulence caused by one blade affects efficiency of the blade that follows

Fewer blades allow the turbine to spin faster => smaller generator.

Two and three blades are the most common in modern wind turbine.

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Source: http://www.wind-energy-the-facts.org http://www.climatechangeconnection.org http://www.sti.nasa.gov

HAWTs: Upwind VS Downwind

Upwind turbine

Complex yaw control system.

Keep blade facing wind.

Operate more smoothly.

Deliver more power.

Downwind turbine

Let the wind control left-right motion (the yaw).

Orient itself correctly to wind direction.

Wind shadowing effect by the tower, cause the blade to flex.

Increase noise and reduce power output.

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Vertical Axis Wind Turbines

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Darrieus VAWTs

Principal Subsystems of VAWTs

Rotor Typically contains 2-3 blades, symmetrical in cross-section. Rotor height is usually 15-30% larger than diameter.

Power train Mechanical and electrical components to convert mechanical

power received from rotor hub to electrical power.

Support structure Upper and lower rotor bearings, 3-4 structural cables (guy wire)

at an elevation angle of 30-40 degree with tensioning devices, and a support stand.

Ground equipment station Interface VAWTs with electric utility, similar to HAWTs.

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HAWTs VS VAWTs

HAWTs

The turbines need to be align with the wind direction.

Capture wind energy at higher power.

Power-train equipments located above ground Costly maintenance.

VAWTs

Capture wind energy from any direction because of the turbine is symmetry about its vertical axis. dont require yaw control

Cant capture wind energy at high altitude.

Power-train equipments are located at or near the ground Easier maintenance.

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Offshore VS Onshore

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VAWTs for Off-Shore? New Releases on July 30, 2012 www.sandia.gov The economics of offshore windpower are different from land-based turbines, due to installation and operational challenges. VAWTs offer three big advantages that could reduce the cost of wind energy: a lower turbine center of gravity; reduced machine complexity; and better scalability to very large sizes. A lower center of gravity means improved stability afloat and lower gravitational fatigue loads. Additionally, the drivetrain on a VAWT is at or near the surface, potentially making maintenance easier and less time-consuming. Fewer parts, lower fatigue loads and simpler maintenance all lead to reduced maintenance costs.

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Goodbye Nuclear, Hello Renewables

Article from www.newscientist.com dated 16 January 2013.

Japanese government announced its plan to build a total of 143 wind turbines 16 kms off the coast of Fukushima by 2020.

Total capacity 1GW!! (to become the worlds largest wind farm)

Part of Fukushimas plan to become energy self-sufficient by 2040.

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Summary

Types of wind turbine

Turbine aerodynamic

Angle of attack

Lift-to-drag ratio

Vertical axis VS Horizontal axis

Comparisons between HAWTs and VAWTs

Comparisons between onshore and offshore WTs

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Next Lecture

Wind Turbine II

Power in the wind

Power extracted from the wind

Wind Energy Conversion Systems (WECS)

Speed control for wind turbines

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