0-SomeBasicFactsAboutWindEnergy

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Wind Energy: Some Basic Facts

C.L. Bottasso

Politecnico di Milano

November 2011

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POLITECNICO di MILANO POLI-Wind Research Lab

Outline

• Basic working principles of a wind turbine, and its anatomy

• Some basic figures

• Trends: the exploitation of off-shore resources

• Wind energy research at the Politecnico di Milano

• Concluding remarks

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How it Works

Maximum theoretical aerodynamic efficiency = 16/27 ≈ 0.593 (Betz limit)

Aerodynamic efficiency in practice < 0.50

(plus mechanical and electrical losses)

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Anatomy

(source: GE)

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Anatomy

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(sources: reuk.co.uk, geograph.org.uk, coriolis-energy.com)

Gearbox-Based Configurations

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(sources: wind-energy-the-facts.org, scruss.com, windpowerengineering.com, inhabitat.com, leitwind.com)

Direct-Drive Configurations

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(sources: wind-energy-the-facts.org, eetweb.com, machinedesign.com)

Hybrid Concepts

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Dimensions

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Unique Aspects Some differences with respect to aeronautical applications:

• Dimensions: need relatively low cost materials, large volumes

• Reliability/maintenance: performance with simplicity and robustness

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Where is the Wind in Europe

Forecasts of reasonable accuracy: 6% 24 h, 2.5% 2h (ISET)

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The Energy Mix

• Wind energy cannot have the same importance in all countries

• Different countries should aim at different energy mixes, depending on their specific natural resources

• An integrated efficient network enables the management of the energy mix within each country (time of the day/season) and across borders

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Installed Wind Energy in Europe

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… and in the World

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Growth Trend

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Wind Energy Share in Europe

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Where We Are wrt the 2020 Objectives

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Comparison with Other Energy Sources

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Cost Comparisons

“External costs”: due to effects on environment, CO2 emissions, health

Subsidies: 23.9 G€ non-renewables, 5.3 G€ renewables (2001, source EU)

(source: Vestas)

€cent/kWh

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Trends: Off-Shore Wind

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Off-Shore Wind ◀ Great potential resources

Great technological problems ▶ (logistics, maintenance,

harsh environment)

… great opportunities

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Trends: Deep Waters

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Some Deep Water Concepts

(source: Deepwater Wind) (source: StatoilHydro) (source: Principle Power)

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Wind Energy at the Politecnico di Milano

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An Example: the Wind Tunnel

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Turbulence (boundary layer) generators

The Wind Tunnel of the Politecnico Turn-table

13 m

• High speed testing • Aerodynamic characterization (Cp-TSR-β & CF-TSR-β curves)

• Low speed testing with vertical wind profile • Multiple wind turbine testing (wake-machine interaction)

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The First Ever Actively-Controlled Aeroelastically-Scaled Model

Conical spiral gears

Main shaft with torque meter

Pitch actuator electronics

Slip ring

Torque actuator: • Planetary gearhead • Torque and speed control

Pitch actuator: • Zero backlash gearhead • Built-in encoder

Rotor sensor electronics

Radius = 1m

Height = 1.87 m

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• Wind energy by itself does not solve the energy problem

• However, it can contribute significantly, especially in some countries

• Off-shore wind can alleviate some public acceptance issues (NIMBY: Not In My Back-Yard), and allows for the exploitation of huge available resources

• From the technological point of view, there are many fascinating problems that need to be solved (research) and opportunities for improvement

Concluding Remarks

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European Wind Energy Association: www.ewea.org Global Wind Energy Council: www.gwec.net

Further Information

http://www.ewea.org/

http://www.gwec.net/

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