List four sources of the energy shortfall between rotor collected energy and electrical output.

Gearbox friction and bearing friction waste energy as heat. Generator losses and transformer losses reduce the electrical output further.

Why does a turbine's own equipment reduce the energy it exports?

Yaw motors, pitch actuators, cooling fans and control electronics all draw electricity. The turbine uses some of its own output, and imports power when the wind is calm.

What is a wind turbine power curve?

A power curve is a graph of a turbine's electrical output against wind speed. Manufacturers publish one for each model so its energy yield at a site can be predicted.

CCEA A-Level Environmental Technology 3930

Fossil Fuels

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Global Action on Energy Conservation and Climate Change

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Macrogeneration

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Microgeneration

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Energy From Wind

Topic overview Horizontal and vertical axis wind turbines Kinetic energy, wind power and the Betz limit Power curves, rated output and energy losses Swept area, blade length and turbine mass Air density, hub height and turbine siting Power control, yawing and survival speed Choosing a location for a commercial wind farm

Energy From the Sun

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Energy Storage

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Energy Performance of Buildings

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Emerging Technologies

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Energy From Wind

Power curves, rated output and energy losses

3 things to know
AS 1

Overview

Rotor collected energy against rated output and the losses between them, power curves, cut-in, rated and cut-out speeds, estimating annual output from site wind data, and capacity factor calculations.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is meant by rotor collected energy?

Key term

What is meant by the rated energy output of a wind turbine?

Key term

Explain why rated energy output is always lower than rotor collected energy.

Questions from this subtopic

Each one with the model answer underneath.

1
What is meant by rotor collected energy?
Model answer
Rotor collected energy is the kinetic energy the blades actually take from the wind and turn into rotation of the shaft. The amount never exceeds 59.3% of the energy in the wind.
2
What is meant by the rated energy output of a wind turbine?
Model answer
Rated energy output is the electrical output a turbine is designed to deliver at its rated wind speed. A 2 MW turbine produces 2 MW at wind speeds between rated and cut-out.
3
Explain why rated energy output is always lower than rotor collected energy.
Model answer
Energy is lost between the rotor and the grid connection. Friction in bearings and the gearbox wastes some as heat, and the generator and power electronics lose more.
4
List four sources of the energy shortfall between rotor collected energy and electrical output.
Model answer
Gearbox friction and bearing friction waste energy as heat. Generator losses and transformer losses reduce the electrical output further.
5
Why does a turbine's own equipment reduce the energy it exports?
Model answer
Yaw motors, pitch actuators, cooling fans and control electronics all draw electricity. The turbine uses some of its own output, and imports power when the wind is calm.
6
What is a wind turbine power curve?
Model answer
A power curve is a graph of a turbine's electrical output against wind speed. Manufacturers publish one for each model so its energy yield at a site can be predicted.

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Fossil Fuels

Global Action on Energy Conservation and Climate Change

Macrogeneration

Microgeneration

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