What is active stall control?

Active stall control pitches the blades slightly the opposite way to pitch control, deliberately increasing stall in high winds. The method gives more precise power control than passive stall.

Compare pitch control with passive stall control.

Pitch control actively adjusts the blades and holds output steady at rated power. Stall control is simpler and cheaper but controls power less precisely in gusty winds.

What is meant by feathering the blades?

A feathered blade is turned edge-on to the wind so it produces almost no lift. The rotor then slows to a stop or idles safely in storms or during faults.

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Energy From Wind

Power control, yawing and survival speed

3 things to know
AS 1

Overview

Pitch control, passive and active stall, feathering, furling on small turbines, variable-speed operation, yawing and unwinding, and survival speed compared with cut-out speed.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why are all wind turbines designed with some form of power control?

Key term

How does pitch control limit a turbine's power in strong winds?

Key term

What is passive stall control?

Questions from this subtopic

Each one with the model answer underneath.

1
Why are all wind turbines designed with some form of power control?
Model answer
Power in the wind rises steeply with speed, and strong winds would overload the generator and structure. Power control limits output to the rated value and protects the turbine.
2
How does pitch control limit a turbine's power in strong winds?
Model answer
Motors turn each blade about its long axis to reduce the angle at which the wind meets it. Less lift is produced, so the rotor keeps output at rated power.
3
What is passive stall control?
Model answer
Passive stall control uses fixed blades shaped so that airflow breaks away from their surface in high winds. The loss of lift automatically limits power without moving parts.
4
What is active stall control?
Model answer
Active stall control pitches the blades slightly the opposite way to pitch control, deliberately increasing stall in high winds. The method gives more precise power control than passive stall.
5
Compare pitch control with passive stall control.
Model answer
Pitch control actively adjusts the blades and holds output steady at rated power. Stall control is simpler and cheaper but controls power less precisely in gusty winds.
6
What is meant by feathering the blades?
Model answer
A feathered blade is turned edge-on to the wind so it produces almost no lift. The rotor then slows to a stop or idles safely in storms or during faults.

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