Question

Minimum wind speed required for the operation for windmill usually ranges from

• A. 4-6 km/hr
• B. 6-8 km/hr
• C. 8-10 km/hr
• D. 10-12 km/hr

Hint:

Multi-blade windmills have high starting torque, enabling them to start pumping water at low wind speeds (6-8 km/hr), whereas electricity-generating wind turbines have low starting torque and require higher wind speeds.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
A windmill utilizes wind energy to generate mechanical power (for water pumping) or electrical power.
The minimum wind speed at which a windmill begins to operate is called the "cut-in wind speed."
Detailed Explanation:
- Multi-blade agricultural windmills designed specifically for water pumping are high-torque, low-speed machines.
- Because they have many blades, they have a high solidity ratio and can capture wind energy at very low velocities.
- The cut-in wind speed (minimum wind speed required to overcome mechanical friction and begin rotation) for these multi-blade water-pumping windmills typically ranges from ______6 to 8 km/hr______ (or occasionally 8 to 10 km/hr).
- Windmills designed for electricity generation (usually having 2 or 3 aerodynamic blades) require higher cut-in wind speeds, typically above 10 to 12 km/hr.
- Therefore, for standard water-pumping windmills, the minimum operating speed is lower, starting around 6 to 8 km/hr.

Step 2: Final Answer:
The minimum wind speed required for agricultural water-pumping windmills ranges from 6 to 8 km/hr, corresponding to option (B).