Based on their fundamental design, modern windmills, commonly referred to as wind turbines when generating electricity, are primarily classified by the orientation of their rotation axis.
The most fundamental way modern wind turbines are classified is based on the orientation of their rotating shaft or axis. As highlighted by the reference (dated 27-Dec-2023), there are two basic types: Horizontal-axis turbines and Vertical-axis turbines.
This classification determines key characteristics of the turbine's structure, operation, and applications.
Primary Classification: Axis Orientation
Wind turbines capture kinetic energy from the wind and convert it into rotational energy, which then drives a generator to produce electricity. The axis around which the blades rotate defines its primary classification.
- Horizontal-Axis Wind Turbines (HAWTs): These are the most common type seen globally, characterized by their main rotor shaft and electrical generator located at the top of a tower, with the blades pointing into the wind.
- Vertical-Axis Wind Turbines (VAWTs): These have their main rotor shaft oriented vertically. The main components, such as the gearbox and generator, can be located at the base of the turbine, closer to the ground.
Let's look at these types in a bit more detail:
Horizontal-Axis Wind Turbines (HAWTs)
HAWTs are the dominant design in the modern wind energy industry, both for large utility-scale wind farms and smaller distributed generation.
Key Characteristics:
- Design: Typically feature two or three blades, resembling a giant propeller.
- Yaw System: Requires a mechanism to turn the rotor to face the wind for optimal performance.
- Efficiency: Generally considered more efficient at capturing wind energy than VAWTs in consistent wind conditions, especially at higher altitudes where wind is stronger and steadier.
- Applications: Used extensively in onshore and offshore wind farms.
Vertical-Axis Wind Turbines (VAWTs)
While less common for large-scale power generation compared to HAWTs, VAWTs offer certain advantages, particularly in specific locations or niche applications.
Key Characteristics:
- Design: Come in various forms, such as the Darrieus (eggbeater shape) or Savonius (S-shape) designs.
- Omni-directional: Do not need to be oriented into the wind, as they can capture wind coming from any direction.
- Components at Base: Heavy components like the generator and gearbox can be located closer to the ground, simplifying maintenance.
- Applications: Suitable for urban environments, rooftops, or locations with turbulent wind where their omni-directional nature and lower profile can be advantageous.
Summary Table
| Feature | Horizontal-Axis Wind Turbine (HAWT) | Vertical-Axis Wind Turbine (VAWT) |
|---|---|---|
| Axis | Horizontal | Vertical |
| Blade Shape | Propeller-like | Various (e.g., Darrieus, Savonius) |
| Wind Capture | Needs to face the wind | Captures wind from any direction |
| Common Use | Large-scale power generation, wind farms | Niche applications, urban settings, small scale |
In conclusion, the primary classification of modern windmills (wind turbines) revolves around whether the rotor spins on a horizontal or vertical axis, fundamentally influencing their design, performance, and suitability for different applications.
