Understanding Wind Turbines: How They Work And What Determines Their Amount Of Power Generation

Wind energy is one of the fastest growing and most promising sources of renewable electricity worldwide. As concerns about climate change and energy sustainability intensify, wind turbines have become a familiar sight on landscapes across the globe. They harness the kinetic energy of the wind and convert it into electrical power without emitting harmful greenhouse gases or relying on fossil fuels. With rapid advancements in technology and increasing investment in sustainable infrastructure, wind turbines now supply a significant portion of the world’s electricity.

Understanding how wind turbines work involves more than just observing their rotating blades. It requires an appreciation of the physics behind wind movement, mechanical energy conversion, electrical systems, and the environmental and geographical factors that influence their performance. This article explores the fundamental principles of how wind turbines work, the key factors affecting their power generation, and the broader considerations involved in wind energy deployment.

A few words about the WIND project itself

The project has been funded by the European Union’s Recovery and Resilience Facility (RRF), which is the key instrument of the EU’s Recovery Facility (NextGenerationEU). The financing has been granted by the Service Centre for Continuous Learning and Employment (SECLE). The Service Centre promotes the competence development of working-age people and availability of skilled labour. The operations of the Service Centre are overseen by the Ministry of Education and Culture and the Ministry of Economic Affairs and Employment.

Basic Working Principle of Wind Turbines

Wind turbines operate on a simple physical principle: wind turns the blades, which in turn spin a shaft connected to a generator, ultimately producing electricity. The process begins with the wind—air in motion due to differences in atmospheric pressure caused by the sun’s heating of the Earth’s surface.

There are two main types of wind turbines:

• Horizontal-Axis Wind Turbines (HAWT): These are the most common and recognizable type, featuring three blades and a rotor that faces into the wind.
• Vertical-Axis Wind Turbines (VAWT): Less common and used for specific applications, these have blades that rotate around a vertical axis, allowing them to capture wind from any direction.

For example, a horizontal-axis wind turbine typically works as follows:

• Wind Capture: When the wind blows, it passes over the curved blades of the turbine. Due to their aerodynamic design, the wind causes a lift effect on one side of the blade and drag on the other, causing the rotor to spin.
• Rotation and Shaft Movement: The rotor is connected to a main shaft. As the rotor spins, the main shaft also turns. In large turbines, this shaft is connected to a gearbox that increases the rotational speed suitable for electricity generation.
• Electricity Generation: The high-speed shaft from the gearbox drives a generator, which converts the rotational mechanical energy into electrical energy through electromagnetic induction.
• Control Systems: Modern turbines include control systems to optimize performance and ensure safety. These systems can adjust the pitch of the blades (to control rotation speed), yaw (to align the turbine with wind direction), and can shut down the turbine in excessively high wind speeds.

Key Components of a Wind Turbine and Their Functions

A modern wind turbine is made up of several critical components that work together to convert wind into usable electrical energy. While the blades, shaft, gearbox, and generator are central to the energy conversion process, many other parts play essential roles in efficiency, safety, and control.

Here are the major components:

1. Rotor Blades

• Function: Capture wind energy and convert it into rotational motion. Most turbines have three blades, designed aerodynamically to maximize lift and minimize drag.

2. Hub

• Function: Connects the rotor blades together and attaches them to the main shaft. It transfers the rotational energy from the blades to the shaft.

3. Main Shaft (Low-Speed Shaft)

• Function: Transfers rotational energy from the rotor hub to the gearbox. It typically rotates at 10–60 rpm.

4. Gearbox

• Function: Increases the rotational speed from the low-speed shaft (10–60 rpm) to the high-speed shaft (typically 1,000–1,800 rpm) suitable for the generator.

5. High-Speed Shaft

• Function: Connects the gearbox to the generator. Spins at high speeds to drive electricity generation.

6. Generator

• Function: Converts mechanical energy from the shaft into electrical energy using electromagnetic induction.

7. Nacelle

• Function: The protective housing mounted on top of the tower that contains the gearbox, generator, shafts, brakes, and control systems. It allows technicians to access internal components for maintenance.

8. Yaw System

• Function: Rotates the nacelle so that the rotor faces into the wind. This maximizes energy capture. It uses sensors and motors to adjust direction as the wind changes.

9. Yaw Motor and Yaw Drive

• Function: Mechanically rotate the nacelle based on input from wind direction sensor.

10. Anemometer and Wind Vane

• Function:
  • Anemometer measures wind speed.
  • Wind vane determines wind direction.
  • These sensors feed data to the control system for optimal yaw and pitch adjustments.

11. Pitch System

• Function: Adjusts the angle of the blades (pitch) to control rotor speed and power output. It helps optimize performance and can prevent overspeed during high winds.

12. Brake System

• Function: Stops the rotor in emergencies or during maintenance. Can be mechanical, hydraulic, or aerodynamic.

13. Tower

• Function: Supports the nacelle and rotor at a height where wind speeds are higher and more stable. Made of steel or concrete, often 80 to 120 meters tall in utility-scale turbines.

14. Controller

• Function: Acts as the brain of the turbine. It processes input from sensors, controls pitch and yaw systems, monitors operating conditions, and can initiate shutdowns if needed.

15. Transformer

• Function: Converts the voltage of the generated electricity to match the grid or local usage requirements.

How to Determine the Power Output of a Wind Turbine

The power output of a wind turbine depends primarily on the wind speed, rotor size, and air density. To estimate how much electrical power a wind turbine can produce, we rely on a physics-based formula that describes the energy available in the wind and how much of it can be captured by the turbine.

Theoretical Power in Wind

The power available in the wind flowing through the area swept by the turbine blades is given by the formula:

From the above equation, wind speed can be seen to have a cubic relationship with power, implying that any small increase in wind speed will lead to much higher power output.

Actual Power Output (Turbine Power)

However, no turbine can capture all the power in the wind. According to Betz’s Law, the maximum possible efficiency of a wind turbine is about 59.3% (known as the Betz Limit).

So, the actual power output P_actual is given by the equation:

Example Calculation

 Assuming we have a wind turbine in which the blade length is 25 m, wind speed 12m/s, power coefficient is 0.45 and total system efficiency is 0.92. Calculate the actual power output of the turbine.

This estimated output helps in:

• Sizing turbines for specific locations
• Calculating energy production over time (using average wind speed data)
• Evaluating feasibility for wind farm development

Still on the example above, if the blade length was 20 m and under the same wind condition with the same parameters, the total power output would be about 319 kW. This is a difference of close to 180 kW which could power between 90 to 180 homes assuming an average household power consumption of 1 to 2 kW. Rotor blade size is therefore, one of the factors affecting the power output of a wind turbine.

Factors Affecting Wind Turbine Efficiency and Power Output

While the theoretical output of a wind turbine can be calculated using formulas, the actual power generated often varies due to multiple real-world factors. These factors influence how effectively the turbine converts wind energy into electrical energy and how consistently it operates over time.

1. Wind Speed

 Most critical factor affecting power output.

• 
• Low wind areas produce minimal energy, while high wind regions are ideal.
• Turbines have a cut-in speed (typically ~3 m/s), rated speed, and cut-out speed (typically ~25 m/s, beyond which they shut down for safety).2. Air Density

• Denser air carries more energy. Air density is influenced by:
  • Altitude (higher altitude = lower density)
  • Temperature (colder air = denser)
  • Humidity (dryer air = denser)
• Lower air density means lower power output for the same wind speed.3. Rotor Blade Size (Swept Area)
•  The swept area of the blades determines how much wind energy is intercepted.
•  Larger blades capture more energy; power is proportional to the square of the blade radius.
• Turbines with longer blades produce more power, especially at lower wind speeds.

        4. Blade Design and Aerodynamics

• Efficient, lightweight, and aerodynamically optimized blades improve energy capture.
• Poor blade design increases drag and reduce efficiency.
• Influenced by turbine design, control strategy, and operating conditions.5. Mechanical and Electrical Losses
• Energy is lost in the:
  • Gearbox (friction and heat)
  •  Generator
  • Power electronics and transformers
• Efficiency of these components affects total output.6. Turbine Control Systems
• Advanced control systems adjust blade pitch, yaw, and braking to optimize output.
•  Inconsistent or outdated controls may limit efficiency or reduce energy capture in variable winds.7. Turbine Height and Location
•  Higher towers access stronger and steadier winds.
• Turbines placed on ridges, open plains, or offshore areas generally perform better.
• Obstacles (trees, buildings) cause turbulence and reduce efficiency.

         8. Turbulence and Wind Direction Variability

• Turbulence reduces consistent blade rotation and can cause mechanical stress.
• Constant changes in wind direction require yaw adjustments, reducing efficiency.9. Maintenance and Downtime
• Turbines require regular inspection and maintenance.
• Failures or planned shutdowns reduce operational time and, therefore, total energy output.

Key features, Benefits and Shortcomings of Different Wind Turbine types

Horizontal-Axis Wind Turbines (HAWT)

As stated earlier, these are the most used turbines worldwide, especially in large-scale wind farms. Wind farm (or wind park) is a term used to describe an area of several square kilometres housing an array of wind turbines.

Features:

• Rotor shaft is horizontal and typically faced into the wind using a yaw mechanism.
• Usually has three blades, although two- and one-blade (not so common) designs exist.
• Mounted on tall towers to access stronger wind currents.

Advantages:

• High efficiency due to consistent orientation toward the wind.
• Proven technology with wide commercial use.
• Better performance at high wind speeds.

Disadvantages:

• Requires complex yaw systems.
• Needs tall towers and large clearances.
• Maintenance can be challenging due to height.

Applications:

• Utility-scale electricity generation onshore and offshore.

Vertical-Axis Wind Turbines (VAWT)

These turbines have a rotor shaft oriented vertically, allowing them to capture wind from any direction without the need of a yaw control.

Common Types:

• Darrieus turbine: Egg-beater shaped, uses aerodynamic lift.
• Savonius turbine: S-shaped, uses drag force.

Advantages:

• Simpler design: generator and gearbox can be placed at the base.
• No need to orient the turbine with the wind.
• Can operate in turbulent, urban environments.

Disadvantages:

• Generally lower efficiency than HAWTs.
• More wear due to cyclic stress.
• May need external power to start rotation.

Applications:

• Small-scale or urban installations.
• Remote or rugged environments with changing wind directions.

Offshore Wind Turbines

These are typically large horizontal-axis turbines installed in sea or ocean environments.

Features:

• Benefit from higher and more consistent wind speeds offshore.
• Mounted on fixed foundations (shallow waters) or floating platforms (deep waters).

Advantages:

• Higher energy output potential.
• No land use or noise concerns for nearby residents.

Disadvantages:

• High installation and maintenance costs.
• Requires specialized ships and equipment.
• Environmental challenges (corrosion, marine ecosystem impact).

Applications:

• Large-scale national grid contributions.
• Coastal or island regions.

Small Wind Turbines

These are compact turbines designed for individual homes, farms, or remote applications.

Features:

• Can be HAWT or VAWT.
• Rated below ~100 kW.
• Some are pole-mounted; others can be rooftop installations.

Advantages:

• Easy to install and maintain.
• Useful in off-grid or hybrid solar-wind systems.

Disadvantages:

• Output is limited.
• Heavily dependent on local wind conditions.

Applications:

• Residential or rural power supply.
• Supplementary energy in hybrid systems.

Wind Farm Design Considerations

Designing a wind farm is a complex task that involves engineering, environmental, economic, and logistical factors. The goal is to maximize energy production while minimizing costs and environmental impacts. Whether onshore or offshore, the following key elements must be carefully considered:

Wind Resource Assessment

• Purpose: Identify locations with sufficient and consistent wind.
• Methods:
  • On-site wind measurements using anemometers or LiDAR.
  • Analysis of historical wind data and satellite modelling.
• Key Metrics:
  • Average wind speed
  • Wind direction and variability
  • Turbulence intensity

Site Location and Terrain

• Flat open land, hilltops, or coastal areas are ideal for onshore farms.
• Offshore sites are chosen for higher wind speeds but involve greater costs.
• Obstacles (trees, buildings, hills) cause turbulence and reduce efficiency.
• Proximity to transmission lines, roads, and access infrastructure is crucial for installation and grid connection.

Turbine Spacing and Layout

• Turbines must be spaced to minimize wake effects (turbulent air behind each turbine) which reduce performance.
• General rule: turbines spaced 5–10 rotor diameters apart in the prevailing wind direction.
• Layout may follow:
  • Linear arrays (aligned with wind)
  • Grid patterns
  • Clustered groupings depending on land shape and wind direction

Environmental and Social Impact

• Environmental Impact Assessments (EIAs) are often legally required.
• Factors considered:
  • Impact on birds and bats
  • Noise pollution and shadow flicker
  • Land use and visual impact
  • Marine ecosystem effects for offshore farms
• Public consultation and local acceptance are key for project success.

Grid Connection and Infrastructure

• Wind farms must be connected to the electricity grid.
• Requires:
  • Substations and transformers to step up voltage
  • Cables (underground or overhead) to reach the grid
  • Grid stability and capacity analysis (can the local grid absorb the generated power?)

Turbine Selection

• Based on wind speed, air density, terrain, and energy goals.
• Considerations:
  • Rotor diameter
  • Rated power
  • Cut-in, rated, and cut-out wind speeds
• Offshore turbines are usually larger with higher power ratings.

Economic and Financial Feasibility

• Includes capital expenditure, operating costs, and return on investment.
• Influences:
  • Turbine cost
  • Installation and maintenance expenses
  • Expected capacity factor (actual output vs. maximum possible)
  • Government incentives, feed-in tariffs, or subsidies

Maintenance and Accessibility

• Planning for maintenance roads, service access, and monitoring systems is vital.
• Offshore turbines require specialized vessels and longer downtimes for repair.

Regulatory and Permitting Requirements

• Involves acquiring:
  • Land or sea use permits
  • Environmental clearance
  • Aviation and telecommunications approval (to avoid interference)
  • Construction and operational licenses

Conclusion

Wind energy plays a vital role in the global shift toward cleaner, more sustainable power systems. Understanding how wind turbines work, how to calculate their power output, and the challenges associated with their implementation provides valuable insight into this transformative technology. With continued advancements in design, control, and integration, wind power will remain a cornerstone of the renewable energy landscape for decades to come.

Oriyomi Oladele
Project Worker
B.Sc. (Physics), B.Eng. (Information Technology)

Essi Hauta
Expert, RDI
M.A. (Education)

References

Manwell, J.F., McGowan, J.G., & Rogers, A.L. (2010). Wind Energy Explained: Theory, Design and Application. Wiley.

How a Wind Turbine Works. https://www.energy.gov/articles/how-wind-turbine-works

Hau, E. (2013). Wind Turbines: Fundamentals, Technologies, Application, Economics. Springer.

Wind Turbines. https://www.e-education.psu.edu/emsc297/node/647

Wind Turbine Math and Physics. https://www.uti.edu/blog/wind-turbine/wind-turbine-math-physics

Ackermann, T. (Ed.). (2005). Wind Power in Power Systems. Wiley.

Energy Fundamentals. Physics of Wind Turbines. https://home.uni-leipzig.de/energy/energy-fundamentals/15.htm

How to calculate wind energy and wind turbine energy https://x-engineer.org/wind-turbine-energy/

EM SC 470: Applied Sustainability in Contemporary Culture. Wind Energy Power Calculations. https://www.e-education.psu.edu/emsc297/node/649

U.S. Department of Energy. How Do Wind Turbines Work. https://www.energy.gov/eere/wind/how-do-wind-turbines-work

Global Wind Energy Council (GWEC). (2024). Global Wind Report. https://gwec.net

Betz’s law. https://en.wikipedia.org/wiki/Betz%27s_law