What Technology Is Used In Wind Power?
Wind power is the use of air flow through wind turbines to generate electricity. Humans have harnessed wind power for centuries, initially using windmills to grind grain and pump water. The earliest known use of windmills dates back to Persia in the 7th century CE. Windmills then spread across the Middle East and Central Asia before arriving in Europe by the 11th century. In the late 19th century, wind turbines began generating electricity, marking the true beginnings of modern wind power.
The importance of wind power has grown tremendously in recent decades. As concerns over climate change and fossil fuel dependence rise, renewable energy sources like wind and solar have become increasingly critical. Wind power in particular offers an abundant, clean energy source that avoids greenhouse gas emissions. Today, wind provides nearly 20% of electricity generation in the European Union. Global wind capacity has expanded over 25 times in the last two decades. Wind power will continue playing a vital role in the world’s renewable energy future.
Sources:
European Use of Wind Power – Electricity & Alternative Energy
An Overview for Wind Energy Technology for Electricity
Wind Turbine Components
The main components of a wind turbine are the rotor, nacelle, tower, and foundation [1]. The rotor is comprised of the blades and hub, and sits atop the nacelle at the top of the tower. The nacelle contains the mechanical and electrical components necessary to convert the kinetic energy of the wind into electrical energy [2].
The rotor blades capture the wind energy and transform it into rotational motion to turn the main shaft. Most modern wind turbines have three rotor blades made of fiberglass or carbon fiber. The blades can be up to 90 meters long. The hub connects the blades to the main shaft and allows their pitch to be adjusted to control power output.
The nacelle sits atop the tower and contains the gearbox, brake, generator, controller, and yaw system. The nacelle cover protects these components from the elements. The gearbox increases the rotational speed from the main shaft to the level required by the generator to produce electricity. The generator uses magnetic fields to convert the rotational energy into electrical energy.
The tower supports the nacelle and rotor. Towers are made of tubular steel, concrete, or steel lattice. Utility-scale turbines have tower heights ranging from 80-140 meters. The tower foundation anchors the turbine in the ground, typically using concrete and steel rebar.
Turbine Size and Capacity
Wind turbines come in a variety of sizes and power generation capacities. Turbines are typically categorized as small, medium or large based on power output.
Small turbines range from 20 kW to 100 kW. They typically have tower heights up to 30 meters and rotor diameters up to 15 meters. Small turbines are often used for residential, farm, and small business applications 1.
Medium sized turbines generate between 250 kW to 1 MW of power. They generally have tower heights around 50 meters and rotor diameters between 40-60 meters. Medium turbines are utilized for small businesses, schools and some utilities 2.
Large utility-scale turbines start at around 2.5 MW capacity, with many modern turbines exceeding 4 MW. Tower heights are commonly 80-120 meters tall, with rotor diameters exceeding 120 meters. These massive turbines are designed for utility-scale wind farms and offshore wind projects.
Horizontal vs. Vertical Axis
Wind turbines come in two main designs – horizontal axis and vertical axis turbines. The difference lies in the orientation of the rotating axis with respect to the ground.
Horizontal axis turbines have their rotating axis parallel to the ground. The blades face into the wind directly as the turbine spins on its horizontal axis. This is the more common design used in large-scale wind farms. Pros of horizontal axis turbines include high efficiency, self-starting capabilities, and low torque ripple. However, they do require a yaw control mechanism to keep them facing the wind.
Vertical axis turbines have the rotating axis perpendicular to the ground and wind direction. The most common type is the Darrieus design with curved blades that generate lift as they spin. Pros of vertical turbines include omnidirectional operation without a yaw mechanism and accessibility of generator/gearbox on ground level. Cons are lower efficiency than horizontal turbines and difficulty self-starting.
Overall, horizontal axis turbines are better suited for utility-scale wind farms due to their higher efficiency and power output. Vertical turbines may be advantageous for niche applications like rooftop mounting where omnidirectional operation is beneficial.
Generators
Wind turbines generate electricity through the use of large generators housed inside the nacelle, or hub, at the top of the tower. The most common types of generators used in modern wind turbines are induction generators and permanent magnet synchronous generators.[1]
Induction generators are simple, rugged, and well-tested, making them a common choice for most wind turbine applications. They generate power from the rotation of the turbine rotor, working together with the power grid frequency to generate alternating current electricity.[1] Permanent magnet generators are more complex but can be more efficient. They use permanent magnets rather than an external voltage source to generate electricity.[2]
Some wind turbines also use direct drive generators, which eliminate the gearbox and connect the rotor directly to the generator. This improves reliability but requires larger generators.[2] Regardless of generator type, modern wind turbines utilize advanced power electronics to optimize energy output.
Sources:
[1] https://www.energy.gov/eere/wind/how-do-wind-turbines-work
[2] https://windandsolar.com/wind-turbine-kits/
Gearbox
The gearbox is a critical component in a wind turbine drivetrain. Its purpose is to increase the rotational speed from the turbine rotor to the generator. Most wind turbines operate at between 6-20 rpm, while a generator requires rotational speeds of 1000-1800 rpm to produce electricity efficiently (Source 1). Gearboxes allow this increase in rpm to match the generator’s optimum operating speed.
The most common type of gearbox used in large turbines is the planetary gearbox. Planetary gearing uses a sun gear surrounded by multiple planet gears which then drive a ring gear. This arrangement provides the high gear ratios needed for wind turbines in a compact and efficient design. Planetary gearboxes can achieve over 100:1 gear ratios in just a few stages (Source 2). Other gearbox types like parallel shaft and spur gears are also sometimes used.
The gearbox experiences very high torque loads from the rotor, so must be extremely robust. Gearbox reliability and maintenance is critical as gearbox replacement is one of the most expensive turbine maintenance tasks.
Blades
The blades of a wind turbine are one of the most important components. They capture the wind energy and convert it into rotational motion to turn the generator. The shape and design of the blades have a significant impact on the turbine’s efficiency and power output.
Most modern wind turbine blades have a curved, airfoil design similar to airplane wings. This allows them to generate lift and turn the rotor. The outer parts of the blade are generally wider to capture more wind, while the inner parts are narrower. Blades are made of strong, lightweight materials like fiberglass, carbon fiber or wood epoxy composites. Composite materials allow the blade shape to be precisely engineered for optimal aerodynamic performance (1).
Researchers are exploring innovative new blade shapes and adaptations. A recent advancement is bend-twist coupled blades, which passively adjust their angle to reduce drag when wind speeds get too high. Flat back blade edges have also been shown to improve efficiency. Vortex generators added to the surface can optimize airflow. Improved computer modeling and wind tunnel testing enables manufacturers to fine-tune blade designs (1).
The number, length and shape of blades are customized for the turbine size and site wind conditions. Finding the optimal balance of aerodynamics, structure and efficiency is an active area of wind power research and development.
Control Systems
Modern wind turbines use advanced control systems to optimize performance and maximize power output. The two main control systems are yaw control and blade pitch control.
Yaw control turns the turbine to face into the wind. Wind direction sensors on the turbine measure wind direction continuously and send signals to the yaw drive to turn the turbine. Hydraulic motors or electric drives rotate the nacelle to keep the turbine facing into the wind.
Blade pitch control adjusts the angle or pitch of the blades to control rotor speed. Anemometers on the turbine measure wind speed and feed data to the turbine control system. When wind speeds get too high, the blades are pitched slightly out of the wind to reduce rotor speed and maintain control. Pitch control also optimizes the angle of attack for maximum aerodynamic efficiency.
Modern wind turbines also use a variety of sensors to monitor operations. These include wind speed sensors, wind direction sensors, temperature sensors, position sensors on components, vibration sensors, and power output sensors. The data is fed to controllers that can adjust operations for optimal performance and safety. For example, the turbine can be shut down if vibration levels get too high.
According to the U.S. Department of Energy’s National Renewable Energy Laboratory, advanced control systems can capture up to 10% more energy than conventional systems (https://www.nrel.gov/wind/controls-analysis.html). Continued innovation in wind turbine control algorithms, sensors, and actuators will further enhance performance and reliability.
Maintenance
Regular maintenance is crucial for keeping wind turbines functioning properly and maximizing their productivity. There are two main types of maintenance performed on wind turbines: preventive and corrective. Preventive maintenance involves scheduled inspections and service tasks to detect and prevent failures before they occur. This includes activities like lubricating parts, tightening bolts, replacing worn components, and testing control systems and sensors. Preventive maintenance is typically performed 1-2 times per year.
Corrective maintenance involves repairs made after a failure or breakdown occurs. This includes activities like replacing broken parts, fixing electrical and mechanical issues, and troubleshooting problems that arise unexpectedly. Corrective maintenance may require taking the turbine out of service until repairs can be made. Having strong preventive maintenance practices helps minimize the need for corrective maintenance. Both types of maintenance are critical for maximizing turbine availability, power production, and lifetime.
Accessing turbines for maintenance can be challenging as many are located in remote areas and tower heights often exceed 250 feet. Service technicians use trucks equipped with cranes and lifts to access turbine components. More maintenance is typically required as a turbine ages past 10 years. The level of maintenance needs varies by turbine design, climate, and location. Careful monitoring and upkeep are essential for maximizing wind power assets.
Future Trends
The wind industry is continuously innovating and developing new technologies to improve efficiency and lower costs. Some key emerging technologies and innovations include:
- Larger turbines – New turbines are getting increasingly larger, with rotor diameters over 200 meters and capacities over 10 MW. Larger turbines can capture more wind energy.
- Taller towers – Taller towers, over 100 meters high, allow access to stronger and more consistent winds.
- Floating offshore wind – Floating offshore wind farms are being developed that can access excellent wind resources further offshore in deep waters where foundations are not feasible.
- Smart rotors – Smart turbine blades can adjust their shape to optimize power production as wind conditions change.
- Superconducting generators – Superconducting generator materials allow lighter and more powerful generators.
- Drones and sensors – Advanced monitoring with drones and sensors improves turbine performance.
- Energy storage – Integrating storage, like batteries, enables capturing surplus energy for later use.
Advancements in materials, data analytics, forecasting, and control systems will also continue to improve reliability and optimize wind farms. While upfront costs are still decreasing, technology innovations will be key for harnessing the enormous potential of wind power.
