What Are The Requirements For A Wind Turbine?

Wind turbines are renewable energy systems that convert the kinetic energy of wind into electrical energy. They play a vital role in generating clean, emissions-free power around the world. The basic purpose of a wind turbine is to capture wind to spin large blades connected to a generator that produces electricity. This article will provide an overview of the key requirements and considerations involved in designing, building, and operating a wind turbine.

Table of Contents

Siting Requirements

Wind turbines need to be sited in locations with optimal wind conditions to maximize energy production. Ideal sites will have the following characteristics:

Open areas – Wind turbines require unobstructed wind flow, so they should be placed in open fields, shorelines, or mountain passes rather than forests or cities where buildings and trees can block the wind.

Consistent winds – Sites with steady wind speeds around 10-20 mph are best. Locations with frequent lulls will produce less consistent power output.
Elevation – Higher elevations are better as wind speeds tend to increase with height. Ridgelines and hilltops make good turbine sites.
Space – Each turbine needs adequate spacing from other turbines, structures, and property lines to reduce turbulence and ensure proper operation.

When siting wind projects, it’s also important to consider factors like access to transmission lines, community acceptance, and minimizing impacts to wildlife. Proper site selection is crucial to maximize power production and return on investment.

Wind Speed

Wind turbines require specific wind speed ranges to operate efficiently. There are three key wind speeds to consider:

Minimum wind speed – This is the lowest wind speed at which the turbine will start to rotate and generate electricity. This is typically around 7-9 mph. Below this speed, the wind does not provide enough force to overcome inertia and friction and spin the blades.

Rated wind speed – This is the optimum wind speed where the turbine reaches its maximum power output, usually around 30-35 mph. At this speed, the turbine generates its full rated capacity.

Cut-out wind speed – This is the maximum wind speed the turbine is designed to withstand, usually around 55-80 mph. Above this speed, the turbine automatically shuts down to prevent damage from extremely high winds.

Wind turbines are designed to operate most efficiently within the wind speed range between the minimum and rated speeds. By carefully selecting turbine models matched to the average wind speeds in a location, wind farms can maximize power generation. Understanding these key wind speed parameters is critical when siting and specifying turbines.

Height

The height of a wind turbine is a crucial factor in harnessing the most energy from the wind. Wind speeds increase with height above the ground due to less surface drag from vegetation and landscape. Taller towers allow access to faster, less turbulent wind, resulting in increased energy production.

According to wind resource assessments, wind speeds are lowest near the surface and reach their maximum speeds at around 80 meters (262 feet) of elevation. Most modern utility-scale wind turbines have tower heights in the range of 60-120 meters (197-394 feet). The turbine’s hub height should be high enough to clear any obstacles or surface roughness elements near the wind farm.

In addition to tower height, the length of the turbine blades plays a role. Longer blades can sweep a larger rotor area to harness more wind energy. However, the blades need to remain structurally sound. Most commercial megawatt-scale turbines have rotor diameters between 70-130 meters (230-425 feet). The ratio of total height to rotor diameter is optimized to extract the most energy from the wind flowing past the site.

Requirements for Wind Turbine Materials

Wind turbines are exposed to extreme weather conditions and must be constructed from durable materials. The most common materials used are:

Fiberglass – The blades are often made of fiberglass reinforced polyester or epoxy. Fiberglass is lightweight, strong, and flexible, which allows the blades to capture the most wind energy. It resists weathering from rain, snow, ice, and UV radiation.

Steel – The towers are primarily constructed from tubular steel. Steel provides the necessary strength to support the turbine and withstand high winds. Steel towers are also relatively easy to transport and construct onsite.

Aluminum – Some turbine components like the rotor hub and nacelle cover may use aluminum for its light weight, strength, and corrosion resistance. Aluminum can withstand the high winds without adding too much weight.

Concrete – The turbine foundations are made from steel-reinforced concrete to provide stability and support for the tower base. Concrete holds up well over decades exposed to the elements.

Other advanced materials like carbon fiber and kevlar are sometimes used. But fiberglass, steel, aluminum, and concrete comprise most of a wind turbine’s materials to ensure it survives years of harsh weather conditions.

Mechanical Components

Wind turbines contain a variety of mechanical components that work together to convert the kinetic energy of the wind into electrical energy. The main mechanical components include:

Rotor

The rotor is comprised of two or three blades attached to a central hub. The blades are shaped such that when the wind blows, lift is created and the rotor spins. Most modern wind turbine rotors are constructed of fiberglass infused with epoxy or vinyl ester resins. The rotor connects to the main shaft, which turns a series of gears to spin the generator.

Gearbox

The gearbox is responsible for increasing the rotational speed from the rotor to the generator. Most turbines use a gearbox to convert the rotor’s low rotational speed to speeds of about 1000 – 1800 rpm to drive the generator. Gearboxes enable the generator to operate at an optimum speed regardless of rotor speed.

Generator

The generator uses electromagnetic induction to convert the rotational mechanical energy from the rotor into electrical energy. Most commercial wind turbines use asynchronous generators containing magnets that rotate past wire coils to generate current. The power output is transformed and transmitted to the grid.

Brake

A brake system is critical to stop and secure the rotor in emergency situations and for maintenance. Common braking methods include pitch control, rotor blades with aerodynamic brakes, and a mechanical disc brake which can hold the shaft stationary.

Electrical Systems

Electricity generation is the primary purpose of wind turbines. The electrical systems convert the mechanical rotation of the turbine blades into electrical power that can be fed into the grid. Here are the key electrical components:

Cables – Insulated copper cables connect the various electrical components and carry power down the turbine tower to the base. Cables must be properly shielded and grounded to prevent interference and ensure safety.

Generator – The generator uses electromagnetic induction to convert the rotational energy of the turbine shaft into electrical energy. Common generator types are asynchronous generators and synchronous generators.

Power converter – Most turbines use a power converter to change the wild AC from the generator into grid-compliant AC power. The converter consists of a rectifier, inverter, and transformer.

Transformers – Transformers are used to step up the generator output voltage to higher transmission voltages (like 110 kV). This minimizes losses over long cable runs to the grid connection point.

Switchgear – Switchgear and protection relays safeguard the electrical systems and personnel. Features include integrated fuses, circuit breakers, surge protection, and grounding systems.

Proper electrical design is critical for extracting maximum power, complying with grid requirements, ensuring safety, and facilitating maintenance. The electricity produced by the wind turbine can vary based on wind speeds. So the electrical components must be able to handle those fluctuations.

Controls

Control systems are critical components of wind turbines. They allow the turbine to start up, shut down, and optimize its performance and efficiency by responding to changing wind speeds and directions. The most important control systems in a wind turbine are:

Yaw control – actively turns the turbine to face into the wind.

Pitch control – adjusts the angle of the blades to maintain optimal rotational speed.
Braking control – slows the rotor for shutdown or in high winds.
Generator torque control – modulates power output and rotor speed.

Modern wind turbines use advanced computerized control systems to monitor wind speed, generator speed and power output. The controllers can turn the machine on and off, adjust blade pitch and yaw, and apply brakes to the rotor. This allows the turbine to operate at maximum efficiency across a wide range of wind speeds. The control system is also critical for safe shutdown in high winds.

Reliable and precise electronic controllers are essential for optimizing energy capture, reducing mechanical stresses, and preventing damage to turbine components. As wind turbine sizes continue to increase, the complexity and capabilities of control systems will be an important focus of technological innovation.

Maintenance

Wind turbines have many mechanical components that require regular maintenance to ensure they operate properly. Some key maintenance activities include:

Lubricating parts like the gearbox, generator, and bearings
Checking and changing oils and filters
Inspecting and replacing parts like blades, brakes, sensors, and cables

Cleaning equipment and removing debris or ice buildup
Testing pitch and yaw systems
Checking bolts and fasteners for tightness

Verifying software and control systems are updated

The turbine manufacturer provides maintenance manuals with schedules that dictate the frequency of these tasks. Maintenance crews should closely follow these schedules and log all activities. Catching small problems early prevents more expensive repairs down the road.

Some components may require replacement every few years. Planning ahead for these major overhauls and having spare parts available is crucial. Proper maintenance maximizes turbine availability, energy production, and return on investment.

Safety Systems

Wind turbines are equipped with various safety systems to protect equipment, wildlife, and people. This includes:

Lightning protection – Wind turbines have a lightning protection system to direct lightning strikes safely to the ground. This protects sensitive electronics from damage.
Fire prevention – Sensors monitor temperature inside the nacelle housing and automatically activate fire suppression systems if needed. This prevents fires from spreading.

Overspeed sensors – These monitor the rotor speed and apply brakes if the winds become too strong. This prevents damage from excess speeds.
Pitch control – The turbine blades can be pitched or turned parallel to the wind to regulate speed in high winds. This also acts as a braking system.
Mechanical brakes – Disc brakes are built into the drivetrain and rotor to stop the blades from turning when needed.

Obstacle lighting – Red flashing aviation warning lights are installed on the nacelle to alert aircraft.
Wildlife sensors – Some turbines use automated wildlife detection such as radar, infrared, or visual systems. This can trigger deterrents or brief shut downs when animals approach.