SME 2512: WIND TURBINE 1 1.0 Wind Turbine

Wind turbine or wind power developed as an alternative to fossil fuels, plenty and no

cost sources, renewable, widely distributed, clean, produces no greenhouse gas

emissions during operation and uses little land to generate electricity.

2.0 History

Wind turbine is a device that converts kinetic energy from the wind or is called wind

energy. Wind turbine was developed from the windmills, which were to use for

agricultural industries. Later in years of researches and development, Scottish

academic Prof. James Blyth from Scotland was believed to be the first to built the

wind turbine in July 1887.

2.1 Invention Chronology

634-44M : Persian was first to build a mill operated by wind and introduced the

system to Caliph Umar. Later, wind power was widely used to run

both millstones for grinding corn and to draw up water for

irrigation. The walls of the lower chamber were pierced by four

vents as to direct the wind to the sails and can increase its speed.

Figure 2.0: A millstone attached to end of a wooden cylinder, standing vertically in a tower open on the northeast side to catch the wind.

WIND TURBINE 2 9th Century : Windmill later developed by Islamic Engineers to improve husking,

paper, textile and sugarcane industries in Iran, Afghanistan and

Pakistan. By manipulating the wind speed at that times (reaching

120km/hour) the windmills have been constructed perpendiculr to

the wind flow to maximize output. Generally constructed out of

clay, straw and wood.

1887-88 : Charles F. Brush produced electricity using a wind powered

generator for powered his house and laboratory.

1890 : Danish (scientist) and Poul la Cour (inventor) constructed wind

turbines to generate electricity, which was used to produce hydrogen

and oxygen by electrolysis and mixture of the two gases was stored

for use as a fuel.

Figure 2.1: Each of the windmills consists of 8 rotating chambers with each chamber housing 6 vertical blades. Once the chambers begin rotating by the force of the wind, it results in the turning of the windmills main axle which was in turn is connected to grain grinders.

Figure 2.2: It was 60 feet tall with a diameter of 56 feet, weighed 80,000 pounds and had a 12kW dynamo.

SME 2512: WIND TURBINE 3 1904 : La Cour founded the Society of Wind Electricians was the first

discover that fast rotating wind turbines with fewer rotor blades

were the most efficient in generating electricity.

Mid-1920s : Wind generators developed by company Parris-Dunn to produced 1-

3kW.

1975 : NASA wind turbines project built thirteen experimental tubines

which paved the way for much of the technology used today.

Since then, wind turbines have increased greatly in size with the Enercon E-126

capable of delivering up to 7.5 MW.

2.2 Improvement

The windmill designs evoke the current wind turbines. From Middle Easterns

traditional mills technologies brought to Europe by Arabic Geographers. The ideas

continue with amount of researches including increasing the size of a wind turbines

blades; making the tower taller, allow a turbine to capture more wind, even at low

speeds. The basic design specification guaranteed endless power source and the availability has been improved by drawings, dimensions, environmental factors,

ergonomic factors, aesthetic factors, cost, maintenance that will be needed, quality

and safety which will be further discuss in the next chapters. With the data it is

possible to develop commercial viability.

2.3 Types and Design

In the chronology, it was clearly shown that windmills divided to 2 types except for

the 9th centurys model that combined both. Current wind turbines in the market

divided into two types of rotation:

a. horizontal axis and

b. vertical axis.

WIND TURBINE 4 2.3.1 Horizontal Axis

Horizontal Axis Wind Turbine (HAWT) has the main rotor shaft

and electrical generator at the top of a tower, and may be pointed into

or out of the wind. Most have a gearbox, which turns the slow rotation

of the blades into a quicker rotation that is more suitable to drive an

electrical generator.

Average wind speeds required for grid connected applications about of

5 meters per second or 11mph. Annual average wind speeds of 3 to 4

m/s or 7-9 mph may be adequate for non-connected electrical and

mechanical applications such as battery charging and water pumping.

In this report, HAWT will be the main focus instead of VAWT.

2.3.2 Vertical Axis

Vertical Axis Wind Turbine (VAWT) where the main rotor shaft is

set vertically and the main components are located at the base of the

turbine.

Figure 2.3.1: Featured in tall mass with minimal numbers of blades and nacelle at the top.

Figure 2.3.2: The blades are vertical and consist of two hubs.

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3.0 Components and Functionality

A horizontal wind turbine is consist of three (3) main components; Rotor,

Gear Box and Generator; to generate electricity through kinetic from the wind

energy.

3.1 Blades

a. The lifting style wind turbine blade. These are the most efficiently designed,

especially for capturing energy of strong, fast winds. Some European

companies actually manufacture a single blade turbine.

b. The drag style wind turbine blade, most popularly used for water mills, as seen

in the Old Dutch windmills. The blades are flattened plates, which catch the

wind. These are poorly designed for capturing the energy of heightened

winds.

3.2 Rotor

The rotor is Aerodynamics design to capture the maximum surface area of wind in

order to spin the most ergonomically. The blades are lightweight, durable and

corrosion-resistant material. The best are composites of fiberglass and reinforced

plastic.

Figure 3.0: For high power wind turbines, double-fed asynchronous generators are most frequently used. The operating rotation speed can be varied somewhat, unlike when using conventional asynchronous generators. Another concept uses synchronous generators. A grid connection of synchronous generators is only possible via transformers, due to the fixed rotation behavior.

WIND TURBINE 6 3.3 Gearbox

Magnifies or amplifies the energy output of the rotor. The gearbox situated directly

between the rotor and the generator. A rotor rotates the generator (which is protected

by a nacelle), as directed by the tail vane.

3.4 Generator

Generator produced electricity from the rotation of the rotor. It is comes in various

sizes, relative to the output you wish to generate. The nacelle is the housing or

encloses that seals and protects the generator and gearbox from the elements. It is

easily removed for maintenance of the wind.

SME 2512: WIND TURBINE 7 4.0 Product Specification

This chapter discusses further breakdown specification required for a horizontal wind

turbine.

4.1 Weight

For 1.5MW wind turbine, the tower is at 80 meters high, the rotor assembly weight is

22,000 kg, the nacelle, which contains the generator component weight, is 52,000 kg.

The concrete base tower is constructed using 26,000 kg of reinforcing and contains

190 m3 of concrete. The base is 15 m diameter and 2.4 m thick near the center.

4.2 Ergonomic

A horizontal wind turbine does not have any direct connection with human. So the

ergonomic aspect of the built only focused on the rotor blades to harvest more wind.

The ratio between the speed of the blade tips and the speed of the wind is called tip

speed ratio. High efficiency 3-blade-turbines has tip speed/wind speed ratios of 6 to 7.

Modern wind turbines are designed to spin at varying speeds. Operating closer to their

optimal tip speed ratio during energetic gusts of wind allows wind turbines to improve

energy capture from sudden gusts that are typical in urban settings.

In contrast, older style wind turbines were designed with heavier steel blades, which

have higher inertia, and rotated at speeds governed by the AC frequency of the power

lines. The speed and torque at which a wind turbine rotates must be controlled for

several reasons:

To optimize the aerodynamic efficiency of the rotor in light winds.

To keep the generator within its speed and torque limits.

To keep the rotor and hub within centrifugal force limits. The centrifugal force

from the spinning rotors increases as the square of the rotation speed, which

makes this structure sensitive to over speed.

To keep the rotor and tower within strength limits. Because the power of the

wind increases as the cube of the wind speed, turbines have to be built to

survive much higher wind loads (such as gusts of wind) than those from which

WIND TURBINE 8 they can practically generate power. Since the blades generate more torsion

and vertical forces (putting far greater stress on the tower and nacelle due to

the tendency of the rotor to precess and nutate) when they are producing

torque, most wind turbines have ways of reducing torque in high winds.

To enable maintenance. Since it is dangerous to have people working on a

wind turbine while it is active, it is sometimes necessary to bring a turbine to a

full stop.

To reduce noise. As a rule of thumb, the noise from a wind turbine increases

with the fifth power of the relative wind speed (as seen from the moving tip of

the blades). In noise-sensitive environments, the tip speed can be limited to

approximately 60 m/s (200 ft/s).

Noise generated from the rotor blades is the only impact to human. It is generally

understood that noise increases with higher blade tip speeds. To increase tip speed

without increasing noise would allow reduction the torque into the gearbox and

generator and reduce overall structural loads, thereby reducing cost. The reduction of

noise is linked to the detailed aerodynamics of the blades, especially factors that

reduce abrupt stalling. The inability to predict stall restricts the development of

aggressive aerodynamic concepts. The wind turbine generates 150dB that is

equivalent to a lawn motor and recommended to be built at least 500m away from any

residential.

4.3 Material

Figure 4.0:Material of the horizontal blade.

SME 2512: WIND TURBINE 9

4.3.1 Tower & Foundation

Tubular construction of concrete or steel is used. An alternative to this

is the lattice tower form. Its manufactured in several individual tower

section connected using stress-reducing L-flanges.

4.3.2 Nacella

Cover housing that houses all the generating components in a wind

turbine including generator, gearbox, drive train and brake assembly.

4.3.3 Rotor blades

The rotor blades are mainly made of glass fibre or carbon reinforced

plastics (GRP, CFRP). The blade profile is similar to an aeroplane

wing.

4.4 Safety

Operation of any utility-scale energy conversion system presents safety hazards. Wind

turbines do not consume fuel or produce pollution during normal operation, but still

have hazards associated with their operation.

If a turbine's brake fails, the turbine can spin freely until it disintegrates or catches

fire. This is rare and the odds of a major turbine fire or disintegration is in the order of

0.001% over the 20-25 year lifespan of a modern wind turbine. Some turbine nacelle

fires cannot be extinguished because of their height, and are sometimes left to burn

themselves out. In such cases they generate toxic fumes and can cause secondary fires

below. However, newer wind turbines are built with automatic fire extinguishing

systems similar to those provided for jet aircraft engines.

During winter ice may form on turbine blades and subsequently be thrown off during

operation. This is a potential safety hazard, and has led to localized shutdowns of

turbines. Modern turbines can detect ice formation and excess vibration during

operations, and are shut down automatically. Electronic controllers and safety sub-

systems monitor many different aspects of the turbine, generator, tower, and

environment to determine if the turbine is operating in a safe manner within

prescribed limits. These systems can temporarily shut down the turbine due to high

WIND TURBINE 10 wind, ice, electrical load imbalance, vibration, and other problems. Recurring or

significant problems cause a system lockout and notify an engineer for inspection and

repair. In addition, most systems include multiple passive safety systems that stop

operation even if the electronic controller fails.

4.5 Product Reliability

The lifespan of a modern turbine is around 120,000 hours or 20-25 years, however,

they are not maintenance free. As they contain moving components, some parts will

need to be replaced during their working life. Throughout research, the cost of

maintenance and parts replacement is around the 1-cent USD/AU per kWh or 1.5 to 2

percent annually of the original turbine cost.

The components of a wind turbine are typically designed to remain operational for

twenty years. It would be quite easy, and hardly any more expensive to design and

build some of the components to remain operational for far longer. However, because

most of the major components would be very expensive to build for a longer life span,

it would be a waste to have a whole turbine standing idle because one part failed years

earlier than the rest.

By agreeing on a twenty-year design lifetime, an economic compromise is met which

guides the engineers who develop new components for wind turbines. When planning

new components they know that it will be expected to work reliably for two decades.

They have to show that their planned components will have little chance of failing

within twenty years of installation.

The design lifetime of a component compared to its actual lifetime means that a wind

turbine can last far longer than originally planned. How long it will continue working

depends on the build quality of all of the turbine components, how well put together

and the local environmental conditions. Environment isn't just the wind factors, like

how much turbulence is experienced at the site, but also the air density, average

humidity, even seismic factors.

An offshore turbine may last longer, simply due to the fact that with no obstacles to

the wind there is lower turbulence at sea. This would in turn result in lower

maintenance costs, but this would be balanced by the increased cost in accessing the

turbine to effect any maintenance.

SME 2512: WIND TURBINE 11 4.6 Production

Wind turbines for commercial electricity production usual range from 100 kilowatts

to 5 megawatts. At the time of writing, the largest wind turbine in the world had a

rotor diameter of 126 m (390 feet) and the potential to generate enough electricity for

5000 households. For a 600 kW turbine, the average output is between 1.5 and 2

GW/h per year, depending on wind speed. For every kilowatt-hour of electricity

produced by wind energy or other green means, approximately 1.5 pounds of carbon

is prevented from going into the atmosphere if that electricity had been sourced from

coal fired power plants.

WIND TURBINE 12 5.0 Photos & Sketches

SME 2512: WIND TURBINE 13 6.0 Material & Production

1. Foundation

2. Tower

3. Nacelle

4. Rotor Blade

5. Hub

6. Transformer ( Dost not a part of wind turbine)

WIND TURBINE 14