wind turbines

Wind Turbineshttps://pursuitengineering.blogspot.com/2017/02/wind-

turbines.html

• A wind turbine works the opposite of a fan

• wind turbines use wind to make electricity.

• The wind turns the blades, which spin a shaft, which connects to a

generator and makes electricity.

• Wind turbines convert the kinetic energy in the wind into mechanical

power.

• This mechanical power can be used for specific tasks (such as grinding grain

or pumping water) or a generator can convert this mechanical power into

electricity.

• If the mechanical energy is then converted to electricity, the machine is

called a wind generator.

Types of Wind Turbines

Wind turbines are classified into two general types

• Horizontal axis• Vertical axis

A horizontal axis machine has its blades rotating on an axis parallel to the ground

A vertical axis machine has its blades rotating on an axis perpendicular to the ground

Horizontal-axis wind turbines (HAWT)

Theses wind turbines typically either have two or three

blades. These three-bladed wind turbines are operated

"upwind," with the blades facing into the wind.

Horizontal-axis wind turbines (HAWT)

Up-Wind Turbines

Some wind turbines are designed to

operate in an upwind mode (with the

blades upwind of the tower). Large

wind turbines use a motor-driven

mechanism that turns the machine in

response to a wind direc tion. Smaller

wind turbines use a tail vane to keep

the blades facing into the wind

Horizontal-axis wind turbines (HAWT)

Down-Wind Turbines

Other wind turbines operate in

a downwind mode so that the

wind passes the tower before

striking the blades. Without a

tail vane, the machine rotor

naturally tracks the wind in a

downwind mode.

Horizontal-axis wind turbines (HAWT)

Shrouded Wind Turbines

Some turbines have an added structural design feature called an augmentor. The augmentor is intended to increase the amount of wind passing through the blades.

Vertical-axis wind turbines (VAWT)

Vertical-axis wind turbines (VAWT)

Savonius Wind Turbine

The Savonius turbine is S-shaped if

viewed from above. This drag-type

VAWT turns relatively slowly, but yields

a high torque. It is useful for grinding

grain, pumping water, and many other

tasks, but its slow rotational speeds

make it unsuitable for generating

electricity on a large-scale

Vertical-axis wind turbines (VAWT)

Flapping Panel Wind Turbine

This illustration shows the wind coming from one direction, but the wind can actually come from any direction and the wind turbine will work the same way

Vertical-axis wind turbines (VAWT)

Darrieus Wind Turbine

The Darrieus turbine is the most famous vertical axis wind turbone. It is characterized by its C-shaped rotor blades which give it its eggbeater appear ance. It is normally built with two or three blades.

Vertical-axis wind turbines (VAWT)

Giromill Wind Turbine

The giromill is typically powered by two or three vertical aerofoil’s attached to the central mast by horizontal supports. Giromill turbines work well in turbulent wind conditions and are an affordable option where a standard horizontal axis windmill type turbine is unsuitable

Parts of a Wind Turbine

• The nacelle contains the key components of the wind turbine, including the gearbox, and the electrical generator.

• The tower of the wind turbine carries the nacelle and the rotor. Generally, it is an advantage to have a high tower, since wind speeds increase farther away from the ground.

• The rotor blades capture wind energy and transfer its power to the rotor hub.

• The generator converts the mechanical energy of the rotating shaft to electrical energy

• The gearbox increases the rotational speed of the shaft for the generator

Installing a Wind Turbine

• The basic steps for installing a small wind turbine on your property are:

• Determine whether the wind resource in your area makes a small wind system economical.

• Determine your household electricity needs by checking your monthly or yearly electricity usage.

• Find out whether local zoning ordinances allow wind turbine installations.

• Purchase and install a wind turbine sized to the needs of your household.

Siting a Wind Farm

• Winds Minimum class 4 desired for utility-scale wind farm (>7 m/s at hub height)

• Transmission Distance, voltage excess capacity

• Permit approval Land-use compatibility Public acceptance Visual, noise, and bird impacts are biggest concern

• Land area Economies of scale in construction Number of landowners

Advantages of Wind Power

• Environmental• Economic Development• Fuel Diversity & Conservation• Cost Stability• small project size• Short/flexible development time • Dispatch ability

Disadvantages

• Generally remote location • Grid connectivity -- lack of transmission capability • Intermittent output only when the wind blows • Low capacity factor• Birds of Prey (hawks, owls, golden eagles) in jeopardy • Shutting down all the turbines for at least two months

each winter• Replace all before permits expire in 13 years

Wind Energy and Power

Atmospheric pressure differences accelerate and impart kinetic energy into the air

Wind energy conversion machines (WEC) convert wind energy into electrical or mechanical forms

How much power can we extract?

Wind Energy Natural Characteristics

• Wind Speed

Wind energy increases with the cube of the wind speed 10% increase in wind speed translates into 30% more electricity

2X the wind speed translates into 8X the electricity

Wind energy increases with height to the 1/7 power2X the height translates into 10.4% more electricity

• Air density

Wind energy increases proportionally with air density

Humid climates have greater air density than dry climates

Lower elevations have greater air density than higher elevations

Wind energy in Denver about 6% less than at sea level Blade swept area

Wind energy increases proportionally with swept area of the blades

• Blades are shaped like airplane wings10% increase in swept diameter translates into 21% greater swept area

Longest blades up to 413 feet in diameter, resulting in 600 foot total height

• Height

Wind energy increases with height to the 1/7 power

2X the height translates into 10.4% more electricity