scofieldgoldteam.weebly.com · Web viewWind Energy Source: A wind turbine transforms the kinetic energy of the wind into electrical energy. Wind turbines can range in size from small

Read and annotate this article

Highlight the keywords in each paragraph

Identify the main idea for each paragraph in the margins

Circle any new vocabulary or scientific terms that you need to

understand. Look them up and jot notes in the margins.

Use information from this article for your research

Wind EnergySource: http://www.stelr.org.au/wind-energy/

A wind turbine transforms the kinetic energy of the wind into electrical energy. Wind

turbines can range in size from small ones installed on large yachts and buildings, to

giant ones like those shown in Figures 1 and 2.

A wind farm is a set of wind turbines that are linked together to supply electricity to a

local community or to an electricity grid for a larger population. Wind farms are often

located along coastlines where the winds are strong.

The purpose of a wind turbine is to convert kinetic energy (energy of a moving mass) of

the wind into electrical energy. Energy conversion is common to all machines because

they must obey the law of conservation of energy—energy cannot be created or

destroyed, but only changed from one form to another or moved from one location to

another. For example, your car converts the chemical energy stored in fuel (if it’s an

electric car, batteries) to kinetic energy, moving it down the road. A wind turbine also

obeys this law when it extracts the kinetic energy in the wind and converts most of it to

1

electrical energy, and the remaining original kinetic energy becomes sound energy and

thermal energy.

How do wind turbines work?Wind turbines transform the kinetic energy of the wind into electrical energy.

The main steps are:

Step 1:  Moving air pushes against the blades of the turbine, making them rotate. In the

process, some of the kinetic energy of the moving air is transformed into the mechanical

(rotational kinetic) energy of the spinning blades. (The

wind still has some kinetic energy as it flows away from

the turbine.)

Step 2: The shafts and the gears inside the gear box

transfer the mechanical energy of the turbine to the

generator. (The gears make the drive shaft to the

generator spin faster than the shaft connected to the blade hub.)

What is the best place to locate a wind farm?Wind turbines should be located where there are steady strong winds - though not so

strong they would damage the turbines.

FIGURE 3. THE ENERGY TRANSFORMATIONS THAT TAKE PLACE IN A WIND TURBINE

They work at their greatest possible energy efficiency, however, when they operate in

‘smooth’ air - that is, when the air particles are moving in the same direction and not

2

whirling around and moving in different directions.

Ideal sites for wind turbines therefore are:

Away from obstructions such as forests, towers and rocky outcrops. (These

would cause the air to swirl around.)

At the highest point possible.

The best place is on top of a smooth hilltop, where

the wind can concentrate and increase in speed.

FIGURE 4. A CLOSE-UP VIEW OF A WIND

TURBINE AT THE WOOLNORTH WIND FARM    PHOTO

CREDIT: ROARING 40S.

The Power of the WindThe power available from the wind is proportional to the cube of the wind speed! This

means:

FIGURE 5. A WIND TURBINE – AN INSIDE VIEW

If the wind speed were 2 times greater, the power available from the wind would

be 8 times greater.

3

If the wind speed were 3 times greater, the power available from the wind would

be 27 times greater.

If the wind speed were 10 times greater, the power available from the wind would

be 1000 times greater!

This shows how important it is to locate wind farms in places where the winds are

strong.

What determines how much power is generated by a wind turbine?The amount of electrical power produced by a wind turbine doesn’t only depend on the

speed of the wind, and how smoothly it flows, however. It also depends on the way the

turbine is built:

The number of blades

The length of the blades

The shape of the blades

The mass (weight) of the blades

The pitch (angle) of the blades to the wind

The height of the tower

The gears used

The type of generator used

The computer system that controls the operation of the turbine and its power

output (where this is used)

What is the energy efficiency of wind turbines?Wind turbines do not produce electricity all the time. Although the wind might be

available for as much as 70 % of the time, it is often not strong enough to operate the

wind turbine at full efficiency. The combination of absence of wind and inadequate wind

4

strength means that even in a good location the wind turbine, over the course of a year,

will generate only about 30 % of the amount it could generate in a constant strong wind.

A good site might have 35 % efficiency. This means that the turbines will produce 35%

of their capacity on average over a year.

FIGURE 6. A SANKEY DIAGRAM SHOWING HOW SOME OF THE KINETIC ENERGY OF THE WIND IS TRANSFORMED

INTO FORMS OF ENERGY THAT ARE NOT USEFUL.

Apart from problems with the wind itself, some of the kinetic energy of the wind is

transformed into heat energy (the gears and shafts get hot) and sound energy (the

blades, gears and shafts make some noise as they spin). This is summarized in Figure

6.

Advantages of wind turbines

The main advantages of wind turbines, once they are built*, are:

They are a renewable energy resource.

They do not emit greenhouse gases or any other pollution.

They are more energy efficient than most power stations that burn fossil fuels.

They are less costly to run than many other energy resources.

5

They can be established in remote areas where other energy resources are not

practical, even in places like Antarctica and on ocean-going yachts.

FIGURE 7. A WIND TURBINE AT MAWSON BASE IN ANTARCTICA PHOTO CREDIT AUSTRALIAN ANTARCTIC DIVISION

*Greenhouse gases and other pollutants are produced during the manufacture,

transport and installation of wind turbines, but once they have operated for a year or so,

they will have compensated for this. Overall, wind turbines help reduce the amount of

greenhouse gases emitted into the atmosphere.

Disadvantages of wind turbines

Some of the disadvantages of wind turbines are:

The electrical power delivered varies because wind speed and direction vary.

Sometimes the wind speed is too low to even start rotation. Therefore they can

only be used to provide some of the electrical power people need.

They can be damaged by very strong winds and also corroded by salt in the air

when near the sea.

It can be costly to connect them to the electricity grid, due to the distances

involved.

6

Some people think they spoil the landscape.

They need to have flashing lights on the top to warn the pilots of any aircraft that

fly overhead of their presence. People who live close by sometimes complain the

flashing lights disturb their sleep.

In many countries, most wind turbines are constructed off-shore, usually because

people do not want them across the land. This is a much more expensive

location, because the turbines are more costly to install and to maintain, because

of problems such as corrosion of metal parts by sea water and damage from the

constant movement of waves and sand. This means the electricity they generate

is more expensive than that generated by coal-fired power stations.

There may be an impact on local bird populations.

Text Dependent Questions- RAVE your response on a separate piece of paper

1. Explain how a wind turbine works.

2. What are the factors that impact the placement of a wind turbine? Explain which

location is best.

3. Describe at least 3 advantages and disadvantages to wind turbines.

7