Visualizing Environmental Science

RRotor

diaameter

Rotor blade

Gear

box

Drive shaft

TTTower

Wind direction forr

an upwind rotor

Generatoro

0

1994 1996 1998

Year

2000 2002 2004 2006 2008 2010 2012

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

220

230

240

World wind energy–generating capacity (

×1000 megawatts)

From

Vital Signs 2005

, Worldwatch Institute, W.W. Norton (2005), and based on data from BTM Consult (2010),

American Wind Energy Association (2012), and European Wind Energy Association (2012).

Mark Thiessen/NG Image Collection

a. Kansas Wind Farm. Wind energy represents a promising alternative

that could diminish our dependence on fossil fuels.

c. Trends in Wind Energy Use. Global wind energy has shown

record growth in recent years.

b. Wind Turbine Design. This basic wind turbine

design has a horizontal axis (horizontal refers to

the orientation of the drive shaft). Airflow causes

the turbine’s blades to turn 15 to 60 revolutions

per minute (rpm). As the blades turn, gears within

the turbine spin the drive shaft. This spinning

powers the generator, which sends electricity

through underground cables to a nearby utility. (The

tower isn’t drawn to scale and is much taller than

depicted.)

Environmental InSight Wind energyÊ UÊ ˆ}ÕÀiÊ£n°™
✓✓THE PLANNER

Interpreting Data

What was the world wind energy–generating capacity in

1998? 2008? If the trend in this figure continues, what will

it be in 2018?

Indirect Solar Energy 453