we can build plants to use it, water will be available as a source of energy. The energy of
waves and tides can also be used to produce water power.
Water power does have its problems, though. When a large dam is built, this creates a
reservoir, changing the ecosystem upstream. Large river ecosystems are inundated, killing
all the plants and animals. The dams and turbines also change the downstream environment
for fish and other living things. Dams also slow the release of silt, so that downstream deltas
retreat and seaside cities become dangerously exposed to storms and rising sea levels. Tidal
power stations may need to close off a narrow bay or estuary. Wave power applications have
to be able to withstand coastal storms and the corrosion of seawater.
Wind Power
Figure 5.10: Wind turbines like the ones shown above turn wind into electricity without
creating pollution. ( 3 )
As you learned earlier, the sun provides plenty of energy to the Earth. The energy from
the sun also creates wind (Figure5.10). Learning about what causes wind will help you
understand that energy can move as heat, not just by radiation and conduction, but also
by convection. Wind happens when the sun heats some parts of the Earth differently. For
example, sunlight hits the equator much more directly than it hits the North and South
Poles. Hot air rises and cooler air moves in, so when the air near the equator is heated much
more than the air near the poles, the air begins to move carrying heat through the air in a
process calledconvection. This movement of air is wind.
Wind power uses moving air as a source of energy. Some examples of wind power have
been around for a long time. Windmills have been used to grind grain and pump water